/*

 * jdcoefct.c

 *

 * This file was part of the Independent JPEG Group's software:

 * Copyright (C) 1994-1997, Thomas G. Lane.

 * libjpeg-turbo Modifications:

 * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB

 * Copyright (C) 2010, 2015-2016, 2019-2020, 2022, D. R. Commander.

 * Copyright (C) 2015, 2020, Google, Inc.

 * For conditions of distribution and use, see the accompanying README.ijg

 * file.

 *

 * This file contains the coefficient buffer controller for decompression.

 * This controller is the top level of the lossy JPEG decompressor proper.

 * The coefficient buffer lies between entropy decoding and inverse-DCT steps.

 *

 * In buffered-image mode, this controller is the interface between

 * input-oriented processing and output-oriented processing.

 * Also, the input side (only) is used when reading a file for transcoding.

 */

#include "jinclude.h"

#include "jdcoefct.h"

#include "jpegapicomp.h"

#include "jsamplecomp.h"

/* Forward declarations */

METHODDEF(int) decompress_onepass(j_decompress_ptr cinfo,

                                  _JSAMPIMAGE output_buf);

#ifdef D_MULTISCAN_FILES_SUPPORTED

METHODDEF(int) decompress_data(j_decompress_ptr cinfo, _JSAMPIMAGE output_buf);

#endif

#ifdef BLOCK_SMOOTHING_SUPPORTED

LOCAL(boolean) smoothing_ok(j_decompress_ptr cinfo);

METHODDEF(int) decompress_smooth_data(j_decompress_ptr cinfo,

                                      _JSAMPIMAGE output_buf);

#endif

/*

 * Initialize for an input processing pass.

 */

METHODDEF(void)

start_input_pass(j_decompress_ptr cinfo)

{

  cinfo->input_iMCU_row = 0;

  start_iMCU_row(cinfo);

}

/*

 * Initialize for an output processing pass.

 */

METHODDEF(void)

start_output_pass(j_decompress_ptr cinfo)

{

#ifdef BLOCK_SMOOTHING_SUPPORTED

  my_coef_ptr coef = (my_coef_ptr)cinfo->coef;

  /* If multipass, check to see whether to use block smoothing on this pass */

  if (coef->pub.coef_arrays != NULL) {

    if (cinfo->do_block_smoothing && smoothing_ok(cinfo))

      coef->pub._decompress_data = decompress_smooth_data;

    else

      coef->pub._decompress_data = decompress_data;

  }

#endif

  cinfo->output_iMCU_row = 0;

}

/*

 * Decompress and return some data in the single-pass case.

 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).

 * Input and output must run in lockstep since we have only a one-MCU buffer.

 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.

 *

 * NB: output_buf contains a plane for each component in image,

 * which we index according to the component's SOF position.

 */

METHODDEF(int)

decompress_onepass(j_decompress_ptr cinfo, _JSAMPIMAGE output_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, ci, xindex, yindex, yoffset, useful_width;

  _JSAMPARRAY output_ptr;

  JDIMENSION start_col, output_col;

  jpeg_component_info *compptr;

  _inverse_DCT_method_ptr inverse_DCT;

  /* Loop to process 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++) {

      /* Try to fetch an MCU.  Entropy decoder expects buffer to be zeroed. */

      jzero_far((void *)coef->MCU_buffer[0],

                (size_t)(cinfo->blocks_in_MCU * sizeof(JBLOCK)));

      if (!cinfo->entropy->insufficient_data)

        cinfo->master->last_good_iMCU_row = cinfo->input_iMCU_row;

      if (!(*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {

        /* Suspension forced; update state counters and exit */

        coef->MCU_vert_offset = yoffset;

        coef->MCU_ctr = MCU_col_num;

        return JPEG_SUSPENDED;

      }

      /* Only perform the IDCT on blocks that are contained within the desired

       * cropping region.

       */

      if (MCU_col_num >= cinfo->master->first_iMCU_col &&

          MCU_col_num <= cinfo->master->last_iMCU_col) {

        /* Determine where data should go in output_buf and do the IDCT thing.

         * We skip dummy blocks at the right and bottom edges (but blkn gets

         * incremented past them!).  Note the inner loop relies on having

         * allocated the MCU_buffer[] blocks sequentially.

         */

        blkn = 0;               /* index of current DCT block within MCU */

        for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

          compptr = cinfo->cur_comp_info[ci];

          /* Don't bother to IDCT an uninteresting component. */

          if (!compptr->component_needed) {

            blkn += compptr->MCU_blocks;

            continue;

          }

          inverse_DCT = cinfo->idct->_inverse_DCT[compptr->component_index];

          useful_width = (MCU_col_num < last_MCU_col) ?

