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)