<!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 to the Rust file `libstd/sync/mpsc/sync.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>sync.rs.html -- 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="../../../../dark.css"><link rel="stylesheet" type="text/css" href="../../../../light.css" id="themeStyle"><script src="../../../../storage.js"></script><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc source"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../../../std/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../../../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../../../../settings.html"><img src="../../../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><pre class="line-numbers"><span id="1"> 1</span>
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</pre><pre class="rust ">
<span class="comment">// Copyright 2014 The Rust Project Developers. See the COPYRIGHT</span>
<span class="comment">// file at the top-level directory of this distribution and at</span>
<span class="comment">// http://rust-lang.org/COPYRIGHT.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span>
<span class="comment">// option. This file may not be copied, modified, or distributed</span>
<span class="comment">// except according to those terms.</span>
<span class="doccomment">/// Synchronous channels/ports</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This channel implementation differs significantly from the asynchronous</span>
<span class="doccomment">/// implementations found next to it (oneshot/stream/share). This is an</span>
<span class="doccomment">/// implementation of a synchronous, bounded buffer channel.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Each channel is created with some amount of backing buffer, and sends will</span>
<span class="doccomment">/// *block* until buffer space becomes available. A buffer size of 0 is valid,</span>
<span class="doccomment">/// which means that every successful send is paired with a successful recv.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This flavor of channels defines a new `send_opt` method for channels which</span>
<span class="doccomment">/// is the method by which a message is sent but the thread does not panic if it</span>
<span class="doccomment">/// cannot be delivered.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Another major difference is that send() will *always* return back the data</span>
<span class="doccomment">/// if it couldn't be sent. This is because it is deterministically known when</span>
<span class="doccomment">/// the data is received and when it is not received.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Implementation-wise, it can all be summed up with "use a mutex plus some</span>
<span class="doccomment">/// logic". The mutex used here is an OS native mutex, meaning that no user code</span>
<span class="doccomment">/// is run inside of the mutex (to prevent context switching). This</span>
<span class="doccomment">/// implementation shares almost all code for the buffered and unbuffered cases</span>
<span class="doccomment">/// of a synchronous channel. There are a few branches for the unbuffered case,</span>
<span class="doccomment">/// but they're mostly just relevant to blocking senders.</span>
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">Failure</span>::<span class="kw-2">*</span>;
<span class="kw">use</span> <span class="self">self</span>::<span class="ident">Blocker</span>::<span class="kw-2">*</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">intrinsics</span>::<span class="ident">abort</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">isize</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">mem</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">ptr</span>;
<span class="kw">use</span> <span class="ident">sync</span>::<span class="ident">atomic</span>::{<span class="ident">Ordering</span>, <span class="ident">AtomicUsize</span>};
<span class="kw">use</span> <span class="ident">sync</span>::<span class="ident">mpsc</span>::<span class="ident">blocking</span>::{<span class="self">self</span>, <span class="ident">WaitToken</span>, <span class="ident">SignalToken</span>};
<span class="kw">use</span> <span class="ident">sync</span>::<span class="ident">mpsc</span>::<span class="ident">select</span>::<span class="ident">StartResult</span>::{<span class="self">self</span>, <span class="ident">Installed</span>, <span class="ident">Abort</span>};
<span class="kw">use</span> <span class="ident">sync</span>::{<span class="ident">Mutex</span>, <span class="ident">MutexGuard</span>};
<span class="kw">use</span> <span class="ident">time</span>::<span class="ident">Instant</span>;
<span class="kw">const</span> <span class="ident">MAX_REFCOUNT</span>: <span class="ident">usize</span> <span class="op">=</span> (<span class="ident">isize</span>::<span class="ident">MAX</span>) <span class="kw">as</span> <span class="ident">usize</span>;
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Packet</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Only field outside of the mutex. Just done for kicks, but mainly because</span>
<span class="doccomment">/// the other shared channel already had the code implemented</span>
<span class="ident">channels</span>: <span class="ident">AtomicUsize</span>,
<span class="ident">lock</span>: <span class="ident">Mutex</span><span class="op"><</span><span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>,
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Send</span><span class="op">></span> <span class="ident">Send</span> <span class="kw">for</span> <span class="ident">Packet</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { }
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Send</span><span class="op">></span> <span class="ident">Sync</span> <span class="kw">for</span> <span class="ident">Packet</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { }
<span class="kw">struct</span> <span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">disconnected</span>: <span class="ident">bool</span>, <span class="comment">// Is the channel disconnected yet?</span>
<span class="ident">queue</span>: <span class="ident">Queue</span>, <span class="comment">// queue of senders waiting to send data</span>
<span class="ident">blocker</span>: <span class="ident">Blocker</span>, <span class="comment">// currently blocked thread on this channel</span>
<span class="ident">buf</span>: <span class="ident">Buffer</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>, <span class="comment">// storage for buffered messages</span>
<span class="ident">cap</span>: <span class="ident">usize</span>, <span class="comment">// capacity of this channel</span>
<span class="doccomment">/// A curious flag used to indicate whether a sender failed or succeeded in</span>
<span class="doccomment">/// blocking. This is used to transmit information back to the thread that it</span>
<span class="doccomment">/// must dequeue its message from the buffer because it was not received.</span>
<span class="doccomment">/// This is only relevant in the 0-buffer case. This obviously cannot be</span>
<span class="doccomment">/// safely constructed, but it's guaranteed to always have a valid pointer</span>
<span class="doccomment">/// value.</span>
<span class="ident">canceled</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'static</span> <span class="kw-2">mut</span> <span class="ident">bool</span><span class="op">></span>,
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Send</span><span class="op">></span> <span class="ident">Send</span> <span class="kw">for</span> <span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="doccomment">/// Possible flavors of threads who can be blocked on this channel.</span>
<span class="kw">enum</span> <span class="ident">Blocker</span> {
<span class="ident">BlockedSender</span>(<span class="ident">SignalToken</span>),
<span class="ident">BlockedReceiver</span>(<span class="ident">SignalToken</span>),
<span class="ident">NoneBlocked</span>
}
<span class="doccomment">/// Simple queue for threading threads together. Nodes are stack-allocated, so</span>
<span class="doccomment">/// this structure is not safe at all</span>
<span class="kw">struct</span> <span class="ident">Queue</span> {
<span class="ident">head</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">Node</span>,
<span class="ident">tail</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">Node</span>,
}
<span class="kw">struct</span> <span class="ident">Node</span> {
<span class="ident">token</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">SignalToken</span><span class="op">></span>,
<span class="ident">next</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">Node</span>,
}
<span class="kw">unsafe</span> <span class="kw">impl</span> <span class="ident">Send</span> <span class="kw">for</span> <span class="ident">Node</span> {}
<span class="doccomment">/// A simple ring-buffer</span>
<span class="kw">struct</span> <span class="ident">Buffer</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">buf</span>: <span class="ident">Vec</span><span class="op"><</span><span class="prelude-ty">Option</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="ident">size</span>: <span class="ident">usize</span>,
}
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">Failure</span> {
<span class="ident">Empty</span>,
<span class="ident">Disconnected</span>,
}
<span class="doccomment">/// Atomically blocks the current thread, placing it into `slot`, unlocking `lock`</span>
<span class="doccomment">/// in the meantime. This re-locks the mutex upon returning.</span>
<span class="kw">fn</span> <span class="ident">wait</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span>, <span class="ident">T</span><span class="op">></span>(<span class="ident">lock</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">Mutex</span><span class="op"><</span><span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>,
<span class="kw-2">mut</span> <span class="ident">guard</span>: <span class="ident">MutexGuard</span><span class="op"><</span><span class="lifetime">'b</span>, <span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>,
<span class="ident">f</span>: <span class="kw">fn</span>(<span class="ident">SignalToken</span>) <span class="op">-></span> <span class="ident">Blocker</span>)
<span class="op">-></span> <span class="ident">MutexGuard</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>
{
<span class="kw">let</span> (<span class="ident">wait_token</span>, <span class="ident">signal_token</span>) <span class="op">=</span> <span class="ident">blocking</span>::<span class="ident">tokens</span>();
<span class="kw">match</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</span>.<span class="ident">blocker</span>, <span class="ident">f</span>(<span class="ident">signal_token</span>)) {
<span class="ident">NoneBlocked</span> <span class="op">=></span> {}
<span class="kw">_</span> <span class="op">=></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
}
<span class="ident">drop</span>(<span class="ident">guard</span>); <span class="comment">// unlock</span>
<span class="ident">wait_token</span>.<span class="ident">wait</span>(); <span class="comment">// block</span>
<span class="ident">lock</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>() <span class="comment">// relock</span>
}
<span class="doccomment">/// Same as wait, but waiting at most until `deadline`.</span>
