text: /*
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version 2
   * of the License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
   *
   * The Original Code is Copyright (C) 2006 Blender Foundation.
   * All rights reserved.
   * Implementation of CustomData.
   *
   * BKE_customdata.h contains the function prototypes for this file.
   */
  
  /** \file
   * \ingroup bke
   */
  
  #include "MEM_guardedalloc.h"
  
  /* Since we have versioning code here (CustomData_verify_versions()). */
  #define DNA_DEPRECATED_ALLOW
  
  #include "DNA_ID.h"
  #include "DNA_customdata_types.h"
  #include "DNA_hair_types.h"
  #include "DNA_meshdata_types.h"
  
  #include "BLI_bitmap.h"
  #include "BLI_endian_switch.h"
  #include "BLI_math.h"
  #include "BLI_math_color_blend.h"
  #include "BLI_mempool.h"
  #include "BLI_path_util.h"
  #include "BLI_string.h"
  #include "BLI_string_utils.h"
  #include "BLI_utildefines.h"
  
  #include "BLT_translation.h"
  
  #include "BKE_customdata.h"
  #include "BKE_customdata_file.h"
  #include "BKE_deform.h"
  #include "BKE_main.h"
  #include "BKE_mesh_mapping.h"
  #include "BKE_mesh_remap.h"
  #include "BKE_multires.h"
  #include "BKE_subsurf.h"
  
  #include "BLO_read_write.h"
  
  #include "bmesh.h"
  
  #include "CLG_log.h"
  
  /* only for customdata_data_transfer_interp_normal_normals */
  #include "data_transfer_intern.h"
  
  /* number of layers to add when growing a CustomData object */
  #define CUSTOMDATA_GROW 5
  
  /* ensure typemap size is ok */
  BLI_STATIC_ASSERT(ARRAY_SIZE(((CustomData *)NULL)->typemap) == CD_NUMTYPES, "size mismatch");
  
  static CLG_LogRef LOG = {"bke.customdata"};
  
  /** Update mask_dst with layers defined in mask_src (equivalent to a bitwise OR). */
  void CustomData_MeshMasks_update(CustomData_MeshMasks *mask_dst,
                                   const CustomData_MeshMasks *mask_src)
  {
    mask_dst->vmask |= mask_src->vmask;
    mask_dst->emask |= mask_src->emask;
    mask_dst->fmask |= mask_src->fmask;
    mask_dst->pmask |= mask_src->pmask;
    mask_dst->lmask |= mask_src->lmask;
  }
  
  /** Return True if all layers set in \a mask_required are also set in \a mask_ref */
  bool CustomData_MeshMasks_are_matching(const CustomData_MeshMasks *mask_ref,
                                         const CustomData_MeshMasks *mask_required)
  {
    return (((mask_required->vmask & mask_ref->vmask) == mask_required->vmask) &&
            ((mask_required->emask & mask_ref->emask) == mask_required->emask) &&
            ((mask_required->fmask & mask_ref->fmask) == mask_required->fmask) &&
            ((mask_required->pmask & mask_ref->pmask) == mask_required->pmask) &&
            ((mask_required->lmask & mask_ref->lmask) == mask_required->lmask));
  }
  
  /********************* Layer type information **********************/
  typedef struct LayerTypeInfo {
    int size; /* the memory size of one element of this layer's data */
  
    /** name of the struct used, for file writing */
    const char *structname;
    /** number of structs per element, for file writing */
    int structnum;
  
    /**
     * default layer name.
     * note! when NULL this is a way to ensure there is only ever one item
     * see: CustomData_layertype_is_singleton() */
    const char *defaultname;
  
    /**
     * a function to copy count elements of this layer's data
     * (deep copy if appropriate)
     * if NULL, memcpy is used
     */
    cd_copy copy;
  
    /**
     * a function to free any dynamically allocated components of this
     * layer's data (note the data pointer itself should not be freed)
     * size should be the size of one element of this layer's data (e.g.
     * LayerTypeInfo.size)
     */
    void (*free)(void *data, int count, int size);
  
    /**
     * a function to interpolate between count source elements of this
     * layer's data and store the result in dest
     * if weights == NULL or sub_weights == NULL, they should default to 1
     *
     * weights gives the weight for each element in sources
     * sub_weights gives the sub-element weights for each element in sources
     *    (there should be (sub element count)^2 weights per element)
     * count gives the number of elements in sources
     *
     * \note in some cases \a dest pointer is in \a sources
     *       so all functions have to take this into account and delay
     *       applying changes while reading from sources.
     *       See bug T32395 - Campbell.
     */
    cd_interp interp;
  
    /** a function to swap the data in corners of the element */
    void (*swap)(void *data, const int *corner_indices);
  
    /**
     * a function to set a layer's data to default values. if NULL, the
     * default is assumed to be all zeros */
    void (*set_default)(void *data, int count);
  
    /** A function used by mesh validating code, must ensures passed item has valid data. */
    cd_validate validate;
  
    /** functions necessary for geometry collapse */
    bool (*equal)(const void *data1, const void *data2);
    void (*multiply)(void *data, float fac);
    void (*initminmax)(void *min, void *max);
    void (*add)(void *data1, const void *data2);
    void (*dominmax)(const void *data1, void *min, void *max);
    void (*copyvalue)(const void *source, void *dest, const int mixmode, const float mixfactor);
  
    /** a function to read data from a cdf file */
    bool (*read)(CDataFile *cdf, void *data, int count);
  
    /** a function to write data to a cdf file */
    bool (*write)(CDataFile *cdf, const void *data, int count);
  
    /** a function to determine file size */
    size_t (*filesize)(CDataFile *cdf, const void *data, int count);
  
    /** a function to determine max allowed number of layers,
     * should be NULL or return -1 if no limit */
    int (*layers_max)(void);
  } LayerTypeInfo;
  
  static void layerCopy_mdeformvert(const void *source, void *dest, int count)
  {
    int i, size = sizeof(MDeformVert);
  
    memcpy(dest, source, count * size);
  
    for (i = 0; i < count; i++) {
      MDeformVert *dvert = POINTER_OFFSET(dest, i * size);
  
      if (dvert->totweight) {
        MDeformWeight *dw = MEM_malloc_arrayN(
            dvert->totweight, sizeof(*dw), "layerCopy_mdeformvert dw");
  
        memcpy(dw, dvert->dw, dvert->totweight * sizeof(*dw));
        dvert->dw = dw;
      }
      else {
        dvert->dw = NULL;
      }
    }
  }
  
  static void layerFree_mdeformvert(void *data, int count, int size)
  {
    for (int i = 0; i < count; i++) {
      MDeformVert *dvert = POINTER_OFFSET(data, i * size);
  
      if (dvert->dw) {
        MEM_freeN(dvert->dw);
        dvert->dw = NULL;
        dvert->totweight = 0;
      }
    }
  }
  
  /* copy just zeros in this case */
  static void layerCopy_bmesh_elem_py_ptr(const void *UNUSED(source), void *dest, int count)
  {
    int i, size = sizeof(void *);
  
    for (i = 0; i < count; i++) {
      void **ptr = POINTER_OFFSET(dest, i * size);
      *ptr = NULL;
    }
  }
  
  #ifndef WITH_PYTHON
  void bpy_bm_generic_invalidate(struct BPy_BMGeneric *UNUSED(self))
  {
    /* dummy */
  }
  #endif
  
  static void layerFree_bmesh_elem_py_ptr(void *data, int count, int size)
  {
    for (int i = 0; i < count; i++) {
      void **ptr = POINTER_OFFSET(data, i * size);
      if (*ptr) {
        bpy_bm_generic_invalidate(*ptr);
      }
    }
  }
  
  static void layerInterp_mdeformvert(const void **sources,
                                      const float *weights,
                                      const float *UNUSED(sub_weights),
                                      int count,
                                      void *dest)
  {
    /* a single linked list of MDeformWeight's
     * use this to avoid double allocs (which LinkNode would do) */
    struct MDeformWeight_Link {
      struct MDeformWeight_Link *next;
      MDeformWeight dw;
    };
  
    MDeformVert *dvert = dest;
    struct MDeformWeight_Link *dest_dwlink = NULL;
    struct MDeformWeight_Link *node;
    int i, j, totweight;
  
    /* build a list of unique def_nrs for dest */
    totweight = 0;
    for (i = 0; i < count; i++) {
      const MDeformVert *source = sources[i];
      float interp_weight = weights[i];
  
      for (j = 0; j < source->totweight; j++) {
        MDeformWeight *dw = &source->dw[j];
        float weight = dw->weight * interp_weight;
  
        if (weight == 0.0f) {
          continue;
        }
  
        for (node = dest_dwlink; node; node = node->next) {
          MDeformWeight *tmp_dw = &node->dw;
  
          if (tmp_dw->def_nr == dw->def_nr) {
            tmp_dw->weight += weight;
            break;
          }
        }
  
        /* if this def_nr is not in the list, add it */
        if (!node) {
          struct MDeformWeight_Link *tmp_dwlink = alloca(sizeof(*tmp_dwlink));
          tmp_dwlink->dw.def_nr = dw->def_nr;
          tmp_dwlink->dw.weight = weight;
  
          /* inline linklist */
          tmp_dwlink->next = dest_dwlink;
          dest_dwlink = tmp_dwlink;
  
          totweight++;
        }
      }
    }
  
    /* Delay writing to the destination in case dest is in sources. */
  
    /* now we know how many unique deform weights there are, so realloc */
    if (dvert->dw && (dvert->totweight == totweight)) {
      /* pass (fast-path if we don't need to realloc). */
    }
    else {
      if (dvert->dw) {
        MEM_freeN(dvert->dw);
      }
  
      if (totweight) {
        dvert->dw = MEM_malloc_arrayN(totweight, sizeof(*dvert->dw), __func__);
      }
    }
  
    if (totweight) {
      dvert->totweight = totweight;
      for (i = 0, node = dest_dwlink; node; node = node->next, i++) {
        if (node->dw.weight > 1.0f) {
          node->dw.weight = 1.0f;
        }
        dvert->dw[i] = node->dw;
      }
    }
    else {
      memset(dvert, 0, sizeof(*dvert));
    }
  }
  
  static void layerInterp_normal(const void **sources,
                                 const float *weights,
                                 const float *UNUSED(sub_weights),
                                 int count,
                                 void *dest)
  {
    /* Note: This is linear interpolation, which is not optimal for vectors.
     * Unfortunately, spherical interpolation of more than two values is hairy,
     * so for now it will do... */
    float no[3] = {0.0f};
  
    while (count--) {
      madd_v3_v3fl(no, (const float *)sources[count], weights[count]);
    }
  
    /* Weighted sum of normalized vectors will **not** be normalized, even if weights are. */
    normalize_v3_v3((float *)dest, no);
  }
  
  static bool layerValidate_normal(void *data, const uint totitems, const bool do_fixes)
  {
    static const float no_default[3] = {0.0f, 0.0f, 1.0f}; /* Z-up default normal... */
    float(*no)[3] = data;
    bool has_errors = false;
  
    for (int i = 0; i < totitems; i++, no++) {
      if (!is_finite_v3((float *)no)) {
        has_errors = true;
        if (do_fixes) {
          copy_v3_v3((float *)no, no_default);
        }
      }
      else if (!compare_ff(len_squared_v3((float *)no), 1.0f, 1e-6f)) {
        has_errors = true;
        if (do_fixes) {
          normalize_v3((float *)no);
        }
      }
    }
  
    return has_errors;
  }
  
  static void layerCopyValue_normal(const void *source,
                                    void *dest,
                                    const int mixmode,
                                    const float mixfactor)
  {
    const float *no_src = source;
    float *no_dst = dest;
    float no_tmp[3];
  
    if (ELEM(mixmode,
             CDT_MIX_NOMIX,
             CDT_MIX_REPLACE_ABOVE_THRESHOLD,
             CDT_MIX_REPLACE_BELOW_THRESHOLD)) {
      /* Above/below threshold modes are not supported here, fallback to nomix (just in case). */
      copy_v3_v3(no_dst, no_src);
    }
    else { /* Modes that support 'real' mix factor. */
      /* Since we normalize in the end, MIX and ADD are the same op here. */
      if (ELEM(mixmode, CDT_MIX_MIX, CDT_MIX_ADD)) {
        add_v3_v3v3(no_tmp, no_dst, no_src);
        normalize_v3(no_tmp);
      }
      else if (mixmode == CDT_MIX_SUB) {
        sub_v3_v3v3(no_tmp, no_dst, no_src);
        normalize_v3(no_tmp);
      }
      else if (mixmode == CDT_MIX_MUL) {
        mul_v3_v3v3(no_tmp, no_dst, no_src);
        normalize_v3(no_tmp);
      }
      else {
        copy_v3_v3(no_tmp, no_src);
      }
      interp_v3_v3v3_slerp_safe(no_dst, no_dst, no_tmp, mixfactor);
    }
  }
  
  static void layerCopy_tface(const void *source, void *dest, int count)
  {
    const MTFace *source_tf = (const MTFace *)source;
    MTFace *dest_tf = (MTFace *)dest;
    for (int i = 0; i < count; i++) {
      dest_tf[i] = source_tf[i];
    }
  }
  
  static void layerInterp_tface(
      const void **sources, const float *weights, const float *sub_weights, int count, void *dest)
  {
    MTFace *tf = dest;
    int i, j, k;
    float uv[4][2] = {{0.0f}};
    const float *sub_weight;
  
    sub_weight = sub_weights;
    for (i = 0; i < count; i++) {
      const float interp_weight = weights[i];
      const MTFace *src = sources[i];
  
      for (j = 0; j < 4; j++) {
        if (sub_weights) {
          for (k = 0; k < 4; k++, sub_weight++) {
            madd_v2_v2fl(uv[j], src->uv[k], (*sub_weight) * interp_weight);
          }
        }
        else {
          madd_v2_v2fl(uv[j], src->uv[j], interp_weight);
        }
      }
    }
  
    /* Delay writing to the destination in case dest is in sources. */
    *tf = *(MTFace *)(*sources);
    memcpy(tf->uv, uv, sizeof(tf->uv));
  }
  
  static void layerSwap_tface(void *data, const int *corner_indices)
  {
    MTFace *tf = data;
    float uv[4][2];
    int j;
  
    for (j = 0; j < 4; j++) {
      const int source_index = corner_indices[j];
      copy_v2_v2(uv[j], tf->uv[source_index]);
    }
  
    memcpy(tf->uv, uv, sizeof(tf->uv));
  }
  
  static void layerDefault_tface(void *data, int count)
  {
    static MTFace default_tf = {{{0, 0}, {1, 0}, {1, 1}, {0, 1}}};
    MTFace *tf = (MTFace *)data;
  
    for (int i = 0; i < count; i++) {
      tf[i] = default_tf;
    }
  }
  
  static int layerMaxNum_tface(void)
  {
    return MAX_MTFACE;
  }
  
  static void layerCopy_propFloat(const void *source, void *dest, int count)
  {
    memcpy(dest, source, sizeof(MFloatProperty) * count);
  }
  
  static bool layerValidate_propFloat(void *data, const uint totitems, const bool do_fixes)
  {
    MFloatProperty *fp = data;
    bool has_errors = false;
  
    for (int i = 0; i < totitems; i++, fp++) {
      if (!isfinite(fp->f)) {
        if (do_fixes) {
          fp->f = 0.0f;
        }
        has_errors = true;
      }
    }
  
    return has_errors;
  }
  
  static void layerCopy_propInt(const void *source, void *dest, int count)
  {
    memcpy(dest, source, sizeof(MIntProperty) * count);
  }
  
  static void layerCopy_propString(const void *source, void *dest, int count)
  {
    memcpy(dest, source, sizeof(MStringProperty) * count);
  }
  
  static void layerCopy_origspace_face(const void *source, void *dest, int count)
  {
    const OrigSpaceFace *source_tf = (const OrigSpaceFace *)source;
    OrigSpaceFace *dest_tf = (OrigSpaceFace *)dest;
  
    for (int i = 0; i < count; i++) {
      dest_tf[i] = source_tf[i];
    }
  }
  
  static void layerInterp_origspace_face(
      const void **sources, const float *weights, const float *sub_weights, int count, void *dest)
  {
    OrigSpaceFace *osf = dest;
    int i, j, k;
    float uv[4][2] = {{0.0f}};
    const float *sub_weight;
  
    sub_weight = sub_weights;
    for (i = 0; i < count; i++) {
      const float interp_weight = weights[i];
      const OrigSpaceFace *src = sources[i];
  
      for (j = 0; j < 4; j++) {
        if (sub_weights) {
          for (k = 0; k < 4; k++, sub_weight++) {
            madd_v2_v2fl(uv[j], src->uv[k], (*sub_weight) * interp_weight);
          }
        }
        else {
          madd_v2_v2fl(uv[j], src->uv[j], interp_weight);
        }
      }
    }
  
    /* Delay writing to the destination in case dest is in sources. */
    memcpy(osf->uv, uv, sizeof(osf->uv));
  }
  
  static void layerSwap_origspace_face(void *data, const int *corner_indices)
  {
    OrigSpaceFace *osf = data;
    float uv[4][2];
    int j;
  
    for (j = 0; j < 4; j++) {
      copy_v2_v2(uv[j], osf->uv[corner_indices[j]]);
    }
    memcpy(osf->uv, uv, sizeof(osf->uv));
  }
  
  static void layerDefault_origspace_face(void *data, int count)
  {
    static OrigSpaceFace default_osf = {{{0, 0}, {1, 0}, {1, 1}, {0, 1}}};
    OrigSpaceFace *osf = (OrigSpaceFace *)data;
  
    for (int i = 0; i < count; i++) {
      osf[i] = default_osf;
    }
  }
  
  static void layerSwap_mdisps(void *data, const int *ci)
  {
    MDisps *s = data;
    float(*d)[3] = NULL;
    int corners, cornersize, S;
  
    if (s->disps) {
      int nverts = (ci[1] == 3) ? 4 : 3; /* silly way to know vertex count of face */
      corners = multires_mdisp_corners(s);
      cornersize = s->totdisp / corners;
  
      if (corners != nverts) {
        /* happens when face changed vertex count in edit mode
         * if it happened, just forgot displacement */
  
        MEM_freeN(s->disps);
        s->totdisp = (s->totdisp / corners) * nverts;
        s->disps = MEM_calloc_arrayN(s->totdisp, sizeof(float[3]), "mdisp swap");
        return;
      }
  
      d = MEM_calloc_arrayN(s->totdisp, sizeof(float[3]), "mdisps swap");
  
      for (S = 0; S < corners; S++) {
        memcpy(d + cornersize * S, s->disps + cornersize * ci[S], sizeof(float[3]) * cornersize);
      }
  
      MEM_freeN(s->disps);
      s->disps = d;
    }
  }
  
  static void layerCopy_mdisps(const void *source, void *dest, int count)
  {
    const MDisps *s = source;
    MDisps *d = dest;
  
    for (int i = 0; i < count; i++) {
      if (s[i].disps) {
        d[i].disps = MEM_dupallocN(s[i].disps);
        d[i].hidden = MEM_dupallocN(s[i].hidden);
      }
      else {
        d[i].disps = NULL;
        d[i].hidden = NULL;
      }
  
