Initial commit, new website system

author: Loïc Hoguin <[email protected]> 2016-03-28 15:36:42 +0200
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+<div id="contents" class="two_col">
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+<div id="docs" class="span9 maincol">
+
+<h1 class="lined-header"><span>Reading the request body</span></h1>
+
+<div class="paragraph"><p>The Req object also allows you to read the request body.</p></div>
+<div class="paragraph"><p>Because the request body can be of any size, all body
+reading operations will only work once, as Cowboy will
+not cache the result of these operations.</p></div>
+<div class="paragraph"><p>Cowboy will not attempt to read the body until you do.
+If handler execution ends without reading it, Cowboy
+will simply skip it.</p></div>
+<div class="paragraph"><p>Cowboy provides different ways to read the request body.
+You can read it directly, stream it, but also read and
+parse in a single call for form urlencoded formats or
+multipart. All of these except multipart are covered in
+this chapter. Multipart is covered later on in the guide.</p></div>
+<div class="sect1">
+<h2 id="_check_for_request_body">Check for request body</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>You can check whether a body was sent with the request.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">cowboy_req:has_body</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>It will return <code>true</code> if there is a request body, and
+<code>false</code> otherwise.</p></div>
+<div class="paragraph"><p>Note that it is generally safe to assume that a body is
+sent for <code>POST</code>, <code>PUT</code> and <code>PATCH</code> requests, without
+having to explicitly check for it.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_request_body_length">Request body length</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>You can obtain the body length if it was sent with the
+request.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #009900">Length</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:body_length</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>The value returned will be <code>undefined</code> if the length
+couldn&#8217;t be figured out from the request headers. If
+there&#8217;s a body but no length is given, this means that
+the chunked transfer-encoding was used. You can read
+chunked bodies by using the stream functions.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_reading_the_body">Reading the body</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>You can read the whole body directly in one call.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #FF6600">ok</span>, <span style="color: #009900">Body</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:body</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>By default, Cowboy will attempt to read up to a
+size of 8MB. You can override this limit as needed.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #FF6600">ok</span>, <span style="color: #009900">Body</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:body</span></span>(<span style="color: #009900">Req</span>, [{<span style="font-weight: bold"><span style="color: #000080">length</span></span>, <span style="color: #993399">100000000</span>}])<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>You can also disable it.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #FF6600">ok</span>, <span style="color: #009900">Body</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:body</span></span>(<span style="color: #009900">Req</span>, [{<span style="font-weight: bold"><span style="color: #000080">length</span></span>, <span style="color: #FF6600">infinity</span>}])<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>It is recommended that you do not disable it for public
+facing websites.</p></div>
+<div class="paragraph"><p>If the body is larger than the limit, then Cowboy will return
+a <code>more</code> tuple instead, allowing you to stream it if you
+would like to.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_streaming_the_body">Streaming the body</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>You can stream the request body by chunks.</p></div>
+<div class="paragraph"><p>Cowboy returns a <code>more</code> tuple when there is more body to
+be read, and an <code>ok</code> tuple for the last chunk. This allows
+you to loop over all chunks.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">body_to_console</span></span>(<span style="color: #009900">Req</span>) <span style="color: #990000">-&gt;</span>
+    <span style="font-weight: bold"><span style="color: #0000FF">case</span></span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:body</span></span>(<span style="color: #009900">Req</span>) <span style="font-weight: bold"><span style="color: #0000FF">of</span></span>
+        {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Data</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">-&gt;</span>
+            <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"~s"</span>, [<span style="color: #009900">Data</span>]),
+            <span style="color: #009900">Req2</span>;
