<!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/select.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>select.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">//! Interface to the select mechanism.</span>
<span class="kw">use</span> <span class="ident">std::fmt</span>;
<span class="kw">use</span> <span class="ident">std::marker::PhantomData</span>;
<span class="kw">use</span> <span class="ident">std::mem</span>;
<span class="kw">use</span> <span class="ident">std::time</span>::{<span class="ident">Duration</span>, <span class="ident">Instant</span>};
<span class="kw">use</span> <span class="ident">crossbeam_utils::Backoff</span>;
<span class="kw">use</span> <span class="kw">crate</span><span class="ident">::channel</span>::{<span class="self">self</span>, <span class="ident">Receiver</span>, <span class="ident">Sender</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">ReadyTimeoutError</span>, <span class="ident">TryReadyError</span>};
<span class="kw">use</span> <span class="kw">crate</span><span class="ident">::err</span>::{<span class="ident">RecvError</span>, <span class="ident">SendError</span>};
<span class="kw">use</span> <span class="kw">crate</span><span class="ident">::err</span>::{<span class="ident">SelectTimeoutError</span>, <span class="ident">TrySelectError</span>};
<span class="kw">use</span> <span class="kw">crate</span><span class="ident">::flavors</span>;
<span class="kw">use</span> <span class="kw">crate</span><span class="ident">::utils</span>;
<span class="doccomment">/// Temporary data that gets initialized during select or a blocking operation, and is consumed by</span>
<span class="doccomment">/// `read` or `write`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Each field contains data associated with a specific channel flavor.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>, <span class="ident">Default</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Token</span> {
<span class="kw">pub</span> <span class="ident">at</span>: <span class="ident">flavors::at::AtToken</span>,
<span class="kw">pub</span> <span class="ident">array</span>: <span class="ident">flavors::array::ArrayToken</span>,
<span class="kw">pub</span> <span class="ident">list</span>: <span class="ident">flavors::list::ListToken</span>,
<span class="kw">pub</span> <span class="ident">never</span>: <span class="ident">flavors::never::NeverToken</span>,
<span class="kw">pub</span> <span class="ident">tick</span>: <span class="ident">flavors::tick::TickToken</span>,
<span class="kw">pub</span> <span class="ident">zero</span>: <span class="ident">flavors::zero::ZeroToken</span>,
}
<span class="doccomment">/// Identifier associated with an operation by a specific thread on a specific channel.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>, <span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">PartialEq</span>, <span class="ident">Eq</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Operation</span>(<span class="ident">usize</span>);
<span class="kw">impl</span> <span class="ident">Operation</span> {
<span class="doccomment">/// Creates an operation identifier from a mutable reference.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function essentially just turns the address of the reference into a number. The</span>
<span class="doccomment">/// reference should point to a variable that is specific to the thread and the operation,</span>
<span class="doccomment">/// and is alive for the entire duration of select or blocking operation.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">hook</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">r</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Operation</span> {
<span class="kw">let</span> <span class="ident">val</span> <span class="op">=</span> <span class="ident">r</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span> <span class="kw">as</span> <span class="ident">usize</span>;
<span class="comment">// Make sure that the pointer address doesn't equal the numerical representation of</span>
<span class="comment">// `Selected::{Waiting, Aborted, Disconnected}`.</span>
<span class="macro">assert!</span>(<span class="ident">val</span> <span class="op">></span> <span class="number">2</span>);
<span class="ident">Operation</span>(<span class="ident">val</span>)
}
}
<span class="doccomment">/// Current state of a select or a blocking operation.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>, <span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">PartialEq</span>, <span class="ident">Eq</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">Selected</span> {
<span class="doccomment">/// Still waiting for an operation.</span>
<span class="ident">Waiting</span>,
<span class="doccomment">/// The attempt to block the current thread has been aborted.</span>
<span class="ident">Aborted</span>,
<span class="doccomment">/// An operation became ready because a channel is disconnected.</span>
<span class="ident">Disconnected</span>,
<span class="doccomment">/// An operation became ready because a message can be sent or received.</span>
<span class="ident">Operation</span>(<span class="ident">Operation</span>),
}
<span class="kw">impl</span> <span class="ident">From</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Selected</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">from</span>(<span class="ident">val</span>: <span class="ident">usize</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Selected</span> {
<span class="kw">match</span> <span class="ident">val</span> {
<span class="number">0</span> <span class="op">=</span><span class="op">></span> <span class="ident">Selected::Waiting</span>,
<span class="number">1</span> <span class="op">=</span><span class="op">></span> <span class="ident">Selected::Aborted</span>,
<span class="number">2</span> <span class="op">=</span><span class="op">></span> <span class="ident">Selected::Disconnected</span>,
<span class="ident">oper</span> <span class="op">=</span><span class="op">></span> <span class="ident">Selected::Operation</span>(<span class="ident">Operation</span>(<span class="ident">oper</span>)),
}
}
}
<span class="kw">impl</span> <span class="ident">Into</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Selected</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">into</span>(<span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">usize</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="ident">Selected::Waiting</span> <span class="op">=</span><span class="op">></span> <span class="number">0</span>,
<span class="ident">Selected::Aborted</span> <span class="op">=</span><span class="op">></span> <span class="number">1</span>,
<span class="ident">Selected::Disconnected</span> <span class="op">=</span><span class="op">></span> <span class="number">2</span>,
<span class="ident">Selected::Operation</span>(<span class="ident">Operation</span>(<span class="ident">val</span>)) <span class="op">=</span><span class="op">></span> <span class="ident">val</span>,
}
}
}
<span class="doccomment">/// A receiver or a sender that can participate in select.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This is a handle that assists select in executing an operation, registration, deciding on the</span>
<span class="doccomment">/// appropriate deadline for blocking, etc.</span>
<span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">SelectHandle</span> {
<span class="doccomment">/// Attempts to select an operation and returns `true` on success.</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="doccomment">/// Returns a deadline for an operation, if there is one.</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="doccomment">/// Registers an operation for execution and returns `true` if it is now ready.</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="doccomment">/// Unregisters an operation for execution.</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="doccomment">/// Attempts to select an operation the thread got woken up for and returns `true` on success.</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="doccomment">/// Returns `true` if an operation can be executed without blocking.</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="doccomment">/// Registers an operation for readiness notification and returns `true` if it is now ready.</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="doccomment">/// Unregisters an operation for readiness notification.</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="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">SelectHandle</span><span class="op">></span> <span class="ident">SelectHandle</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="ident">T</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="kw-2">*</span><span class="kw-2">*</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">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="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">deadline</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="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">register</span>(<span class="ident">oper</span>, <span class="ident">cx</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-2">*</span><span class="kw-2">*</span><span class="self">self</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="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">accept</span>(<span class="ident">token</span>, <span class="ident">cx</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="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">is_ready</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="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">watch</span>(<span class="ident">oper</span>, <span class="ident">cx</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="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">unwatch</span>(<span class="ident">oper</span>)
}
}
<span class="doccomment">/// Determines when a select operation should time out.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">Eq</span>, <span class="ident">PartialEq</span>)]</span>
