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Matthias Clasen 2007-12-18 00:56:35 +00:00
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docs/reference/gio/overview.xml
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@ -1,6 +1,88 @@
<part>
<title>GIO Overview</title>
<para>
GIO is striving to provide a modern, easy-to-use VFS api that sits
at the right level in the library stack. The goal is to overcome the
shortcomings of gnome-vfs and provide an api that is so good that
developers prefer it over raw POSIX calls. Among other things
that means using GObject. It also means not cloning the POSIX
api, but providing a higher-level, document-centric interfaces.
</para>
<para>
The abstract file system model of GIO consists of a number of
interfaces and base classes for I/O and files:
<variablelist>
<varlistentry>
<term>GFile</term>
<listitem><para>reference to a file</para></listitem>
</varlistentry>
<varlistentry>
<term>GFileInfo</term>
<listitem><para>information about a file or filesystem</para></listitem>
</varlistentry>
<varlistentry>
<term>GFileEnumerator</term>
<listitem><para>list files in directories</para></listitem>
</varlistentry>
<varlistentry>
<term>GDrive</term>
<listitem><para>represents a drive</para></listitem>
</varlistentry>
<varlistentry>
<term>GVolume</term>
<listitem><para>represents a file system in an abstract way</para></listitem>
</varlistentry>
<varlistentry>
<term>GMount</term>
<listitem><para>represents a mounted file system</para></listitem>
</varlistentry>
</variablelist>
Then there is a number of stream classes, similar to the input and
output stream hierarchies that can be found in frameworks like Java:
<variablelist>
<varlistentry>
<term>GInputStream</term>
<listitem><para>read data</para></listitem>
</varlistentry>
<varlistentry>
<term>GOutputStream</term>
<listitem><para>write data</para></listitem>
</varlistentry>
<varlistentry>
<term>GSeekable</term>
<listitem><para>seek in data</para></listitem>
</varlistentry>
</variablelist>
There are interfaces related to applications and the types
of files they handle:
<variablelist>
<varlistentry>
<term>GAppInfo</term>
<listitem><para>information about an installed application</para></listitem>
</varlistentry>
<varlistentry>
<term>GIcon</term>
<listitem><para>abstract type for file and application icons</para></listitem>
</varlistentry>
</variablelist>
Beyond these, GIO provides facilities for file monitoring,
asynchronous I/O and filename completion. In addition to the
interfaces, GIO provides implementations for the local case.
Implementations for various network file systems are provided
by the GVFS package as loadable modules.
</para>
<para>
Other design choices which consciously break with the gnome-vfs
design are to move backends out-of-process, which minimizes the
dependency bloat and makes the whole system more robust. The backends
are not included in GIO, but in the separate GVFS package. GVFS
also contains the GVFS daemon, which spawn further mount daemons
for each individual connection.
</para>
<para>
<figure id="mainloop-states">
<title>GIO in the GTK+ library stack</title>
@ -8,7 +90,15 @@
</figure>
</para>
<!-- FIXME a picture is worth a 1000 words,
but we still need some text here
-->
<para>
The GIO model of I/O is stateful: if an application establishes e.g.
a sftp connection to a server, it becomes available to all applications
in the session; the user does not have to enter his password over
and over again.
</para>
<para>
One of the big advantages of putting the VFS in the GLib layer
is that GTK+ can directly use it, e.g. in the filechooser.
</para>
</part>