                         compptr->MCU_width : compptr->last_col_width;

          output_ptr = output_buf[compptr->component_index] +

                       yoffset * compptr->_DCT_scaled_size;

          start_col = (MCU_col_num - cinfo->master->first_iMCU_col) *

                      compptr->MCU_sample_width;

          for (yindex = 0; yindex < compptr->MCU_height; yindex++) {

            if (cinfo->input_iMCU_row < last_iMCU_row ||

                yoffset + yindex < compptr->last_row_height) {

              output_col = start_col;

              for (xindex = 0; xindex < useful_width; xindex++) {

                (*inverse_DCT) (cinfo, compptr,

                                (JCOEFPTR)coef->MCU_buffer[blkn + xindex],

                                output_ptr, output_col);

                output_col += compptr->_DCT_scaled_size;

              }

            }

            blkn += compptr->MCU_width;

            output_ptr += compptr->_DCT_scaled_size;

          }

        }

      }

    }

    /* Completed an MCU row, but perhaps not an iMCU row */

    coef->MCU_ctr = 0;

  }

  /* Completed the iMCU row, advance counters for next one */

  cinfo->output_iMCU_row++;

  if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {

    start_iMCU_row(cinfo);

    return JPEG_ROW_COMPLETED;

  }

  /* Completed the scan */

  (*cinfo->inputctl->finish_input_pass) (cinfo);

  return JPEG_SCAN_COMPLETED;

}

/*

 * Dummy consume-input routine for single-pass operation.

 */

METHODDEF(int)

dummy_consume_data(j_decompress_ptr cinfo)

{

  return JPEG_SUSPENDED;        /* Always indicate nothing was done */

}

#ifdef D_MULTISCAN_FILES_SUPPORTED

/*

 * Consume input data and store it in the full-image coefficient buffer.

 * We read as much as one fully interleaved MCU row ("iMCU" row) per call,

 * ie, v_samp_factor block rows for each component in the scan.

 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.

 */

METHODDEF(int)

consume_data(j_decompress_ptr cinfo)

{

  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. */

  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],

       cinfo->input_iMCU_row * compptr->v_samp_factor,

       (JDIMENSION)compptr->v_samp_factor, TRUE);

    /* Note: entropy decoder expects buffer to be zeroed,

     * but this is handled automatically by the memory manager

     * because we requested a pre-zeroed array.

     */

  }

  /* 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++;

          }

        }

      }

      if (!cinfo->entropy->insufficient_data)

        cinfo->master->last_good_iMCU_row = cinfo->input_iMCU_row;

      /* Try to fetch the MCU. */

      if (!(*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {

        /* Suspension forced; update state counters and exit */

        coef->MCU_vert_offset = yoffset;

        coef->MCU_ctr = MCU_col_num;

        return JPEG_SUSPENDED;

      }

    }

    /* Completed an MCU row, but perhaps not an iMCU row */

    coef->MCU_ctr = 0;

  }

  /* Completed the iMCU row, advance counters for next one */

  if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {

    start_iMCU_row(cinfo);

    return JPEG_ROW_COMPLETED;

  }

  /* Completed the scan */

  (*cinfo->inputctl->finish_input_pass) (cinfo);

  return JPEG_SCAN_COMPLETED;

}

/*

 * Decompress and return some data in the multi-pass case.

 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).

 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.

 *

 * NB: output_buf contains a plane for each component in image.

 */

METHODDEF(int)

decompress_data(j_decompress_ptr cinfo, _JSAMPIMAGE output_buf)

{

  my_coef_ptr coef = (my_coef_ptr)cinfo->coef;

  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;

  JDIMENSION block_num;

  int ci, block_row, block_rows;

  JBLOCKARRAY buffer;

  JBLOCKROW buffer_ptr;

  _JSAMPARRAY output_ptr;

  JDIMENSION output_col;

  jpeg_component_info *compptr;

  _inverse_DCT_method_ptr inverse_DCT;

  /* Force some input to be done if we are getting ahead of the input. */

  while (cinfo->input_scan_number < cinfo->output_scan_number ||

         (cinfo->input_scan_number == cinfo->output_scan_number &&

          cinfo->input_iMCU_row <= cinfo->output_iMCU_row)) {

    if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED)

      return JPEG_SUSPENDED;

