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| author | Loïc Hoguin <[email protected]> | 2018-04-04 13:13:37 +0200 |
|---|---|---|
| committer | Loïc Hoguin <[email protected]> | 2018-04-04 13:13:37 +0200 |
| commit | d2a3f2cedd7c00d0933222aed9c06b3149aa4db4 (patch) | |
| tree | 4f1499bac639c782b250af0fbf0dec2064315813 /docs/en/cowboy/2.3/guide/multipart/index.html | |
| parent | 1d654719f5fa6be67d2c95145872068665702cb7 (diff) | |
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Cowboy 2.3.0
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diff --git a/docs/en/cowboy/2.3/guide/multipart/index.html b/docs/en/cowboy/2.3/guide/multipart/index.html new file mode 100644 index 00000000..c049ef65 --- /dev/null +++ b/docs/en/cowboy/2.3/guide/multipart/index.html @@ -0,0 +1,330 @@ +<!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 0.37.1" /> + + <title>Nine Nines: Multipart requests</title> + + <link href='https://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + <link href="/css/99s.css?r=1" 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.</p></div> +<div class="paragraph"><p>A multipart message is a list of parts. A part contains +headers and a body. The body of the parts may be +of any media type, and contain text or binary data. +It is possible for parts to contain a multipart media +type.</p></div> +<div class="paragraph"><p>In the context of HTTP, multipart is most often used +with the <code>multipart/form-data</code> media type. It is what +browsers use to upload files through HTML forms.</p></div> +<div class="paragraph"><p>The <code>multipart/byteranges</code> is also common. It is the +media type used to send arbitrary bytes from a resource, +enabling clients to resume downloads.</p></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 create a multipart +message where each part corresponds to a field on +the form. For files, it also adds some metadata in +the part headers, like the file name.</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 media 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_for_multipart_messages">Checking for multipart messages</h2> +<div class="sectionbody"> +<div class="paragraph"><p>The content-type header indicates the presence of +a multipart message:</p></div> +<div class="listingblock"> +<div class="content"><!-- Generator: GNU source-highlight +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>Cowboy provides two sets of functions for reading +request bodies as multipart messages.</p></div> +<div class="paragraph"><p>The <code>cowboy_req:read_part/1,2</code> functions return the +next part’s headers, if any.</p></div> +<div class="paragraph"><p>The <code>cowboy_req:read_part_body/1,2</code> functions return +the current part’s body. For large bodies you may +need to call the function multiple times.</p></div> +<div class="paragraph"><p>To read a multipart message you need to iterate over +all its parts:</p></div> +<div class="listingblock"> +<div class="content"><!-- Generator: GNU source-highlight +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">Req0</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:read_part</span></span>(<span style="color: #009900">Req0</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">Req1</span>} <span style="color: #990000">-></span> + {<span style="color: #FF6600">ok</span>, <span style="color: #009900">_Body</span>, <span style="color: #009900">Req</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:read_part_body</span></span>(<span style="color: #009900">Req1</span>), + <span style="font-weight: bold"><span style="color: #000000">multipart</span></span>(<span style="color: #009900">Req</span>); + {<span style="color: #FF6600">done</span>, <span style="color: #009900">Req</span>} <span style="color: #990000">-></span> + <span style="color: #009900">Req</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>When part bodies are too large, Cowboy will return +a <code>more</code> tuple, and allow you to loop until the part +body has been fully read.</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. The function returns +a <code>data</code> or a <code>file</code> tuple depending on whether this +is a normal field or a file being uploaded.</p></div> +<div class="paragraph"><p>The following snippet will use this function and +use different strategies depending on whether the +part is a file:</p></div> +<div class="listingblock"> +<div class="content"><!