<span class="kw">enum</span> <span class="ident">Timeout</span> {
<span class="doccomment">/// No blocking.</span>
<span class="ident">Now</span>,
<span class="doccomment">/// Block forever.</span>
<span class="ident">Never</span>,
<span class="doccomment">/// Time out after the time instant.</span>
<span class="ident">At</span>(<span class="ident">Instant</span>),
}
<span class="doccomment">/// Runs until one of the operations is selected, potentially blocking the current thread.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Successful receive operations will have to be followed up by `channel::read()` and successful</span>
<span class="doccomment">/// send operations by `channel::write()`.</span>
<span class="kw">fn</span> <span class="ident">run_select</span>(
<span class="ident">handles</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [(<span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">SelectHandle</span>, <span class="ident">usize</span>, <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>)],
<span class="ident">timeout</span>: <span class="ident">Timeout</span>,
) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">Token</span>, <span class="ident">usize</span>, <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>)<span class="op">></span> {
<span class="kw">if</span> <span class="ident">handles</span>.<span class="ident">is_empty</span>() {
<span class="comment">// Wait until the timeout and return.</span>
<span class="kw">match</span> <span class="ident">timeout</span> {
<span class="ident">Timeout::Now</span> <span class="op">=</span><span class="op">></span> <span class="kw">return</span> <span class="prelude-val">None</span>,
<span class="ident">Timeout::Never</span> <span class="op">=</span><span class="op">></span> {
<span class="ident">utils::sleep_until</span>(<span class="prelude-val">None</span>);
<span class="macro">unreachable!</span>();
}
<span class="ident">Timeout::At</span>(<span class="ident">when</span>) <span class="op">=</span><span class="op">></span> {
<span class="ident">utils::sleep_until</span>(<span class="prelude-val">Some</span>(<span class="ident">when</span>));
<span class="kw">return</span> <span class="prelude-val">None</span>;
}
}
}
<span class="comment">// Shuffle the operations for fairness.</span>
<span class="ident">utils::shuffle</span>(<span class="ident">handles</span>);
<span class="comment">// Create a token, which serves as a temporary variable that gets initialized in this function</span>
<span class="comment">// and is later used by a call to `channel::read()` or `channel::write()` that completes the</span>
<span class="comment">// selected operation.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">token</span> <span class="op">=</span> <span class="ident">Token::default</span>();
<span class="comment">// Try selecting one of the operations without blocking.</span>
<span class="kw">for</span> <span class="kw-2">&</span>(<span class="ident">handle</span>, <span class="ident">i</span>, <span class="ident">ptr</span>) <span class="kw">in</span> <span class="ident">handles</span>.<span class="ident">iter</span>() {
<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">try_select</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">token</span>) {
<span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">token</span>, <span class="ident">i</span>, <span class="ident">ptr</span>));
}
}
<span class="kw">loop</span> {
<span class="comment">// Prepare for blocking.</span>
<span class="kw">let</span> <span class="ident">res</span> <span class="op">=</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="kw-2">mut</span> <span class="ident">sel</span> <span class="op">=</span> <span class="ident">Selected::Waiting</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">registered_count</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">index_ready</span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">if</span> <span class="kw">let</span> <span class="ident">Timeout::Now</span> <span class="op">=</span> <span class="ident">timeout</span> {
<span class="ident">cx</span>.<span class="ident">try_select</span>(<span class="ident">Selected::Aborted</span>).<span class="ident">unwrap</span>();
}
<span class="comment">// Register all operations.</span>
<span class="kw">for</span> (<span class="ident">handle</span>, <span class="ident">i</span>, <span class="kw">_</span>) <span class="kw">in</span> <span class="ident">handles</span>.<span class="ident">iter_mut</span>() {
<span class="ident">registered_count</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
<span class="comment">// If registration returns `false`, that means the operation has just become ready.</span>
<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">register</span>(<span class="ident">Operation::hook</span>::<span class="op"><</span><span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">SelectHandle</span><span class="op">></span>(<span class="ident">handle</span>), <span class="ident">cx</span>) {
<span class="comment">// Try aborting select.</span>
<span class="ident">sel</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">cx</span>.<span class="ident">try_select</span>(<span class="ident">Selected::Aborted</span>) {
<span class="prelude-val">Ok</span>(()) <span class="op">=</span><span class="op">></span> {
<span class="ident">index_ready</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="kw-2">*</span><span class="ident">i</span>);
<span class="ident">Selected::Aborted</span>
}
<span class="prelude-val">Err</span>(<span class="ident">s</span>) <span class="op">=</span><span class="op">></span> <span class="ident">s</span>,
};
<span class="kw">break</span>;
}
<span class="comment">// If another thread has already selected one of the operations, stop registration.</span>
<span class="ident">sel</span> <span class="op">=</span> <span class="ident">cx</span>.<span class="ident">selected</span>();
<span class="kw">if</span> <span class="ident">sel</span> <span class="op">!</span><span class="op">=</span> <span class="ident">Selected::Waiting</span> {
<span class="kw">break</span>;
}
}
<span class="kw">if</span> <span class="ident">sel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">Selected::Waiting</span> {
<span class="comment">// Check with each operation for how long we're allowed to block, and compute the</span>
<span class="comment">// earliest deadline.</span>
<span class="kw">let</span> <span class="kw-2">mut</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="kw">match</span> <span class="ident">timeout</span> {
<span class="ident">Timeout::Now</span> <span class="op">=</span><span class="op">></span> <span class="kw">return</span> <span class="prelude-val">None</span>,
<span class="ident">Timeout::Never</span> <span class="op">=</span><span class="op">></span> <span class="prelude-val">None</span>,
<span class="ident">Timeout::At</span>(<span class="ident">when</span>) <span class="op">=</span><span class="op">></span> <span class="prelude-val">Some</span>(<span class="ident">when</span>),
};
<span class="kw">for</span> <span class="kw-2">&</span>(<span class="ident">handle</span>, <span class="kw">_</span>, <span class="kw">_</span>) <span class="kw">in</span> <span class="ident">handles</span>.<span class="ident">iter</span>() {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">x</span>) <span class="op">=</span> <span class="ident">handle</span>.<span class="ident">deadline</span>() {
<span class="ident">deadline</span> <span class="op">=</span> <span class="ident">deadline</span>.<span class="ident">map</span>(<span class="op">|</span><span class="ident">y</span><span class="op">|</span> <span class="ident">x</span>.<span class="ident">min</span>(<span class="ident">y</span>)).<span class="ident">or</span>(<span class="prelude-val">Some</span>(<span class="ident">x</span>));
}
}
<span class="comment">// Block the current thread.</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="comment">// Unregister all registered operations.</span>
<span class="kw">for</span> (<span class="ident">handle</span>, <span class="kw">_</span>, <span class="kw">_</span>) <span class="kw">in</span> <span class="ident">handles</span>.<span class="ident">iter_mut</span>().<span class="ident">take</span>(<span class="ident">registered_count</span>) {
<span class="ident">handle</span>.<span class="ident">unregister</span>(<span class="ident">Operation::hook</span>::<span class="op"><</span><span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">SelectHandle</span><span class="op">></span>(<span class="ident">handle</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="op">></span> {
<span class="comment">// If an operation became ready during registration, try selecting it.</span>
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">index_ready</span>) <span class="op">=</span> <span class="ident">index_ready</span> {
<span class="kw">for</span> <span class="kw-2">&</span>(<span class="ident">handle</span>, <span class="ident">i</span>, <span class="ident">ptr</span>) <span class="kw">in</span> <span class="ident">handles</span>.<span class="ident">iter</span>() {
<span class="kw">if</span> <span class="ident">i</span> <span class="op">=</span><span class="op">=</span> <span class="ident">index_ready</span> <span class="op">&&</span> <span class="ident">handle</span>.<span class="ident">try_select</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">token</span>) {
<span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">i</span>, <span class="ident">ptr</span>));
}
}
}
}
<span class="ident">Selected::Disconnected</span> <span class="op">=</span><span class="op">></span> {}
<span class="ident">Selected::Operation</span>(<span class="kw">_</span>) <span class="op">=</span><span class="op">></span> {
<span class="comment">// Find the selected operation.</span>
<span class="kw">for</span> (<span class="ident">handle</span>, <span class="ident">i</span>, <span class="ident">ptr</span>) <span class="kw">in</span> <span class="ident">handles</span>.<span class="ident">iter_mut</span>() {
