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README.md 4.7KB

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  1. iMurmurHash.js
  2. ==============
  3. An incremental implementation of the MurmurHash3 (32-bit) hashing algorithm for JavaScript based on [Gary Court's implementation](https://github.com/garycourt/murmurhash-js) with [kazuyukitanimura's modifications](https://github.com/kazuyukitanimura/murmurhash-js).
  4. 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.
  5. Installation
  6. ------------
  7. To use iMurmurHash in the browser, [download the latest version](https://raw.github.com/jensyt/imurmurhash-js/master/imurmurhash.min.js) and include it as a script on your site.
  8. ```html
  9. <script type="text/javascript" src="/scripts/imurmurhash.min.js"></script>
  10. <script>
  11. // Your code here, access iMurmurHash using the global object MurmurHash3
  12. </script>
  13. ```
  14. ---
  15. To use iMurmurHash in Node.js, install the module using NPM:
  16. ```bash
  17. npm install imurmurhash
  18. ```
  19. Then simply include it in your scripts:
  20. ```javascript
  21. MurmurHash3 = require('imurmurhash');
  22. ```
  23. Quick Example
  24. -------------
  25. ```javascript
  26. // Create the initial hash
  27. var hashState = MurmurHash3('string');
  28. // Incrementally add text
  29. hashState.hash('more strings');
  30. hashState.hash('even more strings');
  31. // All calls can be chained if desired
  32. hashState.hash('and').hash('some').hash('more');
  33. // Get a result
  34. hashState.result();
  35. // returns 0xe4ccfe6b
  36. ```
  37. Functions
  38. ---------
  39. ### MurmurHash3 ([string], [seed])
  40. 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:
  41. ```javascript
  42. // Use the cached object, calling the function again will return the same
  43. // object (but reset, so the current state would be lost)
  44. hashState = MurmurHash3();
  45. ...
  46. // Create a new object that can be safely used however you wish. Calling the
  47. // function again will simply return a new state object, and no state loss
  48. // will occur, at the cost of creating more objects.
  49. hashState = new MurmurHash3();
  50. ```
  51. Both methods can be mixed however you like if you have different use cases.
  52. ---
  53. ### MurmurHash3.prototype.hash (string)
  54. 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 `result()`. Returns `this` so calls can be chained.
  55. ---
  56. ### MurmurHash3.prototype.result ()
  57. 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 `hash`.
  58. ```javascript
  59. // Do the whole string at once
  60. MurmurHash3('this is a test string').result();
  61. // 0x70529328
  62. // Do part of the string, get a result, then the other part
  63. var m = MurmurHash3('this is a');
  64. m.result();
  65. // 0xbfc4f834
  66. m.hash(' test string').result();
  67. // 0x70529328 (same as above)
  68. ```
  69. ---
  70. ### MurmurHash3.prototype.reset ([seed])
  71. Reset the state object for reuse, optionally using the given _seed_ (defaults to 0 like the constructor). Returns `this` so calls can be chained.
  72. ---
  73. License (MIT)
  74. -------------
  75. Copyright (c) 2013 Gary Court, Jens Taylor
  76. Permission is hereby granted, free of charge, to any person obtaining a copy of
  77. this software and associated documentation files (the "Software"), to deal in
  78. the Software without restriction, including without limitation the rights to
  79. use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
  80. the Software, and to permit persons to whom the Software is furnished to do so,
  81. subject to the following conditions:
  82. The above copyright notice and this permission notice shall be included in all
  83. copies or substantial portions of the Software.
  84. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  85. IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
  86. FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
  87. COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
  88. IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  89. CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.