MingyuZhong commented on a change in pull request #8542:
URL: https://github.com/apache/arrow/pull/8542#discussion_r517062023
##########
File path: cpp/src/arrow/util/basic_decimal.cc
##########
@@ -404,51 +429,33 @@ BasicDecimal128& BasicDecimal128::operator*=(const
BasicDecimal128& right) {
/// \result the output length of the array
static int64_t FillInArray(const BasicDecimal128& value, uint32_t* array,
bool& was_negative) {
- uint64_t high;
- uint64_t low;
- const int64_t highbits = value.high_bits();
- const uint64_t lowbits = value.low_bits();
-
- if (highbits < 0) {
- low = ~lowbits + 1;
- high = static_cast<uint64_t>(~highbits);
- if (low == 0) {
- ++high;
- }
- was_negative = true;
- } else {
- low = lowbits;
- high = static_cast<uint64_t>(highbits);
- was_negative = false;
- }
-
- if (high != 0) {
- if (high > std::numeric_limits<uint32_t>::max()) {
- array[0] = static_cast<uint32_t>(high >> 32);
- array[1] = static_cast<uint32_t>(high);
- array[2] = static_cast<uint32_t>(low >> 32);
- array[3] = static_cast<uint32_t>(low);
- return 4;
- }
-
- array[0] = static_cast<uint32_t>(high);
- array[1] = static_cast<uint32_t>(low >> 32);
- array[2] = static_cast<uint32_t>(low);
- return 3;
- }
-
- if (low >= std::numeric_limits<uint32_t>::max()) {
- array[0] = static_cast<uint32_t>(low >> 32);
- array[1] = static_cast<uint32_t>(low);
- return 2;
- }
+ BasicDecimal128 abs_value = BasicDecimal128::Abs(value);
+ was_negative = value.high_bits() < 0;
+ std::array<uint64_t, 2> abs_big_endian_array = {
+ static_cast<uint64_t>(abs_value.high_bits()),
+ static_cast<uint64_t>(abs_value.low_bits())};
+ return FillInArray(abs_big_endian_array, array);
+}
- if (low == 0) {
- return 0;
+/// Expands the given value into an array of ints so that we can work on
+/// it. The array will be converted to an absolute value and the wasNegative
+/// flag will be set appropriately. The array will remove leading zeros from
+/// the value.
+/// \param array an array of length 8 to set with the value
+/// \param was_negative a flag for whether the value was original negative
+/// \result the output length of the array
+static int64_t FillInArray(const BasicDecimal256& value, uint32_t* array,
+ bool& was_negative) {
+ BasicDecimal256 positive_value = value;
+ was_negative = false;
+ int64_t highest_bit = positive_value.little_endian_array()[3];
+ if (highest_bit < 0) {
+ positive_value.Negate();
+ was_negative = true;
}
-
- array[0] = static_cast<uint32_t>(low);
- return 1;
+ std::array<uint64_t, 4> value_big_endian_array =
positive_value.little_endian_array();
+ std::reverse(value_big_endian_array.begin(), value_big_endian_array.end());
Review comment:
Can FillInArray below take little-endian array so you don't need to call
std::reverse?
##########
File path: cpp/src/arrow/util/basic_decimal.cc
##########
@@ -451,6 +463,27 @@ static int64_t FillInArray(const BasicDecimal128& value,
uint32_t* array,
return 1;
}
+/// Expands the given value into an array of ints so that we can work on
Review comment:
Comment that the output array is in big-endian.
##########
File path: cpp/src/arrow/util/basic_decimal.cc
##########
@@ -451,6 +463,27 @@ static int64_t FillInArray(const BasicDecimal128& value,
uint32_t* array,
return 1;
}
+/// Expands the given value into an array of ints so that we can work on
+/// it. The array will be converted to an absolute value and the wasNegative
Review comment:
was_negative
##########
File path: cpp/src/arrow/util/basic_decimal.cc
##########
@@ -404,23 +429,10 @@ BasicDecimal128& BasicDecimal128::operator*=(const
BasicDecimal128& right) {
/// \result the output length of the array
static int64_t FillInArray(const BasicDecimal128& value, uint32_t* array,
bool& was_negative) {
- uint64_t high;
- uint64_t low;
- const int64_t highbits = value.high_bits();
- const uint64_t lowbits = value.low_bits();
-
- if (highbits < 0) {
- low = ~lowbits + 1;
- high = static_cast<uint64_t>(~highbits);
- if (low == 0) {
- ++high;
- }
- was_negative = true;
- } else {
- low = lowbits;
- high = static_cast<uint64_t>(highbits);
- was_negative = false;
- }
+ BasicDecimal128 abs_value = BasicDecimal128::Abs(value);
+ was_negative = value.high_bits() < 0;
+ uint64_t high = static_cast<uint64_t>(abs_value.high_bits());
Review comment:
Please add a comment about why FillInArray is not called.
##########
File path: cpp/src/arrow/util/basic_decimal.cc
##########
@@ -395,6 +395,31 @@ BasicDecimal128& BasicDecimal128::operator*=(const
BasicDecimal128& right) {
return *this;
}
+/// Expands the given big endian array of uint64_t into an array of uint32_t.
+/// The value of input array is expected to be positive. The result_array will
Review comment:
positive -> non-negative?
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