text: /*
   * jccoefct.c
   *
   * Copyright (C) 1994-1997, Thomas G. Lane.
   * 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 the coefficient buffer controller for compression.
   * This controller is the top level of the JPEG compressor proper.
   * The coefficient buffer lies between forward-DCT and entropy encoding steps.
   */
  
  #define JPEG_INTERNALS
  #include "jinclude.h"
  #include "jpeglib.h"
  
  
  /* We use a full-image coefficient buffer when doing Huffman optimization,
   * and also for writing multiple-scan JPEG files.  In all cases, the DCT
   * step is run during the first pass, and subsequent passes need only read
   * the buffered coefficients.
   */
  #ifdef ENTROPY_OPT_SUPPORTED
  #define FULL_COEF_BUFFER_SUPPORTED
  #else
  #ifdef C_MULTISCAN_FILES_SUPPORTED
  #define FULL_COEF_BUFFER_SUPPORTED
  #endif
  #endif
  
  
  /* Private buffer controller object */
  
  typedef struct {
    struct jpeg_c_coef_controller pub; /* public fields */
  
    JDIMENSION iMCU_row_num;  /* iMCU row # within image */
    JDIMENSION mcu_ctr;       /* counts MCUs processed in current row */
    int MCU_vert_offset;      /* counts MCU rows within iMCU row */
    int MCU_rows_per_iMCU_row;    /* number of such rows needed */
  
    /* For single-pass compression, it's sufficient to buffer just one MCU
     * (although this may prove a bit slow in practice).  We allocate a
     * workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each
     * MCU constructed and sent.  (On 80x86, the workspace is FAR even though
     * it's not really very big; this is to keep the module interfaces unchanged
     * when a large coefficient buffer is necessary.)
     * In multi-pass modes, this array points to the current MCU's blocks
     * within the virtual arrays.
     */
    JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU];
  
    /* In multi-pass modes, we need a virtual block array for each component. */
    jvirt_barray_ptr whole_image[MAX_COMPONENTS];
  } my_coef_controller;
  
  typedef my_coef_controller * my_coef_ptr;
  
  
  /* Forward declarations */
  METHODDEF(boolean) compress_data
      JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
  #ifdef FULL_COEF_BUFFER_SUPPORTED
  METHODDEF(boolean) compress_first_pass
      JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
  METHODDEF(boolean) compress_output
      JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
  #endif
  
  
  LOCAL(void)
  start_iMCU_row (j_compress_ptr cinfo)
  /* Reset within-iMCU-row counters for a new row */
  {
    my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
  
    /* In an interleaved scan, an MCU row is the same as an iMCU row.
     * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
     * But at the bottom of the image, process only what's left.
     */
    if (cinfo->comps_in_scan > 1) {
      coef->MCU_rows_per_iMCU_row = 1;
    } else {
      if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1))
        coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
      else
        coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
    }
  
    coef->mcu_ctr = 0;
    coef->MCU_vert_offset = 0;
  }
  
  
  /*
   * Initialize for a processing pass.
   */
  
  METHODDEF(void)
  start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
  {
    my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
  
    coef->iMCU_row_num = 0;
    start_iMCU_row(cinfo);
  
    switch (pass_mode) {
    case JBUF_PASS_THRU:
      if (coef->whole_image[0] != NULL)
        ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
      coef->pub.compress_data = compress_data;
      break;
  #ifdef FULL_COEF_BUFFER_SUPPORTED
    case JBUF_SAVE_AND_PASS:
      if (coef->whole_image[0] == NULL)
        ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
      coef->pub.compress_data = compress_first_pass;
      break;
    case JBUF_CRANK_DEST:
      if (coef->whole_image[0] == NULL)
        ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
      coef->pub.compress_data = compress_output;
      break;
  #endif
    default:
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
      break;
    }
  }
  
