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<h1 class='fqn'><span class='in-band'>Crate <a class="mod" href=''>serde_cbor</a></span><span class='out-of-band'><span id='render-detail'>
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</span><a class='srclink' href='../src/serde_cbor/lib.rs.html#1-147' title='goto source code'>[src]</a></span></h1>
<div class='docblock'><p>CBOR and serialization.</p>
<h1 id="what-is-cbor" class="section-header"><a href="#what-is-cbor">What is CBOR?</a></h1>
<p><a href="http://cbor.io">CBOR</a> is a way to encode data in a space-efficient and fast binary format.
CBORs data-model is a superset of the JSONs.</p>
<p>A simple object describing a person in diagnostic notation (it is actually JSON plus some
annotations) looks like</p>
<pre><code class="language-json">{
&quot;FirstName&quot;: &quot;John&quot;,
&quot;LastName&quot;: &quot;Doe&quot;,
&quot;Age&quot;: 43,
&quot;Address&quot;: {
&quot;Street&quot;: &quot;Downing Street 10&quot;,
&quot;City&quot;: &quot;London&quot;,
&quot;Country&quot;: &quot;Great Britain&quot;
},
&quot;PhoneNumbers&quot;: [
&quot;+44 1234567&quot;,
&quot;+44 2345678&quot;
]
}
</code></pre>
<p>The CBOR encoded object with comments in hexadecimal notation looks like</p>
<pre><code class="language-cbor">a5 # map(5)
69 # text(9)
46697273744e616d65 # &quot;FirstName&quot;
64 # text(4)
4a6f686e # &quot;John&quot;
68 # text(8)
4c6173744e616d65 # &quot;LastName&quot;
63 # text(3)
446f65 # &quot;Doe&quot;
63 # text(3)
416765 # &quot;Age&quot;
18 2b # unsigned(43)
67 # text(7)
41646472657373 # &quot;Address&quot;
a3 # map(3)
66 # text(6)
537472656574 # &quot;Street&quot;
71 # text(17)
446f776e696e6720537472656574203130 # &quot;Downing Street 10&quot;
64 # text(4)
43697479 # &quot;City&quot;
66 # text(6)
4c6f6e646f6e # &quot;London&quot;
67 # text(7)
436f756e747279 # &quot;Country&quot;
6d # text(13)
4772656174204272697461696e # &quot;Great Britain&quot;
6c # text(12)
50686f6e654e756d62657273 # &quot;PhoneNumbers&quot;
82 # array(2)
6b # text(11)
2b34342031323334353637 # &quot;+44 1234567&quot;
6b # text(11)
2b34342032333435363738 # &quot;+44 2345678&quot;
</code></pre>
<p>While the JSON encoding is 174 bytes long the CBOR representation is only 141 bytes long.
This is 19% shorter! Sometimes compression will even better, but never CBOR will be longer
than the corresponding JSON. More importantly CBOR supports binary data, custom data tyes,
annotations for dates, times and expected encoding and is faster to serialize and deserialize.
It can even be used on embedded devices.</p>
<h1 id="type-based-serialization-and-deserialization" class="section-header"><a href="#type-based-serialization-and-deserialization">Type-based Serialization and Deserialization</a></h1>
<p>Serde provides a mechanism for low boilerplate serialization &amp; deserialization of values to and
from CBOR via the serialization API. To be able to serialize a piece of data, it must implement
the <code>serde::Serialize</code> trait. To be able to deserialize a piece of data, it must implement the
<code>serde::Deserialize</code> trait. Serde provides an annotation to automatically generate the
code for these traits: <code>#[derive(Serialize, Deserialize)]</code>.</p>
<p>The CBOR API also provides an enum <code>serde_cbor::Value</code>.</p>
<h1 id="packed-encoding" class="section-header"><a href="#packed-encoding">Packed Encoding</a></h1>
<p>When serializing structs or enums in CBOR the keys or enum variant names will be serialized
as string keys to a map. Esspecially in embedded environments this can increase the file
size too much. In packed encoding the keys and variants will be serialized as variable sized
integers. The first 24 entries in any struct consume only a single byte!
To serialize a document in packed encoding use <code>ser::to_(vec|writer)_packed</code>, deserialization
works without any changes.</p>
<h1 id="self-describing-documents" class="section-header"><a href="#self-describing-documents">Self describing documents</a></h1>
<p>In some contexts different formats are used but there is no way to declare the format used
out of band. For this reason CBOR has a magic number that may be added before any document.
