Function UInt64FromBigEndian

cpp/src/arrow/util/decimal.cc:1091–1102

Helper function used by Decimal128::FromBigEndian

// Helper function used by Decimal128::FromBigEndian
static inline uint64_t UInt64FromBigEndian(const uint8_t* bytes, int32_t length) {
  // We don't bounds check the length here because this is called by
  // FromBigEndian that has a Decimal128 as its out parameters and
  // that function is already checking the length of the bytes and only
  // passes lengths between zero and eight.
  uint64_t result = 0;
  // Using memcpy instead of special casing for length
  // and doing the conversion in 16, 32 parts, which could
  // possibly create unaligned memory access on certain platforms
  memcpy(reinterpret_cast<uint8_t*>(&result) + 8 - length, bytes, length);
  return ::arrow::bit_util::FromBigEndian(result);
}

Result<Decimal32> Decimal32::FromBigEndian(const uint8_t* bytes, int32_t length) {
  static constexpr int32_t kMinDecimalBytes = 1;