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/*-------------------------------------------*/
/* File : huffman.c, utilities for jfif view */
/* Author : Pierre Guerrier, march 1998	     */
/*-------------------------------------------*/
 
#include <stdlib.h>
#include <stdio.h>
 
 
/*--------------------------------------*/
/* private huffman.c defines and macros */
/*--------------------------------------*/
 
#define HUFF_EOB		0x00
#define HUFF_ZRL		0xF0
 
/*------------------------------------------*/
/* some constants for on-the-fly IQ and IZZ */
/*------------------------------------------*/
 
static const int G_ZZ[] = {
   0,  1,  8, 16,  9,  2,  3, 10,
  17, 24, 32, 25, 18, 11,  4,  5,
  12, 19, 26, 33, 40, 48, 41, 34,
  27, 20, 13,  6,  7, 14, 21, 28,
  35, 42, 49, 56, 57, 50, 43, 36,
  29, 22, 15, 23, 30, 37, 44, 51,
  58, 59, 52, 45, 38, 31, 39, 46,
  53, 60, 61, 54, 47, 55, 62, 63
};
 
/*-------------------------------------------------*/
/* here we unpack, predict, unquantify and reorder */
/* a complete 8*8 DCT block ...			   */
/*-------------------------------------------------*/
 
void
unpack_block(FILE *fi, FBlock *T, int select)
{
  unsigned int i, run, cat;
  int value;
  unsigned char	symbol;
 
  /* Init the block with 0's: */
  for (i=0; i<64; i++) T->linear[i] = 0;
 
  /* First get the DC coefficient: */
  symbol = get_symbol(fi, HUFF_ID(DC_CLASS, comp[select].DC_HT));
  value = reformat(get_bits(fi, symbol), symbol);
 
#ifdef SPY
  trace_bits(symbol, 1);
#endif
 
  value += comp[select].PRED;
  comp[select].PRED = value;
  T->linear[0] = value * QTable[comp[select].QT]->linear[0];
 
  /* Now get all 63 AC values: */
  for (i=1; i<64; i++) {
    symbol = get_symbol(fi, HUFF_ID(AC_CLASS, comp[select].AC_HT));
    if (symbol == HUFF_EOB) break;
    if (symbol == HUFF_ZRL) { i += 15; continue; }
    cat = symbol & 0x0F;
    run = (symbol>>4) & 0x0F;
    i += run;
    value = reformat(get_bits(fi, cat), cat);
 
#ifdef SPY
    trace_bits(cat, 1);
#endif
 
    /* Dequantify and ZigZag-reorder: */
    T->linear[G_ZZ[i]] = value * QTable[comp[select].QT]->linear[i];
  }
}