Function decodeGeneric

depends/lodepng/lodepng.cpp:4757–4949

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;
  unsigned char* idat; /*the data from idat chunks, zlib compressed*/
  size_t idatsize = 0;
  unsigned char* scanlines = 0;
  size_t scanlines_size = 0, expected_size = 0;
  size_t outsize = 0;

  /*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*/


  /* safe output values in case error happens */
  *out = 0;
  *w = *h = 0;

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

  if(lodepng_pixel_overflow(*w, *h, &state->info_png.color, &state->info_raw)) {
    CERROR_RETURN(state->error, 92); /*overflow possible due to amount of pixels*/
  }

  /*the input filesize is a safe upper bound for the sum of idat chunks size*/
  idat = (unsigned char*)lodepng_malloc(insize);
  if(!idat) CERROR_RETURN(state->error, 83); /*alloc fail*/

  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) {
      if(state->decoder.ignore_end) break; /*other errors may still happen though*/
      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) {
      if(state->decoder.ignore_end) break; /*other errors may still happen though*/
      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*/
    }