source: bootcd/isolinux/syslinux-6.03/com32/lib/jpeg/tinyjpeg.c @ e16e8f2

/*
 * Small jpeg decoder library
 *
 * Copyright (c) 2006, Luc Saillard <luc@saillard.org>
 * All rights reserved.
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *  this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright notice,
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 *
 * - Neither the name of the author nor the names of its contributors may be
 *  used to endorse or promote products derived from this software without
 *  specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <errno.h>

#include "tinyjpeg.h"
#include "tinyjpeg-internal.h"

/* Global variable to return the last error found while deconding */
static char error_string[256];

static const unsigned char zigzag[64] =
{
   0,  1,  5,  6, 14, 15, 27, 28,
   2,  4,  7, 13, 16, 26, 29, 42,
   3,  8, 12, 17, 25, 30, 41, 43,
   9, 11, 18, 24, 31, 40, 44, 53,
  10, 19, 23, 32, 39, 45, 52, 54,
  20, 22, 33, 38, 46, 51, 55, 60,
  21, 34, 37, 47, 50, 56, 59, 61,
  35, 36, 48, 49, 57, 58, 62, 63
};

/* Set up the standard Huffman tables (cf. JPEG standard section K.3) */
/* IMPORTANT: these are only valid for 8-bit data precision! */
static const unsigned char bits_dc_luminance[17] =
{
  0, 0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0
};
static const unsigned char val_dc_luminance[] =
{
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
};

static const unsigned char bits_dc_chrominance[17] =
{
  0, 0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0
};
static const unsigned char val_dc_chrominance[] =
{
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
};

static const unsigned char bits_ac_luminance[17] =
{
  0, 0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 0x7d
};
static const unsigned char val_ac_luminance[] =
{
  0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12,
  0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07,
  0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xa1, 0x08,
  0x23, 0x42, 0xb1, 0xc1, 0x15, 0x52, 0xd1, 0xf0,
  0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0a, 0x16,
  0x17, 0x18, 0x19, 0x1a, 0x25, 0x26, 0x27, 0x28,
  0x29, 0x2a, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
  0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49,
  0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59,
  0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69,
  0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79,
  0x7a, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89,
  0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98,
  0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
  0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6,
  0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 0xc4, 0xc5,
  0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, 0xd3, 0xd4,
  0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe1, 0xe2,
  0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea,
  0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
  0xf9, 0xfa
};

static const unsigned char bits_ac_chrominance[17] =
{
  0, 0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 0x77
};

static const unsigned char val_ac_chrominance[] =
{
  0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21,
  0x31, 0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71,
  0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91,
  0xa1, 0xb1, 0xc1, 0x09, 0x23, 0x33, 0x52, 0xf0,
  0x15, 0x62, 0x72, 0xd1, 0x0a, 0x16, 0x24, 0x34,
  0xe1, 0x25, 0xf1, 0x17, 0x18, 0x19, 0x1a, 0x26,
  0x27, 0x28, 0x29, 0x2a, 0x35, 0x36, 0x37, 0x38,
  0x39, 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,
  0x49, 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,
  0x59, 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,
  0x69, 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
  0x79, 0x7a, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
  0x88, 0x89, 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96,
  0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5,
  0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4,
  0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3,
  0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2,
  0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda,
  0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9,
  0xea, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
  0xf9, 0xfa
};


/*
 * 4 functions to manage the stream
 *
 *  fill_nbits: put at least nbits in the reservoir of bits.
 *              But convert any 0xff,0x00 into 0xff
 *  get_nbits: read nbits from the stream, and put it in result,
 *             bits is removed from the stream and the reservoir is filled
 *             automaticaly. The result is signed according to the number of
 *             bits.
 *  look_nbits: read nbits from the stream without marking as read.
 *  skip_nbits: read nbits from the stream but do not return the result.
 *
 * stream: current pointer in the jpeg data (read bytes per bytes)
 * nbits_in_reservoir: number of bits filled into the reservoir
 * reservoir: register that contains bits information. Only nbits_in_reservoir
 *            is valid.
 *                          nbits_in_reservoir
 *                        <--    17 bits    -->
 *            Ex: 0000 0000 1010 0000 1111 0000   <== reservoir
 *                        ^
 *                        bit 1
 *            To get two bits from this example
 *                 result = (reservoir >> 15) & 3
 *
 */
#define fill_nbits(reservoir,nbits_in_reservoir,stream,nbits_wanted) do { \
   while (nbits_in_reservoir<nbits_wanted) \
    { \
      unsigned char c; \
      if (stream >= priv->stream_end) \
        longjmp(priv->jump_state, -EIO); \
      c = *stream++; \
      reservoir <<= 8; \
      if (c == 0xff && *stream == 0x00) \
        stream++; \
      reservoir |= c; \
      nbits_in_reservoir+=8; \
    } \
}  while(0);

