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