Function getTreeInflateDynamic

depends/lodepng/lodepng.cpp:1130–1260

get the tree of a deflated block with dynamic tree, the tree itself is also Huffman compressed with a known tree*/

/*get the tree of a deflated block with dynamic tree, the tree itself is also Huffman compressed with a known tree*/
static unsigned getTreeInflateDynamic(HuffmanTree* tree_ll, HuffmanTree* tree_d,
                                      LodePNGBitReader* reader) {
  /*make sure that length values that aren't filled in will be 0, or a wrong tree will be generated*/
  unsigned error = 0;
  unsigned n, HLIT, HDIST, HCLEN, i;

  /*see comments in deflateDynamic for explanation of the context and these variables, it is analogous*/
  unsigned* bitlen_ll = 0; /*lit,len code lengths*/
  unsigned* bitlen_d = 0; /*dist code lengths*/
  /*code length code lengths ("clcl"), the bit lengths of the huffman tree used to compress bitlen_ll and bitlen_d*/
  unsigned* bitlen_cl = 0;
  HuffmanTree tree_cl; /*the code tree for code length codes (the huffman tree for compressed huffman trees)*/

  if(!ensureBits17(reader, 14)) return 49; /*error: the bit pointer is or will go past the memory*/

  /*number of literal/length codes + 257. Unlike the spec, the value 257 is added to it here already*/
  HLIT =  readBits(reader, 5) + 257;
  /*number of distance codes. Unlike the spec, the value 1 is added to it here already*/
  HDIST = readBits(reader, 5) + 1;
  /*number of code length codes. Unlike the spec, the value 4 is added to it here already*/
  HCLEN = readBits(reader, 4) + 4;

  bitlen_cl = (unsigned*)lodepng_malloc(NUM_CODE_LENGTH_CODES * sizeof(unsigned));
  if(!bitlen_cl) return 83 /*alloc fail*/;

  HuffmanTree_init(&tree_cl);

  while(!error) {
    /*read the code length codes out of 3 * (amount of code length codes) bits*/
    if(lodepng_gtofl(reader->bp, HCLEN * 3, reader->bitsize)) {
      ERROR_BREAK(50); /*error: the bit pointer is or will go past the memory*/
    }
    for(i = 0; i != HCLEN; ++i) {
      ensureBits9(reader, 3); /*out of bounds already checked above */
      bitlen_cl[CLCL_ORDER[i]] = readBits(reader, 3);
    }
    for(i = HCLEN; i != NUM_CODE_LENGTH_CODES; ++i) {
      bitlen_cl[CLCL_ORDER[i]] = 0;
    }

    error = HuffmanTree_makeFromLengths(&tree_cl, bitlen_cl, NUM_CODE_LENGTH_CODES, 7);
    if(error) break;

    /*now we can use this tree to read the lengths for the tree that this function will return*/
    bitlen_ll = (unsigned*)lodepng_malloc(NUM_DEFLATE_CODE_SYMBOLS * sizeof(unsigned));
    bitlen_d = (unsigned*)lodepng_malloc(NUM_DISTANCE_SYMBOLS * sizeof(unsigned));
    if(!bitlen_ll || !bitlen_d) ERROR_BREAK(83 /*alloc fail*/);
    lodepng_memset(bitlen_ll, 0, NUM_DEFLATE_CODE_SYMBOLS * sizeof(*bitlen_ll));
    lodepng_memset(bitlen_d, 0, NUM_DISTANCE_SYMBOLS * sizeof(*bitlen_d));

    /*i is the current symbol we're reading in the part that contains the code lengths of lit/len and dist codes*/
    i = 0;
    while(i < HLIT + HDIST) {
      unsigned code;
      ensureBits25(reader, 22); /* up to 15 bits for huffman code, up to 7 extra bits below*/
      code = huffmanDecodeSymbol(reader, &tree_cl);
      if(code <= 15) /*a length code*/ {
        if(i < HLIT) bitlen_ll[i] = code;