<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Hiding blocking</title>
<meta name="generator" content="DocBook XSL Stylesheets V1.72.0">
<link rel="start" href="index.html" title="GNet Network Library Reference Manual">
<link rel="up" href="gnet-developers.html" title="GNet for developers">
<link rel="prev" href="gnet-developers-tips.html" title="Tips and tricks">
<link rel="next" href="gnet-examples.html" title="GNet Examples">
<meta name="generator" content="GTK-Doc V1.8 (XML mode)">
<link rel="stylesheet" href="style.css" type="text/css">
<link rel="chapter" href="gnet-overview.html" title="GNet Overview">
<link rel="chapter" href="gnet-developers.html" title="GNet for developers">
<link rel="chapter" href="gnet-examples.html" title="GNet Examples">
<link rel="chapter" href="libgnet-reference.html" title="GNet Library Reference">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="2"><tr valign="middle">
<td><a accesskey="p" href="gnet-developers-tips.html"><img src="left.png" width="24" height="24" border="0" alt="Prev"></a></td>
<td><a accesskey="u" href="gnet-developers.html"><img src="up.png" width="24" height="24" border="0" alt="Up"></a></td>
<td><a accesskey="h" href="index.html"><img src="home.png" width="24" height="24" border="0" alt="Home"></a></td>
<th width="100%" align="center">GNet Network Library Reference Manual</th>
<td><a accesskey="n" href="gnet-examples.html"><img src="right.png" width="24" height="24" border="0" alt="Next"></a></td>
</tr></table>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="gnet-developers-async"></a>Hiding blocking</h2></div></div></div>
<p>
Many GNet functions block. That is, they do not return
immediately. For example
<code class="function">gnet_inetaddr_new</code> performs a DNS lookup
that may take several seconds. This is acceptable for many
programs. But, it is not tolerable in interactive GUI
programs or high-performance servers.
</p>
<p>
There are two ways to hide blocking. The first is to use
threads. GLib 2.0 includes thread support (GThread). The
second method is to use asynchronous functions. Asynchronous
functions return immediately and call a callback when the
operation is completed. For example,
<code class="function">gnet_inetaddr_new_async</code> begins an
asynchronous DNS lookup and returns immediately. When the
lookup is complete, a callback is called with the GInetAddr.
Most blocking function in GNet have an asynchronous
counterpart.
</p>
<p>
To use GNet's asynchronous functions, you must also use the
GLib main event loop. Most GTK and Gnome program already do
this.
</p>
<p>
Another common blocking operation is reading or writing to a
GIOChannel (a GLib object).
<code class="function">g_io_channel_read</code> blocks until there is
data available to read.
<code class="function">g_io_channel_write</code> blocks until there is
OS buffer space to write to. To determine when a GIOChannel
can be read to or written from without blocking, use GLib's
<code class="function">g_io_add_watch</code> to set a watch. A
callback is called when the GIOChannel becomes readable or
writable. See the GLib documentation for more information and
GNet's echoclient-async and echoserver-async for an example.
</p>
</div>
</body>
</html>
