some efficient mathematical hacks for powers of two

Author: toschmidt

src/cpp-utility/math/Math.hpp

@@ -0,0 +1,57 @@
+#pragma once
+
+#include <cpp-utility/compiler/CompilerHints.hpp>
+
+namespace utility::math {
+
+   template<typename T>
+   forceinline constexpr bool is_power_of_two(T x) {
+      return (x == 1) | (x && ((x & (x - 1)) == 0));
+   }
+
+   template<typename T>
+   forceinline constexpr T next_power_of_two(T value) {
+      if (unlikely(value == 0)) {
+         return 0;
+      } else if (unlikely(value == 1)) {
+         return 1;
+      } else {
+         if constexpr (sizeof(T) == 4) {
+            return 1ull << ((sizeof(T) << 3) - __builtin_clz(value - 1));
+         } else {
+            return 1ull << ((sizeof(T) << 3) - __builtin_clzll(value - 1));
+         }
+      }
+   }
+
+   template<typename T>
+   forceinline constexpr T prev_power_of_two(T value) {
+      return next_power_of_two(value) >> 1;
+   }
+
+   template<typename T>
+   forceinline constexpr T get_number_of_bits(T value) {
+      if (value == 0) {
+         return 0;
+      } else if (value == 1) {
+         return 1;
+      } else {
+         if constexpr (sizeof(T) == 4) {
+            return (sizeof(T) << 3) - __builtin_clz(value - 1);
+         } else {
+            return (sizeof(T) << 3) - __builtin_clzll(value - 1);
+         }
+      }
+   }
+
+   template<typename T>
+   forceinline constexpr T align_number(const T& value, const T& align) {
+      return ((value + align - 1) / align) * align;
+   }
+
+   template<typename T>
+   forceinline constexpr T const_log2(const T n) {
+      return (n < 2) ? 0 : 1 + const_log2(n / 2);
+   }
+
+} // namespace utility::math