      /* still copy even if not in memory, displacement can be external */
      d[i].totdisp = s[i].totdisp;
      d[i].level = s[i].level;
    }
  }
  
  static void layerFree_mdisps(void *data, int count, int UNUSED(size))
  {
    MDisps *d = data;
  
    for (int i = 0; i < count; i++) {
      if (d[i].disps) {
        MEM_freeN(d[i].disps);
      }
      if (d[i].hidden) {
        MEM_freeN(d[i].hidden);
      }
      d[i].disps = NULL;
      d[i].hidden = NULL;
      d[i].totdisp = 0;
      d[i].level = 0;
    }
  }
  
  static bool layerRead_mdisps(CDataFile *cdf, void *data, int count)
  {
    MDisps *d = data;
  
    for (int i = 0; i < count; i++) {
      if (!d[i].disps) {
        d[i].disps = MEM_calloc_arrayN(d[i].totdisp, sizeof(float[3]), "mdisps read");
      }
  
      if (!cdf_read_data(cdf, sizeof(float[3]) * d[i].totdisp, d[i].disps)) {
        CLOG_ERROR(&LOG, "failed to read multires displacement %d/%d %d", i, count, d[i].totdisp);
        return 0;
      }
    }
  
    return true;
  }
  
  static bool layerWrite_mdisps(CDataFile *cdf, const void *data, int count)
  {
    const MDisps *d = data;
  
    for (int i = 0; i < count; i++) {
      if (!cdf_write_data(cdf, sizeof(float[3]) * d[i].totdisp, d[i].disps)) {
        CLOG_ERROR(&LOG, "failed to write multires displacement %d/%d %d", i, count, d[i].totdisp);
        return 0;
      }
    }
  
    return true;
  }
  
  static size_t layerFilesize_mdisps(CDataFile *UNUSED(cdf), const void *data, int count)
  {
    const MDisps *d = data;
    size_t size = 0;
  
    for (int i = 0; i < count; i++) {
      size += sizeof(float[3]) * d[i].totdisp;
    }
  
    return size;
  }
  static void layerInterp_paint_mask(const void **sources,
                                     const float *weights,
                                     const float *UNUSED(sub_weights),
                                     int count,
                                     void *dest)
  {
    float mask = 0.0f;
    for (int i = 0; i < count; i++) {
      const float interp_weight = weights[i];
      const float *src = sources[i];
      mask += (*src) * interp_weight;
    }
    *(float *)dest = mask;
  }
  
  static void layerCopy_grid_paint_mask(const void *source, void *dest, int count)
  {
    const GridPaintMask *s = source;
    GridPaintMask *d = dest;
  
    for (int i = 0; i < count; i++) {
      if (s[i].data) {
        d[i].data = MEM_dupallocN(s[i].data);
        d[i].level = s[i].level;
      }
      else {
        d[i].data = NULL;
        d[i].level = 0;
      }
    }
  }
  
  static void layerFree_grid_paint_mask(void *data, int count, int UNUSED(size))
  {
    GridPaintMask *gpm = data;
  
    for (int i = 0; i < count; i++) {
      if (gpm[i].data) {
        MEM_freeN(gpm[i].data);
      }
      gpm[i].data = NULL;
      gpm[i].level = 0;
    }
  }
  
  /* --------- */
  static void layerCopyValue_mloopcol(const void *source,
                                      void *dest,
                                      const int mixmode,
                                      const float mixfactor)
  {
    const MLoopCol *m1 = source;
    MLoopCol *m2 = dest;
    unsigned char tmp_col[4];
  
    if (ELEM(mixmode,
             CDT_MIX_NOMIX,
             CDT_MIX_REPLACE_ABOVE_THRESHOLD,
             CDT_MIX_REPLACE_BELOW_THRESHOLD)) {
      /* Modes that do a full copy or nothing. */
      if (ELEM(mixmode, CDT_MIX_REPLACE_ABOVE_THRESHOLD, CDT_MIX_REPLACE_BELOW_THRESHOLD)) {
        /* TODO: Check for a real valid way to get 'factor' value of our dest color? */
        const float f = ((float)m2->r + (float)m2->g + (float)m2->b) / 3.0f;
        if (mixmode == CDT_MIX_REPLACE_ABOVE_THRESHOLD && f < mixfactor) {
          return; /* Do Nothing! */
        }
        if (mixmode == CDT_MIX_REPLACE_BELOW_THRESHOLD && f > mixfactor) {
          return; /* Do Nothing! */
        }
      }
      m2->r = m1->r;
      m2->g = m1->g;
      m2->b = m1->b;
      m2->a = m1->a;
    }
    else { /* Modes that support 'real' mix factor. */
      unsigned char src[4] = {m1->r, m1->g, m1->b, m1->a};
      unsigned char dst[4] = {m2->r, m2->g, m2->b, m2->a};
  
      if (mixmode == CDT_MIX_MIX) {
        blend_color_mix_byte(tmp_col, dst, src);
      }
      else if (mixmode == CDT_MIX_ADD) {
        blend_color_add_byte(tmp_col, dst, src);
      }
      else if (mixmode == CDT_MIX_SUB) {
        blend_color_sub_byte(tmp_col, dst, src);
      }
      else if (mixmode == CDT_MIX_MUL) {
        blend_color_mul_byte(tmp_col, dst, src);
      }
      else {
        memcpy(tmp_col, src, sizeof(tmp_col));
      }
  
      blend_color_interpolate_byte(dst, dst, tmp_col, mixfactor);
  
      m2->r = (char)dst[0];
      m2->g = (char)dst[1];
      m2->b = (char)dst[2];
      m2->a = (char)dst[3];
    }
  }
  
  static bool layerEqual_mloopcol(const void *data1, const void *data2)
  {
    const MLoopCol *m1 = data1, *m2 = data2;
    float r, g, b, a;
  
    r = m1->r - m2->r;
    g = m1->g - m2->g;
    b = m1->b - m2->b;
    a = m1->a - m2->a;
  
    return r * r + g * g + b * b + a * a < 0.001f;
  }
  
  static void layerMultiply_mloopcol(void *data, float fac)
  {
    MLoopCol *m = data;
  
    m->r = (float)m->r * fac;
    m->g = (float)m->g * fac;
    m->b = (float)m->b * fac;
    m->a = (float)m->a * fac;
  }
  
  static void layerAdd_mloopcol(void *data1, const void *data2)
  {
    MLoopCol *m = data1;
    const MLoopCol *m2 = data2;
  
    m->r += m2->r;
    m->g += m2->g;
    m->b += m2->b;
    m->a += m2->a;
  }
  
  static void layerDoMinMax_mloopcol(const void *data, void *vmin, void *vmax)
  {
    const MLoopCol *m = data;
    MLoopCol *min = vmin, *max = vmax;
  
    if (m->r < min->r) {
      min->r = m->r;
    }
    if (m->g < min->g) {
      min->g = m->g;
    }
    if (m->b < min->b) {
      min->b = m->b;
    }
    if (m->a < min->a) {
      min->a = m->a;
    }
    if (m->r > max->r) {
      max->r = m->r;
    }
    if (m->g > max->g) {
      max->g = m->g;
    }
    if (m->b > max->b) {
      max->b = m->b;
    }
    if (m->a > max->a) {
      max->a = m->a;
    }
  }
  
  static void layerInitMinMax_mloopcol(void *vmin, void *vmax)
  {
    MLoopCol *min = vmin, *max = vmax;
  
    min->r = 255;
    min->g = 255;
    min->b = 255;
    min->a = 255;
  
    max->r = 0;
    max->g = 0;
    max->b = 0;
    max->a = 0;
  }
  
  static void layerDefault_mloopcol(void *data, int count)
  {
    MLoopCol default_mloopcol = {255, 255, 255, 255};
    MLoopCol *mlcol = (MLoopCol *)data;
    for (int i = 0; i < count; i++) {
      mlcol[i] = default_mloopcol;
    }
  }
  
  static void layerInterp_mloopcol(const void **sources,
                                   const float *weights,
                                   const float *UNUSED(sub_weights),
                                   int count,
                                   void *dest)
  {
    MLoopCol *mc = dest;
    struct {
      float a;
      float r;
      float g;
      float b;
    } col = {0};
  
    for (int i = 0; i < count; i++) {
      const float interp_weight = weights[i];
      const MLoopCol *src = sources[i];
      col.r += src->r * interp_weight;
      col.g += src->g * interp_weight;
      col.b += src->b * interp_weight;
      col.a += src->a * interp_weight;
    }
  
    /* Subdivide smooth or fractal can cause problems without clamping
     * although weights should also not cause this situation */
  
    /* Also delay writing to the destination in case dest is in sources. */
    mc->r = round_fl_to_uchar_clamp(col.r);
    mc->g = round_fl_to_uchar_clamp(col.g);
    mc->b = round_fl_to_uchar_clamp(col.b);
    mc->a = round_fl_to_uchar_clamp(col.a);
  }
  
  static int layerMaxNum_mloopcol(void)
  {
    return MAX_MCOL;
  }
  
  static void layerCopyValue_mloopuv(const void *source,
                                     void *dest,
                                     const int mixmode,
                                     const float mixfactor)
  {
    const MLoopUV *luv1 = source;
    MLoopUV *luv2 = dest;
  
    /* We only support a limited subset of advanced mixing here -
     * namely the mixfactor interpolation. */
  
    if (mixmode == CDT_MIX_NOMIX) {
      copy_v2_v2(luv2->uv, luv1->uv);
    }
    else {
      interp_v2_v2v2(luv2->uv, luv2->uv, luv1->uv, mixfactor);
    }
  }
  
  static bool layerEqual_mloopuv(const void *data1, const void *data2)
  {
    const MLoopUV *luv1 = data1, *luv2 = data2;
  
    return len_squared_v2v2(luv1->uv, luv2->uv) < 0.00001f;
  }
  
  static void layerMultiply_mloopuv(void *data, float fac)
  {
    MLoopUV *luv = data;
  
    mul_v2_fl(luv->uv, fac);
  }
  
  static void layerInitMinMax_mloopuv(void *vmin, void *vmax)
  {
    MLoopUV *min = vmin, *max = vmax;
  
    INIT_MINMAX2(min->uv, max->uv);
  }
  
  static void layerDoMinMax_mloopuv(const void *data, void *vmin, void *vmax)
  {
    const MLoopUV *luv = data;
    MLoopUV *min = vmin, *max = vmax;
  
    minmax_v2v2_v2(min->uv, max->uv, luv->uv);
  }
  
  static void layerAdd_mloopuv(void *data1, const void *data2)
  {
    MLoopUV *l1 = data1;
    const MLoopUV *l2 = data2;
  
    add_v2_v2(l1->uv, l2->uv);
  }
  
  static void layerInterp_mloopuv(const void **sources,
                                  const float *weights,
                                  const float *UNUSED(sub_weights),
                                  int count,
                                  void *dest)
  {
    float uv[2];
    int flag = 0;
  
    zero_v2(uv);
  
    for (int i = 0; i < count; i++) {
      const float interp_weight = weights[i];
      const MLoopUV *src = sources[i];
      madd_v2_v2fl(uv, src->uv, interp_weight);
      if (interp_weight > 0.0f) {
        flag |= src->flag;
      }
    }
  
    /* Delay writing to the destination in case dest is in sources. */
    copy_v2_v2(((MLoopUV *)dest)->uv, uv);
    ((MLoopUV *)dest)->flag = flag;
  }
  
  static bool layerValidate_mloopuv(void *data, const uint totitems, const bool do_fixes)
  {
    MLoopUV *uv = data;
    bool has_errors = false;
  
    for (int i = 0; i < totitems; i++, uv++) {
      if (!is_finite_v2(uv->uv)) {
        if (do_fixes) {
          zero_v2(uv->uv);
        }
        has_errors = true;
      }
    }
  
    return has_errors;
  }
  
  /* origspace is almost exact copy of mloopuv's, keep in sync */
  static void layerCopyValue_mloop_origspace(const void *source,
                                             void *dest,
                                             const int UNUSED(mixmode),
                                             const float UNUSED(mixfactor))
  {
    const OrigSpaceLoop *luv1 = source;
    OrigSpaceLoop *luv2 = dest;
  
    copy_v2_v2(luv2->uv, luv1->uv);
  }
  
  static bool layerEqual_mloop_origspace(const void *data1, const void *data2)
  {
    const OrigSpaceLoop *luv1 = data1, *luv2 = data2;
  
    return len_squared_v2v2(luv1->uv, luv2->uv) < 0.00001f;
  }
  
  static void layerMultiply_mloop_origspace(void *data, float fac)
  {
    OrigSpaceLoop *luv = data;
  
    mul_v2_fl(luv->uv, fac);
  }
  
  static void layerInitMinMax_mloop_origspace(void *vmin, void *vmax)
  {
    OrigSpaceLoop *min = vmin, *max = vmax;
  
    INIT_MINMAX2(min->uv, max->uv);
  }
  
  static void layerDoMinMax_mloop_origspace(const void *data, void *vmin, void *vmax)
  {
    const OrigSpaceLoop *luv = data;
    OrigSpaceLoop *min = vmin, *max = vmax;
  
    minmax_v2v2_v2(min->uv, max->uv, luv->uv);
  }
  
  static void layerAdd_mloop_origspace(void *data1, const void *data2)
  {
    OrigSpaceLoop *l1 = data1;
    const OrigSpaceLoop *l2 = data2;
  
    add_v2_v2(l1->uv, l2->uv);
  }
  
  static void layerInterp_mloop_origspace(const void **sources,
                                          const float *weights,
                                          const float *UNUSED(sub_weights),
                                          int count,
                                          void *dest)
  {
    float uv[2];
    zero_v2(uv);
  
    for (int i = 0; i < count; i++) {
      const float interp_weight = weights[i];
      const OrigSpaceLoop *src = sources[i];
      madd_v2_v2fl(uv, src->uv, interp_weight);
    }
  
    /* Delay writing to the destination in case dest is in sources. */
    copy_v2_v2(((OrigSpaceLoop *)dest)->uv, uv);
  }
  /* --- end copy */
  
  static void layerInterp_mcol(
      const void **sources, const float *weights, const float *sub_weights, int count, void *dest)
  {
    MCol *mc = dest;
    struct {
      float a;
      float r;
      float g;
      float b;
    } col[4] = {{0.0f}};
  
    const float *sub_weight = sub_weights;
    for (int i = 0; i < count; i++) {
      const float interp_weight = weights[i];
  
      for (int j = 0; j < 4; j++) {
        if (sub_weights) {
          const MCol *src = sources[i];
          for (int k = 0; k < 4; k++, sub_weight++, src++) {
            const float w = (*sub_weight) * interp_weight;
            col[j].a += src->a * w;
            col[j].r += src->r * w;
            col[j].g += src->g * w;
            col[j].b += src->b * w;
          }
        }
        else {
          const MCol *src = sources[i];
          col[j].a += src[j].a * interp_weight;
          col[j].r += src[j].r * interp_weight;
          col[j].g += src[j].g * interp_weight;
          col[j].b += src[j].b * interp_weight;
        }
      }
    }
  
    /* Delay writing to the destination in case dest is in sources. */
    for (int j = 0; j < 4; j++) {
  
      /* Subdivide smooth or fractal can cause problems without clamping
       * although weights should also not cause this situation */
      mc[j].a = round_fl_to_uchar_clamp(col[j].a);
      mc[j].r = round_fl_to_uchar_clamp(col[j].r);
      mc[j].g = round_fl_to_uchar_clamp(col[j].g);
      mc[j].b = round_fl_to_uchar_clamp(col[j].b);
    }
  }
  
  static void layerSwap_mcol(void *data, const int *corner_indices)
  {
    MCol *mcol = data;
    MCol col[4];
    int j;
  
    for (j = 0; j < 4; j++) {
      col[j] = mcol[corner_indices[j]];
    }
  
    memcpy(mcol, col, sizeof(col));
  }
  
  static void layerDefault_mcol(void *data, int count)
  {
    static MCol default_mcol = {255, 255, 255, 255};
    MCol *mcol = (MCol *)data;
  
    for (int i = 0; i < 4 * count; i++) {
      mcol[i] = default_mcol;
    }
  }
  
  static void layerDefault_origindex(void *data, int count)
  {
    copy_vn_i((int *)data, count, ORIGINDEX_NONE);
  }
  
  static void layerInterp_bweight(const void **sources,
                                  const float *weights,
                                  const float *UNUSED(sub_weights),
                                  int count,
                                  void *dest)
  {
    float **in = (float **)sources;
  
    if (count <= 0) {
      return;
    }
  
    float f = 0.0f;
  
    for (int i = 0; i < count; i++) {
      const float interp_weight = weights[i];
      f += *in[i] * interp_weight;
    }
  
    /* Delay writing to the destination in case dest is in sources. */
    *((float *)dest) = f;
  }
  
  static void layerInterp_shapekey(const void **sources,
                                   const float *weights,
                                   const float *UNUSED(sub_weights),
                                   int count,
                                   void *dest)
  {
    float **in = (float **)sources;
  
    if (count <= 0) {
      return;
    }
  
    float co[3];
    zero_v3(co);
  
    for (int i = 0; i < count; i++) {
      const float interp_weight = weights[i];
      madd_v3_v3fl(co, in[i], interp_weight);
    }
  
    /* Delay writing to the destination in case dest is in sources. */
    copy_v3_v3((float *)dest, co);
  }
  
  static void layerDefault_mvert_skin(void *data, int count)
  {
    MVertSkin *vs = data;
  
    for (int i = 0; i < count; i++) {
      copy_v3_fl(vs[i].radius, 0.25f);
      vs[i].flag = 0;
    }
  }
  
  static void layerCopy_mvert_skin(const void *source, void *dest, int count)
  {
    memcpy(dest, source, sizeof(MVertSkin) * count);
  }
  
  static void layerInterp_mvert_skin(const void **sources,
                                     const float *weights,
                                     const float *UNUSED(sub_weights),
                                     int count,
                                     void *dest)
  {
    MVertSkin *vs_dst = dest;
  
    float radius[3];
    zero_v3(radius);
  
    for (int i = 0; i < count; i++) {
      const float interp_weight = weights[i];
      const MVertSkin *vs_src = sources[i];
  
      madd_v3_v3fl(radius, vs_src->radius, interp_weight);
    }
  
    /* Delay writing to the destination in case dest is in sources. */
    vs_dst = dest;
    copy_v3_v3(vs_dst->radius, radius);
    vs_dst->flag &= ~MVERT_SKIN_ROOT;
  }
  
  static void layerSwap_flnor(void *data, const int *corner_indices)
  {
    short(*flnors)[4][3] = data;
    short nors[4][3];
    int i = 4;
  
    while (i--) {
      copy_v3_v3_short(nors[i], (*flnors)[corner_indices[i]]);
    }
  
    memcpy(flnors, nors, sizeof(nors));
  }
  
  static void layerDefault_fmap(void *data, int count)
  {
    int *fmap_num = (int *)data;
    for (int i = 0; i < count; i++) {
      fmap_num[i] = -1;
    }
  }
  
  static void layerCopyValue_propcol(const void *source,
                                     void *dest,
                                     const int mixmode,
                                     const float mixfactor)
  {
    const MPropCol *m1 = source;
    MPropCol *m2 = dest;
    float tmp_col[4];
  
    if (ELEM(mixmode,
             CDT_MIX_NOMIX,
             CDT_MIX_REPLACE_ABOVE_THRESHOLD,
             CDT_MIX_REPLACE_BELOW_THRESHOLD)) {
      /* Modes that do a full copy or nothing. */
      if (ELEM(mixmode, CDT_MIX_REPLACE_ABOVE_THRESHOLD, CDT_MIX_REPLACE_BELOW_THRESHOLD)) {
        /* TODO: Check for a real valid way to get 'factor' value of our dest color? */
        const float f = (m2->color[0] + m2->color[1] + m2->color[2]) / 3.0f;
        if (mixmode == CDT_MIX_REPLACE_ABOVE_THRESHOLD && f < mixfactor) {
          return; /* Do Nothing! */
        }
        if (mixmode == CDT_MIX_REPLACE_BELOW_THRESHOLD && f > mixfactor) {
          return; /* Do Nothing! */
        }
      }
      copy_v4_v4(m2->color, m1->color);
    }
    else { /* Modes that support 'real' mix factor. */
      if (mixmode == CDT_MIX_MIX) {
        blend_color_mix_float(tmp_col, m2->color, m1->color);
      }
      else if (mixmode == CDT_MIX_ADD) {
        blend_color_add_float(tmp_col, m2->color, m1->color);
      }
      else if (mixmode == CDT_MIX_SUB) {
        blend_color_sub_float(tmp_col, m2->color, m1->color);
      }
      else if (mixmode == CDT_MIX_MUL) {
        blend_color_mul_float(tmp_col, m2->color, m1->color);
      }
      else {
        memcpy(tmp_col, m1->color, sizeof(tmp_col));
      }
      blend_color_interpolate_float(m2->color, m2->color, tmp_col, mixfactor);
  
      copy_v4_v4(m2->color, m1->color);
    }
  }
  
  static bool layerEqual_propcol(const void *data1, const void *data2)
  {
    const MPropCol *m1 = data1, *m2 = data2;
    float tot = 0;
  
    for (int i = 0; i < 4; i++) {
      float c = (m1->color[i] - m2->color[i]);
      tot += c * c;
    }
  
    return tot < 0.001f;
  }
  
  static void layerMultiply_propcol(void *data, float fac)
  {
    MPropCol *m = data;
    mul_v4_fl(m->color, fac);
  }
  
  static void layerAdd_propcol(void *data1, const void *data2)
  {
    MPropCol *m = data1;
    const MPropCol *m2 = data2;
    add_v4_v4(m->color, m2->color);
  }
  
  static void layerDoMinMax_propcol(const void *data, void *vmin, void *vmax)
  {
    const MPropCol *m = data;
    MPropCol *min = vmin, *max = vmax;
    minmax_v4v4_v4(min->color, max->color, m->color);
  }
  
  static void layerInitMinMax_propcol(void *vmin, void *vmax)
  {
    MPropCol *min = vmin, *max = vmax;
  
