Utility functions for little-endian <-> big-endian conversion.

components/misc/endianness.hpp

@@ -0,0 +1,82 @@
+#ifndef COMPONENTS_MISC_ENDIANNESS_H
+#define COMPONENTS_MISC_ENDIANNESS_H
+
+#include <cstdint>
+
+namespace Misc
+{
+
+    // Two-way conversion little-endian <-> big-endian
+    template <typename T>
+    void swapEndiannessInplace(T& v)
+    {
+        static_assert(std::is_arithmetic_v<T>);
+        static_assert(sizeof(T) == 1 || sizeof(T) == 2 || sizeof(T) == 4 || sizeof(T) == 8);
+
+        if constexpr (sizeof(T) == 2)
+        {
+            uint16_t& v16 = *reinterpret_cast<uint16_t*>(&v);
+            v16 = (v16 >> 8) | (v16 << 8);
+        }
+        if constexpr (sizeof(T) == 4)
+        {
+            uint32_t& v32 = *reinterpret_cast<uint32_t*>(&v);
+            v32 = (v32 >> 24) | ((v32 >> 8) & 0xff00) | ((v32 & 0xff00) << 8) || v32 << 24;
+        }
+        if constexpr (sizeof(T) == 8)
+        {
+            uint64_t& v64 = *reinterpret_cast<uint64_t*>(&v);
+            v64 = (v64 >> 56) | ((v64 & 0x00ff'0000'0000'0000) >> 40) | ((v64 & 0x0000'ff00'0000'0000) >> 24)
+                | ((v64 & 0x0000'00ff'0000'0000) >> 8) | ((v64 & 0x0000'0000'ff00'0000) << 8)
+                | ((v64 & 0x0000'0000'00ff'0000) << 24) | ((v64 & 0x0000'0000'0000'ff00) << 40) | (v64 << 56);
+        }
+    }
+
+    #ifdef _WIN32
+    constexpr bool IS_LITTLE_ENDIAN = true;
+    constexpr bool IS_BIG_ENDIAN = false;
+    #else
+    constexpr bool IS_LITTLE_ENDIAN = __BYTE_ORDER__ != __ORDER_BIG_ENDIAN__;
+    constexpr bool IS_BIG_ENDIAN = __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__;
+    #endif
+
+    // Usage: swapEndiannessInplaceIf<IS_BIG_ENDIAN>(v)  - native to little-endian or back
+    //        swapEndiannessInplaceIf<IS_LITTLE_ENDIAN>(v)  - native to big-endian or back
+    template <bool C, typename T>
+    void swapEndiannessInplaceIf(T& v)
+    {
+        static_assert(std::is_arithmetic_v<T>);
+        static_assert(sizeof(T) == 1 || sizeof(T) == 2 || sizeof(T) == 4 || sizeof(T) == 8);
+        if constexpr (C)
+            swapEndiannessInplace(v);
+    }
+
+    template <typename T>
+    T toLittleEndian(T v)
+    {
+        swapEndiannessInplaceIf<IS_BIG_ENDIAN>(v);
+        return v;
+    }
+    template <typename T>
+    T fromLittleEndian(T v)
+    {
+        swapEndiannessInplaceIf<IS_BIG_ENDIAN>(v);
+        return v;
+    }
+
+    template <typename T>
+    T toBigEndian(T v)
+    {
+        swapEndiannessInplaceIf<IS_LITTLE_ENDIAN>(v);
+        return v;
+    }
+    template <typename T>
+    T fromBigEndian(T v)
+    {
+        swapEndiannessInplaceIf<IS_LITTLE_ENDIAN>(v);
+        return v;
+    }
+
+}
+
+#endif // COMPONENTS_MISC_ENDIANNESS_H