  }

  /* OK, output from the virtual arrays. */

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

       ci++, compptr++) {

    /* Don't bother to IDCT an uninteresting component. */

    if (!compptr->component_needed)

      continue;

    /* Align the virtual buffer for this component. */

    buffer = (*cinfo->mem->access_virt_barray)

      ((j_common_ptr)cinfo, coef->whole_image[ci],

       cinfo->output_iMCU_row * compptr->v_samp_factor,

       (JDIMENSION)compptr->v_samp_factor, FALSE);

    /* Count non-dummy DCT block rows in this iMCU row. */

    if (cinfo->output_iMCU_row < last_iMCU_row)

      block_rows = compptr->v_samp_factor;

    else {

      /* NB: can't use last_row_height here; it is input-side-dependent! */

      block_rows = (int)(compptr->height_in_blocks % compptr->v_samp_factor);

      if (block_rows == 0) block_rows = compptr->v_samp_factor;

    }

    inverse_DCT = cinfo->idct->_inverse_DCT[ci];

    output_ptr = output_buf[ci];

    /* Loop over all DCT blocks to be processed. */

    for (block_row = 0; block_row < block_rows; block_row++) {

      buffer_ptr = buffer[block_row] + cinfo->master->first_MCU_col[ci];

      output_col = 0;

      for (block_num = cinfo->master->first_MCU_col[ci];

           block_num <= cinfo->master->last_MCU_col[ci]; block_num++) {

        (*inverse_DCT) (cinfo, compptr, (JCOEFPTR)buffer_ptr, output_ptr,

                        output_col);

        buffer_ptr++;

        output_col += compptr->_DCT_scaled_size;

      }

      output_ptr += compptr->_DCT_scaled_size;

    }

  }

  if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)

    return JPEG_ROW_COMPLETED;

  return JPEG_SCAN_COMPLETED;

}

#endif /* D_MULTISCAN_FILES_SUPPORTED */

#ifdef BLOCK_SMOOTHING_SUPPORTED

/*

 * This code applies interblock smoothing; the first 9 AC coefficients are

 * estimated from the DC values of a DCT block and its 24 neighboring blocks.

 * We apply smoothing only for progressive JPEG decoding, and only if

 * the coefficients it can estimate are not yet known to full precision.

 */

/* Natural-order array positions of the first 9 zigzag-order coefficients */

#define Q01_POS  1

#define Q10_POS  8

#define Q20_POS  16

#define Q11_POS  9

#define Q02_POS  2

#define Q03_POS  3

#define Q12_POS  10

#define Q21_POS  17

#define Q30_POS  24

/*

 * Determine whether block smoothing is applicable and safe.

 * We also latch the current states of the coef_bits[] entries for the

 * AC coefficients; otherwise, if the input side of the decompressor

 * advances into a new scan, we might think the coefficients are known

 * more accurately than they really are.

 */

LOCAL(boolean)

smoothing_ok(j_decompress_ptr cinfo)

{

  my_coef_ptr coef = (my_coef_ptr)cinfo->coef;

  boolean smoothing_useful = FALSE;

  int ci, coefi;

  jpeg_component_info *compptr;

  JQUANT_TBL *qtable;

  int *coef_bits, *prev_coef_bits;

  int *coef_bits_latch, *prev_coef_bits_latch;

  if (!cinfo->progressive_mode || cinfo->coef_bits == NULL)

    return FALSE;

  /* Allocate latch area if not already done */

  if (coef->coef_bits_latch == NULL)

    coef->coef_bits_latch = (int *)

      (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,

                                  cinfo->num_components * 2 *

                                  (SAVED_COEFS * sizeof(int)));

  coef_bits_latch = coef->coef_bits_latch;

  prev_coef_bits_latch =

    &coef->coef_bits_latch[cinfo->num_components * SAVED_COEFS];

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

       ci++, compptr++) {

    /* All components' quantization values must already be latched. */

    if ((qtable = compptr->quant_table) == NULL)

      return FALSE;

    /* Verify DC & first 9 AC quantizers are nonzero to avoid zero-divide. */

    if (qtable->quantval[0] == 0 ||

        qtable->quantval[Q01_POS] == 0 ||

        qtable->quantval[Q10_POS] == 0 ||

        qtable->quantval[Q20_POS] == 0 ||

        qtable->quantval[Q11_POS] == 0 ||

        qtable->quantval[Q02_POS] == 0 ||

        qtable->quantval[Q03_POS] == 0 ||

        qtable->quantval[Q12_POS] == 0 ||

        qtable->quantval[Q21_POS] == 0 ||

        qtable->quantval[Q30_POS] == 0)

      return FALSE;

