Function ConsumeDecimalNumber

src/leveldb/util/logging.cc:51–82

}

bool ConsumeDecimalNumber(Slice* in, uint64_t* val) {
  // Constants that will be optimized away.
  constexpr const uint64_t kMaxUint64 = std::numeric_limits<uint64_t>::max();
  constexpr const char kLastDigitOfMaxUint64 =
      '0' + static_cast<char>(kMaxUint64 % 10);

  uint64_t value = 0;

  // reinterpret_cast-ing from char* to uint8_t* to avoid signedness.
  const uint8_t* start = reinterpret_cast<const uint8_t*>(in->data());

  const uint8_t* end = start + in->size();
  const uint8_t* current = start;
  for (; current != end; ++current) {
    const uint8_t ch = *current;
    if (ch < '0' || ch > '9') break;

    // Overflow check.
    // kMaxUint64 / 10 is also constant and will be optimized away.
    if (value > kMaxUint64 / 10 ||
        (value == kMaxUint64 / 10 && ch > kLastDigitOfMaxUint64)) {
      return false;
    }

    value = (value * 10) + (ch - '0');
  }

  *val = value;
  const size_t digits_consumed = current - start;
  in->remove_prefix(digits_consumed);
  return digits_consumed != 0;
}

}  // namespace leveldb