JPEGView/Independent JPEG Group/jcmainct.c

/*
 * jcmainct.c
 *
 * Copyright (C) 1994, 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 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"


/* Private buffer controller object */

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

  JDIMENSION cur_mcu_row;	/* number of current MCU row */
  JDIMENSION rowgroup_ctr;	/* counts row groups received in MCU row */
  JDIMENSION mcu_ctr;		/* counts MCUs output from current row */
  boolean suspended;		/* remember if we suspended output */
  J_BUF_MODE pass_mode;		/* current operating mode */

  /* If using full-image storage, this array holds pointers to virtual-array
   * control blocks for each component.  Unused if not full-image storage.
   */
  jvirt_sarray_ptr virtual[MAX_COMPONENTS];
  /* If using just a strip buffer, this points to the entire set of buffers
   * (we allocate one for each component).  In the virtual-array case, this
   * points to the currently accessible strips of the virtual arrays.
   */
  JSAMPARRAY buffer[MAX_COMPONENTS];
  /* This vector points to the current strips of the components being written
   * during the current scan.
   */
  JSAMPARRAY cur_buffer[MAX_COMPS_IN_SCAN];
} my_main_controller;

typedef my_main_controller * my_main_ptr;


/* Forward declarations */
METHODDEF void process_data_simple_main
	JPP((j_compress_ptr cinfo, JSAMPARRAY input_buf,
	     JDIMENSION *in_row_ctr, JDIMENSION in_rows_avail));
METHODDEF void process_data_buffer_main
	JPP((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 = (my_main_ptr) cinfo->main;
  int ci, cindex;

  main->cur_mcu_row = 0;	/* initialize counters */
  main->rowgroup_ctr = 0;
  main->mcu_ctr = 0;
  main->suspended = FALSE;
  main->pass_mode = pass_mode;	/* save mode for use by process_data */

  switch (pass_mode) {
  case JBUF_PASS_THRU:
    if (main->virtual[0] != NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    main->pub.process_data = process_data_simple_main;
    /* The output-strip pointers can be set up once for the whole pass. */
    for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
      cindex = cinfo->cur_comp_info[ci]->component_index;
      main->cur_buffer[ci] = main->buffer[cindex];
    }
    break;
  case JBUF_SAVE_SOURCE:
  case JBUF_CRANK_DEST:
  case JBUF_SAVE_AND_PASS:
    if (main->virtual[0] == NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    main->pub.process_data = process_data_buffer_main;
    break;
  default:
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    break;
  }
}


/*
 * 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 = (my_main_ptr) cinfo->main;

  while (*in_row_ctr < in_rows_avail) {
    /* Read input data if we haven't filled the main buffer yet */
    if (main->rowgroup_ctr < DCTSIZE)
      (*cinfo->prep->pre_process_data) (cinfo,
					input_buf, in_row_ctr, in_rows_avail,
					main->buffer, &main->rowgroup_ctr,
					(JDIMENSION) DCTSIZE);

    /* If we have a full MCU row buffered, emit data. */
    /* Note that preprocessor ensures this will be true at bottom of image. */
    if (main->rowgroup_ctr == DCTSIZE) {
      (*cinfo->coef->compress_data) (cinfo, main->cur_buffer, &main->mcu_ctr);
      /* 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 co