<!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 `/home/sangenya/.cargo/registry/src/github.com-1ecc6299db9ec823/crossbeam-channel-0.5.1/src/flavors/list.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>list.rs - source</title><link rel="stylesheet" type="text/css" href="../../../normalize.css"><link rel="stylesheet" type="text/css" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../../light.css" id="themeStyle"><link rel="stylesheet" type="text/css" href="../../../dark.css" disabled ><link rel="stylesheet" type="text/css" href="../../../ayu.css" disabled ><script id="default-settings"></script><script src="../../../storage.js"></script><script src="../../../crates.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="icon" type="image/svg+xml" href="../../../favicon.svg">
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</pre><pre class="rust">
<span class="doccomment">//! Unbounded channel implemented as a linked list.</span>
<span class="kw">use</span> <span class="ident">std::cell::UnsafeCell</span>;
<span class="kw">use</span> <span class="ident">std::marker::PhantomData</span>;
<span class="kw">use</span> <span class="ident">std::mem::MaybeUninit</span>;
<span class="kw">use</span> <span class="ident">std::ptr</span>;
<span class="kw">use</span> <span class="ident">std::sync::atomic</span>::{<span class="self">self</span>, <span class="ident">AtomicPtr</span>, <span class="ident">AtomicUsize</span>, <span class="ident">Ordering</span>};
<span class="kw">use</span> <span class="ident">std::time::Instant</span>;
<span class="kw">use</span> <span class="ident">crossbeam_utils</span>::{<span class="ident">Backoff</span>, <span class="ident">CachePadded</span>};
<span class="kw">use</span> <span class="kw">crate</span><span class="ident">::context::Context</span>;
<span class="kw">use</span> <span class="kw">crate</span><span class="ident">::err</span>::{<span class="ident">RecvTimeoutError</span>, <span class="ident">SendTimeoutError</span>, <span class="ident">TryRecvError</span>, <span class="ident">TrySendError</span>};
<span class="kw">use</span> <span class="kw">crate</span><span class="ident">::select</span>::{<span class="ident">Operation</span>, <span class="ident">SelectHandle</span>, <span class="ident">Selected</span>, <span class="ident">Token</span>};
<span class="kw">use</span> <span class="kw">crate</span><span class="ident">::waker::SyncWaker</span>;
<span class="comment">// TODO(stjepang): Once we bump the minimum required Rust version to 1.28 or newer, re-apply the</span>
<span class="comment">// following changes by @kleimkuhler:</span>
<span class="comment">//</span>
<span class="comment">// 1. https://github.com/crossbeam-rs/crossbeam-channel/pull/100</span>
<span class="comment">// 2. https://github.com/crossbeam-rs/crossbeam-channel/pull/101</span>
<span class="comment">// Bits indicating the state of a slot:</span>
<span class="comment">// * If a message has been written into the slot, `WRITE` is set.</span>
<span class="comment">// * If a message has been read from the slot, `READ` is set.</span>
<span class="comment">// * If the block is being destroyed, `DESTROY` is set.</span>
<span class="kw">const</span> <span class="ident">WRITE</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">1</span>;
<span class="kw">const</span> <span class="ident">READ</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">2</span>;
<span class="kw">const</span> <span class="ident">DESTROY</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">4</span>;
<span class="comment">// Each block covers one "lap" of indices.</span>
<span class="kw">const</span> <span class="ident">LAP</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">32</span>;
<span class="comment">// The maximum number of messages a block can hold.</span>
<span class="kw">const</span> <span class="ident">BLOCK_CAP</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="ident">LAP</span> <span class="op">-</span> <span class="number">1</span>;
<span class="comment">// How many lower bits are reserved for metadata.</span>
<span class="kw">const</span> <span class="ident">SHIFT</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">1</span>;
<span class="comment">// Has two different purposes:</span>
<span class="comment">// * If set in head, indicates that the block is not the last one.</span>
<span class="comment">// * If set in tail, indicates that the channel is disconnected.</span>
<span class="kw">const</span> <span class="ident">MARK_BIT</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">1</span>;
<span class="doccomment">/// A slot in a block.</span>
<span class="kw">struct</span> <span class="ident">Slot</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// The message.</span>
<span class="ident">msg</span>: <span class="ident">UnsafeCell</span><span class="op"><</span><span class="ident">MaybeUninit</span><span class="op"><</span><span class="ident">T</span><span class="op">></span><span class="op">></span>,
<span class="doccomment">/// The state of the slot.</span>
<span class="ident">state</span>: <span class="ident">AtomicUsize</span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Slot</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Waits until a message is written into the slot.</span>
<span class="kw">fn</span> <span class="ident">wait_write</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">let</span> <span class="ident">backoff</span> <span class="op">=</span> <span class="ident">Backoff::new</span>();
<span class="kw">while</span> <span class="self">self</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>) <span class="op">&</span> <span class="ident">WRITE</span> <span class="op">=</span><span class="op">=</span> <span class="number">0</span> {
<span class="ident">backoff</span>.<span class="ident">snooze</span>();
}
}
}
<span class="doccomment">/// A block in a linked list.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Each block in the list can hold up to `BLOCK_CAP` messages.</span>
<span class="kw">struct</span> <span class="ident">Block</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// The next block in the linked list.</span>
<span class="ident">next</span>: <span class="ident">AtomicPtr</span><span class="op"><</span><span class="ident">Block</span><span class="op"><</span><span class="ident">T</span><span class="op">></span><span class="op">></span>,
<span class="doccomment">/// Slots for messages.</span>
<span class="ident">slots</span>: [<span class="ident">Slot</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>; <span class="ident">BLOCK_CAP</span>],
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Block</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Creates an empty block.</span>
<span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-</span><span class="op">></span> <span class="ident">Block</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">// SAFETY: This is safe because:</span>
<span class="comment">// [1] `Block::next` (AtomicPtr) may be safely zero initialized.</span>
<span class="comment">// [2] `Block::slots` (Array) may be safely zero initialized because of [3, 4].</span>
<span class="comment">// [3] `Slot::msg` (UnsafeCell) may be safely zero initialized because it</span>
<span class="comment">// holds a MaybeUninit.</span>
<span class="comment">// [4] `Slot::state` (AtomicUsize) may be safely zero initialized.</span>
<span class="kw">unsafe</span> { <span class="ident">MaybeUninit::zeroed</span>().<span class="ident">assume_init</span>() }
}
<span class="doccomment">/// Waits until the next pointer is set.</span>
<span class="kw">fn</span> <span class="ident">wait_next</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">Block</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">backoff</span> <span class="op">=</span> <span class="ident">Backoff::new</span>();
<span class="kw">loop</span> {