/* Signed version !!!! */
#define get_nbits(reservoir,nbits_in_reservoir,stream,nbits_wanted,result) do { \
   fill_nbits(reservoir,nbits_in_reservoir,stream,(nbits_wanted)); \
   result = ((reservoir)>>(nbits_in_reservoir-(nbits_wanted))); \
   nbits_in_reservoir -= (nbits_wanted);  \
   reservoir &= ((1U<<nbits_in_reservoir)-1); \
   if ((unsigned int)result < (1UL<<((nbits_wanted)-1))) \
       result += (0xFFFFFFFFUL<<(nbits_wanted))+1; \
}  while(0);

#define look_nbits(reservoir,nbits_in_reservoir,stream,nbits_wanted,result) do { \
   fill_nbits(reservoir,nbits_in_reservoir,stream,(nbits_wanted)); \
   result = ((reservoir)>>(nbits_in_reservoir-(nbits_wanted))); \
}  while(0);

/* To speed up the decoding, we assume that the reservoir have enough bit 
 * slow version:
 * #define skip_nbits(reservoir,nbits_in_reservoir,stream,nbits_wanted) do { \
 *   fill_nbits(reservoir,nbits_in_reservoir,stream,(nbits_wanted)); \
 *   nbits_in_reservoir -= (nbits_wanted); \
 *   reservoir &= ((1U<<nbits_in_reservoir)-1); \
 * }  while(0);
 */
#define skip_nbits(reservoir,nbits_in_reservoir,stream,nbits_wanted) do { \
   nbits_in_reservoir -= (nbits_wanted); \
   reservoir &= ((1U<<nbits_in_reservoir)-1); \
}  while(0);


#define be16_to_cpu(x) (((x)[0]<<8)|(x)[1])

static void resync(struct jdec_private *priv);

/**
 * Get the next (valid) huffman code in the stream.
 *
 * To speedup the procedure, we look HUFFMAN_HASH_NBITS bits and the code is
 * lower than HUFFMAN_HASH_NBITS we have automaticaly the length of the code
 * and the value by using two lookup table.
 * Else if the value is not found, just search (linear) into an array for each
 * bits is the code is present.
 *
 * If the code is not present for any reason, -1 is return.
 */
static int get_next_huffman_code(struct jdec_private *priv, struct huffman_table *huffman_table)
{
  int value, hcode;
  unsigned int extra_nbits, nbits;
  uint16_t *slowtable;

  look_nbits(priv->reservoir, priv->nbits_in_reservoir, priv->stream, HUFFMAN_HASH_NBITS, hcode);
  value = huffman_table->lookup[hcode];
  if (__likely(value >= 0))
  {
     unsigned int code_size = huffman_table->code_size[value];
     skip_nbits(priv->reservoir, priv->nbits_in_reservoir, priv->stream, code_size);
     return value;
  }

  /* Decode more bits each time ... */
  for (extra_nbits=0; extra_nbits<16-HUFFMAN_HASH_NBITS; extra_nbits++)
   {
     nbits = HUFFMAN_HASH_NBITS + 1 + extra_nbits;

     look_nbits(priv->reservoir, priv->nbits_in_reservoir, priv->stream, nbits, hcode);
     slowtable = huffman_table->slowtable[extra_nbits];
     /* Search if the code is in this array */
     while (slowtable[0]) {
        if (slowtable[0] == hcode) {
           skip_nbits(priv->reservoir, priv->nbits_in_reservoir, priv->stream, nbits);
           return slowtable[1];
        }
        slowtable+=2;
     }
   }
  return 0;
}




