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src/Source/LibJPEG/jdinput.c  view on Meta::CPAN

 */

METHODDEF(void)
finish_input_pass (j_decompress_ptr cinfo)
{
  (*cinfo->entropy->finish_pass) (cinfo);
  cinfo->inputctl->consume_input = consume_markers;
}


/*
 * Read JPEG markers before, between, or after compressed-data scans.
 * Change state as necessary when a new scan is reached.
 * Return value is JPEG_SUSPENDED, JPEG_REACHED_SOS, or JPEG_REACHED_EOI.
 *
 * The consume_input method pointer points either here or to the
 * coefficient controller's consume_data routine, depending on whether
 * we are reading a compressed data segment or inter-segment markers.
 *
 * Note: This function should NOT return a pseudo SOS marker (with zero
 * component number) to the caller.  A pseudo marker received by
 * read_markers is processed and then skipped for other markers.
 */

METHODDEF(int)
consume_markers (j_decompress_ptr cinfo)
{
  my_inputctl_ptr inputctl = (my_inputctl_ptr) cinfo->inputctl;
  int val;

  if (inputctl->pub.eoi_reached) /* After hitting EOI, read no further */
    return JPEG_REACHED_EOI;

  for (;;) {			/* Loop to pass pseudo SOS marker */
    val = (*cinfo->marker->read_markers) (cinfo);

    switch (val) {
    case JPEG_REACHED_SOS:	/* Found SOS */
      if (inputctl->inheaders) { /* 1st SOS */
	if (inputctl->inheaders == 1)
	  initial_setup(cinfo);
	if (cinfo->comps_in_scan == 0) { /* pseudo SOS marker */
	  inputctl->inheaders = 2;
	  break;
	}
	inputctl->inheaders = 0;
	/* Note: start_input_pass must be called by jdmaster.c
	 * before any more input can be consumed.  jdapimin.c is
	 * responsible for enforcing this sequencing.
	 */
      } else {			/* 2nd or later SOS marker */
	if (! inputctl->pub.has_multiple_scans)
	  ERREXIT(cinfo, JERR_EOI_EXPECTED); /* Oops, I wasn't expecting this! */
	if (cinfo->comps_in_scan == 0) /* unexpected pseudo SOS marker */
	  break;
	start_input_pass(cinfo);
      }
      return val;
    case JPEG_REACHED_EOI:	/* Found EOI */
      inputctl->pub.eoi_reached = TRUE;
      if (inputctl->inheaders) { /* Tables-only datastream, apparently */
	if (cinfo->marker->saw_SOF)
	  ERREXIT(cinfo, JERR_SOF_NO_SOS);
      } else {
	/* Prevent infinite loop in coef ctlr's decompress_data routine
	 * if user set output_scan_number larger than number of scans.
	 */
	if (cinfo->output_scan_number > cinfo->input_scan_number)
	  cinfo->output_scan_number = cinfo->input_scan_number;
      }
      return val;
    case JPEG_SUSPENDED:
      return val;
    default:
      return val;
    }
  }
}


/*
 * Reset state to begin a fresh datastream.
 */

METHODDEF(void)
reset_input_controller (j_decompress_ptr cinfo)
{
  my_inputctl_ptr inputctl = (my_inputctl_ptr) cinfo->inputctl;

  inputctl->pub.consume_input = consume_markers;
  inputctl->pub.has_multiple_scans = FALSE; /* "unknown" would be better */
  inputctl->pub.eoi_reached = FALSE;
  inputctl->inheaders = 1;
  /* Reset other modules */
  (*cinfo->err->reset_error_mgr) ((j_common_ptr) cinfo);
  (*cinfo->marker->reset_marker_reader) (cinfo);
  /* Reset progression state -- would be cleaner if entropy decoder did this */
  cinfo->coef_bits = NULL;
}


/*
 * Initialize the input controller module.
 * This is called only once, when the decompression object is created.
 */

GLOBAL(void)
jinit_input_controller (j_decompress_ptr cinfo)
{
  my_inputctl_ptr inputctl;

  /* Create subobject in permanent pool */
  inputctl = (my_inputctl_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
				SIZEOF(my_input_controller));
  cinfo->inputctl = &inputctl->pub;
  /* Initialize method pointers */
  inputctl->pub.consume_input = consume_markers;
  inputctl->pub.reset_input_controller = reset_input_controller;
  inputctl->pub.start_input_pass = start_input_pass;
  inputctl->pub.finish_input_pass = finish_input_pass;