<!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 `rtic-sync/src/signal.rs`."><title>signal.rs - source</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../../static.files/rustdoc-42caa33d.css"><meta name="rustdoc-vars" data-root-path="../../" data-static-root-path="../../static.files/" data-current-crate="rtic_sync" data-themes="" data-resource-suffix="" data-rustdoc-version="1.84.0 (9fc6b4312 2025-01-07)" data-channel="1.84.0" data-search-js="search-92e6798f.js" data-settings-js="settings-0f613d39.js" ><script src="../../static.files/storage-59e33391.js"></script><script defer src="../../static.files/src-script-56102188.js"></script><script defer src="../../src-files.js"></script><script defer src="../../static.files/main-5f194d8c.js"></script><noscript><link rel="stylesheet" href="../../static.files/noscript-893ab5e7.css"></noscript><link rel="alternate icon" type="image/png" href="../../static.files/favicon-32x32-6580c154.png"><link rel="icon" type="image/svg+xml" href="../../static.files/favicon-044be391.svg"></head><body class="rustdoc src"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="src-sidebar-title"><h2>Files</h2></div></nav><div class="sidebar-resizer"></div><main><rustdoc-search></rustdoc-search><section id="main-content" class="content"><div class="main-heading"><h1><div class="sub-heading">rtic_sync/</div>signal.rs</h1><rustdoc-toolbar></rustdoc-toolbar></div><div class="example-wrap"><div data-nosnippet><pre class="src-line-numbers">
<a href="#1" id="1">1</a>
<a href="#2" id="2">2</a>
<a href="#3" id="3">3</a>
<a href="#4" id="4">4</a>
<a href="#5" id="5">5</a>
<a href="#6" id="6">6</a>
<a href="#7" id="7">7</a>
<a href="#8" id="8">8</a>
<a href="#9" id="9">9</a>
<a href="#10" id="10">10</a>
<a href="#11" id="11">11</a>
<a href="#12" id="12">12</a>
<a href="#13" id="13">13</a>
<a href="#14" id="14">14</a>
<a href="#15" id="15">15</a>
<a href="#16" id="16">16</a>
<a href="#17" id="17">17</a>
<a href="#18" id="18">18</a>
<a href="#19" id="19">19</a>
<a href="#20" id="20">20</a>
<a href="#21" id="21">21</a>
<a href="#22" id="22">22</a>
<a href="#23" id="23">23</a>
<a href="#24" id="24">24</a>
<a href="#25" id="25">25</a>
<a href="#26" id="26">26</a>
<a href="#27" id="27">27</a>
<a href="#28" id="28">28</a>
<a href="#29" id="29">29</a>
<a href="#30" id="30">30</a>
<a href="#31" id="31">31</a>
<a href="#32" id="32">32</a>
<a href="#33" id="33">33</a>
<a href="#34" id="34">34</a>
<a href="#35" id="35">35</a>
<a href="#36" id="36">36</a>
<a href="#37" id="37">37</a>
<a href="#38" id="38">38</a>
<a href="#39" id="39">39</a>
<a href="#40" id="40">40</a>
<a href="#41" id="41">41</a>
<a href="#42" id="42">42</a>
<a href="#43" id="43">43</a>
<a href="#44" id="44">44</a>
<a href="#45" id="45">45</a>
<a href="#46" id="46">46</a>
<a href="#47" id="47">47</a>
<a href="#48" id="48">48</a>
<a href="#49" id="49">49</a>
<a href="#50" id="50">50</a>
<a href="#51" id="51">51</a>
<a href="#52" id="52">52</a>
