Function xpack_decode_integer

src/proxy/hdrs/XPACK.cc:63–92

[RFC 7541] 5.1. Integer representation

// [RFC 7541] 5.1. Integer representation
//
int64_t
xpack_decode_integer(uint64_t &dst, const uint8_t *buf_start, const uint8_t *buf_end, uint8_t n)
{
  if (buf_start >= buf_end) {
    return XPACK_ERROR_COMPRESSION_ERROR;
  }

  const uint8_t *p = buf_start;

  dst = (*p & ((1 << n) - 1));
  if (dst == static_cast<uint64_t>(1 << n) - 1) {
    int m = 0;
    do {
      if (++p >= buf_end) {
        return XPACK_ERROR_COMPRESSION_ERROR;
      }

      uint64_t added_value = *p & 0x7f;
      if ((UINT64_MAX >> m) < added_value) {
        // Excessively large integer encodings - in value or octet
        // length - MUST be treated as a decoding error.
        return XPACK_ERROR_COMPRESSION_ERROR;
      }
      dst += added_value << m;
      m   += 7;
    } while (*p & 0x80);
  }

  return p - buf_start + 1;
}

//
// [RFC 7541] 5.2. String Literal Representation