    /* DC values must be at least partly known for all components. */

    coef_bits = cinfo->coef_bits[ci];

    prev_coef_bits = cinfo->coef_bits[ci + cinfo->num_components];

    if (coef_bits[0] < 0)

      return FALSE;

    coef_bits_latch[0] = coef_bits[0];

    /* Block smoothing is helpful if some AC coefficients remain inaccurate. */

    for (coefi = 1; coefi < SAVED_COEFS; coefi++) {

      if (cinfo->input_scan_number > 1)

        prev_coef_bits_latch[coefi] = prev_coef_bits[coefi];

      else

        prev_coef_bits_latch[coefi] = -1;

      coef_bits_latch[coefi] = coef_bits[coefi];

      if (coef_bits[coefi] != 0)

        smoothing_useful = TRUE;

    }

    coef_bits_latch += SAVED_COEFS;

    prev_coef_bits_latch += SAVED_COEFS;

  }

  return smoothing_useful;

}

/*

 * Variant of decompress_data for use when doing block smoothing.

 */

METHODDEF(int)

decompress_smooth_data(j_decompress_ptr cinfo, _JSAMPIMAGE output_buf)

{

  my_coef_ptr coef = (my_coef_ptr)cinfo->coef;

  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;

  JDIMENSION block_num, last_block_column;

  int ci, block_row, block_rows, access_rows;

  JBLOCKARRAY buffer;

  JBLOCKROW buffer_ptr, prev_prev_block_row, prev_block_row;

  JBLOCKROW next_block_row, next_next_block_row;

  _JSAMPARRAY output_ptr;

  JDIMENSION output_col;

  jpeg_component_info *compptr;

  _inverse_DCT_method_ptr inverse_DCT;

  boolean change_dc;

  JCOEF *workspace;

  int *coef_bits;

  JQUANT_TBL *quanttbl;

  JLONG Q00, Q01, Q02, Q03 = 0, Q10, Q11, Q12 = 0, Q20, Q21 = 0, Q30 = 0, num;

  int DC01, DC02, DC03, DC04, DC05, DC06, DC07, DC08, DC09, DC10, DC11, DC12,

      DC13, DC14, DC15, DC16, DC17, DC18, DC19, DC20, DC21, DC22, DC23, DC24,

      DC25;

  int Al, pred;

  /* Keep a local variable to avoid looking it up more than once */

  workspace = coef->workspace;

  /* Force some input to be done if we are getting ahead of the input. */

  while (cinfo->input_scan_number <= cinfo->output_scan_number &&

         !cinfo->inputctl->eoi_reached) {

    if (cinfo->input_scan_number == cinfo->output_scan_number) {

      /* If input is working on current scan, we ordinarily want it to

       * have completed the current row.  But if input scan is DC,

       * we want it to keep two rows ahead so that next two block rows' DC

       * values are up to date.

       */

      JDIMENSION delta = (cinfo->Ss == 0) ? 2 : 0;

      if (cinfo->input_iMCU_row > cinfo->output_iMCU_row + delta)

        break;

    }

    if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED)

      return JPEG_SUSPENDED;

  }

  /* OK, output from the virtual arrays. */

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

       ci++, compptr++) {

    /* Don't bother to IDCT an uninteresting component. */

    if (!compptr->component_needed)

      continue;

    /* Count non-dummy DCT block rows in this iMCU row. */

    if (cinfo->output_iMCU_row + 1 < last_iMCU_row) {

      block_rows = compptr->v_samp_factor;

      access_rows = block_rows * 3; /* this and next two iMCU rows */

    } else if (cinfo->output_iMCU_row < last_iMCU_row) {

      block_rows = compptr->v_samp_factor;

      access_rows = block_rows * 2; /* this and next iMCU row */

    } else {

      /* NB: can't use last_row_height here; it is input-side-dependent! */

      block_rows = (int)(compptr->height_in_blocks % compptr->v_samp_factor);

      if (block_rows == 0) block_rows = compptr->v_samp_factor;

      access_rows = block_rows; /* this iMCU row only */

    }

    /* Align the virtual buffer for this component. */

    if (cinfo->output_iMCU_row > 1) {

      access_rows += 2 * compptr->v_samp_factor; /* prior two iMCU rows too */

      buffer = (*cinfo->mem->access_virt_barray)

        ((j_common_ptr)cinfo, coef->whole_image[ci],

         (cinfo->output_iMCU_row - 2) * compptr->v_samp_factor,

         (JDIMENSION)access_rows, FALSE);

      buffer += 2 * compptr->v_samp_factor; /* point to current iMCU row */

    } else if (cinfo->output_iMCU_row > 0) {

      buffer = (*cinfo->mem->access_virt_barray)