<a href="#53" id="53">53</a>
<a href="#54" id="54">54</a>
<a href="#55" id="55">55</a>
<a href="#56" id="56">56</a>
<a href="#57" id="57">57</a>
<a href="#58" id="58">58</a>
<a href="#59" id="59">59</a>
<a href="#60" id="60">60</a>
<a href="#61" id="61">61</a>
<a href="#62" id="62">62</a>
<a href="#63" id="63">63</a>
<a href="#64" id="64">64</a>
<a href="#65" id="65">65</a>
<a href="#66" id="66">66</a>
<a href="#67" id="67">67</a>
<a href="#68" id="68">68</a>
<a href="#69" id="69">69</a>
<a href="#70" id="70">70</a>
<a href="#71" id="71">71</a>
<a href="#72" id="72">72</a>
<a href="#73" id="73">73</a>
<a href="#74" id="74">74</a>
<a href="#75" id="75">75</a>
<a href="#76" id="76">76</a>
<a href="#77" id="77">77</a>
<a href="#78" id="78">78</a>
<a href="#79" id="79">79</a>
<a href="#80" id="80">80</a>
<a href="#81" id="81">81</a>
<a href="#82" id="82">82</a>
<a href="#83" id="83">83</a>
<a href="#84" id="84">84</a>
<a href="#85" id="85">85</a>
<a href="#86" id="86">86</a>
<a href="#87" id="87">87</a>
<a href="#88" id="88">88</a>
<a href="#89" id="89">89</a>
<a href="#90" id="90">90</a>
<a href="#91" id="91">91</a>
<a href="#92" id="92">92</a>
<a href="#93" id="93">93</a>
<a href="#94" id="94">94</a>
<a href="#95" id="95">95</a>
<a href="#96" id="96">96</a>
<a href="#97" id="97">97</a>
<a href="#98" id="98">98</a>
<a href="#99" id="99">99</a>
<a href="#100" id="100">100</a>
<a href="#101" id="101">101</a>
<a href="#102" id="102">102</a>
<a href="#103" id="103">103</a>
<a href="#104" id="104">104</a>
<a href="#105" id="105">105</a>
<a href="#106" id="106">106</a>
<a href="#107" id="107">107</a>
<a href="#108" id="108">108</a>
<a href="#109" id="109">109</a>
<a href="#110" id="110">110</a>
<a href="#111" id="111">111</a>
<a href="#112" id="112">112</a>
<a href="#113" id="113">113</a>
<a href="#114" id="114">114</a>
<a href="#115" id="115">115</a>
<a href="#116" id="116">116</a>
<a href="#117" id="117">117</a>
<a href="#118" id="118">118</a>
<a href="#119" id="119">119</a>
<a href="#120" id="120">120</a>
<a href="#121" id="121">121</a>
<a href="#122" id="122">122</a>
<a href="#123" id="123">123</a>
<a href="#124" id="124">124</a>
<a href="#125" id="125">125</a>
<a href="#126" id="126">126</a>
<a href="#127" id="127">127</a>
<a href="#128" id="128">128</a>
<a href="#129" id="129">129</a>
<a href="#130" id="130">130</a>
<a href="#131" id="131">131</a>
<a href="#132" id="132">132</a>
<a href="#133" id="133">133</a>
<a href="#134" id="134">134</a>
<a href="#135" id="135">135</a>
<a href="#136" id="136">136</a>
<a href="#137" id="137">137</a>
<a href="#138" id="138">138</a>
<a href="#139" id="139">139</a>
<a href="#140" id="140">140</a>
<a href="#141" id="141">141</a>
<a href="#142" id="142">142</a>
<a href="#143" id="143">143</a>
<a href="#144" id="144">144</a>
<a href="#145" id="145">145</a>
<a href="#146" id="146">146</a>
<a href="#147" id="147">147</a>
<a href="#148" id="148">148</a>
<a href="#149" id="149">149</a>
