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<p class='location'>Trait Decoder</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#associated-types">Associated Types</a><div class="sidebar-links"><a href="#associatedtype.Item">Item</a><a href="#associatedtype.Error">Error</a></div><a class="sidebar-title" href="#required-methods">Required Methods</a><div class="sidebar-links"><a href="#tymethod.decode">decode</a></div><a class="sidebar-title" href="#provided-methods">Provided Methods</a><div class="sidebar-links"><a href="#method.decode_eof">decode_eof</a><a href="#method.framed">framed</a></div><a class="sidebar-title" href="#implementors">Implementors</a></div><p class='location'><a href='index.html'>tokio_codec</a></p><script>window.sidebarCurrent = {name: 'Decoder', ty: 'trait', relpath: ''};</script><script defer src="sidebar-items.js"></script></div>
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<section id='main' class="content"><h1 class='fqn'><span class='in-band'>Trait <a href='index.html'>tokio_codec</a>::<wbr><a class="trait" href=''>Decoder</a></span><span class='out-of-band'><span id='render-detail'>
<a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">
[<span class='inner'>&#x2212;</span>]
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</span><a class='srclink' href='../src/tokio_io/codec/decoder.rs.html#22-117' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class='rust trait'>pub trait Decoder {
type <a href='#associatedtype.Item' class="type">Item</a>;
type <a href='#associatedtype.Error' class="type">Error</a>: <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.From.html" title="trait core::convert::From">From</a>&lt;<a class="struct" href="https://doc.rust-lang.org/nightly/std/io/error/struct.Error.html" title="struct std::io::error::Error">Error</a>&gt;;
fn <a href='#tymethod.decode' class='fnname'>decode</a>(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;src: &amp;mut <a class="struct" href="../bytes/bytes/struct.BytesMut.html" title="struct bytes::bytes::BytesMut">BytesMut</a><br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="enum" href="https://doc.rust-lang.org/nightly/core/option/enum.Option.html" title="enum core::option::Option">Option</a>&lt;Self::<a class="type" href="../tokio_codec/trait.Decoder.html#associatedtype.Item" title="type tokio_codec::Decoder::Item">Item</a>&gt;, Self::<a class="type" href="../tokio_codec/trait.Decoder.html#associatedtype.Error" title="type tokio_codec::Decoder::Error">Error</a>&gt;;
fn <a href='#method.decode_eof' class='fnname'>decode_eof</a>(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;buf: &amp;mut <a class="struct" href="../bytes/bytes/struct.BytesMut.html" title="struct bytes::bytes::BytesMut">BytesMut</a><br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="enum" href="https://doc.rust-lang.org/nightly/core/option/enum.Option.html" title="enum core::option::Option">Option</a>&lt;Self::<a class="type" href="../tokio_codec/trait.Decoder.html#associatedtype.Item" title="type tokio_codec::Decoder::Item">Item</a>&gt;, Self::<a class="type" href="../tokio_codec/trait.Decoder.html#associatedtype.Error" title="type tokio_codec::Decoder::Error">Error</a>&gt; { ... }
<div class='item-spacer'></div> fn <a href='#method.framed' class='fnname'>framed</a>&lt;T&gt;(self, io: T) -&gt; <a class="struct" href="../tokio_codec/struct.Framed.html" title="struct tokio_codec::Framed">Framed</a>&lt;T, Self&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Self: <a class="trait" href="../tokio_codec/trait.Encoder.html" title="trait tokio_codec::Encoder">Encoder</a>,<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="../tokio_io/async_read/trait.AsyncRead.html" title="trait tokio_io::async_read::AsyncRead">AsyncRead</a> + <a class="trait" href="../tokio_io/async_write/trait.AsyncWrite.html" title="trait tokio_io::async_write::AsyncWrite">AsyncWrite</a></span>,
{ ... }
}</pre></div><div class='docblock'><p>Decoding of frames via buffers.</p>
<p>This trait is used when constructing an instance of <code>Framed</code> or
<code>FramedRead</code>. An implementation of <code>Decoder</code> takes a byte stream that has
already been buffered in <code>src</code> and decodes the data into a stream of
<code>Self::Item</code> frames.</p>
<p>Implementations are able to track state on <code>self</code>, which enables
implementing stateful streaming parsers. In many cases, though, this type
will simply be a unit struct (e.g. <code>struct HttpDecoder</code>).</p>
</div>
<h2 id='associated-types' class='small-section-header'>
Associated Types<a href='#associated-types' class='anchor'></a>
</h2>
<div class='methods'>
