Unsigned Bytes CRC32 in Java

Question

I'm trying to replicate the CRC32 hashing function that is available in PHP in Java. The existing CRC32 class within Java returns a different hash and I believe it is because the Java bytes in my byte array are unsigned -128 through 128 instead of 0-255.

What I'm failing to figured out is how to work around this situation. I've looked at using Guava's UnsignedBytes, but I can't find a hashing method that takes it as an argument. I could use that to write my own hashing function, but frankly I don't nearly enough about how it works or bitwise arithmetic in general to make that plausible.

In the simplest terms I'm trying to CRC32 has a string and return the decimal representation.

Answer 1

CRC does not care about sign.

Java's CRC32 gave me same result than PHP's.

public static void main(String[] args) {
    String a = "Hello World!";
    CRC32 crc = new CRC32();
    crc.update(a.getBytes());
    System.out.println(Long.toHexString(crc.getValue()));
}

Outputs: 1c291ca3

Using this online PHP CRC32 calculator gave the same CRC value than above Java code.