<span class="comment">// Is this the selected operation?</span>
<span class="kw">if</span> <span class="ident">sel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">Selected::Operation</span>(<span class="ident">Operation::hook</span>::<span class="op"><</span><span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">SelectHandle</span><span class="op">></span>(<span class="ident">handle</span>))
{
<span class="comment">// Try selecting this operation.</span>
<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">accept</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">return</span> <span class="prelude-val">Some</span>((<span class="kw-2">*</span><span class="ident">i</span>, <span class="kw-2">*</span><span class="ident">ptr</span>));
}
}
}
}
}
<span class="prelude-val">None</span>
});
<span class="comment">// Return if an operation was selected.</span>
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>((<span class="ident">i</span>, <span class="ident">ptr</span>)) <span class="op">=</span> <span class="ident">res</span> {
<span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">token</span>, <span class="ident">i</span>, <span class="ident">ptr</span>));
}
<span class="comment">// Try selecting one of the operations without blocking.</span>
<span class="kw">for</span> <span class="kw-2">&</span>(<span class="ident">handle</span>, <span class="ident">i</span>, <span class="ident">ptr</span>) <span class="kw">in</span> <span class="ident">handles</span>.<span class="ident">iter</span>() {
<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">try_select</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">token</span>) {
<span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">token</span>, <span class="ident">i</span>, <span class="ident">ptr</span>));
}
}
<span class="kw">match</span> <span class="ident">timeout</span> {
<span class="ident">Timeout::Now</span> <span class="op">=</span><span class="op">></span> <span class="kw">return</span> <span class="prelude-val">None</span>,
<span class="ident">Timeout::Never</span> <span class="op">=</span><span class="op">></span> {}
<span class="ident">Timeout::At</span>(<span class="ident">when</span>) <span class="op">=</span><span class="op">></span> {
<span class="kw">if</span> <span class="ident">Instant::now</span>() <span class="op">></span><span class="op">=</span> <span class="ident">when</span> {
<span class="kw">return</span> <span class="prelude-val">None</span>;
}
}
}
}
}
<span class="doccomment">/// Runs until one of the operations becomes ready, potentially blocking the current thread.</span>
<span class="kw">fn</span> <span class="ident">run_ready</span>(
<span class="ident">handles</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [(<span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">SelectHandle</span>, <span class="ident">usize</span>, <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>)],
<span class="ident">timeout</span>: <span class="ident">Timeout</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="kw">if</span> <span class="ident">handles</span>.<span class="ident">is_empty</span>() {
<span class="comment">// Wait until the timeout and return.</span>
<span class="kw">match</span> <span class="ident">timeout</span> {
<span class="ident">Timeout::Now</span> <span class="op">=</span><span class="op">></span> <span class="kw">return</span> <span class="prelude-val">None</span>,
<span class="ident">Timeout::Never</span> <span class="op">=</span><span class="op">></span> {
<span class="ident">utils::sleep_until</span>(<span class="prelude-val">None</span>);
<span class="macro">unreachable!</span>();
}
<span class="ident">Timeout::At</span>(<span class="ident">when</span>) <span class="op">=</span><span class="op">></span> {
<span class="ident">utils::sleep_until</span>(<span class="prelude-val">Some</span>(<span class="ident">when</span>));
<span class="kw">return</span> <span class="prelude-val">None</span>;
}
}
}
<span class="comment">// Shuffle the operations for fairness.</span>
<span class="ident">utils::shuffle</span>(<span class="ident">handles</span>);
<span class="kw">loop</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="comment">// Check operations for readiness.</span>
<span class="kw">for</span> <span class="kw-2">&</span>(<span class="ident">handle</span>, <span class="ident">i</span>, <span class="kw">_</span>) <span class="kw">in</span> <span class="ident">handles</span>.<span class="ident">iter</span>() {
<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">is_ready</span>() {
<span class="kw">return</span> <span class="prelude-val">Some</span>(<span class="ident">i</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="comment">// Check for timeout.</span>
<span class="kw">match</span> <span class="ident">timeout</span> {
<span class="ident">Timeout::Now</span> <span class="op">=</span><span class="op">></span> <span class="kw">return</span> <span class="prelude-val">None</span>,
<span class="ident">Timeout::Never</span> <span class="op">=</span><span class="op">></span> {}
<span class="ident">Timeout::At</span>(<span class="ident">when</span>) <span class="op">=</span><span class="op">></span> {
<span class="kw">if</span> <span class="ident">Instant::now</span>() <span class="op">></span><span class="op">=</span> <span class="ident">when</span> {
<span class="kw">return</span> <span class="prelude-val">None</span>;
}
}
}
<span class="comment">// Prepare for blocking.</span>
<span class="kw">let</span> <span class="ident">res</span> <span class="op">=</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="kw-2">mut</span> <span class="ident">sel</span> <span class="op">=</span> <span class="ident">Selected::Waiting</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">registered_count</span> <span class="op">=</span> <span class="number">0</span>;
<span class="comment">// Begin watching all operations.</span>
<span class="kw">for</span> (<span class="ident">handle</span>, <span class="kw">_</span>, <span class="kw">_</span>) <span class="kw">in</span> <span class="ident">handles</span>.<span class="ident">iter_mut</span>() {
<span class="ident">registered_count</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
<span class="kw">let</span> <span class="ident">oper</span> <span class="op">=</span> <span class="ident">Operation::hook</span>::<span class="op"><</span><span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">SelectHandle</span><span class="op">></span>(<span class="ident">handle</span>);
<span class="comment">// If registration returns `false`, that means the operation has just become ready.</span>
<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">watch</span>(<span class="ident">oper</span>, <span class="ident">cx</span>) {
<span class="ident">sel</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">cx</span>.<span class="ident">try_select</span>(<span class="ident">Selected::Operation</span>(<span class="ident">oper</span>)) {
<span class="prelude-val">Ok</span>(()) <span class="op">=</span><span class="op">></span> <span class="ident">Selected::Operation</span>(<span class="ident">oper</span>),
<span class="prelude-val">Err</span>(<span class="ident">s</span>) <span class="op">=</span><span class="op">></span> <span class="ident">s</span>,
};
<span class="kw">break</span>;
}
<span class="comment">// If another thread has already chosen one of the operations, stop registration.</span>
<span class="ident">sel</span> <span class="op">=</span> <span class="ident">cx</span>.<span class="ident">selected</span>();
<span class="kw">if</span> <span class="ident">sel</span> <span class="op">!</span><span class="op">=</span> <span class="ident">Selected::Waiting</span> {
<span class="kw">break</span>;
}
}
<span class="kw">if</span> <span class="ident">sel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">Selected::Waiting</span> {
<span class="comment">// Check with each operation for how long we're allowed to block, and compute the</span>
<span class="comment">// earliest deadline.</span>
<span class="kw">let</span> <span class="kw-2">mut</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="kw">match</span> <span class="ident">timeout</span> {
<span class="ident">Timeout::Now</span> <span class="op">=</span><span class="op">></span> <span class="macro">unreachable!</span>(),
<span class="ident">Timeout::Never</span> <span class="op">=</span><span class="op">></span> <span class="prelude-val">None</span>,
<span class="ident">Timeout::At</span>(<span class="ident">when</span>) <span class="op">=</span><span class="op">></span> <span class="prelude-val">Some</span>(<span class="ident">when</span>),
};
<span class="kw">for</span> <span class="kw-2">&</span>(<span class="ident">handle</span>, <span class="kw">_</span>, <span class="kw">_</span>) <span class="kw">in</span> <span class="ident">handles</span>.<span class="ident">iter</span>() {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">x</span>) <span class="op">=</span> <span class="ident">handle</span>.<span class="ident">deadline</span>() {
<span class="ident">deadline</span> <span class="op">=</span> <span class="ident">deadline</span>.<span class="ident">map</span>(<span class="op">|</span><span class="ident">y</span><span class="op">|</span> <span class="ident">x</span>.<span class="ident">min</span>(<span class="ident">y</span>)).<span class="ident">or</span>(<span class="prelude-val">Some</span>(<span class="ident">x</span>));
}
}
<span class="comment">// Block the current thread.</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="comment">// Unwatch all operations.</span>
<span class="kw">for</span> (<span class="ident">handle</span>, <span class="kw">_</span>, <span class="kw">_</span>) <span class="kw">in</span> <span class="ident">handles</span>.<span class="ident">iter_mut</span>().<span class="ident">take</span>(<span class="ident">registered_count</span>) {
