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</pre><pre class="rust"><code><span class="doccomment">//! Callsites represent the source locations from which spans or events
//! originate.
//!
//! # What Are Callsites?
//!
//! Every span or event in `tracing` is associated with a [`Callsite`]. A
//! callsite is a small `static` value that is responsible for the following:
//!
//! * Storing the span or event&#39;s [`Metadata`],
//! * Uniquely [identifying](Identifier) the span or event definition,
//! * Caching the subscriber&#39;s [`Interest`][^1] in that span or event, to avoid
//! re-evaluating filters,
//! * Storing a [`Registration`] that allows the callsite to be part of a global
//! list of all callsites in the program.
//!
//! # Registering Callsites
//!
//! When a span or event is recorded for the first time, its callsite
//! [`register`]s itself with the global callsite registry. Registering a
//! callsite calls the [`Subscriber::register_callsite`][`register_callsite`]
//! method with that callsite&#39;s [`Metadata`] on every currently active
//! subscriber. This serves two primary purposes: informing subscribers of the
//! callsite&#39;s existence, and performing static filtering.
//!
//! ## Callsite Existence
//!
//! If a [`Subscriber`] implementation wishes to allocate storage for each
//! unique span/event location in the program, or pre-compute some value
//! that will be used to record that span or event in the future, it can
//! do so in its [`register_callsite`] method.
//!
//! ## Performing Static Filtering
//!
//! The [`register_callsite`] method returns an [`Interest`] value,
//! which indicates that the subscriber either [always] wishes to record
//! that span or event, [sometimes] wishes to record it based on a
//! dynamic filter evaluation, or [never] wishes to record it.
//!
//! When registering a new callsite, the [`Interest`]s returned by every
//! currently active subscriber are combined, and the result is stored at
//! each callsite. This way, when the span or event occurs in the
//! future, the cached [`Interest`] value can be checked efficiently
//! to determine if the span or event should be recorded, without
//! needing to perform expensive filtering (i.e. calling the
//! [`Subscriber::enabled`] method every time a span or event occurs).
//!
//! ### Rebuilding Cached Interest
//!
//! When a new [`Dispatch`] is created (i.e. a new subscriber becomes
//! active), any previously cached [`Interest`] values are re-evaluated
//! for all callsites in the program. This way, if the new subscriber
//! will enable a callsite that was not previously enabled, the
//! [`Interest`] in that callsite is updated. Similarly, when a
//! subscriber is dropped, the interest cache is also re-evaluated, so
//! that any callsites enabled only by that subscriber are disabled.
//!
//! In addition, the [`rebuild_interest_cache`] function in this module can be
//! used to manually invalidate all cached interest and re-register those
//! callsites. This function is useful in situations where a subscriber&#39;s
//! interest can change, but it does so relatively infrequently. The subscriber
//! may wish for its interest to be cached most of the time, and return
//! [`Interest::always`][always] or [`Interest::never`][never] in its
//! [`register_callsite`] method, so that its [`Subscriber::enabled`] method
//! doesn&#39;t need to be evaluated every time a span or event is recorded.
//! However, when the configuration changes, the subscriber can call
//! [`rebuild_interest_cache`] to re-evaluate the entire interest cache with its
//! new configuration. This is a relatively costly operation, but if the
//! configuration changes infrequently, it may be more efficient than calling
//! [`Subscriber::enabled`] frequently.
//!
//! # Implementing Callsites
//!
//! In most cases, instrumenting code using `tracing` should *not* require
//! implementing the [`Callsite`] trait directly. When using the [`tracing`
//! crate&#39;s macros][macros] or the [`#[instrument]` attribute][instrument], a
//! `Callsite` is automatically generated.
//!
//! However, code which provides alternative forms of `tracing` instrumentation
//! may need to interact with the callsite system directly. If
//! instrumentation-side code needs to produce a `Callsite` to emit spans or
//! events, the [`DefaultCallsite`] struct provided in this module is a
//! ready-made `Callsite` implementation that is suitable for most uses. When
//! possible, the use of `DefaultCallsite` should be preferred over implementing
//! [`Callsite`] for user types, as `DefaultCallsite` may benefit from
//! additional performance optimizations.
