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<H2><A NAME="sec:relativity"></A> <A NAME="s4">4.</A> <A HREF="vfs.html#toc4">Relativity</A></H2>

<P>Ok, just one last thing before we get into relativity. You will
notice throughout the examples the use of $fakebase. $GLOBALS['phpgw']-&gt;vfs-&gt;fakebase
is by default '/home'. The old VFS was hard-coded to use '/home',
but the naming choice for this is now up to administrators. See the
<A HREF="vfs-6.html#sec:fakebase">Fakebase directory (changing /home)</A> section for more information. Throughout the rest of this document,
you will see $fakebase used in calls to the VFS, and /home
used in actual paths. <EM>You should always use $fakebase when
making applications. </EM>I suggest doing $fakebase = $GLOBALS['phpgw']-&gt;vfs-&gt;fakebase;
right off the bat to keep things neater.</P>
<H2><A NAME="ss4.1">4.1</A> <A HREF="vfs.html#toc4.1">What is it and how does it work?</A>
</H2>

<P>One of the design challenges for a Virtual File System is to
try to figure out whether the calling application is referring to
a file inside or outside the virtual root, and if inside, exactly
where. To solve this problem, the eGoupWare VFS uses RELATIVE
defines that are used in bitmasks passed to each function. The result
is that any set of different relativities can be used in combination
with each other. Let's look at a few examples. Say you want to move
'logo.png' from the user's home directory to the current directory.</P>

<P>
<PRE>
$GLOBALS['phpgw']-&gt;vfs-&gt;mv (array(
    'from' =&gt; 'logo.png',
    'to' =&gt; 'logo.png',
    'relatives' =&gt; array(
          RELATIVE_USER,
          RELATIVE_ALL
     )
));
</PRE>
</P>
<P>RELATIVE_USER means relative to the user's home directory. RELATIVE_ALL
means relative to the current directory, as set by cd () and as reported
by pwd (). So if the current directory was "$fakebase/my_group/project1",
the call to mv () would be processed as:</P>
<P>
<PRE>
MOVE "$fakebase/jason/logo.png" TO "$fakebase/my_group/project1/logo.png"
</PRE>
</P>
<P>and the actual file system call would be:</P>
<P>
<PRE>
rename ('/var/www/egroupware/files/home/jason/logo.php', '/var/www/egroupware/files/home/my_group/project1/logo.png');
</PRE>
</P>
<P>Those used to the old VFS will note that you do not have to translate
the path beforehand. Let's look at another example. Suppose you were
moving an email attachment stored in eGoupWare's temporary directory
to the 'attachments' directory within the user's home directory (we're
assuming the attachments directory exists). Note that the temporary
directory is <EM>outside</EM> the virtual root.</P>
<P>
<PRE>
$GLOBALS['phpgw']-&gt;vfs-&gt;mv (array(
     'from' =&gt; $GLOBALS['phpgw_info']['server']['temp_dir'] . '/' . $randomdir . '/' . $randomfile,
     'to' =&gt; 'attachments/actual_name.ext',
     'relatives' =&gt; array(
          RELATIVE_NONE|VFS_REAL,
          RELATIVE_USER
     )
));
</PRE>
</P>
<P>$randomdir and $randomfile are what the directory
and file might be called before they are given a proper name by the
user, which is actual_name.ext in this example. RELATIVE_NONE is
the define for using full path names. However, RELATIVE_NONE is still
relative to the virtual root, so we pass along VFS_REAL as well,
to say that the file is <EM>outside</EM> the virtual root, somewhere else
in the file system. Once again, RELATIVE_USER means relative to the
user's home directory. So the actual file system call might look
like this (keep in mind that $randomdir and $randomfile
are just random strings):</P>
<P>
<PRE>
rename ('/var/www/egroupware/tmp/0ak5adftgh7/jX42sC9M', '/var/www/egroupware/files/home/jason/attachments/actual_name.ext');
</PRE>
</P>
<P>Of course you don't have to know that, nor should you be concerned
with it; you can take it for granted that the VFS will translate
the paths correctly. Let's take a look at one more example, this
time using the RELATIVE_USER_APP define. RELATIVE_USER_APP is used
to store quasi-hidden application files, similar to the Unix convention
of ~/.appname. It simply appends .appname to the user's home
directory. For example, if you were making an HTML editor application
named 'htmledit', and wanted to keep a backup file in case something
goes wrong, you could use RELATIVE_USER_APP to store it:</P>
<P>
<PRE>
$GLOBALS['phpgw']-&gt;vfs-&gt;write (array(
     'string' =&gt; 'file.name~',
     'relatives' =&gt; array(
          RELATIVE_USER_APP
     ),
     'content' =&gt; $contents
));
</PRE>
</P>
<P>This assumes that ~/.htmledit exists of course. The backup
file "file.name~" would then be written in $fakebase/jason/.htmledit/file.name~.
Note that storing files like this might not be as good of a solution
as storing them in the temporary directory or in the database. But
it is there in case you need it.</P>
<H2><A NAME="sec:relatives_complete_list"></A> <A NAME="ss4.2">4.2</A> <A HREF="vfs.html#toc4.2">Complete List</A>
</H2>

