Function xpack_encode_integer

src/proxy/hdrs/XPACK.cc:143–177

[RFC 7541] 5.1. Integer representation

// [RFC 7541] 5.1. Integer representation
//
int64_t
xpack_encode_integer(uint8_t *buf_start, const uint8_t *buf_end, uint64_t value, uint8_t n)
{
  if (buf_start >= buf_end) {
    return -1;
  }

  uint8_t *p = buf_start;

  // Preserve the first n bits
  uint8_t prefix = *buf_start & (0xFF << n);

  if (value < (static_cast<uint64_t>(UINT64_C(1) << n) - 1)) {
    *(p++) = value;
  } else {
    *(p++)  = (1 << n) - 1;
    value  -= (1 << n) - 1;
    while (value >= 128) {
      if (p >= buf_end) {
        return -1;
      }
      *(p++) = (value & 0x7F) | 0x80;
      value  = value >> 7;
    }
    if (p + 1 >= buf_end) {
      return -1;
    }
    *(p++) = value;
  }

  // Restore the prefix
  *buf_start |= prefix;

  return p - buf_start;
}

int64_t
xpack_encode_string(uint8_t *buf_start, const uint8_t *buf_end, const char *value, uint64_t value_len, uint8_t n)