text: /*
   * jdmaster.c
   *
   * Copyright (C) 1991-1997, Thomas G. Lane.
   * Modified 2002-2019 by Guido Vollbeding.
   * This file is part of the Independent JPEG Group's software.
   * For conditions of distribution and use, see the accompanying README file.
   *
   * This file contains master control logic for the JPEG decompressor.
   * These routines are concerned with selecting the modules to be executed
   * and with determining the number of passes and the work to be done in each
   * pass.
   */
  
  #define JPEG_INTERNALS
  #include "jinclude.h"
  #include "jpeglib.h"
  
  
  /* Private state */
  
  typedef struct {
    struct jpeg_decomp_master pub; /* public fields */
  
    int pass_number;		/* # of passes completed */
  
    boolean using_merged_upsample; /* TRUE if using merged upsample/cconvert */
  
    /* Saved references to initialized quantizer modules,
     * in case we need to switch modes.
     */
    struct jpeg_color_quantizer * quantizer_1pass;
    struct jpeg_color_quantizer * quantizer_2pass;
  } my_decomp_master;
  
  typedef my_decomp_master * my_master_ptr;
  
  
  /*
   * Determine whether merged upsample/color conversion should be used.
   * CRUCIAL: this must match the actual capabilities of jdmerge.c!
   */
  
  LOCAL(boolean)
  use_merged_upsample (j_decompress_ptr cinfo)
  {
  #ifdef UPSAMPLE_MERGING_SUPPORTED
    /* Merging is the equivalent of plain box-filter upsampling. */
    /* The following condition is only needed if fancy shall select
     * a different upsampling method.  In our current implementation
     * fancy only affects the DCT scaling, thus we can use fancy
     * upsampling and merged upsample simultaneously, in particular
     * with scaled DCT sizes larger than the default DCTSIZE.
     */
  #if 0
    if (cinfo->do_fancy_upsampling)
      return FALSE;
  #endif
    if (cinfo->CCIR601_sampling)
      return FALSE;
    /* jdmerge.c only supports YCC=>RGB color conversion */
    if ((cinfo->jpeg_color_space != JCS_YCbCr &&
         cinfo->jpeg_color_space != JCS_BG_YCC) ||
        cinfo->num_components != 3 ||
        cinfo->out_color_space != JCS_RGB ||
        cinfo->out_color_components != RGB_PIXELSIZE ||
        cinfo->color_transform)
      return FALSE;
    /* and it only handles 2h1v or 2h2v sampling ratios */
    if (cinfo->comp_info[0].h_samp_factor != 2 ||
        cinfo->comp_info[1].h_samp_factor != 1 ||
        cinfo->comp_info[2].h_samp_factor != 1 ||
        cinfo->comp_info[0].v_samp_factor >  2 ||
        cinfo->comp_info[1].v_samp_factor != 1 ||
        cinfo->comp_info[2].v_samp_factor != 1)
      return FALSE;
    /* furthermore, it doesn't work if we've scaled the IDCTs differently */
    if (cinfo->comp_info[0].DCT_h_scaled_size != cinfo->min_DCT_h_scaled_size ||
        cinfo->comp_info[1].DCT_h_scaled_size != cinfo->min_DCT_h_scaled_size ||
        cinfo->comp_info[2].DCT_h_scaled_size != cinfo->min_DCT_h_scaled_size ||
        cinfo->comp_info[0].DCT_v_scaled_size != cinfo->min_DCT_v_scaled_size ||
        cinfo->comp_info[1].DCT_v_scaled_size != cinfo->min_DCT_v_scaled_size ||
        cinfo->comp_info[2].DCT_v_scaled_size != cinfo->min_DCT_v_scaled_size)
      return FALSE;
    /* ??? also need to test for upsample-time rescaling, when & if supported */
    return TRUE;			/* by golly, it'll work... */
  #else
    return FALSE;
  #endif
  }
  
  
  /*
   * Compute output image dimensions and related values.
   * NOTE: this is exported for possible use by application.
   * Hence it mustn't do anything that can't be done twice.
   * Also note that it may be called before the master module is initialized!
   */
  
  GLOBAL(void)
  jpeg_calc_output_dimensions (j_decompress_ptr cinfo)
  /* Do computations that are needed before master selection phase.
   * This function is used for full decompression.
   */
  {
  #ifdef IDCT_SCALING_SUPPORTED
    int ci, ssize;
    jpeg_component_info *compptr;
  #endif
  