/**
 *
 * Decode a single block that contains the DCT coefficients.
 * The table coefficients is already dezigzaged at the end of the operation.
 *
 */
void tinyjpeg_process_Huffman_data_unit(struct jdec_private *priv, int component)
{
  unsigned char j;
  unsigned int huff_code;
  unsigned char size_val, count_0;

  struct component *c = &priv->component_infos[component];
  short int DCT[64];


  /* Initialize the DCT coef table */
  memset(DCT, 0, sizeof(DCT));

  /* DC coefficient decoding */
  huff_code = get_next_huffman_code(priv, c->DC_table);
  //trace("+ %x\n", huff_code);
  if (huff_code) {
     get_nbits(priv->reservoir, priv->nbits_in_reservoir, priv->stream, huff_code, DCT[0]);
     DCT[0] += c->previous_DC;
     c->previous_DC = DCT[0];
  } else {
     DCT[0] = c->previous_DC;
  }

  /* AC coefficient decoding */
  j = 1;
  while (j<64)
   {
     huff_code = get_next_huffman_code(priv, c->AC_table);
     //trace("- %x\n", huff_code);

     size_val = huff_code & 0xF;
     count_0 = huff_code >> 4;

     if (size_val == 0)
      { /* RLE */
        if (count_0 == 0)
          break;        /* EOB found, go out */
        else if (count_0 == 0xF)
          j += 16;      /* skip 16 zeros */
      }
     else
      {
        j += count_0;   /* skip count_0 zeroes */
        if (__unlikely(j >= 64))
         {
           snprintf(error_string, sizeof(error_string), "Bad huffman data (buffer overflow)");
           break;
         }
        get_nbits(priv->reservoir, priv->nbits_in_reservoir, priv->stream, size_val, DCT[j]);
        j++;
      }
   }

  for (j = 0; j < 64; j++)
    c->DCT[j] = DCT[zigzag[j]];
}

/*
 * Takes two array of bits, and build the huffman table for size, and code
 *
 * lookup will return the symbol if the code is less or equal than HUFFMAN_HASH_NBITS.
 * code_size will be used to known how many bits this symbol is encoded.
 * slowtable will be used when the first lookup didn't give the result.
 */
static void build_huffman_table(const unsigned char *bits, const unsigned char *vals, struct huffman_table *table)
{
  unsigned int i, j, code, code_size, val, nbits;
  unsigned char huffsize[HUFFMAN_BITS_SIZE+1], *hz;
  unsigned int huffcode[HUFFMAN_BITS_SIZE+1], *hc;

  /*
   * Build a temp array
   *   huffsize[X] => numbers of bits to write vals[X]
   */
  hz = huffsize;
  for (i=1; i<=16; i++)
   {
     for (j=1; j<=bits[i]; j++)
       *hz++ = i;
   }
  *hz = 0;

  memset(table->lookup, 0xff, sizeof(table->lookup));
  for (i=0; i<(16-HUFFMAN_HASH_NBITS); i++)
    table->slowtable[i][0] = 0;

  /* Build a temp array
   *   huffcode[X] => code used to write vals[X]
   */
  code = 0;
  hc = huffcode;
  hz = huffsize;
  nbits = *hz;
  while (*hz)
   {
     while (*hz == nbits)
      {
        *hc++ = code++;
        hz++;
      }
     code <<= 1;
     nbits++;
   }

  /*
   * Build the lookup table, and the slowtable if needed.
   */
  for (i=0; huffsize[i]; i++)
   {
     val = vals[i];
     code = huffcode[i];
     code_size = huffsize[i];

     trace("val=%2.2x code=%8.8x codesize=%2.2d\n", val, code, code_size);

     table->code_size[val] = code_size;
     if (code_size <= HUFFMAN_HASH_NBITS)
      {
        /*
         * Good: val can be put in the lookup table, so fill all value of this
         * column with value val
         */
        int repeat = 1UL<<(HUFFMAN_HASH_NBITS - code_size);
        code <<= HUFFMAN_HASH_NBITS - code_size;
        while ( repeat-- )
          table->lookup[code++] = val;

