An incremental implementation of MurmurHash3
This version works significantly faster than the non-incremental version if you need to hash many small strings into a single hash, since string concatenation (to build the single string to pass the non-incremental version) is fairly costly. In one case tested, using the incremental version was about 50% faster than concatenating 5-10 strings and then hashing.
To use iMurmurHash in the browser, download the latest version and include it as a script on your site.
To use iMurmurHash in Node.js, install the module using NPM:
npm install imurmurhash
Then simply include it in your scripts:
MurmurHash3 = require'imurmurhash';
// Create the initial hashvar hashState = MurmurHash3'string';// Incrementally add texthashStatehash'more strings';hashStatehash'even more strings';// All calls can be chained if desiredhashStatehash'and'hash'some'hash'more';// Get a resulthashStateresult;// returns 0xe4ccfe6b
Get a hash state object, optionally initialized with the given string and seed. Seed must be a positive integer if provided. Calling this function without the
new keyword will return a cached state object that has been reset. This is safe to use as long as the object is only used from a single thread and no other hashes are created while operating on this one. If this constraint cannot be met, you can use
new to create a new state object. For example:
// Use the cached object, calling the function again will return the same// object (but reset, so the current state would be lost)hashState = MurmurHash3;// Create a new object that can be safely used however you wish. Calling the// function again will simply return a new state object, and no state loss// will occur, at the cost of creating more objects.hashState = ;
Both methods can be mixed however you like if you have different use cases.
Incrementally add string to the hash. This can be called as many times as you want for the hash state object, including after a call to
this so calls can be chained.
Get the result of the hash as a 32-bit positive integer. This performs the tail and finalizer portions of the algorithm, but does not store the result in the state object. This means that it is perfectly safe to get results and then continue adding strings via
// Do the whole string at onceMurmurHash3'this is a test string'result;// 0x70529328// Do part of the string, get a result, then the other partvar m = MurmurHash3'this is a';mresult;// 0xbfc4f834mhash' test string'result;// 0x70529328 (same as above)
Reset the state object for reuse, optionally using the given seed (defaults to 0 like the constructor). Returns
this so calls can be chained.
Copyright (c) 2013 Gary Court, Jens Taylor
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