<span class="ident">handle</span>.<span class="ident">unwatch</span>(<span class="ident">Operation::hook</span>::<span class="op"><</span><span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">SelectHandle</span><span class="op">></span>(<span class="ident">handle</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="op">></span> {}
<span class="ident">Selected::Disconnected</span> <span class="op">=</span><span class="op">></span> {}
<span class="ident">Selected::Operation</span>(<span class="kw">_</span>) <span class="op">=</span><span class="op">></span> {
<span class="kw">for</span> (<span class="ident">handle</span>, <span class="ident">i</span>, <span class="kw">_</span>) <span class="kw">in</span> <span class="ident">handles</span>.<span class="ident">iter_mut</span>() {
<span class="kw">let</span> <span class="ident">oper</span> <span class="op">=</span> <span class="ident">Operation::hook</span>::<span class="op"><</span><span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">SelectHandle</span><span class="op">></span>(<span class="ident">handle</span>);
<span class="kw">if</span> <span class="ident">sel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">Selected::Operation</span>(<span class="ident">oper</span>) {
<span class="kw">return</span> <span class="prelude-val">Some</span>(<span class="kw-2">*</span><span class="ident">i</span>);
}
}
}
}
<span class="prelude-val">None</span>
});
<span class="comment">// Return if an operation became ready.</span>
<span class="kw">if</span> <span class="ident">res</span>.<span class="ident">is_some</span>() {
<span class="kw">return</span> <span class="ident">res</span>;
}
}
}
<span class="doccomment">/// Attempts to select one of the operations without blocking.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">try_select</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>(
<span class="ident">handles</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [(<span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw">dyn</span> <span class="ident">SelectHandle</span>, <span class="ident">usize</span>, <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>)],
) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">SelectedOperation</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>, <span class="ident">TrySelectError</span><span class="op">></span> {
<span class="kw">match</span> <span class="ident">run_select</span>(<span class="ident">handles</span>, <span class="ident">Timeout::Now</span>) {
<span class="prelude-val">None</span> <span class="op">=</span><span class="op">></span> <span class="prelude-val">Err</span>(<span class="ident">TrySelectError</span>),
<span class="prelude-val">Some</span>((<span class="ident">token</span>, <span class="ident">index</span>, <span class="ident">ptr</span>)) <span class="op">=</span><span class="op">></span> <span class="prelude-val">Ok</span>(<span class="ident">SelectedOperation</span> {
<span class="ident">token</span>,
<span class="ident">index</span>,
<span class="ident">ptr</span>,
<span class="ident">_marker</span>: <span class="ident">PhantomData</span>,
}),
}
}
<span class="doccomment">/// Blocks until one of the operations becomes ready and selects it.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">select</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>(
<span class="ident">handles</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [(<span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw">dyn</span> <span class="ident">SelectHandle</span>, <span class="ident">usize</span>, <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>)],
) <span class="op">-</span><span class="op">></span> <span class="ident">SelectedOperation</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="kw">if</span> <span class="ident">handles</span>.<span class="ident">is_empty</span>() {
<span class="macro">panic!</span>(<span class="string">"no operations have been added to `Select`"</span>);
}
<span class="kw">let</span> (<span class="ident">token</span>, <span class="ident">index</span>, <span class="ident">ptr</span>) <span class="op">=</span> <span class="ident">run_select</span>(<span class="ident">handles</span>, <span class="ident">Timeout::Never</span>).<span class="ident">unwrap</span>();
<span class="ident">SelectedOperation</span> {
<span class="ident">token</span>,
<span class="ident">index</span>,
<span class="ident">ptr</span>,
<span class="ident">_marker</span>: <span class="ident">PhantomData</span>,
}
}
<span class="doccomment">/// Blocks for a limited time until one of the operations becomes ready and selects it.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">select_timeout</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>(
<span class="ident">handles</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [(<span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw">dyn</span> <span class="ident">SelectHandle</span>, <span class="ident">usize</span>, <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>)],
<span class="ident">timeout</span>: <span class="ident">Duration</span>,
) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">SelectedOperation</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>, <span class="ident">SelectTimeoutError</span><span class="op">></span> {
<span class="ident">select_deadline</span>(<span class="ident">handles</span>, <span class="ident">Instant::now</span>() <span class="op">+</span> <span class="ident">timeout</span>)
}
<span class="doccomment">/// Blocks until a given deadline, or until one of the operations becomes ready and selects it.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">select_deadline</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>(
<span class="ident">handles</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [(<span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw">dyn</span> <span class="ident">SelectHandle</span>, <span class="ident">usize</span>, <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>)],
<span class="ident">deadline</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">SelectedOperation</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>, <span class="ident">SelectTimeoutError</span><span class="op">></span> {
<span class="kw">match</span> <span class="ident">run_select</span>(<span class="ident">handles</span>, <span class="ident">Timeout::At</span>(<span class="ident">deadline</span>)) {
<span class="prelude-val">None</span> <span class="op">=</span><span class="op">></span> <span class="prelude-val">Err</span>(<span class="ident">SelectTimeoutError</span>),
<span class="prelude-val">Some</span>((<span class="ident">token</span>, <span class="ident">index</span>, <span class="ident">ptr</span>)) <span class="op">=</span><span class="op">></span> <span class="prelude-val">Ok</span>(<span class="ident">SelectedOperation</span> {
<span class="ident">token</span>,
<span class="ident">index</span>,
<span class="ident">ptr</span>,
<span class="ident">_marker</span>: <span class="ident">PhantomData</span>,
}),
}
}
<span class="doccomment">/// Selects from a set of channel operations.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `Select` allows you to define a set of channel operations, wait until any one of them becomes</span>
<span class="doccomment">/// ready, and finally execute it. If multiple operations are ready at the same time, a random one</span>
<span class="doccomment">/// among them is selected.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An operation is considered to be ready if it doesn't have to block. Note that it is ready even</span>
<span class="doccomment">/// when it will simply return an error because the channel is disconnected.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The [`select!`] macro is a convenience wrapper around `Select`. However, it cannot select over a</span>
<span class="doccomment">/// dynamically created list of channel operations.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Once a list of operations has been built with `Select`, there are two different ways of</span>
<span class="doccomment">/// proceeding:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * Select an operation with [`try_select`], [`select`], or [`select_timeout`]. If successful,</span>
<span class="doccomment">/// the returned selected operation has already begun and **must** be completed. If we don't</span>
<span class="doccomment">/// complete it, a panic will occur.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * Wait for an operation to become ready with [`try_ready`], [`ready`], or [`ready_timeout`]. If</span>
<span class="doccomment">/// successful, we may attempt to execute the operation, but are not obliged to. In fact, it's</span>
<span class="doccomment">/// possible for another thread to make the operation not ready just before we try executing it,</span>
<span class="doccomment">/// so it's wise to use a retry loop. However, note that these methods might return with success</span>
<span class="doccomment">/// spuriously, so it's a good idea to always double check if the operation is really ready.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Use [`select`] to receive a message from a list of receivers:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_channel::{Receiver, RecvError, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// fn recv_multiple<T>(rs: &[Receiver<T>]) -> Result<T, RecvError> {</span>
<span class="doccomment">/// // Build a list of operations.</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// for r in rs {</span>
<span class="doccomment">/// sel.recv(r);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Complete the selected operation.</span>
<span class="doccomment">/// let oper = sel.select();</span>
<span class="doccomment">/// let index = oper.index();</span>
<span class="doccomment">/// oper.recv(&rs[index])</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Use [`ready`] to receive a message from a list of receivers:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_channel::{Receiver, RecvError, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// fn recv_multiple<T>(rs: &[Receiver<T>]) -> Result<T, RecvError> {</span>