//!
//! [^1]: Returned by the [`Subscriber::register_callsite`][`register_callsite`]
//! method.
//!
//! [`Metadata`]: crate::metadata::Metadata
//! [`Interest`]: crate::subscriber::Interest
//! [`Subscriber`]: crate::subscriber::Subscriber
//! [`register_callsite`]: crate::subscriber::Subscriber::register_callsite
//! [`Subscriber::enabled`]: crate::subscriber::Subscriber::enabled
//! [always]: crate::subscriber::Interest::always
//! [sometimes]: crate::subscriber::Interest::sometimes
//! [never]: crate::subscriber::Interest::never
//! [`Dispatch`]: crate::dispatch::Dispatch
//! [macros]: https://docs.rs/tracing/latest/tracing/#macros
//! [instrument]: https://docs.rs/tracing/latest/tracing/attr.instrument.html
</span><span class="kw">use </span><span class="kw">crate</span>::stdlib::{
any::TypeId,
fmt,
hash::{Hash, Hasher},
ptr,
sync::{
atomic::{AtomicBool, AtomicPtr, AtomicU8, Ordering},
Mutex,
},
vec::Vec,
};
<span class="kw">use crate</span>::{
dispatcher::Dispatch,
lazy::Lazy,
metadata::{LevelFilter, Metadata},
subscriber::Interest,
};
<span class="kw">use </span><span class="self">self</span>::dispatchers::Dispatchers;
<span class="doccomment">/// Trait implemented by callsites.
///
/// These functions are only intended to be called by the callsite registry, which
/// correctly handles determining the common interest between all subscribers.
///
/// See the [module-level documentation](crate::callsite) for details on
/// callsites.
</span><span class="kw">pub trait </span>Callsite: Sync {
<span class="doccomment">/// Sets the [`Interest`] for this callsite.
///
/// See the [documentation on callsite interest caching][cache-docs] for
/// details.
///
/// [`Interest`]: super::subscriber::Interest
/// [cache-docs]: crate::callsite#performing-static-filtering
</span><span class="kw">fn </span>set_interest(<span class="kw-2">&amp;</span><span class="self">self</span>, interest: Interest);
<span class="doccomment">/// Returns the [metadata] associated with the callsite.
///
/// &lt;div class=&quot;example-wrap&quot; style=&quot;display:inline-block&quot;&gt;
/// &lt;pre class=&quot;ignore&quot; style=&quot;white-space:normal;font:inherit;&quot;&gt;
///
/// **Note:** Implementations of this method should not produce [`Metadata`]
/// that share the same callsite [`Identifier`] but otherwise differ in any
/// way (e.g., have different `name`s).
///
/// &lt;/pre&gt;&lt;/div&gt;
///
/// [metadata]: super::metadata::Metadata
</span><span class="kw">fn </span>metadata(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; <span class="kw-2">&amp;</span>Metadata&lt;<span class="lifetime">&#39;_</span>&gt;;
<span class="doccomment">/// This method is an *internal implementation detail* of `tracing-core`. It
/// is *not* intended to be called or overridden from downstream code.
///
/// The `Private` type can only be constructed from within `tracing-core`.
/// Because this method takes a `Private` as an argument, it cannot be
/// called from (safe) code external to `tracing-core`. Because it must
/// *return* a `Private`, the only valid implementation possible outside of
/// `tracing-core` would have to always unconditionally panic.
///
/// THIS IS BY DESIGN. There is currently no valid reason for code outside
/// of `tracing-core` to override this method.
</span><span class="comment">// TODO(eliza): this could be used to implement a public downcasting API
// for `&amp;dyn Callsite`s in the future.
</span><span class="attribute">#[doc(hidden)]
#[inline]
</span><span class="kw">fn </span>private_type_id(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="kw">_</span>: private::Private&lt;()&gt;) -&gt; private::Private&lt;TypeId&gt;
<span class="kw">where
</span><span class="self">Self</span>: <span class="lifetime">&#39;static</span>,
{
private::Private(TypeId::of::&lt;<span class="self">Self</span>&gt;())
}
}
<span class="doccomment">/// Uniquely identifies a [`Callsite`]
///
/// Two `Identifier`s are equal if they both refer to the same callsite.