  
  /*
   * Process some data in the single-pass case.
   * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
   * per call, ie, v_samp_factor block rows for each component in the image.
   * Returns TRUE if the iMCU row is completed, FALSE if suspended.
   *
   * NB: input_buf contains a plane for each component in image,
   * which we index according to the component's SOF position.
   */
  
  METHODDEF(boolean)
  compress_data (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
  {
    my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
    JDIMENSION MCU_col_num;   /* index of current MCU within row */
    JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
    JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
    int blkn, bi, ci, yindex, yoffset, blockcnt;
    JDIMENSION ypos, xpos;
    jpeg_component_info *compptr;
  
    /* Loop to write as much as one whole iMCU row */
    for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
         yoffset++) {
      for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col;
       MCU_col_num++) {
        /* Determine where data comes from in input_buf and do the DCT thing.
         * Each call on forward_DCT processes a horizontal row of DCT blocks
         * as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks
         * sequentially.  Dummy blocks at the right or bottom edge are filled in
         * specially.  The data in them does not matter for image reconstruction,
         * so we fill them with values that will encode to the smallest amount of
         * data, viz: all zeroes in the AC entries, DC entries equal to previous
         * block's DC value.  (Thanks to Thomas Kinsman for this idea.)
         */
        blkn = 0;
        for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
      compptr = cinfo->cur_comp_info[ci];
      blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
                          : compptr->last_col_width;
      xpos = MCU_col_num * compptr->MCU_sample_width;
      ypos = yoffset * DCTSIZE; /* ypos == (yoffset+yindex) * DCTSIZE */
      for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
        if (coef->iMCU_row_num < last_iMCU_row ||
            yoffset+yindex < compptr->last_row_height) {
          (*cinfo->fdct->forward_DCT) (cinfo, compptr,
                       input_buf[compptr->component_index],
                       coef->MCU_buffer[blkn],
                       ypos, xpos, (JDIMENSION) blockcnt);
          if (blockcnt < compptr->MCU_width) {
            /* Create some dummy blocks at the right edge of the image. */
            jzero_far((void FAR *) coef->MCU_buffer[blkn + blockcnt],
              (compptr->MCU_width - blockcnt) * SIZEOF(JBLOCK));
            for (bi = blockcnt; bi < compptr->MCU_width; bi++) {
          coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn+bi-1][0][0];
            }
          }
        } else {
          /* Create a row of dummy blocks at the bottom of the image. */
          jzero_far((void FAR *) coef->MCU_buffer[blkn],
                compptr->MCU_width * SIZEOF(JBLOCK));
          for (bi = 0; bi < compptr->MCU_width; bi++) {
            coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn-1][0][0];
          }
        }
        blkn += compptr->MCU_width;
        ypos += DCTSIZE;
      }
        }
        /* Try to write the MCU.  In event of a suspension failure, we will
         * re-DCT the MCU on restart (a bit inefficient, could be fixed...)
         */
        if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
      /* Suspension forced; update state counters and exit */
      coef->MCU_vert_offset = yoffset;
      coef->mcu_ctr = MCU_col_num;
      return FALSE;
        }
      }
      /* Completed an MCU row, but perhaps not an iMCU row */
      coef->mcu_ctr = 0;
    }
    /* Completed the iMCU row, advance counters for next one */
    coef->iMCU_row_num++;
    start_iMCU_row(cinfo);
    return TRUE;
  }
  
  
  #ifdef FULL_COEF_BUFFER_SUPPORTED
  
  /*
   * Process some data in the first pass of a multi-pass case.
   * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
   * per call, ie, v_samp_factor block rows for each component in the image.
   * This amount of data is read from the source buffer, DCT'd and quantized,
   * and saved into the virtual arrays.  We also generate suitable dummy blocks
   * as needed at the right and lower edges.  (The dummy blocks are constructed
   * in the virtual arrays, which have been padded appropriately.)  This makes
   * it possible for subsequent passes not to worry about real vs. dummy blocks.
   *
   * We must also emit the data to the entropy encoder.  This is conveniently
   * done by calling compress_output() after we've loaded the current strip
   * of the virtual arrays.
   *
   * NB: input_buf contains a plane for each component in image.  All
   * components are DCT'd and loaded into the virtual arrays in this pass.
   * However, it may be that only a subset of the components are emitted to
   * the entropy encoder during this first pass; be careful about looking
   * at the scan-dependent variables (MCU dimensions, etc).
   */
  