<h3 id='associatedtype.Item' class='method'><span id='Item.t' class='invisible'><code>type <a href='#associatedtype.Item' class="type">Item</a></code></span></h3><div class='docblock'><p>The type of decoded frames.</p>
</div><h3 id='associatedtype.Error' class='method'><span id='Error.t' class='invisible'><code>type <a href='#associatedtype.Error' class="type">Error</a>: <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.From.html" title="trait core::convert::From">From</a>&lt;<a class="struct" href="https://doc.rust-lang.org/nightly/std/io/error/struct.Error.html" title="struct std::io::error::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>The type of unrecoverable frame decoding errors.</p>
<p>If an individual message is ill-formed but can be ignored without
interfering with the processing of future messages, it may be more
useful to report the failure as an <code>Item</code>.</p>
<p><code>From&lt;io::Error&gt;</code> is required in the interest of making <code>Error</code> suitable
for returning directly from a <code>FramedRead</code>, and to enable the default
implementation of <code>decode_eof</code> to yield an <code>io::Error</code> when the decoder
fails to consume all available data.</p>
<p>Note that implementors of this trait can simply indicate <code>type Error = io::Error</code> to use I/O errors as this type.</p>
</div></div>
<h2 id='required-methods' class='small-section-header'>
Required Methods<a href='#required-methods' class='anchor'></a>
</h2>
<div class='methods'>
<h3 id='tymethod.decode' class='method'><span id='decode.v' class='invisible'><code>fn <a href='#tymethod.decode' class='fnname'>decode</a>(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;src: &amp;mut <a class="struct" href="../bytes/bytes/struct.BytesMut.html" title="struct bytes::bytes::BytesMut">BytesMut</a><br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="enum" href="https://doc.rust-lang.org/nightly/core/option/enum.Option.html" title="enum core::option::Option">Option</a>&lt;Self::<a class="type" href="../tokio_codec/trait.Decoder.html#associatedtype.Item" title="type tokio_codec::Decoder::Item">Item</a>&gt;, Self::<a class="type" href="../tokio_codec/trait.Decoder.html#associatedtype.Error" title="type tokio_codec::Decoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Attempts to decode a frame from the provided buffer of bytes.</p>
<p>This method is called by <code>FramedRead</code> whenever bytes are ready to be
parsed. The provided buffer of bytes is what's been read so far, and
this instance of <code>Decode</code> can determine whether an entire frame is in
the buffer and is ready to be returned.</p>
<p>If an entire frame is available, then this instance will remove those
bytes from the buffer provided and return them as a decoded
frame. Note that removing bytes from the provided buffer doesn't always
necessarily copy the bytes, so this should be an efficient operation in
most circumstances.</p>
<p>If the bytes look valid, but a frame isn't fully available yet, then
<code>Ok(None)</code> is returned. This indicates to the <code>Framed</code> instance that
it needs to read some more bytes before calling this method again.</p>
<p>Note that the bytes provided may be empty. If a previous call to
<code>decode</code> consumed all the bytes in the buffer then <code>decode</code> will be
called again until it returns <code>None</code>, indicating that more bytes need to
be read.</p>
<p>Finally, if the bytes in the buffer are malformed then an error is
returned indicating why. This informs <code>Framed</code> that the stream is now
corrupt and should be terminated.</p>
</div></div>
<h2 id='provided-methods' class='small-section-header'>
Provided Methods<a href='#provided-methods' class='anchor'></a>
</h2>
<div class='methods'>
<h3 id='method.decode_eof' class='method'><span id='decode_eof.v' class='invisible'><code>fn <a href='#method.decode_eof' class='fnname'>decode_eof</a>(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;buf: &amp;mut <a class="struct" href="../bytes/bytes/struct.BytesMut.html" title="struct bytes::bytes::BytesMut">BytesMut</a><br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="enum" href="https://doc.rust-lang.org/nightly/core/option/enum.Option.html" title="enum core::option::Option">Option</a>&lt;Self::<a class="type" href="../tokio_codec/trait.Decoder.html#associatedtype.Item" title="type tokio_codec::Decoder::Item">Item</a>&gt;, Self::<a class="type" href="../tokio_codec/trait.Decoder.html#associatedtype.Error" title="type tokio_codec::Decoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>A default method available to be called when there are no more bytes
available to be read from the underlying I/O.</p>
<p>This method defaults to calling <code>decode</code> and returns an error if
<code>Ok(None)</code> is returned while there is unconsumed data in <code>buf</code>.