///
/// [`Callsite`]: super::callsite::Callsite
</span><span class="attribute">#[derive(Clone)]
</span><span class="kw">pub struct </span>Identifier(
<span class="doccomment">/// **Warning**: The fields on this type are currently `pub` because it must
/// be able to be constructed statically by macros. However, when `const
/// fn`s are available on stable Rust, this will no longer be necessary.
/// Thus, these fields are *not* considered stable public API, and they may
/// change warning. Do not rely on any fields on `Identifier`. When
/// constructing new `Identifier`s, use the `identify_callsite!` macro
/// instead.
</span><span class="attribute">#[doc(hidden)]
</span><span class="kw">pub </span><span class="kw-2">&amp;</span><span class="lifetime">&#39;static </span><span class="kw">dyn </span>Callsite,
);
<span class="doccomment">/// A default [`Callsite`] implementation.
</span><span class="attribute">#[derive(Debug)]
</span><span class="kw">pub struct </span>DefaultCallsite {
interest: AtomicU8,
registration: AtomicU8,
meta: <span class="kw-2">&amp;</span><span class="lifetime">&#39;static </span>Metadata&lt;<span class="lifetime">&#39;static</span>&gt;,
next: AtomicPtr&lt;<span class="self">Self</span>&gt;,
}
<span class="doccomment">/// Clear and reregister interest on every [`Callsite`]
///
/// This function is intended for runtime reconfiguration of filters on traces
/// when the filter recalculation is much less frequent than trace events are.
/// The alternative is to have the [`Subscriber`] that supports runtime
/// reconfiguration of filters always return [`Interest::sometimes()`] so that
/// [`enabled`] is evaluated for every event.
///
/// This function will also re-compute the global maximum level as determined by
/// the [`max_level_hint`] method. If a [`Subscriber`]
/// implementation changes the value returned by its `max_level_hint`
/// implementation at runtime, then it **must** call this function after that
/// value changes, in order for the change to be reflected.
///
/// See the [documentation on callsite interest caching][cache-docs] for
/// additional information on this function&#39;s usage.
///
/// [`max_level_hint`]: super::subscriber::Subscriber::max_level_hint
/// [`Callsite`]: super::callsite::Callsite
/// [`enabled`]: super::subscriber::Subscriber#tymethod.enabled
/// [`Interest::sometimes()`]: super::subscriber::Interest::sometimes
/// [`Subscriber`]: super::subscriber::Subscriber
/// [cache-docs]: crate::callsite#rebuilding-cached-interest
</span><span class="kw">pub fn </span>rebuild_interest_cache() {
CALLSITES.rebuild_interest(DISPATCHERS.rebuilder());
}
<span class="doccomment">/// Register a new [`Callsite`] with the global registry.
///
/// This should be called once per callsite after the callsite has been
/// constructed.
///
/// See the [documentation on callsite registration][reg-docs] for details
/// on the global callsite registry.
///
/// [`Callsite`]: crate::callsite::Callsite
/// [reg-docs]: crate::callsite#registering-callsites
</span><span class="kw">pub fn </span>register(callsite: <span class="kw-2">&amp;</span><span class="lifetime">&#39;static </span><span class="kw">dyn </span>Callsite) {
rebuild_callsite_interest(callsite, <span class="kw-2">&amp;</span>DISPATCHERS.rebuilder());
<span class="comment">// Is this a `DefaultCallsite`? If so, use the fancy linked list!
</span><span class="kw">if </span>callsite.private_type_id(private::Private(())).<span class="number">0 </span>== TypeId::of::&lt;DefaultCallsite&gt;() {
<span class="kw">let </span>callsite = <span class="kw">unsafe </span>{
<span class="comment">// Safety: the pointer cast is safe because the type id of the
// provided callsite matches that of the target type for the cast
// (`DefaultCallsite`). Because user implementations of `Callsite`
// cannot override `private_type_id`, we can trust that the callsite
// is not lying about its type ID.
