Class ValueUnion

deps/google-benchmark/src/sysinfo.cc:96–140

ValueUnion - A type used to correctly alias the byte-for-byte output of `sysctl` with the result type it's to be interpreted as.

/// ValueUnion - A type used to correctly alias the byte-for-byte output of
/// `sysctl` with the result type it's to be interpreted as.
struct ValueUnion {
  union DataT {
    int32_t int32_value;
    int64_t int64_value;
    // For correct aliasing of union members from bytes.
    char bytes[8];
  };
  using DataPtr = std::unique_ptr<DataT, decltype(&std::free)>;

  // The size of the data union member + its trailing array size.
  std::size_t size;
  DataPtr buff;

 public:
  ValueUnion() : size(0), buff(nullptr, &std::free) {}

  explicit ValueUnion(std::size_t buff_size)
      : size(sizeof(DataT) + buff_size),
        buff(::new (std::malloc(size)) DataT(), &std::free) {}

  ValueUnion(ValueUnion&& other) = default;

  explicit operator bool() const { return bool(buff); }

  char* data() const { return buff->bytes; }

  std::string GetAsString() const { return std::string(data()); }

  int64_t GetAsInteger() const {
    if (size == sizeof(buff->int32_value))
      return buff->int32_value;
    else if (size == sizeof(buff->int64_value))
      return buff->int64_value;
    BENCHMARK_UNREACHABLE();
  }

  template <class T, int N>
  std::array<T, N> GetAsArray() {
    const int arr_size = sizeof(T) * N;
    BM_CHECK_LE(arr_size, size);
    std::array<T, N> arr;
    std::memcpy(arr.data(), data(), arr_size);
    return arr;
  }
};

ValueUnion GetSysctlImp(std::string const& name) {
#if defined BENCHMARK_OS_OPENBSD