<span class="doccomment">/// // Build a list of operations.</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// for r in rs {</span>
<span class="doccomment">/// sel.recv(r);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// loop {</span>
<span class="doccomment">/// // Wait until a receive operation becomes ready and try executing it.</span>
<span class="doccomment">/// let index = sel.ready();</span>
<span class="doccomment">/// let res = rs[index].try_recv();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // If the operation turns out not to be ready, retry.</span>
<span class="doccomment">/// if let Err(e) = res {</span>
<span class="doccomment">/// if e.is_empty() {</span>
<span class="doccomment">/// continue;</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Success!</span>
<span class="doccomment">/// return res.map_err(|_| RecvError);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`try_select`]: Select::try_select</span>
<span class="doccomment">/// [`select`]: Select::select</span>
<span class="doccomment">/// [`select_timeout`]: Select::select_timeout</span>
<span class="doccomment">/// [`try_ready`]: Select::try_ready</span>
<span class="doccomment">/// [`ready`]: Select::ready</span>
<span class="doccomment">/// [`ready_timeout`]: Select::ready_timeout</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Select</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="doccomment">/// A list of senders and receivers participating in selection.</span>
<span class="ident">handles</span>: <span class="ident">Vec</span><span class="op"><</span>(<span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw">dyn</span> <span class="ident">SelectHandle</span>, <span class="ident">usize</span>, <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>)<span class="op">></span>,
<span class="doccomment">/// The next index to assign to an operation.</span>
<span class="ident">next_index</span>: <span class="ident">usize</span>,
}
<span class="kw">unsafe</span> <span class="kw">impl</span> <span class="ident">Send</span> <span class="kw">for</span> <span class="ident">Select</span><span class="op"><</span><span class="lifetime">'_</span><span class="op">></span> {}
<span class="kw">unsafe</span> <span class="kw">impl</span> <span class="ident">Sync</span> <span class="kw">for</span> <span class="ident">Select</span><span class="op"><</span><span class="lifetime">'_</span><span class="op">></span> {}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="ident">Select</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="doccomment">/// Creates an empty list of channel operations for selection.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_channel::Select;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // The list of operations is empty, which means no operation can be selected.</span>
<span class="doccomment">/// assert!(sel.try_select().is_err());</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-</span><span class="op">></span> <span class="ident">Select</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="ident">Select</span> {
<span class="ident">handles</span>: <span class="ident">Vec::with_capacity</span>(<span class="number">4</span>),
<span class="ident">next_index</span>: <span class="number">0</span>,
}
}
<span class="doccomment">/// Adds a send operation.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Returns the index of the added operation.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_channel::{unbounded, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s, r) = unbounded::<i32>();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let index = sel.send(&s);</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">send</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">s</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">Sender</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">usize</span> {
<span class="kw">let</span> <span class="ident">i</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">next_index</span>;
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="ident">s</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Sender</span><span class="op"><</span><span class="kw">_</span><span class="op">></span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>;
<span class="self">self</span>.<span class="ident">handles</span>.<span class="ident">push</span>((<span class="ident">s</span>, <span class="ident">i</span>, <span class="ident">ptr</span>));
<span class="self">self</span>.<span class="ident">next_index</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
<span class="ident">i</span>
}
<span class="doccomment">/// Adds a receive operation.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Returns the index of the added operation.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_channel::{unbounded, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s, r) = unbounded::<i32>();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let index = sel.recv(&r);</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">recv</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">r</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">Receiver</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">usize</span> {
<span class="kw">let</span> <span class="ident">i</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">next_index</span>;
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="ident">r</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Receiver</span><span class="op"><</span><span class="kw">_</span><span class="op">></span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>;
<span class="self">self</span>.<span class="ident">handles</span>.<span class="ident">push</span>((<span class="ident">r</span>, <span class="ident">i</span>, <span class="ident">ptr</span>));
<span class="self">self</span>.<span class="ident">next_index</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
<span class="ident">i</span>
}
<span class="doccomment">/// Removes a previously added operation.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This is useful when an operation is selected because the channel got disconnected and we</span>
<span class="doccomment">/// want to try again to select a different operation instead.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If new operations are added after removing some, the indices of removed operations will not</span>
<span class="doccomment">/// be reused.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An attempt to remove a non-existing or already removed operation will panic.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_channel::{unbounded, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s1, r1) = unbounded::<i32>();</span>
<span class="doccomment">/// let (_, r2) = unbounded::<i32>();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let oper1 = sel.recv(&r1);</span>
<span class="doccomment">/// let oper2 = sel.recv(&r2);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Both operations are initially ready, so a random one will be executed.</span>
<span class="doccomment">/// let oper = sel.select();</span>
<span class="doccomment">/// assert_eq!(oper.index(), oper2);</span>
<span class="doccomment">/// assert!(oper.recv(&r2).is_err());</span>
<span class="doccomment">/// sel.remove(oper2);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// s1.send(10).unwrap();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let oper = sel.select();</span>
<span class="doccomment">/// assert_eq!(oper.index(), oper1);</span>
<span class="doccomment">/// assert_eq!(oper.recv(&r1), Ok(10));</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">remove</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">index</span>: <span class="ident">usize</span>) {
<span class="macro">assert!</span>(
<span class="ident">index</span> <span class="op"><</span> <span class="self">self</span>.<span class="ident">next_index</span>,
<span class="string">"index out of bounds; {} >= {}"</span>,
<span class="ident">index</span>,
<span class="self">self</span>.<span class="ident">next_index</span>,
);
<span class="kw">let</span> <span class="ident">i</span> <span class="op">=</span> <span class="self">self</span>
.<span class="ident">handles</span>
.<span class="ident">iter</span>()
.<span class="ident">enumerate</span>()
.<span class="ident">find</span>(<span class="op">|</span>(<span class="kw">_</span>, (<span class="kw">_</span>, <span class="ident">i</span>, <span class="kw">_</span>))<span class="op">|</span> <span class="kw-2">*</span><span class="ident">i</span> <span class="op">=</span><span class="op">=</span> <span class="ident">index</span>)
.<span class="ident">expect</span>(<span class="string">"no operation with this index"</span>)
.<span class="number">0</span>;
<span class="self">self</span>.<span class="ident">handles</span>.<span class="ident">swap_remove</span>(<span class="ident">i</span>);
}
<span class="doccomment">/// Attempts to select one of the operations without blocking.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If an operation is ready, it is selected and returned. If multiple operations are ready at</span>
<span class="doccomment">/// the same time, a random one among them is selected. If none of the operations are ready, an</span>
<span class="doccomment">/// error is returned.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An operation is considered to be ready if it doesn't have to block. Note that it is ready</span>
<span class="doccomment">/// even when it will simply return an error because the channel is disconnected.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The selected operation must be completed with [`SelectedOperation::send`]</span>
<span class="doccomment">/// or [`SelectedOperation::recv`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_channel::{unbounded, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s1, r1) = unbounded();</span>
