110 lines
3.3 KiB
JavaScript
110 lines
3.3 KiB
JavaScript
var rng = require('./lib/rng');
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var bytesToUuid = require('./lib/bytesToUuid');
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// **`v1()` - Generate time-based UUID**
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//
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// Inspired by https://github.com/LiosK/UUID.js
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// and http://docs.python.org/library/uuid.html
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var _nodeId;
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var _clockseq;
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// Previous uuid creation time
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var _lastMSecs = 0;
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var _lastNSecs = 0;
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// See https://github.com/uuidjs/uuid for API details
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function v1(options, buf, offset) {
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var i = buf && offset || 0;
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var b = buf || [];
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options = options || {};
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var node = options.node || _nodeId;
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var clockseq = options.clockseq !== undefined ? options.clockseq : _clockseq;
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// node and clockseq need to be initialized to random values if they're not
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// specified. We do this lazily to minimize issues related to insufficient
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// system entropy. See #189
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if (node == null || clockseq == null) {
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var seedBytes = rng();
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if (node == null) {
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// Per 4.5, create and 48-bit node id, (47 random bits + multicast bit = 1)
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node = _nodeId = [
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seedBytes[0] | 0x01,
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seedBytes[1], seedBytes[2], seedBytes[3], seedBytes[4], seedBytes[5]
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];
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}
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if (clockseq == null) {
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// Per 4.2.2, randomize (14 bit) clockseq
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clockseq = _clockseq = (seedBytes[6] << 8 | seedBytes[7]) & 0x3fff;
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}
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}
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// UUID timestamps are 100 nano-second units since the Gregorian epoch,
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// (1582-10-15 00:00). JSNumbers aren't precise enough for this, so
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// time is handled internally as 'msecs' (integer milliseconds) and 'nsecs'
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// (100-nanoseconds offset from msecs) since unix epoch, 1970-01-01 00:00.
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var msecs = options.msecs !== undefined ? options.msecs : new Date().getTime();
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// Per 4.2.1.2, use count of uuid's generated during the current clock
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// cycle to simulate higher resolution clock
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var nsecs = options.nsecs !== undefined ? options.nsecs : _lastNSecs + 1;
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// Time since last uuid creation (in msecs)
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var dt = (msecs - _lastMSecs) + (nsecs - _lastNSecs)/10000;
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// Per 4.2.1.2, Bump clockseq on clock regression
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if (dt < 0 && options.clockseq === undefined) {
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clockseq = clockseq + 1 & 0x3fff;
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}
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// Reset nsecs if clock regresses (new clockseq) or we've moved onto a new
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// time interval
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if ((dt < 0 || msecs > _lastMSecs) && options.nsecs === undefined) {
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nsecs = 0;
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}
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// Per 4.2.1.2 Throw error if too many uuids are requested
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if (nsecs >= 10000) {
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throw new Error('uuid.v1(): Can\'t create more than 10M uuids/sec');
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}
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_lastMSecs = msecs;
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_lastNSecs = nsecs;
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_clockseq = clockseq;
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// Per 4.1.4 - Convert from unix epoch to Gregorian epoch
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msecs += 12219292800000;
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// `time_low`
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var tl = ((msecs & 0xfffffff) * 10000 + nsecs) % 0x100000000;
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b[i++] = tl >>> 24 & 0xff;
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b[i++] = tl >>> 16 & 0xff;
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b[i++] = tl >>> 8 & 0xff;
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b[i++] = tl & 0xff;
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// `time_mid`
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var tmh = (msecs / 0x100000000 * 10000) & 0xfffffff;
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b[i++] = tmh >>> 8 & 0xff;
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b[i++] = tmh & 0xff;
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// `time_high_and_version`
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b[i++] = tmh >>> 24 & 0xf | 0x10; // include version
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b[i++] = tmh >>> 16 & 0xff;
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// `clock_seq_hi_and_reserved` (Per 4.2.2 - include variant)
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b[i++] = clockseq >>> 8 | 0x80;
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// `clock_seq_low`
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b[i++] = clockseq & 0xff;
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// `node`
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for (var n = 0; n < 6; ++n) {
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b[i + n] = node[n];
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}
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return buf ? buf : bytesToUuid(b);
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}
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module.exports = v1;
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