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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/uuid-1.3.3/src/timestamp.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>timestamp.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="icon" href="https://www.rust-lang.org/favicon.ico"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../uuid/index.html"><div class="logo-container">
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</pre><pre class="rust"><code><span class="doccomment">//! Generating UUIDs from timestamps.
//!
//! Timestamps are used in a few UUID versions as a source of decentralized
//! uniqueness (as in versions 1 and 6), and as a way to enable sorting (as
//! in versions 6 and 7). Timestamps aren&#39;t encoded the same way by all UUID
//! versions so this module provides a single [`Timestamp`] type that can
//! convert between them.
//!
//! # Timestamp representations in UUIDs
//!
//! Versions 1 and 6 UUIDs use a bespoke timestamp that consists of the
//! number of 100ns ticks since `1582-10-15 00:00:00`, along with
//! a counter value to avoid duplicates.
//!
//! Version 7 UUIDs use a more standard timestamp that consists of the
//! number of millisecond ticks since the Unix epoch (`1970-01-01 00:00:00`).
//!
//! # References
//!
//! * [Timestamp in RFC4122](https://www.rfc-editor.org/rfc/rfc4122#section-4.1.4)
//! * [Timestamp in Draft RFC: New UUID Formats, Version 4](https://datatracker.ietf.org/doc/html/draft-peabody-dispatch-new-uuid-format-04#section-6.1)
</span><span class="kw">use </span><span class="kw">crate</span>::Uuid;
<span class="doccomment">/// The number of 100 nanosecond ticks between the RFC4122 epoch
/// (`1582-10-15 00:00:00`) and the Unix epoch (`1970-01-01 00:00:00`).
</span><span class="kw">pub const </span>UUID_TICKS_BETWEEN_EPOCHS: u64 = <span class="number">0x01B2_1DD2_1381_4000</span>;
<span class="doccomment">/// A timestamp that can be encoded into a UUID.
///
/// This type abstracts the specific encoding, so versions 1, 6, and 7
/// UUIDs can both be supported through the same type, even
/// though they have a different representation of a timestamp.
///
/// # References
///
/// * [Timestamp in RFC4122](https://www.rfc-editor.org/rfc/rfc4122#section-4.1.4)
/// * [Timestamp in Draft RFC: New UUID Formats, Version 4](https://datatracker.ietf.org/doc/html/draft-peabody-dispatch-new-uuid-format-04#section-6.1)
/// * [Clock Sequence in RFC4122](https://datatracker.ietf.org/doc/html/rfc4122#section-4.1.5)
</span><span class="attribute">#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
</span><span class="kw">pub struct </span>Timestamp {
<span class="kw">pub</span>(<span class="kw">crate</span>) seconds: u64,
<span class="kw">pub</span>(<span class="kw">crate</span>) nanos: u32,
<span class="attribute">#[cfg(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>))]
</span><span class="kw">pub</span>(<span class="kw">crate</span>) counter: u16,
}
<span class="kw">impl </span>Timestamp {
<span class="doccomment">/// Get a timestamp representing the current system time.
///
/// This method defers to the standard library&#39;s `SystemTime` type.
///
/// # Panics
///
/// This method will panic if calculating the elapsed time since the Unix epoch fails.
</span><span class="attribute">#[cfg(feature = <span class="string">&quot;std&quot;</span>)]
</span><span class="kw">pub fn </span>now(context: <span class="kw">impl </span>ClockSequence&lt;Output = u16&gt;) -&gt; <span class="self">Self </span>{
<span class="attribute">#[cfg(not(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>)))]
</span>{
<span class="kw">let _ </span>= context;
}
<span class="kw">let </span>(seconds, nanos) = now();
Timestamp {
seconds,
nanos,
<span class="attribute">#[cfg(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>))]
</span>counter: context.generate_sequence(seconds, nanos),
}
}
<span class="doccomment">/// Construct a `Timestamp` from an RFC4122 timestamp and counter, as used
/// in versions 1 and 6 UUIDs.