</span><span class="kw-2">&amp;*</span>(callsite <span class="kw">as </span><span class="kw-2">*const </span><span class="kw">dyn </span>Callsite <span class="kw">as </span><span class="kw-2">*const </span>DefaultCallsite)
};
CALLSITES.push_default(callsite);
<span class="kw">return</span>;
}
CALLSITES.push_dyn(callsite);
}
<span class="kw">static </span>CALLSITES: Callsites = Callsites {
list_head: AtomicPtr::new(ptr::null_mut()),
has_locked_callsites: AtomicBool::new(<span class="bool-val">false</span>),
};
<span class="kw">static </span>DISPATCHERS: Dispatchers = Dispatchers::new();
<span class="kw">static </span>LOCKED_CALLSITES: Lazy&lt;Mutex&lt;Vec&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;static </span><span class="kw">dyn </span>Callsite&gt;&gt;&gt; = Lazy::new(Default::default);
<span class="kw">struct </span>Callsites {
list_head: AtomicPtr&lt;DefaultCallsite&gt;,
has_locked_callsites: AtomicBool,
}
<span class="comment">// === impl DefaultCallsite ===
</span><span class="kw">impl </span>DefaultCallsite {
<span class="kw">const </span>UNREGISTERED: u8 = <span class="number">0</span>;
<span class="kw">const </span>REGISTERING: u8 = <span class="number">1</span>;
<span class="kw">const </span>REGISTERED: u8 = <span class="number">2</span>;
<span class="kw">const </span>INTEREST_NEVER: u8 = <span class="number">0</span>;
<span class="kw">const </span>INTEREST_SOMETIMES: u8 = <span class="number">1</span>;
<span class="kw">const </span>INTEREST_ALWAYS: u8 = <span class="number">2</span>;
<span class="doccomment">/// Returns a new `DefaultCallsite` with the specified `Metadata`.
</span><span class="kw">pub const fn </span>new(meta: <span class="kw-2">&amp;</span><span class="lifetime">&#39;static </span>Metadata&lt;<span class="lifetime">&#39;static</span>&gt;) -&gt; <span class="self">Self </span>{
<span class="self">Self </span>{
interest: AtomicU8::new(<span class="number">0xFF</span>),
meta,
next: AtomicPtr::new(ptr::null_mut()),
registration: AtomicU8::new(<span class="self">Self</span>::UNREGISTERED),
}
}
<span class="doccomment">/// Registers this callsite with the global callsite registry.
///
/// If the callsite is already registered, this does nothing. When using
/// [`DefaultCallsite`], this method should be preferred over
/// [`tracing_core::callsite::register`], as it ensures that the callsite is
/// only registered a single time.
///
/// Other callsite implementations will generally ensure that
/// callsites are not re-registered through another mechanism.
///
/// See the [documentation on callsite registration][reg-docs] for details
/// on the global callsite registry.
///
/// [`Callsite`]: crate::callsite::Callsite
/// [reg-docs]: crate::callsite#registering-callsites
</span><span class="attribute">#[inline(never)]
</span><span class="comment">// This only happens once (or if the cached interest value was corrupted).
</span><span class="attribute">#[cold]
</span><span class="kw">pub fn </span>register(<span class="kw-2">&amp;</span><span class="lifetime">&#39;static </span><span class="self">self</span>) -&gt; Interest {
<span class="comment">// Attempt to advance the registration state to `REGISTERING`...
</span><span class="kw">match </span><span class="self">self</span>.registration.compare_exchange(
<span class="self">Self</span>::UNREGISTERED,
<span class="self">Self</span>::REGISTERING,
Ordering::AcqRel,
Ordering::Acquire,
) {
<span class="prelude-val">Ok</span>(<span class="kw">_</span>) =&gt; {
<span class="comment">// Okay, we advanced the state, try to register the callsite.
</span>rebuild_callsite_interest(<span class="self">self</span>, <span class="kw-2">&amp;</span>DISPATCHERS.rebuilder());
CALLSITES.push_default(<span class="self">self</span>);
<span class="self">self</span>.registration.store(<span class="self">Self</span>::REGISTERED, Ordering::Release);
}
<span class="comment">// Great, the callsite is already registered! Just load its
// previous cached interest.
