portable byteswap.h

byteswap.h comes from glibc, doesn't work on mac

Author: JJJollyjim

arcompact/arcompact.cpp

@@ -1,4 +1,11 @@
+#if HAVE_BYTESWAP_H
 #include <byteswap.h>
+#else
+#define bswap_16(value) ((((value) & 0xff) << 8) | ((value) >> 8))
+#define bswap_32(value) (((uint32_t)bswap_16((uint16_t)((value) & 0xffff)) << 16) | (uint32_t)bswap_16((uint16_t)((value) >> 16)))
+#define bswap_64(value) (((uint64_t)bswap_32((uint32_t)((value) & 0xffffffff)) << 32) | (uint64_t)bswap_32((uint32_t)((value) >> 32)))
+#endif
+
 #include <cstdint>
 #include <stdlib.h>
 #include <stdio.h>
@@ -1995,4 +2002,4 @@ namespace ArCompact {
 
 		return result;
 	}
-}
+}