<span class="doccomment">/// let (s2, r2) = unbounded();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// s1.send(10).unwrap();</span>
<span class="doccomment">/// s2.send(20).unwrap();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let oper1 = sel.recv(&r1);</span>
<span class="doccomment">/// let oper2 = sel.recv(&r2);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Both operations are initially ready, so a random one will be executed.</span>
<span class="doccomment">/// let oper = sel.try_select();</span>
<span class="doccomment">/// match oper {</span>
<span class="doccomment">/// Err(_) => panic!("both operations should be ready"),</span>
<span class="doccomment">/// Ok(oper) => match oper.index() {</span>
<span class="doccomment">/// i if i == oper1 => assert_eq!(oper.recv(&r1), Ok(10)),</span>
<span class="doccomment">/// i if i == oper2 => assert_eq!(oper.recv(&r2), Ok(20)),</span>
<span class="doccomment">/// _ => unreachable!(),</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">try_select</span>(<span class="kw-2">&</span><span class="kw-2">mut</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">SelectedOperation</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>, <span class="ident">TrySelectError</span><span class="op">></span> {
<span class="ident">try_select</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">handles</span>)
}
<span class="doccomment">/// Blocks until one of the operations becomes ready and selects it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Once an operation becomes ready, it is selected and returned. If multiple operations are</span>
<span class="doccomment">/// ready at the same time, a random one among them is selected.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An operation is considered to be ready if it doesn't have to block. Note that it is ready</span>
<span class="doccomment">/// even when it will simply return an error because the channel is disconnected.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The selected operation must be completed with [`SelectedOperation::send`]</span>
<span class="doccomment">/// or [`SelectedOperation::recv`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Panics if no operations have been added to `Select`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::thread;</span>
<span class="doccomment">/// use std::time::Duration;</span>
<span class="doccomment">/// use crossbeam_channel::{unbounded, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s1, r1) = unbounded();</span>
<span class="doccomment">/// let (s2, r2) = unbounded();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::spawn(move || {</span>
<span class="doccomment">/// thread::sleep(Duration::from_secs(1));</span>
<span class="doccomment">/// s1.send(10).unwrap();</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// thread::spawn(move || s2.send(20).unwrap());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let oper1 = sel.recv(&r1);</span>
<span class="doccomment">/// let oper2 = sel.recv(&r2);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // The second operation will be selected because it becomes ready first.</span>
<span class="doccomment">/// let oper = sel.select();</span>
<span class="doccomment">/// match oper.index() {</span>
<span class="doccomment">/// i if i == oper1 => assert_eq!(oper.recv(&r1), Ok(10)),</span>
<span class="doccomment">/// i if i == oper2 => assert_eq!(oper.recv(&r2), Ok(20)),</span>
<span class="doccomment">/// _ => unreachable!(),</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">select</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">SelectedOperation</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="ident">select</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">handles</span>)
}
<span class="doccomment">/// Blocks for a limited time until one of the operations becomes ready and selects it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If an operation becomes ready, it is selected and returned. If multiple operations are</span>
<span class="doccomment">/// ready at the same time, a random one among them is selected. If none of the operations</span>
<span class="doccomment">/// become ready for the specified duration, an error is returned.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An operation is considered to be ready if it doesn't have to block. Note that it is ready</span>
<span class="doccomment">/// even when it will simply return an error because the channel is disconnected.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The selected operation must be completed with [`SelectedOperation::send`]</span>
<span class="doccomment">/// or [`SelectedOperation::recv`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::thread;</span>
<span class="doccomment">/// use std::time::Duration;</span>
<span class="doccomment">/// use crossbeam_channel::{unbounded, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s1, r1) = unbounded();</span>
<span class="doccomment">/// let (s2, r2) = unbounded();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::spawn(move || {</span>
<span class="doccomment">/// thread::sleep(Duration::from_secs(1));</span>
<span class="doccomment">/// s1.send(10).unwrap();</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// thread::spawn(move || s2.send(20).unwrap());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let oper1 = sel.recv(&r1);</span>
<span class="doccomment">/// let oper2 = sel.recv(&r2);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // The second operation will be selected because it becomes ready first.</span>
<span class="doccomment">/// let oper = sel.select_timeout(Duration::from_millis(500));</span>
<span class="doccomment">/// match oper {</span>
<span class="doccomment">/// Err(_) => panic!("should not have timed out"),</span>
<span class="doccomment">/// Ok(oper) => match oper.index() {</span>
<span class="doccomment">/// i if i == oper1 => assert_eq!(oper.recv(&r1), Ok(10)),</span>
<span class="doccomment">/// i if i == oper2 => assert_eq!(oper.recv(&r2), Ok(20)),</span>
<span class="doccomment">/// _ => unreachable!(),</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">select_timeout</span>(
<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>,
<span class="ident">timeout</span>: <span class="ident">Duration</span>,
) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">SelectedOperation</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>, <span class="ident">SelectTimeoutError</span><span class="op">></span> {
<span class="ident">select_timeout</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">handles</span>, <span class="ident">timeout</span>)
}
<span class="doccomment">/// Blocks until a given deadline, or until one of the operations becomes ready and selects it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If an operation becomes ready, it is selected and returned. If multiple operations are</span>
<span class="doccomment">/// ready at the same time, a random one among them is selected. If none of the operations</span>
<span class="doccomment">/// become ready before the given deadline, an error is returned.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An operation is considered to be ready if it doesn't have to block. Note that it is ready</span>
<span class="doccomment">/// even when it will simply return an error because the channel is disconnected.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The selected operation must be completed with [`SelectedOperation::send`]</span>
<span class="doccomment">/// or [`SelectedOperation::recv`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::thread;</span>
<span class="doccomment">/// use std::time::{Instant, Duration};</span>
<span class="doccomment">/// use crossbeam_channel::{unbounded, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s1, r1) = unbounded();</span>
<span class="doccomment">/// let (s2, r2) = unbounded();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::spawn(move || {</span>
<span class="doccomment">/// thread::sleep(Duration::from_secs(1));</span>
<span class="doccomment">/// s1.send(10).unwrap();</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// thread::spawn(move || s2.send(20).unwrap());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let oper1 = sel.recv(&r1);</span>
<span class="doccomment">/// let oper2 = sel.recv(&r2);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let deadline = Instant::now() + Duration::from_millis(500);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // The second operation will be selected because it becomes ready first.</span>
<span class="doccomment">/// let oper = sel.select_deadline(deadline);</span>
<span class="doccomment">/// match oper {</span>
<span class="doccomment">/// Err(_) => panic!("should not have timed out"),</span>
<span class="doccomment">/// Ok(oper) => match oper.index() {</span>
<span class="doccomment">/// i if i == oper1 => assert_eq!(oper.recv(&r1), Ok(10)),</span>
<span class="doccomment">/// i if i == oper2 => assert_eq!(oper.recv(&r2), Ok(20)),</span>
<span class="doccomment">/// _ => unreachable!(),</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">select_deadline</span>(
<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>,
<span class="ident">deadline</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">SelectedOperation</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>, <span class="ident">SelectTimeoutError</span><span class="op">></span> {
<span class="ident">select_deadline</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">handles</span>, <span class="ident">deadline</span>)
}
<span class="doccomment">/// Attempts to find a ready operation without blocking.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If an operation is ready, its index is returned. If multiple operations are ready at the</span>
<span class="doccomment">/// same time, a random one among them is chosen. If none of the operations are ready, an error</span>