    copy_v4_fl(min->color, FLT_MAX);
    copy_v4_fl(max->color, FLT_MIN);
  }
  
  static void layerDefault_propcol(void *data, int count)
  {
    /* Default to white, full alpha. */
    MPropCol default_propcol = {{1.0f, 1.0f, 1.0f, 1.0f}};
    MPropCol *pcol = (MPropCol *)data;
    for (int i = 0; i < count; i++) {
      copy_v4_v4(pcol[i].color, default_propcol.color);
    }
  }
  
  static void layerInterp_propcol(const void **sources,
                                  const float *weights,
                                  const float *UNUSED(sub_weights),
                                  int count,
                                  void *dest)
  {
    MPropCol *mc = dest;
    float col[4] = {0.0f, 0.0f, 0.0f, 0.0f};
    for (int i = 0; i < count; i++) {
      const float interp_weight = weights[i];
      const MPropCol *src = sources[i];
      madd_v4_v4fl(col, src->color, interp_weight);
    }
    copy_v4_v4(mc->color, col);
  }
  
  static int layerMaxNum_propcol(void)
  {
    return MAX_MCOL;
  }
  
  static void layerInterp_propfloat3(const void **sources,
                                     const float *weights,
                                     const float *UNUSED(sub_weights),
                                     int count,
                                     void *dest)
  {
    vec3f result = {0.0f, 0.0f, 0.0f};
    for (int i = 0; i < count; i++) {
      const float interp_weight = weights[i];
      const vec3f *src = sources[i];
      madd_v3_v3fl(&result.x, &src->x, interp_weight);
    }
    copy_v3_v3((float *)dest, &result.x);
  }
  
  static void layerMultiply_propfloat3(void *data, float fac)
  {
    vec3f *vec = data;
    vec->x *= fac;
    vec->y *= fac;
    vec->z *= fac;
  }
  
  static void layerAdd_propfloat3(void *data1, const void *data2)
  {
    vec3f *vec1 = data1;
    const vec3f *vec2 = data2;
    vec1->x += vec2->x;
    vec1->y += vec2->y;
    vec1->z += vec2->z;
  }
  
  static bool layerValidate_propfloat3(void *data, const uint totitems, const bool do_fixes)
  {
    float *values = data;
    bool has_errors = false;
    for (int i = 0; i < totitems * 3; i++) {
      if (!isfinite(values[i])) {
        if (do_fixes) {
          values[i] = 0.0f;
        }
        has_errors = true;
      }
    }
    return has_errors;
  }
  
  static void layerInterp_propfloat2(const void **sources,
                                     const float *weights,
                                     const float *UNUSED(sub_weights),
                                     int count,
                                     void *dest)
  {
    vec2f result = {0.0f, 0.0f};
    for (int i = 0; i < count; i++) {
      const float interp_weight = weights[i];
      const vec2f *src = sources[i];
      madd_v2_v2fl(&result.x, &src->x, interp_weight);
    }
    copy_v2_v2((float *)dest, &result.x);
  }
  
  static void layerMultiply_propfloat2(void *data, float fac)
  {
    vec2f *vec = data;
    vec->x *= fac;
    vec->y *= fac;
  }
  
  static void layerAdd_propfloat2(void *data1, const void *data2)
  {
    vec2f *vec1 = data1;
    const vec2f *vec2 = data2;
    vec1->x += vec2->x;
    vec1->y += vec2->y;
  }
  
  static bool layerValidate_propfloat2(void *data, const uint totitems, const bool do_fixes)
  {
    float *values = data;
    bool has_errors = false;
    for (int i = 0; i < totitems * 2; i++) {
      if (!isfinite(values[i])) {
        if (do_fixes) {
          values[i] = 0.0f;
        }
        has_errors = true;
      }
    }
    return has_errors;
  }
  
  static const LayerTypeInfo LAYERTYPEINFO[CD_NUMTYPES] = {
      /* 0: CD_MVERT */
      {sizeof(MVert), "MVert", 1, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 1: CD_MSTICKY */ /* DEPRECATED */
      {sizeof(float[2]), "", 1, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 2: CD_MDEFORMVERT */
      {sizeof(MDeformVert),
       "MDeformVert",
       1,
       NULL,
       layerCopy_mdeformvert,
       layerFree_mdeformvert,
       layerInterp_mdeformvert,
       NULL,
       NULL},
      /* 3: CD_MEDGE */
      {sizeof(MEdge), "MEdge", 1, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 4: CD_MFACE */
      {sizeof(MFace), "MFace", 1, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 5: CD_MTFACE */
      {sizeof(MTFace),
       "MTFace",
       1,
       N_("UVMap"),
       layerCopy_tface,
       NULL,
       layerInterp_tface,
       layerSwap_tface,
       layerDefault_tface,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       layerMaxNum_tface},
      /* 6: CD_MCOL */
      /* 4 MCol structs per face */
      {sizeof(MCol[4]),
       "MCol",
       4,
       N_("Col"),
       NULL,
       NULL,
       layerInterp_mcol,
       layerSwap_mcol,
       layerDefault_mcol,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       layerMaxNum_mloopcol},
      /* 7: CD_ORIGINDEX */
      {sizeof(int), "", 0, NULL, NULL, NULL, NULL, NULL, layerDefault_origindex},
      /* 8: CD_NORMAL */
      /* 3 floats per normal vector */
      {sizeof(float[3]),
       "vec3f",
       1,
       NULL,
       NULL,
       NULL,
       layerInterp_normal,
       NULL,
       NULL,
       layerValidate_normal,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       layerCopyValue_normal},
      /* 9: CD_FACEMAP */
      {sizeof(int), "", 0, NULL, NULL, NULL, NULL, NULL, layerDefault_fmap, NULL},
      /* 10: CD_PROP_FLOAT */
      {sizeof(MFloatProperty),
       "MFloatProperty",
       1,
       N_("Float"),
       layerCopy_propFloat,
       NULL,
       NULL,
       NULL,
       NULL,
       layerValidate_propFloat},
      /* 11: CD_PROP_INT32 */
      {sizeof(MIntProperty), "MIntProperty", 1, N_("Int"), layerCopy_propInt, NULL, NULL, NULL},
      /* 12: CD_PROP_STRING */
      {sizeof(MStringProperty),
       "MStringProperty",
       1,
       N_("String"),
       layerCopy_propString,
       NULL,
       NULL,
       NULL},
      /* 13: CD_ORIGSPACE */
      {sizeof(OrigSpaceFace),
       "OrigSpaceFace",
       1,
       N_("UVMap"),
       layerCopy_origspace_face,
       NULL,
       layerInterp_origspace_face,
       layerSwap_origspace_face,
       layerDefault_origspace_face},
      /* 14: CD_ORCO */
      {sizeof(float[3]), "", 0, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 15: CD_MTEXPOLY */ /* DEPRECATED */
      /* note, when we expose the UV Map / TexFace split to the user,
       * change this back to face Texture. */
      {sizeof(int), "", 0, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 16: CD_MLOOPUV */
      {sizeof(MLoopUV),
       "MLoopUV",
       1,
       N_("UVMap"),
       NULL,
       NULL,
       layerInterp_mloopuv,
       NULL,
       NULL,
       layerValidate_mloopuv,
       layerEqual_mloopuv,
       layerMultiply_mloopuv,
       layerInitMinMax_mloopuv,
       layerAdd_mloopuv,
       layerDoMinMax_mloopuv,
       layerCopyValue_mloopuv,
       NULL,
       NULL,
       NULL,
       layerMaxNum_tface},
      /* 17: CD_MLOOPCOL */
      {sizeof(MLoopCol),
       "MLoopCol",
       1,
       N_("Col"),
       NULL,
       NULL,
       layerInterp_mloopcol,
       NULL,
       layerDefault_mloopcol,
       NULL,
       layerEqual_mloopcol,
       layerMultiply_mloopcol,
       layerInitMinMax_mloopcol,
       layerAdd_mloopcol,
       layerDoMinMax_mloopcol,
       layerCopyValue_mloopcol,
       NULL,
       NULL,
       NULL,
       layerMaxNum_mloopcol},
      /* 18: CD_TANGENT */
      {sizeof(float[4][4]), "", 0, N_("Tangent"), NULL, NULL, NULL, NULL, NULL},
      /* 19: CD_MDISPS */
      {sizeof(MDisps),
       "MDisps",
       1,
       NULL,
       layerCopy_mdisps,
       layerFree_mdisps,
       NULL,
       layerSwap_mdisps,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       NULL,
       layerRead_mdisps,
       layerWrite_mdisps,
       layerFilesize_mdisps},
      /* 20: CD_PREVIEW_MCOL */
      {sizeof(MCol[4]),
       "MCol",
       4,
       N_("PreviewCol"),
       NULL,
       NULL,
       layerInterp_mcol,
       layerSwap_mcol,
       layerDefault_mcol},
      /* 21: CD_ID_MCOL */ /* DEPRECATED */
      {sizeof(MCol[4]), "", 0, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 22: CD_TEXTURE_MCOL */
      {sizeof(MCol[4]),
       "MCol",
       4,
       N_("TexturedCol"),
       NULL,
       NULL,
       layerInterp_mcol,
       layerSwap_mcol,
       layerDefault_mcol},
      /* 23: CD_CLOTH_ORCO */
      {sizeof(float[3]), "", 0, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 24: CD_RECAST */
      {sizeof(MRecast), "MRecast", 1, N_("Recast"), NULL, NULL, NULL, NULL},
  
      /* BMESH ONLY */
      /* 25: CD_MPOLY */
      {sizeof(MPoly), "MPoly", 1, N_("NGon Face"), NULL, NULL, NULL, NULL, NULL},
      /* 26: CD_MLOOP */
      {sizeof(MLoop), "MLoop", 1, N_("NGon Face-Vertex"), NULL, NULL, NULL, NULL, NULL},
      /* 27: CD_SHAPE_KEYINDEX */
      {sizeof(int), "", 0, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 28: CD_SHAPEKEY */
      {sizeof(float[3]), "", 0, N_("ShapeKey"), NULL, NULL, layerInterp_shapekey},
      /* 29: CD_BWEIGHT */
      {sizeof(float), "", 0, N_("BevelWeight"), NULL, NULL, layerInterp_bweight},
      /* 30: CD_CREASE */
      {sizeof(float), "", 0, N_("SubSurfCrease"), NULL, NULL, layerInterp_bweight},
      /* 31: CD_ORIGSPACE_MLOOP */
      {sizeof(OrigSpaceLoop),
       "OrigSpaceLoop",
       1,
       N_("OS Loop"),
       NULL,
       NULL,
       layerInterp_mloop_origspace,
       NULL,
       NULL,
       NULL,
       layerEqual_mloop_origspace,
       layerMultiply_mloop_origspace,
       layerInitMinMax_mloop_origspace,
       layerAdd_mloop_origspace,
       layerDoMinMax_mloop_origspace,
       layerCopyValue_mloop_origspace},
      /* 32: CD_PREVIEW_MLOOPCOL */
      {sizeof(MLoopCol),
       "MLoopCol",
       1,
       N_("PreviewLoopCol"),
       NULL,
       NULL,
       layerInterp_mloopcol,
       NULL,
       layerDefault_mloopcol,
       NULL,
       layerEqual_mloopcol,
       layerMultiply_mloopcol,
       layerInitMinMax_mloopcol,
       layerAdd_mloopcol,
       layerDoMinMax_mloopcol,
       layerCopyValue_mloopcol},
      /* 33: CD_BM_ELEM_PYPTR */
      {sizeof(void *),
       "",
       1,
       NULL,
       layerCopy_bmesh_elem_py_ptr,
       layerFree_bmesh_elem_py_ptr,
       NULL,
       NULL,
       NULL},
  
      /* END BMESH ONLY */
  
      /* 34: CD_PAINT_MASK */
      {sizeof(float), "", 0, NULL, NULL, NULL, layerInterp_paint_mask, NULL, NULL},
      /* 35: CD_GRID_PAINT_MASK */
      {sizeof(GridPaintMask),
       "GridPaintMask",
       1,
       NULL,
       layerCopy_grid_paint_mask,
       layerFree_grid_paint_mask,
       NULL,
       NULL,
       NULL},
      /* 36: CD_MVERT_SKIN */
      {sizeof(MVertSkin),
       "MVertSkin",
       1,
       NULL,
       layerCopy_mvert_skin,
       NULL,
       layerInterp_mvert_skin,
       NULL,
       layerDefault_mvert_skin},
      /* 37: CD_FREESTYLE_EDGE */
      {sizeof(FreestyleEdge), "FreestyleEdge", 1, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 38: CD_FREESTYLE_FACE */
      {sizeof(FreestyleFace), "FreestyleFace", 1, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 39: CD_MLOOPTANGENT */
      {sizeof(float[4]), "", 0, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 40: CD_TESSLOOPNORMAL */
      {sizeof(short[4][3]), "", 0, NULL, NULL, NULL, NULL, layerSwap_flnor, NULL},
      /* 41: CD_CUSTOMLOOPNORMAL */
      {sizeof(short[2]), "vec2s", 1, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 42: CD_SCULPT_FACE_SETS */
      {sizeof(int), "", 0, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 43: CD_LOCATION */
      {sizeof(float[3]), "vec3f", 1, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 44: CD_RADIUS */
      {sizeof(float), "MFloatProperty", 1, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 45: CD_HAIRCURVE */
      {sizeof(HairCurve), "HairCurve", 1, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 46: CD_HAIRMAPPING */
      {sizeof(HairMapping), "HairMapping", 1, NULL, NULL, NULL, NULL, NULL, NULL},
      /* 47: CD_PROP_COLOR */
      {sizeof(MPropCol),
       "MPropCol",
       1,
       N_("Color"),
       NULL,
       NULL,
       layerInterp_propcol,
       NULL,
       layerDefault_propcol,
       NULL,
       layerEqual_propcol,
       layerMultiply_propcol,
       layerInitMinMax_propcol,
       layerAdd_propcol,
       layerDoMinMax_propcol,
       layerCopyValue_propcol,
       NULL,
       NULL,
       NULL,
       layerMaxNum_propcol},
      /* 48: CD_PROP_FLOAT3 */
      {sizeof(float[3]),
       "vec3f",
       1,
       N_("Float3"),
       NULL,
       NULL,
       layerInterp_propfloat3,
       NULL,
       NULL,
       layerValidate_propfloat3,
       NULL,
       layerMultiply_propfloat3,
       NULL,
       layerAdd_propfloat3},
      /* 49: CD_PROP_FLOAT2 */
      {sizeof(float[2]),
       "vec2f",
       1,
       N_("Float2"),
       NULL,
       NULL,
       layerInterp_propfloat2,
       NULL,
       NULL,
       layerValidate_propfloat2,
       NULL,
       layerMultiply_propfloat2,
       NULL,
       layerAdd_propfloat2},
  };
  
  static const char *LAYERTYPENAMES[CD_NUMTYPES] = {
      /*   0-4 */ "CDMVert",
      "CDMSticky",
      "CDMDeformVert",
      "CDMEdge",
      "CDMFace",
      /*   5-9 */ "CDMTFace",
      "CDMCol",
      "CDOrigIndex",
      "CDNormal",
      "CDFaceMap",
      /* 10-14 */ "CDMFloatProperty",
      "CDMIntProperty",
      "CDMStringProperty",
      "CDOrigSpace",
      "CDOrco",
      /* 15-19 */ "CDMTexPoly",
      "CDMLoopUV",
      "CDMloopCol",
      "CDTangent",
      "CDMDisps",
      /* 20-24 */ "CDPreviewMCol",
      "CDIDMCol",
      "CDTextureMCol",
      "CDClothOrco",
      "CDMRecast",
  
      /* BMESH ONLY */
      /* 25-29 */ "CDMPoly",
      "CDMLoop",
      "CDShapeKeyIndex",
      "CDShapeKey",
      "CDBevelWeight",
      /* 30-34 */ "CDSubSurfCrease",
      "CDOrigSpaceLoop",
      "CDPreviewLoopCol",
      "CDBMElemPyPtr",
      "CDPaintMask",
      /* 35-36 */ "CDGridPaintMask",
      "CDMVertSkin",
      /* 37-38 */ "CDFreestyleEdge",
      "CDFreestyleFace",
      /* 39-42 */ "CDMLoopTangent",
      "CDTessLoopNormal",
      "CDCustomLoopNormal",
      "CDSculptFaceGroups",
      /* 43-46 */ "CDHairPoint",
      "CDHairCurve",
      "CDHairMapping",
      "CDPoint",
      "CDPropCol",
      "CDPropFloat3",
      "CDPropFloat2",
  };
  
