Function stbi__parse_entropy_coded_data

stb/stb_image.h:2949–3071

}

static int stbi__parse_entropy_coded_data(stbi__jpeg *z)
{
   stbi__jpeg_reset(z);
   if (!z->progressive) {
      if (z->scan_n == 1) {
         int i,j;
         STBI_SIMD_ALIGN(short, data[64]);
         int n = z->order[0];
         // non-interleaved data, we just need to process one block at a time,
         // in trivial scanline order
         // number of blocks to do just depends on how many actual "pixels" this
         // component has, independent of interleaved MCU blocking and such
         int w = (z->img_comp[n].x+7) >> 3;
         int h = (z->img_comp[n].y+7) >> 3;
         for (j=0; j < h; ++j) {
            for (i=0; i < w; ++i) {
               int ha = z->img_comp[n].ha;
               if (!stbi__jpeg_decode_block(z, data, z->huff_dc+z->img_comp[n].hd, z->huff_ac+ha, z->fast_ac[ha], n, z->dequant[z->img_comp[n].tq])) return 0;
               z->idct_block_kernel(z->img_comp[n].data+z->img_comp[n].w2*j*8+i*8, z->img_comp[n].w2, data);
               // every data block is an MCU, so countdown the restart interval
               if (--z->todo <= 0) {
                  if (z->code_bits < 24) stbi__grow_buffer_unsafe(z);
                  // if it's NOT a restart, then just bail, so we get corrupt data
                  // rather than no data
                  if (!STBI__RESTART(z->marker)) return 1;
                  stbi__jpeg_reset(z);
               }
            }
         }
         return 1;
      } else { // interleaved
         int i,j,k,x,y;
         STBI_SIMD_ALIGN(short, data[64]);
         for (j=0; j < z->img_mcu_y; ++j) {
            for (i=0; i < z->img_mcu_x; ++i) {
               // scan an interleaved mcu... process scan_n components in order
               for (k=0; k < z->scan_n; ++k) {
                  int n = z->order[k];
                  // scan out an mcu's worth of this component; that's just determined
                  // by the basic H and V specified for the component
                  for (y=0; y < z->img_comp[n].v; ++y) {
                     for (x=0; x < z->img_comp[n].h; ++x) {
                        int x2 = (i*z->img_comp[n].h + x)*8;
                        int y2 = (j*z->img_comp[n].v + y)*8;
                        int ha = z->img_comp[n].ha;
                        if (!stbi__jpeg_decode_block(z, data, z->huff_dc+z->img_comp[n].hd, z->huff_ac+ha, z->fast_ac[ha], n, z->dequant[z->img_comp[n].tq])) return 0;
                        z->idct_block_kernel(z->img_comp[n].data+z->img_comp[n].w2*y2+x2, z->img_comp[n].w2, data);
                     }
                  }
               }
               // after all interleaved components, that's an interleaved MCU,
               // so now count down the restart interval
               if (--z->todo <= 0) {
                  if (z->code_bits < 24) stbi__grow_buffer_unsafe(z);
                  if (!STBI__RESTART(z->marker)) return 1;
                  stbi__jpeg_reset(z);
               }
            }