</span><span class="kw">pub const fn </span>from_rfc4122(ticks: u64, counter: u16) -&gt; <span class="self">Self </span>{
<span class="attribute">#[cfg(not(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>)))]
</span>{
<span class="kw">let _ </span>= counter;
}
<span class="kw">let </span>(seconds, nanos) = <span class="self">Self</span>::rfc4122_to_unix(ticks);
Timestamp {
seconds,
nanos,
<span class="attribute">#[cfg(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>))]
</span>counter,
}
}
<span class="doccomment">/// Construct a `Timestamp` from a Unix timestamp, as used in version 7 UUIDs.
</span><span class="kw">pub fn </span>from_unix(context: <span class="kw">impl </span>ClockSequence&lt;Output = u16&gt;, seconds: u64, nanos: u32) -&gt; <span class="self">Self </span>{
<span class="attribute">#[cfg(not(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>)))]
</span>{
<span class="kw">let _ </span>= context;
Timestamp { seconds, nanos }
}
<span class="attribute">#[cfg(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>))]
</span>{
<span class="kw">let </span>counter = context.generate_sequence(seconds, nanos);
Timestamp {
seconds,
nanos,
counter,
}
}
}
<span class="doccomment">/// Get the value of the timestamp as an RFC4122 timestamp and counter,
/// as used in versions 1 and 6 UUIDs.
</span><span class="attribute">#[cfg(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>))]
</span><span class="kw">pub const fn </span>to_rfc4122(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; (u64, u16) {
(
<span class="self">Self</span>::unix_to_rfc4122_ticks(<span class="self">self</span>.seconds, <span class="self">self</span>.nanos),
<span class="self">self</span>.counter,
)
}
<span class="doccomment">/// Get the value of the timestamp as a Unix timestamp, as used in version 7 UUIDs.
</span><span class="kw">pub const fn </span>to_unix(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; (u64, u32) {
(<span class="self">self</span>.seconds, <span class="self">self</span>.nanos)
}
<span class="attribute">#[cfg(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>))]
</span><span class="kw">const fn </span>unix_to_rfc4122_ticks(seconds: u64, nanos: u32) -&gt; u64 {
<span class="kw">let </span>ticks = UUID_TICKS_BETWEEN_EPOCHS + seconds * <span class="number">10_000_000 </span>+ nanos <span class="kw">as </span>u64 / <span class="number">100</span>;
ticks
}
<span class="kw">const fn </span>rfc4122_to_unix(ticks: u64) -&gt; (u64, u32) {
(
(ticks - UUID_TICKS_BETWEEN_EPOCHS) / <span class="number">10_000_000</span>,
((ticks - UUID_TICKS_BETWEEN_EPOCHS) % <span class="number">10_000_000</span>) <span class="kw">as </span>u32 * <span class="number">100</span>,
)
}
<span class="attribute">#[deprecated(note = <span class="string">&quot;use `to_unix` instead; this method will be removed in a future release&quot;</span>)]
</span><span class="doccomment">/// Get the number of fractional nanoseconds in the Unix timestamp.
///
/// This method is deprecated and probably doesn&#39;t do what you&#39;re expecting it to.
/// It doesn&#39;t return the timestamp as nanoseconds since the Unix epoch, it returns
/// the fractional seconds of the timestamp.