  METHODDEF(boolean)
  compress_first_pass (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
  {
    my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
    JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
    JDIMENSION blocks_across, MCUs_across, MCUindex;
    int bi, ci, h_samp_factor, block_row, block_rows, ndummy;
    JCOEF lastDC;
    jpeg_component_info *compptr;
    JBLOCKARRAY buffer;
    JBLOCKROW thisblockrow, lastblockrow;
  
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
         ci++, compptr++) {
      /* Align the virtual buffer for this component. */
      buffer = (*cinfo->mem->access_virt_barray)
        ((j_common_ptr) cinfo, coef->whole_image[ci],
         coef->iMCU_row_num * compptr->v_samp_factor,
         (JDIMENSION) compptr->v_samp_factor, TRUE);
      /* Count non-dummy DCT block rows in this iMCU row. */
      if (coef->iMCU_row_num < last_iMCU_row)
        block_rows = compptr->v_samp_factor;
      else {
        /* NB: can't use last_row_height here, since may not be set! */
        block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
        if (block_rows == 0) block_rows = compptr->v_samp_factor;
      }
      blocks_across = compptr->width_in_blocks;
      h_samp_factor = compptr->h_samp_factor;
      /* Count number of dummy blocks to be added at the right margin. */
      ndummy = (int) (blocks_across % h_samp_factor);
      if (ndummy > 0)
        ndummy = h_samp_factor - ndummy;
      /* Perform DCT for all non-dummy blocks in this iMCU row.  Each call
       * on forward_DCT processes a complete horizontal row of DCT blocks.
       */
      for (block_row = 0; block_row < block_rows; block_row++) {
        thisblockrow = buffer[block_row];
        (*cinfo->fdct->forward_DCT) (cinfo, compptr,
                     input_buf[ci], thisblockrow,
                     (JDIMENSION) (block_row * DCTSIZE),
                     (JDIMENSION) 0, blocks_across);
        if (ndummy > 0) {
      /* Create dummy blocks at the right edge of the image. */
      thisblockrow += blocks_across; /* => first dummy block */
      jzero_far((void FAR *) thisblockrow, ndummy * SIZEOF(JBLOCK));
      lastDC = thisblockrow[-1][0];
      for (bi = 0; bi < ndummy; bi++) {
        thisblockrow[bi][0] = lastDC;
      }
        }
      }
      /* If at end of image, create dummy block rows as needed.
       * The tricky part here is that within each MCU, we want the DC values
       * of the dummy blocks to match the last real block's DC value.
       * This squeezes a few more bytes out of the resulting file...
       */
      if (coef->iMCU_row_num == last_iMCU_row) {
        blocks_across += ndummy;  /* include lower right corner */
        MCUs_across = blocks_across / h_samp_factor;
        for (block_row = block_rows; block_row < compptr->v_samp_factor;
         block_row++) {
      thisblockrow = buffer[block_row];
      lastblockrow = buffer[block_row-1];
      jzero_far((void FAR *) thisblockrow,
            (size_t) (blocks_across * SIZEOF(JBLOCK)));
      for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) {
        lastDC = lastblockrow[h_samp_factor-1][0];
        for (bi = 0; bi < h_samp_factor; bi++) {
          thisblockrow[bi][0] = lastDC;
        }
        thisblockrow += h_samp_factor; /* advance to next MCU in row */
        lastblockrow += h_samp_factor;
      }
        }
      }
    }
    /* NB: compress_output will increment iMCU_row_num if successful.
     * A suspension return will result in redoing all the work above next time.
     */
  
