oxipng/doc/bitflags/__core/sync/struct.RwLock.html
2016-04-20 15:59:23 -04:00

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<h1 class='fqn'><span class='in-band'>Struct <a href='../../index.html'>bitflags</a>::<wbr><a href='../index.html'>__core</a>::<wbr><a href='index.html'>sync</a>::<wbr><a class='struct' href=''>RwLock</a></span><span class='out-of-band'><span id='render-detail'>
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</span><a id='src-10419' class='srclink' href='https://doc.rust-lang.org/nightly/std/sync/rwlock/struct.RwLock.html?gotosrc=10419' title='goto source code'>[src]</a></span></h1>
<pre class='rust struct'>pub struct RwLock&lt;T&gt; <span class='where'>where T: ?<a class='trait' href='../../../bitflags/__core/marker/trait.Sized.html' title='bitflags::__core::marker::Sized'>Sized</a></span> {
// some fields omitted
}</pre><span class="since">1.0.0</span><div class='docblock'><p>A reader-writer lock</p>
<p>This type of lock allows a number of readers or at most one writer at any
point in time. The write portion of this lock typically allows modification
of the underlying data (exclusive access) and the read portion of this lock
typically allows for read-only access (shared access).</p>
<p>The priority policy of the lock is dependent on the underlying operating
system&#39;s implementation, and this type does not guarantee that any
particular policy will be used.</p>
<p>The type parameter <code>T</code> represents the data that this lock protects. It is
required that <code>T</code> satisfies <code>Send</code> to be shared across threads and <code>Sync</code> to
allow concurrent access through readers. The RAII guards returned from the
locking methods implement <code>Deref</code> (and <code>DerefMut</code> for the <code>write</code> methods)
to allow access to the contained of the lock.</p>
<h1 id='poisoning' class='section-header'><a href='#poisoning'>Poisoning</a></h1>
<p>RwLocks, like Mutexes, will become poisoned on panics. Note, however, that
an RwLock may only be poisoned if a panic occurs while it is locked
exclusively (write mode). If a panic occurs in any reader, then the lock
will not be poisoned.</p>
<h1 id='examples' class='section-header'><a href='#examples'>Examples</a></h1>
<pre class='rust rust-example-rendered'>
<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>sync</span>::<span class='ident'>RwLock</span>;
<span class='kw'>let</span> <span class='ident'>lock</span> <span class='op'>=</span> <span class='ident'>RwLock</span>::<span class='ident'>new</span>(<span class='number'>5</span>);
<span class='comment'>// many reader locks can be held at once</span>
{
<span class='kw'>let</span> <span class='ident'>r1</span> <span class='op'>=</span> <span class='ident'>lock</span>.<span class='ident'>read</span>().<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>r2</span> <span class='op'>=</span> <span class='ident'>lock</span>.<span class='ident'>read</span>().<span class='ident'>unwrap</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='op'>*</span><span class='ident'>r1</span>, <span class='number'>5</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='op'>*</span><span class='ident'>r2</span>, <span class='number'>5</span>);
} <span class='comment'>// read locks are dropped at this point</span>
<span class='comment'>// only one write lock may be held, however</span>
{
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>w</span> <span class='op'>=</span> <span class='ident'>lock</span>.<span class='ident'>write</span>().<span class='ident'>unwrap</span>();
<span class='op'>*</span><span class='ident'>w</span> <span class='op'>+=</span> <span class='number'>1</span>;
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='op'>*</span><span class='ident'>w</span>, <span class='number'>6</span>);
} <span class='comment'>// write lock is dropped here</span></pre>
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