byteswapping: move declaration into source file

src/sp/common/ByteSwapping.cpp

@@ -0,0 +1,74 @@
+#include <sp/common/ByteSwapping.h>
+
+#ifdef _WIN32
+#include <winsock2.h>
+#else
+#include <arpa/inet.h>
+#endif
+
+#include <algorithm>
+
+namespace sp {
+
+template <typename T>
+void SwapBytes(T& value) {
+	char* ptr = reinterpret_cast<char*>(&value);
+	std::reverse(ptr, ptr + sizeof(T));
+}
+
+bool IsSystemBigEndian() {
+	static constexpr std::uint16_t test = 10;
+	static const bool isBigEndian = reinterpret_cast<const std::uint8_t*>(&test)[1] == 10;
+	return isBigEndian;
+}
+
+template <>
+void ToNetwork<std::uint16_t>(std::uint16_t& value) {
+	value = htons(value);
+}
+
+template <>
+void ToNetwork<std::uint32_t>(std::uint32_t& value) {
+	value = htonl(value);
+}
+
+template <>
+void ToNetwork<std::uint64_t>(std::uint64_t& value) {
+	if (IsSystemBigEndian())
+		return;
+	SwapBytes(value);
+}
+
+template <>
+void FromNetwork<std::uint16_t>(std::uint16_t& value) {
+	value = ntohs(value);
+}
+
+template <>
+void FromNetwork<std::uint32_t>(std::uint32_t& value) {
+	value = ntohl(value);
+}
+
+template <>
+void FromNetwork<std::uint64_t>(std::uint64_t& value) {
+	if (IsSystemBigEndian())
+		return;
+	SwapBytes(value);
+}
+
+template <>
+void TrySwapBytes<std::uint16_t>(std::uint16_t& value) {
+	SwapBytes(value);
+}
+
+template <>
+void TrySwapBytes<std::uint32_t>(std::uint32_t& value) {
+	SwapBytes(value);
+}
+
+template <>
+void TrySwapBytes<std::uint64_t>(std::uint64_t& value) {
+	SwapBytes(value);
+}
+
+}  // namespace sp