Function deflateNoCompression

external/lodepng/lodepng.cpp:1740–1771

/* /////////////////////////////////////////////////////////////////////////// */

static unsigned deflateNoCompression(ucvector* out, const unsigned char* data, size_t datasize) {
  /*non compressed deflate block data: 1 bit BFINAL,2 bits BTYPE,(5 bits): it jumps to start of next byte,
  2 bytes LEN, 2 bytes NLEN, LEN bytes literal DATA*/

  size_t i, numdeflateblocks = (datasize + 65534u) / 65535u;
  size_t datapos = 0;
  for(i = 0; i != numdeflateblocks; ++i) {
    unsigned BFINAL, BTYPE, LEN, NLEN;
    unsigned char firstbyte;
    size_t pos = out->size;

    BFINAL = (i == numdeflateblocks - 1);
    BTYPE = 0;

    LEN = 65535;
    if(datasize - datapos < 65535u) LEN = (unsigned)datasize - (unsigned)datapos;
    NLEN = 65535 - LEN;

    if(!ucvector_resize(out, out->size + LEN + 5)) return 83; /*alloc fail*/

    firstbyte = (unsigned char)(BFINAL + ((BTYPE & 1u) << 1u) + ((BTYPE & 2u) << 1u));
    out->data[pos + 0] = firstbyte;
    out->data[pos + 1] = (unsigned char)(LEN & 255);
    out->data[pos + 2] = (unsigned char)(LEN >> 8u);
    out->data[pos + 3] = (unsigned char)(NLEN & 255);
    out->data[pos + 4] = (unsigned char)(NLEN >> 8u);
    lodepng_memcpy(out->data + pos + 5, data + datapos, LEN);
    datapos += LEN;
  }

  return 0;
}

/*
write the lz77-encoded data, which has lit, len and dist codes, to compressed stream using huffman trees.