<a href="#150" id="150">150</a>
<a href="#151" id="151">151</a>
<a href="#152" id="152">152</a>
<a href="#153" id="153">153</a>
<a href="#154" id="154">154</a>
<a href="#155" id="155">155</a>
<a href="#156" id="156">156</a>
<a href="#157" id="157">157</a>
<a href="#158" id="158">158</a>
<a href="#159" id="159">159</a>
<a href="#160" id="160">160</a>
<a href="#161" id="161">161</a>
<a href="#162" id="162">162</a>
<a href="#163" id="163">163</a>
<a href="#164" id="164">164</a>
<a href="#165" id="165">165</a>
<a href="#166" id="166">166</a>
<a href="#167" id="167">167</a>
<a href="#168" id="168">168</a>
<a href="#169" id="169">169</a>
<a href="#170" id="170">170</a>
<a href="#171" id="171">171</a>
<a href="#172" id="172">172</a>
<a href="#173" id="173">173</a>
<a href="#174" id="174">174</a>
<a href="#175" id="175">175</a>
<a href="#176" id="176">176</a>
<a href="#177" id="177">177</a>
<a href="#178" id="178">178</a>
<a href="#179" id="179">179</a>
<a href="#180" id="180">180</a>
<a href="#181" id="181">181</a>
<a href="#182" id="182">182</a>
<a href="#183" id="183">183</a>
<a href="#184" id="184">184</a>
<a href="#185" id="185">185</a>
<a href="#186" id="186">186</a>
<a href="#187" id="187">187</a>
<a href="#188" id="188">188</a>
<a href="#189" id="189">189</a>
<a href="#190" id="190">190</a>
<a href="#191" id="191">191</a>
<a href="#192" id="192">192</a>
<a href="#193" id="193">193</a>
<a href="#194" id="194">194</a>
<a href="#195" id="195">195</a>
<a href="#196" id="196">196</a>
<a href="#197" id="197">197</a>
<a href="#198" id="198">198</a>
<a href="#199" id="199">199</a>
<a href="#200" id="200">200</a>
<a href="#201" id="201">201</a>
<a href="#202" id="202">202</a>
<a href="#203" id="203">203</a>
<a href="#204" id="204">204</a>
<a href="#205" id="205">205</a>
<a href="#206" id="206">206</a>
<a href="#207" id="207">207</a>
<a href="#208" id="208">208</a>
<a href="#209" id="209">209</a>
<a href="#210" id="210">210</a>
<a href="#211" id="211">211</a>
<a href="#212" id="212">212</a>
<a href="#213" id="213">213</a>
<a href="#214" id="214">214</a>
<a href="#215" id="215">215</a>
<a href="#216" id="216">216</a>
<a href="#217" id="217">217</a>
<a href="#218" id="218">218</a>
<a href="#219" id="219">219</a>
<a href="#220" id="220">220</a>
<a href="#221" id="221">221</a>
<a href="#222" id="222">222</a>
<a href="#223" id="223">223</a>
<a href="#224" id="224">224</a>
<a href="#225" id="225">225</a>
<a href="#226" id="226">226</a>
<a href="#227" id="227">227</a>
<a href="#228" id="228">228</a>
<a href="#229" id="229">229</a>
<a href="#230" id="230">230</a>
<a href="#231" id="231">231</a>
<a href="#232" id="232">232</a>
<a href="#233" id="233">233</a>
<a href="#234" id="234">234</a>
<a href="#235" id="235">235</a>
<a href="#236" id="236">236</a>
<a href="#237" id="237">237</a></pre></div><pre class="rust"><code><span class="doccomment">//! A "latest only" value store with unlimited writers and async waiting.