        ((j_common_ptr)cinfo, coef->whole_image[ci],

         (cinfo->output_iMCU_row - 1) * compptr->v_samp_factor,

         (JDIMENSION)access_rows, FALSE);

      buffer += compptr->v_samp_factor; /* point to current iMCU row */

    } else {

      buffer = (*cinfo->mem->access_virt_barray)

        ((j_common_ptr)cinfo, coef->whole_image[ci],

         (JDIMENSION)0, (JDIMENSION)access_rows, FALSE);

    }

    /* Fetch component-dependent info.

     * If the current scan is incomplete, then we use the component-dependent

     * info from the previous scan.

     */

    if (cinfo->output_iMCU_row > cinfo->master->last_good_iMCU_row)

      coef_bits =

        coef->coef_bits_latch + ((ci + cinfo->num_components) * SAVED_COEFS);

    else

      coef_bits = coef->coef_bits_latch + (ci * SAVED_COEFS);

    /* We only do DC interpolation if no AC coefficient data is available. */

    change_dc =

      coef_bits[1] == -1 && coef_bits[2] == -1 && coef_bits[3] == -1 &&

      coef_bits[4] == -1 && coef_bits[5] == -1 && coef_bits[6] == -1 &&

      coef_bits[7] == -1 && coef_bits[8] == -1 && coef_bits[9] == -1;

    quanttbl = compptr->quant_table;

    Q00 = quanttbl->quantval[0];

    Q01 = quanttbl->quantval[Q01_POS];

    Q10 = quanttbl->quantval[Q10_POS];

    Q20 = quanttbl->quantval[Q20_POS];

    Q11 = quanttbl->quantval[Q11_POS];

    Q02 = quanttbl->quantval[Q02_POS];

    if (change_dc) {

      Q03 = quanttbl->quantval[Q03_POS];

      Q12 = quanttbl->quantval[Q12_POS];

      Q21 = quanttbl->quantval[Q21_POS];

      Q30 = quanttbl->quantval[Q30_POS];

    }

    inverse_DCT = cinfo->idct->_inverse_DCT[ci];

    output_ptr = output_buf[ci];

    /* Loop over all DCT blocks to be processed. */

    for (block_row = 0; block_row < block_rows; block_row++) {

      buffer_ptr = buffer[block_row] + cinfo->master->first_MCU_col[ci];

      if (block_row > 0 || cinfo->output_iMCU_row > 0)

        prev_block_row =

          buffer[block_row - 1] + cinfo->master->first_MCU_col[ci];

      else

        prev_block_row = buffer_ptr;

      if (block_row > 1 || cinfo->output_iMCU_row > 1)

        prev_prev_block_row =

          buffer[block_row - 2] + cinfo->master->first_MCU_col[ci];

      else

        prev_prev_block_row = prev_block_row;

      if (block_row < block_rows - 1 || cinfo->output_iMCU_row < last_iMCU_row)

        next_block_row =

          buffer[block_row + 1] + cinfo->master->first_MCU_col[ci];

      else

        next_block_row = buffer_ptr;

      if (block_row < block_rows - 2 ||

          cinfo->output_iMCU_row + 1 < last_iMCU_row)

        next_next_block_row =

          buffer[block_row + 2] + cinfo->master->first_MCU_col[ci];

      else

        next_next_block_row = next_block_row;

      /* We fetch the surrounding DC values using a sliding-register approach.

       * Initialize all 25 here so as to do the right thing on narrow pics.

       */

      DC01 = DC02 = DC03 = DC04 = DC05 = (int)prev_prev_block_row[0][0];

      DC06 = DC07 = DC08 = DC09 = DC10 = (int)prev_block_row[0][0];

      DC11 = DC12 = DC13 = DC14 = DC15 = (int)buffer_ptr[0][0];

      DC16 = DC17 = DC18 = DC19 = DC20 = (int)next_block_row[0][0];

      DC21 = DC22 = DC23 = DC24 = DC25 = (int)next_next_block_row[0][0];

      output_col = 0;

      last_block_column = compptr->width_in_blocks - 1;

      for (block_num = cinfo->master->first_MCU_col[ci];

           block_num <= cinfo->master->last_MCU_col[ci]; block_num++) {

        /* Fetch current DCT block into workspace so we can modify it. */

        jcopy_block_row(buffer_ptr, (JBLOCKROW)workspace, (JDIMENSION)1);