<span class="kw">let</span> <span class="ident">next</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">next</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="kw">if</span> <span class="op">!</span><span class="ident">next</span>.<span class="ident">is_null</span>() {
<span class="kw">return</span> <span class="ident">next</span>;
}
<span class="ident">backoff</span>.<span class="ident">snooze</span>();
}
}
<span class="doccomment">/// Sets the `DESTROY` bit in slots starting from `start` and destroys the block.</span>
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">destroy</span>(<span class="ident">this</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">Block</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>, <span class="ident">start</span>: <span class="ident">usize</span>) {
<span class="comment">// It is not necessary to set the `DESTROY` bit in the last slot because that slot has</span>
<span class="comment">// begun destruction of the block.</span>
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="ident">start</span>..<span class="ident">BLOCK_CAP</span> <span class="op">-</span> <span class="number">1</span> {
<span class="kw">let</span> <span class="ident">slot</span> <span class="op">=</span> (<span class="kw-2">*</span><span class="ident">this</span>).<span class="ident">slots</span>.<span class="ident">get_unchecked</span>(<span class="ident">i</span>);
<span class="comment">// Mark the `DESTROY` bit if a thread is still using the slot.</span>
<span class="kw">if</span> <span class="ident">slot</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>) <span class="op">&</span> <span class="ident">READ</span> <span class="op">=</span><span class="op">=</span> <span class="number">0</span>
<span class="op">&&</span> <span class="ident">slot</span>.<span class="ident">state</span>.<span class="ident">fetch_or</span>(<span class="ident">DESTROY</span>, <span class="ident">Ordering::AcqRel</span>) <span class="op">&</span> <span class="ident">READ</span> <span class="op">=</span><span class="op">=</span> <span class="number">0</span>
{
<span class="comment">// If a thread is still using the slot, it will continue destruction of the block.</span>
<span class="kw">return</span>;
}
}
<span class="comment">// No thread is using the block, now it is safe to destroy it.</span>
<span class="ident">drop</span>(<span class="ident">Box::from_raw</span>(<span class="ident">this</span>));
}
}
<span class="doccomment">/// A position in a channel.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">struct</span> <span class="ident">Position</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// The index in the channel.</span>
<span class="ident">index</span>: <span class="ident">AtomicUsize</span>,
<span class="doccomment">/// The block in the linked list.</span>
<span class="ident">block</span>: <span class="ident">AtomicPtr</span><span class="op"><</span><span class="ident">Block</span><span class="op"><</span><span class="ident">T</span><span class="op">></span><span class="op">></span>,
}
<span class="doccomment">/// The token type for the list flavor.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">ListToken</span> {
<span class="doccomment">/// The block of slots.</span>
<span class="ident">block</span>: <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>,
<span class="doccomment">/// The offset into the block.</span>
<span class="ident">offset</span>: <span class="ident">usize</span>,
}
<span class="kw">impl</span> <span class="ident">Default</span> <span class="kw">for</span> <span class="ident">ListToken</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">default</span>() <span class="op">-</span><span class="op">></span> <span class="self">Self</span> {
<span class="ident">ListToken</span> {
<span class="ident">block</span>: <span class="ident">ptr::null</span>(),
<span class="ident">offset</span>: <span class="number">0</span>,
}
}
}
<span class="doccomment">/// Unbounded channel implemented as a linked list.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Each message sent into the channel is assigned a sequence number, i.e. an index. Indices are</span>
<span class="doccomment">/// represented as numbers of type `usize` and wrap on overflow.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Consecutive messages are grouped into blocks in order to put less pressure on the allocator and</span>
<span class="doccomment">/// improve cache efficiency.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct</span> <span class="ident">Channel</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// The head of the channel.</span>
<span class="ident">head</span>: <span class="ident">CachePadded</span><span class="op"><</span><span class="ident">Position</span><span class="op"><</span><span class="ident">T</span><span class="op">></span><span class="op">></span>,
<span class="doccomment">/// The tail of the channel.</span>
<span class="ident">tail</span>: <span class="ident">CachePadded</span><span class="op"><</span><span class="ident">Position</span><span class="op"><</span><span class="ident">T</span><span class="op">></span><span class="op">></span>,
<span class="doccomment">/// Receivers waiting while the channel is empty and not disconnected.</span>
<span class="ident">receivers</span>: <span class="ident">SyncWaker</span>,
<span class="doccomment">/// Indicates that dropping a `Channel<T>` may drop messages of type `T`.</span>
<span class="ident">_marker</span>: <span class="ident">PhantomData</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Channel</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Creates a new unbounded channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-</span><span class="op">></span> <span class="self">Self</span> {
<span class="ident">Channel</span> {
<span class="ident">head</span>: <span class="ident">CachePadded::new</span>(<span class="ident">Position</span> {
<span class="ident">block</span>: <span class="ident">AtomicPtr::new</span>(<span class="ident">ptr::null_mut</span>()),
<span class="ident">index</span>: <span class="ident">AtomicUsize::new</span>(<span class="number">0</span>),
}),
<span class="ident">tail</span>: <span class="ident">CachePadded::new</span>(<span class="ident">Position</span> {
<span class="ident">block</span>: <span class="ident">AtomicPtr::new</span>(<span class="ident">ptr::null_mut</span>()),
<span class="ident">index</span>: <span class="ident">AtomicUsize::new</span>(<span class="number">0</span>),
}),
<span class="ident">receivers</span>: <span class="ident">SyncWaker::new</span>(),
<span class="ident">_marker</span>: <span class="ident">PhantomData</span>,
}
}
<span class="doccomment">/// Returns a receiver handle to the channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">receiver</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Receiver</span><span class="op"><</span><span class="lifetime">'_</span>, <span class="ident">T</span><span class="op">></span> {
<span class="ident">Receiver</span>(<span class="self">self</span>)
}
<span class="doccomment">/// Returns a sender handle to the channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">sender</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Sender</span><span class="op"><</span><span class="lifetime">'_</span>, <span class="ident">T</span><span class="op">></span> {
<span class="ident">Sender</span>(<span class="self">self</span>)
}
<span class="doccomment">/// Attempts to reserve a slot for sending a message.</span>
<span class="kw">fn</span> <span class="ident">start_send</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">token</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Token</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="kw">let</span> <span class="ident">backoff</span> <span class="op">=</span> <span class="ident">Backoff::new</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">tail</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">block</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">block</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">next_block</span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">loop</span> {