</span><span class="kw">pub const fn </span>to_unix_nanos(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; u32 {
<span class="macro">panic!</span>(<span class="string">&quot;`Timestamp::to_unix_nanos` is deprecated and will be removed: use `Timestamp::to_unix` instead&quot;</span>)
}
}
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>encode_rfc4122_timestamp(ticks: u64, counter: u16, node_id: <span class="kw-2">&amp;</span>[u8; <span class="number">6</span>]) -&gt; Uuid {
<span class="kw">let </span>time_low = (ticks &amp; <span class="number">0xFFFF_FFFF</span>) <span class="kw">as </span>u32;
<span class="kw">let </span>time_mid = ((ticks &gt;&gt; <span class="number">32</span>) &amp; <span class="number">0xFFFF</span>) <span class="kw">as </span>u16;
<span class="kw">let </span>time_high_and_version = (((ticks &gt;&gt; <span class="number">48</span>) &amp; <span class="number">0x0FFF</span>) <span class="kw">as </span>u16) | (<span class="number">1 </span>&lt;&lt; <span class="number">12</span>);
<span class="kw">let </span><span class="kw-2">mut </span>d4 = [<span class="number">0</span>; <span class="number">8</span>];
d4[<span class="number">0</span>] = (((counter &amp; <span class="number">0x3F00</span>) &gt;&gt; <span class="number">8</span>) <span class="kw">as </span>u8) | <span class="number">0x80</span>;
d4[<span class="number">1</span>] = (counter &amp; <span class="number">0xFF</span>) <span class="kw">as </span>u8;
d4[<span class="number">2</span>] = node_id[<span class="number">0</span>];
d4[<span class="number">3</span>] = node_id[<span class="number">1</span>];
d4[<span class="number">4</span>] = node_id[<span class="number">2</span>];
d4[<span class="number">5</span>] = node_id[<span class="number">3</span>];
d4[<span class="number">6</span>] = node_id[<span class="number">4</span>];
d4[<span class="number">7</span>] = node_id[<span class="number">5</span>];
Uuid::from_fields(time_low, time_mid, time_high_and_version, <span class="kw-2">&amp;</span>d4)
}
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>decode_rfc4122_timestamp(uuid: <span class="kw-2">&amp;</span>Uuid) -&gt; (u64, u16) {
<span class="kw">let </span>bytes = uuid.as_bytes();
<span class="kw">let </span>ticks: u64 = ((bytes[<span class="number">6</span>] &amp; <span class="number">0x0F</span>) <span class="kw">as </span>u64) &lt;&lt; <span class="number">56
</span>| (bytes[<span class="number">7</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">48
</span>| (bytes[<span class="number">4</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">40
</span>| (bytes[<span class="number">5</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">32
</span>| (bytes[<span class="number">0</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">24
</span>| (bytes[<span class="number">1</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">16
</span>| (bytes[<span class="number">2</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">8
</span>| (bytes[<span class="number">3</span>] <span class="kw">as </span>u64);
<span class="kw">let </span>counter: u16 = ((bytes[<span class="number">8</span>] &amp; <span class="number">0x3F</span>) <span class="kw">as </span>u16) &lt;&lt; <span class="number">8 </span>| (bytes[<span class="number">9</span>] <span class="kw">as </span>u16);
(ticks, counter)
}
<span class="attribute">#[cfg(uuid_unstable)]
</span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>encode_sorted_rfc4122_timestamp(
ticks: u64,
counter: u16,
node_id: <span class="kw-2">&amp;</span>[u8; <span class="number">6</span>],
) -&gt; Uuid {
<span class="kw">let </span>time_high = ((ticks &gt;&gt; <span class="number">28</span>) &amp; <span class="number">0xFFFF_FFFF</span>) <span class="kw">as </span>u32;
<span class="kw">let </span>time_mid = ((ticks &gt;&gt; <span class="number">12</span>) &amp; <span class="number">0xFFFF</span>) <span class="kw">as </span>u16;
<span class="kw">let </span>time_low_and_version = ((ticks &amp; <span class="number">0x0FFF</span>) <span class="kw">as </span>u16) | (<span class="number">0x6 </span>&lt;&lt; <span class="number">12</span>);
<span class="kw">let </span><span class="kw-2">mut </span>d4 = [<span class="number">0</span>; <span class="number">8</span>];
