Javascript implementation of Jenkins Hash?

Question

Is there a javascript implemenation of the Jenkins Hash I could use - rather than implementing it on my own?

I know there is a python implemenation I could use to write my own js. But I am no Javascript expert and therefor I would prefer someone elses implementation.

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Update: (I did try to convert http://www.burtleburtle.net/bob/c/lookup3.c) Update 2: This code gives you the same hashes as hashlittle2 in lookup3.c

var Jenkins = {
rot: function(x,k) {
    return (x<<k) | (x>>>(32-k));
},

mix: function(a,b,c) {
    a = (a - c) | 0;  a ^= Jenkins.rot(c, 4);  c = (c + b) | 0;
    b = (b - a) | 0;  b ^= Jenkins.rot(a, 6);  a = (a + c) | 0;
    c = (c - b) | 0;  c ^= Jenkins.rot(b, 8);  b = (b + a) | 0;
    a = (a - c) | 0;  a ^= Jenkins.rot(c,16);  c = (c + b) | 0;
    b = (b - a) | 0;  b ^= Jenkins.rot(a,19);  a = (a + c) | 0;
    c = (c - b) | 0;  c ^= Jenkins.rot(b, 4);  b = (b + a) | 0;
    return {a : a, b : b, c : c};
},

final: function(a,b,c) {
   c ^= b; c -= Jenkins.rot(b,14) | 0;
   a ^= c; a -= Jenkins.rot(c,11) | 0;
   b ^= a; b -= Jenkins.rot(a,25) | 0;
   c ^= b; c -= Jenkins.rot(b,16) | 0;
   a ^= c; a -= Jenkins.rot(c,4) | 0;
   b ^= a; b -= Jenkins.rot(a,14) | 0;
   c ^= b; c -= Jenkins.rot(b,24) | 0;
   return {a : a, b : b, c : c};
},  

hashlittle2: function(k, initval, initval2) {
    var length = k.length;
    a = b = c = 0xdeadbeef + length + initval;
    c += initval2;

    offset = 0;
    while (length > 12) {
        a += (k.charCodeAt(offset+0) + (k.charCodeAt(offset+1)<<8) + (k.charCodeAt(offset+2)<<16) + (k.charCodeAt(offset+3)<<24)); a = a>>>0;
        b += (k.charCodeAt(offset+4) + (k.charCodeAt(offset+5)<<8) + (k.charCodeAt(offset+6)<<16) + (k.charCodeAt(offset+7)<<24)); b = b>>>0;
        c += (k.charCodeAt(offset+8) + (k.charCodeAt(offset+9)<<8) + (k.charCodeAt(offset+10)<<16) + (k.charCodeAt(offset+11)<<24)); c = c>>>0;
        o = Jenkins.mix(a,b,c);
        a = o.a; b = o.b; c = o.c;
        length -= 12;
        offset += 12;
    }

    switch(length) {
        case 12: c += (k.charCodeAt(offset+8) + (k.charCodeAt(offset+9)<<8) + (k.charCodeAt(offset+10)<<16) + (k.charCodeAt(offset+11)<<24)); b += (k.charCodeAt(offset+4) + (k.charCodeAt(offset+5)<<8) + (k.charCodeAt(offset+6)<<16) + (k.charCodeAt(offset+7)<<24)); a += (k.charCodeAt(offset+0) + (k.charCodeAt(offset+1)<<8) + (k.charCodeAt(offset+2)<<16) + (k.charCodeAt(offset+3)<<24)); break;
        case 11: c += (k.charCodeAt(offset+8) + (k.charCodeAt(offset+9)<<8) + (k.charCodeAt(offset+10)<<16)); b += (k.charCodeAt(offset+4) + (k.charCodeAt(offset+5)<<8) + (k.charCodeAt(offset+6)<<16) + (k.charCodeAt(offset+7)<<24)); a += (k.charCodeAt(offset+0) + (k.charCodeAt(offset+1)<<8) + (k.charCodeAt(offset+2)<<16) + (k.charCodeAt(offset+3)<<24)); break;
        case 10: c += (k.charCodeAt(offset+8) + (k.charCodeAt(offset+9)<<8)); b += (k.charCodeAt(offset+4) + (k.charCodeAt(offset+5)<<8) + (k.charCodeAt(offset+6)<<16) + (k.charCodeAt(offset+7)<<24)); a += (k.charCodeAt(offset+0) + (k.charCodeAt(offset+1)<<8) + (k.charCodeAt(offset+2)<<16) + (k.charCodeAt(offset+3)<<24)); break;
        case 9: c += (k.charCodeAt(offset+8)); b += (k.charCodeAt(offset+4) + (k.charCodeAt(offset+5)<<8) + (k.charCodeAt(offset+6)<<16) + (k.charCodeAt(offset+7)<<24)); a += (k.charCodeAt(offset+0) + (k.charCodeAt(offset+1)<<8) + (k.charCodeAt(offset+2)<<16) + (k.charCodeAt(offset+3)<<24)); break;
        case 8: b += (k.charCodeAt(offset+4) + (k.charCodeAt(offset+5)<<8) + (k.charCodeAt(offset+6)<<16) + (k.charCodeAt(offset+7)<<24)); a += (k.charCodeAt(offset+0) + (k.charCodeAt(offset+1)<<8) + (k.charCodeAt(offset+2)<<16) + (k.charCodeAt(offset+3)<<24)); break;
        case 7: b += (k.charCodeAt(offset+4) + (k.charCodeAt(offset+5)<<8) + (k.charCodeAt(offset+6)<<16)); a += (k.charCodeAt(offset+0) + (k.charCodeAt(offset+1)<<8) + (k.charCodeAt(offset+2)<<16) + (k.charCodeAt(offset+3)<<24)); break;
        case 6: b += ((k.charCodeAt(offset+5)<<8) + k.charCodeAt(offset+4)); a += (k.charCodeAt(offset+0) + (k.charCodeAt(offset+1)<<8) + (k.charCodeAt(offset+2)<<16) + (k.charCodeAt(offset+3)<<24)); break;
        case 5: b += (k.charCodeAt(offset+4)); a += (k.charCodeAt(offset+0) + (k.charCodeAt(offset+1)<<8) + (k.charCodeAt(offset+2)<<16) + (k.charCodeAt(offset+3)<<24)); break;
        case 4: a += (k.charCodeAt(offset+0) + (k.charCodeAt(offset+1)<<8) + (k.charCodeAt(offset+2)<<16) + (k.charCodeAt(offset+3)<<24)); break;
        case 3: a += (k.charCodeAt(offset+0) + (k.charCodeAt(offset+1)<<8) + (k.charCodeAt(offset+2)<<16)); break;
        case 2: a += (k.charCodeAt(offset+0) + (k.charCodeAt(offset+1)<<8)); break;
        case 1: a += (k.charCodeAt(offset+0)); break;
        case 0: return {b : b, c : c};
    }

