From df82adca43db7f5820a27624ae3e2b60c9085efd Mon Sep 17 00:00:00 2001 From: Niels Boehm Date: Thu, 22 Jun 2017 12:36:54 +0200 Subject: Add function testing whether a bitmask is valid. This one verifies bitmasks where low bits are set to 1 (hence the name). Any stray 0 among the lower ones or any stray 1 among the higher zeros renders the mask invalid. The edge cases of all zeros and all ones are considered valid masks. It uses an efficient implementation. It's the counterpart of https://graphics.stanford.edu/~seander/bithacks.html#DetermineIfPowerOf2 --- Source/UnitTests/Common/BitUtilsTest.cpp | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) (limited to 'Source/UnitTests/Common') diff --git a/Source/UnitTests/Common/BitUtilsTest.cpp b/Source/UnitTests/Common/BitUtilsTest.cpp index 987868e6e4..75f7adf50e 100644 --- a/Source/UnitTests/Common/BitUtilsTest.cpp +++ b/Source/UnitTests/Common/BitUtilsTest.cpp @@ -57,3 +57,35 @@ TEST(BitUtils, ExtractBits) // Ensure bit extraction with type overriding works as expected EXPECT_EQ((Common::ExtractBits<0, 31, s32, s32>(negative_one)), -1); } + +TEST(BitUtils, IsValidLowMask) +{ + EXPECT_TRUE(Common::IsValidLowMask(0b0u)); + EXPECT_TRUE(Common::IsValidLowMask(0b1u)); + EXPECT_FALSE(Common::IsValidLowMask(0b10u)); + EXPECT_TRUE(Common::IsValidLowMask(0b11u)); + EXPECT_FALSE(Common::IsValidLowMask(0b1110u)); + EXPECT_TRUE(Common::IsValidLowMask(0b1111u)); + EXPECT_FALSE(Common::IsValidLowMask(0b10000u)); + EXPECT_FALSE(Common::IsValidLowMask(0b101111u)); + + EXPECT_TRUE(Common::IsValidLowMask((u8)~0b0)); + EXPECT_FALSE(Common::IsValidLowMask((u8)(~0b0 - 1))); + EXPECT_FALSE(Common::IsValidLowMask((u8)~(0b10000))); + EXPECT_FALSE(Common::IsValidLowMask((u8)(~((u8)(~0b0) >> 1) | 0b1111))); + + EXPECT_TRUE(Common::IsValidLowMask((u16)~0b0)); + EXPECT_FALSE(Common::IsValidLowMask((u16)(~0b0 - 1))); + EXPECT_FALSE(Common::IsValidLowMask((u16)~(0b10000))); + EXPECT_FALSE(Common::IsValidLowMask((u16)(~((u16)(~0b0) >> 1) | 0b1111))); + + EXPECT_TRUE(Common::IsValidLowMask((u32)~0b0)); + EXPECT_FALSE(Common::IsValidLowMask((u32)(~0b0 - 1))); + EXPECT_FALSE(Common::IsValidLowMask((u32)~(0b10000))); + EXPECT_FALSE(Common::IsValidLowMask((u32)(~((u32)(~0b0) >> 1) | 0b1111))); + + EXPECT_TRUE(Common::IsValidLowMask((u64)~0b0)); + EXPECT_FALSE(Common::IsValidLowMask((u64)(~0b0 - 1))); + EXPECT_FALSE(Common::IsValidLowMask((u64)~(0b10000))); + EXPECT_FALSE(Common::IsValidLowMask((u64)(~((u64)(~0b0) >> 1) | 0b1111))); +} -- cgit v1.2.3