d4[<span class="number">0</span>] = (((counter &amp; <span class="number">0x3F00</span>) &gt;&gt; <span class="number">8</span>) <span class="kw">as </span>u8) | <span class="number">0x80</span>;
d4[<span class="number">1</span>] = (counter &amp; <span class="number">0xFF</span>) <span class="kw">as </span>u8;
d4[<span class="number">2</span>] = node_id[<span class="number">0</span>];
d4[<span class="number">3</span>] = node_id[<span class="number">1</span>];
d4[<span class="number">4</span>] = node_id[<span class="number">2</span>];
d4[<span class="number">5</span>] = node_id[<span class="number">3</span>];
d4[<span class="number">6</span>] = node_id[<span class="number">4</span>];
d4[<span class="number">7</span>] = node_id[<span class="number">5</span>];
Uuid::from_fields(time_high, time_mid, time_low_and_version, <span class="kw-2">&amp;</span>d4)
}
<span class="attribute">#[cfg(uuid_unstable)]
</span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>decode_sorted_rfc4122_timestamp(uuid: <span class="kw-2">&amp;</span>Uuid) -&gt; (u64, u16) {
<span class="kw">let </span>bytes = uuid.as_bytes();
<span class="kw">let </span>ticks: u64 = ((bytes[<span class="number">0</span>]) <span class="kw">as </span>u64) &lt;&lt; <span class="number">52
</span>| (bytes[<span class="number">1</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">44
</span>| (bytes[<span class="number">2</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">36
</span>| (bytes[<span class="number">3</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">28
</span>| (bytes[<span class="number">4</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">20
</span>| (bytes[<span class="number">5</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">12
</span>| ((bytes[<span class="number">6</span>] &amp; <span class="number">0xF</span>) <span class="kw">as </span>u64) &lt;&lt; <span class="number">8
</span>| (bytes[<span class="number">7</span>] <span class="kw">as </span>u64);
<span class="kw">let </span>counter: u16 = ((bytes[<span class="number">8</span>] &amp; <span class="number">0x3F</span>) <span class="kw">as </span>u16) &lt;&lt; <span class="number">8 </span>| (bytes[<span class="number">9</span>] <span class="kw">as </span>u16);
(ticks, counter)
}
<span class="attribute">#[cfg(uuid_unstable)]
</span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>encode_unix_timestamp_millis(millis: u64, random_bytes: <span class="kw-2">&amp;</span>[u8; <span class="number">10</span>]) -&gt; Uuid {
<span class="kw">let </span>millis_high = ((millis &gt;&gt; <span class="number">16</span>) &amp; <span class="number">0xFFFF_FFFF</span>) <span class="kw">as </span>u32;
<span class="kw">let </span>millis_low = (millis &amp; <span class="number">0xFFFF</span>) <span class="kw">as </span>u16;
<span class="kw">let </span>random_and_version =
(random_bytes[<span class="number">0</span>] <span class="kw">as </span>u16 | ((random_bytes[<span class="number">1</span>] <span class="kw">as </span>u16) &lt;&lt; <span class="number">8</span>) &amp; <span class="number">0x0FFF</span>) | (<span class="number">0x7 </span>&lt;&lt; <span class="number">12</span>);
<span class="kw">let </span><span class="kw-2">mut </span>d4 = [<span class="number">0</span>; <span class="number">8</span>];
d4[<span class="number">0</span>] = (random_bytes[<span class="number">2</span>] &amp; <span class="number">0x3F</span>) | <span class="number">0x80</span>;
d4[<span class="number">1</span>] = random_bytes[<span class="number">3</span>];
d4[<span class="number">2</span>] = random_bytes[<span class="number">4</span>];
d4[<span class="number">3</span>] = random_bytes[<span class="number">5</span>];
d4[<span class="number">4</span>] = random_bytes[<span class="number">6</span>];
d4[<span class="number">5</span>] = random_bytes[<span class="number">7</span>];
d4[<span class="number">6</span>] = random_bytes[<span class="number">8</span>];
d4[<span class="number">7</span>] = random_bytes[<span class="number">9</span>];
Uuid::from_fields(millis_high, millis_low, random_and_version, <span class="kw-2">&amp;</span>d4)
}
<span class="attribute">#[cfg(uuid_unstable)]
