Method _decode_header

src/proxy/http3/QPACK.cc:912–975

}

int
QPACK::_decode_header(const uint8_t *header_block, size_t header_block_len, HTTPHdr &hdr)
{
  const uint8_t *pos        = header_block;
  size_t         remain_len = header_block_len;
  int64_t        ret;

  // Decode Header Data Prefix
  uint64_t tmp;
  if ((ret = xpack_decode_integer(tmp, pos, pos + remain_len, 8)) < 0 && tmp > 0xFFFF) {
    return -1;
  }
  pos                        += ret;
  uint16_t largest_reference  = tmp;

  uint64_t delta_base_index;
  uint16_t base_index;
  if ((ret = xpack_decode_integer(delta_base_index, pos, pos + remain_len, 7)) < 0 && delta_base_index < 0xFFFF) {
    return -2;
  }

  if (pos[0] & 0x80) {
    if (delta_base_index == 0) {
      return -3;
    }
    base_index = largest_reference - delta_base_index;
  } else {
    base_index = largest_reference + delta_base_index;
  }
  pos += ret;

  uint32_t decoded_header_list_size = 0;

  // Decode Instructions
  while (pos < header_block + header_block_len) {
    uint32_t header_len = 0;

    if (pos[0] & 0x80) { // Index Header Field
      ret = this->_decode_indexed_header_field(base_index, pos, remain_len, hdr, header_len);
    } else if (pos[0] & 0x40) { // Literal Header Field With Name Reference
      ret = this->_decode_literal_header_field_with_name_ref(base_index, pos, remain_len, hdr, header_len);
    } else if (pos[0] & 0x20) { // Literal Header Field Without Name Reference
      ret = this->_decode_literal_header_field_without_name_ref(pos, remain_len, hdr, header_len);
    } else if (pos[0] & 0x10) { // Indexed Header Field With Post-Base Index
      ret = this->_decode_indexed_header_field_with_postbase_index(base_index, pos, remain_len, hdr, header_len);
    } else { // Literal Header Field With Post-Base Name Reference
      ret = this->_decode_literal_header_field_with_postbase_name_ref(base_index, pos, remain_len, hdr, header_len);
    }

    if (ret < 0) {
      break;
    }

    decoded_header_list_size += header_len;
    if (decoded_header_list_size > this->_max_field_section_size) {
      ret = -2;
      break;
    }