I need convert the following code to Java programming language. What does mean []byte{}? What is type uint8?
func int8ToByte(int_val int) byte {
buf := new(bytes.Buffer)
err := binary.Write(buf, binary.LittleEndian, uint8(int_val))
if err != nil {
log.Fatal("binary.Write failed:", err)
}
return buf.Bytes()[0]
}
[]byte{} is a composite literal which creates an empty byte slice (of type []byte). The uint8 type is an unsigned integer type whose size is 1 byte. In Go the type byte is an alias for uint8, so byte and uint8 are equivalent and completely interchangeable.
I don't know who wrote your int8ToByte() function, but that seems like an obfuscation. All it does is it returns the least significant byte of its argument, which is nothing more than a simple conversion from int to byte:
byte(int_val)
See this Go example:
func main() {
fmt.Println(int8ToByte(0x01))
fmt.Println(int8ToByte(0x0102))
fmt.Println(int8ToByte(-1))
var i int
i = 0x01
fmt.Println(byte(i))
i = 0x0102
fmt.Println(byte(i))
i = -1
fmt.Println(byte(i))
}
func int8ToByte(int_val int) byte {
buf := new(bytes.Buffer)
err := binary.Write(buf, binary.LittleEndian, uint8(int_val))
if err != nil {
log.Fatal("binary.Write failed:", err)
}
return buf.Bytes()[0]
}
It outputs (try it on the Go Playground):
1
2
255
1
2
255
To achieve the same in Java, you again just have to convert the int number to byte:
public static void main(String []args){
int i = 0x01;
System.out.println((byte)i);
i = 0x0102;
System.out.println((byte)i);
i = -1;
System.out.println((byte)i + " " + String.format("%x", (byte)i));
}
This outputs:
1
2
-1 ff
Note the difference: Java's byte is signed, it has a valid range of -128..127, while Go's byte is unsigned, its valid range is 0..255. But the binary representation of both outputs are the same. For details, see Java vs. Golang for HOTP (rfc-4226).