</span><span class="kw">use </span>core::{cell::UnsafeCell, future::poll_fn, task::Poll};
<span class="kw">use </span>rtic_common::waker_registration::CriticalSectionWakerRegistration;

<span class="doccomment">/// Basically an Option but for indicating
/// whether the store has been set or not
</span><span class="attr">#[derive(Clone, Copy)]
</span><span class="kw">enum </span>Store&lt;T&gt; {
    Set(T),
    Unset,
}

<span class="doccomment">/// A "latest only" value store with unlimited writers and async waiting.
</span><span class="kw">pub struct </span>Signal&lt;T: Copy&gt; {
    waker: CriticalSectionWakerRegistration,
    store: UnsafeCell&lt;Store&lt;T&gt;&gt;,
}

<span class="kw">impl</span>&lt;T&gt; core::fmt::Debug <span class="kw">for </span>Signal&lt;T&gt;
<span class="kw">where
    </span>T: core::marker::Copy,
{
    <span class="kw">fn </span>fmt(<span class="kw-2">&amp;</span><span class="self">self</span>, fmt: <span class="kw-2">&amp;mut </span>core::fmt::Formatter&lt;<span class="lifetime">'_</span>&gt;) -&gt; core::fmt::Result {
        fmt.write_fmt(<span class="macro">format_args!</span>(
            <span class="string">"Signal&lt;{}&gt;{{ .. }}"</span>,
            core::any::type_name::&lt;T&gt;()
        ))
    }
}

<span class="kw">impl</span>&lt;T: Copy&gt; Default <span class="kw">for </span>Signal&lt;T&gt; {
    <span class="kw">fn </span>default() -&gt; <span class="self">Self </span>{
        <span class="self">Self</span>::new()
    }
}

<span class="kw">unsafe impl</span>&lt;T: Copy&gt; Send <span class="kw">for </span>Signal&lt;T&gt; {}
<span class="kw">unsafe impl</span>&lt;T: Copy&gt; Sync <span class="kw">for </span>Signal&lt;T&gt; {}

<span class="kw">impl</span>&lt;T: Copy&gt; Signal&lt;T&gt; {
    <span class="doccomment">/// Create a new signal.
    </span><span class="kw">pub const fn </span>new() -&gt; <span class="self">Self </span>{
        <span class="self">Self </span>{
            waker: CriticalSectionWakerRegistration::new(),
            store: UnsafeCell::new(Store::Unset),
        }
    }

    <span class="doccomment">/// Split the signal into a writer and reader.
    </span><span class="kw">pub fn </span>split(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; (SignalWriter&lt;T&gt;, SignalReader&lt;T&gt;) {
        (SignalWriter { parent: <span class="self">self </span>}, SignalReader { parent: <span class="self">self </span>})
    }
}

<span class="doccomment">/// Facilitates the writing of values to a Signal.
</span><span class="attr">#[derive(Clone)]
</span><span class="kw">pub struct </span>SignalWriter&lt;<span class="lifetime">'a</span>, T: Copy&gt; {
    parent: <span class="kw-2">&amp;</span><span class="lifetime">'a </span>Signal&lt;T&gt;,
}

<span class="kw">impl</span>&lt;T&gt; core::fmt::Debug <span class="kw">for </span>SignalWriter&lt;<span class="lifetime">'_</span>, T&gt;
<span class="kw">where
    </span>T: core::marker::Copy,
{
    <span class="kw">fn </span>fmt(<span class="kw-2">&amp;</span><span class="self">self</span>, fmt: <span class="kw-2">&amp;mut </span>core::fmt::Formatter&lt;<span class="lifetime">'_</span>&gt;) -&gt; core::fmt::Result {
        fmt.write_fmt(<span class="macro">format_args!</span>(
            <span class="string">"SignalWriter&lt;{}&gt;{{ .. }}"</span>,
            core::any::type_name::&lt;T&gt;()
        ))
    }
}

<span class="kw">impl</span>&lt;T: Copy&gt; SignalWriter&lt;<span class="lifetime">'_</span>, T&gt; {
    <span class="doccomment">/// Write a raw Store value to the Signal.
    </span><span class="kw">fn </span>write_inner(<span class="kw-2">&amp;mut </span><span class="self">self</span>, value: Store&lt;T&gt;) {
        critical_section::with(|<span class="kw">_</span>| {
            <span class="comment">// SAFETY: in a cs: exclusive access
            </span><span class="kw">unsafe </span>{ <span class="self">self</span>.parent.store.get().replace(value) };
        });

        <span class="self">self</span>.parent.waker.wake();
    }

    <span class="doccomment">/// Write a value to the Signal.
    </span><span class="kw">pub fn </span>write(<span class="kw-2">&amp;mut </span><span class="self">self</span>, value: T) {
        <span class="self">self</span>.write_inner(Store::Set(value));
    }

