146 lines
No EOL
4.6 KiB
JavaScript
146 lines
No EOL
4.6 KiB
JavaScript
import rng from './rng.js';
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import { unsafeStringify } from './stringify.js';
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/**
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* UUID V7 - Unix Epoch time-based UUID
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*
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* The IETF has published RFC9562, introducing 3 new UUID versions (6,7,8). This
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* implementation of V7 is based on the accepted, though not yet approved,
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* revisions.
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*
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* RFC 9562:https://www.rfc-editor.org/rfc/rfc9562.html Universally Unique
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* IDentifiers (UUIDs)
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*
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* Sample V7 value:
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* https://www.rfc-editor.org/rfc/rfc9562.html#name-example-of-a-uuidv7-value
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*
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* Monotonic Bit Layout: RFC rfc9562.6.2 Method 1, Dedicated Counter Bits ref:
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* https://www.rfc-editor.org/rfc/rfc9562.html#section-6.2-5.1
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*
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* 0 1 2 3 0 1 2 3 4 5 6
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* 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | unix_ts_ms |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | unix_ts_ms | ver | seq_hi |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* |var| seq_low | rand |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | rand |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*
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* seq is a 31 bit serialized counter; comprised of 12 bit seq_hi and 19 bit
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* seq_low, and randomly initialized upon timestamp change. 31 bit counter size
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* was selected as any bitwise operations in node are done as _signed_ 32 bit
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* ints. we exclude the sign bit.
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*/
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var _seqLow = null;
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var _seqHigh = null;
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var _msecs = 0;
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function v7(options, buf, offset) {
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options = options || {};
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// initialize buffer and pointer
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var i = buf && offset || 0;
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var b = buf || new Uint8Array(16);
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// rnds is Uint8Array(16) filled with random bytes
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var rnds = options.random || (options.rng || rng)();
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// milliseconds since unix epoch, 1970-01-01 00:00
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var msecs = options.msecs !== undefined ? options.msecs : Date.now();
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// seq is user provided 31 bit counter
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var seq = options.seq !== undefined ? options.seq : null;
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// initialize local seq high/low parts
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var seqHigh = _seqHigh;
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var seqLow = _seqLow;
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// check if clock has advanced and user has not provided msecs
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if (msecs > _msecs && options.msecs === undefined) {
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_msecs = msecs;
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// unless user provided seq, reset seq parts
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if (seq !== null) {
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seqHigh = null;
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seqLow = null;
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}
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}
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// if we have a user provided seq
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if (seq !== null) {
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// trim provided seq to 31 bits of value, avoiding overflow
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if (seq > 0x7fffffff) {
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seq = 0x7fffffff;
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}
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// split provided seq into high/low parts
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seqHigh = seq >>> 19 & 0xfff;
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seqLow = seq & 0x7ffff;
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}
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// randomly initialize seq
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if (seqHigh === null || seqLow === null) {
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seqHigh = rnds[6] & 0x7f;
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seqHigh = seqHigh << 8 | rnds[7];
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seqLow = rnds[8] & 0x3f; // pad for var
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seqLow = seqLow << 8 | rnds[9];
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seqLow = seqLow << 5 | rnds[10] >>> 3;
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}
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// increment seq if within msecs window
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if (msecs + 10000 > _msecs && seq === null) {
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if (++seqLow > 0x7ffff) {
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seqLow = 0;
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if (++seqHigh > 0xfff) {
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seqHigh = 0;
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// increment internal _msecs. this allows us to continue incrementing
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// while staying monotonic. Note, once we hit 10k milliseconds beyond system
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// clock, we will reset breaking monotonicity (after (2^31)*10000 generations)
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_msecs++;
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}
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}
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} else {
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// resetting; we have advanced more than
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// 10k milliseconds beyond system clock
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_msecs = msecs;
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}
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_seqHigh = seqHigh;
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_seqLow = seqLow;
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// [bytes 0-5] 48 bits of local timestamp
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b[i++] = _msecs / 0x10000000000 & 0xff;
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b[i++] = _msecs / 0x100000000 & 0xff;
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b[i++] = _msecs / 0x1000000 & 0xff;
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b[i++] = _msecs / 0x10000 & 0xff;
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b[i++] = _msecs / 0x100 & 0xff;
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b[i++] = _msecs & 0xff;
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// [byte 6] - set 4 bits of version (7) with first 4 bits seq_hi
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b[i++] = seqHigh >>> 4 & 0x0f | 0x70;
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// [byte 7] remaining 8 bits of seq_hi
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b[i++] = seqHigh & 0xff;
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// [byte 8] - variant (2 bits), first 6 bits seq_low
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b[i++] = seqLow >>> 13 & 0x3f | 0x80;
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// [byte 9] 8 bits seq_low
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b[i++] = seqLow >>> 5 & 0xff;
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// [byte 10] remaining 5 bits seq_low, 3 bits random
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b[i++] = seqLow << 3 & 0xff | rnds[10] & 0x07;
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// [bytes 11-15] always random
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b[i++] = rnds[11];
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b[i++] = rnds[12];
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b[i++] = rnds[13];
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b[i++] = rnds[14];
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b[i++] = rnds[15];
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return buf || unsafeStringify(b);
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}
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export default v7; |