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JavaScript

/**
* @preserve
* JS Implementation of incremental MurmurHash3 (r150) (as of May 10, 2013)
*
* @author <a href="mailto:jensyt@gmail.com">Jens Taylor</a>
* @see http://github.com/homebrewing/brauhaus-diff
* @author <a href="mailto:gary.court@gmail.com">Gary Court</a>
* @see http://github.com/garycourt/murmurhash-js
* @author <a href="mailto:aappleby@gmail.com">Austin Appleby</a>
* @see http://sites.google.com/site/murmurhash/
*/
(function(){
var cache;
// Call this function without `new` to use the cached object (good for
// single-threaded environments), or with `new` to create a new object.
//
// @param {string} key A UTF-16 or ASCII string
// @param {number} seed An optional positive integer
// @return {object} A MurmurHash3 object for incremental hashing
function MurmurHash3(key, seed) {
var m = this instanceof MurmurHash3 ? this : cache;
m.reset(seed)
if (typeof key === 'string' && key.length > 0) {
m.hash(key);
}
if (m !== this) {
return m;
}
};
// Incrementally add a string to this hash
//
// @param {string} key A UTF-16 or ASCII string
// @return {object} this
MurmurHash3.prototype.hash = function(key) {
var h1, k1, i, top, len;
len = key.length;
this.len += len;
k1 = this.k1;
i = 0;
switch (this.rem) {
case 0: k1 ^= len > i ? (key.charCodeAt(i++) & 0xffff) : 0;
case 1: k1 ^= len > i ? (key.charCodeAt(i++) & 0xffff) << 8 : 0;
case 2: k1 ^= len > i ? (key.charCodeAt(i++) & 0xffff) << 16 : 0;
case 3:
k1 ^= len > i ? (key.charCodeAt(i) & 0xff) << 24 : 0;
k1 ^= len > i ? (key.charCodeAt(i++) & 0xff00) >> 8 : 0;
}
this.rem = (len + this.rem) & 3; // & 3 is same as % 4
len -= this.rem;
if (len > 0) {
h1 = this.h1;
while (1) {
k1 = (k1 * 0x2d51 + (k1 & 0xffff) * 0xcc9e0000) & 0xffffffff;
k1 = (k1 << 15) | (k1 >>> 17);
k1 = (k1 * 0x3593 + (k1 & 0xffff) * 0x1b870000) & 0xffffffff;
h1 ^= k1;
h1 = (h1 << 13) | (h1 >>> 19);
h1 = (h1 * 5 + 0xe6546b64) & 0xffffffff;
if (i >= len) {
break;
}
k1 = ((key.charCodeAt(i++) & 0xffff)) ^
((key.charCodeAt(i++) & 0xffff) << 8) ^
((key.charCodeAt(i++) & 0xffff) << 16);
top = key.charCodeAt(i++);
k1 ^= ((top & 0xff) << 24) ^
((top & 0xff00) >> 8);
}
k1 = 0;
switch (this.rem) {
case 3: k1 ^= (key.charCodeAt(i + 2) & 0xffff) << 16;
case 2: k1 ^= (key.charCodeAt(i + 1) & 0xffff) << 8;
case 1: k1 ^= (key.charCodeAt(i) & 0xffff);
}
this.h1 = h1;
}
this.k1 = k1;
return this;
};
// Get the result of this hash
//
// @return {number} The 32-bit hash
MurmurHash3.prototype.result = function() {
var k1, h1;
k1 = this.k1;
h1 = this.h1;
if (k1 > 0) {
k1 = (k1 * 0x2d51 + (k1 & 0xffff) * 0xcc9e0000) & 0xffffffff;
k1 = (k1 << 15) | (k1 >>> 17);
k1 = (k1 * 0x3593 + (k1 & 0xffff) * 0x1b870000) & 0xffffffff;
h1 ^= k1;
}
h1 ^= this.len;
h1 ^= h1 >>> 16;
h1 = (h1 * 0xca6b + (h1 & 0xffff) * 0x85eb0000) & 0xffffffff;
h1 ^= h1 >>> 13;
h1 = (h1 * 0xae35 + (h1 & 0xffff) * 0xc2b20000) & 0xffffffff;
h1 ^= h1 >>> 16;
return h1 >>> 0;
};
// Reset the hash object for reuse
//
// @param {number} seed An optional positive integer
MurmurHash3.prototype.reset = function(seed) {
this.h1 = typeof seed === 'number' ? seed : 0;
this.rem = this.k1 = this.len = 0;
return this;
};
// A cached object to use. This can be safely used if you're in a single-
// threaded environment, otherwise you need to create new hashes to use.
cache = new MurmurHash3();
if (typeof(module) != 'undefined') {
module.exports = MurmurHash3;
} else {
this.MurmurHash3 = MurmurHash3;
}
}());