<span class="kw">fn</span> <span class="ident">wait_timeout_receiver</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span>, <span class="ident">T</span><span class="op">></span>(<span class="ident">lock</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">Mutex</span><span class="op"><</span><span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>,
<span class="ident">deadline</span>: <span class="ident">Instant</span>,
<span class="kw-2">mut</span> <span class="ident">guard</span>: <span class="ident">MutexGuard</span><span class="op"><</span><span class="lifetime">'b</span>, <span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>,
<span class="ident">success</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">bool</span>)
<span class="op">-></span> <span class="ident">MutexGuard</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>
{
<span class="kw">let</span> (<span class="ident">wait_token</span>, <span class="ident">signal_token</span>) <span class="op">=</span> <span class="ident">blocking</span>::<span class="ident">tokens</span>();
<span class="kw">match</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</span>.<span class="ident">blocker</span>, <span class="ident">BlockedReceiver</span>(<span class="ident">signal_token</span>)) {
<span class="ident">NoneBlocked</span> <span class="op">=></span> {}
<span class="kw">_</span> <span class="op">=></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
}
<span class="ident">drop</span>(<span class="ident">guard</span>); <span class="comment">// unlock</span>
<span class="kw-2">*</span><span class="ident">success</span> <span class="op">=</span> <span class="ident">wait_token</span>.<span class="ident">wait_max_until</span>(<span class="ident">deadline</span>); <span class="comment">// block</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">new_guard</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>(); <span class="comment">// relock</span>
<span class="kw">if</span> <span class="op">!</span><span class="kw-2">*</span><span class="ident">success</span> {
<span class="ident">abort_selection</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">new_guard</span>);
}
<span class="ident">new_guard</span>
}
<span class="kw">fn</span> <span class="ident">abort_selection</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span>(<span class="ident">guard</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">MutexGuard</span><span class="op"><</span><span class="lifetime">'a</span> , <span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw">match</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</span>.<span class="ident">blocker</span>, <span class="ident">NoneBlocked</span>) {
<span class="ident">NoneBlocked</span> <span class="op">=></span> <span class="bool-val">true</span>,
<span class="ident">BlockedSender</span>(<span class="ident">token</span>) <span class="op">=></span> {
<span class="ident">guard</span>.<span class="ident">blocker</span> <span class="op">=</span> <span class="ident">BlockedSender</span>(<span class="ident">token</span>);
<span class="bool-val">true</span>
}
<span class="ident">BlockedReceiver</span>(<span class="ident">token</span>) <span class="op">=></span> { <span class="ident">drop</span>(<span class="ident">token</span>); <span class="bool-val">false</span> }
}
}
<span class="doccomment">/// Wakes up a thread, dropping the lock at the correct time</span>
<span class="kw">fn</span> <span class="ident">wakeup</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">token</span>: <span class="ident">SignalToken</span>, <span class="ident">guard</span>: <span class="ident">MutexGuard</span><span class="op"><</span><span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>) {
<span class="comment">// We need to be careful to wake up the waiting thread *outside* of the mutex</span>
<span class="comment">// in case it incurs a context switch.</span>
<span class="ident">drop</span>(<span class="ident">guard</span>);
<span class="ident">token</span>.<span class="ident">signal</span>();
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Packet</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">cap</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="ident">Packet</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">Packet</span> {
<span class="ident">channels</span>: <span class="ident">AtomicUsize</span>::<span class="ident">new</span>(<span class="number">1</span>),
<span class="ident">lock</span>: <span class="ident">Mutex</span>::<span class="ident">new</span>(<span class="ident">State</span> {
<span class="ident">disconnected</span>: <span class="bool-val">false</span>,
<span class="ident">blocker</span>: <span class="ident">NoneBlocked</span>,
<span class="ident">cap</span>,
<span class="ident">canceled</span>: <span class="prelude-val">None</span>,
<span class="ident">queue</span>: <span class="ident">Queue</span> {
<span class="ident">head</span>: <span class="ident">ptr</span>::<span class="ident">null_mut</span>(),
<span class="ident">tail</span>: <span class="ident">ptr</span>::<span class="ident">null_mut</span>(),
},
<span class="ident">buf</span>: <span class="ident">Buffer</span> {
<span class="ident">buf</span>: (<span class="number">0</span>..<span class="ident">cap</span> <span class="op">+</span> <span class="kw">if</span> <span class="ident">cap</span> <span class="op">==</span> <span class="number">0</span> {<span class="number">1</span>} <span class="kw">else</span> {<span class="number">0</span>}).<span class="ident">map</span>(<span class="op">|</span><span class="kw">_</span><span class="op">|</span> <span class="prelude-val">None</span>).<span class="ident">collect</span>(),
<span class="ident">start</span>: <span class="number">0</span>,
<span class="ident">size</span>: <span class="number">0</span>,
},
}),
}
}
<span class="comment">// wait until a send slot is available, returning locked access to</span>
<span class="comment">// the channel state.</span>