    /* Emit data to the entropy encoder, sharing code with subsequent passes */
    return compress_output(cinfo, input_buf);
  }
  
  
  /*
   * Process some data in subsequent passes of a multi-pass case.
   * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
   * per call, ie, v_samp_factor block rows for each component in the scan.
   * The data is obtained from the virtual arrays and fed to the entropy coder.
   * Returns TRUE if the iMCU row is completed, FALSE if suspended.
   *
   * NB: input_buf is ignored; it is likely to be a NULL pointer.
   */
  
  METHODDEF(boolean)
  compress_output (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
  {
    my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
    JDIMENSION MCU_col_num;   /* index of current MCU within row */
    int blkn, ci, xindex, yindex, yoffset;
    JDIMENSION start_col;
    JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
    JBLOCKROW buffer_ptr;
    jpeg_component_info *compptr;
  
    /* Align the virtual buffers for the components used in this scan.
     * NB: during first pass, this is safe only because the buffers will
     * already be aligned properly, so jmemmgr.c won't need to do any I/O.
     */
    for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
      compptr = cinfo->cur_comp_info[ci];
      buffer[ci] = (*cinfo->mem->access_virt_barray)
        ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
         coef->iMCU_row_num * compptr->v_samp_factor,
         (JDIMENSION) compptr->v_samp_factor, FALSE);
    }
  
    /* Loop to process one whole iMCU row */
    for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
         yoffset++) {
      for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row;
       MCU_col_num++) {
        /* Construct list of pointers to DCT blocks belonging to this MCU */
        blkn = 0;         /* index of current DCT block within MCU */
        for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
      compptr = cinfo->cur_comp_info[ci];
      start_col = MCU_col_num * compptr->MCU_width;
      for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
        buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
        for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
          coef->MCU_buffer[blkn++] = buffer_ptr++;
        }
      }
        }
        /* Try to write the MCU. */
        if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
      /* Suspension forced; update state counters and exit */
      coef->MCU_vert_offset = yoffset;
      coef->mcu_ctr = MCU_col_num;
      return FALSE;
        }
      }
      /* Completed an MCU row, but perhaps not an iMCU row */
      coef->mcu_ctr = 0;
    }
    /* Completed the iMCU row, advance counters for next one */
    coef->iMCU_row_num++;
    start_iMCU_row(cinfo);
    UNREFERENCED(input_buf);
    return TRUE;
  }
  
  #endif /* FULL_COEF_BUFFER_SUPPORTED */
  
  
  /*
   * Initialize coefficient buffer controller.
   */
  
  GLOBAL(void)
  jinit_c_coef_controller (j_compress_ptr cinfo, boolean need_full_buffer)
  {
    my_coef_ptr coef;
  
    coef = (my_coef_ptr)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                  SIZEOF(my_coef_controller));
    cinfo->coef = (struct jpeg_c_coef_controller *) coef;
    coef->pub.start_pass = start_pass_coef;
  
    /* Create the coefficient buffer. */
    if (need_full_buffer) {
  #ifdef FULL_COEF_BUFFER_SUPPORTED
      /* Allocate a full-image virtual array for each component, */
      /* padded to a multiple of samp_factor DCT blocks in each direction. */
      int ci;
      jpeg_component_info *compptr;
  
      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
        coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
      ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
       (JDIMENSION) jround_up((long) compptr->width_in_blocks,
                  (long) compptr->h_samp_factor),
       (JDIMENSION) jround_up((long) compptr->height_in_blocks,
                  (long) compptr->v_samp_factor),
       (JDIMENSION) compptr->v_samp_factor);
      }
  #else
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
  #endif
    } else {
      /* We only need a single-MCU buffer. */
      JBLOCKROW buffer;
      int i;
  
      buffer = (JBLOCKROW)
        (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                    C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
      for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) {
        coef->MCU_buffer[i] = buffer + i;
      }
      coef->whole_image[0] = NULL; /* flag for no virtual arrays */
    }
  }
  