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ARROW-914 [C++/Python] Fix Decimal ToBytes #613

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cpcloud wants to merge 2 commits into from
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ARROW-914 [C++/Python] Fix Decimal ToBytes #613

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ARROW-914 [C++/Python] Fix Decimal ToBytes
cpcloud Apr 29, 2017
b0f3c10
Use a more appropriate name
cpcloud Apr 29, 2017
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3 changes: 1 addition & 2 deletions ci/msvc-build.bat
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Expand Up @@ -53,5 +53,4 @@ cd ..\..\python
python setup.py build_ext --inplace || exit /B
python -c "import pyarrow" || exit /B

@rem TODO: re-enable when last tests are fixed
@rem py.test pyarrow -v -s || exit /B
py.test pyarrow -v -s || exit /B
8 changes: 4 additions & 4 deletions cpp/src/arrow/util/decimal.cc
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Expand Up @@ -147,15 +147,15 @@ void FromBytes(const uint8_t* bytes, Decimal64* decimal) {
constexpr static const size_t BYTES_IN_128_BITS = 128 / CHAR_BIT;
constexpr static const size_t LIMB_SIZE =
sizeof(std::remove_pointer<int128_t::backend_type::limb_pointer>::type);
constexpr static const size_t BYTES_PER_LIMB = BYTES_IN_128_BITS / LIMB_SIZE;
constexpr static const size_t LIMBS_IN_INT128 = BYTES_IN_128_BITS / LIMB_SIZE;

void FromBytes(const uint8_t* bytes, bool is_negative, Decimal128* decimal) {
DCHECK_NE(bytes, nullptr);
DCHECK_NE(decimal, nullptr);

auto& decimal_value(decimal->value);
int128_t::backend_type& backend(decimal_value.backend());
backend.resize(BYTES_PER_LIMB, BYTES_PER_LIMB);
backend.resize(LIMBS_IN_INT128, LIMBS_IN_INT128);
std::memcpy(backend.limbs(), bytes, BYTES_IN_128_BITS);
if (is_negative) { decimal->value = -decimal->value; }
}
Expand All @@ -177,8 +177,8 @@ void ToBytes(const Decimal128& decimal, uint8_t** bytes, bool* is_negative) {
/// TODO(phillipc): boost multiprecision is unreliable here, int128_t can't be
/// roundtripped
const auto& backend(decimal.value.backend());
auto boost_bytes = reinterpret_cast<const uint8_t*>(backend.limbs());
std::memcpy(*bytes, boost_bytes, BYTES_IN_128_BITS);
const size_t bytes_in_use = LIMB_SIZE * backend.size();
std::memcpy(*bytes, backend.limbs(), bytes_in_use);
*is_negative = backend.isneg();
}

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