    /* Prevent application from calling me at wrong times */
    if (cinfo->global_state != DSTATE_READY)
      ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  
    /* Compute core output image dimensions and DCT scaling choices. */
    jpeg_core_output_dimensions(cinfo);
  
  #ifdef IDCT_SCALING_SUPPORTED
  
    /* In selecting the actual DCT scaling for each component, we try to
     * scale up the chroma components via IDCT scaling rather than upsampling.
     * This saves time if the upsampler gets to use 1:1 scaling.
     * Note this code adapts subsampling ratios which are powers of 2.
     */
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
         ci++, compptr++) {
      ssize = 1;
      if (! cinfo->raw_data_out)
        while (cinfo->min_DCT_h_scaled_size * ssize <=
  	     (cinfo->do_fancy_upsampling ? DCTSIZE : DCTSIZE / 2) &&
  	     (cinfo->max_h_samp_factor % (compptr->h_samp_factor * ssize * 2)) ==
  	     0) {
  	ssize = ssize * 2;
        }
      compptr->DCT_h_scaled_size = cinfo->min_DCT_h_scaled_size * ssize;
      ssize = 1;
      if (! cinfo->raw_data_out)
        while (cinfo->min_DCT_v_scaled_size * ssize <=
  	     (cinfo->do_fancy_upsampling ? DCTSIZE : DCTSIZE / 2) &&
  	     (cinfo->max_v_samp_factor % (compptr->v_samp_factor * ssize * 2)) ==
  	     0) {
  	ssize = ssize * 2;
        }
      compptr->DCT_v_scaled_size = cinfo->min_DCT_v_scaled_size * ssize;
  
      /* We don't support IDCT ratios larger than 2. */
      if (compptr->DCT_h_scaled_size > compptr->DCT_v_scaled_size * 2)
  	compptr->DCT_h_scaled_size = compptr->DCT_v_scaled_size * 2;
      else if (compptr->DCT_v_scaled_size > compptr->DCT_h_scaled_size * 2)
  	compptr->DCT_v_scaled_size = compptr->DCT_h_scaled_size * 2;
  
      /* Recompute downsampled dimensions of components;
       * application needs to know these if using raw downsampled data.
       */
      /* Size in samples, after IDCT scaling */
      compptr->downsampled_width = (JDIMENSION)
        jdiv_round_up((long) cinfo->image_width *
  		    (long) (compptr->h_samp_factor * compptr->DCT_h_scaled_size),
  		    (long) (cinfo->max_h_samp_factor * cinfo->block_size));
      compptr->downsampled_height = (JDIMENSION)
        jdiv_round_up((long) cinfo->image_height *
  		    (long) (compptr->v_samp_factor * compptr->DCT_v_scaled_size),
  		    (long) (cinfo->max_v_samp_factor * cinfo->block_size));
    }
  
  #endif /* IDCT_SCALING_SUPPORTED */
  
    /* Report number of components in selected colorspace. */
    /* Probably this should be in the color conversion module... */
    switch (cinfo->out_color_space) {
    case JCS_GRAYSCALE:
      cinfo->out_color_components = 1;
      break;
    case JCS_RGB:
    case JCS_BG_RGB:
  #if RGB_PIXELSIZE != 3
      cinfo->out_color_components = RGB_PIXELSIZE;
      break;
  #endif /* else share code with YCbCr */
    case JCS_YCbCr:
    case JCS_BG_YCC:
      cinfo->out_color_components = 3;
      break;
    case JCS_CMYK:
    case JCS_YCCK:
      cinfo->out_color_components = 4;
      break;
    default:			/* else must be same colorspace as in file */
      cinfo->out_color_components = cinfo->num_components;
    }
    cinfo->output_components = (cinfo->quantize_colors ? 1 :
  			      cinfo->out_color_components);
  
    /* See if upsampler will want to emit more than one row at a time */
    if (use_merged_upsample(cinfo))
      cinfo->rec_outbuf_height = cinfo->max_v_samp_factor;
    else
      cinfo->rec_outbuf_height = 1;
  }
  