<span class="comment">// Check if the channel is disconnected.</span>
<span class="kw">if</span> <span class="ident">tail</span> <span class="op">&</span> <span class="ident">MARK_BIT</span> <span class="op">!</span><span class="op">=</span> <span class="number">0</span> {
<span class="ident">token</span>.<span class="ident">list</span>.<span class="ident">block</span> <span class="op">=</span> <span class="ident">ptr::null</span>();
<span class="kw">return</span> <span class="bool-val">true</span>;
}
<span class="comment">// Calculate the offset of the index into the block.</span>
<span class="kw">let</span> <span class="ident">offset</span> <span class="op">=</span> (<span class="ident">tail</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span>) <span class="op">%</span> <span class="ident">LAP</span>;
<span class="comment">// If we reached the end of the block, wait until the next one is installed.</span>
<span class="kw">if</span> <span class="ident">offset</span> <span class="op">=</span><span class="op">=</span> <span class="ident">BLOCK_CAP</span> {
<span class="ident">backoff</span>.<span class="ident">snooze</span>();
<span class="ident">tail</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="ident">block</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">block</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="kw">continue</span>;
}
<span class="comment">// If we're going to have to install the next block, allocate it in advance in order to</span>
<span class="comment">// make the wait for other threads as short as possible.</span>
<span class="kw">if</span> <span class="ident">offset</span> <span class="op">+</span> <span class="number">1</span> <span class="op">=</span><span class="op">=</span> <span class="ident">BLOCK_CAP</span> <span class="op">&&</span> <span class="ident">next_block</span>.<span class="ident">is_none</span>() {
<span class="ident">next_block</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">Box::new</span>(<span class="ident">Block</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span><span class="ident">::new</span>()));
}
<span class="comment">// If this is the first message to be sent into the channel, we need to allocate the</span>
<span class="comment">// first block and install it.</span>
<span class="kw">if</span> <span class="ident">block</span>.<span class="ident">is_null</span>() {
<span class="kw">let</span> <span class="ident">new</span> <span class="op">=</span> <span class="ident">Box::into_raw</span>(<span class="ident">Box::new</span>(<span class="ident">Block</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span><span class="ident">::new</span>()));
<span class="kw">if</span> <span class="self">self</span>
.<span class="ident">tail</span>
.<span class="ident">block</span>
.<span class="ident">compare_exchange</span>(<span class="ident">block</span>, <span class="ident">new</span>, <span class="ident">Ordering::Release</span>, <span class="ident">Ordering::Relaxed</span>)
.<span class="ident">is_ok</span>()
{
<span class="self">self</span>.<span class="ident">head</span>.<span class="ident">block</span>.<span class="ident">store</span>(<span class="ident">new</span>, <span class="ident">Ordering::Release</span>);
<span class="ident">block</span> <span class="op">=</span> <span class="ident">new</span>;
} <span class="kw">else</span> {
<span class="ident">next_block</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="prelude-val">Some</span>(<span class="ident">Box::from_raw</span>(<span class="ident">new</span>)) };
<span class="ident">tail</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="ident">block</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">block</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="kw">continue</span>;
}
}
<span class="kw">let</span> <span class="ident">new_tail</span> <span class="op">=</span> <span class="ident">tail</span> <span class="op">+</span> (<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>);
<span class="comment">// Try advancing the tail forward.</span>
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">compare_exchange_weak</span>(
<span class="ident">tail</span>,
<span class="ident">new_tail</span>,
<span class="ident">Ordering::SeqCst</span>,
<span class="ident">Ordering::Acquire</span>,
) {
<span class="prelude-val">Ok</span>(<span class="kw">_</span>) <span class="op">=</span><span class="op">></span> <span class="kw">unsafe</span> {
<span class="comment">// If we've reached the end of the block, install the next one.</span>
<span class="kw">if</span> <span class="ident">offset</span> <span class="op">+</span> <span class="number">1</span> <span class="op">=</span><span class="op">=</span> <span class="ident">BLOCK_CAP</span> {
<span class="kw">let</span> <span class="ident">next_block</span> <span class="op">=</span> <span class="ident">Box::into_raw</span>(<span class="ident">next_block</span>.<span class="ident">unwrap</span>());
<span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">block</span>.<span class="ident">store</span>(<span class="ident">next_block</span>, <span class="ident">Ordering::Release</span>);
<span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">fetch_add</span>(<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>, <span class="ident">Ordering::Release</span>);
(<span class="kw-2">*</span><span class="ident">block</span>).<span class="ident">next</span>.<span class="ident">store</span>(<span class="ident">next_block</span>, <span class="ident">Ordering::Release</span>);
}
<span class="ident">token</span>.<span class="ident">list</span>.<span class="ident">block</span> <span class="op">=</span> <span class="ident">block</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>;
<span class="ident">token</span>.<span class="ident">list</span>.<span class="ident">offset</span> <span class="op">=</span> <span class="ident">offset</span>;
<span class="kw">return</span> <span class="bool-val">true</span>;
},
<span class="prelude-val">Err</span>(<span class="ident">t</span>) <span class="op">=</span><span class="op">></span> {
<span class="ident">tail</span> <span class="op">=</span> <span class="ident">t</span>;
<span class="ident">block</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">block</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="ident">backoff</span>.<span class="ident">spin</span>();
}
}
}
}
<span class="doccomment">/// Writes a message into the channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">write</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">token</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Token</span>, <span class="ident">msg</span>: <span class="ident">T</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">T</span><span class="op">></span> {
<span class="comment">// If there is no slot, the channel is disconnected.</span>
<span class="kw">if</span> <span class="ident">token</span>.<span class="ident">list</span>.<span class="ident">block</span>.<span class="ident">is_null</span>() {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">msg</span>);
}
<span class="comment">// Write the message into the slot.</span>
<span class="kw">let</span> <span class="ident">block</span> <span class="op">=</span> <span class="ident">token</span>.<span class="ident">list</span>.<span class="ident">block</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">Block</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>;
<span class="kw">let</span> <span class="ident">offset</span> <span class="op">=</span> <span class="ident">token</span>.<span class="ident">list</span>.<span class="ident">offset</span>;
