/src/libjpeg-turbo.main/src/jcmainct.c

Source
/*
 * jcmainct.c
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * Lossless JPEG Modifications:
 * Copyright (C) 1999, Ken Murchison.
 * libjpeg-turbo Modifications:
 * Copyright (C) 2022, 2024, D. R. Commander.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file contains the main buffer controller for compression.
 * The main buffer lies between the pre-processor and the JPEG
 * compressor proper; it holds downsampled data in the JPEG colorspace.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jsamplecomp.h"


#if BITS_IN_JSAMPLE != 16 || defined(C_LOSSLESS_SUPPORTED)

/* Private buffer controller object */

typedef struct {
  struct jpeg_c_main_controller pub; /* public fields */

  JDIMENSION cur_iMCU_row;      /* number of current iMCU row */
  JDIMENSION rowgroup_ctr;      /* counts row groups received in iMCU row */
  boolean suspended;            /* remember if we suspended output */
  J_BUF_MODE pass_mode;         /* current operating mode */

  /* If using just a strip buffer, this points to the entire set of buffers
   * (we allocate one for each component).  In the full-image case, this
   * points to the currently accessible strips of the virtual arrays.
   */
  _JSAMPARRAY buffer[MAX_COMPONENTS];
} my_main_controller;

typedef my_main_controller *my_main_ptr;


/* Forward declarations */
METHODDEF(void) process_data_simple_main(j_compress_ptr cinfo,
                                         _JSAMPARRAY input_buf,
                                         JDIMENSION *in_row_ctr,
                                         JDIMENSION in_rows_avail);


/*
 * Initialize for a processing pass.
 */

METHODDEF(void)
start_pass_main(j_compress_ptr cinfo, J_BUF_MODE pass_mode)
{
  my_main_ptr main_ptr = (my_main_ptr)cinfo->main;

  /* Do nothing in raw-data mode. */
  if (cinfo->raw_data_in)
    return;

  if (pass_mode != JBUF_PASS_THRU)
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);

  main_ptr->cur_iMCU_row = 0;   /* initialize counters */
  main_ptr->rowgroup_ctr = 0;
  main_ptr->suspended = FALSE;
  main_ptr->pass_mode = pass_mode;      /* save mode for use by process_data */
  main_ptr->pub._process_data = process_data_simple_main;
}


/*
 * Process some data.
 * This routine handles the simple pass-through mode,
 * where we have only a strip buffer.
 */

METHODDEF(void)
process_data_simple_main(j_compress_ptr cinfo, _JSAMPARRAY input_buf,
                         JDIMENSION *in_row_ctr, JDIMENSION in_rows_avail)
{
  my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
  JDIMENSION data_unit = cinfo->master->lossless ? 1 : DCTSIZE;

  while (main_ptr->cur_iMCU_row < cinfo->total_iMCU_rows) {
    /* Read input data if we haven't filled the main buffer yet */
    if (main_ptr->rowgroup_ctr < data_unit)
      (*cinfo->prep->_pre_process_data) (cinfo, input_buf, in_row_ctr,
                                         in_rows_avail, main_ptr->buffer,
                                         &main_ptr->rowgroup_ctr, data_unit);

    /* If we don't have a full iMCU row buffered, return to application for
     * more data.  Note that preprocessor will always pad to fill the iMCU row
     * at the bottom of the image.
     */
    if (main_ptr->rowgroup_ctr != data_unit)
      return;

    /* Send the completed row to the compressor */
    if (!(*cinfo->coef->_compress_data) (cinfo, main_ptr->buffer)) {
      /* If compressor did not consume the whole row, then we must need to
       * suspend processing and return to the application.  In this situation
       * we pretend we didn't yet consume the last input row; otherwise, if
       * it happened to be the last row of the image, the application would
       * think we were done.
       */
      if (!main_ptr->suspended) {
        (*in_row_ctr)--;
        main_ptr->suspended = TRUE;
      }
      return;
    }
    /* We did finish the row.  Undo our little suspension hack if a previous
     * call suspended; then mark the main buffer empty.
     */
    if (main_ptr->suspended) {
      (*in_row_ctr)++;
      main_ptr->suspended = FALSE;
    }
    main_ptr->rowgroup_ctr = 0;
    main_ptr->cur_iMCU_row++;
  }
}


/*
 * Initialize main buffer controller.
 */

GLOBAL(void)
_jinit_c_main_controller(j_compress_ptr cinfo, boolean need_full_buffer)
{
  my_main_ptr main_ptr;
  int ci;
  jpeg_component_info *compptr;
  int data_unit = cinfo->master->lossless ? 1 : DCTSIZE;

#ifdef C_LOSSLESS_SUPPORTED
  if (cinfo->master->lossless) {
#if BITS_IN_JSAMPLE == 8
    if (cinfo->data_precision > BITS_IN_JSAMPLE || cinfo->data_precision < 2)
#else
    if (cinfo->data_precision > BITS_IN_JSAMPLE ||
        cinfo->data_precision < BITS_IN_JSAMPLE - 3)
#endif
      ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
  } else
#endif
  {
    if (cinfo->data_precision != BITS_IN_JSAMPLE)
      ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
  }

  main_ptr = (my_main_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
                                sizeof(my_main_controller));
  memset(main_ptr, 0, sizeof(my_main_controller));
  cinfo->main = (struct jpeg_c_main_controller *)main_ptr;
  main_ptr->pub.start_pass = start_pass_main;

  /* We don't need to create a buffer in raw-data mode. */
  if (cinfo->raw_data_in)
    return;

  /* Create the buffer.  It holds downsampled data, so each component
   * may be of a different size.
   */
  if (need_full_buffer) {
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
  } else {
    /* Allocate a strip buffer for each component */
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
         ci++, compptr++) {
      main_ptr->buffer[ci] = (_JSAMPARRAY)(*cinfo->mem->alloc_sarray)
        ((j_common_ptr)cinfo, JPOOL_IMAGE,
         compptr->width_in_blocks * data_unit,
         (JDIMENSION)(compptr->v_samp_factor * data_unit));
    }
  }
}

#endif /* BITS_IN_JSAMPLE != 16 || defined(C_LOSSLESS_SUPPORTED) */

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Created: 2026-03-12 08:02