Function huffman_encode

src/proxy/hdrs/HuffmanCodec.cc:443–480

}

int64_t
huffman_encode(uint8_t *dst_start, const uint8_t *src, uint32_t src_len)
{
  uint8_t *dst = dst_start;
  // NOTE: The maximum length of Huffman Code is 30, thus using uint32_t as buffer.
  uint32_t buf         = 0;
  uint32_t remain_bits = 32;

  for (uint32_t i = 0; i < src_len; ++i) {
    const uint32_t hex     = huffman_table[src[i]].code_as_hex;
    const uint32_t bit_len = huffman_table[src[i]].bit_len;

    if (remain_bits > bit_len) {
      remain_bits  = remain_bits - bit_len;
      buf         |= hex << remain_bits;
    } else if (remain_bits == bit_len) {
      buf         |= hex;
      dst          = huffman_encode_append(dst, buf);
      remain_bits  = 32;
      buf          = 0;
    } else {
      buf         |= hex >> (bit_len - remain_bits);
      dst          = huffman_encode_append(dst, buf);
      remain_bits  = (32 - (bit_len - remain_bits));
      buf          = hex << remain_bits;
    }
  }

  dst = huffman_encode_append(dst, buf, remain_bits / 8);

  // NOTE: Add padding w/ EOS
  uint32_t pad_len = remain_bits % 8;
  if (pad_len) {
    *(dst - 1) |= 0xff >> (8 - pad_len);
  }

  return dst - dst_start;
}