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<title>Read from a file descriptor at given offset.</title>
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<h1 class="refname">eio_read</h1>
<p class="verinfo">(PECL eio >= 0.0.1dev)</p><p class="refpurpose"><span class="refname">eio_read</span> — <span class="dc-title">Read from a file descriptor at given offset.</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.eio-read-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">resource</span> <span class="methodname"><strong>eio_read</strong></span>
( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$fd</code></span>
, <span class="methodparam"><span class="type">int</span> <code class="parameter">$length</code></span>
, <span class="methodparam"><span class="type">int</span> <code class="parameter">$offset</code></span>
, <span class="methodparam"><span class="type">int</span> <code class="parameter">$pri</code></span>
, <span class="methodparam"><span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span> <code class="parameter">$callback</code></span>
[, <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$data</code><span class="initializer"> = NULL</span></span>
] )</div>
<p class="para rdfs-comment">
<span class="function"><strong>eio_read()</strong></span> reads up to <em><code class="parameter">length</code></em>
bytes from <em><code class="parameter">fd</code></em> file descriptor at
<em><code class="parameter">offset</code></em>. The read bytes are stored in
<em><code class="parameter">result</code></em> argument of <em><code class="parameter">callback</code></em>.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.eio-read-parameters">
<h3 class="title">Parameters</h3>
<dl>
<dt>
<span class="term"><em><code class="parameter">fd</code></em></span>
<dd>
<p class="para">
Stream, Socket resource, or numeric file descriptor
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">length</code></em></span>
<dd>
<p class="para">
Maximum number of bytes to read.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">offset</code></em></span>
<dd>
<p class="para">
Offset within the file.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">pri</code></em></span>
<dd>
<p class="para">The request priority: <strong><code>EIO_PRI_DEFAULT</code></strong>, <strong><code>EIO_PRI_MIN</code></strong>, <strong><code>EIO_PRI_MAX</code></strong>, or <strong><code>NULL</code></strong>.
If <strong><code>NULL</code></strong> passed, <em><code class="parameter">pri</code></em> internally is set to
<strong><code>EIO_PRI_DEFAULT</code></strong>.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">callback</code></em></span>
<dd>
<p class="para">
<em><code class="parameter">callback</code></em> function is called when the request is done.
It should match the following prototype: <div class="example-contents"><div class="phpcode"><code><span style="color: #000000">
void callback(mixed $data, int $result[, resource $req]);</span>
</code></div></div>
<dl>
<dt>
<span class="term"><em><code class="parameter">data</code></em></span>
<dd>
<p class="para">is custom data passed to the request.</p></dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">result</code></em></span>
<dd>
<p class="para">request-specific result value; basically, the value returned by corresponding
system call.</p></dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">req</code></em></span>
<dd>
<p class="para">is optional request resource which can be used with functions like <span class="function"><a href="function.eio-get-last-error.html" class="function">eio_get_last_error()</a></span></p></dd>
</dt>
</dl>
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">data</code></em></span>
<dd>
<p class="para">
Arbitrary variable passed to <em><code class="parameter">callback</code></em>.
</p>
</dd>
</dt>
</dl>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.eio-read-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
<span class="function"><strong>eio_read()</strong></span> stores read bytes in
<em><code class="parameter">result</code></em> argument of <em><code class="parameter">callback</code></em>
function.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.eio-read-examples">
<h3 class="title">Examples</h3>
<div class="example" id="example-3601">
<p><strong>Example #1 <span class="function"><strong>eio_read()</strong></span> example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// Open a temporary file and write some bytes there<br /></span><span style="color: #0000BB">$temp_filename </span><span style="color: #007700">= </span><span style="color: #DD0000">"eio-temp-file.tmp"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$fp </span><span style="color: #007700">= </span><span style="color: #0000BB">fopen</span><span style="color: #007700">(</span><span style="color: #0000BB">$temp_filename</span><span style="color: #007700">, </span><span style="color: #DD0000">"w"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">fwrite</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">, </span><span style="color: #DD0000">"1234567890"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">fclose</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* Is called when eio_read() is done */<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">my_read_cb</span><span style="color: #007700">(</span><span style="color: #0000BB">$data</span><span style="color: #007700">, </span><span style="color: #0000BB">$result</span><span style="color: #007700">) {<br /> global </span><span style="color: #0000BB">$temp_filename</span><span style="color: #007700">;<br /><br /> </span><span style="color: #FF8000">// Output read bytes<br /> </span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$result</span><span style="color: #007700">);<br /><br /> </span><span style="color: #FF8000">// Close file<br /> </span><span style="color: #0000BB">eio_close</span><span style="color: #007700">(</span><span style="color: #0000BB">$data</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">eio_event_loop</span><span style="color: #007700">();<br /><br /> </span><span style="color: #FF8000">// Remove temporary file<br /> </span><span style="color: #007700">@</span><span style="color: #0000BB">unlink</span><span style="color: #007700">(</span><span style="color: #0000BB">$temp_filename</span><span style="color: #007700">);<br />}<br /><br /></span><span style="color: #FF8000">/* Is called when eio_open() is done */<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">my_file_opened_callback</span><span style="color: #007700">(</span><span style="color: #0000BB">$data</span><span style="color: #007700">, </span><span style="color: #0000BB">$result</span><span style="color: #007700">) {<br /> </span><span style="color: #FF8000">// $result should contain the file descriptor<br /> </span><span style="color: #007700">if (</span><span style="color: #0000BB">$result </span><span style="color: #007700">> </span><span style="color: #0000BB">0</span><span style="color: #007700">) {<br /> </span><span style="color: #FF8000">// Read 5 bytes starting from third<br /> </span><span style="color: #0000BB">eio_read</span><span style="color: #007700">(</span><span style="color: #0000BB">$result</span><span style="color: #007700">, </span><span style="color: #0000BB">5</span><span style="color: #007700">, </span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">EIO_PRI_DEFAULT</span><span style="color: #007700">, </span><span style="color: #DD0000">"my_read_cb"</span><span style="color: #007700">, </span><span style="color: #0000BB">$result</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">eio_event_loop</span><span style="color: #007700">();<br /> } else {<br /> </span><span style="color: #FF8000">// eio_open() failed<br /> </span><span style="color: #0000BB">unlink</span><span style="color: #007700">(</span><span style="color: #0000BB">$data</span><span style="color: #007700">);<br /> }<br />}<br /><br /></span><span style="color: #FF8000">// Open the file for reading and writing<br /></span><span style="color: #0000BB">eio_open</span><span style="color: #007700">(</span><span style="color: #0000BB">$temp_filename</span><span style="color: #007700">, </span><span style="color: #0000BB">EIO_O_RDWR</span><span style="color: #007700">, </span><span style="color: #0000BB">NULL</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">EIO_PRI_DEFAULT</span><span style="color: #007700">, </span><span style="color: #DD0000">"my_file_opened_callback"</span><span style="color: #007700">, </span><span style="color: #0000BB">$temp_filename</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">eio_event_loop</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output
something similar to:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
string(5) "34567"
</pre></div>
</div>
</div>
</div>
<div class="refsect1 seealso" id="refsect1-function.eio-read-seealso">
<h3 class="title">See Also</h3>
<ul class="simplelist">
<li class="member">eio_open</li>
<li class="member">eio_write</li>
<li class="member">eio_close</li>
<li class="member">eio_event_loop</li>
</ul>
</div>
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