  const CustomData_MeshMasks CD_MASK_BAREMESH = {
      .vmask = CD_MASK_MVERT | CD_MASK_BWEIGHT,
      .emask = CD_MASK_MEDGE | CD_MASK_BWEIGHT,
      .fmask = 0,
      .lmask = CD_MASK_MLOOP,
      .pmask = CD_MASK_MPOLY | CD_MASK_FACEMAP,
  };
  const CustomData_MeshMasks CD_MASK_BAREMESH_ORIGINDEX = {
      .vmask = CD_MASK_MVERT | CD_MASK_BWEIGHT | CD_MASK_ORIGINDEX,
      .emask = CD_MASK_MEDGE | CD_MASK_BWEIGHT | CD_MASK_ORIGINDEX,
      .fmask = 0,
      .lmask = CD_MASK_MLOOP,
      .pmask = CD_MASK_MPOLY | CD_MASK_FACEMAP | CD_MASK_ORIGINDEX,
  };
  const CustomData_MeshMasks CD_MASK_MESH = {
      .vmask = (CD_MASK_MVERT | CD_MASK_MDEFORMVERT | CD_MASK_MVERT_SKIN | CD_MASK_PAINT_MASK |
                CD_MASK_PROP_ALL | CD_MASK_PROP_COLOR),
      .emask = (CD_MASK_MEDGE | CD_MASK_FREESTYLE_EDGE | CD_MASK_PROP_ALL),
      .fmask = 0,
      .lmask = (CD_MASK_MLOOP | CD_MASK_MDISPS | CD_MASK_MLOOPUV | CD_MASK_MLOOPCOL |
                CD_MASK_CUSTOMLOOPNORMAL | CD_MASK_GRID_PAINT_MASK | CD_MASK_PROP_ALL),
      .pmask = (CD_MASK_MPOLY | CD_MASK_RECAST | CD_MASK_FACEMAP | CD_MASK_FREESTYLE_FACE |
                CD_MASK_PROP_ALL | CD_MASK_SCULPT_FACE_SETS),
  };
  const CustomData_MeshMasks CD_MASK_EDITMESH = {
      .vmask = (CD_MASK_MDEFORMVERT | CD_MASK_PAINT_MASK | CD_MASK_MVERT_SKIN | CD_MASK_SHAPEKEY |
                CD_MASK_SHAPE_KEYINDEX | CD_MASK_PROP_ALL | CD_MASK_PROP_COLOR),
      .emask = (CD_MASK_PROP_ALL),
      .fmask = 0,
      .lmask = (CD_MASK_MDISPS | CD_MASK_MLOOPUV | CD_MASK_MLOOPCOL | CD_MASK_CUSTOMLOOPNORMAL |
                CD_MASK_GRID_PAINT_MASK | CD_MASK_PROP_ALL),
      .pmask = (CD_MASK_RECAST | CD_MASK_FACEMAP | CD_MASK_PROP_ALL | CD_MASK_SCULPT_FACE_SETS),
  };
  const CustomData_MeshMasks CD_MASK_DERIVEDMESH = {
      .vmask = (CD_MASK_ORIGINDEX | CD_MASK_MDEFORMVERT | CD_MASK_SHAPEKEY | CD_MASK_MVERT_SKIN |
                CD_MASK_PAINT_MASK | CD_MASK_ORCO | CD_MASK_CLOTH_ORCO | CD_MASK_PROP_ALL |
                CD_MASK_PROP_COLOR),
      .emask = (CD_MASK_ORIGINDEX | CD_MASK_FREESTYLE_EDGE | CD_MASK_PROP_ALL),
      .fmask = (CD_MASK_ORIGINDEX | CD_MASK_ORIGSPACE | CD_MASK_PREVIEW_MCOL | CD_MASK_TANGENT),
      .lmask = (CD_MASK_MLOOPUV | CD_MASK_MLOOPCOL | CD_MASK_CUSTOMLOOPNORMAL |
                CD_MASK_PREVIEW_MLOOPCOL | CD_MASK_ORIGSPACE_MLOOP |
                CD_MASK_PROP_ALL), /* XXX MISSING CD_MASK_MLOOPTANGENT ? */
      .pmask = (CD_MASK_ORIGINDEX | CD_MASK_RECAST | CD_MASK_FREESTYLE_FACE | CD_MASK_FACEMAP |
                CD_MASK_PROP_ALL | CD_MASK_SCULPT_FACE_SETS),
  };
  const CustomData_MeshMasks CD_MASK_BMESH = {
      .vmask = (CD_MASK_MDEFORMVERT | CD_MASK_BWEIGHT | CD_MASK_MVERT_SKIN | CD_MASK_SHAPEKEY |
                CD_MASK_SHAPE_KEYINDEX | CD_MASK_PAINT_MASK | CD_MASK_PROP_ALL | CD_MASK_PROP_COLOR),
      .emask = (CD_MASK_BWEIGHT | CD_MASK_CREASE | CD_MASK_FREESTYLE_EDGE | CD_MASK_PROP_ALL),
      .fmask = 0,
      .lmask = (CD_MASK_MDISPS | CD_MASK_MLOOPUV | CD_MASK_MLOOPCOL | CD_MASK_CUSTOMLOOPNORMAL |
                CD_MASK_GRID_PAINT_MASK | CD_MASK_PROP_ALL),
      .pmask = (CD_MASK_RECAST | CD_MASK_FREESTYLE_FACE | CD_MASK_FACEMAP | CD_MASK_PROP_ALL |
                CD_MASK_SCULPT_FACE_SETS),
  };
  /**
   * cover values copied by #BKE_mesh_loops_to_tessdata
   */
  const CustomData_MeshMasks CD_MASK_FACECORNERS = {
      .vmask = 0,
      .emask = 0,
      .fmask = (CD_MASK_MTFACE | CD_MASK_MCOL | CD_MASK_PREVIEW_MCOL | CD_MASK_ORIGSPACE |
                CD_MASK_TESSLOOPNORMAL | CD_MASK_TANGENT),
      .lmask = (CD_MASK_MLOOPUV | CD_MASK_MLOOPCOL | CD_MASK_PREVIEW_MLOOPCOL |
                CD_MASK_ORIGSPACE_MLOOP | CD_MASK_NORMAL | CD_MASK_MLOOPTANGENT),
      .pmask = 0,
  };
  const CustomData_MeshMasks CD_MASK_EVERYTHING = {
      .vmask = (CD_MASK_MVERT | CD_MASK_BM_ELEM_PYPTR | CD_MASK_ORIGINDEX | CD_MASK_NORMAL |
                CD_MASK_MDEFORMVERT | CD_MASK_BWEIGHT | CD_MASK_MVERT_SKIN | CD_MASK_ORCO |
                CD_MASK_CLOTH_ORCO | CD_MASK_SHAPEKEY | CD_MASK_SHAPE_KEYINDEX | CD_MASK_PAINT_MASK |
                CD_MASK_PROP_ALL | CD_MASK_PROP_COLOR),
      .emask = (CD_MASK_MEDGE | CD_MASK_BM_ELEM_PYPTR | CD_MASK_ORIGINDEX | CD_MASK_BWEIGHT |
                CD_MASK_CREASE | CD_MASK_FREESTYLE_EDGE | CD_MASK_PROP_ALL),
      .fmask = (CD_MASK_MFACE | CD_MASK_ORIGINDEX | CD_MASK_NORMAL | CD_MASK_MTFACE | CD_MASK_MCOL |
                CD_MASK_ORIGSPACE | CD_MASK_TANGENT | CD_MASK_TESSLOOPNORMAL | CD_MASK_PREVIEW_MCOL |
                CD_MASK_PROP_ALL),
      .lmask = (CD_MASK_MLOOP | CD_MASK_BM_ELEM_PYPTR | CD_MASK_MDISPS | CD_MASK_NORMAL |
                CD_MASK_MLOOPUV | CD_MASK_MLOOPCOL | CD_MASK_CUSTOMLOOPNORMAL |
                CD_MASK_MLOOPTANGENT | CD_MASK_PREVIEW_MLOOPCOL | CD_MASK_ORIGSPACE_MLOOP |
                CD_MASK_GRID_PAINT_MASK | CD_MASK_PROP_ALL),
      .pmask = (CD_MASK_MPOLY | CD_MASK_BM_ELEM_PYPTR | CD_MASK_ORIGINDEX | CD_MASK_NORMAL |
                CD_MASK_RECAST | CD_MASK_FACEMAP | CD_MASK_FREESTYLE_FACE | CD_MASK_PROP_ALL |
                CD_MASK_SCULPT_FACE_SETS),
  };
  
  static const LayerTypeInfo *layerType_getInfo(int type)
  {
    if (type < 0 || type >= CD_NUMTYPES) {
      return NULL;
    }
  
    return &LAYERTYPEINFO[type];
  }
  
  static const char *layerType_getName(int type)
  {
    if (type < 0 || type >= CD_NUMTYPES) {
      return NULL;
    }
  
    return LAYERTYPENAMES[type];
  }
  
  void customData_mask_layers__print(const CustomData_MeshMasks *mask)
  {
    printf("verts mask=0x%lx:\n", (long unsigned int)mask->vmask);
    for (int i = 0; i < CD_NUMTYPES; i++) {
      if (mask->vmask & CD_TYPE_AS_MASK(i)) {
        printf("  %s\n", layerType_getName(i));
      }
    }
  
    printf("edges mask=0x%lx:\n", (long unsigned int)mask->emask);
    for (int i = 0; i < CD_NUMTYPES; i++) {
      if (mask->emask & CD_TYPE_AS_MASK(i)) {
        printf("  %s\n", layerType_getName(i));
      }
    }
  
    printf("faces mask=0x%lx:\n", (long unsigned int)mask->fmask);
    for (int i = 0; i < CD_NUMTYPES; i++) {
      if (mask->fmask & CD_TYPE_AS_MASK(i)) {
        printf("  %s\n", layerType_getName(i));
      }
    }
  
    printf("loops mask=0x%lx:\n", (long unsigned int)mask->lmask);
    for (int i = 0; i < CD_NUMTYPES; i++) {
      if (mask->lmask & CD_TYPE_AS_MASK(i)) {
        printf("  %s\n", layerType_getName(i));
      }
    }
  
    printf("polys mask=0x%lx:\n", (long unsigned int)mask->pmask);
    for (int i = 0; i < CD_NUMTYPES; i++) {
      if (mask->pmask & CD_TYPE_AS_MASK(i)) {
        printf("  %s\n", layerType_getName(i));
      }
    }
  }
  
  /********************* CustomData functions *********************/
  static void customData_update_offsets(CustomData *data);
  
  static CustomDataLayer *customData_add_layer__internal(CustomData *data,
                                                         int type,
                                                         eCDAllocType alloctype,
                                                         void *layerdata,
                                                         int totelem,
                                                         const char *name);
  
  void CustomData_update_typemap(CustomData *data)
  {
    int i, lasttype = -1;
  
    for (i = 0; i < CD_NUMTYPES; i++) {
      data->typemap[i] = -1;
    }
  
    for (i = 0; i < data->totlayer; i++) {
      const int type = data->layers[i].type;
      if (type != lasttype) {
        data->typemap[type] = i;
        lasttype = type;
      }
    }
  }
  
  /* currently only used in BLI_assert */
  #ifndef NDEBUG
  static bool customdata_typemap_is_valid(const CustomData *data)
  {
    CustomData data_copy = *data;
    CustomData_update_typemap(&data_copy);
    return (memcmp(data->typemap, data_copy.typemap, sizeof(data->typemap)) == 0);
  }
  #endif
  
  bool CustomData_merge(const struct CustomData *source,
                        struct CustomData *dest,
                        CustomDataMask mask,
                        eCDAllocType alloctype,
                        int totelem)
  {
    /*const LayerTypeInfo *typeInfo;*/
    CustomDataLayer *layer, *newlayer;
    void *data;
    int i, type, lasttype = -1, lastactive = 0, lastrender = 0, lastclone = 0, lastmask = 0,
                 flag = 0;
    int number = 0, maxnumber = -1;
    bool changed = false;
  
    for (i = 0; i < source->totlayer; i++) {
      layer = &source->layers[i];
      /*typeInfo = layerType_getInfo(layer->type);*/ /*UNUSED*/
  
      type = layer->type;
      flag = layer->flag;
  
      if (type != lasttype) {
        number = 0;
        maxnumber = CustomData_layertype_layers_max(type);
        lastactive = layer->active;
        lastrender = layer->active_rnd;
        lastclone = layer->active_clone;
        lastmask = layer->active_mask;
        lasttype = type;
      }
      else {
        number++;
      }
  
      if (flag & CD_FLAG_NOCOPY) {
        continue;
      }
      if (!(mask & CD_TYPE_AS_MASK(type))) {
        continue;
      }
      if ((maxnumber != -1) && (number >= maxnumber)) {
        continue;
      }
      if (CustomData_get_named_layer_index(dest, type, layer->name) != -1) {
        continue;
      }
  
      switch (alloctype) {
        case CD_ASSIGN:
        case CD_REFERENCE:
        case CD_DUPLICATE:
          data = layer->data;
          break;
        default:
          data = NULL;
          break;
      }
  
      if ((alloctype == CD_ASSIGN) && (flag & CD_FLAG_NOFREE)) {
        newlayer = customData_add_layer__internal(
            dest, type, CD_REFERENCE, data, totelem, layer->name);
      }
      else {
        newlayer = customData_add_layer__internal(dest, type, alloctype, data, totelem, layer->name);
      }
  
      if (newlayer) {
        newlayer->uid = layer->uid;
  
        newlayer->active = lastactive;
        newlayer->active_rnd = lastrender;
        newlayer->active_clone = lastclone;
        newlayer->active_mask = lastmask;
        newlayer->flag |= flag & (CD_FLAG_EXTERNAL | CD_FLAG_IN_MEMORY);
        changed = true;
      }
    }
  
    CustomData_update_typemap(dest);
    return changed;
  }
  
  /* NOTE: Take care of referenced layers by yourself! */
  void CustomData_realloc(CustomData *data, int totelem)
  {
    for (int i = 0; i < data->totlayer; i++) {
      CustomDataLayer *layer = &data->layers[i];
      const LayerTypeInfo *typeInfo;
      if (layer->flag & CD_FLAG_NOFREE) {
        continue;
      }
      typeInfo = layerType_getInfo(layer->type);
      layer->data = MEM_reallocN(layer->data, (size_t)totelem * typeInfo->size);
    }
  }
  
  void CustomData_copy(const struct CustomData *source,
                       struct CustomData *dest,
                       CustomDataMask mask,
                       eCDAllocType alloctype,
                       int totelem)
  {
    CustomData_reset(dest);
  
    if (source->external) {
      dest->external = MEM_dupallocN(source->external);
    }
  
    CustomData_merge(source, dest, mask, alloctype, totelem);
  }
  
  static void customData_free_layer__internal(CustomDataLayer *layer, int totelem)
  {
    const LayerTypeInfo *typeInfo;
  
    if (!(layer->flag & CD_FLAG_NOFREE) && layer->data) {
      typeInfo = layerType_getInfo(layer->type);
  
      if (typeInfo->free) {
        typeInfo->free(layer->data, totelem, typeInfo->size);
      }
  
      if (layer->data) {
        MEM_freeN(layer->data);
      }
    }
  }
  
  static void CustomData_external_free(CustomData *data)
  {
    if (data->external) {
      MEM_freeN(data->external);
      data->external = NULL;
    }
  }
  
  void CustomData_reset(CustomData *data)
  {
    memset(data, 0, sizeof(*data));
    copy_vn_i(data->typemap, CD_NUMTYPES, -1);
  }
  
  void CustomData_free(CustomData *data, int totelem)
  {
    for (int i = 0; i < data->totlayer; i++) {
      customData_free_layer__internal(&data->layers[i], totelem);
    }
  
    if (data->layers) {
      MEM_freeN(data->layers);
    }
  
    CustomData_external_free(data);
    CustomData_reset(data);
  }
  
  void CustomData_free_typemask(struct CustomData *data, int totelem, CustomDataMask mask)
  {
    for (int i = 0; i < data->totlayer; i++) {
      CustomDataLayer *layer = &data->layers[i];
      if (!(mask & CD_TYPE_AS_MASK(layer->type))) {
        continue;
      }
      customData_free_layer__internal(layer, totelem);
    }
  
    if (data->layers) {
      MEM_freeN(data->layers);
    }
  
    CustomData_external_free(data);
    CustomData_reset(data);
  }
  
  static void customData_update_offsets(CustomData *data)
  {
    const LayerTypeInfo *typeInfo;
    int offset = 0;
  
    for (int i = 0; i < data->totlayer; i++) {
      typeInfo = layerType_getInfo(data->layers[i].type);
  
      data->layers[i].offset = offset;
      offset += typeInfo->size;
    }
  
    data->totsize = offset;
    CustomData_update_typemap(data);
  }
  
  /* to use when we're in the middle of modifying layers */
  static int CustomData_get_layer_index__notypemap(const CustomData *data, int type)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        return i;
      }
    }
  
    return -1;
  }
  
  /* -------------------------------------------------------------------- */
  /* index values to access the layers (offset from the layer start) */
  
  int CustomData_get_layer_index(const CustomData *data, int type)
  {
    BLI_assert(customdata_typemap_is_valid(data));
    return data->typemap[type];
  }
  
  int CustomData_get_layer_index_n(const struct CustomData *data, int type, int n)
  {
    BLI_assert(n >= 0);
    int i = CustomData_get_layer_index(data, type);
  
    if (i != -1) {
      BLI_assert(i + n < data->totlayer);
      i = (data->layers[i + n].type == type) ? (i + n) : (-1);
    }
  
    return i;
  }
  
  int CustomData_get_named_layer_index(const CustomData *data, int type, const char *name)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        if (STREQ(data->layers[i].name, name)) {
          return i;
        }
      }
    }
  
    return -1;
  }
  
  int CustomData_get_active_layer_index(const CustomData *data, int type)
  {
    const int layer_index = data->typemap[type];
    BLI_assert(customdata_typemap_is_valid(data));
    return (layer_index != -1) ? layer_index + data->layers[layer_index].active : -1;
  }
  
  int CustomData_get_render_layer_index(const CustomData *data, int type)
  {
    const int layer_index = data->typemap[type];
    BLI_assert(customdata_typemap_is_valid(data));
    return (layer_index != -1) ? layer_index + data->layers[layer_index].active_rnd : -1;
  }
  
  int CustomData_get_clone_layer_index(const CustomData *data, int type)
  {
    const int layer_index = data->typemap[type];
    BLI_assert(customdata_typemap_is_valid(data));
    return (layer_index != -1) ? layer_index + data->layers[layer_index].active_clone : -1;
  }
  
  int CustomData_get_stencil_layer_index(const CustomData *data, int type)
  {
    const int layer_index = data->typemap[type];
    BLI_assert(customdata_typemap_is_valid(data));
    return (layer_index != -1) ? layer_index + data->layers[layer_index].active_mask : -1;
  }
  
  /* -------------------------------------------------------------------- */
  /* index values per layer type */
  
  int CustomData_get_named_layer(const struct CustomData *data, int type, const char *name)
  {
    const int named_index = CustomData_get_named_layer_index(data, type, name);
    const int layer_index = data->typemap[type];
    BLI_assert(customdata_typemap_is_valid(data));
    return (named_index != -1) ? named_index - layer_index : -1;
  }
  
  int CustomData_get_active_layer(const CustomData *data, int type)
  {
    const int layer_index = data->typemap[type];
    BLI_assert(customdata_typemap_is_valid(data));
    return (layer_index != -1) ? data->layers[layer_index].active : -1;
  }
  
  int CustomData_get_render_layer(const CustomData *data, int type)
  {
    const int layer_index = data->typemap[type];
    BLI_assert(customdata_typemap_is_valid(data));
    return (layer_index != -1) ? data->layers[layer_index].active_rnd : -1;
  }
  
  int CustomData_get_clone_layer(const CustomData *data, int type)
  {
    const int layer_index = data->typemap[type];
    BLI_assert(customdata_typemap_is_valid(data));
    return (layer_index != -1) ? data->layers[layer_index].active_clone : -1;
  }
  
  int CustomData_get_stencil_layer(const CustomData *data, int type)
  {
    const int layer_index = data->typemap[type];
    BLI_assert(customdata_typemap_is_valid(data));
    return (layer_index != -1) ? data->layers[layer_index].active_mask : -1;
  }
  
  void CustomData_set_layer_active(CustomData *data, int type, int n)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        data->layers[i].active = n;
      }
    }
  }
  
  void CustomData_set_layer_render(CustomData *data, int type, int n)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        data->layers[i].active_rnd = n;
      }
    }
  }
  
  void CustomData_set_layer_clone(CustomData *data, int type, int n)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        data->layers[i].active_clone = n;
      }
    }
  }
  
  void CustomData_set_layer_stencil(CustomData *data, int type, int n)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        data->layers[i].active_mask = n;
      }
    }
  }
  
  /* For using with an index from CustomData_get_active_layer_index and
   * CustomData_get_render_layer_index. */
  void CustomData_set_layer_active_index(CustomData *data, int type, int n)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        data->layers[i].active = n - i;
      }
    }
  }
  
  void CustomData_set_layer_render_index(CustomData *data, int type, int n)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        data->layers[i].active_rnd = n - i;
      }
    }
  }
  
  void CustomData_set_layer_clone_index(CustomData *data, int type, int n)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        data->layers[i].active_clone = n - i;
      }
    }
  }
  
  void CustomData_set_layer_stencil_index(CustomData *data, int type, int n)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        data->layers[i].active_mask = n - i;
      }
    }
  }
  
  void CustomData_set_layer_flag(struct CustomData *data, int type, int flag)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        data->layers[i].flag |= flag;
      }
    }
  }
  
  void CustomData_clear_layer_flag(struct CustomData *data, int type, int flag)
  {
    const int nflag = ~flag;
  
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        data->layers[i].flag &= nflag;
      }
    }
  }
  
  static bool customData_resize(CustomData *data, int amount)
  {
    CustomDataLayer *tmp = MEM_calloc_arrayN(
        (data->maxlayer + amount), sizeof(*tmp), "CustomData->layers");
    if (!tmp) {
      return false;
    }
  
    data->maxlayer += amount;
    if (data->layers) {
      memcpy(tmp, data->layers, sizeof(*tmp) * data->totlayer);
      MEM_freeN(data->layers);
    }
    data->layers = tmp;
  
    return true;
  }
  
  static CustomDataLayer *customData_add_layer__internal(CustomData *data,
                                                         int type,
                                                         eCDAllocType alloctype,
                                                         void *layerdata,
                                                         int totelem,
                                                         const char *name)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
    int flag = 0, index = data->totlayer;
    void *newlayerdata = NULL;
  
    /* Passing a layer-data to copy from with an alloctype that won't copy is
     * most likely a bug */
    BLI_assert(!layerdata || (alloctype == CD_ASSIGN) || (alloctype == CD_DUPLICATE) ||
               (alloctype == CD_REFERENCE));
  
    if (!typeInfo->defaultname && CustomData_has_layer(data, type)) {
      return &data->layers[CustomData_get_layer_index(data, type)];
    }
  
    if (ELEM(alloctype, CD_ASSIGN, CD_REFERENCE)) {
      newlayerdata = layerdata;
    }
    else if (totelem > 0 && typeInfo->size > 0) {
      if (alloctype == CD_DUPLICATE && layerdata) {
        newlayerdata = MEM_malloc_arrayN((size_t)totelem, typeInfo->size, layerType_getName(type));
      }
      else {
        newlayerdata = MEM_calloc_arrayN((size_t)totelem, typeInfo->size, layerType_getName(type));
      }
  
      if (!newlayerdata) {
        return NULL;
      }
    }
  
    if (alloctype == CD_DUPLICATE && layerdata) {
      if (totelem > 0) {
        if (typeInfo->copy) {
          typeInfo->copy(layerdata, newlayerdata, totelem);
        }
        else {
          memcpy(newlayerdata, layerdata, (size_t)totelem * typeInfo->size);
        }
      }
    }
    else if (alloctype == CD_DEFAULT) {
      if (typeInfo->set_default) {
        typeInfo->set_default(newlayerdata, totelem);
      }
    }
    else if (alloctype == CD_REFERENCE) {
      flag |= CD_FLAG_NOFREE;
    }
  
    if (index >= data->maxlayer) {
      if (!customData_resize(data, CUSTOMDATA_GROW)) {
        if (newlayerdata != layerdata) {
          MEM_freeN(newlayerdata);
        }
        return NULL;
      }
    }
  
    data->totlayer++;
  
    /* keep layers ordered by type */
    for (; index > 0 && data->layers[index - 1].type > type; index--) {
      data->layers[index] = data->layers[index - 1];
    }
  
    data->layers[index].type = type;
    data->layers[index].flag = flag;
    data->layers[index].data = newlayerdata;
  
