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<h1 class='fqn'><span class='in-band'>Function <a href='../index.html'>futures</a>::<wbr><a href='index.html'>task</a>::<wbr><a class="fn" href=''>init</a></span><span class='out-of-band'><span id='render-detail'>
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<pre class='rust fn'>pub unsafe fn init(get: fn() -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.pointer.html">*mut </a><a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u8.html">u8</a>, set: fn(_: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.pointer.html">*mut </a><a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u8.html">u8</a>)) -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></pre><div class='docblock'><p>Initialize the <code>futures</code> task system.</p>
<p>This function is an unsafe low-level implementation detail typically only
used by crates using <code>futures</code> in <code>no_std</code> context. Users of this crate
who also use the standard library never need to invoke this function.</p>
<p>The task system in the <code>futures</code> crate relies on some notion of "local
storage" for the running thread and/or context. The <code>task::current</code> function
can get invoked in any context, for example, and needs to be able to return
a <code>Task</code>. Typically with the standard library this is supported with
thread-local-storage, but this is not available in <code>no_std</code> contexts!</p>
<p>This function is provided to allow <code>no_std</code> contexts to continue to be able
to use the standard task system in this crate. The functions provided here
will be used as-if they were thread-local-storage getters/setters. The <code>get</code>
function provided is used to retrieve the current thread-local value of the
task system's pointer, returning null if not initialized. The <code>set</code> function
updates the value of the pointer.</p>
<h1 id="return-value" class="section-header"><a href="#return-value">Return value</a></h1>
<p>This function will return whether initialization succeeded or not. This
function can be called concurrently and only the first invocation will
succeed. If <code>false</code> is returned then the <code>get</code> and <code>set</code> pointers provided
were <em>not</em> registered for use with the task system, but if <code>true</code> was
provided then they will be called when the task system is used.</p>
<p>Note that while safe to call concurrently it's recommended to still perform
external synchronization when calling this function. This task system is
not guaranteed to be ready to go until a call to this function returns
<code>true</code>. In other words, if you call this function and see <code>false</code>, the
task system may not be ready to go as another thread may still be calling
<code>init</code>.</p>
<h1 id="unsafety" class="section-header"><a href="#unsafety">Unsafety</a></h1>
<p>This function is unsafe due to the requirements on the behavior of the
<code>get</code> and <code>set</code> functions. The pointers returned from these functions must
reflect the semantics specified above and must also be thread-local,
depending on the definition of a "thread" in the calling context.</p>
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