  
  /*
   * Several decompression processes need to range-limit values to the range
   * 0..MAXJSAMPLE; the input value may fall somewhat outside this range
   * due to noise introduced by quantization, roundoff error, etc.  These
   * processes are inner loops and need to be as fast as possible.  On most
   * machines, particularly CPUs with pipelines or instruction prefetch,
   * a (subscript-check-less) C table lookup
   *		x = sample_range_limit[x];
   * is faster than explicit tests
   *		if (x < 0)  x = 0;
   *		else if (x > MAXJSAMPLE)  x = MAXJSAMPLE;
   * These processes all use a common table prepared by the routine below.
   *
   * For most steps we can mathematically guarantee that the initial value
   * of x is within 2*(MAXJSAMPLE+1) of the legal range, so a table running
   * from -2*(MAXJSAMPLE+1) to 3*MAXJSAMPLE+2 is sufficient.  But for the
   * initial limiting step (just after the IDCT), a wildly out-of-range value
   * is possible if the input data is corrupt.  To avoid any chance of indexing
   * off the end of memory and getting a bad-pointer trap, we perform the
   * post-IDCT limiting thus:
   *		x = (sample_range_limit - SUBSET)[(x + CENTER) & MASK];
   * where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit
   * samples.  Under normal circumstances this is more than enough range and
   * a correct output will be generated; with bogus input data the mask will
   * cause wraparound, and we will safely generate a bogus-but-in-range output.
   * For the post-IDCT step, we want to convert the data from signed to unsigned
   * representation by adding CENTERJSAMPLE at the same time that we limit it.
   * This is accomplished with SUBSET = CENTER - CENTERJSAMPLE.
   *
   * Note that the table is allocated in near data space on PCs; it's small
   * enough and used often enough to justify this.
   */
  
  LOCAL(void)
  prepare_range_limit_table (j_decompress_ptr cinfo)
  /* Allocate and fill in the sample_range_limit table */
  {
    JSAMPLE * table;
    int i;
  
    table = (JSAMPLE *) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo,
      JPOOL_IMAGE, (RANGE_CENTER * 2 + MAXJSAMPLE + 1) * SIZEOF(JSAMPLE));
    /* First segment of range limit table: limit[x] = 0 for x < 0 */
    MEMZERO(table, RANGE_CENTER * SIZEOF(JSAMPLE));
    table += RANGE_CENTER;	/* allow negative subscripts of table */
    cinfo->sample_range_limit = table;
    /* Main part of range limit table: limit[x] = x */
    for (i = 0; i <= MAXJSAMPLE; i++)
      table[i] = (JSAMPLE) i;
    /* End of range limit table: limit[x] = MAXJSAMPLE for x > MAXJSAMPLE */
    for (; i <=  MAXJSAMPLE + RANGE_CENTER; i++)
      table[i] = MAXJSAMPLE;
  }
  
  
  /*
   * Master selection of decompression modules.
   * This is done once at jpeg_start_decompress time.  We determine
   * which modules will be used and give them appropriate initialization calls.
   * We also initialize the decompressor input side to begin consuming data.
   *
   * Since jpeg_read_header has finished, we know what is in the SOF
   * and (first) SOS markers.  We also have all the application parameter
   * settings.
   */
  
  LOCAL(void)
  master_selection (j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr) cinfo->master;
    boolean use_c_buffer;
    long samplesperrow;
    JDIMENSION jd_samplesperrow;
  
    /* For now, precision must match compiled-in value... */
    if (cinfo->data_precision != BITS_IN_JSAMPLE)
      ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
  
    /* Initialize dimensions and other stuff */
    jpeg_calc_output_dimensions(cinfo);
    prepare_range_limit_table(cinfo);
  
    /* Sanity check on image dimensions */
    if (cinfo->output_height <= 0 || cinfo->output_width <= 0 ||
        cinfo->out_color_components <= 0)
      ERREXIT(cinfo, JERR_EMPTY_IMAGE);
  
    /* Width of an output scanline must be representable as JDIMENSION. */
    samplesperrow = (long) cinfo->output_width * (long) cinfo->out_color_components;
    jd_samplesperrow = (JDIMENSION) samplesperrow;
    if ((long) jd_samplesperrow != samplesperrow)
      ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
  
    /* Initialize my private state */
    master->pass_number = 0;
    master->using_merged_upsample = use_merged_upsample(cinfo);
  