    /* Set default name if none exists. Note we only call DATA_()  once
     * we know there is a default name, to avoid overhead of locale lookups
     * in the depsgraph. */
    if (!name && typeInfo->defaultname) {
      name = DATA_(typeInfo->defaultname);
    }
  
    if (name) {
      BLI_strncpy(data->layers[index].name, name, sizeof(data->layers[index].name));
      CustomData_set_layer_unique_name(data, index);
    }
    else {
      data->layers[index].name[0] = '\0';
    }
  
    if (index > 0 && data->layers[index - 1].type == type) {
      data->layers[index].active = data->layers[index - 1].active;
      data->layers[index].active_rnd = data->layers[index - 1].active_rnd;
      data->layers[index].active_clone = data->layers[index - 1].active_clone;
      data->layers[index].active_mask = data->layers[index - 1].active_mask;
    }
    else {
      data->layers[index].active = 0;
      data->layers[index].active_rnd = 0;
      data->layers[index].active_clone = 0;
      data->layers[index].active_mask = 0;
    }
  
    customData_update_offsets(data);
  
    return &data->layers[index];
  }
  
  void *CustomData_add_layer(
      CustomData *data, int type, eCDAllocType alloctype, void *layerdata, int totelem)
  {
    CustomDataLayer *layer;
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    layer = customData_add_layer__internal(
        data, type, alloctype, layerdata, totelem, typeInfo->defaultname);
    CustomData_update_typemap(data);
  
    if (layer) {
      return layer->data;
    }
  
    return NULL;
  }
  
  /*same as above but accepts a name*/
  void *CustomData_add_layer_named(CustomData *data,
                                   int type,
                                   eCDAllocType alloctype,
                                   void *layerdata,
                                   int totelem,
                                   const char *name)
  {
    CustomDataLayer *layer;
  
    layer = customData_add_layer__internal(data, type, alloctype, layerdata, totelem, name);
    CustomData_update_typemap(data);
  
    if (layer) {
      return layer->data;
    }
  
    return NULL;
  }
  
  bool CustomData_free_layer(CustomData *data, int type, int totelem, int index)
  {
    const int index_first = CustomData_get_layer_index(data, type);
    const int n = index - index_first;
  
    BLI_assert(index >= index_first);
    if ((index_first == -1) || (n < 0)) {
      return false;
    }
    BLI_assert(data->layers[index].type == type);
  
    customData_free_layer__internal(&data->layers[index], totelem);
  
    for (int i = index + 1; i < data->totlayer; i++) {
      data->layers[i - 1] = data->layers[i];
    }
  
    data->totlayer--;
  
    /* if layer was last of type in array, set new active layer */
    int i = CustomData_get_layer_index__notypemap(data, type);
  
    if (i != -1) {
      /* don't decrement zero index */
      const int index_nonzero = n ? n : 1;
      CustomDataLayer *layer;
  
      for (layer = &data->layers[i]; i < data->totlayer && layer->type == type; i++, layer++) {
        if (layer->active >= index_nonzero) {
          layer->active--;
        }
        if (layer->active_rnd >= index_nonzero) {
          layer->active_rnd--;
        }
        if (layer->active_clone >= index_nonzero) {
          layer->active_clone--;
        }
        if (layer->active_mask >= index_nonzero) {
          layer->active_mask--;
        }
      }
    }
  
    if (data->totlayer <= data->maxlayer - CUSTOMDATA_GROW) {
      customData_resize(data, -CUSTOMDATA_GROW);
    }
  
    customData_update_offsets(data);
  
    return true;
  }
  
  bool CustomData_free_layer_active(CustomData *data, int type, int totelem)
  {
    const int index = CustomData_get_active_layer_index(data, type);
    if (index == -1) {
      return false;
    }
    return CustomData_free_layer(data, type, totelem, index);
  }
  
  void CustomData_free_layers(CustomData *data, int type, int totelem)
  {
    const int index = CustomData_get_layer_index(data, type);
    while (CustomData_free_layer(data, type, totelem, index)) {
      /* pass */
    }
  }
  
  bool CustomData_has_layer(const CustomData *data, int type)
  {
    return (CustomData_get_layer_index(data, type) != -1);
  }
  
  int CustomData_number_of_layers(const CustomData *data, int type)
  {
    int number = 0;
  
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].type == type) {
        number++;
      }
    }
  
    return number;
  }
  
  int CustomData_number_of_layers_typemask(const CustomData *data, CustomDataMask mask)
  {
    int number = 0;
  
    for (int i = 0; i < data->totlayer; i++) {
      if (mask & CD_TYPE_AS_MASK(data->layers[i].type)) {
        number++;
      }
    }
  
    return number;
  }
  
  static void *customData_duplicate_referenced_layer_index(CustomData *data,
                                                           const int layer_index,
                                                           const int totelem)
  {
    if (layer_index == -1) {
      return NULL;
    }
  
    CustomDataLayer *layer = &data->layers[layer_index];
  
    if (layer->flag & CD_FLAG_NOFREE) {
      /* MEM_dupallocN won't work in case of complex layers, like e.g.
       * CD_MDEFORMVERT, which has pointers to allocated data...
       * So in case a custom copy function is defined, use it!
       */
      const LayerTypeInfo *typeInfo = layerType_getInfo(layer->type);
  
      if (typeInfo->copy) {
        void *dst_data = MEM_malloc_arrayN(
            (size_t)totelem, typeInfo->size, "CD duplicate ref layer");
        typeInfo->copy(layer->data, dst_data, totelem);
        layer->data = dst_data;
      }
      else {
        layer->data = MEM_dupallocN(layer->data);
      }
  
      layer->flag &= ~CD_FLAG_NOFREE;
    }
  
    return layer->data;
  }
  
  void *CustomData_duplicate_referenced_layer(CustomData *data, const int type, const int totelem)
  {
    /* get the layer index of the first layer of type */
    int layer_index = CustomData_get_active_layer_index(data, type);
  
    return customData_duplicate_referenced_layer_index(data, layer_index, totelem);
  }
  
  void *CustomData_duplicate_referenced_layer_n(CustomData *data,
                                                const int type,
                                                const int n,
                                                const int totelem)
  {
    /* get the layer index of the desired layer */
    int layer_index = CustomData_get_layer_index_n(data, type, n);
  
    return customData_duplicate_referenced_layer_index(data, layer_index, totelem);
  }
  
  void *CustomData_duplicate_referenced_layer_named(CustomData *data,
                                                    const int type,
                                                    const char *name,
                                                    const int totelem)
  {
    /* get the layer index of the desired layer */
    int layer_index = CustomData_get_named_layer_index(data, type, name);
  
    return customData_duplicate_referenced_layer_index(data, layer_index, totelem);
  }
  
  bool CustomData_is_referenced_layer(struct CustomData *data, int type)
  {
    /* get the layer index of the first layer of type */
    int layer_index = CustomData_get_active_layer_index(data, type);
    if (layer_index == -1) {
      return false;
    }
  
    CustomDataLayer *layer = &data->layers[layer_index];
  
    return (layer->flag & CD_FLAG_NOFREE) != 0;
  }
  
  void CustomData_free_temporary(CustomData *data, int totelem)
  {
    CustomDataLayer *layer;
    int i, j;
    bool changed = false;
  
    for (i = 0, j = 0; i < data->totlayer; i++) {
      layer = &data->layers[i];
  
      if (i != j) {
        data->layers[j] = data->layers[i];
      }
  
      if ((layer->flag & CD_FLAG_TEMPORARY) == CD_FLAG_TEMPORARY) {
        customData_free_layer__internal(layer, totelem);
        changed = true;
      }
      else {
        j++;
      }
    }
  
    data->totlayer = j;
  
    if (data->totlayer <= data->maxlayer - CUSTOMDATA_GROW) {
      customData_resize(data, -CUSTOMDATA_GROW);
      changed = true;
    }
  
    if (changed) {
      customData_update_offsets(data);
    }
  }
  
  void CustomData_set_only_copy(const struct CustomData *data, CustomDataMask mask)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (!(mask & CD_TYPE_AS_MASK(data->layers[i].type))) {
        data->layers[i].flag |= CD_FLAG_NOCOPY;
      }
    }
  }
  
  void CustomData_copy_elements(int type, void *src_data_ofs, void *dst_data_ofs, int count)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    if (typeInfo->copy) {
      typeInfo->copy(src_data_ofs, dst_data_ofs, count);
    }
    else {
      memcpy(dst_data_ofs, src_data_ofs, (size_t)count * typeInfo->size);
    }
  }
  
  static void CustomData_copy_data_layer(const CustomData *source,
                                         CustomData *dest,
                                         int src_i,
                                         int dst_i,
                                         int src_index,
                                         int dst_index,
                                         int count)
  {
    const LayerTypeInfo *typeInfo;
  
    const void *src_data = source->layers[src_i].data;
    void *dst_data = dest->layers[dst_i].data;
  
    typeInfo = layerType_getInfo(source->layers[src_i].type);
  
    const size_t src_offset = (size_t)src_index * typeInfo->size;
    const size_t dst_offset = (size_t)dst_index * typeInfo->size;
  
    if (!count || !src_data || !dst_data) {
      if (count && !(src_data == NULL && dst_data == NULL)) {
        CLOG_WARN(&LOG,
                  "null data for %s type (%p --> %p), skipping",
                  layerType_getName(source->layers[src_i].type),
                  (void *)src_data,
                  (void *)dst_data);
      }
      return;
    }
  
    if (typeInfo->copy) {
      typeInfo->copy(
          POINTER_OFFSET(src_data, src_offset), POINTER_OFFSET(dst_data, dst_offset), count);
    }
    else {
      memcpy(POINTER_OFFSET(dst_data, dst_offset),
             POINTER_OFFSET(src_data, src_offset),
             (size_t)count * typeInfo->size);
    }
  }
  
  void CustomData_copy_data_named(
      const CustomData *source, CustomData *dest, int source_index, int dest_index, int count)
  {
    /* copies a layer at a time */
    for (int src_i = 0; src_i < source->totlayer; src_i++) {
  
      int dest_i = CustomData_get_named_layer_index(
          dest, source->layers[src_i].type, source->layers[src_i].name);
  
      /* if we found a matching layer, copy the data */
      if (dest_i != -1) {
        CustomData_copy_data_layer(source, dest, src_i, dest_i, source_index, dest_index, count);
      }
    }
  }
  
  void CustomData_copy_data(
      const CustomData *source, CustomData *dest, int source_index, int dest_index, int count)
  {
    /* copies a layer at a time */
    int dest_i = 0;
    for (int src_i = 0; src_i < source->totlayer; src_i++) {
  
      /* find the first dest layer with type >= the source type
       * (this should work because layers are ordered by type)
       */
      while (dest_i < dest->totlayer && dest->layers[dest_i].type < source->layers[src_i].type) {
        dest_i++;
      }
  
      /* if there are no more dest layers, we're done */
      if (dest_i >= dest->totlayer) {
        return;
      }
  
      /* if we found a matching layer, copy the data */
      if (dest->layers[dest_i].type == source->layers[src_i].type) {
        CustomData_copy_data_layer(source, dest, src_i, dest_i, source_index, dest_index, count);
  
        /* if there are multiple source & dest layers of the same type,
         * we don't want to copy all source layers to the same dest, so
         * increment dest_i
         */
        dest_i++;
      }
    }
  }
  
  void CustomData_copy_layer_type_data(const CustomData *source,
                                       CustomData *destination,
                                       int type,
                                       int source_index,
                                       int destination_index,
                                       int count)
  {
    const int source_layer_index = CustomData_get_layer_index(source, type);
    if (source_layer_index == -1) {
      return;
    }
    const int destinaiton_layer_index = CustomData_get_layer_index(destination, type);
    if (destinaiton_layer_index == -1) {
      return;
    }
    CustomData_copy_data_layer(source,
                               destination,
                               source_layer_index,
                               destinaiton_layer_index,
                               source_index,
                               destination_index,
                               count);
  }
  
  void CustomData_free_elem(CustomData *data, int index, int count)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (!(data->layers[i].flag & CD_FLAG_NOFREE)) {
        const LayerTypeInfo *typeInfo = layerType_getInfo(data->layers[i].type);
  
        if (typeInfo->free) {
          size_t offset = (size_t)index * typeInfo->size;
  
          typeInfo->free(POINTER_OFFSET(data->layers[i].data, offset), count, typeInfo->size);
        }
      }
    }
  }
  
  #define SOURCE_BUF_SIZE 100
  
  /**
   * Interpolate given custom data source items into a single destination one.
   *
   * \param src_indices: Indices of every source items to interpolate into the destination one.
   * \param weights: The weight to apply to each source value individually. If NULL, they will be
   * averaged.
   * \param sub_weights: The weights of sub-items, only used to affect each corners of a
   * tessellated face data (should always be and array of four values).
   * \param count: The number of source items to interpolate.
   * \param dest_index: Index of the destination item, in which to put the result of the
   * interpolation.
   */
  void CustomData_interp(const CustomData *source,
                         CustomData *dest,
                         const int *src_indices,
                         const float *weights,
                         const float *sub_weights,
                         int count,
                         int dest_index)
  {
    if (count <= 0) {
      return;
    }
  
    const void *source_buf[SOURCE_BUF_SIZE];
    const void **sources = source_buf;
  
    /* Slow fallback in case we're interpolating a ridiculous number of elements. */
    if (count > SOURCE_BUF_SIZE) {
      sources = MEM_malloc_arrayN(count, sizeof(*sources), __func__);
    }
  
    /* If no weights are given, generate default ones to produce an average result. */
    float default_weights_buf[SOURCE_BUF_SIZE];
    float *default_weights = NULL;
    if (weights == NULL) {
      default_weights = (count > SOURCE_BUF_SIZE) ?
                            MEM_mallocN(sizeof(*weights) * (size_t)count, __func__) :
                            default_weights_buf;
      copy_vn_fl(default_weights, count, 1.0f / count);
      weights = default_weights;
    }
  
    /* interpolates a layer at a time */
    int dest_i = 0;
    for (int src_i = 0; src_i < source->totlayer; src_i++) {
      const LayerTypeInfo *typeInfo = layerType_getInfo(source->layers[src_i].type);
      if (!typeInfo->interp) {
        continue;
      }
  
      /* find the first dest layer with type >= the source type
       * (this should work because layers are ordered by type)
       */
      while (dest_i < dest->totlayer && dest->layers[dest_i].type < source->layers[src_i].type) {
        dest_i++;
      }
  
      /* if there are no more dest layers, we're done */
      if (dest_i >= dest->totlayer) {
        break;
      }
  
      /* if we found a matching layer, copy the data */
      if (dest->layers[dest_i].type == source->layers[src_i].type) {
        void *src_data = source->layers[src_i].data;
  
        for (int j = 0; j < count; j++) {
          sources[j] = POINTER_OFFSET(src_data, (size_t)src_indices[j] * typeInfo->size);
        }
  
        typeInfo->interp(
            sources,
            weights,
            sub_weights,
            count,
            POINTER_OFFSET(dest->layers[dest_i].data, (size_t)dest_index * typeInfo->size));
  
        /* if there are multiple source & dest layers of the same type,
         * we don't want to copy all source layers to the same dest, so
         * increment dest_i
         */
        dest_i++;
      }
    }
  
    if (count > SOURCE_BUF_SIZE) {
      MEM_freeN((void *)sources);
    }
    if (!ELEM(default_weights, NULL, default_weights_buf)) {
      MEM_freeN(default_weights);
    }
  }
  
  /**
   * Swap data inside each item, for all layers.
   * This only applies to item types that may store several sub-item data
   * (e.g. corner data [UVs, VCol, ...] of tessellated faces).
   *
   * \param corner_indices: A mapping 'new_index -> old_index' of sub-item data.
   */
  void CustomData_swap_corners(struct CustomData *data, int index, const int *corner_indices)
  {
    for (int i = 0; i < data->totlayer; i++) {
      const LayerTypeInfo *typeInfo = layerType_getInfo(data->layers[i].type);
  
      if (typeInfo->swap) {
        const size_t offset = (size_t)index * typeInfo->size;
  
        typeInfo->swap(POINTER_OFFSET(data->layers[i].data, offset), corner_indices);
      }
    }
  }
  
  /**
   * Swap two items of given custom data, in all available layers.
   */
  void CustomData_swap(struct CustomData *data, const int index_a, const int index_b)
  {
    char buff_static[256];
  
    if (index_a == index_b) {
      return;
    }
  
    for (int i = 0; i < data->totlayer; i++) {
      const LayerTypeInfo *typeInfo = layerType_getInfo(data->layers[i].type);
      const size_t size = typeInfo->size;
      const size_t offset_a = size * index_a;
      const size_t offset_b = size * index_b;
  
      void *buff = size <= sizeof(buff_static) ? buff_static : MEM_mallocN(size, __func__);
      memcpy(buff, POINTER_OFFSET(data->layers[i].data, offset_a), size);
      memcpy(POINTER_OFFSET(data->layers[i].data, offset_a),
             POINTER_OFFSET(data->layers[i].data, offset_b),
             size);
      memcpy(POINTER_OFFSET(data->layers[i].data, offset_b), buff, size);
  
      if (buff != buff_static) {
        MEM_freeN(buff);
      }
    }
  }
  
  void *CustomData_get(const CustomData *data, int index, int type)
  {
    BLI_assert(index >= 0);
  
    /* get the layer index of the active layer of type */
    int layer_index = CustomData_get_active_layer_index(data, type);
    if (layer_index == -1) {
      return NULL;
    }
  
    /* get the offset of the desired element */
    const size_t offset = (size_t)index * layerType_getInfo(type)->size;
  
    return POINTER_OFFSET(data->layers[layer_index].data, offset);
  }
  
  void *CustomData_get_n(const CustomData *data, int type, int index, int n)
  {
    BLI_assert(index >= 0 && n >= 0);
  
    /* get the layer index of the first layer of type */
    int layer_index = data->typemap[type];
    if (layer_index == -1) {
      return NULL;
    }
  
    const size_t offset = (size_t)index * layerType_getInfo(type)->size;
    return POINTER_OFFSET(data->layers[layer_index + n].data, offset);
  }
  
  void *CustomData_get_layer(const CustomData *data, int type)
  {
    /* get the layer index of the active layer of type */
    int layer_index = CustomData_get_active_layer_index(data, type);
    if (layer_index == -1) {
      return NULL;
    }
  
    return data->layers[layer_index].data;
  }
  
  void *CustomData_get_layer_n(const CustomData *data, int type, int n)
  {
    /* get the layer index of the active layer of type */
    int layer_index = CustomData_get_layer_index_n(data, type, n);
    if (layer_index == -1) {
      return NULL;
    }
  
    return data->layers[layer_index].data;
  }
  
  void *CustomData_get_layer_named(const struct CustomData *data, int type, const char *name)
  {
    int layer_index = CustomData_get_named_layer_index(data, type, name);
    if (layer_index == -1) {
      return NULL;
    }
  
    return data->layers[layer_index].data;
  }
  
  int CustomData_get_offset(const CustomData *data, int type)
  {
    /* get the layer index of the active layer of type */
    int layer_index = CustomData_get_active_layer_index(data, type);
    if (layer_index == -1) {
      return -1;
    }
  
    return data->layers[layer_index].offset;
  }
  
  int CustomData_get_n_offset(const CustomData *data, int type, int n)
  {
    /* get the layer index of the active layer of type */
    int layer_index = CustomData_get_layer_index_n(data, type, n);
    if (layer_index == -1) {
      return -1;
    }
  
    return data->layers[layer_index].offset;
  }
  
  bool CustomData_set_layer_name(const CustomData *data, int type, int n, const char *name)
  {
    /* get the layer index of the first layer of type */
    const int layer_index = CustomData_get_layer_index_n(data, type, n);
  
    if ((layer_index == -1) || !name) {
      return false;
    }
  
    BLI_strncpy(data->layers[layer_index].name, name, sizeof(data->layers[layer_index].name));
  
    return true;
  }
  
  const char *CustomData_get_layer_name(const CustomData *data, int type, int n)
  {
    const int layer_index = CustomData_get_layer_index_n(data, type, n);
  
    return (layer_index == -1) ? NULL : data->layers[layer_index].name;
  }
  
  void *CustomData_set_layer(const CustomData *data, int type, void *ptr)
  {
    /* get the layer index of the first layer of type */
    int layer_index = CustomData_get_active_layer_index(data, type);
  
    if (layer_index == -1) {
      return NULL;
    }
  
    data->layers[layer_index].data = ptr;
  
    return ptr;
  }
  
  void *CustomData_set_layer_n(const struct CustomData *data, int type, int n, void *ptr)
  {
    /* get the layer index of the first layer of type */
    int layer_index = CustomData_get_layer_index_n(data, type, n);
    if (layer_index == -1) {
      return NULL;
    }
  
    data->layers[layer_index].data = ptr;
  
    return ptr;
  }
  
  void CustomData_set(const CustomData *data, int index, int type, const void *source)
  {
    void *dest = CustomData_get(data, index, type);
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    if (!dest) {
      return;
    }
  
    if (typeInfo->copy) {
      typeInfo->copy(source, dest, 1);
    }
    else {
      memcpy(dest, source, typeInfo->size);
    }
  }
  