<span class="doccomment">/// is returned.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An operation is considered to be ready if it doesn't have to block. Note that it is ready</span>
<span class="doccomment">/// even when it will simply return an error because the channel is disconnected.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this method might return with success spuriously, so it's a good idea to always</span>
<span class="doccomment">/// double check if the operation is really ready.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_channel::{unbounded, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s1, r1) = unbounded();</span>
<span class="doccomment">/// let (s2, r2) = unbounded();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// s1.send(10).unwrap();</span>
<span class="doccomment">/// s2.send(20).unwrap();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let oper1 = sel.recv(&r1);</span>
<span class="doccomment">/// let oper2 = sel.recv(&r2);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Both operations are initially ready, so a random one will be chosen.</span>
<span class="doccomment">/// match sel.try_ready() {</span>
<span class="doccomment">/// Err(_) => panic!("both operations should be ready"),</span>
<span class="doccomment">/// Ok(i) if i == oper1 => assert_eq!(r1.try_recv(), Ok(10)),</span>
<span class="doccomment">/// Ok(i) if i == oper2 => assert_eq!(r2.try_recv(), Ok(20)),</span>
<span class="doccomment">/// Ok(_) => unreachable!(),</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">try_ready</span>(<span class="kw-2">&</span><span class="kw-2">mut</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">usize</span>, <span class="ident">TryReadyError</span><span class="op">></span> {
<span class="kw">match</span> <span class="ident">run_ready</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">handles</span>, <span class="ident">Timeout::Now</span>) {
<span class="prelude-val">None</span> <span class="op">=</span><span class="op">></span> <span class="prelude-val">Err</span>(<span class="ident">TryReadyError</span>),
<span class="prelude-val">Some</span>(<span class="ident">index</span>) <span class="op">=</span><span class="op">></span> <span class="prelude-val">Ok</span>(<span class="ident">index</span>),
}
}
<span class="doccomment">/// Blocks until one of the operations becomes ready.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Once an operation becomes ready, its index is returned. If multiple operations are ready at</span>
<span class="doccomment">/// the same time, a random one among them is chosen.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An operation is considered to be ready if it doesn't have to block. Note that it is ready</span>
<span class="doccomment">/// even when it will simply return an error because the channel is disconnected.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this method might return with success spuriously, so it's a good idea to always</span>
<span class="doccomment">/// double check if the operation is really ready.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Panics if no operations have been added to `Select`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::thread;</span>
<span class="doccomment">/// use std::time::Duration;</span>
<span class="doccomment">/// use crossbeam_channel::{unbounded, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s1, r1) = unbounded();</span>
<span class="doccomment">/// let (s2, r2) = unbounded();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::spawn(move || {</span>
<span class="doccomment">/// thread::sleep(Duration::from_secs(1));</span>
<span class="doccomment">/// s1.send(10).unwrap();</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// thread::spawn(move || s2.send(20).unwrap());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let oper1 = sel.recv(&r1);</span>
<span class="doccomment">/// let oper2 = sel.recv(&r2);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // The second operation will be selected because it becomes ready first.</span>
<span class="doccomment">/// match sel.ready() {</span>
<span class="doccomment">/// i if i == oper1 => assert_eq!(r1.try_recv(), Ok(10)),</span>
<span class="doccomment">/// i if i == oper2 => assert_eq!(r2.try_recv(), Ok(20)),</span>
<span class="doccomment">/// _ => unreachable!(),</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">ready</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">usize</span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">handles</span>.<span class="ident">is_empty</span>() {
<span class="macro">panic!</span>(<span class="string">"no operations have been added to `Select`"</span>);
}
<span class="ident">run_ready</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">handles</span>, <span class="ident">Timeout::Never</span>).<span class="ident">unwrap</span>()
}
<span class="doccomment">/// Blocks for a limited time until one of the operations becomes ready.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If an operation becomes ready, its index is returned. If multiple operations are ready at</span>
<span class="doccomment">/// the same time, a random one among them is chosen. If none of the operations become ready</span>
<span class="doccomment">/// for the specified duration, an error is returned.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An operation is considered to be ready if it doesn't have to block. Note that it is ready</span>
<span class="doccomment">/// even when it will simply return an error because the channel is disconnected.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this method might return with success spuriously, so it's a good idea to double</span>
<span class="doccomment">/// check if the operation is really ready.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::thread;</span>
<span class="doccomment">/// use std::time::Duration;</span>
<span class="doccomment">/// use crossbeam_channel::{unbounded, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s1, r1) = unbounded();</span>
<span class="doccomment">/// let (s2, r2) = unbounded();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::spawn(move || {</span>
<span class="doccomment">/// thread::sleep(Duration::from_secs(1));</span>
<span class="doccomment">/// s1.send(10).unwrap();</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// thread::spawn(move || s2.send(20).unwrap());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let oper1 = sel.recv(&r1);</span>
<span class="doccomment">/// let oper2 = sel.recv(&r2);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // The second operation will be selected because it becomes ready first.</span>
<span class="doccomment">/// match sel.ready_timeout(Duration::from_millis(500)) {</span>
<span class="doccomment">/// Err(_) => panic!("should not have timed out"),</span>
<span class="doccomment">/// Ok(i) if i == oper1 => assert_eq!(r1.try_recv(), Ok(10)),</span>
<span class="doccomment">/// Ok(i) if i == oper2 => assert_eq!(r2.try_recv(), Ok(20)),</span>
<span class="doccomment">/// Ok(_) => unreachable!(),</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">ready_timeout</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">timeout</span>: <span class="ident">Duration</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">usize</span>, <span class="ident">ReadyTimeoutError</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">ready_deadline</span>(<span class="ident">Instant::now</span>() <span class="op">+</span> <span class="ident">timeout</span>)
}
<span class="doccomment">/// Blocks until a given deadline, or until one of the operations becomes ready.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If an operation becomes ready, its index is returned. If multiple operations are ready at</span>
<span class="doccomment">/// the same time, a random one among them is chosen. If none of the operations become ready</span>
<span class="doccomment">/// before the deadline, an error is returned.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An operation is considered to be ready if it doesn't have to block. Note that it is ready</span>
<span class="doccomment">/// even when it will simply return an error because the channel is disconnected.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this method might return with success spuriously, so it's a good idea to double</span>
<span class="doccomment">/// check if the operation is really ready.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::thread;</span>
<span class="doccomment">/// use std::time::{Duration, Instant};</span>
<span class="doccomment">/// use crossbeam_channel::{unbounded, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let deadline = Instant::now() + Duration::from_millis(500);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s1, r1) = unbounded();</span>
<span class="doccomment">/// let (s2, r2) = unbounded();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::spawn(move || {</span>
<span class="doccomment">/// thread::sleep(Duration::from_secs(1));</span>
<span class="doccomment">/// s1.send(10).unwrap();</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// thread::spawn(move || s2.send(20).unwrap());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let oper1 = sel.recv(&r1);</span>
<span class="doccomment">/// let oper2 = sel.recv(&r2);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // The second operation will be selected because it becomes ready first.</span>
<span class="doccomment">/// match sel.ready_deadline(deadline) {</span>
<span class="doccomment">/// Err(_) => panic!("should not have timed out"),</span>
<span class="doccomment">/// Ok(i) if i == oper1 => assert_eq!(r1.try_recv(), Ok(10)),</span>
<span class="doccomment">/// Ok(i) if i == oper2 => assert_eq!(r2.try_recv(), Ok(20)),</span>