<P>Here is the complete list of RELATIVE defines, and what they
do:</P>
<P>
<DL>
<DT><B>RELATIVE_ROOT</B><DD><P>Don't translate the path at all. Just prepends
a /. You'll probably want to use RELATIVE_NONE though, which handles
both virtual and real files.</P>
<DT><B>RELATIVE_USER</B><DD><P>User's home directory</P>
<DT><B>RELATIVE_CURR_USER</B><DD><P>Current user's home directory. If the
current directory is $fakebase/my_group/project1, this will
return is $fakebase/my_group</P>
<DT><B>RELATIVE_USER_APP</B><DD><P>Append .appname to the user's home directory,
where appname is the current application's appname</P>
<DT><B>RELATIVE_PATH</B><DD><P>DO NOT USE. Relative to the current directory,
used in RELATIVE_ALL</P>
<DT><B>RELATIVE_NONE</B><DD><P>Not relative to anything. Use this with VFS_REAL
for files outside the virtual root. Note that using RELATIVE_NONE
by itself still means relative to the virtual root</P>
<DT><B>RELATIVE_CURRENT</B><DD><P>An alias for the currently set RELATIVE
define, or RELATIVE_ALL if none is set (see the Defaults section)</P>
<DT><B>VFS_REAL</B><DD><P>File is outside of the virtual root. Usually used
with RELATIVE_NONE</P>
<DT><B>RELATIVE_ALL</B><DD><P>Relative to the current directory. Use RELATIVE_ALL<EM></EM>instead of RELATIVE_PATH</P>
</DL>
</P>
<H2><A NAME="sec:relatives_defaults"></A> <A NAME="ss4.3">4.3</A> <A HREF="vfs.html#toc4.3">Defaults</A>
</H2>

<P>You might be thinking to yourself that passing along RELATIVE
defines with every VFS call is overkill, especially if your application
always uses the same relativity. The default RELATIVE define for
all VFS calls is RELATIVE_CURRENT. RELATIVE_CURRENT itself defaults
to RELATIVE_ALL (relative to the current path), <EM>unless</EM> your application
sets a specific relativity. If your application requires most of
the work to be done outside of the virtual root, you may wish to
set RELATIVE_CURRENT to RELATIVE_NONE|VFS_REAL. set_relative () is
the function to do this. For example:</P>
<P>
<PRE>
$GLOBALS['phpgw']-&gt;vfs-&gt;set_relative (array(
     'mask' =&gt; RELATIVE_NONE|VFS_REAL
));

$GLOBALS['phpgw']-&gt;vfs-&gt;read (array(
     'string' =&gt; '/etc/passwd'
));

$GLOBALS['phpgw']-&gt;vfs-&gt;cp (array(
     'from' =&gt; '/usr/include/stdio.h',
     'to' =&gt; '/tmp/stdio.h'
));

$GLOBALS['phpgw']-&gt;vfs-&gt;cp (array(
     'from' =&gt; '/usr/share/pixmaps/yes.xpm',
     'to' =&gt; 'icons/yes.xpm',
     'relatives' =&gt; array(
          RELATIVE_CURRENT,
          RELATIVE_USER
     )
));
</PRE>
</P>
<P>You should notice that no relativity array is needed in the other
calls that refer to files outside the virtual root, but one is needed
for calls that include files inside the virtual root. Any RELATIVE
define can be set as the default and works in the same fashion. To
retrieve the currently set define, use get_relative (). Note that
the relativity is reset after each page request; that is, it's good
only for the life of the current page loading, and is not stored
in session management.</P>
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