<span class="kw">fn</span> <span class="ident">acquire_send_slot</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">MutexGuard</span><span class="op"><</span><span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">node</span> <span class="op">=</span> <span class="ident">Node</span> { <span class="ident">token</span>: <span class="prelude-val">None</span>, <span class="ident">next</span>: <span class="ident">ptr</span>::<span class="ident">null_mut</span>() };
<span class="kw">loop</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="comment">// are we ready to go?</span>
<span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">disconnected</span> <span class="op">||</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">size</span>() <span class="op"><</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">cap</span>() {
<span class="kw">return</span> <span class="ident">guard</span>;
}
<span class="comment">// no room; actually block</span>
<span class="kw">let</span> <span class="ident">wait_token</span> <span class="op">=</span> <span class="ident">guard</span>.<span class="ident">queue</span>.<span class="ident">enqueue</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">node</span>);
<span class="ident">drop</span>(<span class="ident">guard</span>);
<span class="ident">wait_token</span>.<span class="ident">wait</span>();
}
}
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">send</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">t</span>: <span class="ident">T</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">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">acquire_send_slot</span>();
<span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">disconnected</span> { <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">t</span>) }
<span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">enqueue</span>(<span class="ident">t</span>);
<span class="kw">match</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</span>.<span class="ident">blocker</span>, <span class="ident">NoneBlocked</span>) {
<span class="comment">// if our capacity is 0, then we need to wait for a receiver to be</span>
<span class="comment">// available to take our data. After waiting, we check again to make</span>
<span class="comment">// sure the port didn't go away in the meantime. If it did, we need</span>
<span class="comment">// to hand back our data.</span>
<span class="ident">NoneBlocked</span> <span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">cap</span> <span class="op">==</span> <span class="number">0</span> <span class="op">=></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">canceled</span> <span class="op">=</span> <span class="bool-val">false</span>;
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">guard</span>.<span class="ident">canceled</span>.<span class="ident">is_none</span>());
<span class="ident">guard</span>.<span class="ident">canceled</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="kw">unsafe</span> { <span class="ident">mem</span>::<span class="ident">transmute</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">canceled</span>) });
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="ident">wait</span>(<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">lock</span>, <span class="ident">guard</span>, <span class="ident">BlockedSender</span>);
<span class="kw">if</span> <span class="ident">canceled</span> {<span class="prelude-val">Err</span>(<span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">dequeue</span>())} <span class="kw">else</span> {<span class="prelude-val">Ok</span>(())}
}
<span class="comment">// success, we buffered some data</span>
<span class="ident">NoneBlocked</span> <span class="op">=></span> <span class="prelude-val">Ok</span>(()),
<span class="comment">// success, someone's about to receive our buffered data.</span>
<span class="ident">BlockedReceiver</span>(<span class="ident">token</span>) <span class="op">=></span> { <span class="ident">wakeup</span>(<span class="ident">token</span>, <span class="ident">guard</span>); <span class="prelude-val">Ok</span>(()) }
<span class="ident">BlockedSender</span>(..) <span class="op">=></span> <span class="macro">panic</span><span class="macro">!</span>(<span class="string">"lolwut"</span>),
}
}
<span class="kw">pub</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">t</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="kw">super</span>::<span class="ident">TrySendError</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">disconnected</span> {
<span class="prelude-val">Err</span>(<span class="kw">super</span>::<span class="ident">TrySendError</span>::<span class="ident">Disconnected</span>(<span class="ident">t</span>))
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">size</span>() <span class="op">==</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">cap</span>() {
<span class="prelude-val">Err</span>(<span class="kw">super</span>::<span class="ident">TrySendError</span>::<span class="ident">Full</span>(<span class="ident">t</span>))
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">cap</span> <span class="op">==</span> <span class="number">0</span> {
<span class="comment">// With capacity 0, even though we have buffer space we can't</span>
<span class="comment">// transfer the data unless there's a receiver waiting.</span>
<span class="kw">match</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</span>.<span class="ident">blocker</span>, <span class="ident">NoneBlocked</span>) {
<span class="ident">NoneBlocked</span> <span class="op">=></span> <span class="prelude-val">Err</span>(<span class="kw">super</span>::<span class="ident">TrySendError</span>::<span class="ident">Full</span>(<span class="ident">t</span>)),
