添加函数 MathUtil::popcount，用于计算一个数字中二进制1的个数

source/core/include/math/dvc_math_util.h

@@ -10,6 +10,11 @@ class MathUtil
 public:
 	static size_t ComponentSize(ComponentType ct);
 	static size_t DataTypeSize(DataType dt);
+	
+	//count the number of bits set in v
+	static DV_CORE_API uint32_t popcount(uint8_t v);
+	static DV_CORE_API uint32_t popcount(uint16_t v);
+	static DV_CORE_API uint32_t popcount(uint32_t v);
 
 	static bool floatEqual(float a, float b,
 		float tolerance = std::numeric_limits<float>::epsilon()) {

source/core/source/math/dvc_math_util.cpp

@@ -11,6 +11,31 @@ const float MathUtil::PI_DIV4 = float(0.25 * PI);
 const float MathUtil::fDeg2Rad = PI / float(180.0);
 const float MathUtil::fRad2Deg = float(180.0) / PI;
 
+static const uint8_t kBitsSetTable256[256] =
+{
+#define B2(n) n,     n+1,     n+1,     n+2
+#define B4(n) B2(n), B2(n+1), B2(n+1), B2(n+2)
+#define B6(n) B4(n), B4(n+1), B4(n+1), B4(n+2)
+
+	B6(0), B6(1), B6(1), B6(2)
+};
+
+uint32_t MathUtil::popcount(uint8_t v)
+{
+	return kBitsSetTable256[v];
+}
+
+uint32_t MathUtil::popcount(uint16_t v)
+{
+	return kBitsSetTable256[v & 0xff] + kBitsSetTable256[(v >> 8) & 0xff];
+}
+
+uint32_t MathUtil::popcount(uint32_t v)
+{
+	return kBitsSetTable256[v & 0xff] + kBitsSetTable256[(v >> 8) & 0xff] +
+		kBitsSetTable256[(v >> 16) & 0xff] + kBitsSetTable256[v >> 24];
+}
+
 size_t MathUtil::ComponentSize(ComponentType ct)
 {
 	switch (ct)

test/unit/dvt_unit_math_util.cpp

@@ -76,4 +76,26 @@ TEST(MathUtil, Basic)
 			EXPECT_EQ_4X4_T_APPROX(m1, gm1, std::numeric_limits<float>::epsilon() * 100);
 		}
 	}
+
+	//couting bit set
+	{
+		EXPECT_EQ(MathUtil::popcount((uint8_t)(0x0)), 0);
+		EXPECT_EQ(MathUtil::popcount((uint8_t)(0xFF)), 8);
+		EXPECT_EQ(MathUtil::popcount((uint16_t)(0x0)), 0);
+		EXPECT_EQ(MathUtil::popcount((uint16_t)(0xFFFF)), 16);
+		EXPECT_EQ(MathUtil::popcount((uint32_t)(0x0)), 0);
+		EXPECT_EQ(MathUtil::popcount((uint32_t)(0xFFFFFFFF)), 32);
+
+		for(int32_t i=0; i<100; i++)
+		{
+			uint8_t v8 = (uint8_t)MathUtil::rangeRandom(0, 0xFF);
+			EXPECT_EQ(MathUtil::popcount(v8), __popcnt(v8));
+
+			uint16_t v16 = (uint16_t)MathUtil::rangeRandom(0, 0xFFFF);
+			EXPECT_EQ(MathUtil::popcount(v16), __popcnt(v16));
+
+			uint32_t v32 = (uint32_t)MathUtil::rangeRandom(0, 0x7FFFFF);
+			EXPECT_EQ(MathUtil::popcount(v32), __popcnt(v32));
+		}
+	}
 }