+        {<span style="color: #FF6600">more</span>, <span style="color: #009900">Data</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">-&gt;</span>
+            <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"~s"</span>, [<span style="color: #009900">Data</span>]),
+            <span style="font-weight: bold"><span style="color: #000000">body_to_console</span></span>(<span style="color: #009900">Req2</span>)
+    <span style="font-weight: bold"><span style="color: #0000FF">end</span></span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>You can of course set the <code>length</code> option to configure the
+size of chunks.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_rate_of_data_transmission">Rate of data transmission</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>You can control the rate of data transmission by setting
+options when calling body functions. This applies not only
+to the functions described in this chapter, but also to
+the multipart functions.</p></div>
+<div class="paragraph"><p>The <code>read_length</code> option defines the maximum amount of data
+to be received from the socket at once, in bytes.</p></div>
+<div class="paragraph"><p>The <code>read_timeout</code> option defines the time Cowboy waits
+before that amount is received, in milliseconds.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_transfer_and_content_decoding">Transfer and content decoding</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Cowboy will by default decode the chunked transfer-encoding
+if any. It will not decode any content-encoding by default.</p></div>
+<div class="paragraph"><p>The first time you call a body function you can set the
+<code>transfer_decode</code> and <code>content_decode</code> options. If the body
+was already started being read these options are simply
+ignored.</p></div>
+<div class="paragraph"><p>The following example shows how to set both options.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #FF6600">ok</span>, <span style="color: #009900">Data</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:body</span></span>(<span style="color: #009900">Req</span>, [
+    {<span style="color: #FF6600">transfer_decode</span>, <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> <span style="font-weight: bold"><span style="color: #000000">transfer_decode</span></span><span style="color: #990000">/</span><span style="color: #993399">2</span>, <span style="color: #009900">TransferState</span>},
+    {<span style="color: #FF6600">content_decode</span>, <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> <span style="font-weight: bold"><span style="color: #000000">content_decode</span></span><span style="color: #990000">/</span><span style="color: #993399">1</span>}
+])<span style="color: #990000">.</span></tt></pre></div></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_reading_a_form_urlencoded_body">Reading a form urlencoded body</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>You can directly obtain a list of key/value pairs if the
+body was sent using the application/x-www-form-urlencoded
+content-type.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #FF6600">ok</span>, <span style="color: #009900">KeyValues</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:body_qs</span></span>(<span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>You can then retrieve an individual value from that list.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #990000">_</span>, <span style="color: #009900">Lang</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">lists:keyfind</span></span>(<span style="color: #FF6600">lang</span>, <span style="color: #993399">1</span>, <span style="color: #009900">KeyValues</span>)<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>You should not attempt to match on the list as the order
+of the values is undefined.</p></div>
+<div class="paragraph"><p>By default Cowboy will reject bodies with a size above
+64KB when using this function. You can override this limit
+by setting the <code>length</code> option.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #FF6600">ok</span>, <span style="color: #009900">KeyValues</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:body_qs</span></span>(<span style="color: #009900">Req</span>, [{<span style="font-weight: bold"><span style="color: #000080">length</span></span>, <span style="color: #993399">2000000</span>}])<span style="color: #990000">.</span></tt></pre></div></div>
+</div>
+</div>
+
+
+
+</div>
+
+<div class="span3 sidecol">
+
+
+<h3>
+	Cowboy
+	2.0
+	
+	User Guide
+</h3>
+
+<ul>
+	
+		<li><a href="/docs/en/cowboy/2.0/guide">User Guide</a></li>
+	
+	
+		<li><a href="/docs/en/cowboy/2.0/manual">Function Reference</a></li>
+	
+	
+</ul>
+
+<h4 id="docs-nav">Navigation</h4>
+
+<h4>Version select</h4>
+<ul>
+	
+	
+	
+		<li><a href="/docs/en/cowboy/1.0/guide">1.0</a></li>
+	
+		<li><a href="/docs/en/cowboy/2.0/guide">2.0</a></li>
+	
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+
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author	Loïc Hoguin <[email protected]>	2016-03-28 15:36:42 +0200
committer	Loïc Hoguin <[email protected]>	2016-03-28 15:36:42 +0200
commit	fe3492a98de29942477b061cd02c92246f4bf85a (patch)
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