    <span class="doccomment">/// Clear the stored value in the Signal (if any).
    </span><span class="kw">pub fn </span>clear(<span class="kw-2">&amp;mut </span><span class="self">self</span>) {
        <span class="self">self</span>.write_inner(Store::Unset);
    }
}

<span class="doccomment">/// Facilitates the async reading of values from the Signal.
</span><span class="kw">pub struct </span>SignalReader&lt;<span class="lifetime">'a</span>, T: Copy&gt; {
    parent: <span class="kw-2">&amp;</span><span class="lifetime">'a </span>Signal&lt;T&gt;,
}

<span class="kw">impl</span>&lt;T&gt; core::fmt::Debug <span class="kw">for </span>SignalReader&lt;<span class="lifetime">'_</span>, T&gt;
<span class="kw">where
    </span>T: core::marker::Copy,
{
    <span class="kw">fn </span>fmt(<span class="kw-2">&amp;</span><span class="self">self</span>, fmt: <span class="kw-2">&amp;mut </span>core::fmt::Formatter&lt;<span class="lifetime">'_</span>&gt;) -&gt; core::fmt::Result {
        fmt.write_fmt(<span class="macro">format_args!</span>(
            <span class="string">"SignalReader&lt;{}&gt;{{ .. }}"</span>,
            core::any::type_name::&lt;T&gt;()
        ))
    }
}

<span class="kw">impl</span>&lt;<span class="lifetime">'a</span>, T: Copy&gt; SignalReader&lt;<span class="lifetime">'a</span>, T&gt; {
    <span class="doccomment">/// Immediately read and evict the latest value stored in the Signal.
    </span><span class="kw">fn </span>take(<span class="kw-2">&amp;mut </span><span class="self">self</span>) -&gt; Store&lt;T&gt; {
        critical_section::with(|<span class="kw">_</span>| {
            <span class="comment">// SAFETY: in a cs: exclusive access
            </span><span class="kw">unsafe </span>{ <span class="self">self</span>.parent.store.get().replace(Store::Unset) }
        })
    }

    <span class="doccomment">/// Returns a pending value if present, or None if no value is available.
    ///
    /// Upon read, the stored value is evicted.
    </span><span class="kw">pub fn </span>try_read(<span class="kw-2">&amp;mut </span><span class="self">self</span>) -&gt; <span class="prelude-ty">Option</span>&lt;T&gt; {
        <span class="kw">match </span><span class="self">self</span>.take() {
            Store::Unset =&gt; <span class="prelude-val">None</span>,
            Store::Set(value) =&gt; <span class="prelude-val">Some</span>(value),
        }
    }

    <span class="doccomment">/// Wait for a new value to be written and read it.
    ///
    /// If a value is already pending it will be returned immediately.
    ///
    /// Upon read, the stored value is evicted.
    </span><span class="kw">pub async fn </span>wait(<span class="kw-2">&amp;mut </span><span class="self">self</span>) -&gt; T {
        poll_fn(|ctx| {
            <span class="self">self</span>.parent.waker.register(ctx.waker());
            <span class="kw">match </span><span class="self">self</span>.take() {
                Store::Unset =&gt; Poll::Pending,
                Store::Set(value) =&gt; Poll::Ready(value),
            }
        })
        .<span class="kw">await
    </span>}

    <span class="doccomment">/// Wait for a new value to be written and read it.
    ///
    /// If a value is already pending, it will be evicted and a new
    /// value must be written for the wait to resolve.
    ///
    /// Upon read, the stored value is evicted.
    </span><span class="kw">pub async fn </span>wait_fresh(<span class="kw-2">&amp;mut </span><span class="self">self</span>) -&gt; T {
        <span class="self">self</span>.take();
        <span class="self">self</span>.wait().<span class="kw">await
    </span>}
}