  /* BMesh functions */
  /* needed to convert to/from different face reps */
  void CustomData_to_bmeshpoly(CustomData *fdata, CustomData *ldata, int totloop)
  {
    for (int i = 0; i < fdata->totlayer; i++) {
      if (fdata->layers[i].type == CD_MTFACE) {
        CustomData_add_layer_named(
            ldata, CD_MLOOPUV, CD_CALLOC, NULL, totloop, fdata->layers[i].name);
      }
      else if (fdata->layers[i].type == CD_MCOL) {
        CustomData_add_layer_named(
            ldata, CD_MLOOPCOL, CD_CALLOC, NULL, totloop, fdata->layers[i].name);
      }
      else if (fdata->layers[i].type == CD_MDISPS) {
        CustomData_add_layer_named(
            ldata, CD_MDISPS, CD_CALLOC, NULL, totloop, fdata->layers[i].name);
      }
      else if (fdata->layers[i].type == CD_TESSLOOPNORMAL) {
        CustomData_add_layer_named(
            ldata, CD_NORMAL, CD_CALLOC, NULL, totloop, fdata->layers[i].name);
      }
    }
  }
  
  void CustomData_from_bmeshpoly(CustomData *fdata, CustomData *ldata, int total)
  {
    /* avoid accumulating extra layers */
    BLI_assert(!CustomData_from_bmeshpoly_test(fdata, ldata, false));
  
    for (int i = 0; i < ldata->totlayer; i++) {
      if (ldata->layers[i].type == CD_MLOOPUV) {
        CustomData_add_layer_named(fdata, CD_MTFACE, CD_CALLOC, NULL, total, ldata->layers[i].name);
      }
      if (ldata->layers[i].type == CD_MLOOPCOL) {
        CustomData_add_layer_named(fdata, CD_MCOL, CD_CALLOC, NULL, total, ldata->layers[i].name);
      }
      else if (ldata->layers[i].type == CD_PREVIEW_MLOOPCOL) {
        CustomData_add_layer_named(
            fdata, CD_PREVIEW_MCOL, CD_CALLOC, NULL, total, ldata->layers[i].name);
      }
      else if (ldata->layers[i].type == CD_ORIGSPACE_MLOOP) {
        CustomData_add_layer_named(
            fdata, CD_ORIGSPACE, CD_CALLOC, NULL, total, ldata->layers[i].name);
      }
      else if (ldata->layers[i].type == CD_NORMAL) {
        CustomData_add_layer_named(
            fdata, CD_TESSLOOPNORMAL, CD_CALLOC, NULL, total, ldata->layers[i].name);
      }
      else if (ldata->layers[i].type == CD_TANGENT) {
        CustomData_add_layer_named(fdata, CD_TANGENT, CD_CALLOC, NULL, total, ldata->layers[i].name);
      }
    }
  
    CustomData_bmesh_update_active_layers(fdata, ldata);
  }
  
  #ifndef NDEBUG
  /**
   * Debug check, used to assert when we expect layers to be in/out of sync.
   *
   * \param fallback: Use when there are no layers to handle,
   * since callers may expect success or failure.
   */
  bool CustomData_from_bmeshpoly_test(CustomData *fdata, CustomData *ldata, bool fallback)
  {
    int a_num = 0, b_num = 0;
  #  define LAYER_CMP(l_a, t_a, l_b, t_b) \
      ((a_num += CustomData_number_of_layers(l_a, t_a)) == \
       (b_num += CustomData_number_of_layers(l_b, t_b)))
  
    if (!LAYER_CMP(ldata, CD_MLOOPUV, fdata, CD_MTFACE)) {
      return false;
    }
    if (!LAYER_CMP(ldata, CD_MLOOPCOL, fdata, CD_MCOL)) {
      return false;
    }
    if (!LAYER_CMP(ldata, CD_PREVIEW_MLOOPCOL, fdata, CD_PREVIEW_MCOL)) {
      return false;
    }
    if (!LAYER_CMP(ldata, CD_ORIGSPACE_MLOOP, fdata, CD_ORIGSPACE)) {
      return false;
    }
    if (!LAYER_CMP(ldata, CD_NORMAL, fdata, CD_TESSLOOPNORMAL)) {
      return false;
    }
    if (!LAYER_CMP(ldata, CD_TANGENT, fdata, CD_TANGENT)) {
      return false;
    }
  
  #  undef LAYER_CMP
  
    /* if no layers are on either CustomData's,
     * then there was nothing to do... */
    return a_num ? true : fallback;
  }
  #endif
  
  void CustomData_bmesh_update_active_layers(CustomData *fdata, CustomData *ldata)
  {
    int act;
  
    if (CustomData_has_layer(ldata, CD_MLOOPUV)) {
      act = CustomData_get_active_layer(ldata, CD_MLOOPUV);
      CustomData_set_layer_active(fdata, CD_MTFACE, act);
  
      act = CustomData_get_render_layer(ldata, CD_MLOOPUV);
      CustomData_set_layer_render(fdata, CD_MTFACE, act);
  
      act = CustomData_get_clone_layer(ldata, CD_MLOOPUV);
      CustomData_set_layer_clone(fdata, CD_MTFACE, act);
  
      act = CustomData_get_stencil_layer(ldata, CD_MLOOPUV);
      CustomData_set_layer_stencil(fdata, CD_MTFACE, act);
    }
  
    if (CustomData_has_layer(ldata, CD_MLOOPCOL)) {
      act = CustomData_get_active_layer(ldata, CD_MLOOPCOL);
      CustomData_set_layer_active(fdata, CD_MCOL, act);
  
      act = CustomData_get_render_layer(ldata, CD_MLOOPCOL);
      CustomData_set_layer_render(fdata, CD_MCOL, act);
  
      act = CustomData_get_clone_layer(ldata, CD_MLOOPCOL);
      CustomData_set_layer_clone(fdata, CD_MCOL, act);
  
      act = CustomData_get_stencil_layer(ldata, CD_MLOOPCOL);
      CustomData_set_layer_stencil(fdata, CD_MCOL, act);
    }
  }
  
  /* update active indices for active/render/clone/stencil custom data layers
   * based on indices from fdata layers
   * used by do_versions in readfile.c when creating pdata and ldata for pre-bmesh
   * meshes and needed to preserve active/render/clone/stencil flags set in pre-bmesh files
   */
  void CustomData_bmesh_do_versions_update_active_layers(CustomData *fdata, CustomData *ldata)
  {
    int act;
  
    if (CustomData_has_layer(fdata, CD_MTFACE)) {
      act = CustomData_get_active_layer(fdata, CD_MTFACE);
      CustomData_set_layer_active(ldata, CD_MLOOPUV, act);
  
      act = CustomData_get_render_layer(fdata, CD_MTFACE);
      CustomData_set_layer_render(ldata, CD_MLOOPUV, act);
  
      act = CustomData_get_clone_layer(fdata, CD_MTFACE);
      CustomData_set_layer_clone(ldata, CD_MLOOPUV, act);
  
      act = CustomData_get_stencil_layer(fdata, CD_MTFACE);
      CustomData_set_layer_stencil(ldata, CD_MLOOPUV, act);
    }
  
    if (CustomData_has_layer(fdata, CD_MCOL)) {
      act = CustomData_get_active_layer(fdata, CD_MCOL);
      CustomData_set_layer_active(ldata, CD_MLOOPCOL, act);
  
      act = CustomData_get_render_layer(fdata, CD_MCOL);
      CustomData_set_layer_render(ldata, CD_MLOOPCOL, act);
  
      act = CustomData_get_clone_layer(fdata, CD_MCOL);
      CustomData_set_layer_clone(ldata, CD_MLOOPCOL, act);
  
      act = CustomData_get_stencil_layer(fdata, CD_MCOL);
      CustomData_set_layer_stencil(ldata, CD_MLOOPCOL, act);
    }
  }
  
  void CustomData_bmesh_init_pool(CustomData *data, int totelem, const char htype)
  {
    int chunksize;
  
    /* Dispose old pools before calling here to avoid leaks */
    BLI_assert(data->pool == NULL);
  
    switch (htype) {
      case BM_VERT:
        chunksize = bm_mesh_chunksize_default.totvert;
        break;
      case BM_EDGE:
        chunksize = bm_mesh_chunksize_default.totedge;
        break;
      case BM_LOOP:
        chunksize = bm_mesh_chunksize_default.totloop;
        break;
      case BM_FACE:
        chunksize = bm_mesh_chunksize_default.totface;
        break;
      default:
        BLI_assert(0);
        chunksize = 512;
        break;
    }
  
    /* If there are no layers, no pool is needed just yet */
    if (data->totlayer) {
      data->pool = BLI_mempool_create(data->totsize, totelem, chunksize, BLI_MEMPOOL_NOP);
    }
  }
  
  bool CustomData_bmesh_merge(const CustomData *source,
                              CustomData *dest,
                              CustomDataMask mask,
                              eCDAllocType alloctype,
                              BMesh *bm,
                              const char htype)
  {
  
    if (CustomData_number_of_layers_typemask(source, mask) == 0) {
      return false;
    }
  
    /* copy old layer description so that old data can be copied into
     * the new allocation */
    CustomData destold = *dest;
    if (destold.layers) {
      destold.layers = MEM_dupallocN(destold.layers);
    }
  
    if (CustomData_merge(source, dest, mask, alloctype, 0) == false) {
      if (destold.layers) {
        MEM_freeN(destold.layers);
      }
      return false;
    }
  
    int iter_type;
    int totelem;
    switch (htype) {
      case BM_VERT:
        iter_type = BM_VERTS_OF_MESH;
        totelem = bm->totvert;
        break;
      case BM_EDGE:
        iter_type = BM_EDGES_OF_MESH;
        totelem = bm->totedge;
        break;
      case BM_LOOP:
        iter_type = BM_LOOPS_OF_FACE;
        totelem = bm->totloop;
        break;
      case BM_FACE:
        iter_type = BM_FACES_OF_MESH;
        totelem = bm->totface;
        break;
      default: /* should never happen */
        BLI_assert(!"invalid type given");
        iter_type = BM_VERTS_OF_MESH;
        totelem = bm->totvert;
        break;
    }
  
    dest->pool = NULL;
    CustomData_bmesh_init_pool(dest, totelem, htype);
  
    if (iter_type != BM_LOOPS_OF_FACE) {
      BMHeader *h;
      BMIter iter;
      /*ensure all current elements follow new customdata layout*/
      BM_ITER_MESH (h, &iter, bm, iter_type) {
        void *tmp = NULL;
        CustomData_bmesh_copy_data(&destold, dest, h->data, &tmp);
        CustomData_bmesh_free_block(&destold, &h->data);
        h->data = tmp;
      }
    }
    else {
      BMFace *f;
      BMLoop *l;
      BMIter iter;
      BMIter liter;
  
      /*ensure all current elements follow new customdata layout*/
      BM_ITER_MESH (f, &iter, bm, BM_FACES_OF_MESH) {
        BM_ITER_ELEM (l, &liter, f, BM_LOOPS_OF_FACE) {
          void *tmp = NULL;
          CustomData_bmesh_copy_data(&destold, dest, l->head.data, &tmp);
          CustomData_bmesh_free_block(&destold, &l->head.data);
          l->head.data = tmp;
        }
      }
    }
  
    if (destold.pool) {
      BLI_mempool_destroy(destold.pool);
    }
    if (destold.layers) {
      MEM_freeN(destold.layers);
    }
    return true;
  }
  
  void CustomData_bmesh_free_block(CustomData *data, void **block)
  {
    if (*block == NULL) {
      return;
    }
  
    for (int i = 0; i < data->totlayer; i++) {
      if (!(data->layers[i].flag & CD_FLAG_NOFREE)) {
        const LayerTypeInfo *typeInfo = layerType_getInfo(data->layers[i].type);
  
        if (typeInfo->free) {
          int offset = data->layers[i].offset;
          typeInfo->free(POINTER_OFFSET(*block, offset), 1, typeInfo->size);
        }
      }
    }
  
    if (data->totsize) {
      BLI_mempool_free(data->pool, *block);
    }
  
    *block = NULL;
  }
  
  /**
   * Same as #CustomData_bmesh_free_block but zero the memory rather than freeing.
   */
  void CustomData_bmesh_free_block_data(CustomData *data, void *block)
  {
    if (block == NULL) {
      return;
    }
    for (int i = 0; i < data->totlayer; i++) {
      if (!(data->layers[i].flag & CD_FLAG_NOFREE)) {
        const LayerTypeInfo *typeInfo = layerType_getInfo(data->layers[i].type);
        if (typeInfo->free) {
          const size_t offset = data->layers[i].offset;
          typeInfo->free(POINTER_OFFSET(block, offset), 1, typeInfo->size);
        }
      }
    }
    if (data->totsize) {
      memset(block, 0, data->totsize);
    }
  }
  
  static void CustomData_bmesh_alloc_block(CustomData *data, void **block)
  {
    if (*block) {
      CustomData_bmesh_free_block(data, block);
    }
  
    if (data->totsize > 0) {
      *block = BLI_mempool_alloc(data->pool);
    }
    else {
      *block = NULL;
    }
  }
  
  /**
   * A selective version of #CustomData_bmesh_free_block_data.
   */
  void CustomData_bmesh_free_block_data_exclude_by_type(CustomData *data,
                                                        void *block,
                                                        const CustomDataMask mask_exclude)
  {
    if (block == NULL) {
      return;
    }
    for (int i = 0; i < data->totlayer; i++) {
      if ((CD_TYPE_AS_MASK(data->layers[i].type) & mask_exclude) == 0) {
        const LayerTypeInfo *typeInfo = layerType_getInfo(data->layers[i].type);
        const size_t offset = data->layers[i].offset;
        if (!(data->layers[i].flag & CD_FLAG_NOFREE)) {
          if (typeInfo->free) {
            typeInfo->free(POINTER_OFFSET(block, offset), 1, typeInfo->size);
          }
        }
        memset(POINTER_OFFSET(block, offset), 0, typeInfo->size);
      }
    }
  }
  
  static void CustomData_bmesh_set_default_n(CustomData *data, void **block, int n)
  {
    const LayerTypeInfo *typeInfo;
    int offset = data->layers[n].offset;
  
    typeInfo = layerType_getInfo(data->layers[n].type);
  
    if (typeInfo->set_default) {
      typeInfo->set_default(POINTER_OFFSET(*block, offset), 1);
    }
    else {
      memset(POINTER_OFFSET(*block, offset), 0, typeInfo->size);
    }
  }
  
  void CustomData_bmesh_set_default(CustomData *data, void **block)
  {
    if (*block == NULL) {
      CustomData_bmesh_alloc_block(data, block);
    }
  
    for (int i = 0; i < data->totlayer; i++) {
      CustomData_bmesh_set_default_n(data, block, i);
    }
  }
  
  void CustomData_bmesh_copy_data_exclude_by_type(const CustomData *source,
                                                  CustomData *dest,
                                                  void *src_block,
                                                  void **dest_block,
                                                  const CustomDataMask mask_exclude)
  {
    /* Note that having a version of this function without a 'mask_exclude'
     * would cause too much duplicate code, so add a check instead. */
    const bool no_mask = (mask_exclude == 0);
  
    if (*dest_block == NULL) {
      CustomData_bmesh_alloc_block(dest, dest_block);
      if (*dest_block) {
        memset(*dest_block, 0, dest->totsize);
      }
    }
  
    /* copies a layer at a time */
    int dest_i = 0;
    for (int src_i = 0; src_i < source->totlayer; src_i++) {
  
      /* find the first dest layer with type >= the source type
       * (this should work because layers are ordered by type)
       */
      while (dest_i < dest->totlayer && dest->layers[dest_i].type < source->layers[src_i].type) {
        CustomData_bmesh_set_default_n(dest, dest_block, dest_i);
        dest_i++;
      }
  
      /* if there are no more dest layers, we're done */
      if (dest_i >= dest->totlayer) {
        return;
      }
  
      /* if we found a matching layer, copy the data */
      if (dest->layers[dest_i].type == source->layers[src_i].type &&
          STREQ(dest->layers[dest_i].name, source->layers[src_i].name)) {
        if (no_mask || ((CD_TYPE_AS_MASK(dest->layers[dest_i].type) & mask_exclude) == 0)) {
          const void *src_data = POINTER_OFFSET(src_block, source->layers[src_i].offset);
          void *dest_data = POINTER_OFFSET(*dest_block, dest->layers[dest_i].offset);
          const LayerTypeInfo *typeInfo = layerType_getInfo(source->layers[src_i].type);
          if (typeInfo->copy) {
            typeInfo->copy(src_data, dest_data, 1);
          }
          else {
            memcpy(dest_data, src_data, typeInfo->size);
          }
        }
  
        /* if there are multiple source & dest layers of the same type,
         * we don't want to copy all source layers to the same dest, so
         * increment dest_i
         */
        dest_i++;
      }
    }
  
    while (dest_i < dest->totlayer) {
      CustomData_bmesh_set_default_n(dest, dest_block, dest_i);
      dest_i++;
    }
  }
  
  void CustomData_bmesh_copy_data(const CustomData *source,
                                  CustomData *dest,
                                  void *src_block,
                                  void **dest_block)
  {
    CustomData_bmesh_copy_data_exclude_by_type(source, dest, src_block, dest_block, 0);
  }
  
  /* BMesh Custom Data Functions.
   * Should replace edit-mesh ones with these as well, due to more efficient memory alloc.
   */
  void *CustomData_bmesh_get(const CustomData *data, void *block, int type)
  {
    /* get the layer index of the first layer of type */
    int layer_index = CustomData_get_active_layer_index(data, type);
    if (layer_index == -1) {
      return NULL;
    }
  
    return POINTER_OFFSET(block, data->layers[layer_index].offset);
  }
  
  void *CustomData_bmesh_get_n(const CustomData *data, void *block, int type, int n)
  {
    /* get the layer index of the first layer of type */
    int layer_index = CustomData_get_layer_index(data, type);
    if (layer_index == -1) {
      return NULL;
    }
  
    return POINTER_OFFSET(block, data->layers[layer_index + n].offset);
  }
  
  /*gets from the layer at physical index n, note: doesn't check type.*/
  void *CustomData_bmesh_get_layer_n(const CustomData *data, void *block, int n)
  {
    if (n < 0 || n >= data->totlayer) {
      return NULL;
    }
  
    return POINTER_OFFSET(block, data->layers[n].offset);
  }
  
  bool CustomData_layer_has_math(const struct CustomData *data, int layer_n)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(data->layers[layer_n].type);
  
    if (typeInfo->equal && typeInfo->add && typeInfo->multiply && typeInfo->initminmax &&
        typeInfo->dominmax) {
      return true;
    }
  
    return false;
  }
  
  bool CustomData_layer_has_interp(const struct CustomData *data, int layer_n)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(data->layers[layer_n].type);
  
    if (typeInfo->interp) {
      return true;
    }
  
    return false;
  }
  
  bool CustomData_has_math(const struct CustomData *data)
  {
    /* interpolates a layer at a time */
    for (int i = 0; i < data->totlayer; i++) {
      if (CustomData_layer_has_math(data, i)) {
        return true;
      }
    }
  
    return false;
  }
  
  /* a non bmesh version would have to check layer->data */
  bool CustomData_bmesh_has_free(const struct CustomData *data)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (!(data->layers[i].flag & CD_FLAG_NOFREE)) {
        const LayerTypeInfo *typeInfo = layerType_getInfo(data->layers[i].type);
        if (typeInfo->free) {
          return true;
        }
      }
    }
    return false;
  }
  
  bool CustomData_has_interp(const struct CustomData *data)
  {
    /* interpolates a layer at a time */
    for (int i = 0; i < data->totlayer; i++) {
      if (CustomData_layer_has_interp(data, i)) {
        return true;
      }
    }
  
    return false;
  }
  
  bool CustomData_has_referenced(const struct CustomData *data)
  {
    for (int i = 0; i < data->totlayer; i++) {
      if (data->layers[i].flag & CD_FLAG_NOFREE) {
        return true;
      }
    }
    return false;
  }
  
