/*

 * 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"

#include <assert.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 < maxpixels )         \

        {                                     \

    if (npixels++ & 1)                  \

      *op++ |= lastpixel;               \

    else                                \

      op[0] = (uint8_t) (lastpixel << 4); \

        }                                     \

}

static int

ThunderSetupDecode(TIFF* tif)

{

  static const char module[] = "ThunderSetupDecode";

        if( tif->tif_dir.td_bitspersample != 4 )

        {

                TIFFErrorExt(tif->tif_clientdata, module,

                             "Wrong bitspersample value (%d), Thunder decoder only supports 4bits per sample.",

                             (int) tif->tif_dir.td_bitspersample );

                return 0;

        }

  return (1);

}

static int

ThunderDecode(TIFF* tif, uint8_t* op, tmsize_t maxpixels)

{

  static const char module[] = "ThunderDecode";

  register unsigned char *bp;

  register tmsize_t cc;

  unsigned int lastpixel;

  tmsize_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++ = (uint8_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, (unsigned)((int)lastpixel + twobitdeltas[delta]));

      if ((delta = ((n >> 2) & 3)) != DELTA2_SKIP)

        SETPIXEL(op, (unsigned)((int)lastpixel + twobitdeltas[delta]));

      if ((delta = (n & 3)) != DELTA2_SKIP)

        SETPIXEL(op, (unsigned)((int)lastpixel + twobitdeltas[delta]));

      break;

    case THUNDER_3BITDELTAS: /* 3-bit deltas */

      if ((delta = ((n >> 3) & 7)) != DELTA3_SKIP)

        SETPIXEL(op, (unsigned)((int)lastpixel + threebitdeltas[delta]));

      if ((delta = (n & 7)) != DELTA3_SKIP)

        SETPIXEL(op, (unsigned)((int)lastpixel + threebitdeltas[delta]));

      break;

    case THUNDER_RAW:   /* raw data */

      SETPIXEL(op, n);

      break;

    }

  }

  tif->tif_rawcp = (uint8_t*) bp;

  tif->tif_rawcc = cc;

  if (npixels != maxpixels) {

    TIFFErrorExt(tif->tif_clientdata, module,

           "%s data at scanline %lu (%"PRIu64" != %"PRIu64")",

           npixels < maxpixels ? "Not enough" : "Too much",

           (unsigned long) tif->tif_row,

           (uint64_t) npixels,

           (uint64_t) maxpixels);

    return (0);

  }

        return (1);

}

static int

ThunderDecodeRow(TIFF* tif, uint8_t* buf, tmsize_t occ, uint16_t s)

{

  static const char module[] = "ThunderDecodeRow";

  uint8_t* row = buf;

  (void) s;

  if (occ % tif->tif_scanlinesize)

  {

    TIFFErrorExt(tif->tif_clientdata, module, "Fractional scanlines cannot be read");

    return (0);

  }

  while (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_setupdecode = ThunderSetupDecode;

  tif->tif_decoderow = ThunderDecodeRow;

  tif->tif_decodestrip = ThunderDecodeRow; 

  return (1);

}

#endif /* THUNDER_SUPPORT */

/* vim: set ts=8 sts=8 sw=8 noet: */

/*

 * Local Variables:

 * mode: c

 * c-basic-offset: 8

 * fill-column: 78

 * End:

 */