thisisnic commented on code in PR #53946:
URL: https://github.com/apache/arrow/pull/53946#discussion_r4292516922
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cpp/src/arrow/util/bit_util_test.cc:
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@@ -1108,4 +1108,46 @@ TEST(BitUtil, CopyBits) {
0b01011010);
}
+TEST(BitUtil, BitWidth) {
+ EXPECT_EQ(bit_util::BitWidth(uint8_t{0}), 0);
+ EXPECT_EQ(bit_util::BitWidth(uint8_t{1}), 1);
+ EXPECT_EQ(bit_util::BitWidth(uint8_t{2}), 2);
+ EXPECT_EQ(bit_util::BitWidth(uint8_t{3}), 2);
+ EXPECT_EQ(bit_util::BitWidth(uint8_t{127}), 7);
+ EXPECT_EQ(bit_util::BitWidth(uint8_t{128}), 8);
+ EXPECT_EQ(bit_util::BitWidth(std::numeric_limits<uint8_t>::max()), 8);
+
+ EXPECT_EQ(bit_util::BitWidth(uint32_t{0}), 0);
+ EXPECT_EQ(bit_util::BitWidth(uint32_t{1} << 20), 21);
+ EXPECT_EQ(bit_util::BitWidth((uint32_t{1} << 20) - 1), 20);
+ EXPECT_EQ(bit_util::BitWidth(std::numeric_limits<uint32_t>::max()), 32);
+
+ EXPECT_EQ(bit_util::BitWidth(uint64_t{0}), 0);
+ EXPECT_EQ(bit_util::BitWidth(uint64_t{1} << 40), 41);
+ EXPECT_EQ(bit_util::BitWidth((uint64_t{1} << 40) - 1), 40);
+ EXPECT_EQ(bit_util::BitWidth(uint64_t{1} << 63), 64);
+ EXPECT_EQ(bit_util::BitWidth(std::numeric_limits<uint64_t>::max()), 64);
+
+ // constexpr-evaluable.
+ static_assert(bit_util::BitWidth(uint16_t{0x0100}) == 9);
+}
+
+TEST(BitUtil, HasSingleBit) {
+ EXPECT_FALSE(bit_util::HasSingleBit(uint8_t{0}));
+ EXPECT_TRUE(bit_util::HasSingleBit(uint8_t{1}));
+ EXPECT_TRUE(bit_util::HasSingleBit(uint8_t{2}));
+ EXPECT_FALSE(bit_util::HasSingleBit(uint8_t{3}));
+ EXPECT_TRUE(bit_util::HasSingleBit(uint8_t{128}));
+ EXPECT_FALSE(bit_util::HasSingleBit(std::numeric_limits<uint8_t>::max()));
+
+ EXPECT_TRUE(bit_util::HasSingleBit(uint32_t{1} << 20));
+ EXPECT_FALSE(bit_util::HasSingleBit((uint32_t{1} << 20) + 1));
+ EXPECT_TRUE(bit_util::HasSingleBit(uint64_t{1} << 63));
+ EXPECT_FALSE(bit_util::HasSingleBit(std::numeric_limits<uint64_t>::max()));
+
+ // constexpr-evaluable.
+ static_assert(bit_util::HasSingleBit(uint16_t{0x0100}));
+ static_assert(!bit_util::HasSingleBit(uint16_t{0x0101}));
+}
Review Comment:
I feel like this is overtesting given that on most platforms are using the
existing functions internally, so I'll trim this down
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