<span class="ident">BlockedSender</span>(..) <span class="op">=></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
<span class="ident">BlockedReceiver</span>(<span class="ident">token</span>) <span class="op">=></span> {
<span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">enqueue</span>(<span class="ident">t</span>);
<span class="ident">wakeup</span>(<span class="ident">token</span>, <span class="ident">guard</span>);
<span class="prelude-val">Ok</span>(())
}
}
} <span class="kw">else</span> {
<span class="comment">// If the buffer has some space and the capacity isn't 0, then we</span>
<span class="comment">// just enqueue the data for later retrieval, ensuring to wake up</span>
<span class="comment">// any blocked receiver if there is one.</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">size</span>() <span class="op"><</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">cap</span>());
<span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">enqueue</span>(<span class="ident">t</span>);
<span class="kw">match</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</span>.<span class="ident">blocker</span>, <span class="ident">NoneBlocked</span>) {
<span class="ident">BlockedReceiver</span>(<span class="ident">token</span>) <span class="op">=></span> <span class="ident">wakeup</span>(<span class="ident">token</span>, <span class="ident">guard</span>),
<span class="ident">NoneBlocked</span> <span class="op">=></span> {}
<span class="ident">BlockedSender</span>(..) <span class="op">=></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
}
<span class="prelude-val">Ok</span>(())
}
}
<span class="comment">// Receives a message from this channel</span>
<span class="comment">//</span>
<span class="comment">// When reading this, remember that there can only ever be one receiver at</span>
<span class="comment">// time.</span>
<span class="kw">pub</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="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">Failure</span><span class="op">></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">woke_up_after_waiting</span> <span class="op">=</span> <span class="bool-val">false</span>;
<span class="comment">// Wait for the buffer to have something in it. No need for a</span>
<span class="comment">// while loop because we're the only receiver.</span>
<span class="kw">if</span> <span class="op">!</span><span class="ident">guard</span>.<span class="ident">disconnected</span> <span class="op">&&</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">size</span>() <span class="op">==</span> <span class="number">0</span> {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">deadline</span>) <span class="op">=</span> <span class="ident">deadline</span> {
<span class="ident">guard</span> <span class="op">=</span> <span class="ident">wait_timeout_receiver</span>(<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">lock</span>,
<span class="ident">deadline</span>,
<span class="ident">guard</span>,
<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">woke_up_after_waiting</span>);
} <span class="kw">else</span> {
<span class="ident">guard</span> <span class="op">=</span> <span class="ident">wait</span>(<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">lock</span>, <span class="ident">guard</span>, <span class="ident">BlockedReceiver</span>);
<span class="ident">woke_up_after_waiting</span> <span class="op">=</span> <span class="bool-val">true</span>;
}
}
<span class="comment">// NB: Channel could be disconnected while waiting, so the order of</span>
<span class="comment">// these conditionals is important.</span>
<span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">disconnected</span> <span class="op">&&</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">size</span>() <span class="op">==</span> <span class="number">0</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">Disconnected</span>);
}
<span class="comment">// Pick up the data, wake up our neighbors, and carry on</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">size</span>() <span class="op">></span> <span class="number">0</span> <span class="op">||</span> (<span class="ident">deadline</span>.<span class="ident">is_some</span>() <span class="op">&&</span> <span class="op">!</span><span class="ident">woke_up_after_waiting</span>));
<span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">size</span>() <span class="op">==</span> <span class="number">0</span> { <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">Empty</span>); }
<span class="kw">let</span> <span class="ident">ret</span> <span class="op">=</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">dequeue</span>();
<span class="self">self</span>.<span class="ident">wakeup_senders</span>(<span class="ident">woke_up_after_waiting</span>, <span class="ident">guard</span>);
<span class="prelude-val">Ok</span>(<span class="ident">ret</span>)
}
<span class="kw">pub</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="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">Failure</span><span class="op">></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="comment">// Easy cases first</span>
<span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">disconnected</span> <span class="op">&&</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">size</span>() <span class="op">==</span> <span class="number">0</span> { <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">Disconnected</span>) }
<span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">size</span>() <span class="op">==</span> <span class="number">0</span> { <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">Empty</span>) }
<span class="comment">// Be sure to wake up neighbors</span>
<span class="kw">let</span> <span class="ident">ret</span> <span class="op">=</span> <span class="prelude-val">Ok</span>(<span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">dequeue</span>());