<span class="doccomment">/// Convenience macro for creating a Signal.
</span><span class="attr">#[macro_export]
</span><span class="macro">macro_rules!</span> make_signal {
    ( <span class="macro-nonterminal">$T</span>:ty ) =&gt; {{
        <span class="kw">static </span>SIGNAL: Signal&lt;<span class="macro-nonterminal">$T</span>&gt; = Signal::new();

        SIGNAL.split()
    }};
}

<span class="attr">#[cfg(test)]
</span><span class="kw">mod </span>tests {
    <span class="kw">use </span>static_cell::StaticCell;

    <span class="kw">use super</span>::<span class="kw-2">*</span>;

    <span class="attr">#[test]
    </span><span class="kw">fn </span>empty() {
        <span class="kw">let </span>(_writer, <span class="kw-2">mut </span>reader) = <span class="macro">make_signal!</span>(u32);

        <span class="macro">assert!</span>(reader.try_read().is_none());
    }

    <span class="attr">#[test]
    </span><span class="kw">fn </span>ping_pong() {
        <span class="kw">let </span>(<span class="kw-2">mut </span>writer, <span class="kw-2">mut </span>reader) = <span class="macro">make_signal!</span>(u32);

        writer.write(<span class="number">0xde</span>);
        <span class="macro">assert!</span>(reader.try_read().is_some_and(|value| value == <span class="number">0xde</span>));
    }

    <span class="attr">#[test]
    </span><span class="kw">fn </span>latest() {
        <span class="kw">let </span>(<span class="kw-2">mut </span>writer, <span class="kw-2">mut </span>reader) = <span class="macro">make_signal!</span>(u32);

        writer.write(<span class="number">0xde</span>);
        writer.write(<span class="number">0xad</span>);
        writer.write(<span class="number">0xbe</span>);
        writer.write(<span class="number">0xef</span>);
        <span class="macro">assert!</span>(reader.try_read().is_some_and(|value| value == <span class="number">0xef</span>));
    }

    <span class="attr">#[test]
    </span><span class="kw">fn </span>consumption() {
        <span class="kw">let </span>(<span class="kw-2">mut </span>writer, <span class="kw-2">mut </span>reader) = <span class="macro">make_signal!</span>(u32);

        writer.write(<span class="number">0xaa</span>);
        <span class="macro">assert!</span>(reader.try_read().is_some_and(|value| value == <span class="number">0xaa</span>));
        <span class="macro">assert!</span>(reader.try_read().is_none());
    }

    <span class="attr">#[tokio::test]
    </span><span class="kw">async fn </span>pending() {
        <span class="kw">let </span>(<span class="kw-2">mut </span>writer, <span class="kw-2">mut </span>reader) = <span class="macro">make_signal!</span>(u32);

        writer.write(<span class="number">0xaa</span>);

        <span class="macro">assert_eq!</span>(reader.wait().<span class="kw">await</span>, <span class="number">0xaa</span>);
    }

    <span class="attr">#[tokio::test]
    </span><span class="kw">async fn </span>waiting() {
        <span class="kw">static </span>READER: StaticCell&lt;SignalReader&lt;u32&gt;&gt; = StaticCell::new();
        <span class="kw">let </span>(<span class="kw-2">mut </span>writer, reader) = <span class="macro">make_signal!</span>(u32);

        writer.write(<span class="number">0xaa</span>);

        <span class="kw">let </span>reader = READER.init(reader);
        <span class="kw">let </span>handle = tokio::spawn(reader.wait_fresh());

        tokio::task::yield_now().<span class="kw">await</span>; <span class="comment">// encourage tokio executor to poll reader future
        </span><span class="macro">assert!</span>(!handle.is_finished()); <span class="comment">// verify reader future did not resolve after poll

        </span>writer.write(<span class="number">0xab</span>);

        <span class="macro">assert!</span>(handle.<span class="kw">await</span>.is_ok_and(|value| value == <span class="number">0xab</span>));
    }
}
</code></pre></div></section></main></body></html>