      }
     else
      {
        /* Perhaps sorting the array will be an optimization */
        uint16_t *slowtable = table->slowtable[code_size-HUFFMAN_HASH_NBITS-1];
        while(slowtable[0])
          slowtable+=2;
        slowtable[0] = code;
        slowtable[1] = val;
        slowtable[2] = 0;
        /* TODO: NEED TO CHECK FOR AN OVERFLOW OF THE TABLE */
      }

   }
}

static void build_default_huffman_tables(struct jdec_private *priv)
{
  if (   (priv->flags & TINYJPEG_FLAGS_MJPEG_TABLE)
      && priv->default_huffman_table_initialized)
    return;

  build_huffman_table(bits_dc_luminance, val_dc_luminance, &priv->HTDC[0]);
  build_huffman_table(bits_ac_luminance, val_ac_luminance, &priv->HTAC[0]);

  build_huffman_table(bits_dc_chrominance, val_dc_chrominance, &priv->HTDC[1]);
  build_huffman_table(bits_ac_chrominance, val_ac_chrominance, &priv->HTAC[1]);

  priv->default_huffman_table_initialized = 1;
}



/*******************************************************************************
 *
 * Colorspace conversion routine
 *
 *
 * Note:
 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
 * The conversion equations to be implemented are therefore
 *      R = Y                + 1.40200 * Cr
 *      G = Y - 0.34414 * Cb - 0.71414 * Cr
 *      B = Y + 1.77200 * Cb
 *
 ******************************************************************************/

static void print_SOF(const unsigned char *stream)
{
#if JPEG_DEBUG
  int width, height, nr_components, precision;
  const char *nr_components_to_string[] = {
     "????",
     "Grayscale",
     "????",
     "YCbCr",
     "CYMK"
  };

  precision = stream[2];
  height = be16_to_cpu(stream+3);
  width  = be16_to_cpu(stream+5);
  nr_components = stream[7];

  trace("> SOF marker\n");
  trace("Size:%dx%d nr_components:%d (%s)  precision:%d\n",
      width, height,
      nr_components, nr_components_to_string[nr_components],
      precision);
#endif
  (void)stream;
}

/*******************************************************************************
 *
 * JPEG/JFIF Parsing functions
 *
 * Note: only a small subset of the jpeg file format is supported. No markers,
 * nor progressive stream is supported.
 *
 ******************************************************************************/

static void build_quantization_table(float *qtable, const unsigned char *ref_table)
{
  /* Taken from libjpeg. Copyright Independent JPEG Group's LLM idct.
   * For float AA&N IDCT method, divisors are equal to quantization
   * coefficients scaled by scalefactor[row]*scalefactor[col], where
   *   scalefactor[0] = 1
   *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
   * We apply a further scale factor of 8.
   * What's actually stored is 1/divisor so that the inner loop can
   * use a multiplication rather than a division.
   */
  int i, j;
  static const double aanscalefactor[8] = {
     1.0, 1.387039845, 1.306562965, 1.175875602,
     1.0, 0.785694958, 0.541196100, 0.275899379
  };
  const unsigned char *zz = zigzag;

  for (i=0; i<8; i++) {
     for (j=0; j<8; j++) {
       *qtable++ = ref_table[*zz++] * aanscalefactor[i] * aanscalefactor[j];
     }
   }

}

static int parse_DQT(struct jdec_private *priv, const unsigned char *stream)
{
  int qi;
  float *table;
  const unsigned char *dqt_block_end;

  trace("> DQT marker\n");
  dqt_block_end = stream + be16_to_cpu(stream);
  stream += 2;  /* Skip length */

  while (stream < dqt_block_end)
   {
     qi = *stream++;
#if SANITY_CHECK
     if (qi>>4)
       error("16 bits quantization table is not supported\n");
     if (qi>4)
       error("No more 4 quantization table is supported (got %d)\n", qi);
#endif
     table = priv->Q_tables[qi];
     build_quantization_table(table, stream);
     stream += 64;
   }
  trace("< DQT marker\n");
  return 0;
}