</span><span class="prelude-val">Err</span>(<span class="self">Self</span>::REGISTERED) =&gt; {}
<span class="comment">// Someone else is registering...
</span><span class="prelude-val">Err</span>(_state) =&gt; {
<span class="macro">debug_assert_eq!</span>(
_state,
<span class="self">Self</span>::REGISTERING,
<span class="string">&quot;weird callsite registration state&quot;
</span>);
<span class="comment">// Just hit `enabled` this time.
</span><span class="kw">return </span>Interest::sometimes();
}
}
<span class="kw">match </span><span class="self">self</span>.interest.load(Ordering::Relaxed) {
<span class="self">Self</span>::INTEREST_NEVER =&gt; Interest::never(),
<span class="self">Self</span>::INTEREST_ALWAYS =&gt; Interest::always(),
<span class="kw">_ </span>=&gt; Interest::sometimes(),
}
}
<span class="doccomment">/// Returns the callsite&#39;s cached `Interest`, or registers it for the
/// first time if it has not yet been registered.
</span><span class="attribute">#[inline]
</span><span class="kw">pub fn </span>interest(<span class="kw-2">&amp;</span><span class="lifetime">&#39;static </span><span class="self">self</span>) -&gt; Interest {
<span class="kw">match </span><span class="self">self</span>.interest.load(Ordering::Relaxed) {
<span class="self">Self</span>::INTEREST_NEVER =&gt; Interest::never(),
<span class="self">Self</span>::INTEREST_SOMETIMES =&gt; Interest::sometimes(),
<span class="self">Self</span>::INTEREST_ALWAYS =&gt; Interest::always(),
<span class="kw">_ </span>=&gt; <span class="self">self</span>.register(),
}
}
}
<span class="kw">impl </span>Callsite <span class="kw">for </span>DefaultCallsite {
<span class="kw">fn </span>set_interest(<span class="kw-2">&amp;</span><span class="self">self</span>, interest: Interest) {
<span class="kw">let </span>interest = <span class="kw">match </span>() {
<span class="kw">_ if </span>interest.is_never() =&gt; <span class="self">Self</span>::INTEREST_NEVER,
<span class="kw">_ if </span>interest.is_always() =&gt; <span class="self">Self</span>::INTEREST_ALWAYS,
<span class="kw">_ </span>=&gt; <span class="self">Self</span>::INTEREST_SOMETIMES,
};
<span class="self">self</span>.interest.store(interest, Ordering::SeqCst);
}
<span class="attribute">#[inline(always)]
</span><span class="kw">fn </span>metadata(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; <span class="kw-2">&amp;</span>Metadata&lt;<span class="lifetime">&#39;static</span>&gt; {
<span class="self">self</span>.meta
}
}
<span class="comment">// ===== impl Identifier =====
</span><span class="kw">impl </span>PartialEq <span class="kw">for </span>Identifier {
<span class="kw">fn </span>eq(<span class="kw-2">&amp;</span><span class="self">self</span>, other: <span class="kw-2">&amp;</span>Identifier) -&gt; bool {
core::ptr::eq(
<span class="self">self</span>.<span class="number">0 </span><span class="kw">as </span><span class="kw-2">*const </span><span class="kw">_ as </span><span class="kw-2">*const </span>(),
other.<span class="number">0 </span><span class="kw">as </span><span class="kw-2">*const </span><span class="kw">_ as </span><span class="kw-2">*const </span>(),
)
}
}
<span class="kw">impl </span>Eq <span class="kw">for </span>Identifier {}
<span class="kw">impl </span>fmt::Debug <span class="kw">for </span>Identifier {
<span class="kw">fn </span>fmt(<span class="kw-2">&amp;</span><span class="self">self</span>, f: <span class="kw-2">&amp;mut </span>fmt::Formatter&lt;<span class="lifetime">&#39;_</span>&gt;) -&gt; fmt::Result {
<span class="macro">write!</span>(f, <span class="string">&quot;Identifier({:p})&quot;</span>, <span class="self">self</span>.<span class="number">0</span>)
}
}
<span class="kw">impl </span>Hash <span class="kw">for </span>Identifier {
<span class="kw">fn </span>hash&lt;H&gt;(<span class="kw-2">&amp;</span><span class="self">self</span>, state: <span class="kw-2">&amp;mut </span>H)
<span class="kw">where
</span>H: Hasher,
{
(<span class="self">self</span>.<span class="number">0 </span><span class="kw">as </span><span class="kw-2">*const </span><span class="kw">dyn </span>Callsite).hash(state)
}
}
<span class="comment">// === impl Callsites ===
</span><span class="kw">impl </span>Callsites {
<span class="doccomment">/// Rebuild `Interest`s for all callsites in the registry.
