sortable-hash

Hash arrays of numbers into sortable strings with variable precision loss

npm install sortable-hash
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Hash arrays of numbers into a string from which you can reconstruct the original values, with configurable precision loss. The generated hashes sort well, so similar input values cause large shared prefixes in hashes.

encode([10, 10, 10]) == 'w07w1z0gs3y0';
encode([10, 11, 10]) == 'w07x1e1cs2yk';

Usage

Hash the array [10, -10, 10] and then restore it, using differend hash sizes.

var sortable = require('sortable-hash');

var hash = sortable.encode([10, -10, 10]);
// => 'p4pp5e9cbbuk'

sortable.decode(hash, 3);
// => [ 9.999942779541016,
//      -9.999942779541016,
//      9.999942779541016 ]

var biggerHash = sortable.encode([10, -10, 10], 35);
// => 'p4pp5e9cbbukqnpp5e9cbbukqnpp5e9cb3h'

sortable.decode(biggerHash, 3);
// => [ 10, -10, 10 ]

API

sortable.encode(values[, options])

Hash the array values, which may only contain Numbers in the range of [-100, 100].

options can either be an object with those possible keys:

  • precision: Length of the resulting hash

or a Number, in which case it sets options.precision.

encode([10], 13) === encode([10], { precision: 13 });

sortable.decode(string, numValues)

Decode string into an Array of Numbers. numValues needs to be the number of elements initially passed to hash.encode.

Installation

With npm do:

$ npm install sortable-hash

Kudos

This is the idea of geohashes generalized for use with all numeric data and numbers of input fields.

License

Copyright (c) 2013 Julian Gruber <julian@juliangruber.com>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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