<span class="self">self</span>.<span class="ident">wakeup_senders</span>(<span class="bool-val">false</span>, <span class="ident">guard</span>);
<span class="ident">ret</span>
}
<span class="comment">// Wake up pending senders after some data has been received</span>
<span class="comment">//</span>
<span class="comment">// * `waited` - flag if the receiver blocked to receive some data, or if it</span>
<span class="comment">// just picked up some data on the way out</span>
<span class="comment">// * `guard` - the lock guard that is held over this channel's lock</span>
<span class="kw">fn</span> <span class="ident">wakeup_senders</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">waited</span>: <span class="ident">bool</span>, <span class="kw-2">mut</span> <span class="ident">guard</span>: <span class="ident">MutexGuard</span><span class="op"><</span><span class="ident">State</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>) {
<span class="kw">let</span> <span class="ident">pending_sender1</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">SignalToken</span><span class="op">></span> <span class="op">=</span> <span class="ident">guard</span>.<span class="ident">queue</span>.<span class="ident">dequeue</span>();
<span class="comment">// If this is a no-buffer channel (cap == 0), then if we didn't wait we</span>
<span class="comment">// need to ACK the sender. If we waited, then the sender waking us up</span>
<span class="comment">// was already the ACK.</span>
<span class="kw">let</span> <span class="ident">pending_sender2</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">cap</span> <span class="op">==</span> <span class="number">0</span> <span class="op">&&</span> <span class="op">!</span><span class="ident">waited</span> {
<span class="kw">match</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</span>.<span class="ident">blocker</span>, <span class="ident">NoneBlocked</span>) {
<span class="ident">NoneBlocked</span> <span class="op">=></span> <span class="prelude-val">None</span>,
<span class="ident">BlockedReceiver</span>(..) <span class="op">=></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
<span class="ident">BlockedSender</span>(<span class="ident">token</span>) <span class="op">=></span> {
<span class="ident">guard</span>.<span class="ident">canceled</span>.<span class="ident">take</span>();
<span class="prelude-val">Some</span>(<span class="ident">token</span>)
}
}
} <span class="kw">else</span> {
<span class="prelude-val">None</span>
};
<span class="ident">mem</span>::<span class="ident">drop</span>(<span class="ident">guard</span>);
<span class="comment">// only outside of the lock do we wake up the pending threads</span>
<span class="ident">pending_sender1</span>.<span class="ident">map</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">signal</span>());
<span class="ident">pending_sender2</span>.<span class="ident">map</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">signal</span>());
}
<span class="comment">// Prepares this shared packet for a channel clone, essentially just bumping</span>
<span class="comment">// a refcount.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">clone_chan</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">let</span> <span class="ident">old_count</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">channels</span>.<span class="ident">fetch_add</span>(<span class="number">1</span>, <span class="ident">Ordering</span>::<span class="ident">SeqCst</span>);
<span class="comment">// See comments on Arc::clone() on why we do this (for `mem::forget`).</span>
<span class="kw">if</span> <span class="ident">old_count</span> <span class="op">></span> <span class="ident">MAX_REFCOUNT</span> {
<span class="kw">unsafe</span> {
<span class="ident">abort</span>();
}
}
}
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">drop_chan</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="comment">// Only flag the channel as disconnected if we're the last channel</span>
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">channels</span>.<span class="ident">fetch_sub</span>(<span class="number">1</span>, <span class="ident">Ordering</span>::<span class="ident">SeqCst</span>) {
<span class="number">1</span> <span class="op">=></span> {}
<span class="kw">_</span> <span class="op">=></span> <span class="kw">return</span>
}
<span class="comment">// Not much to do other than wake up a receiver if one's there</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">disconnected</span> { <span class="kw">return</span> }
<span class="ident">guard</span>.<span class="ident">disconnected</span> <span class="op">=</span> <span class="bool-val">true</span>;
<span class="kw">match</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</span>.<span class="ident">blocker</span>, <span class="ident">NoneBlocked</span>) {
<span class="ident">NoneBlocked</span> <span class="op">=></span> {}
<span class="ident">BlockedSender</span>(..) <span class="op">=></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
<span class="ident">BlockedReceiver</span>(<span class="ident">token</span>) <span class="op">=></span> <span class="ident">wakeup</span>(<span class="ident">token</span>, <span class="ident">guard</span>),
}
}
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">drop_port</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">disconnected</span> { <span class="kw">return</span> }
<span class="ident">guard</span>.<span class="ident">disconnected</span> <span class="op">=</span> <span class="bool-val">true</span>;
<span class="comment">// If the capacity is 0, then the sender may want its data back after</span>
<span class="comment">// we're disconnected. Otherwise it's now our responsibility to destroy</span>