///
/// This also re-computes the max level hint.
</span><span class="kw">fn </span>rebuild_interest(<span class="kw-2">&amp;</span><span class="self">self</span>, dispatchers: dispatchers::Rebuilder&lt;<span class="lifetime">&#39;_</span>&gt;) {
<span class="kw">let </span><span class="kw-2">mut </span>max_level = LevelFilter::OFF;
dispatchers.for_each(|dispatch| {
<span class="comment">// If the subscriber did not provide a max level hint, assume
// that it may enable every level.
</span><span class="kw">let </span>level_hint = dispatch.max_level_hint().unwrap_or(LevelFilter::TRACE);
<span class="kw">if </span>level_hint &gt; max_level {
max_level = level_hint;
}
});
<span class="self">self</span>.for_each(|callsite| {
rebuild_callsite_interest(callsite, <span class="kw-2">&amp;</span>dispatchers);
});
LevelFilter::set_max(max_level);
}
<span class="doccomment">/// Push a `dyn Callsite` trait object to the callsite registry.
///
/// This will attempt to lock the callsites vector.
</span><span class="kw">fn </span>push_dyn(<span class="kw-2">&amp;</span><span class="self">self</span>, callsite: <span class="kw-2">&amp;</span><span class="lifetime">&#39;static </span><span class="kw">dyn </span>Callsite) {
<span class="kw">let </span><span class="kw-2">mut </span>lock = LOCKED_CALLSITES.lock().unwrap();
<span class="self">self</span>.has_locked_callsites.store(<span class="bool-val">true</span>, Ordering::Release);
lock.push(callsite);
}
<span class="doccomment">/// Push a `DefaultCallsite` to the callsite registry.
///
/// If we know the callsite being pushed is a `DefaultCallsite`, we can push
/// it to the linked list without having to acquire a lock.
</span><span class="kw">fn </span>push_default(<span class="kw-2">&amp;</span><span class="self">self</span>, callsite: <span class="kw-2">&amp;</span><span class="lifetime">&#39;static </span>DefaultCallsite) {
<span class="kw">let </span><span class="kw-2">mut </span>head = <span class="self">self</span>.list_head.load(Ordering::Acquire);
<span class="kw">loop </span>{
callsite.next.store(head, Ordering::Release);
<span class="macro">assert_ne!</span>(
callsite <span class="kw">as </span><span class="kw-2">*const </span><span class="kw">_</span>, head,
<span class="string">&quot;Attempted to register a `DefaultCallsite` that already exists! \
This will cause an infinite loop when attempting to read from the \
callsite cache. This is likely a bug! You should only need to call \
`DefaultCallsite::register` once per `DefaultCallsite`.&quot;
</span>);
<span class="kw">match </span><span class="self">self</span>.list_head.compare_exchange(
head,
callsite <span class="kw">as </span><span class="kw-2">*const </span><span class="kw">_ as </span><span class="kw-2">*mut </span><span class="kw">_</span>,
Ordering::AcqRel,
Ordering::Acquire,
) {
<span class="prelude-val">Ok</span>(<span class="kw">_</span>) =&gt; {
<span class="kw">break</span>;
}
<span class="prelude-val">Err</span>(current) =&gt; head = current,
}
}
}
<span class="doccomment">/// Invokes the provided closure `f` with each callsite in the registry.