<span class="kw">let</span> <span class="ident">slot</span> <span class="op">=</span> (<span class="kw-2">*</span><span class="ident">block</span>).<span class="ident">slots</span>.<span class="ident">get_unchecked</span>(<span class="ident">offset</span>);
<span class="ident">slot</span>.<span class="ident">msg</span>.<span class="ident">get</span>().<span class="ident">write</span>(<span class="ident">MaybeUninit::new</span>(<span class="ident">msg</span>));
<span class="ident">slot</span>.<span class="ident">state</span>.<span class="ident">fetch_or</span>(<span class="ident">WRITE</span>, <span class="ident">Ordering::Release</span>);
<span class="comment">// Wake a sleeping receiver.</span>
<span class="self">self</span>.<span class="ident">receivers</span>.<span class="ident">notify</span>();
<span class="prelude-val">Ok</span>(())
}
<span class="doccomment">/// Attempts to reserve a slot for receiving a message.</span>
<span class="kw">fn</span> <span class="ident">start_recv</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">token</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Token</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="kw">let</span> <span class="ident">backoff</span> <span class="op">=</span> <span class="ident">Backoff::new</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">head</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">block</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">block</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="kw">loop</span> {
<span class="comment">// Calculate the offset of the index into the block.</span>
<span class="kw">let</span> <span class="ident">offset</span> <span class="op">=</span> (<span class="ident">head</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span>) <span class="op">%</span> <span class="ident">LAP</span>;
<span class="comment">// If we reached the end of the block, wait until the next one is installed.</span>
<span class="kw">if</span> <span class="ident">offset</span> <span class="op">=</span><span class="op">=</span> <span class="ident">BLOCK_CAP</span> {
<span class="ident">backoff</span>.<span class="ident">snooze</span>();
<span class="ident">head</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="ident">block</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">block</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="kw">continue</span>;
}
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">new_head</span> <span class="op">=</span> <span class="ident">head</span> <span class="op">+</span> (<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>);
<span class="kw">if</span> <span class="ident">new_head</span> <span class="op">&</span> <span class="ident">MARK_BIT</span> <span class="op">=</span><span class="op">=</span> <span class="number">0</span> {
<span class="ident">atomic::fence</span>(<span class="ident">Ordering::SeqCst</span>);
<span class="kw">let</span> <span class="ident">tail</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::Relaxed</span>);
<span class="comment">// If the tail equals the head, that means the channel is empty.</span>
<span class="kw">if</span> <span class="ident">head</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span> <span class="op">=</span><span class="op">=</span> <span class="ident">tail</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span> {
<span class="comment">// If the channel is disconnected...</span>
<span class="kw">if</span> <span class="ident">tail</span> <span class="op">&</span> <span class="ident">MARK_BIT</span> <span class="op">!</span><span class="op">=</span> <span class="number">0</span> {
<span class="comment">// ...then receive an error.</span>
<span class="ident">token</span>.<span class="ident">list</span>.<span class="ident">block</span> <span class="op">=</span> <span class="ident">ptr::null</span>();
<span class="kw">return</span> <span class="bool-val">true</span>;
} <span class="kw">else</span> {
<span class="comment">// Otherwise, the receive operation is not ready.</span>
<span class="kw">return</span> <span class="bool-val">false</span>;
}
}
<span class="comment">// If head and tail are not in the same block, set `MARK_BIT` in head.</span>
<span class="kw">if</span> (<span class="ident">head</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span>) <span class="op">/</span> <span class="ident">LAP</span> <span class="op">!</span><span class="op">=</span> (<span class="ident">tail</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span>) <span class="op">/</span> <span class="ident">LAP</span> {
<span class="ident">new_head</span> <span class="op">|</span><span class="op">=</span> <span class="ident">MARK_BIT</span>;
}
}
<span class="comment">// The block can be null here only if the first message is being sent into the channel.</span>
<span class="comment">// In that case, just wait until it gets initialized.</span>
<span class="kw">if</span> <span class="ident">block</span>.<span class="ident">is_null</span>() {
<span class="ident">backoff</span>.<span class="ident">snooze</span>();
<span class="ident">head</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="ident">block</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">block</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="kw">continue</span>;
}
<span class="comment">// Try moving the head index forward.</span>
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">index</span>.<span class="ident">compare_exchange_weak</span>(
<span class="ident">head</span>,
<span class="ident">new_head</span>,
<span class="ident">Ordering::SeqCst</span>,
<span class="ident">Ordering::Acquire</span>,
) {
<span class="prelude-val">Ok</span>(<span class="kw">_</span>) <span class="op">=</span><span class="op">></span> <span class="kw">unsafe</span> {
<span class="comment">// If we've reached the end of the block, move to the next one.</span>
<span class="kw">if</span> <span class="ident">offset</span> <span class="op">+</span> <span class="number">1</span> <span class="op">=</span><span class="op">=</span> <span class="ident">BLOCK_CAP</span> {
<span class="kw">let</span> <span class="ident">next</span> <span class="op">=</span> (<span class="kw-2">*</span><span class="ident">block</span>).<span class="ident">wait_next</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">next_index</span> <span class="op">=</span> (<span class="ident">new_head</span> <span class="op">&</span> <span class="op">!</span><span class="ident">MARK_BIT</span>).<span class="ident">wrapping_add</span>(<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>);
<span class="kw">if</span> <span class="op">!</span>(<span class="kw-2">*</span><span class="ident">next</span>).<span class="ident">next</span>.<span class="ident">load</span>(<span class="ident">Ordering::Relaxed</span>).<span class="ident">is_null</span>() {
<span class="ident">next_index</span> <span class="op">|</span><span class="op">=</span> <span class="ident">MARK_BIT</span>;
}
<span class="self">self</span>.<span class="ident">head</span>.<span class="ident">block</span>.<span class="ident">store</span>(<span class="ident">next</span>, <span class="ident">Ordering::Release</span>);
<span class="self">self</span>.<span class="ident">head</span>.<span class="ident">index</span>.<span class="ident">store</span>(<span class="ident">next_index</span>, <span class="ident">Ordering::Release</span>);
}
<span class="ident">token</span>.<span class="ident">list</span>.<span class="ident">block</span> <span class="op">=</span> <span class="ident">block</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>;
<span class="ident">token</span>.<span class="ident">list</span>.<span class="ident">offset</span> <span class="op">=</span> <span class="ident">offset</span>;
<span class="kw">return</span> <span class="bool-val">true</span>;
},
