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