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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) | |
| tree | 2255b796a657e6e4dfb72beec1141258d17f1220 /docs/en/cowboy/2.0/guide/multipart | |
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Initial commit, new website system
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diff --git a/docs/en/cowboy/2.0/guide/multipart/index.html b/docs/en/cowboy/2.0/guide/multipart/index.html new file mode 100644 index 00000000..2a443f10 --- /dev/null +++ b/docs/en/cowboy/2.0/guide/multipart/index.html @@ -0,0 +1,305 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Multipart requests</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li class="active"><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents" class="two_col"> +<div class="container"> +<div class="row"> +<div id="docs" class="span9 maincol"> + +<h1 class="lined-header"><span>Multipart requests</span></h1> + +<div class="paragraph"><p>Multipart originates from MIME, an Internet standard that
+extends the format of emails. Multipart messages are a
+container for parts of any content-type.</p></div>
+<div class="paragraph"><p>For example, a multipart message may have a part
+containing text and a second part containing an
+image. This is what allows you to attach files
+to emails.</p></div>
+<div class="paragraph"><p>In the context of HTTP, multipart is most often used
+with the <code>multipart/form-data</code> content-type. This is
+the content-type you have to use when you want browsers
+to be allowed to upload files through HTML forms.</p></div>
+<div class="paragraph"><p>Multipart is of course not required for uploading
+files, it is only required when you want to do so
+through HTML forms.</p></div>
+<div class="paragraph"><p>You can read and parse multipart messages using the
+Req object directly.</p></div>
+<div class="paragraph"><p>Cowboy defines two functions that allows you to get
+information about each part and read their contents.</p></div>
+<div class="sect1">
+<h2 id="_structure">Structure</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>A multipart message is a list of parts. Parts may
+contain either a multipart message or a non-multipart
+content-type. This allows parts to be arranged in a
+tree structure, although this is a rare case as far
+as the Web is concerned.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_form_data">Form-data</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>In the normal case, when a form is submitted, the
+browser will use the <code>application/x-www-form-urlencoded</code>
+content-type. This type is just a list of keys and
+values and is therefore not fit for uploading files.</p></div>
+<div class="paragraph"><p>That’s where the <code>multipart/form-data</code> content-type
+comes in. When the form is configured to use this
+content-type, the browser will use one part of the
+message for each form field. This means that a file
+input field will be sent in its own part, but the
+same applies to all other kinds of fields.</p></div>
+<div class="paragraph"><p>A form with a text input, a file input and a select
+choice box will result in a multipart message with
+three parts, one for each field.</p></div>
+<div class="paragraph"><p>The browser does its best to determine the content-type
+of the files it sends this way, but you should not
+rely on it for determining the contents of the file.
+Proper investigation of the contents is recommended.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_checking_the_content_type">Checking the content-type</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>While there is a variety of multipart messages, the
+most common on the Web is <code>multipart/form-data</code>. It’s
+the type of message being sent when an HTML form
+allows uploading files.</p></div>
+<div class="paragraph"><p>You can quickly figure out if a multipart message
+has been sent by parsing the <code>content-type</code> header.</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: #FF0000">"multipart"</span><span style="color: #990000">>></span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"form-data"</span><span style="color: #990000">>></span>, <span style="color: #990000">_</span>}
+ <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:parse_header</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_reading_a_multipart_message">Reading a multipart message</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>To read a message you have to iterate over all its
+parts. Then, for each part, you can inspect its headers
+and read its body.</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">multipart</span></span>(<span style="color: #009900">Req</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #0000FF">case</span></span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:part</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">_Headers</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">-></span>
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">_Body</span>, <span style="color: #009900">Req3</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:part_body</span></span>(<span style="color: #009900">Req2</span>),
+ <span style="font-weight: bold"><span style="color: #000000">multipart</span></span>(<span style="color: #009900">Req3</span>);
+ {<span style="color: #FF6600">done</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">-></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>Parts do not have a size limit. When a part body is
+too big, Cowboy will return what it read so far and
+allow you to continue if you wish to do so.</p></div>
+<div class="paragraph"><p>The function <code>cow_multipart:form_data/1</code> can be used
+to quickly obtain information about a part from a
+<code>multipart/form-data</code> message. This function will
+tell you if the part is for a normal field or if it
+is a file being uploaded.</p></div>
+<div class="paragraph"><p>This can be used for example to allow large part bodies
+for files but crash when a normal field is too large.</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">multipart</span></span>(<span style="color: #009900">Req</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #0000FF">case</span></span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:part</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">Headers</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">-></span>
+ <span style="color: #009900">Req4</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #0000FF">case</span></span> <span style="font-weight: bold"><span style="color: #000000">cow_multipart:form_data</span></span>(<span style="color: #009900">Headers</span>) <span style="font-weight: bold"><span style="color: #0000FF">of</span></span>
+ {<span style="color: #FF6600">data</span>, <span style="color: #009900">_FieldName</span>} <span style="color: #990000">-></span>
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">_Body</span>, <span style="color: #009900">Req3</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:part_body</span></span>(<span style="color: #009900">Req2</span>),
+ <span style="color: #009900">Req3</span>;
+ {<span style="color: #FF6600">file</span>, <span style="color: #009900">_FieldName</span>, <span style="color: #009900">_Filename</span>, <span style="color: #009900">_CType</span>, <span style="color: #009900">_CTransferEncoding</span>} <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">stream_file</span></span>(<span style="color: #009900">Req2</span>)
+ <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>,
+ <span style="font-weight: bold"><span style="color: #000000">multipart</span></span>(<span style="color: #009900">Req4</span>);
+ {<span style="color: #FF6600">done</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">-></span>
+ <span style="color: #009900">Req2</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">end</span></span><span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">stream_file</span></span>(<span style="color: #009900">Req</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #0000FF">case</span></span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:part_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">_Body</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">-></span>
+ <span style="color: #009900">Req2</span>;
+ {<span style="color: #FF6600">more</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">stream_file</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>By default the body chunk Cowboy will return is limited
+to 8MB. This can of course be overriden. Both functions
+can take a second argument, the same list of options that
+will be passed to <code>cowboy_req:body/2</code> function.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_skipping_unwanted_parts">Skipping unwanted parts</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>If you do not want to read a part’s body, you can skip it.
+Skipping is easy. If you do not call the function to read
+the part’s body, Cowboy will automatically skip it when
+you request the next part.</p></div>
+<div class="paragraph"><p>The following snippet reads all part headers and skips
+all bodies:</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">multipart</span></span>(<span style="color: #009900">Req</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #0000FF">case</span></span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:part</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">_Headers</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">multipart</span></span>(<span style="color: #009900">Req2</span>);
+ {<span style="color: #FF6600">done</span>, <span style="color: #009900">Req2</span>} <span style="color: #990000">-></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>Similarly, if you start reading the body and it ends up
+being too big, you can simply continue with the next part,
+Cowboy will automatically skip what remains.</p></div>
+<div class="paragraph"><p>Note that the skipping rate may not be adequate for your
+application. If you observe poor performance when skipping,
+you might want to consider manually skipping by calling
+the <code>cowboy_req:part_body/1</code> function directly.</p></div>
+<div class="paragraph"><p>And if you started reading the message but decide that you
+do not need the remaining parts, you can simply stop reading
+entirely and Cowboy will automatically figure out what to do.</p></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> + +</ul> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + + |