<!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/jpeg-decoder-0.1.22/src/worker/multithreaded.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>multithreaded.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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<span class="doccomment">//! This module implements per-component parallelism.</span>
<span class="doccomment">//! It should be possible to implement per-row parallelism as well,</span>
<span class="doccomment">//! which should also boost performance of grayscale images</span>
<span class="doccomment">//! and allow scaling to more cores.</span>
<span class="doccomment">//! However, that would be more complex, so we use this as a starting point.</span>
<span class="kw">use</span> <span class="ident">decoder::MAX_COMPONENTS</span>;
<span class="kw">use</span> <span class="ident">error::Result</span>;
<span class="kw">use</span> <span class="ident">std</span>::{<span class="ident">mem</span>, <span class="ident">sync::mpsc</span>::{<span class="self">self</span>, <span class="ident">Sender</span>}};
<span class="kw">use</span> <span class="ident">std::thread</span>;
<span class="kw">use</span> <span class="kw">super</span>::{<span class="ident">RowData</span>, <span class="ident">Worker</span>};
<span class="kw">use</span> <span class="kw">super</span><span class="ident">::immediate::ImmediateWorker</span>;
<span class="kw">enum</span> <span class="ident">WorkerMsg</span> {
<span class="ident">Start</span>(<span class="ident">RowData</span>),
<span class="ident">AppendRow</span>(<span class="ident">Vec</span><span class="op"><</span><span class="ident">i16</span><span class="op">></span>),
<span class="ident">GetResult</span>(<span class="ident">Sender</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span><span class="op">></span>),
}
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">MultiThreadedWorker</span> {
<span class="ident">senders</span>: [<span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Sender</span><span class="op"><</span><span class="ident">WorkerMsg</span><span class="op">></span><span class="op">></span>; <span class="ident">MAX_COMPONENTS</span>]
}
<span class="kw">impl</span> <span class="ident">Worker</span> <span class="kw">for</span> <span class="ident">MultiThreadedWorker</span> {
<span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="self">Self</span><span class="op">></span> {
<span class="prelude-val">Ok</span>(<span class="ident">MultiThreadedWorker</span> {
<span class="ident">senders</span>: [<span class="prelude-val">None</span>, <span class="prelude-val">None</span>, <span class="prelude-val">None</span>, <span class="prelude-val">None</span>]
})
}
<span class="kw">fn</span> <span class="ident">start</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">row_data</span>: <span class="ident">RowData</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span>()<span class="op">></span> {
<span class="comment">// if there is no worker thread for this component yet, start one</span>
<span class="kw">let</span> <span class="ident">component</span> <span class="op">=</span> <span class="ident">row_data</span>.<span class="ident">index</span>;
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">None</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">senders</span>[<span class="ident">component</span>] {
<span class="kw">let</span> <span class="ident">sender</span> <span class="op">=</span> <span class="ident">spawn_worker_thread</span>(<span class="ident">component</span>)<span class="question-mark">?</span>;
<span class="self">self</span>.<span class="ident">senders</span>[<span class="ident">component</span>] <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">sender</span>);
}
<span class="comment">// we do the "take out value and put it back in once we're done" dance here</span>
<span class="comment">// and in all other message-passing methods because there's not that many rows</span>
<span class="comment">// and this should be cheaper than spawning MAX_COMPONENTS many threads up front</span>
<span class="kw">let</span> <span class="ident">sender</span> <span class="op">=</span> <span class="ident">mem::replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">senders</span>[<span class="ident">component</span>], <span class="prelude-val">None</span>).<span class="ident">unwrap</span>();
<span class="ident">sender</span>.<span class="ident">send</span>(<span class="ident">WorkerMsg::Start</span>(<span class="ident">row_data</span>)).<span class="ident">expect</span>(<span class="string">"jpeg-decoder worker thread error"</span>);
<span class="self">self</span>.<span class="ident">senders</span>[<span class="ident">component</span>] <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">sender</span>);
<span class="prelude-val">Ok</span>(())
}
<span class="kw">fn</span> <span class="ident">append_row</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">row</span>: (<span class="ident">usize</span>, <span class="ident">Vec</span><span class="op"><</span><span class="ident">i16</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="op">></span> {
<span class="kw">let</span> <span class="ident">component</span> <span class="op">=</span> <span class="ident">row</span>.<span class="number">0</span>;
<span class="kw">let</span> <span class="ident">sender</span> <span class="op">=</span> <span class="ident">mem::replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">senders</span>[<span class="ident">component</span>], <span class="prelude-val">None</span>).<span class="ident">unwrap</span>();
<span class="ident">sender</span>.<span class="ident">send</span>(<span class="ident">WorkerMsg::AppendRow</span>(<span class="ident">row</span>.<span class="number">1</span>)).<span class="ident">expect</span>(<span class="string">"jpeg-decoder worker thread error"</span>);
<span class="self">self</span>.<span class="ident">senders</span>[<span class="ident">component</span>] <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">sender</span>);
<span class="prelude-val">Ok</span>(())
}
<span class="kw">fn</span> <span class="ident">get_result</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="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span><span class="op">></span> {
<span class="kw">let</span> (<span class="ident">tx</span>, <span class="ident">rx</span>) <span class="op">=</span> <span class="ident">mpsc::channel</span>();
<span class="kw">let</span> <span class="ident">sender</span> <span class="op">=</span> <span class="ident">mem::replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">senders</span>[<span class="ident">index</span>], <span class="prelude-val">None</span>).<span class="ident">unwrap</span>();
<span class="ident">sender</span>.<span class="ident">send</span>(<span class="ident">WorkerMsg::GetResult</span>(<span class="ident">tx</span>)).<span class="ident">expect</span>(<span class="string">"jpeg-decoder worker thread error"</span>);
<span class="prelude-val">Ok</span>(<span class="ident">rx</span>.<span class="ident">recv</span>().<span class="ident">expect</span>(<span class="string">"jpeg-decoder worker thread error"</span>))
}
}
<span class="kw">fn</span> <span class="ident">spawn_worker_thread</span>(<span class="ident">component</span>: <span class="ident">usize</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">Sender</span><span class="op"><</span><span class="ident">WorkerMsg</span><span class="op">></span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">thread_builder</span> <span class="op">=</span> <span class="ident">thread::Builder::new</span>().<span class="ident">name</span>(<span class="macro">format!</span>(<span class="string">"worker thread for component {}"</span>, <span class="ident">component</span>));
<span class="kw">let</span> (<span class="ident">tx</span>, <span class="ident">rx</span>) <span class="op">=</span> <span class="ident">mpsc::channel</span>();
<span class="ident">thread_builder</span>.<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">|</span><span class="op">|</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">worker</span> <span class="op">=</span> <span class="ident">ImmediateWorker::new_immediate</span>();
<span class="kw">while</span> <span class="kw">let</span> <span class="prelude-val">Ok</span>(<span class="ident">message</span>) <span class="op">=</span> <span class="ident">rx</span>.<span class="ident">recv</span>() {
<span class="kw">match</span> <span class="ident">message</span> {
<span class="ident">WorkerMsg::Start</span>(<span class="kw-2">mut</span> <span class="ident">data</span>) <span class="op">=</span><span class="op">></span> {
<span class="comment">// we always set component index to 0 for worker threads</span>
<span class="comment">// because they only ever handle one per thread and we don't want them</span>
<span class="comment">// to attempt to access nonexistent components</span>
<span class="ident">data</span>.<span class="ident">index</span> <span class="op">=</span> <span class="number">0</span>;
<span class="ident">worker</span>.<span class="ident">start_immediate</span>(<span class="ident">data</span>);
},
<span class="ident">WorkerMsg::AppendRow</span>(<span class="ident">row</span>) <span class="op">=</span><span class="op">></span> {
<span class="ident">worker</span>.<span class="ident">append_row_immediate</span>((<span class="number">0</span>, <span class="ident">row</span>));
},
<span class="ident">WorkerMsg::GetResult</span>(<span class="ident">chan</span>) <span class="op">=</span><span class="op">></span> {
<span class="kw">let</span> <span class="kw">_</span> <span class="op">=</span> <span class="ident">chan</span>.<span class="ident">send</span>(<span class="ident">worker</span>.<span class="ident">get_result_immediate</span>(<span class="number">0</span>));
<span class="kw">break</span>;
},
}
}
})<span class="question-mark">?</span>;
<span class="prelude-val">Ok</span>(<span class="ident">tx</span>)
}</pre></div>
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