        /* Update DC values */

        if (block_num == cinfo->master->first_MCU_col[ci] &&

            block_num < last_block_column) {

          DC04 = (int)prev_prev_block_row[1][0];

          DC09 = (int)prev_block_row[1][0];

          DC14 = (int)buffer_ptr[1][0];

          DC19 = (int)next_block_row[1][0];

          DC24 = (int)next_next_block_row[1][0];

        }

        if (block_num + 1 < last_block_column) {

          DC05 = (int)prev_prev_block_row[2][0];

          DC10 = (int)prev_block_row[2][0];

          DC15 = (int)buffer_ptr[2][0];

          DC20 = (int)next_block_row[2][0];

          DC25 = (int)next_next_block_row[2][0];

        }

        /* If DC interpolation is enabled, compute coefficient estimates using

         * a Gaussian-like kernel, keeping the averages of the DC values.

         *

         * If DC interpolation is disabled, compute coefficient estimates using

         * an algorithm similar to the one described in Section K.8 of the JPEG

         * standard, except applied to a 5x5 window rather than a 3x3 window.

         *

         * An estimate is applied only if the coefficient is still zero and is

         * not known to be fully accurate.

         */

        /* AC01 */

        if ((Al = coef_bits[1]) != 0 && workspace[1] == 0) {

          num = Q00 * (change_dc ?

                (-DC01 - DC02 + DC04 + DC05 - 3 * DC06 + 13 * DC07 -

                 13 * DC09 + 3 * DC10 - 3 * DC11 + 38 * DC12 - 38 * DC14 +

                 3 * DC15 - 3 * DC16 + 13 * DC17 - 13 * DC19 + 3 * DC20 -

                 DC21 - DC22 + DC24 + DC25) :

                (-7 * DC11 + 50 * DC12 - 50 * DC14 + 7 * DC15));

          if (num >= 0) {

            pred = (int)(((Q01 << 7) + num) / (Q01 << 8));

            if (Al > 0 && pred >= (1 << Al))

              pred = (1 << Al) - 1;

          } else {

            pred = (int)(((Q01 << 7) - num) / (Q01 << 8));

            if (Al > 0 && pred >= (1 << Al))

              pred = (1 << Al) - 1;

            pred = -pred;

          }

          workspace[1] = (JCOEF)pred;

        }

        /* AC10 */

        if ((Al = coef_bits[2]) != 0 && workspace[8] == 0) {

          num = Q00 * (change_dc ?

                (-DC01 - 3 * DC02 - 3 * DC03 - 3 * DC04 - DC05 - DC06 +

                 13 * DC07 + 38 * DC08 + 13 * DC09 - DC10 + DC16 -

                 13 * DC17 - 38 * DC18 - 13 * DC19 + DC20 + DC21 +

                 3 * DC22 + 3 * DC23 + 3 * DC24 + DC25) :

                (-7 * DC03 + 50 * DC08 - 50 * DC18 + 7 * DC23));

          if (num >= 0) {

            pred = (int)(((Q10 << 7) + num) / (Q10 << 8));

            if (Al > 0 && pred >= (1 << Al))

              pred = (1 << Al) - 1;

          } else {

            pred = (int)(((Q10 << 7) - num) / (Q10 << 8));

            if (Al > 0 && pred >= (1 << Al))

              pred = (1 << Al) - 1;

            pred = -pred;

          }

          workspace[8] = (JCOEF)pred;

        }

        /* AC20 */

        if ((Al = coef_bits[3]) != 0 && workspace[16] == 0) {

          num = Q00 * (change_dc ?

                (DC03 + 2 * DC07 + 7 * DC08 + 2 * DC09 - 5 * DC12 - 14 * DC13 -

                 5 * DC14 + 2 * DC17 + 7 * DC18 + 2 * DC19 + DC23) :

                (-DC03 + 13 * DC08 - 24 * DC13 + 13 * DC18 - DC23));

          if (num >= 0) {

            pred = (int)(((Q20 << 7) + num) / (Q20 << 8));

            if (Al > 0 && pred >= (1 << Al))

              pred = (1 << Al) - 1;

          } else {

            pred = (int)(((Q20 << 7) - num) / (Q20 << 8));

            if (Al > 0 && pred >= (1 << Al))

              pred = (1 << Al) - 1;

            pred = -pred;

          }

          workspace[16] = (JCOEF)pred;

        }

        /* AC11 */

        if ((Al = coef_bits[4]) != 0 && workspace[9] == 0) {

          num = Q00 * (change_dc ?