static int parse_SOF(struct jdec_private *priv, const unsigned char *stream)
{
  int i, width, height, nr_components, cid, sampling_factor;
  int Q_table;
  struct component *c;

  trace("> SOF marker\n");
  print_SOF(stream);

  height = be16_to_cpu(stream+3);
  width  = be16_to_cpu(stream+5);
  nr_components = stream[7];
#if SANITY_CHECK
  if (stream[2] != 8)
    error("Precision other than 8 is not supported\n");
  if (width>JPEG_MAX_WIDTH || height>JPEG_MAX_HEIGHT)
    error("Width and Height (%dx%d) seems suspicious\n", width, height);
  if (nr_components != 3)
    error("We only support YUV images\n");
#endif
  stream += 8;
  for (i=0; i<nr_components; i++) {
     cid = *stream++;
     sampling_factor = *stream++;
     Q_table = *stream++;
     c = &priv->component_infos[i];
#if SANITY_CHECK
     c->cid = cid;
     if (Q_table >= COMPONENTS)
       error("Bad Quantization table index (got %d, max allowed %d)\n", Q_table, COMPONENTS-1);
#endif
     c->Vfactor = sampling_factor&0xf;
     c->Hfactor = sampling_factor>>4;
     c->Q_table = priv->Q_tables[Q_table];
     trace("Component:%d  factor:%dx%d  Quantization table:%d\n",
           cid, c->Hfactor, c->Hfactor, Q_table );

  }
  priv->width = width;
  priv->height = height;

  trace("< SOF marker\n");

  return 0;
}

static int parse_SOS(struct jdec_private *priv, const unsigned char *stream)
{
  unsigned int i, cid, table;
  unsigned int nr_components = stream[2];

  trace("> SOS marker\n");

#if SANITY_CHECK
  if (nr_components != 3)
    error("We only support YCbCr image\n");
#endif

  stream += 3;
  for (i=0;i<nr_components;i++) {
     cid = *stream++;
     table = *stream++;
#if SANITY_CHECK
     if ((table&0xf)>=4)
        error("We do not support more than 2 AC Huffman table\n");
     if ((table>>4)>=4)
        error("We do not support more than 2 DC Huffman table\n");
     if (cid != priv->component_infos[i].cid)
        error("SOS cid order (%d:%d) isn't compatible with the SOF marker (%d:%d)\n",
              i, cid, i, priv->component_infos[i].cid);
     trace("ComponentId:%d  tableAC:%d tableDC:%d\n", cid, table&0xf, table>>4);
#endif
     priv->component_infos[i].AC_table = &priv->HTAC[table&0xf];
     priv->component_infos[i].DC_table = &priv->HTDC[table>>4];
  }
  priv->stream = stream+3;
  trace("< SOS marker\n");
  return 0;
}

static int parse_DHT(struct jdec_private *priv, const unsigned char *stream)
{
  unsigned int count, i;
  unsigned char huff_bits[17];
  int length, index;

  length = be16_to_cpu(stream) - 2;
  stream += 2;  /* Skip length */

  trace("> DHT marker (length=%d)\n", length);

  while (length>0) {
     index = *stream++;

     /* We need to calculate the number of bytes 'vals' will takes */
     huff_bits[0] = 0;
     count = 0;
     for (i=1; i<17; i++) {
        huff_bits[i] = *stream++;
        count += huff_bits[i];
     }
#if SANITY_CHECK
     if (count >= HUFFMAN_BITS_SIZE)
       error("No more than %d bytes is allowed to describe a huffman table", HUFFMAN_BITS_SIZE);
     if ( (index &0xf) >= HUFFMAN_TABLES)
       error("No more than %d Huffman tables is supported (got %d)\n", HUFFMAN_TABLES, index&0xf);
     trace("Huffman table %s[%d] length=%d\n", (index&0xf0)?"AC":"DC", index&0xf, count);
#endif

     if (index & 0xf0 )
       build_huffman_table(huff_bits, stream, &priv->HTAC[index&0xf]);
     else
       build_huffman_table(huff_bits, stream, &priv->HTDC[index&0xf]);

     length -= 1;
     length -= 16;
     length -= count;
     stream += count;
  }
  trace("< DHT marker\n");
  return 0;
}

static int parse_DRI(struct jdec_private *priv, const unsigned char *stream)
{
  unsigned int length;

  trace("> DRI marker\n");

  length = be16_to_cpu(stream);

