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| author | Loïc Hoguin <[email protected]> | 2017-10-03 13:39:41 +0200 |
|---|---|---|
| committer | Loïc Hoguin <[email protected]> | 2017-10-03 13:39:41 +0200 |
| commit | b5d4cb91f80c833795a2d87050c3674bb7aecdc5 (patch) | |
| tree | 62bf0ad8326006fcd3407fcb7c34c844c0dc0874 /docs/en/cowboy/2.0/guide/multipart/index.html | |
| parent | 1f8d51dd2692fc3978080419987bbe4d49a41a90 (diff) | |
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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 index cc53b55d..4f173126 100644 --- a/docs/en/cowboy/2.0/guide/multipart/index.html +++ b/docs/en/cowboy/2.0/guide/multipart/index.html @@ -7,7 +7,7 @@ <meta name="description" content=""> <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> - <meta name="generator" content="Hugo 0.17" /> + <meta name="generator" content="Hugo 0.26" /> <title>Nine Nines: Multipart requests</title> @@ -67,175 +67,178 @@ <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 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>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 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">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 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">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">_Body</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">_Body</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 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: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 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: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 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">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>
+<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 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>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 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">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 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">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 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: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 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: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 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">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"> |