69 lines
1.3 KiB
JavaScript
69 lines
1.3 KiB
JavaScript
'use strict';
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var alphabet = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-_'.split('')
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, length = 64
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, map = {}
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, seed = 0
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, i = 0
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, prev;
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/**
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* Return a string representing the specified number.
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*
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* @param {Number} num The number to convert.
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* @returns {String} The string representation of the number.
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* @api public
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*/
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function encode(num) {
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var encoded = '';
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do {
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encoded = alphabet[num % length] + encoded;
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num = Math.floor(num / length);
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} while (num > 0);
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return encoded;
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}
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/**
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* Return the integer value specified by the given string.
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*
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* @param {String} str The string to convert.
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* @returns {Number} The integer value represented by the string.
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* @api public
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*/
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function decode(str) {
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var decoded = 0;
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for (i = 0; i < str.length; i++) {
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decoded = decoded * length + map[str.charAt(i)];
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}
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return decoded;
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}
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/**
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* Yeast: A tiny growing id generator.
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*
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* @returns {String} A unique id.
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* @api public
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*/
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function yeast() {
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var now = encode(+new Date());
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if (now !== prev) return seed = 0, prev = now;
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return now +'.'+ encode(seed++);
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}
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//
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// Map each character to its index.
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//
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for (; i < length; i++) map[alphabet[i]] = i;
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//
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// Expose the `yeast`, `encode` and `decode` functions.
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//
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yeast.encode = encode;
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yeast.decode = decode;
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module.exports = yeast;
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