<span class="comment">// the buffered data. As with many other portions of this code, this</span>
<span class="comment">// needs to be careful to destroy the data *outside* of the lock to</span>
<span class="comment">// prevent deadlock.</span>
<span class="kw">let</span> <span class="ident">_data</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">cap</span> <span class="op">!=</span> <span class="number">0</span> {
<span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">buf</span>, <span class="ident">Vec</span>::<span class="ident">new</span>())
} <span class="kw">else</span> {
<span class="ident">Vec</span>::<span class="ident">new</span>()
};
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">queue</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</span>.<span class="ident">queue</span>, <span class="ident">Queue</span> {
<span class="ident">head</span>: <span class="ident">ptr</span>::<span class="ident">null_mut</span>(),
<span class="ident">tail</span>: <span class="ident">ptr</span>::<span class="ident">null_mut</span>(),
});
<span class="kw">let</span> <span class="ident">waiter</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</span>.<span class="ident">blocker</span>, <span class="ident">NoneBlocked</span>) {
<span class="ident">NoneBlocked</span> <span class="op">=></span> <span class="prelude-val">None</span>,
<span class="ident">BlockedSender</span>(<span class="ident">token</span>) <span class="op">=></span> {
<span class="kw-2">*</span><span class="ident">guard</span>.<span class="ident">canceled</span>.<span class="ident">take</span>().<span class="ident">unwrap</span>() <span class="op">=</span> <span class="bool-val">true</span>;
<span class="prelude-val">Some</span>(<span class="ident">token</span>)
}
<span class="ident">BlockedReceiver</span>(..) <span class="op">=></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
};
<span class="ident">mem</span>::<span class="ident">drop</span>(<span class="ident">guard</span>);
<span class="kw">while</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">token</span>) <span class="op">=</span> <span class="ident">queue</span>.<span class="ident">dequeue</span>() { <span class="ident">token</span>.<span class="ident">signal</span>(); }
<span class="ident">waiter</span>.<span class="ident">map</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">signal</span>());
}
<span class="comment">////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// select implementation</span>
<span class="comment">////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// If Ok, the value is whether this port has data, if Err, then the upgraded</span>
<span class="comment">// port needs to be checked instead of this one.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">can_recv</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw">let</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="ident">guard</span>.<span class="ident">disconnected</span> <span class="op">||</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">size</span>() <span class="op">></span> <span class="number">0</span>
}
<span class="comment">// Attempts to start selection on this port. This can either succeed or fail</span>
<span class="comment">// because there is data waiting.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">start_selection</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">token</span>: <span class="ident">SignalToken</span>) <span class="op">-></span> <span class="ident">StartResult</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="kw">if</span> <span class="ident">guard</span>.<span class="ident">disconnected</span> <span class="op">||</span> <span class="ident">guard</span>.<span class="ident">buf</span>.<span class="ident">size</span>() <span class="op">></span> <span class="number">0</span> {
<span class="ident">Abort</span>
} <span class="kw">else</span> {
<span class="kw">match</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</span>.<span class="ident">blocker</span>, <span class="ident">BlockedReceiver</span>(<span class="ident">token</span>)) {
<span class="ident">NoneBlocked</span> <span class="op">=></span> {}
<span class="ident">BlockedSender</span>(..) <span class="op">=></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
<span class="ident">BlockedReceiver</span>(..) <span class="op">=></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
}
<span class="ident">Installed</span>
}
}
<span class="comment">// Remove a previous selecting thread from this port. This ensures that the</span>
<span class="comment">// blocked thread will no longer be visible to any other threads.</span>
<span class="comment">//</span>
<span class="comment">// The return value indicates whether there's data on this port.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">abort_selection</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="ident">abort_selection</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">guard</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">Packet</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="macro">assert_eq</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">channels</span>.<span class="ident">load</span>(<span class="ident">Ordering</span>::<span class="ident">SeqCst</span>), <span class="number">0</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">guard</span>.<span class="ident">queue</span>.<span class="ident">dequeue</span>().<span class="ident">is_none</span>());
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">guard</span>.<span class="ident">canceled</span>.<span class="ident">is_none</span>());
}
}
<span class="comment">////////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Buffer, a simple ring buffer backed by Vec<T></span>
