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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Latch (picos_std.Picos_std_sync.Latch)</title><meta charset="utf-8"/><link rel="stylesheet" href="../../../_odoc-theme/odoc.css"/><meta name="generator" content="odoc 3.0.0"/><meta name="viewport" content="width=device-width,initial-scale=1.0"/><script src="../../../highlight.pack.js"></script><script>hljs.initHighlightingOnLoad();</script></head><body class="odoc"><nav class="odoc-nav"><a href="../index.html">Up</a> – <a href="../../../index.html">Index</a> » <a href="../../index.html">picos_std</a> » <a href="../index.html">Picos_std_sync</a> » Latch</nav><header class="odoc-preamble"><h1>Module <code><span>Picos_std_sync.Latch</span></code></h1><p>A dynamic single-use countdown latch.</p><p>Latches are typically used for determining when a finite set of parallel computations is done. If the size of the set is known a priori, then the latch can be initialized with the size as initial count and then each computation just <a href="#val-decr" title="decr">decrements</a> the latch.</p><p>If the size is unknown, i.e. it is determined dynamically, then a latch is initialized with a count of one, the a priori known computations are started and then the latch is <a href="#val-decr" title="decr">decremented</a>. When a computation is stsrted, the latch is <a href="#val-try_incr" title="try_incr">incremented</a>, and then <a href="#val-decr" title="decr">decremented</a> once the computation has finished.</p></header><div class="odoc-content"><div class="odoc-spec"><div class="spec type anchored" id="type-t"><a href="#type-t" class="anchor"></a><code><span><span class="keyword">type</span> t</span></code></div><div class="spec-doc"><p>Represents a dynamic countdown latch.</p></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-create"><a href="#val-create" class="anchor"></a><code><span><span class="keyword">val</span> create : <span><span class="optlabel">?padded</span>:bool <span class="arrow">-></span></span> <span>int <span class="arrow">-></span></span> <a href="#type-t">t</a></span></code></div><div class="spec-doc"><p><code>create initial</code> creates a new countdown latch with the specified <code>initial</code> count.</p><ul class="at-tags"><li class="raises"><span class="at-tag">raises</span> <code>Invalid_argument</code> <p>in case the specified <code>initial</code> count is negative.</p></li></ul></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-try_decr"><a href="#val-try_decr" class="anchor"></a><code><span><span class="keyword">val</span> try_decr : <span><a href="#type-t">t</a> <span class="arrow">-></span></span> bool</span></code></div><div class="spec-doc"><p><code>try_decr latch</code> attempts to decrement the count of the latch and returns <code>true</code> in case the count of the latch was greater than zero and <code>false</code> in case the count already was zero.</p></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-decr"><a href="#val-decr" class="anchor"></a><code><span><span class="keyword">val</span> decr : <span><a href="#type-t">t</a> <span class="arrow">-></span></span> unit</span></code></div><div class="spec-doc"><p><code>decr latch</code> is equivalent to:</p><pre class="language-ocaml"><code> if not (try_decr latch) then
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invalid_arg "zero count"</code></pre><p>ℹ️ This operation is not cancelable.</p><ul class="at-tags"><li class="raises"><span class="at-tag">raises</span> <code>Invalid_argument</code> <p>in case the count of the latch is zero.</p></li></ul></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-try_incr"><a href="#val-try_incr" class="anchor"></a><code><span><span class="keyword">val</span> try_incr : <span><a href="#type-t">t</a> <span class="arrow">-></span></span> bool</span></code></div><div class="spec-doc"><p><code>try_incr latch</code> attempts to increment the count of the latch and returns <code>true</code> on success and <code>false</code> on failure, which means that the latch has already reached zero.</p></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-incr"><a href="#val-incr" class="anchor"></a><code><span><span class="keyword">val</span> incr : <span><a href="#type-t">t</a> <span class="arrow">-></span></span> unit</span></code></div><div class="spec-doc"><p><code>incr latch</code> is equivalent to:</p><pre class="language-ocaml"><code> if not (try_incr latch) then
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invalid_arg "zero count"</code></pre><ul class="at-tags"><li class="raises"><span class="at-tag">raises</span> <code>Invalid_argument</code> <p>in case the count of the latch is zero.</p></li></ul></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-await"><a href="#val-await" class="anchor"></a><code><span><span class="keyword">val</span> await : <span><a href="#type-t">t</a> <span class="arrow">-></span></span> unit</span></code></div><div class="spec-doc"><p><code>await latch</code> returns after the count of the latch has reached zero.</p></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-await_evt"><a href="#val-await_evt" class="anchor"></a><code><span><span class="keyword">val</span> await_evt : <span><a href="#type-t">t</a> <span class="arrow">-></span></span> <span>unit <a href="../../Picos_std_event/Event/index.html#type-t">Picos_std_event.Event.t</a></span></span></code></div><div class="spec-doc"><p><code>await_evt latch</code> returns an event that can be committed to once the count of the latch has reached zero.</p></div></div></div></body></html>
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