</span><span class="kw">fn </span>for_each(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="kw-2">mut </span>f: <span class="kw">impl </span>FnMut(<span class="kw-2">&amp;</span><span class="lifetime">&#39;static </span><span class="kw">dyn </span>Callsite)) {
<span class="kw">let </span><span class="kw-2">mut </span>head = <span class="self">self</span>.list_head.load(Ordering::Acquire);
<span class="kw">while let </span><span class="prelude-val">Some</span>(cs) = <span class="kw">unsafe </span>{ head.as_ref() } {
f(cs);
head = cs.next.load(Ordering::Acquire);
}
<span class="kw">if </span><span class="self">self</span>.has_locked_callsites.load(Ordering::Acquire) {
<span class="kw">let </span>locked = LOCKED_CALLSITES.lock().unwrap();
<span class="kw">for </span><span class="kw-2">&amp;</span>cs <span class="kw">in </span>locked.iter() {
f(cs);
}
}
}
}
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>register_dispatch(dispatch: <span class="kw-2">&amp;</span>Dispatch) {
<span class="kw">let </span>dispatchers = DISPATCHERS.register_dispatch(dispatch);
dispatch.subscriber().on_register_dispatch(dispatch);
CALLSITES.rebuild_interest(dispatchers);
}
<span class="kw">fn </span>rebuild_callsite_interest(
callsite: <span class="kw-2">&amp;</span><span class="lifetime">&#39;static </span><span class="kw">dyn </span>Callsite,
dispatchers: <span class="kw-2">&amp;</span>dispatchers::Rebuilder&lt;<span class="lifetime">&#39;_</span>&gt;,
) {
<span class="kw">let </span>meta = callsite.metadata();
<span class="kw">let </span><span class="kw-2">mut </span>interest = <span class="prelude-val">None</span>;
dispatchers.for_each(|dispatch| {
<span class="kw">let </span>this_interest = dispatch.register_callsite(meta);
interest = <span class="kw">match </span>interest.take() {
<span class="prelude-val">None </span>=&gt; <span class="prelude-val">Some</span>(this_interest),
<span class="prelude-val">Some</span>(that_interest) =&gt; <span class="prelude-val">Some</span>(that_interest.and(this_interest)),
}
});
<span class="kw">let </span>interest = interest.unwrap_or_else(Interest::never);
callsite.set_interest(interest)
}
<span class="kw">mod </span>private {
<span class="doccomment">/// Don&#39;t call this function, it&#39;s private.
</span><span class="attribute">#[allow(missing_debug_implementations)]
</span><span class="kw">pub struct </span>Private&lt;T&gt;(<span class="kw">pub</span>(<span class="kw">crate</span>) T);
}
<span class="attribute">#[cfg(feature = <span class="string">&quot;std&quot;</span>)]
</span><span class="kw">mod </span>dispatchers {
<span class="kw">use crate</span>::{dispatcher, lazy::Lazy};
<span class="kw">use </span>std::sync::{
atomic::{AtomicBool, Ordering},
RwLock, RwLockReadGuard, RwLockWriteGuard,
};
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>Dispatchers {
has_just_one: AtomicBool,
}
<span class="kw">static </span>LOCKED_DISPATCHERS: Lazy&lt;RwLock&lt;Vec&lt;dispatcher::Registrar&gt;&gt;&gt; =
Lazy::new(Default::default);
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">enum </span>Rebuilder&lt;<span class="lifetime">&#39;a</span>&gt; {
JustOne,
Read(RwLockReadGuard&lt;<span class="lifetime">&#39;a</span>, Vec&lt;dispatcher::Registrar&gt;&gt;),
Write(RwLockWriteGuard&lt;<span class="lifetime">&#39;a</span>, Vec&lt;dispatcher::Registrar&gt;&gt;),
}
<span class="kw">impl </span>Dispatchers {
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">const fn </span>new() -&gt; <span class="self">Self </span>{
<span class="self">Self </span>{
has_just_one: AtomicBool::new(<span class="bool-val">true</span>),
}
}
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>rebuilder(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; Rebuilder&lt;<span class="lifetime">&#39;_</span>&gt; {
<span class="kw">if </span><span class="self">self</span>.has_just_one.load(Ordering::SeqCst) {
