}
  return 1;
}

/*
 * Targa also defines a 32-bit pixel format with order B,G,R,A.
 * We presently ignore the attribute byte, so the code for reading
 * these pixels is identical to the 24-bit routine above.
 * This works because the actual pixel length is only known to read_pixel.
 */

#define get_32bit_row  get_24bit_row


/*
 * This method is for re-reading the input data in standard top-down
 * row order.  The entire image has already been read into whole_image
 * with proper conversion of pixel format, but it's in a funny row order.
 */

METHODDEF(JDIMENSION)
get_memory_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
{
  tga_source_ptr source = (tga_source_ptr) sinfo;
  JDIMENSION source_row;

  /* Compute row of source that maps to current_row of normal order */
  /* For now, assume image is bottom-up and not interlaced. */
  /* NEEDS WORK to support interlaced images! */
  source_row = cinfo->image_height - source->current_row - 1;

  /* Fetch that row from virtual array */
  source->pub.buffer = (*cinfo->mem->access_virt_sarray)
    ((j_common_ptr) cinfo, source->whole_image,
     source_row, (JDIMENSION) 1, FALSE);

  source->current_row++;
  return 1;
}


/*
 * This method loads the image into whole_image during the first call on
 * get_pixel_rows.  The get_pixel_rows pointer is then adjusted to call
 * get_memory_row on subsequent calls.
 */

METHODDEF(JDIMENSION)
preload_image (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
{
  tga_source_ptr source = (tga_source_ptr) sinfo;
  JDIMENSION row;
  cd_progress_ptr progress = (cd_progress_ptr) cinfo->progress;

  /* Read the data into a virtual array in input-file row order. */
  for (row = 0; row < cinfo->image_height; row++) {
    if (progress != NULL) {
      progress->pub.pass_counter = (long) row;
      progress->pub.pass_limit = (long) cinfo->image_height;
      (*progress->pub.progress_monitor) ((j_common_ptr) cinfo);
    }
    source->pub.buffer = (*cinfo->mem->access_virt_sarray)
      ((j_common_ptr) cinfo, source->whole_image, row, (JDIMENSION) 1, TRUE);
    (*source->get_pixel_rows) (cinfo, sinfo);
  }
  if (progress != NULL)
    progress->completed_extra_passes++;

  /* Set up to read from the virtual array in unscrambled order */
  source->pub.get_pixel_rows = get_memory_row;
  source->current_row = 0;
  /* And read the first row */
  return get_memory_row(cinfo, sinfo);
}


/*
 * Read the file header; return image size and component count.
 */

METHODDEF(void)
start_input_tga (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
{
  tga_source_ptr source = (tga_source_ptr) sinfo;
  U_CHAR targaheader[18];
  int idlen, cmaptype, subtype, flags, interlace_type, components;
  unsigned int width, height, maplen;
  boolean is_bottom_up;

#define GET_2B(offset)	((unsigned int) UCH(targaheader[offset]) + \
			 (((unsigned int) UCH(targaheader[offset+1])) << 8))

  if (! ReadOK(source->pub.input_file, targaheader, 18))
    ERREXIT(cinfo, JERR_INPUT_EOF);

  /* Pretend "15-bit" pixels are 16-bit --- we ignore attribute bit anyway */
  if (targaheader[16] == 15)
    targaheader[16] = 16;

  idlen = UCH(targaheader[0]);
  cmaptype = UCH(targaheader[1]);
  subtype = UCH(targaheader[2]);
  maplen = GET_2B(5);
  width = GET_2B(12);
  height = GET_2B(14);
  source->pixel_size = UCH(targaheader[16]) >> 3;
  flags = UCH(targaheader[17]);	/* Image Descriptor byte */

  is_bottom_up = ((flags & 0x20) == 0);	/* bit 5 set => top-down */
  interlace_type = flags >> 6;	/* bits 6/7 are interlace code */

  if (cmaptype > 1 ||		/* cmaptype must be 0 or 1 */
      source->pixel_size < 1 || source->pixel_size > 4 ||
      (UCH(targaheader[16]) & 7) != 0 || /* bits/pixel must be multiple of 8 */
      interlace_type != 0)	/* currently don't allow interlaced image */
    ERREXIT(cinfo, JERR_TGA_BADPARMS);
  
  if (subtype > 8) {
    /* It's an RLE-coded file */
    source->read_pixel = read_rle_pixel;
    source->block_count = source->dup_pixel_count = 0;
    subtype -= 8;
  } else {
    /* Non-RLE file */
    source->read_pixel = read_non_rle_pixel;
  }