Typically this doesn't need to be implemented unless the framing
protocol differs near the end of the stream.</p>
<p>Note that the <code>buf</code> argument may be empty. If a previous call to
<code>decode_eof</code> consumed all the bytes in the buffer, <code>decode_eof</code> will be
called again until it returns <code>None</code>, indicating that there are no more
frames to yield. This behavior enables returning finalization frames
that may not be based on inbound data.</p>
</div><h3 id='method.framed' class='method'><span id='framed.v' class='invisible'><code>fn <a href='#method.framed' class='fnname'>framed</a>&lt;T&gt;(self, io: T) -&gt; <a class="struct" href="../tokio_codec/struct.Framed.html" title="struct tokio_codec::Framed">Framed</a>&lt;T, Self&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;Self: <a class="trait" href="../tokio_codec/trait.Encoder.html" title="trait tokio_codec::Encoder">Encoder</a>,<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="../tokio_io/async_read/trait.AsyncRead.html" title="trait tokio_io::async_read::AsyncRead">AsyncRead</a> + <a class="trait" href="../tokio_io/async_write/trait.AsyncWrite.html" title="trait tokio_io::async_write::AsyncWrite">AsyncWrite</a>,&nbsp;</span></code></span></h3><div class='docblock'><p>Provides a <code>Stream</code> and <code>Sink</code> interface for reading and writing to this
<code>Io</code> object, using <code>Decode</code> and <code>Encode</code> to read and write the raw data.</p>
<p>Raw I/O objects work with byte sequences, but higher-level code usually
wants to batch these into meaningful chunks, called &quot;frames&quot;. This
method layers framing on top of an I/O object, by using the <code>Codec</code>
traits to handle encoding and decoding of messages frames. Note that
the incoming and outgoing frame types may be distinct.</p>
<p>This function returns a <em>single</em> object that is both <code>Stream</code> and
<code>Sink</code>; grouping this into a single object is often useful for layering
things like gzip or TLS, which require both read and write access to the
underlying object.</p>
<p>If you want to work more directly with the streams and sink, consider
calling <code>split</code> on the <code>Framed</code> returned by this method, which will
break them into separate objects, allowing them to interact more easily.</p>
</div></div>
<h2 id='implementors' class='small-section-header'>
Implementors<a href='#implementors' class='anchor'></a>
</h2>
<ul class='item-list' id='implementors-list'>
<li><table class='table-display'><tbody><tr><td><code>impl Decoder for <a class="struct" href="../tokio_codec/struct.BytesCodec.html" title="struct tokio_codec::BytesCodec">BytesCodec</a><span class="where fmt-newline"> type <a href='#associatedtype.Item' class="type">Item</a> = <a class="struct" href="../bytes/bytes/struct.BytesMut.html" title="struct bytes::bytes::BytesMut">BytesMut</a>;</span><span class="where fmt-newline"> type <a href='#associatedtype.Error' class="type">Error</a> = <a class="struct" href="https://doc.rust-lang.org/nightly/std/io/error/struct.Error.html" title="struct std::io::error::Error">Error</a>;</span></code><td><div class='out-of-band'><a class='srclink' href='../src/tokio_codec/bytes_codec.rs.html#14-26' title='goto source code'>[src]</a></div></td></tr></tbody></table></li>
<li><table class='table-display'><tbody><tr><td><code>impl Decoder for <a class="struct" href="../tokio_codec/struct.LinesCodec.html" title="struct tokio_codec::LinesCodec">LinesCodec</a><span class="where fmt-newline"> type <a href='#associatedtype.Item' class="type">Item</a> = <a class="struct" href="https://doc.rust-lang.org/nightly/alloc/string/struct.String.html" title="struct alloc::string::String">String</a>;</span><span class="where fmt-newline"> type <a href='#associatedtype.Error' class="type">Error</a> = <a class="struct" href="https://doc.rust-lang.org/nightly/std/io/error/struct.Error.html" title="struct std::io::error::Error">Error</a>;</span></code><td><div class='out-of-band'><a class='srclink' href='../src/tokio_codec/lines_codec.rs.html#39-77' title='goto source code'>[src]</a></div></td></tr></tbody></table></li>
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