<span class="doccomment">/// Ok(_) => unreachable!(),</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">ready_deadline</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">deadline</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">usize</span>, <span class="ident">ReadyTimeoutError</span><span class="op">></span> {
<span class="kw">match</span> <span class="ident">run_ready</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">handles</span>, <span class="ident">Timeout::At</span>(<span class="ident">deadline</span>)) {
<span class="prelude-val">None</span> <span class="op">=</span><span class="op">></span> <span class="prelude-val">Err</span>(<span class="ident">ReadyTimeoutError</span>),
<span class="prelude-val">Some</span>(<span class="ident">index</span>) <span class="op">=</span><span class="op">></span> <span class="prelude-val">Ok</span>(<span class="ident">index</span>),
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="ident">Clone</span> <span class="kw">for</span> <span class="ident">Select</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">clone</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Select</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="ident">Select</span> {
<span class="ident">handles</span>: <span class="self">self</span>.<span class="ident">handles</span>.<span class="ident">clone</span>(),
<span class="ident">next_index</span>: <span class="self">self</span>.<span class="ident">next_index</span>,
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="ident">Default</span> <span class="kw">for</span> <span class="ident">Select</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">default</span>() <span class="op">-</span><span class="op">></span> <span class="ident">Select</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="ident">Select::new</span>()
}
}
<span class="kw">impl</span> <span class="ident">fmt::Debug</span> <span class="kw">for</span> <span class="ident">Select</span><span class="op"><</span><span class="lifetime">'_</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt::Formatter</span><span class="op"><</span><span class="lifetime">'_</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">fmt::Result</span> {
<span class="ident">f</span>.<span class="ident">pad</span>(<span class="string">"Select { .. }"</span>)
}
}
<span class="doccomment">/// A selected operation that needs to be completed.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// To complete the operation, call [`send`] or [`recv`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Forgetting to complete the operation is an error and might lead to deadlocks. If a</span>
<span class="doccomment">/// `SelectedOperation` is dropped without completion, a panic occurs.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`send`]: SelectedOperation::send</span>
<span class="doccomment">/// [`recv`]: SelectedOperation::recv</span>
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">SelectedOperation</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="doccomment">/// Token needed to complete the operation.</span>
<span class="ident">token</span>: <span class="ident">Token</span>,
<span class="doccomment">/// The index of the selected operation.</span>
<span class="ident">index</span>: <span class="ident">usize</span>,
<span class="doccomment">/// The address of the selected `Sender` or `Receiver`.</span>
<span class="ident">ptr</span>: <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>,
<span class="doccomment">/// Indicates that `Sender`s and `Receiver`s are borrowed.</span>
<span class="ident">_marker</span>: <span class="ident">PhantomData</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> ()<span class="op">></span>,
}
<span class="kw">impl</span> <span class="ident">SelectedOperation</span><span class="op"><</span><span class="lifetime">'_</span><span class="op">></span> {
<span class="doccomment">/// Returns the index of the selected operation.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_channel::{bounded, Select};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s1, r1) = bounded::<()>(0);</span>
<span class="doccomment">/// let (s2, r2) = bounded::<()>(0);</span>
<span class="doccomment">/// let (s3, r3) = bounded::<()>(1);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let oper1 = sel.send(&s1);</span>
<span class="doccomment">/// let oper2 = sel.recv(&r2);</span>
<span class="doccomment">/// let oper3 = sel.send(&s3);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Only the last operation is ready.</span>
<span class="doccomment">/// let oper = sel.select();</span>
<span class="doccomment">/// assert_eq!(oper.index(), 2);</span>
<span class="doccomment">/// assert_eq!(oper.index(), oper3);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Complete the operation.</span>
<span class="doccomment">/// oper.send(&s3, ()).unwrap();</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">index</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="self">self</span>.<span class="ident">index</span>
}
<span class="doccomment">/// Completes the send operation.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The passed [`Sender`] reference must be the same one that was used in [`Select::send`]</span>
<span class="doccomment">/// when the operation was added.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Panics if an incorrect [`Sender`] reference is passed.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_channel::{bounded, Select, SendError};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s, r) = bounded::<i32>(0);</span>
<span class="doccomment">/// drop(r);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let oper1 = sel.send(&s);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let oper = sel.select();</span>
<span class="doccomment">/// assert_eq!(oper.index(), oper1);</span>
<span class="doccomment">/// assert_eq!(oper.send(&s, 10), Err(SendError(10)));</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">send</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">s</span>: <span class="kw-2">&</span><span class="ident">Sender</span><span class="op"><</span><span class="ident">T</span><span class="op">></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">SendError</span><span class="op"><</span><span class="ident">T</span><span class="op">></span><span class="op">></span> {
<span class="macro">assert!</span>(
<span class="ident">s</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Sender</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span> <span class="op">=</span><span class="op">=</span> <span class="self">self</span>.<span class="ident">ptr</span>,
<span class="string">"passed a sender that wasn't selected"</span>,
);
<span class="kw">let</span> <span class="ident">res</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="ident">channel::write</span>(<span class="ident">s</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">token</span>, <span class="ident">msg</span>) };
<span class="ident">mem::forget</span>(<span class="self">self</span>);
<span class="ident">res</span>.<span class="ident">map_err</span>(<span class="ident">SendError</span>)
}
<span class="doccomment">/// Completes the receive operation.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The passed [`Receiver`] reference must be the same one that was used in [`Select::recv`]</span>
<span class="doccomment">/// when the operation was added.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Panics if an incorrect [`Receiver`] reference is passed.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_channel::{bounded, Select, RecvError};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (s, r) = bounded::<i32>(0);</span>
<span class="doccomment">/// drop(s);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut sel = Select::new();</span>
<span class="doccomment">/// let oper1 = sel.recv(&r);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let oper = sel.select();</span>
<span class="doccomment">/// assert_eq!(oper.index(), oper1);</span>
<span class="doccomment">/// assert_eq!(oper.recv(&r), Err(RecvError));</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">recv</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">r</span>: <span class="kw-2">&</span><span class="ident">Receiver</span><span class="op"><</span><span class="ident">T</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">RecvError</span><span class="op">></span> {
<span class="macro">assert!</span>(
<span class="ident">r</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Receiver</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span> <span class="op">=</span><span class="op">=</span> <span class="self">self</span>.<span class="ident">ptr</span>,
<span class="string">"passed a receiver that wasn't selected"</span>,
);
<span class="kw">let</span> <span class="ident">res</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="ident">channel::read</span>(<span class="ident">r</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">token</span>) };
<span class="ident">mem::forget</span>(<span class="self">self</span>);
<span class="ident">res</span>.<span class="ident">map_err</span>(<span class="op">|</span><span class="kw">_</span><span class="op">|</span> <span class="ident">RecvError</span>)
}
}
<span class="kw">impl</span> <span class="ident">fmt::Debug</span> <span class="kw">for</span> <span class="ident">SelectedOperation</span><span class="op"><</span><span class="lifetime">'_</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt::Formatter</span><span class="op"><</span><span class="lifetime">'_</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">fmt::Result</span> {
<span class="ident">f</span>.<span class="ident">pad</span>(<span class="string">"SelectedOperation { .. }"</span>)
}
}
<span class="kw">impl</span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">SelectedOperation</span><span class="op"><</span><span class="lifetime">'_</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">panic!</span>(<span class="string">"dropped `SelectedOperation` without completing the operation"</span>);
}
}
</pre></div>
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