<span class="comment">////////////////////////////////////////////////////////////////////////////////</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Buffer</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">enqueue</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">t</span>: <span class="ident">T</span>) {
<span class="kw">let</span> <span class="ident">pos</span> <span class="op">=</span> (<span class="self">self</span>.<span class="ident">start</span> <span class="op">+</span> <span class="self">self</span>.<span class="ident">size</span>) <span class="op">%</span> <span class="self">self</span>.<span class="ident">buf</span>.<span class="ident">len</span>();
<span class="self">self</span>.<span class="ident">size</span> <span class="op">+=</span> <span class="number">1</span>;
<span class="kw">let</span> <span class="ident">prev</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">buf</span>[<span class="ident">pos</span>], <span class="prelude-val">Some</span>(<span class="ident">t</span>));
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">prev</span>.<span class="ident">is_none</span>());
}
<span class="kw">fn</span> <span class="ident">dequeue</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="kw">let</span> <span class="ident">start</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">start</span>;
<span class="self">self</span>.<span class="ident">size</span> <span class="op">-=</span> <span class="number">1</span>;
<span class="self">self</span>.<span class="ident">start</span> <span class="op">=</span> (<span class="self">self</span>.<span class="ident">start</span> <span class="op">+</span> <span class="number">1</span>) <span class="op">%</span> <span class="self">self</span>.<span class="ident">buf</span>.<span class="ident">len</span>();
<span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">buf</span>[<span class="ident">start</span>];
<span class="ident">result</span>.<span class="ident">take</span>().<span class="ident">unwrap</span>()
}
<span class="kw">fn</span> <span class="ident">size</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">usize</span> { <span class="self">self</span>.<span class="ident">size</span> }
<span class="kw">fn</span> <span class="ident">cap</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">usize</span> { <span class="self">self</span>.<span class="ident">buf</span>.<span class="ident">len</span>() }
}
<span class="comment">////////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Queue, a simple queue to enqueue threads with (stack-allocated nodes)</span>
<span class="comment">////////////////////////////////////////////////////////////////////////////////</span>
<span class="kw">impl</span> <span class="ident">Queue</span> {
<span class="kw">fn</span> <span class="ident">enqueue</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">node</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Node</span>) <span class="op">-></span> <span class="ident">WaitToken</span> {
<span class="kw">let</span> (<span class="ident">wait_token</span>, <span class="ident">signal_token</span>) <span class="op">=</span> <span class="ident">blocking</span>::<span class="ident">tokens</span>();
<span class="ident">node</span>.<span class="ident">token</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">signal_token</span>);
<span class="ident">node</span>.<span class="ident">next</span> <span class="op">=</span> <span class="ident">ptr</span>::<span class="ident">null_mut</span>();
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">tail</span>.<span class="ident">is_null</span>() {
<span class="self">self</span>.<span class="ident">head</span> <span class="op">=</span> <span class="ident">node</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">Node</span>;
<span class="self">self</span>.<span class="ident">tail</span> <span class="op">=</span> <span class="ident">node</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">Node</span>;
} <span class="kw">else</span> {
<span class="kw">unsafe</span> {
(<span class="kw-2">*</span><span class="self">self</span>.<span class="ident">tail</span>).<span class="ident">next</span> <span class="op">=</span> <span class="ident">node</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">Node</span>;
<span class="self">self</span>.<span class="ident">tail</span> <span class="op">=</span> <span class="ident">node</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">Node</span>;
}
}
<span class="ident">wait_token</span>
}
<span class="kw">fn</span> <span class="ident">dequeue</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">SignalToken</span><span class="op">></span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">is_null</span>() {
<span class="kw">return</span> <span class="prelude-val">None</span>
}
<span class="kw">let</span> <span class="ident">node</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">head</span>;
<span class="self">self</span>.<span class="ident">head</span> <span class="op">=</span> <span class="kw">unsafe</span> { (<span class="kw-2">*</span><span class="ident">node</span>).<span class="ident">next</span> };
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">head</span>.<span class="ident">is_null</span>() {
<span class="self">self</span>.<span class="ident">tail</span> <span class="op">=</span> <span class="ident">ptr</span>::<span class="ident">null_mut</span>();
}
<span class="kw">unsafe</span> {
(<span class="kw-2">*</span><span class="ident">node</span>).<span class="ident">next</span> <span class="op">=</span> <span class="ident">ptr</span>::<span class="ident">null_mut</span>();
<span class="prelude-val">Some</span>((<span class="kw-2">*</span><span class="ident">node</span>).<span class="ident">token</span>.<span class="ident">take</span>().<span class="ident">unwrap</span>())
}
}
}
</pre>
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