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<h1 class='fqn'><span class='in-band'>Module <a href='../index.html'>nom</a>::<wbr><a class='mod' href=''>consumer</a></span><span class='out-of-band'><span id='render-detail'>
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</span><a id='src-4292' class='srclink' href='../../src/nom/consumer.rs.html#1-266' title='goto source code'>[src]</a></span></h1>
<div class='docblock'><p>Data consumers</p>
<p>The goal of data producers is to parse data depending on the previous result.
It can be used to selectively seek in a file.</p>
<h2 id="example" class='section-header'><a
href="#example">Example</a></h2>
<p>This consumer will take 4 samples from the input, print them, then stop</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>use</span> <span class='ident'>nom</span>::{<span class='ident'>IResult</span>,<span class='ident'>Needed</span>,<span class='ident'>MemProducer</span>,<span class='ident'>Consumer</span>,<span class='ident'>ConsumerState</span>};
<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>str</span>;
<span class='kw'>struct</span> <span class='ident'>TestPrintConsumer</span> {
<span class='ident'>counter</span>: <span class='ident'>usize</span>
}
<span class='kw'>impl</span> <span class='ident'>TestPrintConsumer</span> {
<span class='kw'>fn</span> <span class='ident'>new</span>() <span class='op'>-></span> <span class='ident'>TestPrintConsumer</span> {
<span class='ident'>TestPrintConsumer</span> { <span class='ident'>counter</span>: <span class='number'>0</span> }
}
}
<span class='kw'>fn</span> <span class='ident'>take4</span>(<span class='ident'>i</span>:<span class='kw-2'>&</span>[<span class='ident'>u8</span>]) <span class='op'>-></span> <span class='ident'>IResult</span><span class='op'><</span><span class='kw-2'>&</span>[<span class='ident'>u8</span>], <span class='kw-2'>&</span>[<span class='ident'>u8</span>]<span class='op'>></span>{
<span class='kw'>if</span> <span class='ident'>i</span>.<span class='ident'>len</span>() <span class='op'><</span> <span class='number'>4</span> {
<span class='ident'>IResult</span>::<span class='ident'>Incomplete</span>(<span class='ident'>Needed</span>::<span class='ident'>Size</span>(<span class='number'>4</span>))
} <span class='kw'>else</span> {
<span class='ident'>IResult</span>::<span class='ident'>Done</span>(<span class='kw-2'>&</span><span class='ident'>i</span>[<span class='number'>4</span>..],<span class='kw-2'>&</span><span class='ident'>i</span>[<span class='number'>0</span>..<span class='number'>4</span>])
}
}
<span class='comment'>// Return ConsumerState::Await if it needs more data, or ConsumerDone when it ends</span>
<span class='kw'>impl</span> <span class='ident'>Consumer</span> <span class='kw'>for</span> <span class='ident'>TestPrintConsumer</span> {
<span class='kw'>fn</span> <span class='ident'>consume</span>(<span class='kw-2'>&</span><span class='kw-2'>mut</span> <span class='self'>self</span>, <span class='ident'>input</span>: <span class='kw-2'>&</span>[<span class='ident'>u8</span>]) <span class='op'>-></span> <span class='ident'>ConsumerState</span> {
<span class='kw'>match</span> <span class='ident'>take4</span>(<span class='ident'>input</span>) {
<span class='ident'>IResult</span>::<span class='ident'>Error</span>(<span class='ident'>a</span>) <span class='op'>=></span> <span class='ident'>ConsumerState</span>::<span class='ident'>ConsumerError</span>(<span class='number'>0</span>),
<span class='ident'>IResult</span>::<span class='ident'>Incomplete</span>(<span class='ident'>a</span>) <span class='op'>=></span> <span class='ident'>ConsumerState</span>::<span class='ident'>Await</span>(<span class='number'>0</span>, <span class='number'>4</span>),
<span class='ident'>IResult</span>::<span class='ident'>Done</span>(<span class='ident'>i</span>, <span class='ident'>o</span>) <span class='op'>=></span> {
<span class='macro'>println</span><span class='macro'>!</span>(<span class='string'>"{} -> {}"</span>, <span class='self'>self</span>.<span class='ident'>counter</span>, <span class='ident'>str</span>::<span class='ident'>from_utf8</span>(<span class='ident'>o</span>).<span class='ident'>unwrap</span>());
<span class='self'>self</span>.<span class='ident'>counter</span> <span class='op'>=</span> <span class='self'>self</span>.<span class='ident'>counter</span> <span class='op'>+</span> <span class='number'>1</span>;
<span class='kw'>if</span> <span class='self'>self</span>.<span class='ident'>counter</span> <span class='op'><=</span> <span class='number'>4</span> {
<span class='ident'>ConsumerState</span>::<span class='ident'>Await</span>(<span class='number'>4</span>, <span class='number'>4</span>)
} <span class='kw'>else</span> {
<span class='ident'>ConsumerState</span>::<span class='ident'>ConsumerDone</span>
}
}
}
}
<span class='kw'>fn</span> <span class='ident'>end</span>(<span class='kw-2'>&</span><span class='kw-2'>mut</span> <span class='self'>self</span>) {
<span class='macro'>println</span><span class='macro'>!</span>(<span class='string'>"finished"</span>);
}
}
<span class='comment'>// It can consume data directly from a producer</span>
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>p</span> <span class='op'>=</span> <span class='ident'>MemProducer</span>::<span class='ident'>new</span>(<span class='string'>b"abcdefghijklmnopqrstuvwx"</span>, <span class='number'>4</span>);
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>c</span> <span class='op'>=</span> <span class='ident'>TestPrintConsumer</span>::<span class='ident'>new</span>();
<span class='ident'>c</span>.<span class='ident'>run</span>(<span class='kw-2'>&</span><span class='kw-2'>mut</span> <span class='ident'>p</span>);
</pre>
</div><h2 id='enums' class='section-header'><a href="#enums">Enums</a></h2>
<table>
<tr class=' module-item'>
<td><a class='enum' href='enum.ConsumerState.html'
title='nom::consumer::ConsumerState'>ConsumerState</a></td>
<td class='docblock short'>
<p>Holds the current state of the consumer</p>
</td>
</tr>
</table><h2 id='traits' class='section-header'><a href="#traits">Traits</a></h2>
<table>
<tr class=' module-item'>
<td><a class='trait' href='trait.Consumer.html'
title='nom::consumer::Consumer'>Consumer</a></td>
<td class='docblock short'>
<p>Implement the consume method, taking a byte array as input and returning a consumer state</p>
</td>
</tr>
</table></section>
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