  /* copies the "value" (e.g. mloopuv uv or mloopcol colors) from one block to
   * another, while not overwriting anything else (e.g. flags)*/
  void CustomData_data_copy_value(int type, const void *source, void *dest)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    if (!dest) {
      return;
    }
  
    if (typeInfo->copyvalue) {
      typeInfo->copyvalue(source, dest, CDT_MIX_NOMIX, 0.0f);
    }
    else {
      memcpy(dest, source, typeInfo->size);
    }
  }
  
  /* Mixes the "value" (e.g. mloopuv uv or mloopcol colors) from one block into
   * another, while not overwriting anything else (e.g. flags)*/
  void CustomData_data_mix_value(
      int type, const void *source, void *dest, const int mixmode, const float mixfactor)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    if (!dest) {
      return;
    }
  
    if (typeInfo->copyvalue) {
      typeInfo->copyvalue(source, dest, mixmode, mixfactor);
    }
    else {
      /* Mere copy if no advanced interpolation is supported. */
      memcpy(dest, source, typeInfo->size);
    }
  }
  
  bool CustomData_data_equals(int type, const void *data1, const void *data2)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    if (typeInfo->equal) {
      return typeInfo->equal(data1, data2);
    }
  
    return !memcmp(data1, data2, typeInfo->size);
  }
  
  void CustomData_data_initminmax(int type, void *min, void *max)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    if (typeInfo->initminmax) {
      typeInfo->initminmax(min, max);
    }
  }
  
  void CustomData_data_dominmax(int type, const void *data, void *min, void *max)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    if (typeInfo->dominmax) {
      typeInfo->dominmax(data, min, max);
    }
  }
  
  void CustomData_data_multiply(int type, void *data, float fac)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    if (typeInfo->multiply) {
      typeInfo->multiply(data, fac);
    }
  }
  
  void CustomData_data_add(int type, void *data1, const void *data2)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    if (typeInfo->add) {
      typeInfo->add(data1, data2);
    }
  }
  
  void CustomData_bmesh_set(const CustomData *data, void *block, int type, const void *source)
  {
    void *dest = CustomData_bmesh_get(data, block, type);
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    if (!dest) {
      return;
    }
  
    if (typeInfo->copy) {
      typeInfo->copy(source, dest, 1);
    }
    else {
      memcpy(dest, source, typeInfo->size);
    }
  }
  
  void CustomData_bmesh_set_n(CustomData *data, void *block, int type, int n, const void *source)
  {
    void *dest = CustomData_bmesh_get_n(data, block, type, n);
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    if (!dest) {
      return;
    }
  
    if (typeInfo->copy) {
      typeInfo->copy(source, dest, 1);
    }
    else {
      memcpy(dest, source, typeInfo->size);
    }
  }
  
  void CustomData_bmesh_set_layer_n(CustomData *data, void *block, int n, const void *source)
  {
    void *dest = CustomData_bmesh_get_layer_n(data, block, n);
    const LayerTypeInfo *typeInfo = layerType_getInfo(data->layers[n].type);
  
    if (!dest) {
      return;
    }
  
    if (typeInfo->copy) {
      typeInfo->copy(source, dest, 1);
    }
    else {
      memcpy(dest, source, typeInfo->size);
    }
  }
  
  /**
   * \note src_blocks_ofs & dst_block_ofs
   * must be pointers to the data, offset by layer->offset already.
   */
  void CustomData_bmesh_interp_n(CustomData *data,
                                 const void **src_blocks_ofs,
                                 const float *weights,
                                 const float *sub_weights,
                                 int count,
                                 void *dst_block_ofs,
                                 int n)
  {
    BLI_assert(weights != NULL);
    BLI_assert(count > 0);
  
    CustomDataLayer *layer = &data->layers[n];
    const LayerTypeInfo *typeInfo = layerType_getInfo(layer->type);
  
    typeInfo->interp(src_blocks_ofs, weights, sub_weights, count, dst_block_ofs);
  }
  
  void CustomData_bmesh_interp(CustomData *data,
                               const void **src_blocks,
                               const float *weights,
                               const float *sub_weights,
                               int count,
                               void *dst_block)
  {
    if (count <= 0) {
      return;
    }
  
    int i, j;
    void *source_buf[SOURCE_BUF_SIZE];
    const void **sources = (const void **)source_buf;
  
    /* Slow fallback in case we're interpolating a ridiculous number of elements. */
    if (count > SOURCE_BUF_SIZE) {
      sources = MEM_malloc_arrayN(count, sizeof(*sources), __func__);
    }
  
    /* If no weights are given, generate default ones to produce an average result. */
    float default_weights_buf[SOURCE_BUF_SIZE];
    float *default_weights = NULL;
    if (weights == NULL) {
      default_weights = (count > SOURCE_BUF_SIZE) ?
                            MEM_mallocN(sizeof(*weights) * (size_t)count, __func__) :
                            default_weights_buf;
      copy_vn_fl(default_weights, count, 1.0f / count);
      weights = default_weights;
    }
  
    /* interpolates a layer at a time */
    for (i = 0; i < data->totlayer; i++) {
      CustomDataLayer *layer = &data->layers[i];
      const LayerTypeInfo *typeInfo = layerType_getInfo(layer->type);
      if (typeInfo->interp) {
        for (j = 0; j < count; j++) {
          sources[j] = POINTER_OFFSET(src_blocks[j], layer->offset);
        }
        CustomData_bmesh_interp_n(
            data, sources, weights, sub_weights, count, POINTER_OFFSET(dst_block, layer->offset), i);
      }
    }
  
    if (count > SOURCE_BUF_SIZE) {
      MEM_freeN((void *)sources);
    }
    if (!ELEM(default_weights, NULL, default_weights_buf)) {
      MEM_freeN(default_weights);
    }
  }
  
  /**
   * \param use_default_init: initializes data which can't be copied,
   * typically you'll want to use this if the BM_xxx create function
   * is called with BM_CREATE_SKIP_CD flag
   */
  void CustomData_to_bmesh_block(const CustomData *source,
                                 CustomData *dest,
                                 int src_index,
                                 void **dest_block,
                                 bool use_default_init)
  {
    if (*dest_block == NULL) {
      CustomData_bmesh_alloc_block(dest, dest_block);
    }
  
    /* copies a layer at a time */
    int dest_i = 0;
    for (int src_i = 0; src_i < source->totlayer; src_i++) {
  
      /* find the first dest layer with type >= the source type
       * (this should work because layers are ordered by type)
       */
      while (dest_i < dest->totlayer && dest->layers[dest_i].type < source->layers[src_i].type) {
        if (use_default_init) {
          CustomData_bmesh_set_default_n(dest, dest_block, dest_i);
        }
        dest_i++;
      }
  
      /* if there are no more dest layers, we're done */
      if (dest_i >= dest->totlayer) {
        break;
      }
  
      /* if we found a matching layer, copy the data */
      if (dest->layers[dest_i].type == source->layers[src_i].type) {
        int offset = dest->layers[dest_i].offset;
        const void *src_data = source->layers[src_i].data;
        void *dest_data = POINTER_OFFSET(*dest_block, offset);
  
        const LayerTypeInfo *typeInfo = layerType_getInfo(dest->layers[dest_i].type);
        const size_t src_offset = (size_t)src_index * typeInfo->size;
  
        if (typeInfo->copy) {
          typeInfo->copy(POINTER_OFFSET(src_data, src_offset), dest_data, 1);
        }
        else {
          memcpy(dest_data, POINTER_OFFSET(src_data, src_offset), typeInfo->size);
        }
  
        /* if there are multiple source & dest layers of the same type,
         * we don't want to copy all source layers to the same dest, so
         * increment dest_i
         */
        dest_i++;
      }
    }
  
    if (use_default_init) {
      while (dest_i < dest->totlayer) {
        CustomData_bmesh_set_default_n(dest, dest_block, dest_i);
        dest_i++;
      }
    }
  }
  
  void CustomData_from_bmesh_block(const CustomData *source,
                                   CustomData *dest,
                                   void *src_block,
                                   int dest_index)
  {
    /* copies a layer at a time */
    int dest_i = 0;
    for (int src_i = 0; src_i < source->totlayer; src_i++) {
  
      /* find the first dest layer with type >= the source type
       * (this should work because layers are ordered by type)
       */
      while (dest_i < dest->totlayer && dest->layers[dest_i].type < source->layers[src_i].type) {
        dest_i++;
      }
  
      /* if there are no more dest layers, we're done */
      if (dest_i >= dest->totlayer) {
        return;
      }
  
      /* if we found a matching layer, copy the data */
      if (dest->layers[dest_i].type == source->layers[src_i].type) {
        const LayerTypeInfo *typeInfo = layerType_getInfo(dest->layers[dest_i].type);
        int offset = source->layers[src_i].offset;
        const void *src_data = POINTER_OFFSET(src_block, offset);
        void *dst_data = POINTER_OFFSET(dest->layers[dest_i].data,
                                        (size_t)dest_index * typeInfo->size);
  
        if (typeInfo->copy) {
          typeInfo->copy(src_data, dst_data, 1);
        }
        else {
          memcpy(dst_data, src_data, typeInfo->size);
        }
  
        /* if there are multiple source & dest layers of the same type,
         * we don't want to copy all source layers to the same dest, so
         * increment dest_i
         */
        dest_i++;
      }
    }
  }
  
  void CustomData_file_write_info(int type, const char **r_struct_name, int *r_struct_num)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    *r_struct_name = typeInfo->structname;
    *r_struct_num = typeInfo->structnum;
  }
  
  /**
   * Prepare given custom data for file writing.
   *
   * \param data: the customdata to tweak for .blend file writing (modified in place).
   * \param r_write_layers: contains a reduced set of layers to be written to file,
   * use it with writestruct_at_address()
   * (caller must free it if != \a write_layers_buff).
   *
   * \param write_layers_buff: an optional buffer for r_write_layers (to avoid allocating it).
   * \param write_layers_size: the size of pre-allocated \a write_layer_buff.
   *
   * \warning After this func has ran, given custom data is no more valid from Blender PoV
   * (its totlayer is invalid). This func shall always be called with localized data
   * (as it is in write_meshes()).
   *
   * \note data->typemap is not updated here, since it is always rebuilt on file read anyway.
   * This means written typemap does not match written layers (as returned by \a r_write_layers).
   * Trivial to fix is ever needed.
   */
  void CustomData_blend_write_prepare(CustomData *data,
                                      CustomDataLayer **r_write_layers,
                                      CustomDataLayer *write_layers_buff,
                                      size_t write_layers_size)
  {
    CustomDataLayer *write_layers = write_layers_buff;
    const size_t chunk_size = (write_layers_size > 0) ? write_layers_size : CD_TEMP_CHUNK_SIZE;
  
    const int totlayer = data->totlayer;
    int i, j;
  
    for (i = 0, j = 0; i < totlayer; i++) {
      CustomDataLayer *layer = &data->layers[i];
      if (layer->flag & CD_FLAG_NOCOPY) { /* Layers with this flag set are not written to file. */
        data->totlayer--;
        /* CLOG_WARN(&LOG, "skipping layer %p (%s)", layer, layer->name); */
      }
      else {
        if (UNLIKELY((size_t)j >= write_layers_size)) {
          if (write_layers == write_layers_buff) {
            write_layers = MEM_malloc_arrayN(
                (write_layers_size + chunk_size), sizeof(*write_layers), __func__);
            if (write_layers_buff) {
              memcpy(write_layers, write_layers_buff, sizeof(*write_layers) * write_layers_size);
            }
          }
          else {
            write_layers = MEM_reallocN(write_layers,
                                        sizeof(*write_layers) * (write_layers_size + chunk_size));
          }
          write_layers_size += chunk_size;
        }
        write_layers[j++] = *layer;
      }
    }
    BLI_assert(j == data->totlayer);
    data->maxlayer = data->totlayer; /* We only write that much of data! */
    *r_write_layers = write_layers;
  }
  
  int CustomData_sizeof(int type)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    return typeInfo->size;
  }
  
  const char *CustomData_layertype_name(int type)
  {
    return layerType_getName(type);
  }
  
  /**
   * Can only ever be one of these.
   */
  bool CustomData_layertype_is_singleton(int type)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
    return typeInfo->defaultname == NULL;
  }
  
  /**
   * \return Maximum number of layers of given \a type, -1 means 'no limit'.
   */
  int CustomData_layertype_layers_max(const int type)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(type);
  
    /* Same test as for singleton above. */
    if (typeInfo->defaultname == NULL) {
      return 1;
    }
    if (typeInfo->layers_max == NULL) {
      return -1;
    }
  
    return typeInfo->layers_max();
  }
  
  static bool cd_layer_find_dupe(CustomData *data, const char *name, int type, int index)
  {
    /* see if there is a duplicate */
    for (int i = 0; i < data->totlayer; i++) {
      if (i != index) {
        CustomDataLayer *layer = &data->layers[i];
  
        if (CD_TYPE_AS_MASK(type) & CD_MASK_PROP_ALL) {
          if ((CD_TYPE_AS_MASK(layer->type) & CD_MASK_PROP_ALL) && STREQ(layer->name, name)) {
            return true;
          }
        }
        else {
          if (i != index && layer->type == type && STREQ(layer->name, name)) {
            return true;
          }
        }
      }
    }
  
    return false;
  }
  
  static bool customdata_unique_check(void *arg, const char *name)
  {
    struct {
      CustomData *data;
      int type;
      int index;
    } *data_arg = arg;
    return cd_layer_find_dupe(data_arg->data, name, data_arg->type, data_arg->index);
  }
  
  void CustomData_set_layer_unique_name(CustomData *data, int index)
  {
    CustomDataLayer *nlayer = &data->layers[index];
    const LayerTypeInfo *typeInfo = layerType_getInfo(nlayer->type);
  
    struct {
      CustomData *data;
      int type;
      int index;
    } data_arg;
    data_arg.data = data;
    data_arg.type = nlayer->type;
    data_arg.index = index;
  
    if (!typeInfo->defaultname) {
      return;
    }
  
    /* Set default name if none specified. Note we only call DATA_() when
     * needed to avoid overhead of locale lookups in the depsgraph. */
    if (nlayer->name[0] == '\0') {
      STRNCPY(nlayer->name, DATA_(typeInfo->defaultname));
    }
  
    BLI_uniquename_cb(
        customdata_unique_check, &data_arg, NULL, '.', nlayer->name, sizeof(nlayer->name));
  }
  
  void CustomData_validate_layer_name(const CustomData *data,
                                      int type,
                                      const char *name,
                                      char *outname)
  {
    int index = -1;
  
    /* if a layer name was given, try to find that layer */
    if (name[0]) {
      index = CustomData_get_named_layer_index(data, type, name);
    }
  
    if (index == -1) {
      /* either no layer was specified, or the layer we want has been
       * deleted, so assign the active layer to name
       */
      index = CustomData_get_active_layer_index(data, type);
      BLI_strncpy(outname, data->layers[index].name, MAX_CUSTOMDATA_LAYER_NAME);
    }
    else {
      BLI_strncpy(outname, name, MAX_CUSTOMDATA_LAYER_NAME);
    }
  }
  
  bool CustomData_verify_versions(struct CustomData *data, int index)
  {
    const LayerTypeInfo *typeInfo;
    CustomDataLayer *layer = &data->layers[index];
    bool keeplayer = true;
  
    if (layer->type >= CD_NUMTYPES) {
      keeplayer = false; /* unknown layer type from future version */
    }
    else {
      typeInfo = layerType_getInfo(layer->type);
  
      if (!typeInfo->defaultname && (index > 0) && data->layers[index - 1].type == layer->type) {
        keeplayer = false; /* multiple layers of which we only support one */
      }
      /* This is a preemptive fix for cases that should not happen
       * (layers that should not be written in .blend files),
       * but can happen due to bugs (see e.g. T62318).
       * Also for forward compatibility, in future,
       * we may put into `.blend` file some currently un-written data types,
       * this should cover that case as well.
       * Better to be safe here, and fix issue on the fly rather than crash... */
      /* 0 structnum is used in writing code to tag layer types that should not be written. */
      else if (typeInfo->structnum == 0 &&
               /* XXX Not sure why those three are exception, maybe that should be fixed? */
               !ELEM(layer->type, CD_PAINT_MASK, CD_FACEMAP, CD_MTEXPOLY, CD_SCULPT_FACE_SETS)) {
        keeplayer = false;
        CLOG_WARN(&LOG, ".blend file read: removing a data layer that should not have been written");
      }
    }
  
    if (!keeplayer) {
      for (int i = index + 1; i < data->totlayer; i++) {
        data->layers[i - 1] = data->layers[i];
      }
      data->totlayer--;
    }
  
    return keeplayer;
  }
  
  /**
   * Validate and fix data of \a layer,
   * if possible (needs relevant callback in layer's type to be defined).
   *
   * \return True if some errors were found.
   */
  bool CustomData_layer_validate(CustomDataLayer *layer, const uint totitems, const bool do_fixes)
  {
    const LayerTypeInfo *typeInfo = layerType_getInfo(layer->type);
  
    if (typeInfo->validate != NULL) {
      return typeInfo->validate(layer->data, totitems, do_fixes);
    }
  
    return false;
  }
  
  void CustomData_layers__print(CustomData *data)
  {
  
    printf("{\n");
  
    int i;
    const CustomDataLayer *layer;
    for (i = 0, layer = data->layers; i < data->totlayer; i++, layer++) {
      const char *name = CustomData_layertype_name(layer->type);
      const int size = CustomData_sizeof(layer->type);
      const char *structname;
      int structnum;
      CustomData_file_write_info(layer->type, &structname, &structnum);
      printf("        dict(name='%s', struct='%s', type=%d, ptr='%p', elem=%d, length=%d),\n",
             name,
             structname,
             layer->type,
             (const void *)layer->data,
             size,
             (int)(MEM_allocN_len(layer->data) / size));
    }
  
    printf("}\n");
  }
  
  /****************************** External Files *******************************/
  
  static void customdata_external_filename(char filename[FILE_MAX],
                                           ID *id,
                                           CustomDataExternal *external)
  {
    BLI_strncpy(filename, external->filename, FILE_MAX);
    BLI_path_abs(filename, ID_BLEND_PATH_FROM_GLOBAL(id));
  }
  
  void CustomData_external_reload(CustomData *data, ID *UNUSED(id), CustomDataMask mask, int totelem)
  {
    for (int i = 0; i < data->totlayer; i++) {
      CustomDataLayer *layer = &data->layers[i];
      const LayerTypeInfo *typeInfo = layerType_getInfo(layer->type);
  
      if (!(mask & CD_TYPE_AS_MASK(layer->type))) {
        /* pass */
      }
      else if ((layer->flag & CD_FLAG_EXTERNAL) && (layer->flag & CD_FLAG_IN_MEMORY)) {
        if (typeInfo->free) {
          typeInfo->free(layer->data, totelem, typeInfo->size);
        }
        layer->flag &= ~CD_FLAG_IN_MEMORY;
      }
    }
  }
  
  void CustomData_external_read(CustomData *data, ID *id, CustomDataMask mask, int totelem)
  {
    CustomDataExternal *external = data->external;
    CustomDataLayer *layer;
    CDataFile *cdf;
    CDataFileLayer *blay;
    char filename[FILE_MAX];
    const LayerTypeInfo *typeInfo;
    int update = 0;
  
    if (!external) {
      return;
    }
  
    for (int i = 0; i < data->totlayer; i++) {
      layer = &data->layers[i];
      typeInfo = layerType_getInfo(layer->type);
  
      if (!(mask & CD_TYPE_AS_MASK(layer->type))) {
        /* pass */
      }
      else if (layer->flag & CD_FLAG_IN_MEMORY) {
        /* pass */
      }
      else if ((layer->flag & CD_FLAG_EXTERNAL) && typeInfo->read) {
        update = 1;
      }
    }
  
    if (!update) {
      return;
    }
  
    customdata_external_filename(filename, id, external);
  
    cdf = cdf_create(CDF_TYPE_MESH);
    if (!cdf_read_open(cdf, filename)) {
      cdf_free(cdf);
      CLOG_ERROR(&LOG, "Failed to read %s layer from %s.", layerType_getName(layer->type), filename);
      return;
    }
  
    for (int i = 0; i < data->totlayer; i++) {
      layer = &data->layers[i];
      typeInfo = layerType_getInfo(layer->type);
  
      if (!(mask & CD_TYPE_AS_MASK(layer->type))) {
        /* pass */
      }
      else if (layer->flag & CD_FLAG_IN_MEMORY) {
        /* pass */
      }
      else if ((layer->flag & CD_FLAG_EXTERNAL) && typeInfo->read) {
        blay = cdf_layer_find(cdf, layer->type, layer->name);
  
        if (blay) {
          if (cdf_read_layer(cdf, blay)) {
            if (typeInfo->read(cdf, layer->data, totelem)) {
              /* pass */
            }
            else {
              break;
            }
            layer->flag |= CD_FLAG_IN_MEMORY;
          }
          else {
            break;
          }
        }
      }
    }
  