#if SANITY_CHECK
  if (length != 4)
    error("Length of DRI marker need to be 4\n");
#endif

  priv->restart_interval = be16_to_cpu(stream+2);

#if JPEG_DEBUG
  trace("Restart interval = %d\n", priv->restart_interval);
#endif

  trace("< DRI marker\n");

  return 0;
}



static void resync(struct jdec_private *priv)
{
  int i;

  /* Init DC coefficients */
  for (i=0; i<COMPONENTS; i++)
     priv->component_infos[i].previous_DC = 0;

  priv->reservoir = 0;
  priv->nbits_in_reservoir = 0;
  if (priv->restart_interval > 0)
    priv->restarts_to_go = priv->restart_interval;
  else
    priv->restarts_to_go = -1;
}

static int find_next_rst_marker(struct jdec_private *priv)
{
  int rst_marker_found = 0;
  int marker;
  const unsigned char *stream = priv->stream;

  /* Parse marker */
  while (!rst_marker_found)
   {
     while (*stream++ != 0xff)
      {
        if (stream >= priv->stream_end)
          error("EOF while search for a RST marker.");
      }
     /* Skip any padding ff byte (this is normal) */
     while (*stream == 0xff)
       stream++;

     marker = *stream++;
     if ((RST+priv->last_rst_marker_seen) == marker)
       rst_marker_found = 1;
     else if (marker >= RST && marker <= RST7)
       error("Wrong Reset marker found, abording");
     else if (marker == EOI)
       return 0;
   }
  trace("RST Marker %d found at offset %d\n", priv->last_rst_marker_seen, stream - priv->stream_begin);

  priv->stream = stream;
  priv->last_rst_marker_seen++;
  priv->last_rst_marker_seen &= 7;

  return 0;
}

static int parse_JFIF(struct jdec_private *priv, const unsigned char *stream)
{
  int chuck_len;
  int marker;
  int sos_marker_found = 0;
  int dht_marker_found = 0;
  const unsigned char *next_chunck;

  /* Parse marker */
  while (!sos_marker_found)
   {
     if (*stream++ != 0xff)
       goto bogus_jpeg_format;
     /* Skip any padding ff byte (this is normal) */
     while (*stream == 0xff)
       stream++;

     marker = *stream++;
     chuck_len = be16_to_cpu(stream);
     next_chunck = stream + chuck_len;
     switch (marker)
      {
       case SOF:
         if (parse_SOF(priv, stream) < 0)
           return -1;
         break;
       case DQT:
         if (parse_DQT(priv, stream) < 0)
           return -1;
         break;
       case SOS:
         if (parse_SOS(priv, stream) < 0)
           return -1;
         sos_marker_found = 1;
         break;
       case DHT:
         if (parse_DHT(priv, stream) < 0)
           return -1;
         dht_marker_found = 1;
         break;
       case DRI:
         if (parse_DRI(priv, stream) < 0)
           return -1;
         break;
       default:
         trace("> Unknown marker %2.2x\n", marker);
         break;
      }

     stream = next_chunck;
   }

  if (!dht_marker_found) {
    trace("No Huffman table loaded, using the default one\n");
    build_default_huffman_tables(priv);
  }

#ifdef SANITY_CHECK
  if (   (priv->component_infos[cY].Hfactor < priv->component_infos[cCb].Hfactor)
      || (priv->component_infos[cY].Hfactor < priv->component_infos[cCr].Hfactor))
    error("Horizontal sampling factor for Y should be greater than horitontal sampling factor for Cb or Cr\n");
  if (   (priv->component_infos[cY].Vfactor < priv->component_infos[cCb].Vfactor)
      || (priv->component_infos[cY].Vfactor < priv->component_infos[cCr].Vfactor))
    error("Vertical sampling factor for Y should be greater than vertical sampling factor for Cb or Cr\n");
  if (   (priv->component_infos[cCb].Hfactor!=1)
      || (priv->component_infos[cCr].Hfactor!=1)
      || (priv->component_infos[cCb].Vfactor!=1)
      || (priv->component_infos[cCr].Vfactor!=1))
    error("Sampling other than 1x1 for Cr and Cb is not supported");
#endif

  return 0;
bogus_jpeg_format:
  trace("Bogus jpeg format\n");
  return -1;
}

/*******************************************************************************
 *
 * Functions exported of the library.
 *
 * Note: Some applications can access directly to internal pointer of the
 * structure. It's is not recommended, but if you have many images to
 * uncompress with the same parameters, some functions can be called to speedup
 * the decoding.
 *
 ******************************************************************************/