    o = Jenkins.final(a,b,c);
    a = o.a; b = o.b; c = o.c;

    return {b : b>>>0, c : c>>>0};
}    

}

Answer 1

Here's a JavaScript port I did of lookup3.c for a personal project to implement a Bloom filter in JavaScript. I can't say for sure whether it produces identical results to the C code though.

One of the main things that does not translate directly into JavaScript is the pointer arithmetic performed on the pointer to the key input. Look for the word offset in the code below to see how I handled that.

If you want an output as if the integer is unsigned, you can use returnValue >>> 0.

var BloomFilter = {
    // Convert a JavaScript string into an array of 32-bit words.
    // This preserves the UTF-16 encoding, padding with the null character if necessary.
    stringToWords: function(s) {
        var b = [];
        if(s.length & 1) {
            s += "\u0000";
        }
        for (var i = 0; i < s.length; i += 2) {
            b.push((s.charCodeAt(i) << 16) | (s.charCodeAt(i + 1)));
        }
        return b;
    },

    // Hash an array of multiple 32-bit words to a single word.
    // Adapted from "lookup3.c, by Bob Jenkins, May 2006, Public Domain."
    // as retrieved 2010-07-03 from http://burtleburtle.net/bob/c/lookup3.c

    hashWord: function(k, initval) {
        // definition of bitwise rotate function
        function rot(x, k) {
            return (x << k) | (x >>> (32 - k));
        }

        // initialization
        var a, b, c, length = k.length, offset = 0;
        a = b = c = (0xdeadbeef + (length << 2) + initval) | 0;

        // handle most of the key
        while(length > 3) {
            a = (a + k[offset]) | 0;
            b = (b + k[offset + 1]) | 0;
            c = (c + k[offset + 2]) | 0;

            // mixing function
            a = (a - c) | 0;  a ^= rot(c, 4);  c = (c + b) | 0;
            b = (b - a) | 0;  b ^= rot(a, 6);  a = (a + c) | 0;
            c = (c - b) | 0;  c ^= rot(b, 8);  b = (b + a) | 0;
            a = (a - c) | 0;  a ^= rot(c,16);  c = (c + b) | 0;
            b = (b - a) | 0;  b ^= rot(a,19);  a = (a + c) | 0;
            c = (c - b) | 0;  c ^= rot(b, 4);  b = (b + a) | 0;

            length -= 3;
            offset += 3;
        }

        // handle the final words if left over; fall-through is intended
        switch(length) {
            case 3: c = (c + k[offset + 2]) | 0;
            case 2: b = (b + k[offset + 1]) | 0;
            case 1: a = (a + k[offset]) | 0;

            // final mixing
            c ^= b; c = (c - rot(b,14)) | 0;
            a ^= c; a = (a - rot(c,11)) | 0;
            b ^= a; b = (b - rot(a,25)) | 0;
            c ^= b; c = (c - rot(b,16)) | 0;
            a ^= c; a = (a - rot(c, 4)) | 0;
            b ^= a; b = (b - rot(a,14)) | 0;
            c ^= b; c = (c - rot(b,24)) | 0;

            case 0: break; // nothing left to do
        }

        // return the result
        return c;
    },

    // Hash a string by converting to UTF-16 before using the lookup3 algorithm.
    hashString: function(s) {
        return BloomFilter.hashWord(BloomFilter.stringToWords(s), 0);
    }
}