    cdf_read_close(cdf);
    cdf_free(cdf);
  }
  
  void CustomData_external_write(
      CustomData *data, ID *id, CustomDataMask mask, int totelem, int free)
  {
    CustomDataExternal *external = data->external;
    CustomDataLayer *layer;
    CDataFile *cdf;
    CDataFileLayer *blay;
    const LayerTypeInfo *typeInfo;
    int update = 0;
    char filename[FILE_MAX];
  
    if (!external) {
      return;
    }
  
    /* test if there is anything to write */
    for (int i = 0; i < data->totlayer; i++) {
      layer = &data->layers[i];
      typeInfo = layerType_getInfo(layer->type);
  
      if (!(mask & CD_TYPE_AS_MASK(layer->type))) {
        /* pass */
      }
      else if ((layer->flag & CD_FLAG_EXTERNAL) && typeInfo->write) {
        update = 1;
      }
    }
  
    if (!update) {
      return;
    }
  
    /* make sure data is read before we try to write */
    CustomData_external_read(data, id, mask, totelem);
    customdata_external_filename(filename, id, external);
  
    cdf = cdf_create(CDF_TYPE_MESH);
  
    for (int i = 0; i < data->totlayer; i++) {
      layer = &data->layers[i];
      typeInfo = layerType_getInfo(layer->type);
  
      if ((layer->flag & CD_FLAG_EXTERNAL) && typeInfo->filesize) {
        if (layer->flag & CD_FLAG_IN_MEMORY) {
          cdf_layer_add(
              cdf, layer->type, layer->name, typeInfo->filesize(cdf, layer->data, totelem));
        }
        else {
          cdf_free(cdf);
          return; /* read failed for a layer! */
        }
      }
    }
  
    if (!cdf_write_open(cdf, filename)) {
      CLOG_ERROR(&LOG, "Failed to open %s for writing.", filename);
      cdf_free(cdf);
      return;
    }
  
    int i;
    for (i = 0; i < data->totlayer; i++) {
      layer = &data->layers[i];
      typeInfo = layerType_getInfo(layer->type);
  
      if ((layer->flag & CD_FLAG_EXTERNAL) && typeInfo->write) {
        blay = cdf_layer_find(cdf, layer->type, layer->name);
  
        if (cdf_write_layer(cdf, blay)) {
          if (typeInfo->write(cdf, layer->data, totelem)) {
            /* pass */
          }
          else {
            break;
          }
        }
        else {
          break;
        }
      }
    }
  
    if (i != data->totlayer) {
      CLOG_ERROR(&LOG, "Failed to write data to %s.", filename);
      cdf_write_close(cdf);
      cdf_free(cdf);
      return;
    }
  
    for (i = 0; i < data->totlayer; i++) {
      layer = &data->layers[i];
      typeInfo = layerType_getInfo(layer->type);
  
      if ((layer->flag & CD_FLAG_EXTERNAL) && typeInfo->write) {
        if (free) {
          if (typeInfo->free) {
            typeInfo->free(layer->data, totelem, typeInfo->size);
          }
          layer->flag &= ~CD_FLAG_IN_MEMORY;
        }
      }
    }
  
    cdf_write_close(cdf);
    cdf_free(cdf);
  }
  
  void CustomData_external_add(
      CustomData *data, ID *UNUSED(id), int type, int UNUSED(totelem), const char *filename)
  {
    CustomDataExternal *external = data->external;
    CustomDataLayer *layer;
    int layer_index;
  
    layer_index = CustomData_get_active_layer_index(data, type);
    if (layer_index == -1) {
      return;
    }
  
    layer = &data->layers[layer_index];
  
    if (layer->flag & CD_FLAG_EXTERNAL) {
      return;
    }
  
    if (!external) {
      external = MEM_callocN(sizeof(CustomDataExternal), "CustomDataExternal");
      data->external = external;
    }
    BLI_strncpy(external->filename, filename, sizeof(external->filename));
  
    layer->flag |= CD_FLAG_EXTERNAL | CD_FLAG_IN_MEMORY;
  }
  
  void CustomData_external_remove(CustomData *data, ID *id, int type, int totelem)
  {
    CustomDataExternal *external = data->external;
  
    int layer_index = CustomData_get_active_layer_index(data, type);
    if (layer_index == -1) {
      return;
    }
  
    CustomDataLayer *layer = &data->layers[layer_index];
  
    if (!external) {
      return;
    }
  
    if (layer->flag & CD_FLAG_EXTERNAL) {
      if (!(layer->flag & CD_FLAG_IN_MEMORY)) {
        CustomData_external_read(data, id, CD_TYPE_AS_MASK(layer->type), totelem);
      }
  
      layer->flag &= ~CD_FLAG_EXTERNAL;
    }
  }
  
  bool CustomData_external_test(CustomData *data, int type)
  {
    int layer_index = CustomData_get_active_layer_index(data, type);
    if (layer_index == -1) {
      return false;
    }
  
    CustomDataLayer *layer = &data->layers[layer_index];
    return (layer->flag & CD_FLAG_EXTERNAL) != 0;
  }
  
  /* ********** Mesh-to-mesh data transfer ********** */
  static void copy_bit_flag(void *dst, const void *src, const size_t data_size, const uint64_t flag)
  {
  #define COPY_BIT_FLAG(_type, _dst, _src, _f) \
    { \
      const _type _val = *((_type *)(_src)) & ((_type)(_f)); \
      *((_type *)(_dst)) &= ~((_type)(_f)); \
      *((_type *)(_dst)) |= _val; \
    } \
    (void)0
  
    switch (data_size) {
      case 1:
        COPY_BIT_FLAG(uint8_t, dst, src, flag);
        break;
      case 2:
        COPY_BIT_FLAG(uint16_t, dst, src, flag);
        break;
      case 4:
        COPY_BIT_FLAG(uint32_t, dst, src, flag);
        break;
      case 8:
        COPY_BIT_FLAG(uint64_t, dst, src, flag);
        break;
      default:
        // CLOG_ERROR(&LOG, "Unknown flags-container size (%zu)", datasize);
        break;
    }
  
  #undef COPY_BIT_FLAG
  }
  
  static bool check_bit_flag(const void *data, const size_t data_size, const uint64_t flag)
  {
    switch (data_size) {
      case 1:
        return ((*((uint8_t *)data) & ((uint8_t)flag)) != 0);
      case 2:
        return ((*((uint16_t *)data) & ((uint16_t)flag)) != 0);
      case 4:
        return ((*((uint32_t *)data) & ((uint32_t)flag)) != 0);
      case 8:
        return ((*((uint64_t *)data) & ((uint64_t)flag)) != 0);
      default:
        // CLOG_ERROR(&LOG, "Unknown flags-container size (%zu)", datasize);
        return false;
    }
  }
  
  static void customdata_data_transfer_interp_generic(const CustomDataTransferLayerMap *laymap,
                                                      void *data_dst,
                                                      const void **sources,
                                                      const float *weights,
                                                      const int count,
                                                      const float mix_factor)
  {
    BLI_assert(weights != NULL);
    BLI_assert(count > 0);
  
    /* Fake interpolation, we actually copy highest weighted source to dest.
     * Note we also handle bitflags here,
     * in which case we rather choose to transfer value of elements totaling
     * more than 0.5 of weight. */
    int best_src_idx = 0;
  
    const int data_type = laymap->data_type;
    const int mix_mode = laymap->mix_mode;
  
    size_t data_size;
    const uint64_t data_flag = laymap->data_flag;
  
    cd_interp interp_cd = NULL;
    cd_copy copy_cd = NULL;
  
    void *tmp_dst;
  
    if (!sources) {
      /* Not supported here, abort. */
      return;
    }
  
    if (data_type & CD_FAKE) {
      data_size = laymap->data_size;
    }
    else {
      const LayerTypeInfo *type_info = layerType_getInfo(data_type);
  
      data_size = (size_t)type_info->size;
      interp_cd = type_info->interp;
      copy_cd = type_info->copy;
    }
  
    tmp_dst = MEM_mallocN(data_size, __func__);
  
    if (count > 1 && !interp_cd) {
      if (data_flag) {
        /* Boolean case, we can 'interpolate' in two groups,
         * and choose value from highest weighted group. */
        float tot_weight_true = 0.0f;
        int item_true_idx = -1, item_false_idx = -1;
  
        for (int i = 0; i < count; i++) {
          if (check_bit_flag(sources[i], data_size, data_flag)) {
            tot_weight_true += weights[i];
            item_true_idx = i;
          }
          else {
            item_false_idx = i;
          }
        }
        best_src_idx = (tot_weight_true >= 0.5f) ? item_true_idx : item_false_idx;
      }
      else {
        /* We just choose highest weighted source. */
        float max_weight = 0.0f;
  
        for (int i = 0; i < count; i++) {
          if (weights[i] > max_weight) {
            max_weight = weights[i];
            best_src_idx = i;
          }
        }
      }
    }
  
    BLI_assert(best_src_idx >= 0);
  
    if (interp_cd) {
      interp_cd(sources, weights, NULL, count, tmp_dst);
    }
    else if (data_flag) {
      copy_bit_flag(tmp_dst, sources[best_src_idx], data_size, data_flag);
    }
    /* No interpolation, just copy highest weight source element's data. */
    else if (copy_cd) {
      copy_cd(sources[best_src_idx], tmp_dst, 1);
    }
    else {
      memcpy(tmp_dst, sources[best_src_idx], data_size);
    }
  
    if (data_flag) {
      /* Bool flags, only copy if dest data is set (resp. unset) -
       * only 'advanced' modes we can support here! */
      if (mix_factor >= 0.5f && ((mix_mode == CDT_MIX_TRANSFER) ||
                                 (mix_mode == CDT_MIX_REPLACE_ABOVE_THRESHOLD &&
                                  check_bit_flag(data_dst, data_size, data_flag)) ||
                                 (mix_mode == CDT_MIX_REPLACE_BELOW_THRESHOLD &&
                                  !check_bit_flag(data_dst, data_size, data_flag)))) {
        copy_bit_flag(data_dst, tmp_dst, data_size, data_flag);
      }
    }
    else if (!(data_type & CD_FAKE)) {
      CustomData_data_mix_value(data_type, tmp_dst, data_dst, mix_mode, mix_factor);
    }
    /* Else we can do nothing by default, needs custom interp func!
     * Note this is here only for sake of consistency, not expected to be used much actually? */
    else {
      if (mix_factor >= 0.5f) {
        memcpy(data_dst, tmp_dst, data_size);
      }
    }
  
    MEM_freeN(tmp_dst);
  }
  
  /* Normals are special, we need to take care of source & destination spaces... */
  void customdata_data_transfer_interp_normal_normals(const CustomDataTransferLayerMap *laymap,
                                                      void *data_dst,
                                                      const void **sources,
                                                      const float *weights,
                                                      const int count,
                                                      const float mix_factor)
  {
    BLI_assert(weights != NULL);
    BLI_assert(count > 0);
  
    const int data_type = laymap->data_type;
    const int mix_mode = laymap->mix_mode;
  
    SpaceTransform *space_transform = laymap->interp_data;
  
    const LayerTypeInfo *type_info = layerType_getInfo(data_type);
    cd_interp interp_cd = type_info->interp;
  
    float tmp_dst[3];
  
    BLI_assert(data_type == CD_NORMAL);
  
    if (!sources) {
      /* Not supported here, abort. */
      return;
    }
  
    interp_cd(sources, weights, NULL, count, tmp_dst);
    if (space_transform) {
      /* tmp_dst is in source space so far, bring it back in destination space. */
      BLI_space_transform_invert_normal(space_transform, tmp_dst);
    }
  
    CustomData_data_mix_value(data_type, tmp_dst, data_dst, mix_mode, mix_factor);
  }
  
  void CustomData_data_transfer(const MeshPairRemap *me_remap,
                                const CustomDataTransferLayerMap *laymap)
  {
    MeshPairRemapItem *mapit = me_remap->items;
    const int totelem = me_remap->items_num;
  
    const int data_type = laymap->data_type;
    const void *data_src = laymap->data_src;
    void *data_dst = laymap->data_dst;
  
    size_t data_step;
    size_t data_size;
    size_t data_offset;
  
    cd_datatransfer_interp interp = NULL;
  
    size_t tmp_buff_size = 32;
    const void **tmp_data_src = NULL;
  
    /* Note: NULL data_src may happen and be valid (see vgroups...). */
    if (!data_dst) {
      return;
    }
  
    if (data_src) {
      tmp_data_src = MEM_malloc_arrayN(tmp_buff_size, sizeof(*tmp_data_src), __func__);
    }
  
    if (data_type & CD_FAKE) {
      data_step = laymap->elem_size;
      data_size = laymap->data_size;
      data_offset = laymap->data_offset;
    }
    else {
      const LayerTypeInfo *type_info = layerType_getInfo(data_type);
  
      /* Note: we can use 'fake' CDLayers, like e.g. for crease, bweight, etc. :/ */
      data_size = (size_t)type_info->size;
      data_step = laymap->elem_size ? laymap->elem_size : data_size;
      data_offset = laymap->data_offset;
    }
  
    interp = laymap->interp ? laymap->interp : customdata_data_transfer_interp_generic;
  
    for (int i = 0; i < totelem; i++, data_dst = POINTER_OFFSET(data_dst, data_step), mapit++) {
      const int sources_num = mapit->sources_num;
      const float mix_factor = laymap->mix_factor *
                               (laymap->mix_weights ? laymap->mix_weights[i] : 1.0f);
  
      if (!sources_num) {
        /* No sources for this element, skip it. */
        continue;
      }
  
      if (tmp_data_src) {
        if (UNLIKELY(sources_num > tmp_buff_size)) {
          tmp_buff_size = (size_t)sources_num;
          tmp_data_src = MEM_reallocN((void *)tmp_data_src, sizeof(*tmp_data_src) * tmp_buff_size);
        }
  
        for (int j = 0; j < sources_num; j++) {
          const size_t src_idx = (size_t)mapit->indices_src[j];
          tmp_data_src[j] = POINTER_OFFSET(data_src, (data_step * src_idx) + data_offset);
        }
      }
  
      interp(laymap,
             POINTER_OFFSET(data_dst, data_offset),
             tmp_data_src,
             mapit->weights_src,
             sources_num,
             mix_factor);
    }
  
    MEM_SAFE_FREE(tmp_data_src);
  }
  
  static void write_mdisps(BlendWriter *writer, int count, MDisps *mdlist, int external)
  {
    if (mdlist) {
      BLO_write_struct_array(writer, MDisps, count, mdlist);
      for (int i = 0; i < count; i++) {
        MDisps *md = &mdlist[i];
        if (md->disps) {
          if (!external) {
            BLO_write_float3_array(writer, md->totdisp, &md->disps[0][0]);
          }
        }
  
        if (md->hidden) {
          BLO_write_raw(writer, BLI_BITMAP_SIZE(md->totdisp), md->hidden);
        }
      }
    }
  }
  
  static void write_grid_paint_mask(BlendWriter *writer, int count, GridPaintMask *grid_paint_mask)
  {
    if (grid_paint_mask) {
      BLO_write_struct_array(writer, GridPaintMask, count, grid_paint_mask);
      for (int i = 0; i < count; i++) {
        GridPaintMask *gpm = &grid_paint_mask[i];
        if (gpm->data) {
          const int gridsize = BKE_ccg_gridsize(gpm->level);
          BLO_write_raw(writer, sizeof(*gpm->data) * gridsize * gridsize, gpm->data);
        }
      }
    }
  }
  
  /**
   * \param layers: The layers argument assigned by #CustomData_blend_write_prepare.
   */
  void CustomData_blend_write(BlendWriter *writer,
                              CustomData *data,
                              CustomDataLayer *layers,
                              int count,
                              CustomDataMask cddata_mask,
                              ID *id)
  {
    /* write external customdata (not for undo) */
    if (data->external && !BLO_write_is_undo(writer)) {
      CustomData_external_write(data, id, cddata_mask, count, 0);
    }
  
    BLO_write_struct_array_at_address(writer, CustomDataLayer, data->totlayer, data->layers, layers);
  
    for (int i = 0; i < data->totlayer; i++) {
      CustomDataLayer *layer = &layers[i];
  
      if (layer->type == CD_MDEFORMVERT) {
        /* layer types that allocate own memory need special handling */
        BKE_defvert_blend_write(writer, count, layer->data);
      }
      else if (layer->type == CD_MDISPS) {
        write_mdisps(writer, count, layer->data, layer->flag & CD_FLAG_EXTERNAL);
      }
      else if (layer->type == CD_PAINT_MASK) {
        const float *layer_data = layer->data;
        BLO_write_raw(writer, sizeof(*layer_data) * count, layer_data);
      }
      else if (layer->type == CD_SCULPT_FACE_SETS) {
        const float *layer_data = layer->data;
        BLO_write_raw(writer, sizeof(*layer_data) * count, layer_data);
      }
      else if (layer->type == CD_GRID_PAINT_MASK) {
        write_grid_paint_mask(writer, count, layer->data);
      }
      else if (layer->type == CD_FACEMAP) {
        const int *layer_data = layer->data;
        BLO_write_raw(writer, sizeof(*layer_data) * count, layer_data);
      }
      else {
        const char *structname;
        int structnum;
        CustomData_file_write_info(layer->type, &structname, &structnum);
        if (structnum) {
          int datasize = structnum * count;
          BLO_write_struct_array_by_name(writer, structname, datasize, layer->data);
        }
        else if (!BLO_write_is_undo(writer)) { /* Do not warn on undo. */
          printf("%s error: layer '%s':%d - can't be written to file\n",
                 __func__,
                 structname,
                 layer->type);
        }
      }
    }
  
    if (data->external) {
      BLO_write_struct(writer, CustomDataExternal, data->external);
    }
  }
  
  static void blend_read_mdisps(BlendDataReader *reader, int count, MDisps *mdisps, int external)
  {
    if (mdisps) {
      for (int i = 0; i < count; i++) {
        BLO_read_data_address(reader, &mdisps[i].disps);
        BLO_read_data_address(reader, &mdisps[i].hidden);
  
        if (mdisps[i].totdisp && !mdisps[i].level) {
          /* this calculation is only correct for loop mdisps;
           * if loading pre-BMesh face mdisps this will be
           * overwritten with the correct value in
           * bm_corners_to_loops() */
          float gridsize = sqrtf(mdisps[i].totdisp);
          mdisps[i].level = (int)(logf(gridsize - 1.0f) / (float)M_LN2) + 1;
        }
  
        if (BLO_read_requires_endian_switch(reader) && (mdisps[i].disps)) {
          /* DNA_struct_switch_endian doesn't do endian swap for (*disps)[] */
          /* this does swap for data written at write_mdisps() - readfile.c */
          BLI_endian_switch_float_array(*mdisps[i].disps, mdisps[i].totdisp * 3);
        }
        if (!external && !mdisps[i].disps) {
          mdisps[i].totdisp = 0;
        }
      }
    }
  }
  
  static void blend_read_paint_mask(BlendDataReader *reader,
                                    int count,
                                    GridPaintMask *grid_paint_mask)
  {
    if (grid_paint_mask) {
      for (int i = 0; i < count; i++) {
        GridPaintMask *gpm = &grid_paint_mask[i];
        if (gpm->data) {
          BLO_read_data_address(reader, &gpm->data);
        }
      }
    }
  }
  
  void CustomData_blend_read(BlendDataReader *reader, CustomData *data, int count)
  {
    BLO_read_data_address(reader, &data->layers);
  
    /* Annoying workaround for bug T31079 loading legacy files with
     * no polygons _but_ have stale custom-data. */
    if (UNLIKELY(count == 0 && data->layers == NULL && data->totlayer != 0)) {
      CustomData_reset(data);
      return;
    }
  
    BLO_read_data_address(reader, &data->external);
  
    int i = 0;
    while (i < data->totlayer) {
      CustomDataLayer *layer = &data->layers[i];
  
      if (layer->flag & CD_FLAG_EXTERNAL) {
        layer->flag &= ~CD_FLAG_IN_MEMORY;
      }
  
      layer->flag &= ~CD_FLAG_NOFREE;
  
      if (CustomData_verify_versions(data, i)) {
        BLO_read_data_address(reader, &layer->data);
        if (layer->type == CD_MDISPS) {
          blend_read_mdisps(reader, count, layer->data, layer->flag & CD_FLAG_EXTERNAL);
        }
        else if (layer->type == CD_GRID_PAINT_MASK) {
          blend_read_paint_mask(reader, count, layer->data);
        }
        i++;
      }
    }
  
    CustomData_update_typemap(data);
  }
  