                (-DC01 + DC05 + 9 * DC07 - 9 * DC09 - 9 * DC17 +

                 9 * DC19 + DC21 - DC25) :

                (DC10 + DC16 - 10 * DC17 + 10 * DC19 - DC02 - DC20 + DC22 -

                 DC24 + DC04 - DC06 + 10 * DC07 - 10 * DC09));

          if (num >= 0) {

            pred = (int)(((Q11 << 7) + num) / (Q11 << 8));

            if (Al > 0 && pred >= (1 << Al))

              pred = (1 << Al) - 1;

          } else {

            pred = (int)(((Q11 << 7) - num) / (Q11 << 8));

            if (Al > 0 && pred >= (1 << Al))

              pred = (1 << Al) - 1;

            pred = -pred;

          }

          workspace[9] = (JCOEF)pred;

        }

        /* AC02 */

        if ((Al = coef_bits[5]) != 0 && workspace[2] == 0) {

          num = Q00 * (change_dc ?

                (2 * DC07 - 5 * DC08 + 2 * DC09 + DC11 + 7 * DC12 - 14 * DC13 +

                 7 * DC14 + DC15 + 2 * DC17 - 5 * DC18 + 2 * DC19) :

                (-DC11 + 13 * DC12 - 24 * DC13 + 13 * DC14 - DC15));

          if (num >= 0) {

            pred = (int)(((Q02 << 7) + num) / (Q02 << 8));

            if (Al > 0 && pred >= (1 << Al))

              pred = (1 << Al) - 1;

          } else {

            pred = (int)(((Q02 << 7) - num) / (Q02 << 8));

            if (Al > 0 && pred >= (1 << Al))

              pred = (1 << Al) - 1;

            pred = -pred;

          }

          workspace[2] = (JCOEF)pred;

        }

        if (change_dc) {

          /* AC03 */

          if ((Al = coef_bits[6]) != 0 && workspace[3] == 0) {

            num = Q00 * (DC07 - DC09 + 2 * DC12 - 2 * DC14 + DC17 - DC19);

            if (num >= 0) {

              pred = (int)(((Q03 << 7) + num) / (Q03 << 8));

              if (Al > 0 && pred >= (1 << Al))

                pred = (1 << Al) - 1;

            } else {

              pred = (int)(((Q03 << 7) - num) / (Q03 << 8));

              if (Al > 0 && pred >= (1 << Al))

                pred = (1 << Al) - 1;

              pred = -pred;

            }

            workspace[3] = (JCOEF)pred;

          }

          /* AC12 */

          if ((Al = coef_bits[7]) != 0 && workspace[10] == 0) {

            num = Q00 * (DC07 - 3 * DC08 + DC09 - DC17 + 3 * DC18 - DC19);

            if (num >= 0) {

              pred = (int)(((Q12 << 7) + num) / (Q12 << 8));

              if (Al > 0 && pred >= (1 << Al))

                pred = (1 << Al) - 1;

            } else {

              pred = (int)(((Q12 << 7) - num) / (Q12 << 8));

              if (Al > 0 && pred >= (1 << Al))

                pred = (1 << Al) - 1;

              pred = -pred;

            }

            workspace[10] = (JCOEF)pred;

          }

          /* AC21 */

          if ((Al = coef_bits[8]) != 0 && workspace[17] == 0) {

            num = Q00 * (DC07 - DC09 - 3 * DC12 + 3 * DC14 + DC17 - DC19);

            if (num >= 0) {

              pred = (int)(((Q21 << 7) + num) / (Q21 << 8));

              if (Al > 0 && pred >= (1 << Al))

                pred = (1 << Al) - 1;

            } else {

              pred = (int)(((Q21 << 7) - num) / (Q21 << 8));

              if (Al > 0 && pred >= (1 << Al))

                pred = (1 << Al) - 1;

              pred = -pred;

            }

            workspace[17] = (JCOEF)pred;

          }

          /* AC30 */

          if ((Al = coef_bits[9]) != 0 && workspace[24] == 0) {

            num = Q00 * (DC07 + 2 * DC08 + DC09 - DC17 - 2 * DC18 - DC19);

            if (num >= 0) {

              pred = (int)(((Q30 << 7) + num) / (Q30 << 8));

              if (Al > 0 && pred >= (1 << Al))

                pred = (1 << Al) - 1;

            } else {

              pred = (int)(((Q30 << 7) - num) / (Q30 << 8));

              if (Al > 0 && pred >= (1 << Al))

                pred = (1 << Al) - 1;

              pred = -pred;

            }

            workspace[24] = (JCOEF)pred;

          }

          /* coef_bits[0] is non-negative.  Otherwise this function would not

           * be called.

