/**
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* Module dependencies
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*/
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var crypto = require('crypto');
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/**
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* 62 characters in the ascii range that can be used in URLs without special
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* encoding.
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*/
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var UIDCHARS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
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/**
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* Make a Buffer into a string ready for use in URLs
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*
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* @param {String} bytes a Buffer containing the bytes to convert
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* @returns {String} UID
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* @api private
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*/
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function tostr(bytes) {
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var r, i;
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r = [];
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for (i = 0; i < bytes.length; i++) {
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r.push(UIDCHARS[bytes[i] % UIDCHARS.length]);
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}
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return r.join('');
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}
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/**
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* Generate an Unique Id
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*
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* @param {Number} length The number of chars of the uid
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* @param {Number} cb (optional) Callback for async uid generation
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* @api public
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*/
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function uid(length, cb) {
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if (typeof cb === 'undefined') {
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return tostr(crypto.pseudoRandomBytes(length));
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} else {
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crypto.pseudoRandomBytes(length, function(err, bytes) {
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if (err) return cb(err);
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cb(null, tostr(bytes));
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})
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}
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}
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/**
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* Exports
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*/
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module.exports = uid;
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