    /* Color quantizer selection */
    master->quantizer_1pass = NULL;
    master->quantizer_2pass = NULL;
    /* No mode changes if not using buffered-image mode. */
    if (! cinfo->quantize_colors || ! cinfo->buffered_image) {
      cinfo->enable_1pass_quant = FALSE;
      cinfo->enable_external_quant = FALSE;
      cinfo->enable_2pass_quant = FALSE;
    }
    if (cinfo->quantize_colors) {
      if (cinfo->raw_data_out)
        ERREXIT(cinfo, JERR_NOTIMPL);
      /* 2-pass quantizer only works in 3-component color space. */
      if (cinfo->out_color_components != 3) {
        cinfo->enable_1pass_quant = TRUE;
        cinfo->enable_external_quant = FALSE;
        cinfo->enable_2pass_quant = FALSE;
        cinfo->colormap = NULL;
      } else if (cinfo->colormap != NULL) {
        cinfo->enable_external_quant = TRUE;
      } else if (cinfo->two_pass_quantize) {
        cinfo->enable_2pass_quant = TRUE;
      } else {
        cinfo->enable_1pass_quant = TRUE;
      }
  
      if (cinfo->enable_1pass_quant) {
  #ifdef QUANT_1PASS_SUPPORTED
        jinit_1pass_quantizer(cinfo);
        master->quantizer_1pass = cinfo->cquantize;
  #else
        ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
      }
  
      /* We use the 2-pass code to map to external colormaps. */
      if (cinfo->enable_2pass_quant || cinfo->enable_external_quant) {
  #ifdef QUANT_2PASS_SUPPORTED
        jinit_2pass_quantizer(cinfo);
        master->quantizer_2pass = cinfo->cquantize;
  #else
        ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
      }
      /* If both quantizers are initialized, the 2-pass one is left active;
       * this is necessary for starting with quantization to an external map.
       */
    }
  
    /* Post-processing: in particular, color conversion first */
    if (! cinfo->raw_data_out) {
      if (master->using_merged_upsample) {
  #ifdef UPSAMPLE_MERGING_SUPPORTED
        jinit_merged_upsampler(cinfo); /* does color conversion too */
  #else
        ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
      } else {
        jinit_color_deconverter(cinfo);
        jinit_upsampler(cinfo);
      }
      jinit_d_post_controller(cinfo, cinfo->enable_2pass_quant);
    }
    /* Inverse DCT */
    jinit_inverse_dct(cinfo);
    /* Entropy decoding: either Huffman or arithmetic coding. */
    if (cinfo->arith_code)
      jinit_arith_decoder(cinfo);
    else {
      jinit_huff_decoder(cinfo);
    }
  
    /* Initialize principal buffer controllers. */
    use_c_buffer = cinfo->inputctl->has_multiple_scans || cinfo->buffered_image;
    jinit_d_coef_controller(cinfo, use_c_buffer);
  
    if (! cinfo->raw_data_out)
      jinit_d_main_controller(cinfo, FALSE /* never need full buffer here */);
  
    /* We can now tell the memory manager to allocate virtual arrays. */
    (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
  
    /* Initialize input side of decompressor to consume first scan. */
    (*cinfo->inputctl->start_input_pass) (cinfo);
  
  #ifdef D_MULTISCAN_FILES_SUPPORTED
    /* If jpeg_start_decompress will read the whole file, initialize
     * progress monitoring appropriately.  The input step is counted
     * as one pass.
     */
    if (cinfo->progress != NULL && ! cinfo->buffered_image &&
        cinfo->inputctl->has_multiple_scans) {
      int nscans;
      /* Estimate number of scans to set pass_limit. */
      if (cinfo->progressive_mode) {
        /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
        nscans = 2 + 3 * cinfo->num_components;
      } else {
        /* For a nonprogressive multiscan file, estimate 1 scan per component. */
        nscans = cinfo->num_components;
      }
      cinfo->progress->pass_counter = 0L;
      cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
      cinfo->progress->completed_passes = 0;
      cinfo->progress->total_passes = (cinfo->enable_2pass_quant ? 3 : 2);
      /* Count the input pass as done */
      master->pass_number++;
    }
  #endif /* D_MULTISCAN_FILES_SUPPORTED */
  }
  
  
  /*
   * Per-pass setup.
   * This is called at the beginning of each output pass.  We determine which
   * modules will be active during this pass and give them appropriate
   * start_pass calls.  We also set is_dummy_pass to indicate whether this
   * is a "real" output pass or a dummy pass for color quantization.
   * (In the latter case, jdapistd.c will crank the pass to completion.)
   */
  
