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

LOCAL(void)
do_barray_io (j_common_ptr cinfo, jvirt_barray_ptr ptr, boolean writing)
/* Do backing store read or write of a virtual coefficient-block array */
{
  long bytesperrow, file_offset, byte_count, rows, thisrow, i;

  bytesperrow = (long) ptr->blocksperrow * SIZEOF(JBLOCK);
  file_offset = ptr->cur_start_row * bytesperrow;
  /* Loop to read or write each allocation chunk in mem_buffer */
  for (i = 0; i < (long) ptr->rows_in_mem; i += ptr->rowsperchunk) {
    /* One chunk, but check for short chunk at end of buffer */
    rows = MIN((long) ptr->rowsperchunk, (long) ptr->rows_in_mem - i);
    /* Transfer no more than is currently defined */
    thisrow = (long) ptr->cur_start_row + i;
    rows = MIN(rows, (long) ptr->first_undef_row - thisrow);
    /* Transfer no more than fits in file */
    rows = MIN(rows, (long) ptr->rows_in_array - thisrow);
    if (rows <= 0)		/* this chunk might be past end of file! */
      break;
    byte_count = rows * bytesperrow;
    if (writing)
      (*ptr->b_s_info.write_backing_store) (cinfo, & ptr->b_s_info,
					    (void FAR *) ptr->mem_buffer[i],
					    file_offset, byte_count);
    else
      (*ptr->b_s_info.read_backing_store) (cinfo, & ptr->b_s_info,
					   (void FAR *) ptr->mem_buffer[i],
					   file_offset, byte_count);
    file_offset += byte_count;
  }
}


METHODDEF(JSAMPARRAY)
access_virt_sarray (j_common_ptr cinfo, jvirt_sarray_ptr ptr,
		    JDIMENSION start_row, JDIMENSION num_rows,
		    boolean writable)
/* Access the part of a virtual sample array starting at start_row */
/* and extending for num_rows rows.  writable is true if  */
/* caller intends to modify the accessed area. */
{
  JDIMENSION end_row = start_row + num_rows;
  JDIMENSION undef_row;

  /* debugging check */
  if (end_row > ptr->rows_in_array || num_rows > ptr->maxaccess ||
      ptr->mem_buffer == NULL)
    ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);

  /* Make the desired part of the virtual array accessible */
  if (start_row < ptr->cur_start_row ||
      end_row > ptr->cur_start_row+ptr->rows_in_mem) {
    if (! ptr->b_s_open)
      ERREXIT(cinfo, JERR_VIRTUAL_BUG);
    /* Flush old buffer contents if necessary */
    if (ptr->dirty) {
      do_sarray_io(cinfo, ptr, TRUE);
      ptr->dirty = FALSE;
    }
    /* Decide what part of virtual array to access.
     * Algorithm: if target address > current window, assume forward scan,
     * load starting at target address.  If target address < current window,
     * assume backward scan, load so that target area is top of window.
     * Note that when switching from forward write to forward read, will have
     * start_row = 0, so the limiting case applies and we load from 0 anyway.
     */
    if (start_row > ptr->cur_start_row) {
      ptr->cur_start_row = start_row;
    } else {
      /* use long arithmetic here to avoid overflow & unsigned problems */
      long ltemp;

      ltemp = (long) end_row - (long) ptr->rows_in_mem;
      if (ltemp < 0)
	ltemp = 0;		/* don't fall off front end of file */
      ptr->cur_start_row = (JDIMENSION) ltemp;
    }
    /* Read in the selected part of the array.
     * During the initial write pass, we will do no actual read
     * because the selected part is all undefined.
     */
    do_sarray_io(cinfo, ptr, FALSE);
  }
  /* Ensure the accessed part of the array is defined; prezero if needed.
   * To improve locality of access, we only prezero the part of the array
   * that the caller is about to access, not the entire in-memory array.
   */
  if (ptr->first_undef_row < end_row) {
    if (ptr->first_undef_row < start_row) {
      if (writable)		/* writer skipped over a section of array */
	ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
      undef_row = start_row;	/* but reader is allowed to read ahead */
    } else {
      undef_row = ptr->first_undef_row;
    }
    if (writable)
      ptr->first_undef_row = end_row;
    if (ptr->pre_zero) {
      size_t bytesperrow = (size_t) ptr->samplesperrow * SIZEOF(JSAMPLE);
      undef_row -= ptr->cur_start_row; /* make indexes relative to buffer */
      end_row -= ptr->cur_start_row;
      while (undef_row < end_row) {
	FMEMZERO((void FAR *) ptr->mem_buffer[undef_row], bytesperrow);
	undef_row++;
      }
    } else {
      if (! writable)		/* reader looking at undefined data */
	ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
    }
  }
  /* Flag the buffer dirty if caller will write in it */
  if (writable)
    ptr->dirty = TRUE;
  /* Return address of proper part of the buffer */
  return ptr->mem_buffer + (start_row - ptr->cur_start_row);
}


