Optimize byte order handling

nl/nl_linux.go

@@ -30,22 +30,34 @@ func GetIPFamily(ip net.IP) int {
 	}
 	return FAMILY_V6
 }
+
+var nativeEndian binary.ByteOrder
+
 // Get native endianness for the system
 func NativeEndian() binary.ByteOrder {
-	var x uint32 = 0x01020304
-	if *(*byte)(unsafe.Pointer(&x)) == 0x01 {
-		return binary.BigEndian
+	if nativeEndian == nil {
+		var x uint32 = 0x01020304
+		if *(*byte)(unsafe.Pointer(&x)) == 0x01 {
+			nativeEndian = binary.BigEndian
+		}
+		nativeEndian = binary.LittleEndian
 	}
-	return binary.LittleEndian
+	return nativeEndian
 }
 
-// Byte swap a 16 bit value in place
+// Byte swap a 16 bit value if we aren't big endian
 func Swap16(i uint16) uint16 {
+	if NativeEndian() == binary.BigEndian {
+		return i
+	}
 	return (i&0xff00)>>8 | (i&0xff)<<8
 }
 
-// Byte swap a 32 bit value in place
+// Byte swap a 32 bit value if aren't big endian
 func Swap32(i uint32) uint32 {
+	if NativeEndian() == binary.BigEndian {
+		return i
+	}
 	return (i&0xff000000)>>24 | (i&0xff0000)>>8 | (i&0xff00)<<8 | (i&0xff)<<24
 }