Function decodeGeneric

dependency/densecrf/examples/lodepng.cpp:4516–4671

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;
    size_t predict;
    size_t numpixels;
    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*/
    
    /*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;
    
    numpixels = *w * *h;
    
    /*multiplication overflow*/
    if(*h != 0 && numpixels / *h != *w) CERROR_RETURN(state->error, 92);
    /*multiplication overflow possible further below. Allows up to 2^31-1 pixel
     bytes with 16-bit RGBA, the rest is room for filter bytes.*/
    if(numpixels > 268435455) CERROR_RETURN(state->error, 92);
    
    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);