-- Generator: GNU source-highlight +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">Req0</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:read_part</span></span>(<span style="color: #009900">Req0</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">Req1</span>} <span style="color: #990000">-></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">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">Req2</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:read_part_body</span></span>(<span style="color: #009900">Req1</span>), + <span style="color: #009900">Req2</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: #990000">-></span> + <span style="font-weight: bold"><span style="color: #000000">stream_file</span></span>(<span style="color: #009900">Req1</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">Req</span>); + {<span style="color: #FF6600">done</span>, <span style="color: #009900">Req</span>} <span style="color: #990000">-></span> + <span style="color: #009900">Req</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">Req0</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:read_part_body</span></span>(<span style="color: #009900">Req0</span>) <span style="font-weight: bold"><span style="color: #0000FF">of</span></span> + {<span style="color: #FF6600">ok</span>, <span style="color: #009900">_LastBodyChunk</span>, <span style="color: #009900">Req</span>} <span style="color: #990000">-></span> + <span style="color: #009900">Req</span>; + {<span style="color: #FF6600">more</span>, <span style="color: #009900">_BodyChunk</span>, <span style="color: #009900">Req</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="font-weight: bold"><span style="color: #0000FF">end</span></span><span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>Both the part header and body reading functions can take +options that will be given to the request body reading +functions. By default, <code>cowboy_req:read_part/1</code> reads +up to 64KB for up to 5 seconds. <code>cowboy_req:read_part_body/1</code> +has the same defaults as <code>cowboy_req:read_body/1</code>.</p></div> +<div class="paragraph"><p>To change the defaults for part headers:</p></div> +<div class="listingblock"> +<div class="content"><!-- Generator: GNU source-highlight +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:read_part</span></span>(<span style="color: #009900">Req</span>, #{<span style="font-weight: bold"><span style="color: #000080">length</span></span> <span style="color: #990000">=></span> <span style="color: #993399">128000</span>})<span style="color: #990000">.</span></tt></pre></div></div> +<div class="paragraph"><p>And for part bodies:</p></div> +<div class="listingblock"> +<div class="content"><!-- Generator: GNU source-highlight +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:read_part_body</span></span>(<span style="color: #009900">Req</span>, #{<span style="font-weight: bold"><span style="color: #000080">length</span></span> <span style="color: #990000">=></span> <span style="color: #993399">1000000</span>, <span style="color: #0000FF">period</span> <span style="color: #990000">=></span> <span style="color: #993399">7000</span>})<span style="color: #990000">.</span></tt></pre></div></div> +</div> +</div> +<div class="sect1"> +<h2 id="_skipping_unwanted_parts">Skipping unwanted parts</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Part bodies do not have to be read. Cowboy will automatically +skip it when you request the next part’s body.</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 +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">Req0</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:read_part</span></span>(<span style="color: #009900">Req0</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">Req</span>} <span style="color: #990000">-></span> + <span style="font-weight: bold"><span style="color: #000000">multipart</span></span>(<span style="color: #009900">Req</span>); + {<span style="color: #FF6600">done</span>, <span style="color: #009900">Req</span>} <span style="color: #990000">-></span> + <span style="color: #009900">Req</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>While Cowboy can skip part bodies automatically, the read +rate is not configurable. Depending on your application +you may want to skip manually, in particular if you observe +poor performance while skipping.</p></div> +<div class="paragraph"><p>You do not have to read all parts either. You can stop +reading as soon as you find the data you need.</p></div> +</div> +</div> + + + + + + + + + + + <nav style="margin:1em 0"> + + <a style="float:left" href="https://ninenines.eu/docs/en/cowboy/2.3/guide/cookies/"> + Using cookies + </a> + + + + <a style="float:right" href="https://ninenines.eu/docs/en/cowboy/2.3/guide/rest_principles/"> + REST principles + </a> + + </nav> + + + + +</div> + +<div class="span3 sidecol"> + + +<h3> + Cowboy + 2.3 + + User Guide +</h3> + +<ul> + + <li><a href="/docs/en/cowboy/2.3/guide">User Guide</a></li> + + + <li><a href="/docs/en/cowboy/2.3/manual">Function Reference</a></li> + + +</ul> + +<h4 id="docs-nav">Navigation</h4> + +<h4>Version select</h4> +<ul> + + + + <li><a href="/docs/en/cowboy/2.3/guide">2.3</a></li> + + <li><a href="/docs/en/cowboy/2.2/guide">2.2</a></li> + + <li><a href="/docs/en/cowboy/2.1/guide">2.1</a></li> + + <li><a href="/docs/en/cowboy/2.0/guide">2.0</a></li> + + <li><a href="/docs/en/cowboy/1.0/guide">1.0</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="/js/custom.js"></script> + </body> +</html> + + |