<span class="prelude-val">Err</span>(<span class="ident">h</span>) <span class="op">=</span><span class="op">></span> {
<span class="ident">head</span> <span class="op">=</span> <span class="ident">h</span>;
<span class="ident">block</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">block</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="ident">backoff</span>.<span class="ident">spin</span>();
}
}
}
}
<span class="doccomment">/// Reads a message from the channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">read</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">token</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Token</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, ()<span class="op">></span> {
<span class="kw">if</span> <span class="ident">token</span>.<span class="ident">list</span>.<span class="ident">block</span>.<span class="ident">is_null</span>() {
<span class="comment">// The channel is disconnected.</span>
<span class="kw">return</span> <span class="prelude-val">Err</span>(());
}
<span class="comment">// Read the message.</span>
<span class="kw">let</span> <span class="ident">block</span> <span class="op">=</span> <span class="ident">token</span>.<span class="ident">list</span>.<span class="ident">block</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">Block</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>;
<span class="kw">let</span> <span class="ident">offset</span> <span class="op">=</span> <span class="ident">token</span>.<span class="ident">list</span>.<span class="ident">offset</span>;
<span class="kw">let</span> <span class="ident">slot</span> <span class="op">=</span> (<span class="kw-2">*</span><span class="ident">block</span>).<span class="ident">slots</span>.<span class="ident">get_unchecked</span>(<span class="ident">offset</span>);
<span class="ident">slot</span>.<span class="ident">wait_write</span>();
<span class="kw">let</span> <span class="ident">msg</span> <span class="op">=</span> <span class="ident">slot</span>.<span class="ident">msg</span>.<span class="ident">get</span>().<span class="ident">read</span>().<span class="ident">assume_init</span>();
<span class="comment">// Destroy the block if we've reached the end, or if another thread wanted to destroy but</span>
<span class="comment">// couldn't because we were busy reading from the slot.</span>
<span class="kw">if</span> <span class="ident">offset</span> <span class="op">+</span> <span class="number">1</span> <span class="op">=</span><span class="op">=</span> <span class="ident">BLOCK_CAP</span> {
<span class="ident">Block::destroy</span>(<span class="ident">block</span>, <span class="number">0</span>);
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">slot</span>.<span class="ident">state</span>.<span class="ident">fetch_or</span>(<span class="ident">READ</span>, <span class="ident">Ordering::AcqRel</span>) <span class="op">&</span> <span class="ident">DESTROY</span> <span class="op">!</span><span class="op">=</span> <span class="number">0</span> {
<span class="ident">Block::destroy</span>(<span class="ident">block</span>, <span class="ident">offset</span> <span class="op">+</span> <span class="number">1</span>);
}
<span class="prelude-val">Ok</span>(<span class="ident">msg</span>)
}
<span class="doccomment">/// Attempts to send a message into the channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">try_send</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">msg</span>: <span class="ident">T</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">TrySendError</span><span class="op"><</span><span class="ident">T</span><span class="op">></span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">send</span>(<span class="ident">msg</span>, <span class="prelude-val">None</span>).<span class="ident">map_err</span>(<span class="op">|</span><span class="ident">err</span><span class="op">|</span> <span class="kw">match</span> <span class="ident">err</span> {
<span class="ident">SendTimeoutError::Disconnected</span>(<span class="ident">msg</span>) <span class="op">=</span><span class="op">></span> <span class="ident">TrySendError::Disconnected</span>(<span class="ident">msg</span>),
<span class="ident">SendTimeoutError::Timeout</span>(<span class="kw">_</span>) <span class="op">=</span><span class="op">></span> <span class="macro">unreachable!</span>(),
})
}
<span class="doccomment">/// Sends a message into the channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">send</span>(
<span class="kw-2">&</span><span class="self">self</span>,
<span class="ident">msg</span>: <span class="ident">T</span>,
<span class="ident">_deadline</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Instant</span><span class="op">></span>,
) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">SendTimeoutError</span><span class="op"><</span><span class="ident">T</span><span class="op">></span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">token</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Token::default</span>();
<span class="macro">assert!</span>(<span class="self">self</span>.<span class="ident">start_send</span>(<span class="ident">token</span>));
<span class="kw">unsafe</span> {
<span class="self">self</span>.<span class="ident">write</span>(<span class="ident">token</span>, <span class="ident">msg</span>)
.<span class="ident">map_err</span>(<span class="ident">SendTimeoutError::Disconnected</span>)
}
}
<span class="doccomment">/// Attempts to receive a message without blocking.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">try_recv</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">TryRecvError</span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">token</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Token::default</span>();
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">start_recv</span>(<span class="ident">token</span>) {
<span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">read</span>(<span class="ident">token</span>).<span class="ident">map_err</span>(<span class="op">|</span><span class="kw">_</span><span class="op">|</span> <span class="ident">TryRecvError::Disconnected</span>) }
} <span class="kw">else</span> {
<span class="prelude-val">Err</span>(<span class="ident">TryRecvError::Empty</span>)
}
}
<span class="doccomment">/// Receives a message from the channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">recv</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">deadline</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Instant</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">RecvTimeoutError</span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">token</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Token::default</span>();
<span class="kw">loop</span> {
<span class="comment">// Try receiving a message several times.</span>
<span class="kw">let</span> <span class="ident">backoff</span> <span class="op">=</span> <span class="ident">Backoff::new</span>();
<span class="kw">loop</span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">start_recv</span>(<span class="ident">token</span>) {
<span class="kw">unsafe</span> {
<span class="kw">return</span> <span class="self">self</span>.<span class="ident">read</span>(<span class="ident">token</span>).<span class="ident">map_err</span>(<span class="op">|</span><span class="kw">_</span><span class="op">|</span> <span class="ident">RecvTimeoutError::Disconnected</span>);
}
}
<span class="kw">if</span> <span class="ident">backoff</span>.<span class="ident">is_completed</span>() {
<span class="kw">break</span>;
} <span class="kw">else</span> {
<span class="ident">backoff</span>.<span class="ident">snooze</span>();
}
}
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">d</span>) <span class="op">=</span> <span class="ident">deadline</span> {
<span class="kw">if</span> <span class="ident">Instant::now</span>() <span class="op">></span><span class="op">=</span> <span class="ident">d</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">RecvTimeoutError::Timeout</span>);
}
}
<span class="comment">// Prepare for blocking until a sender wakes us up.</span>
<span class="ident">Context::with</span>(<span class="op">|</span><span class="ident">cx</span><span class="op">|</span> {
<span class="kw">let</span> <span class="ident">oper</span> <span class="op">=</span> <span class="ident">Operation::hook</span>(<span class="ident">token</span>);
<span class="self">self</span>.<span class="ident">receivers</span>.<span class="ident">register</span>(<span class="ident">oper</span>, <span class="ident">cx</span>);
<span class="comment">// Has the channel become ready just now?</span>
<span class="kw">if</span> <span class="op">!</span><span class="self">self</span>.<span class="ident">is_empty</span>() <span class="op">|</span><span class="op">|</span> <span class="self">self</span>.<span class="ident">is_disconnected</span>() {
<span class="kw">let</span> <span class="kw">_</span> <span class="op">=</span> <span class="ident">cx</span>.<span class="ident">try_select</span>(<span class="ident">Selected::Aborted</span>);
}
<span class="comment">// Block the current thread.</span>
<span class="kw">let</span> <span class="ident">sel</span> <span class="op">=</span> <span class="ident">cx</span>.<span class="ident">wait_until</span>(<span class="ident">deadline</span>);
<span class="kw">match</span> <span class="ident">sel</span> {
<span class="ident">Selected::Waiting</span> <span class="op">=</span><span class="op">></span> <span class="macro">unreachable!</span>(),
<span class="ident">Selected::Aborted</span> <span class="op">|</span> <span class="ident">Selected::Disconnected</span> <span class="op">=</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">receivers</span>.<span class="ident">unregister</span>(<span class="ident">oper</span>).<span class="ident">unwrap</span>();
<span class="comment">// If the channel was disconnected, we still have to check for remaining</span>
<span class="comment">// messages.</span>
}
<span class="ident">Selected::Operation</span>(<span class="kw">_</span>) <span class="op">=</span><span class="op">></span> {}
}
});
}
}
<span class="doccomment">/// Returns the current number of messages inside the channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">len</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">usize</span> {
<span class="kw">loop</span> {
<span class="comment">// Load the tail index, then load the head index.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">tail</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::SeqCst</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">head</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::SeqCst</span>);
<span class="comment">// If the tail index didn't change, we've got consistent indices to work with.</span>
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::SeqCst</span>) <span class="op">=</span><span class="op">=</span> <span class="ident">tail</span> {
<span class="comment">// Erase the lower bits.</span>
<span class="ident">tail</span> <span class="op">&=</span> <span class="op">!</span>((<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>) <span class="op">-</span> <span class="number">1</span>);
<span class="ident">head</span> <span class="op">&=</span> <span class="op">!</span>((<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>) <span class="op">-</span> <span class="number">1</span>);
<span class="comment">// Fix up indices if they fall onto block ends.</span>
<span class="kw">if</span> (<span class="ident">tail</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span>) <span class="op">&</span> (<span class="ident">LAP</span> <span class="op">-</span> <span class="number">1</span>) <span class="op">=</span><span class="op">=</span> <span class="ident">LAP</span> <span class="op">-</span> <span class="number">1</span> {
<span class="ident">tail</span> <span class="op">=</span> <span class="ident">tail</span>.<span class="ident">wrapping_add</span>(<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>);
}
<span class="kw">if</span> (<span class="ident">head</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span>) <span class="op">&</span> (<span class="ident">LAP</span> <span class="op">-</span> <span class="number">1</span>) <span class="op">=</span><span class="op">=</span> <span class="ident">LAP</span> <span class="op">-</span> <span class="number">1</span> {
<span class="ident">head</span> <span class="op">=</span> <span class="ident">head</span>.<span class="ident">wrapping_add</span>(<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>);
}
<span class="comment">// Rotate indices so that head falls into the first block.</span>
<span class="kw">let</span> <span class="ident">lap</span> <span class="op">=</span> (<span class="ident">head</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span>) <span class="op">/</span> <span class="ident">LAP</span>;
<span class="ident">tail</span> <span class="op">=</span> <span class="ident">tail</span>.<span class="ident">wrapping_sub</span>((<span class="ident">lap</span> <span class="op">*</span> <span class="ident">LAP</span>) <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>);
<span class="ident">head</span> <span class="op">=</span> <span class="ident">head</span>.<span class="ident">wrapping_sub</span>((<span class="ident">lap</span> <span class="op">*</span> <span class="ident">LAP</span>) <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>);
<span class="comment">// Remove the lower bits.</span>
<span class="ident">tail</span> <span class="op">></span><span class="op">></span><span class="op">=</span> <span class="ident">SHIFT</span>;
<span class="ident">head</span> <span class="op">></span><span class="op">></span><span class="op">=</span> <span class="ident">SHIFT</span>;
<span class="comment">// Return the difference minus the number of blocks between tail and head.</span>
<span class="kw">return</span> <span class="ident">tail</span> <span class="op">-</span> <span class="ident">head</span> <span class="op">-</span> <span class="ident">tail</span> <span class="op">/</span> <span class="ident">LAP</span>;
}
}
}
<span class="doccomment">/// Returns the capacity of the channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">capacity</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span> {
<span class="prelude-val">None</span>
}
<span class="doccomment">/// Disconnects senders and wakes up all blocked receivers.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Returns `true` if this call disconnected the channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">disconnect_senders</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="kw">let</span> <span class="ident">tail</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">fetch_or</span>(<span class="ident">MARK_BIT</span>, <span class="ident">Ordering::SeqCst</span>);
<span class="kw">if</span> <span class="ident">tail</span> <span class="op">&</span> <span class="ident">MARK_BIT</span> <span class="op">=</span><span class="op">=</span> <span class="number">0</span> {
<span class="self">self</span>.<span class="ident">receivers</span>.<span class="ident">disconnect</span>();
<span class="bool-val">true</span>
} <span class="kw">else</span> {
<span class="bool-val">false</span>
}
}
<span class="doccomment">/// Disconnects receivers.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Returns `true` if this call disconnected the channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">disconnect_receivers</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="kw">let</span> <span class="ident">tail</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">fetch_or</span>(<span class="ident">MARK_BIT</span>, <span class="ident">Ordering::SeqCst</span>);
<span class="kw">if</span> <span class="ident">tail</span> <span class="op">&</span> <span class="ident">MARK_BIT</span> <span class="op">=</span><span class="op">=</span> <span class="number">0</span> {
<span class="comment">// If receivers are dropped first, discard all messages to free</span>
<span class="comment">// memory eagerly.</span>
<span class="self">self</span>.<span class="ident">discard_all_messages</span>();
<span class="bool-val">true</span>
} <span class="kw">else</span> {
<span class="bool-val">false</span>
}
}
<span class="doccomment">/// Discards all messages.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This method should only be called when all receivers are dropped.</span>
<span class="kw">fn</span> <span class="ident">discard_all_messages</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">let</span> <span class="ident">backoff</span> <span class="op">=</span> <span class="ident">Backoff::new</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">tail</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="kw">loop</span> {
<span class="kw">let</span> <span class="ident">offset</span> <span class="op">=</span> (<span class="ident">tail</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span>) <span class="op">%</span> <span class="ident">LAP</span>;
<span class="kw">if</span> <span class="ident">offset</span> <span class="op">!</span><span class="op">=</span> <span class="ident">BLOCK_CAP</span> {
<span class="kw">break</span>;
}
<span class="comment">// New updates to tail will be rejected by MARK_BIT and aborted unless it's</span>
<span class="comment">// at boundary. We need to wait for the updates take affect otherwise there</span>
<span class="comment">// can be memory leaks.</span>
<span class="ident">backoff</span>.<span class="ident">snooze</span>();
<span class="ident">tail</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
}
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">head</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">block</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">block</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="kw">unsafe</span> {
<span class="comment">// Drop all messages between head and tail and deallocate the heap-allocated blocks.</span>
<span class="kw">while</span> <span class="ident">head</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span> <span class="op">!</span><span class="op">=</span> <span class="ident">tail</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span> {
<span class="kw">let</span> <span class="ident">offset</span> <span class="op">=</span> (<span class="ident">head</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span>) <span class="op">%</span> <span class="ident">LAP</span>;
<span class="kw">if</span> <span class="ident">offset</span> <span class="op"><</span> <span class="ident">BLOCK_CAP</span> {
<span class="comment">// Drop the message in the slot.</span>
<span class="kw">let</span> <span class="ident">slot</span> <span class="op">=</span> (<span class="kw-2">*</span><span class="ident">block</span>).<span class="ident">slots</span>.<span class="ident">get_unchecked</span>(<span class="ident">offset</span>);
<span class="ident">slot</span>.<span class="ident">wait_write</span>();
<span class="kw">let</span> <span class="ident">p</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">slot</span>.<span class="ident">msg</span>.<span class="ident">get</span>();
<span class="ident">p</span>.<span class="ident">as_mut_ptr</span>().<span class="ident">drop_in_place</span>();
} <span class="kw">else</span> {
(<span class="kw-2">*</span><span class="ident">block</span>).<span class="ident">wait_next</span>();
<span class="comment">// Deallocate the block and move to the next one.</span>
<span class="kw">let</span> <span class="ident">next</span> <span class="op">=</span> (<span class="kw-2">*</span><span class="ident">block</span>).<span class="ident">next</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>);
<span class="ident">drop</span>(<span class="ident">Box::from_raw</span>(<span class="ident">block</span>));
<span class="ident">block</span> <span class="op">=</span> <span class="ident">next</span>;
}
<span class="ident">head</span> <span class="op">=</span> <span class="ident">head</span>.<span class="ident">wrapping_add</span>(<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>);
}
<span class="comment">// Deallocate the last remaining block.</span>
<span class="kw">if</span> <span class="op">!</span><span class="ident">block</span>.<span class="ident">is_null</span>() {
<span class="ident">drop</span>(<span class="ident">Box::from_raw</span>(<span class="ident">block</span>));
}
}
<span class="ident">head</span> <span class="op">&=</span> <span class="op">!</span><span class="ident">MARK_BIT</span>;
<span class="self">self</span>.<span class="ident">head</span>.<span class="ident">block</span>.<span class="ident">store</span>(<span class="ident">ptr::null_mut</span>(), <span class="ident">Ordering::Release</span>);
<span class="self">self</span>.<span class="ident">head</span>.<span class="ident">index</span>.<span class="ident">store</span>(<span class="ident">head</span>, <span class="ident">Ordering::Release</span>);
}
<span class="doccomment">/// Returns `true` if the channel is disconnected.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">is_disconnected</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::SeqCst</span>) <span class="op">&</span> <span class="ident">MARK_BIT</span> <span class="op">!</span><span class="op">=</span> <span class="number">0</span>
}
<span class="doccomment">/// Returns `true` if the channel is empty.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">is_empty</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="kw">let</span> <span class="ident">head</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::SeqCst</span>);
<span class="kw">let</span> <span class="ident">tail</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::SeqCst</span>);
<span class="ident">head</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span> <span class="op">=</span><span class="op">=</span> <span class="ident">tail</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span>
}
<span class="doccomment">/// Returns `true` if the channel is full.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">is_full</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="bool-val">false</span>
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">Channel</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">head</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::Relaxed</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">tail</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">index</span>.<span class="ident">load</span>(<span class="ident">Ordering::Relaxed</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">block</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">block</span>.<span class="ident">load</span>(<span class="ident">Ordering::Relaxed</span>);
<span class="comment">// Erase the lower bits.</span>
<span class="ident">head</span> <span class="op">&=</span> <span class="op">!</span>((<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>) <span class="op">-</span> <span class="number">1</span>);
<span class="ident">tail</span> <span class="op">&=</span> <span class="op">!</span>((<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>) <span class="op">-</span> <span class="number">1</span>);
<span class="kw">unsafe</span> {
<span class="comment">// Drop all messages between head and tail and deallocate the heap-allocated blocks.</span>
<span class="kw">while</span> <span class="ident">head</span> <span class="op">!</span><span class="op">=</span> <span class="ident">tail</span> {