The <em><code>_sd</code> (for <em>s</em>elf</em>d*escribe) append the magic number before documents.</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<p>Read a CBOR value that is known to be a map of string keys to string values and print it.</p>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">collections</span>::<span class="ident">BTreeMap</span>;
<span class="kw">use</span> <span class="ident">serde_cbor</span>::<span class="ident">from_slice</span>;
<span class="kw">let</span> <span class="ident">slice</span> <span class="op">=</span> <span class="string">b&quot;\xa5aaaAabaBacaCadaDaeaE&quot;</span>;
<span class="kw">let</span> <span class="ident">value</span>: <span class="ident">BTreeMap</span><span class="op">&lt;</span><span class="ident">String</span>, <span class="ident">String</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">from_slice</span>(<span class="ident">slice</span>).<span class="ident">unwrap</span>();
<span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">value</span>); <span class="comment">// {&quot;e&quot;: &quot;E&quot;, &quot;d&quot;: &quot;D&quot;, &quot;a&quot;: &quot;A&quot;, &quot;c&quot;: &quot;C&quot;, &quot;b&quot;: &quot;B&quot;}</span></pre>
<p>Read a general CBOR value with an unknown content.</p>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">serde_cbor</span>::{<span class="ident">from_slice</span>, <span class="ident">Value</span>};
<span class="kw">let</span> <span class="ident">slice</span> <span class="op">=</span> <span class="string">b&quot;\x82\x01\xa1aaab&quot;</span>;
<span class="kw">let</span> <span class="ident">value</span>: <span class="ident">Value</span> <span class="op">=</span> <span class="ident">from_slice</span>(<span class="ident">slice</span>).<span class="ident">unwrap</span>();
<span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">value</span>); <span class="comment">// Array([U64(1), Object({String(&quot;a&quot;): String(&quot;b&quot;)})])</span></pre>
<p>Serialize an object.</p>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">collections</span>::<span class="ident">BTreeMap</span>;
<span class="kw">use</span> <span class="ident">serde_cbor</span>::<span class="ident">to_vec</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">programming_languages</span> <span class="op">=</span> <span class="ident">BTreeMap</span>::<span class="ident">new</span>();
<span class="ident">programming_languages</span>.<span class="ident">insert</span>(<span class="string">&quot;rust&quot;</span>, <span class="macro">vec</span><span class="macro">!</span>[<span class="string">&quot;safe&quot;</span>, <span class="string">&quot;concurrent&quot;</span>, <span class="string">&quot;fast&quot;</span>]);
<span class="ident">programming_languages</span>.<span class="ident">insert</span>(<span class="string">&quot;python&quot;</span>, <span class="macro">vec</span><span class="macro">!</span>[<span class="string">&quot;powerful&quot;</span>, <span class="string">&quot;friendly&quot;</span>, <span class="string">&quot;open&quot;</span>]);
<span class="ident">programming_languages</span>.<span class="ident">insert</span>(<span class="string">&quot;js&quot;</span>, <span class="macro">vec</span><span class="macro">!</span>[<span class="string">&quot;lightweight&quot;</span>, <span class="string">&quot;interpreted&quot;</span>, <span class="string">&quot;object-oriented&quot;</span>]);
<span class="kw">let</span> <span class="ident">encoded</span> <span class="op">=</span> <span class="ident">to_vec</span>(<span class="kw-2">&amp;</span><span class="ident">programming_languages</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">encoded</span>.<span class="ident">unwrap</span>().<span class="ident">len</span>(), <span class="number">103</span>);</pre>
</div><h2 id='modules' class='section-header'><a href="#modules">Modules</a></h2>
<table>
<tr class=' module-item'>
<td><a class="mod" href="de/index.html"
title='mod serde_cbor::de'>de</a></td>
<td class='docblock-short'>
<p>Deserialization.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="mod" href="error/index.html"
title='mod serde_cbor::error'>error</a></td>
<td class='docblock-short'>
<p>When serializing or deserializing CBOR goes wrong.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="mod" href="ser/index.html"
title='mod serde_cbor::ser'>ser</a></td>
<td class='docblock-short'>
<p>Serialize a Rust data structure to CBOR data.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="mod" href="value/index.html"
title='mod serde_cbor::value'>value</a></td>
<td class='docblock-short'>
<p>CBOR values, keys and serialization routines.</p>
</td>
</tr></table><h2 id='structs' class='section-header'><a href="#structs">Structs</a></h2>
<table>
<tr class=' module-item'>
<td><a class="struct" href="struct.Deserializer.html"
title='struct serde_cbor::Deserializer'>Deserializer</a></td>
<td class='docblock-short'>
<p>A Serde <code>Deserialize</code>r of CBOR data.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.Serializer.html"
title='struct serde_cbor::Serializer'>Serializer</a></td>
<td class='docblock-short'>
<p>A structure for serializing Rust values to CBOR.</p>
</td>
</tr></table><h2 id='enums' class='section-header'><a href="#enums">Enums</a></h2>
<table>
<tr class=' module-item'>
<td><a class="enum" href="enum.ObjectKey.html"
title='enum serde_cbor::ObjectKey'>ObjectKey</a></td>
<td class='docblock-short'>
<p>A simplified CBOR value containing only types useful for keys.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="enum" href="enum.Value.html"
title='enum serde_cbor::Value'>Value</a></td>
<td class='docblock-short'>
<p>An enum over all possible CBOR types.</p>
</td>
</tr></table><h2 id='functions' class='section-header'><a href="#functions">Functions</a></h2>
<table>
<tr class=' module-item'>
<td><a class="fn" href="fn.from_reader.html"
title='fn serde_cbor::from_reader'>from_reader</a></td>
<td class='docblock-short'>
<p>Decodes a value from CBOR data in a reader.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="fn" href="fn.from_slice.html"
title='fn serde_cbor::from_slice'>from_slice</a></td>
<td class='docblock-short'>
<p>Decodes a value from CBOR data in a slice.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="fn" href="fn.to_value.html"
title='fn serde_cbor::to_value'>to_value</a></td>
<td class='docblock-short'>
<p>Convert a <code>T</code> into <code>serde_cbor::Value</code> which is an enum that can represent
any valid CBOR data.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="fn" href="fn.to_vec.html"
title='fn serde_cbor::to_vec'>to_vec</a></td>
<td class='docblock-short'>
<p>Serializes a value to a vector.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="fn" href="fn.to_writer.html"
title='fn serde_cbor::to_writer'>to_writer</a></td>
<td class='docblock-short'>
<p>Serializes a value to a writer.</p>
</td>
</tr></table></section>
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