Use builtin bitswap for endian on windows

Signed-off-by: R4SAS <r4sas@i2pmail.org>

libi2pd/I2PEndian.cpp

@@ -50,42 +50,3 @@ uint64_t be64toh(uint64_t big64)
 	return u64.raw_value;
 }
 #endif
-
-/* it can be used in Windows 8
-#include <Winsock2.h>
-
-uint16_t htobe16(uint16_t int16)
-{
-	return htons(int16);
-}
-
-uint32_t htobe32(uint32_t int32)
-{
-	return htonl(int32);
-}
-
-uint64_t htobe64(uint64_t int64)
-{
-	// http://msdn.microsoft.com/en-us/library/windows/desktop/jj710199%28v=vs.85%29.aspx
-	//return htonll(int64);
-	return 0;
-}
-
-
-uint16_t be16toh(uint16_t big16)
-{
-	return ntohs(big16);
-}
-
-uint32_t be32toh(uint32_t big32)
-{
-	return ntohl(big32);
-}
-
-uint64_t be64toh(uint64_t big64)
-{
-	// http://msdn.microsoft.com/en-us/library/windows/desktop/jj710199%28v=vs.85%29.aspx
-	//return ntohll(big64);
-	return 0;
-}
-*/

libi2pd/I2PEndian.h

@@ -13,10 +13,11 @@
 
 #if defined(__FreeBSD__) || defined(__NetBSD__)
 #include <sys/endian.h>
+
 #elif defined(__linux__) || defined(__FreeBSD_kernel__) || defined(__OpenBSD__) || defined(__GLIBC__)
 #include <endian.h>
-#elif defined(__APPLE__) && defined(__MACH__)
 
+#elif defined(__APPLE__) && defined(__MACH__)
 #include <libkern/OSByteOrder.h>
 
 #define htobe16(x) OSSwapHostToBigInt16(x)
@@ -34,6 +35,22 @@
 #define be64toh(x) OSSwapBigToHostInt64(x)
 #define le64toh(x) OSSwapLittleToHostInt64(x)
 
+#elif defined(_WIN32)
+#define htobe16(x) __builtin_bswap16(x)
+#define htole16(x) (x)
+#define be16toh(x) __builtin_bswap16(x)
+#define le16toh(x) (x)
+
+#define htobe32(x) __builtin_bswap32(x)
+#define htole32(x) (x)
+#define be32toh(x) __builtin_bswap32(x)
+#define le32toh(x) (x)
+
+#define htobe64(x) __builtin_bswap64(x)
+#define htole64(x) (x)
+#define be64toh(x) __builtin_bswap64(x)
+#define le64toh(x) (x)
+
 #else
 #define NEEDS_LOCAL_ENDIAN
 #include <cstdint>