</span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>decode_unix_timestamp_millis(uuid: <span class="kw-2">&amp;</span>Uuid) -&gt; u64 {
<span class="kw">let </span>bytes = uuid.as_bytes();
<span class="kw">let </span>millis: u64 = (bytes[<span class="number">0</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">40
</span>| (bytes[<span class="number">1</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">32
</span>| (bytes[<span class="number">2</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">24
</span>| (bytes[<span class="number">3</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">16
</span>| (bytes[<span class="number">4</span>] <span class="kw">as </span>u64) &lt;&lt; <span class="number">8
</span>| (bytes[<span class="number">5</span>] <span class="kw">as </span>u64);
millis
}
<span class="attribute">#[cfg(all(feature = <span class="string">&quot;std&quot;</span>, feature = <span class="string">&quot;js&quot;</span>, target_arch = <span class="string">&quot;wasm32&quot;</span>))]
</span><span class="kw">fn </span>now() -&gt; (u64, u32) {
<span class="kw">use </span>wasm_bindgen::prelude::<span class="kw-2">*</span>;
<span class="attribute">#[wasm_bindgen]
</span><span class="kw">extern </span><span class="string">&quot;C&quot; </span>{
<span class="attribute">#[wasm_bindgen(js_namespace = Date)]
</span><span class="kw">fn </span>now() -&gt; f64;
}
<span class="kw">let </span>now = now();
<span class="kw">let </span>secs = (now / <span class="number">1_000.0</span>) <span class="kw">as </span>u64;
<span class="kw">let </span>nanos = ((now % <span class="number">1_000.0</span>) * <span class="number">1_000_000.0</span>) <span class="kw">as </span>u32;
<span class="macro">dbg!</span>((secs, nanos))
}
<span class="attribute">#[cfg(all(feature = <span class="string">&quot;std&quot;</span>, any(not(feature = <span class="string">&quot;js&quot;</span>), not(target_arch = <span class="string">&quot;wasm32&quot;</span>))))]
</span><span class="kw">fn </span>now() -&gt; (u64, u32) {
<span class="kw">let </span>dur = std::time::SystemTime::UNIX_EPOCH
.elapsed()
.expect(<span class="string">&quot;Getting elapsed time since UNIX_EPOCH. If this fails, we&#39;ve somehow violated causality&quot;</span>);
(dur.as_secs(), dur.subsec_nanos())
}
<span class="doccomment">/// A counter that can be used by version 1 and version 6 UUIDs to support
/// the uniqueness of timestamps.
///
/// # References
///
/// * [Clock Sequence in RFC4122](https://datatracker.ietf.org/doc/html/rfc4122#section-4.1.5)
</span><span class="kw">pub trait </span>ClockSequence {
<span class="doccomment">/// The type of sequence returned by this counter.
</span><span class="kw">type </span>Output;
<span class="doccomment">/// Get the next value in the sequence to feed into a timestamp.
///
/// This method will be called each time a [`Timestamp`] is constructed.
</span><span class="kw">fn </span>generate_sequence(<span class="kw-2">&amp;</span><span class="self">self</span>, seconds: u64, subsec_nanos: u32) -&gt; <span class="self">Self</span>::Output;
}
<span class="kw">impl</span>&lt;<span class="lifetime">&#39;a</span>, T: ClockSequence + <span class="question-mark">?</span>Sized&gt; ClockSequence <span class="kw">for </span><span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>T {
<span class="kw">type </span>Output = T::Output;
<span class="kw">fn </span>generate_sequence(<span class="kw-2">&amp;</span><span class="self">self</span>, seconds: u64, subsec_nanos: u32) -&gt; <span class="self">Self</span>::Output {
(<span class="kw-2">**</span><span class="self">self</span>).generate_sequence(seconds, subsec_nanos)
}
}
<span class="doccomment">/// Default implementations for the [`ClockSequence`] trait.
</span><span class="kw">pub mod </span>context {
<span class="kw">use </span><span class="kw">super</span>::ClockSequence;
<span class="attribute">#[cfg(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>))]
</span><span class="kw">use </span>atomic::{Atomic, Ordering};
<span class="doccomment">/// An empty counter that will always return the value `0`.
///
/// This type should be used when constructing timestamps for version 7 UUIDs,
/// since they don&#39;t need a counter for uniqueness.
