Decision
I had a mistake in my internal conversion logic.
ORIGINAL QUESTION
I need to implement the algorithm in both Java and JavaScript, while the result of Java implementation and calculation is a link. However, when calling the XOR operator with a โnegativeโ value (I know that Java and JavaScript use 2 additions), the Java result is positive, while the JavaScript result is negative, as shown in the following figure:
Java output:
hash A: 16777619
hash B: 637696617
hash A: 637696613
hash B: 988196095
hash A: 988196062
hash B: -1759370886
hash A: 1759370917 <-- here the JavaScript implementation behaves different
hash B: -1169850945
JavaScript output:
hash A: 16777619
hash B: 637696617
hash A: 637696613
hash B: 988196095
hash A: 988196062
hash B: -1759370886
hash A: -1759370843 <-- this result should be equal to the Java result
hash B: -1883572545
Below you can see the Java source code:
private static final int FNV_PRIME = 0x1000193;
private static final int FNV_COMPRESS = 0xFFFF;
...
public long getHash(int inputNumber)
{
int hash = FNVCalculator.FNV_PRIME;
ByteBuffer intToByteArrayConverter = ByteBuffer.allocate(4);
intToByteArrayConverter.putInt(inputNumber);
byte[] inputValues = intToByteArrayConverter.array();
for (byte processCounter = (byte) 0; processCounter < inputValues.length; processCounter++)
{
hash ^= inputValues[processCounter];
System.out.println("hash A: " + hash);
hash *= FNV_PRIME;
System.out.println("hash B: " + hash);
}
return (hash & FNVCalculator.FNV_COMPRESS);
}
The following snippet shows the JavaScript code:
var Constants =
{
FNV_PRIME: parseInt("1000193", 16),
FNV_COMPRESS: parseInt("FFFF", 16),
BYTE_ARRAY_LENGTH: 4,
...
};
Object.freeze(Constants);
var hash = Constants.FNV_PRIME;
for (var counter = 0; counter < Constants.BYTE_ARRAY_LENGTH; counter++)
{
hash ^= inputNumberArray[counter];
console.log("hash A: " + hash);
// mutltiply the hash with the 32 bit FNV prime number: 2^24 + 2^8 + 0x93
// source: https://github.com/wiedi/node-fnv/blob/master/fnv.js
hash += ((hash << 24) + (hash << 8) + (hash << 7) + (hash << 4) + (hash << 1));
hash |= 0;
console.log("hash B: " + hash);
}
return (hash & Constants.FNV_COMPRESS);
An array of numbers is equal in both Java and the JavaScript version, as shown below (all numbers are decimal numbers):
Java version:
inputValues[0]: 0
inputValues[1]: 12
inputValues[2]: 33
inputValues[3]: -33
JavaScript version:
inputNumberArray[0]: 0
inputNumberArray[1]: 12
inputNumberArray[2]: 33
inputNumberArray[3]: -33
, . WebKit JavaScriptCore.