<span class="kw">let</span> <span class="ident">offset</span> <span class="op">=</span> (<span class="ident">head</span> <span class="op">></span><span class="op">></span> <span class="ident">SHIFT</span>) <span class="op">%</span> <span class="ident">LAP</span>;
<span class="kw">if</span> <span class="ident">offset</span> <span class="op"><</span> <span class="ident">BLOCK_CAP</span> {
<span class="comment">// Drop the message in the slot.</span>
<span class="kw">let</span> <span class="ident">slot</span> <span class="op">=</span> (<span class="kw-2">*</span><span class="ident">block</span>).<span class="ident">slots</span>.<span class="ident">get_unchecked</span>(<span class="ident">offset</span>);
<span class="kw">let</span> <span class="ident">p</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">slot</span>.<span class="ident">msg</span>.<span class="ident">get</span>();
<span class="ident">p</span>.<span class="ident">as_mut_ptr</span>().<span class="ident">drop_in_place</span>();
} <span class="kw">else</span> {
<span class="comment">// Deallocate the block and move to the next one.</span>
<span class="kw">let</span> <span class="ident">next</span> <span class="op">=</span> (<span class="kw-2">*</span><span class="ident">block</span>).<span class="ident">next</span>.<span class="ident">load</span>(<span class="ident">Ordering::Relaxed</span>);
<span class="ident">drop</span>(<span class="ident">Box::from_raw</span>(<span class="ident">block</span>));
<span class="ident">block</span> <span class="op">=</span> <span class="ident">next</span>;
}
<span class="ident">head</span> <span class="op">=</span> <span class="ident">head</span>.<span class="ident">wrapping_add</span>(<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">SHIFT</span>);
}
<span class="comment">// Deallocate the last remaining block.</span>
<span class="kw">if</span> <span class="op">!</span><span class="ident">block</span>.<span class="ident">is_null</span>() {
<span class="ident">drop</span>(<span class="ident">Box::from_raw</span>(<span class="ident">block</span>));
}
}
}
}
<span class="doccomment">/// Receiver handle to a channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct</span> <span class="ident">Receiver</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span>(<span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">Channel</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>);
<span class="doccomment">/// Sender handle to a channel.</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct</span> <span class="ident">Sender</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span>(<span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">Channel</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>);
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">SelectHandle</span> <span class="kw">for</span> <span class="ident">Receiver</span><span class="op"><</span><span class="lifetime">'_</span>, <span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">try_select</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">token</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Token</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">start_recv</span>(<span class="ident">token</span>)
}
<span class="kw">fn</span> <span class="ident">deadline</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Instant</span><span class="op">></span> {
<span class="prelude-val">None</span>
}
<span class="kw">fn</span> <span class="ident">register</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">oper</span>: <span class="ident">Operation</span>, <span class="ident">cx</span>: <span class="kw-2">&</span><span class="ident">Context</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">receivers</span>.<span class="ident">register</span>(<span class="ident">oper</span>, <span class="ident">cx</span>);
<span class="self">self</span>.<span class="ident">is_ready</span>()
}
<span class="kw">fn</span> <span class="ident">unregister</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">oper</span>: <span class="ident">Operation</span>) {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">receivers</span>.<span class="ident">unregister</span>(<span class="ident">oper</span>);
}
<span class="kw">fn</span> <span class="ident">accept</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">token</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Token</span>, <span class="ident">_cx</span>: <span class="kw-2">&</span><span class="ident">Context</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">try_select</span>(<span class="ident">token</span>)
}
<span class="kw">fn</span> <span class="ident">is_ready</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="op">!</span><span class="self">self</span>.<span class="number">0</span>.<span class="ident">is_empty</span>() <span class="op">|</span><span class="op">|</span> <span class="self">self</span>.<span class="number">0</span>.<span class="ident">is_disconnected</span>()
}
<span class="kw">fn</span> <span class="ident">watch</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">oper</span>: <span class="ident">Operation</span>, <span class="ident">cx</span>: <span class="kw-2">&</span><span class="ident">Context</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">receivers</span>.<span class="ident">watch</span>(<span class="ident">oper</span>, <span class="ident">cx</span>);
<span class="self">self</span>.<span class="ident">is_ready</span>()
}
<span class="kw">fn</span> <span class="ident">unwatch</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">oper</span>: <span class="ident">Operation</span>) {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">receivers</span>.<span class="ident">unwatch</span>(<span class="ident">oper</span>);
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">SelectHandle</span> <span class="kw">for</span> <span class="ident">Sender</span><span class="op"><</span><span class="lifetime">'_</span>, <span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">try_select</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">token</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Token</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">start_send</span>(<span class="ident">token</span>)
}
<span class="kw">fn</span> <span class="ident">deadline</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Instant</span><span class="op">></span> {
<span class="prelude-val">None</span>
}
<span class="kw">fn</span> <span class="ident">register</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">_oper</span>: <span class="ident">Operation</span>, <span class="ident">_cx</span>: <span class="kw-2">&</span><span class="ident">Context</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">is_ready</span>()
}
<span class="kw">fn</span> <span class="ident">unregister</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">_oper</span>: <span class="ident">Operation</span>) {}
<span class="kw">fn</span> <span class="ident">accept</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">token</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Token</span>, <span class="ident">_cx</span>: <span class="kw-2">&</span><span class="ident">Context</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">try_select</span>(<span class="ident">token</span>)
}
<span class="kw">fn</span> <span class="ident">is_ready</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="bool-val">true</span>
}
<span class="kw">fn</span> <span class="ident">watch</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">_oper</span>: <span class="ident">Operation</span>, <span class="ident">_cx</span>: <span class="kw-2">&</span><span class="ident">Context</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">is_ready</span>()
}
<span class="kw">fn</span> <span class="ident">unwatch</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">_oper</span>: <span class="ident">Operation</span>) {}
}
</pre></div>
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