</span><span class="attribute">#[derive(Debug, Clone, Copy, Default)]
</span><span class="kw">pub struct </span>NoContext;
<span class="kw">impl </span>ClockSequence <span class="kw">for </span>NoContext {
<span class="kw">type </span>Output = u16;
<span class="kw">fn </span>generate_sequence(<span class="kw-2">&amp;</span><span class="self">self</span>, _seconds: u64, _nanos: u32) -&gt; <span class="self">Self</span>::Output {
<span class="number">0
</span>}
}
<span class="attribute">#[cfg(all(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>), feature = <span class="string">&quot;std&quot;</span>, feature = <span class="string">&quot;rng&quot;</span>))]
</span><span class="kw">static </span>CONTEXT: Context = Context {
count: Atomic::new(<span class="number">0</span>),
};
<span class="attribute">#[cfg(all(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>), feature = <span class="string">&quot;std&quot;</span>, feature = <span class="string">&quot;rng&quot;</span>))]
</span><span class="kw">static </span>CONTEXT_INITIALIZED: Atomic&lt;bool&gt; = Atomic::new(<span class="bool-val">false</span>);
<span class="attribute">#[cfg(all(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>), feature = <span class="string">&quot;std&quot;</span>, feature = <span class="string">&quot;rng&quot;</span>))]
</span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>shared_context() -&gt; <span class="kw-2">&amp;</span><span class="lifetime">&#39;static </span>Context {
<span class="comment">// If the context is in its initial state then assign it to a random value
// It doesn&#39;t matter if multiple threads observe `false` here and initialize the context
</span><span class="kw">if </span>CONTEXT_INITIALIZED
.compare_exchange(<span class="bool-val">false</span>, <span class="bool-val">true</span>, Ordering::Relaxed, Ordering::Relaxed)
.is_ok()
{
CONTEXT.count.store(<span class="kw">crate</span>::rng::u16(), Ordering::Release);
}
<span class="kw-2">&amp;</span>CONTEXT
}
<span class="doccomment">/// A thread-safe, wrapping counter that produces 14-bit numbers.
///
/// This type should be used when constructing version 1 and version 6 UUIDs.
</span><span class="attribute">#[derive(Debug)]
#[cfg(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>))]
</span><span class="kw">pub struct </span>Context {
count: Atomic&lt;u16&gt;,
}
<span class="attribute">#[cfg(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>))]
</span><span class="kw">impl </span>Context {
<span class="doccomment">/// Construct a new context that&#39;s initialized with the given value.
///
/// The starting value should be a random number, so that UUIDs from
/// different systems with the same timestamps are less likely to collide.
/// When the `rng` feature is enabled, prefer the [`Context::new_random`] method.
</span><span class="kw">pub const fn </span>new(count: u16) -&gt; <span class="self">Self </span>{
<span class="self">Self </span>{
count: Atomic::&lt;u16&gt;::new(count),
}
}
<span class="doccomment">/// Construct a new context that&#39;s initialized with a random value.
</span><span class="attribute">#[cfg(feature = <span class="string">&quot;rng&quot;</span>)]
</span><span class="kw">pub fn </span>new_random() -&gt; <span class="self">Self </span>{
<span class="self">Self </span>{
count: Atomic::&lt;u16&gt;::new(<span class="kw">crate</span>::rng::u16()),
}
}
}
<span class="attribute">#[cfg(any(feature = <span class="string">&quot;v1&quot;</span>, feature = <span class="string">&quot;v6&quot;</span>))]
</span><span class="kw">impl </span>ClockSequence <span class="kw">for </span>Context {
<span class="kw">type </span>Output = u16;
<span class="kw">fn </span>generate_sequence(<span class="kw-2">&amp;</span><span class="self">self</span>, _seconds: u64, _nanos: u32) -&gt; <span class="self">Self</span>::Output {
<span class="comment">// RFC4122 reserves 2 bits of the clock sequence so the actual
// maximum value is smaller than `u16::MAX`. Since we unconditionally
// increment the clock sequence we want to wrap once it becomes larger
// than what we can represent in a &quot;u14&quot;. Otherwise there&#39;d be patches
// where the clock sequence doesn&#39;t change regardless of the timestamp
</span><span class="self">self</span>.count.fetch_add(<span class="number">1</span>, Ordering::AcqRel) % (u16::MAX &gt;&gt; <span class="number">2</span>)
}
}
}
</code></pre></div>
</section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="uuid" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html>