/* $Id: tif_thunder.c,v 1.4 2005/11/19 16:02:59 malaterre Exp $ */

/*
 * Copyright (c) 1988-1997 Sam Leffler
 * Copyright (c) 1991-1997 Silicon Graphics, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software and 
 * its documentation for any purpose is hereby granted without fee, provided
 * that (i) the above copyright notices and this permission notice appear in
 * all copies of the software and related documentation, and (ii) the names of
 * Sam Leffler and Silicon Graphics may not be used in any advertising or
 * publicity relating to the software without the specific, prior written
 * permission of Sam Leffler and Silicon Graphics.
 * 
 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY 
 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  
 * 
 * IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
 * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
 * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF 
 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 
 * OF THIS SOFTWARE.
 */

#include "tiffiop.h"
#ifdef THUNDER_SUPPORT
/*
 * TIFF Library.
 *
 * ThunderScan 4-bit Compression Algorithm Support
 */

/*
 * ThunderScan uses an encoding scheme designed for
 * 4-bit pixel values.  Data is encoded in bytes, with
 * each byte split into a 2-bit code word and a 6-bit
 * data value.  The encoding gives raw data, runs of
 * pixels, or pixel values encoded as a delta from the
 * previous pixel value.  For the latter, either 2-bit
 * or 3-bit delta values are used, with the deltas packed
 * into a single byte.
 */
#define  THUNDER_DATA    0x3f  /* mask for 6-bit data */
#define  THUNDER_CODE    0xc0  /* mask for 2-bit code word */
/* code values */
#define  THUNDER_RUN    0x00  /* run of pixels w/ encoded count */
#define  THUNDER_2BITDELTAS  0x40  /* 3 pixels w/ encoded 2-bit deltas */
#define      DELTA2_SKIP    2  /* skip code for 2-bit deltas */
#define  THUNDER_3BITDELTAS  0x80  /* 2 pixels w/ encoded 3-bit deltas */
#define      DELTA3_SKIP    4  /* skip code for 3-bit deltas */
#define  THUNDER_RAW    0xc0  /* raw data encoded */

static const int twobitdeltas[4] = { 0, 1, 0, -1 };
static const int threebitdeltas[8] = { 0, 1, 2, 3, 0, -3, -2, -1 };

#define  SETPIXEL(op, v) { \
  lastpixel = (v) & 0xf; \
  if (npixels++ & 1) \
      *op++ |= lastpixel; \
  else \
      op[0] = (tidataval_t) (lastpixel << 4); \
}

static int
ThunderDecode(TIFF* tif, tidata_t op, tsize_t maxpixels)
{
  register unsigned char *bp;
  register tsize_t cc;
  unsigned int lastpixel;
  tsize_t npixels;

  bp = (unsigned char *)tif->tif_rawcp;
  cc = tif->tif_rawcc;
  lastpixel = 0;
  npixels = 0;
  while (cc > 0 && npixels < maxpixels) {
    int n, delta;

    n = *bp++, cc--;
    switch (n & THUNDER_CODE) {
    case THUNDER_RUN:    /* pixel run */
      /*
       * Replicate the last pixel n times,
       * where n is the lower-order 6 bits.
       */
      if (npixels & 1) {
        op[0] |= lastpixel;
        lastpixel = *op++; npixels++; n--;
      } else
        lastpixel |= lastpixel << 4;
      npixels += n;
      if (npixels < maxpixels) {
        for (; n > 0; n -= 2)
          *op++ = (tidataval_t) lastpixel;
      }
      if (n == -1)
        *--op &= 0xf0;
      lastpixel &= 0xf;
      break;
    case THUNDER_2BITDELTAS:  /* 2-bit deltas */
      if ((delta = ((n >> 4) & 3)) != DELTA2_SKIP)
        SETPIXEL(op, lastpixel + twobitdeltas[delta]);
      if ((delta = ((n >> 2) & 3)) != DELTA2_SKIP)
        SETPIXEL(op, lastpixel + twobitdeltas[delta]);
      if ((delta = (n & 3)) != DELTA2_SKIP)
        SETPIXEL(op, lastpixel + twobitdeltas[delta]);
      break;
    case THUNDER_3BITDELTAS:  /* 3-bit deltas */
      if ((delta = ((n >> 3) & 7)) != DELTA3_SKIP)
        SETPIXEL(op, lastpixel + threebitdeltas[delta]);
      if ((delta = (n & 7)) != DELTA3_SKIP)
        SETPIXEL(op, lastpixel + threebitdeltas[delta]);
      break;
    case THUNDER_RAW:    /* raw data */
      SETPIXEL(op, n);
      break;
    }
  }
  tif->tif_rawcp = (tidata_t) bp;
  tif->tif_rawcc = cc;
  if (npixels != maxpixels) {
    TIFFError(tif->tif_name,
        "ThunderDecode: %s data at scanline %ld (%lu != %lu)",
        npixels < maxpixels ? "Not enough" : "Too much",
        (long) tif->tif_row, (long) npixels, (long) maxpixels);
    return (0);
  }
  return (1);
}

static int
ThunderDecodeRow(TIFF* tif, tidata_t buf, tsize_t occ, tsample_t s)
{
  tidata_t row = buf;
  
  (void) s;
  while ((long)occ > 0) {
    if (!ThunderDecode(tif, row, tif->tif_dir.td_imagewidth))
      return (0);
    occ -= tif->tif_scanlinesize;
    row += tif->tif_scanlinesize;
  }
  return (1);
}

int
TIFFInitThunderScan(TIFF* tif, int scheme)
{
  (void) scheme;
  tif->tif_decoderow = ThunderDecodeRow;
  tif->tif_decodestrip = ThunderDecodeRow;
  return (1);
}
#endif /* THUNDER_SUPPORT */

