willcore.ui/client/helpers/guid.js

Simple, Fast And Powerful Client-Side HTML UI Framework.

let getRandomBytes = function(n) {
    let a = new Uint8Array(n);
    for (let i = 0; i < n; i += 65536) {
        crypto.getRandomValues(a.subarray(i, i + Math.min(n - i, 65536)));
    }
    return a;
}

var byteToHex = [];
for (let i = 0; i < 256; ++i) {
    byteToHex[i] = (i + 0x100).toString(16).substr(1);
}

function bytesToUuid(buf, offset) {
    let i = offset || 0;
    let bth = byteToHex;
    return ([bth[buf[i++]], bth[buf[i++]],
    bth[buf[i++]], bth[buf[i++]], '-',
    bth[buf[i++]], bth[buf[i++]], '-',
    bth[buf[i++]], bth[buf[i++]], '-',
    bth[buf[i++]], bth[buf[i++]], '-',
    bth[buf[i++]], bth[buf[i++]],
    bth[buf[i++]], bth[buf[i++]],
    bth[buf[i++]], bth[buf[i++]]]).join('');
}

let _nodeId;
let _clockseq;

let _lastMSecs = 0;
let _lastNSecs = 0;
//  A modified version of a GUID generator from orgiginal API
//  Copyright (c) 2010-2016 Robert Kieffer and other contributors
//	https://github.com/broofa/node-uuid 

function guid(options, buf, offset) {
    let i = buf && offset || 0;
    let b = buf || [];

    options = options || {};
    let node = options.node || _nodeId;
    let clockseq = options.clockseq !== undefined ? options.clockseq : _clockseq;

    // node and clockseq need to be initialized to random values if they're not
    // specified.  We do this lazily to minimize issues related to insufficient
    // system entropy.  See #189
    if (node == null || clockseq == null) {
        let seedBytes = getRandomBytes();
        if (node == null) {
            // Per 4.5, create and 48-bit node id, (47 random bits + multicast bit = 1)
            node = _nodeId = [
                seedBytes[0] | 0x01,
                seedBytes[1], seedBytes[2], seedBytes[3], seedBytes[4], seedBytes[5]
            ];
        }
        if (clockseq == null) {
            // Per 4.2.2, randomize (14 bit) clockseq
            clockseq = _clockseq = (seedBytes[6] << 8 | seedBytes[7]) & 0x3fff;
        }
    }

    // UUID timestamps are 100 nano-second units since the Gregorian epoch,
    // (1582-10-15 00:00).  JSNumbers aren't precise enough for this, so
    // time is handled internally as 'msecs' (integer milliseconds) and 'nsecs'
    // (100-nanoseconds offset from msecs) since unix epoch, 1970-01-01 00:00.
    let msecs = options.msecs !== undefined ? options.msecs : new Date().getTime();

    // Per 4.2.1.2, use count of uuid's generated during the current clock
    //let cycle to simulate higher resolution clock
    let nsecs = options.nsecs !== undefined ? options.nsecs : _lastNSecs + 1;

    // Time since last uuid creation (in msecs)
    let dt = (msecs - _lastMSecs) + (nsecs - _lastNSecs) / 10000;

    // Per 4.2.1.2, Bump clockseq on clock regression
    if (dt < 0 && options.clockseq === undefined) {
        clockseq = clockseq + 1 & 0x3fff;
    }

    // Reset nsecs if clock regresses (new clockseq) or we've moved onto a new
    // time interval
    if ((dt < 0 || msecs > _lastMSecs) && options.nsecs === undefined) {
        nsecs = 0;
    }

    // Per 4.2.1.2 Throw error if too many uuids are requested
    if (nsecs >= 10000) {
        throw new Error('uuid.v1(): Can\'t create more than 10M uuids/sec');
    }

    _lastMSecs = msecs;
    _lastNSecs = nsecs;
    _clockseq = clockseq;

    // Per 4.1.4 - Convert from unix epoch to Gregorian epoch
    msecs += 12219292800000;

    // `time_low`
    let tl = ((msecs & 0xfffffff) * 10000 + nsecs) % 0x100000000;
    b[i++] = tl >>> 24 & 0xff;
    b[i++] = tl >>> 16 & 0xff;
    b[i++] = tl >>> 8 & 0xff;
    b[i++] = tl & 0xff;

    // `time_mid`
    let tmh = (msecs / 0x100000000 * 10000) & 0xfffffff;
    b[i++] = tmh >>> 8 & 0xff;
    b[i++] = tmh & 0xff;

    // `time_high_and_version`
    b[i++] = tmh >>> 24 & 0xf | 0x10; // include version
    b[i++] = tmh >>> 16 & 0xff;

    // `clock_seq_hi_and_reserved` (Per 4.2.2 - include variant)
    b[i++] = clockseq >>> 8 | 0x80;

    // `clock_seq_low`
    b[i++] = clockseq & 0xff;

    // `node`
    for (let n = 0; n < 6; ++n) {
        b[i + n] = node[n];
    }

    return buf ? buf : bytesToUuid(b);
}

export { guid };