Function decodeGeneric

src/lodepng.cpp:4562–4706

read a PNG, the result will be in the same color type as the PNG (hence "generic")*/

/*read a PNG, the result will be in the same color type as the PNG (hence "generic")*/
static void decodeGeneric(unsigned char** out, unsigned* w, unsigned* h,
                          LodePNGState* state,
                          const unsigned char* in, size_t insize)
{
  unsigned char IEND = 0;
  const unsigned char* chunk;
  size_t i;
  ucvector idat; /*the data from idat chunks*/
  ucvector scanlines;

  /*for unknown chunk order*/
  unsigned unknown = 0;
#ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
  unsigned critical_pos = 1; /*1 = after IHDR, 2 = after PLTE, 3 = after IDAT*/
#endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/

  /*provide some proper output values if error will happen*/
  *out = 0;

  state->error = lodepng_inspect(w, h, state, in, insize); /*reads header and resets other parameters in state->info_png*/
  if(state->error) return;

  ucvector_init(&idat);
  chunk = &in[33]; /*first byte of the first chunk after the header*/

  /*loop through the chunks, ignoring unknown chunks and stopping at IEND chunk.
  IDAT data is put at the start of the in buffer*/
  while(!IEND && !state->error)
  {
    unsigned chunkLength;
    const unsigned char* data; /*the data in the chunk*/

    /*error: size of the in buffer too small to contain next chunk*/
    if((size_t)((chunk - in) + 12) > insize || chunk < in) CERROR_BREAK(state->error, 30);

    /*length of the data of the chunk, excluding the length bytes, chunk type and CRC bytes*/
    chunkLength = lodepng_chunk_length(chunk);
    /*error: chunk length larger than the max PNG chunk size*/
    if(chunkLength > 2147483647) CERROR_BREAK(state->error, 63);

    if((size_t)((chunk - in) + chunkLength + 12) > insize || (chunk + chunkLength + 12) < in)
    {
      CERROR_BREAK(state->error, 64); /*error: size of the in buffer too small to contain next chunk*/
    }

    data = lodepng_chunk_data_const(chunk);

    /*IDAT chunk, containing compressed image data*/
    if(lodepng_chunk_type_equals(chunk, "IDAT"))
    {
      size_t oldsize = idat.size;
      if(!ucvector_resize(&idat, oldsize + chunkLength)) CERROR_BREAK(state->error, 83 /*alloc fail*/);
      for(i = 0; i < chunkLength; i++) idat.data[oldsize + i] = data[i];
#ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
      critical_pos = 3;
#endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
    }
    /*IEND chunk*/