/**
 * Allocate a new tinyjpeg decoder object.
 *
 * Before calling any other functions, an object need to be called.
 */
struct jdec_private *tinyjpeg_init(void)
{
  struct jdec_private *priv;

  priv = (struct jdec_private *)calloc(1, sizeof(struct jdec_private));
  if (priv == NULL)
    return NULL;
  return priv;
}

/**
 * Free a tinyjpeg object.
 *
 * No others function can be called after this one.
 */
void tinyjpeg_free(struct jdec_private *priv)
{
  int i;
  for (i=0; i<COMPONENTS; i++) {
     if (priv->components[i])
       free(priv->components[i]);
     priv->components[i] = NULL;
  }
  free(priv);
}

/**
 * Initialize the tinyjpeg object and prepare the decoding of the stream.
 *
 * Check if the jpeg can be decoded with this jpeg decoder.
 * Fill some table used for preprocessing.
 */
int tinyjpeg_parse_header(struct jdec_private *priv, const unsigned char *buf, unsigned int size)
{
  int ret;

  /* Identify the file */
  if ((buf[0] != 0xFF) || (buf[1] != SOI))
    error("Not a JPG file ?\n");

  priv->stream_begin = buf+2;
  priv->stream_length = size-2;
  priv->stream_end = priv->stream_begin + priv->stream_length;

  ret = parse_JFIF(priv, priv->stream_begin);

  return ret;
}

/**
 * Decode and convert the jpeg image into @pixfmt@ image
 *
 * Note: components will be automaticaly allocated if no memory is attached.
 */
int tinyjpeg_decode(struct jdec_private *priv,
                    const struct tinyjpeg_colorspace *pixfmt)
{
  int x, y, sx, sy;
  int xshift_by_mcu, yshift_by_mcu;
  int xstride_by_mcu, ystride_by_mcu;
  unsigned int bytes_per_blocklines[3], bytes_per_mcu[3];
  decode_MCU_fct decode_MCU;
  const decode_MCU_fct *decode_mcu_table;
  convert_colorspace_fct convert_to_pixfmt;
  uint8_t *pptr[3];

  decode_mcu_table = pixfmt->decode_mcu_table;

  /* Fix: check return value */
  pixfmt->initialize(priv, bytes_per_blocklines, bytes_per_mcu);

  xshift_by_mcu = yshift_by_mcu = 3;
  if ((priv->component_infos[cY].Hfactor | priv->component_infos[cY].Vfactor) == 1) {
     decode_MCU = decode_mcu_table[0];
     convert_to_pixfmt = pixfmt->convert_colorspace[0];
     trace("Use decode 1x1 sampling\n");
  } else if (priv->component_infos[cY].Hfactor == 1) {
     decode_MCU = decode_mcu_table[1];
     convert_to_pixfmt = pixfmt->convert_colorspace[1];
     yshift_by_mcu = 4;
     trace("Use decode 1x2 sampling (not supported)\n");
  } else if (priv->component_infos[cY].Vfactor == 2) {
     decode_MCU = decode_mcu_table[3];
     convert_to_pixfmt = pixfmt->convert_colorspace[3];
     xshift_by_mcu = 4;
     yshift_by_mcu = 4;
     trace("Use decode 2x2 sampling\n");
  } else {
     decode_MCU = decode_mcu_table[2];
     convert_to_pixfmt = pixfmt->convert_colorspace[2];
     xshift_by_mcu = 4;
     trace("Use decode 2x1 sampling\n");
  }

  resync(priv);

