[arrow] branch master updated: ARROW-4653: [C++] Fix bug in decimal multiply

[ravindra]

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ravindra pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/arrow.git


The following commit(s) were added to refs/heads/master by this push:
     new 1f49604  ARROW-4653: [C++] Fix bug in decimal multiply
1f49604 is described below

commit 1f49604498dd20e224c996135ea8c57ac38f426e
Author: Pindikura Ravindra <ravin...@dremio.com>
AuthorDate: Fri Feb 22 12:16:30 2019 +0530

    ARROW-4653: [C++] Fix bug in decimal multiply
    
    - fixed a bug which was causing multiply to return an incorrect
      value when both args are -ve.
    
    Author: Pindikura Ravindra <ravin...@dremio.com>
    
    Closes #3728 from pravindra/multbug and squashes the following commits:
    
    7a7b0c2e <Pindikura Ravindra> ARROW-4653: Fix bug in decimal multiply
---
 cpp/src/arrow/util/basic_decimal.cc |  2 +-
 cpp/src/arrow/util/decimal-test.cc  | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/cpp/src/arrow/util/basic_decimal.cc 
b/cpp/src/arrow/util/basic_decimal.cc
index bb235f4..f8d3a72 100644
--- a/cpp/src/arrow/util/basic_decimal.cc
+++ b/cpp/src/arrow/util/basic_decimal.cc
@@ -243,13 +243,13 @@ BasicDecimal128& BasicDecimal128::operator*=(const 
BasicDecimal128& right) {
 
   product = L2 * R3;
   sum += product;
+  high_bits_ = static_cast<int64_t>(sum < product ? kCarryBit : 0);
 
   product = L3 * R2;
   sum += product;
 
   low_bits_ += sum << 32;
 
-  high_bits_ = static_cast<int64_t>(sum < product ? kCarryBit : 0);
   if (sum < product) {
     high_bits_ += kCarryBit;
   }
diff --git a/cpp/src/arrow/util/decimal-test.cc 
b/cpp/src/arrow/util/decimal-test.cc
index 032e02b..3d6e23d 100644
--- a/cpp/src/arrow/util/decimal-test.cc
+++ b/cpp/src/arrow/util/decimal-test.cc
@@ -466,6 +466,22 @@ TEST(Decimal128Test, TestToInteger) {
   ASSERT_RAISES(Invalid, invalid_int64.ToInteger(&out2));
 }
 
+TEST(Decimal128Test, Multiply) {
+  Decimal128 result;
+
+  result = Decimal128("301") * Decimal128("201");
+  ASSERT_EQ(result.ToIntegerString(), "60501");
+
+  result = Decimal128("-301") * Decimal128("201");
+  ASSERT_EQ(result.ToIntegerString(), "-60501");
+
+  result = Decimal128("301") * Decimal128("-201");
+  ASSERT_EQ(result.ToIntegerString(), "-60501");
+
+  result = Decimal128("-301") * Decimal128("-201");
+  ASSERT_EQ(result.ToIntegerString(), "60501");
+}
+
 TEST(Decimal128Test, GetWholeAndFraction) {
   Decimal128 value("123456");
   Decimal128 whole;