  /* Now should have subtype 1, 2, or 3 */
  components = 3;		/* until proven different */
  cinfo->in_color_space = JCS_RGB;

  switch (subtype) {
  case 1:			/* Colormapped image */
    if (source->pixel_size == 1 && cmaptype == 1)
      source->get_pixel_rows = get_8bit_row;
    else
      ERREXIT(cinfo, JERR_TGA_BADPARMS);
    TRACEMS2(cinfo, 1, JTRC_TGA_MAPPED, width, height);
    break;
  case 2:			/* RGB image */
    switch (source->pixel_size) {
    case 2:
      source->get_pixel_rows = get_16bit_row;
      break;
    case 3:
      source->get_pixel_rows = get_24bit_row;
      break;
    case 4:
      source->get_pixel_rows = get_32bit_row;
      break;
    default:
      ERREXIT(cinfo, JERR_TGA_BADPARMS);
      break;
    }
    TRACEMS2(cinfo, 1, JTRC_TGA, width, height);
    break;
  case 3:			/* Grayscale image */
    components = 1;
    cinfo->in_color_space = JCS_GRAYSCALE;
    if (source->pixel_size == 1)
      source->get_pixel_rows = get_8bit_gray_row;
    else
      ERREXIT(cinfo, JERR_TGA_BADPARMS);
    TRACEMS2(cinfo, 1, JTRC_TGA_GRAY, width, height);
    break;
  default:
    ERREXIT(cinfo, JERR_TGA_BADPARMS);
    break;
  }

  if (is_bottom_up) {
    /* Create a virtual array to buffer the upside-down image. */
    source->whole_image = (*cinfo->mem->request_virt_sarray)
      ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
       (JDIMENSION) width * components, (JDIMENSION) height, (JDIMENSION) 1);
    if (cinfo->progress != NULL) {
      cd_progress_ptr progress = (cd_progress_ptr) cinfo->progress;
      progress->total_extra_passes++; /* count file input as separate pass */
    }
    /* source->pub.buffer will point to the virtual array. */
    source->pub.buffer_height = 1; /* in case anyone looks at it */
    source->pub.get_pixel_rows = preload_image;
  } else {
    /* Don't need a virtual array, but do need a one-row input buffer. */
    source->whole_image = NULL;
    source->pub.buffer = (*cinfo->mem->alloc_sarray)
      ((j_common_ptr) cinfo, JPOOL_IMAGE,
       (JDIMENSION) width * components, (JDIMENSION) 1);
    source->pub.buffer_height = 1;
    source->pub.get_pixel_rows = source->get_pixel_rows;
  }
  
  while (idlen--)		/* Throw away ID field */
    (void) read_byte(source);

  if (maplen > 0) {
    if (maplen > 256 || GET_2B(3) != 0)
      ERREXIT(cinfo, JERR_TGA_BADCMAP);
    /* Allocate space to store the colormap */
    source->colormap = (*cinfo->mem->alloc_sarray)
      ((j_common_ptr) cinfo, JPOOL_IMAGE, (JDIMENSION) maplen, (JDIMENSION) 3);
    /* and read it from the file */
    read_colormap(source, (int) maplen, UCH(targaheader[7]));
  } else {
    if (cmaptype)		/* but you promised a cmap! */
      ERREXIT(cinfo, JERR_TGA_BADPARMS);
    source->colormap = NULL;
  }

  cinfo->input_components = components;
  cinfo->data_precision = 8;
  cinfo->image_width = width;
  cinfo->image_height = height;
}


/*
 * Finish up at the end of the file.
 */

METHODDEF(void)
finish_input_tga (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
{
  /* no work */
}


/*
 * The module selection routine for Targa format input.
 */

GLOBAL(cjpeg_source_ptr)
jinit_read_targa (j_compress_ptr cinfo)
{
  tga_source_ptr source;

  /* Create module interface object */
  source = (tga_source_ptr)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				  SIZEOF(tga_source_struct));
  source->cinfo = cinfo;	/* make back link for subroutines */
  /* Fill in method ptrs, except get_pixel_rows which start_input sets */
  source->pub.start_input = start_input_tga;
  source->pub.finish_input = finish_input_tga;

  return (cjpeg_source_ptr) source;
}

#endif /* TARGA_SUPPORTED */