<span class="kw">return </span>Rebuilder::JustOne;
}
Rebuilder::Read(LOCKED_DISPATCHERS.read().unwrap())
}
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>register_dispatch(<span class="kw-2">&amp;</span><span class="self">self</span>, dispatch: <span class="kw-2">&amp;</span>dispatcher::Dispatch) -&gt; Rebuilder&lt;<span class="lifetime">&#39;_</span>&gt; {
<span class="kw">let </span><span class="kw-2">mut </span>dispatchers = LOCKED_DISPATCHERS.write().unwrap();
dispatchers.retain(|d| d.upgrade().is_some());
dispatchers.push(dispatch.registrar());
<span class="self">self</span>.has_just_one
.store(dispatchers.len() &lt;= <span class="number">1</span>, Ordering::SeqCst);
Rebuilder::Write(dispatchers)
}
}
<span class="kw">impl </span>Rebuilder&lt;<span class="lifetime">&#39;_</span>&gt; {
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>for_each(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="kw-2">mut </span>f: <span class="kw">impl </span>FnMut(<span class="kw-2">&amp;</span>dispatcher::Dispatch)) {
<span class="kw">let </span>iter = <span class="kw">match </span><span class="self">self </span>{
Rebuilder::JustOne =&gt; {
dispatcher::get_default(f);
<span class="kw">return</span>;
}
Rebuilder::Read(vec) =&gt; vec.iter(),
Rebuilder::Write(vec) =&gt; vec.iter(),
};
iter.filter_map(dispatcher::Registrar::upgrade)
.for_each(|dispatch| f(<span class="kw-2">&amp;</span>dispatch))
}
}
}
<span class="attribute">#[cfg(not(feature = <span class="string">&quot;std&quot;</span>))]
</span><span class="kw">mod </span>dispatchers {
<span class="kw">use </span><span class="kw">crate</span>::dispatcher;
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>Dispatchers(());
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>Rebuilder&lt;<span class="lifetime">&#39;a</span>&gt;(<span class="prelude-ty">Option</span>&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>dispatcher::Dispatch&gt;);
<span class="kw">impl </span>Dispatchers {
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">const fn </span>new() -&gt; <span class="self">Self </span>{
<span class="self">Self</span>(())
}
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>rebuilder(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; Rebuilder&lt;<span class="lifetime">&#39;_</span>&gt; {
Rebuilder(<span class="prelude-val">None</span>)
}
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>register_dispatch&lt;<span class="lifetime">&#39;dispatch</span>&gt;(
<span class="kw-2">&amp;</span><span class="self">self</span>,
dispatch: <span class="kw-2">&amp;</span><span class="lifetime">&#39;dispatch </span>dispatcher::Dispatch,
) -&gt; Rebuilder&lt;<span class="lifetime">&#39;dispatch</span>&gt; {
<span class="comment">// nop; on no_std, there can only ever be one dispatcher
</span>Rebuilder(<span class="prelude-val">Some</span>(dispatch))
}
}
<span class="kw">impl </span>Rebuilder&lt;<span class="lifetime">&#39;_</span>&gt; {
<span class="attribute">#[inline]
</span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>for_each(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="kw-2">mut </span>f: <span class="kw">impl </span>FnMut(<span class="kw-2">&amp;</span>dispatcher::Dispatch)) {
<span class="kw">if let </span><span class="prelude-val">Some</span>(dispatch) = <span class="self">self</span>.<span class="number">0 </span>{
<span class="comment">// we are rebuilding the interest cache because a new dispatcher
// is about to be set. on `no_std`, this should only happen
// once, because the new dispatcher will be the global default.
</span>f(dispatch)
} <span class="kw">else </span>{
<span class="comment">// otherwise, we are rebuilding the cache because the subscriber
// configuration changed, so use the global default.
// on no_std, there can only ever be one dispatcher
</span>dispatcher::get_default(f)
}
}
}
}
</code></pre></div>
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