  /* Don't forget to that block can be either 8 or 16 lines */
  bytes_per_blocklines[0] <<= yshift_by_mcu-3;
  bytes_per_blocklines[1] <<= yshift_by_mcu-3;
  bytes_per_blocklines[2] <<= yshift_by_mcu-3;

  bytes_per_mcu[0] <<= xshift_by_mcu-3;
  bytes_per_mcu[1] <<= xshift_by_mcu-3;
  bytes_per_mcu[2] <<= xshift_by_mcu-3;

  xstride_by_mcu = 1 << xshift_by_mcu;
  ystride_by_mcu = 1 << yshift_by_mcu;

  pptr[0] = priv->components[0];
  pptr[1] = priv->components[1];
  pptr[2] = priv->components[2];

  trace("bpbl = %d, bpmcu = %d\n",
        bytes_per_blocklines[0], bytes_per_mcu[0]);

  for (y = priv->height; y > 0; y -= ystride_by_mcu)
   {
     trace("Decoding row %d\n", priv->height-y);
     priv->plane[0] = pptr[0];  pptr[0] += bytes_per_blocklines[0];
     priv->plane[1] = pptr[1];  pptr[1] += bytes_per_blocklines[1];
     priv->plane[2] = pptr[2];  pptr[2] += bytes_per_blocklines[2];

     sy = min(y, ystride_by_mcu);

     for (x = priv->width; x > 0; x -= xstride_by_mcu)
      {
        sx = min(x, xstride_by_mcu);
        trace("Block size: %dx%d\n", sx, sy);

        decode_MCU(priv);
        convert_to_pixfmt(priv, sx, sy);
        priv->plane[0] += bytes_per_mcu[0];
        priv->plane[1] += bytes_per_mcu[1];
        priv->plane[2] += bytes_per_mcu[2];
        if (priv->restarts_to_go>0)
         {
           priv->restarts_to_go--;
           if (priv->restarts_to_go == 0)
            {
              priv->stream -= (priv->nbits_in_reservoir/8);
              resync(priv);
              if (find_next_rst_marker(priv) < 0)
                return -1;
            }
         }
      }
   }

  trace("Input file size: %d\n", priv->stream_length+2);
  trace("Input bytes actually read: %d\n", priv->stream - priv->stream_begin + 2);

  return 0;
}

const char *tinyjpeg_get_errorstring(struct jdec_private *priv)
{
  /* FIXME: the error string must be store in the context */
  priv = priv;
  return error_string;
}

void tinyjpeg_get_size(struct jdec_private *priv, unsigned int *width, unsigned int *height)
{
  *width = priv->width;
  *height = priv->height;
}

int tinyjpeg_get_components(struct jdec_private *priv, unsigned char **components, unsigned int ncomponents)
{
  unsigned int i;
  if (ncomponents > COMPONENTS)
    ncomponents = COMPONENTS;
  for (i=0; i<ncomponents; i++)
    components[i] = priv->components[i];
  return 0;
}

int tinyjpeg_set_components(struct jdec_private *priv, unsigned char * const *components, unsigned int ncomponents)
{
  unsigned int i;
  if (ncomponents > COMPONENTS)
    ncomponents = COMPONENTS;
  for (i=0; i<ncomponents; i++)
    priv->components[i] = components[i];
  return 0;
}

int tinyjpeg_get_bytes_per_row(struct jdec_private *priv,
                               unsigned int *bytes,
                               unsigned int ncomponents)
{
  unsigned int i;
  if (ncomponents > COMPONENTS)
    ncomponents = COMPONENTS;
  for (i=0; i<ncomponents; i++)
    bytes[i] = priv->bytes_per_row[i];
  return 0;
}

int tinyjpeg_set_bytes_per_row(struct jdec_private *priv,
                               const unsigned int *bytes,
                               unsigned int ncomponents)
{
  unsigned int i;
  if (ncomponents > COMPONENTS)
    ncomponents = COMPONENTS;
  for (i=0; i<ncomponents; i++)
    priv->bytes_per_row[i] = bytes[i];
  return 0;
}

int tinyjpeg_set_flags(struct jdec_private *priv, int flags)
{
  int oldflags = priv->flags;
  priv->flags = flags;
  return oldflags;
}