  METHODDEF(void)
  prepare_for_output_pass (j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr) cinfo->master;
  
    if (master->pub.is_dummy_pass) {
  #ifdef QUANT_2PASS_SUPPORTED
      /* Final pass of 2-pass quantization */
      master->pub.is_dummy_pass = FALSE;
      (*cinfo->cquantize->start_pass) (cinfo, FALSE);
      (*cinfo->post->start_pass) (cinfo, JBUF_CRANK_DEST);
      (*cinfo->main->start_pass) (cinfo, JBUF_CRANK_DEST);
  #else
      ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif /* QUANT_2PASS_SUPPORTED */
    } else {
      if (cinfo->quantize_colors && cinfo->colormap == NULL) {
        /* Select new quantization method */
        if (cinfo->two_pass_quantize && cinfo->enable_2pass_quant) {
  	cinfo->cquantize = master->quantizer_2pass;
  	master->pub.is_dummy_pass = TRUE;
        } else if (cinfo->enable_1pass_quant) {
  	cinfo->cquantize = master->quantizer_1pass;
        } else {
  	ERREXIT(cinfo, JERR_MODE_CHANGE);
        }
      }
      (*cinfo->idct->start_pass) (cinfo);
      (*cinfo->coef->start_output_pass) (cinfo);
      if (! cinfo->raw_data_out) {
        if (! master->using_merged_upsample)
  	(*cinfo->cconvert->start_pass) (cinfo);
        (*cinfo->upsample->start_pass) (cinfo);
        if (cinfo->quantize_colors)
  	(*cinfo->cquantize->start_pass) (cinfo, master->pub.is_dummy_pass);
        (*cinfo->post->start_pass) (cinfo,
  	    (master->pub.is_dummy_pass ? JBUF_SAVE_AND_PASS : JBUF_PASS_THRU));
        (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
      }
    }
  
    /* Set up progress monitor's pass info if present */
    if (cinfo->progress != NULL) {
      cinfo->progress->completed_passes = master->pass_number;
      cinfo->progress->total_passes = master->pass_number +
  				    (master->pub.is_dummy_pass ? 2 : 1);
      /* In buffered-image mode, we assume one more output pass if EOI not
       * yet reached, but no more passes if EOI has been reached.
       */
      if (cinfo->buffered_image && ! cinfo->inputctl->eoi_reached) {
        cinfo->progress->total_passes += (cinfo->enable_2pass_quant ? 2 : 1);
      }
    }
  }
  
  
  /*
   * Finish up at end of an output pass.
   */
  
  METHODDEF(void)
  finish_output_pass (j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr) cinfo->master;
  
    if (cinfo->quantize_colors)
      (*cinfo->cquantize->finish_pass) (cinfo);
    master->pass_number++;
  }
  
  
  #ifdef D_MULTISCAN_FILES_SUPPORTED
  
  /*
   * Switch to a new external colormap between output passes.
   */
  
  GLOBAL(void)
  jpeg_new_colormap (j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr) cinfo->master;
  
    /* Prevent application from calling me at wrong times */
    if (cinfo->global_state != DSTATE_BUFIMAGE)
      ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  
    if (cinfo->quantize_colors && cinfo->enable_external_quant &&
        cinfo->colormap != NULL) {
      /* Select 2-pass quantizer for external colormap use */
      cinfo->cquantize = master->quantizer_2pass;
      /* Notify quantizer of colormap change */
      (*cinfo->cquantize->new_color_map) (cinfo);
      master->pub.is_dummy_pass = FALSE; /* just in case */
    } else
      ERREXIT(cinfo, JERR_MODE_CHANGE);
  }
  
  #endif /* D_MULTISCAN_FILES_SUPPORTED */
  
  
  /*
   * Initialize master decompression control and select active modules.
   * This is performed at the start of jpeg_start_decompress.
   */
  
  GLOBAL(void)
  jinit_master_decompress (j_decompress_ptr cinfo)
  {
    my_master_ptr master;
  
    master = (my_master_ptr) (*cinfo->mem->alloc_small)
      ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_decomp_master));
    cinfo->master = &master->pub;
    master->pub.prepare_for_output_pass = prepare_for_output_pass;
    master->pub.finish_output_pass = finish_output_pass;
  
    master->pub.is_dummy_pass = FALSE;
  
    master_selection(cinfo);
  }
  