METHODDEF(JBLOCKARRAY)
access_virt_barray (j_common_ptr cinfo, jvirt_barray_ptr ptr,
		    JDIMENSION start_row, JDIMENSION num_rows,
		    boolean writable)
/* Access the part of a virtual block array starting at start_row */
/* and extending for num_rows rows.  writable is true if  */
/* caller intends to modify the accessed area. */
{
  JDIMENSION end_row = start_row + num_rows;
  JDIMENSION undef_row;

  /* debugging check */
  if (end_row > ptr->rows_in_array || num_rows > ptr->maxaccess ||
      ptr->mem_buffer == NULL)
    ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);

  /* Make the desired part of the virtual array accessible */
  if (start_row < ptr->cur_start_row ||
      end_row > ptr->cur_start_row+ptr->rows_in_mem) {
    if (! ptr->b_s_open)
      ERREXIT(cinfo, JERR_VIRTUAL_BUG);
    /* Flush old buffer contents if necessary */
    if (ptr->dirty) {
      do_barray_io(cinfo, ptr, TRUE);
      ptr->dirty = FALSE;
    }
    /* Decide what part of virtual array to access.
     * Algorithm: if target address > current window, assume forward scan,
     * load starting at target address.  If target address < current window,
     * assume backward scan, load so that target area is top of window.
     * Note that when switching from forward write to forward read, will have
     * start_row = 0, so the limiting case applies and we load from 0 anyway.
     */
    if (start_row > ptr->cur_start_row) {
      ptr->cur_start_row = start_row;
    } else {
      /* use long arithmetic here to avoid overflow & unsigned problems */
      long ltemp;

      ltemp = (long) end_row - (long) ptr->rows_in_mem;
      if (ltemp < 0)
	ltemp = 0;		/* don't fall off front end of file */
      ptr->cur_start_row = (JDIMENSION) ltemp;
    }
    /* Read in the selected part of the array.
     * During the initial write pass, we will do no actual read
     * because the selected part is all undefined.
     */
    do_barray_io(cinfo, ptr, FALSE);
  }
  /* Ensure the accessed part of the array is defined; prezero if needed.
   * To improve locality of access, we only prezero the part of the array
   * that the caller is about to access, not the entire in-memory array.
   */
  if (ptr->first_undef_row < end_row) {
    if (ptr->first_undef_row < start_row) {
      if (writable)		/* writer skipped over a section of array */
	ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
      undef_row = start_row;	/* but reader is allowed to read ahead */
    } else {
      undef_row = ptr->first_undef_row;
    }
    if (writable)
      ptr->first_undef_row = end_row;
    if (ptr->pre_zero) {
      size_t bytesperrow = (size_t) ptr->blocksperrow * SIZEOF(JBLOCK);
      undef_row -= ptr->cur_start_row; /* make indexes relative to buffer */
      end_row -= ptr->cur_start_row;
      while (undef_row < end_row) {
	FMEMZERO((void FAR *) ptr->mem_buffer[undef_row], bytesperrow);
	undef_row++;
      }
    } else {
      if (! writable)		/* reader looking at undefined data */
	ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
    }
  }
  /* Flag the buffer dirty if caller will write in it */
  if (writable)
    ptr->dirty = TRUE;
  /* Return address of proper part of the buffer */
  return ptr->mem_buffer + (start_row - ptr->cur_start_row);
}


/*
 * Release all objects belonging to a specified pool.