SmartCommunity/videoSurveillance/node_modules/hat/index.js

var hat = module.exports = function (bits, base) {
    if (!base) base = 16;
    if (bits === undefined) bits = 128;
    if (bits <= 0) return '0';
    
    var digits = Math.log(Math.pow(2, bits)) / Math.log(base);
    for (var i = 2; digits === Infinity; i *= 2) {
        digits = Math.log(Math.pow(2, bits / i)) / Math.log(base) * i;
    }
    
    var rem = digits - Math.floor(digits);
    
    var res = '';
    
    for (var i = 0; i < Math.floor(digits); i++) {
        var x = Math.floor(Math.random() * base).toString(base);
        res = x + res;
    }
    
    if (rem) {
        var b = Math.pow(base, rem);
        var x = Math.floor(Math.random() * b).toString(base);
        res = x + res;
    }
    
    var parsed = parseInt(res, base);
    if (parsed !== Infinity && parsed >= Math.pow(2, bits)) {
        return hat(bits, base)
    }
    else return res;
};

hat.rack = function (bits, base, expandBy) {
    var fn = function (data) {
        var iters = 0;
        do {
            if (iters ++ > 10) {
                if (expandBy) bits += expandBy;
                else throw new Error('too many ID collisions, use more bits')
            }
            
            var id = hat(bits, base);
        } while (Object.hasOwnProperty.call(hats, id));
        
        hats[id] = data;
        return id;
    };
    var hats = fn.hats = {};
    
    fn.get = function (id) {
        return fn.hats[id];
    };
    
    fn.set = function (id, value) {
        fn.hats[id] = value;
        return fn;
    };
    
    fn.bits = bits || 128;
    fn.base = base || 16;
    return fn;
};