[geos-commits] [SCM] GEOS branch master updated. 311b64a08768c3d4f2329ec4647070928058bcd2

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- Log -----------------------------------------------------------------
commit 311b64a08768c3d4f2329ec4647070928058bcd2
Author: Paul Ramsey <pramsey at cleverelephant.ca>
Date:   Wed Sep 18 08:37:46 2019 -0700

    Improve the bit-shifting logic with good types and so on
    Even Roualt, Kurt Schwehr
    References #869

diff --git a/src/precision/CommonBits.cpp b/src/precision/CommonBits.cpp
index a960803..b2ba370 100644
--- a/src/precision/CommonBits.cpp
+++ b/src/precision/CommonBits.cpp
@@ -44,11 +44,12 @@ CommonBits::numCommonMostSigMantissaBits(int64 num1, int64 num2)
 int64
 CommonBits::zeroLowerBits(int64 bits, int nBits)
 {
-    if (nBits >= 64) return 0;
-    int64 invMask = (1 << nBits) - 1;
-    int64 mask = ~ invMask;
-    int64 zeroed = bits & mask;
-    return zeroed;
+    if (nBits >= 64 || nBits < 1) return 0;
+    const uint64_t bits_ = static_cast<uint64_t>(bits);
+    const uint64_t invMask = (1ull << nBits) - 1;
+    const uint64_t mask = ~ invMask;
+    const uint64_t zeroed = bits_ & mask;
+    return static_cast<int64>(zeroed);
 }
 
 /*static public*/
diff --git a/tests/unit/precision/CommonBitsTest.cpp b/tests/unit/precision/CommonBitsTest.cpp
index 02e36df..3ddea74 100644
--- a/tests/unit/precision/CommonBitsTest.cpp
+++ b/tests/unit/precision/CommonBitsTest.cpp
@@ -53,4 +53,28 @@ void object::test<3>
     ensure_equals(CommonBits::getBit(val, 63), 1);
 }
 
+// zeroLowerBits.
+template<>
+template<>
+void object::test<4>()
+{
+    constexpr int64 val = static_cast<int64>(0xffffffffffffffffull);
+    ensure_equals(sizeof(val), 8);
+
+    ensure_equals(CommonBits::zeroLowerBits(val, -1), 0);
+    ensure_equals(CommonBits::zeroLowerBits(val, 0), 0);
+    ensure_equals(CommonBits::zeroLowerBits(val, 1), -2);
+    ensure_equals(CommonBits::zeroLowerBits(val, 2), -4);
+    ensure_equals(CommonBits::zeroLowerBits(val, 16), -65536);
+    ensure_equals(CommonBits::zeroLowerBits(val, 31), -2147483648ll);
+    ensure_equals(CommonBits::zeroLowerBits(val, 32), -4294967296ll);
+    ensure_equals(CommonBits::zeroLowerBits(val, 62), -4611686018427387904ll);
+    ensure_equals(static_cast<uint64_t>(CommonBits::zeroLowerBits(val, 62)), 0xc000000000000000ull);
+    ensure_equals(static_cast<uint64_t>(CommonBits::zeroLowerBits(val, 63)), 9223372036854775808ull);
+    ensure_equals(static_cast<uint64_t>(CommonBits::zeroLowerBits(val, 63)), 0x8000000000000000ull);
+    ensure_equals(CommonBits::zeroLowerBits(val, 64), 0);
+    ensure_equals(CommonBits::zeroLowerBits(val, 10000), 0);
+}
+
+
 } // namespace tut

-----------------------------------------------------------------------

Summary of changes:
 src/precision/CommonBits.cpp            | 11 ++++++-----
 tests/unit/precision/CommonBitsTest.cpp | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 5 deletions(-)


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