           */

          num = Q00 *

                (-2 * DC01 - 6 * DC02 - 8 * DC03 - 6 * DC04 - 2 * DC05 -

                 6 * DC06 + 6 * DC07 + 42 * DC08 + 6 * DC09 - 6 * DC10 -

                 8 * DC11 + 42 * DC12 + 152 * DC13 + 42 * DC14 - 8 * DC15 -

                 6 * DC16 + 6 * DC17 + 42 * DC18 + 6 * DC19 - 6 * DC20 -

                 2 * DC21 - 6 * DC22 - 8 * DC23 - 6 * DC24 - 2 * DC25);

          if (num >= 0) {

            pred = (int)(((Q00 << 7) + num) / (Q00 << 8));

          } else {

            pred = (int)(((Q00 << 7) - num) / (Q00 << 8));

            pred = -pred;

          }

          workspace[0] = (JCOEF)pred;

        }  /* change_dc */

        /* OK, do the IDCT */

        (*inverse_DCT) (cinfo, compptr, (JCOEFPTR)workspace, output_ptr,

                        output_col);

        /* Advance for next column */

        DC01 = DC02;  DC02 = DC03;  DC03 = DC04;  DC04 = DC05;

        DC06 = DC07;  DC07 = DC08;  DC08 = DC09;  DC09 = DC10;

        DC11 = DC12;  DC12 = DC13;  DC13 = DC14;  DC14 = DC15;

        DC16 = DC17;  DC17 = DC18;  DC18 = DC19;  DC19 = DC20;

        DC21 = DC22;  DC22 = DC23;  DC23 = DC24;  DC24 = DC25;

        buffer_ptr++, prev_block_row++, next_block_row++,

          prev_prev_block_row++, next_next_block_row++;

        output_col += compptr->_DCT_scaled_size;

      }

      output_ptr += compptr->_DCT_scaled_size;

    }

  }

  if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)

    return JPEG_ROW_COMPLETED;

  return JPEG_SCAN_COMPLETED;

}

#endif /* BLOCK_SMOOTHING_SUPPORTED */

/*

 * Initialize coefficient buffer controller.

 */

GLOBAL(void)

_jinit_d_coef_controller(j_decompress_ptr cinfo, boolean need_full_buffer)

{

  my_coef_ptr coef;

  if (cinfo->data_precision != BITS_IN_JSAMPLE)

    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);

  coef = (my_coef_ptr)

    (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,

                                sizeof(my_coef_controller));

  cinfo->coef = (struct jpeg_d_coef_controller *)coef;

  coef->pub.start_input_pass = start_input_pass;

  coef->pub.start_output_pass = start_output_pass;

#ifdef BLOCK_SMOOTHING_SUPPORTED

  coef->coef_bits_latch = NULL;

#endif

  /* Create the coefficient buffer. */

  if (need_full_buffer) {

#ifdef D_MULTISCAN_FILES_SUPPORTED

    /* Allocate a full-image virtual array for each component, */

    /* padded to a multiple of samp_factor DCT blocks in each direction. */

    /* Note we ask for a pre-zeroed array. */

    int ci, access_rows;

    jpeg_component_info *compptr;

    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

         ci++, compptr++) {

      access_rows = compptr->v_samp_factor;

#ifdef BLOCK_SMOOTHING_SUPPORTED

      /* If block smoothing could be used, need a bigger window */

      if (cinfo->progressive_mode)

        access_rows *= 5;

#endif

      coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)

        ((j_common_ptr)cinfo, JPOOL_IMAGE, TRUE,

         (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)access_rows);

    }

    coef->pub.consume_data = consume_data;

    coef->pub._decompress_data = decompress_data;

    coef->pub.coef_arrays = coef->whole_image; /* link to virtual arrays */

#else

    ERREXIT(cinfo, JERR_NOT_COMPILED);

#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,

                                  D_MAX_BLOCKS_IN_MCU * sizeof(JBLOCK));

    for (i = 0; i < D_MAX_BLOCKS_IN_MCU; i++) {

      coef->MCU_buffer[i] = buffer + i;

    }

    coef->pub.consume_data = dummy_consume_data;

    coef->pub._decompress_data = decompress_onepass;

    coef->pub.coef_arrays = NULL; /* flag for no virtual arrays */

  }

  /* Allocate the workspace buffer */

  coef->workspace = (JCOEF *)

    (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,