source: trunk/phpgwapi/doc/vfs/vfs.txt @ 2

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*****  1. Introduction_and_Purpose *****
The latest version of the VFS for eGoupWare combines actual file system
manipulation with fully integrated database support. It features nearly
transparent handling of files and directories, as well as files inside and
outside the virtual root. This document is intended to provide API and
application developers with a guide to incorporating the VFS into their work.
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*****  2. Basics *****
*****  2.1 Prerequisites *****
You must explicitly enable the VFS class. To do this, set 'enable_vfs_class' to
True in $GLOBALS['phpgw_info']['flags']. An example:
$GLOBALS['phpgw_info']['flags'] = array(
     'currentapp' => 'phpwebhosting',
     'noheader' => False,
     'noappheader' => False,
     'enable_vfs_class' => True,
     'enable_browser_class' => True
);
*****  2.2 Concepts *****
The VFS in located in phpgwapi/inc/class.vfs_sql.inc.php. You can look over it,
but I don't suggest trying to understand how it works. It isn't necessary to
know its internals to use it, but you may find the inline comments helpful. The
basic things to keep in mind:
    * Files and directories are synonymous in almost all cases
$GLOBALS['phpgw']->vfs->mv (array(
     'from' => 'file1',
     'to' => 'dir/file2'
));

$GLOBALS['phpgw']->vfs->mv (array(
     'from' => 'dir1',
     'to' => 'dir/dir1'
));

$GLOBALS['phpgw']->vfs->rm (array(
     'string' => 'file'
));

$GLOBALS['phpgw']->vfs->rm (array(
     'string' => 'dir'
));
All work as you would except them to. The major exception is:
$GLOBALS['phpgw']->vfs->touch (array(
     'string' => 'file'
));
vs.
$GLOBALS['phpgw']->vfs->mkdir (array(
     'string' => 'dir'
));
    * Users and groups are synonymous
As far as the actual paths are concerned, users and groups are the same. /home/
username works the same as /home/groupname.
    * You should never have to know the real paths of files
One of the VFS's responsibilities is to translate paths for you. While you
certainly can operate using full paths, it is much simpler to use the virtual
paths. For example, instead of using:
$GLOBALS['phpgw']->vfs->cp (array(
     'from' => '/var/www/egroupware/files/home/user/file1',
     'to' => '/var/www/egroupware/files/home/user/file2',
     'relatives' => array(
          RELATIVE_NONE|VFS_REAL,
          RELATIVE_NONE|VFS_REAL
     )
));
you might use
$GLOBALS['phpgw']->vfs->cp (array(
     'from' => '/home/user/file1',
     'to' => '/home/user/file2',
     'relatives' => array(
          RELATIVE_NONE,
          RELATIVE_NONE
     )
));
(We'll get to the RELATIVE's in a minute.)
Site administrators should be able to move their files dir around on their
system and know that everything will continue to work smoothly.
    * Relativity is vital
Relativity is a new feature in the VFS, and its importance cannot be stressed
enough. It will make your life much easier, especially for file system
intensive applications, but it will take some getting used to. If something
doesn't work right the first time, chances are great it has to do with
incorrect relativity settings. We will deal with relativity in depth in the
Relativity section.
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*****  3. Basic_Functions *****
These are two functions you'll need to know before we get into relativity.
*****  3.1 path_parts_() *****
The job of path_parts () is to translate any given file location into its many
component parts for any relativity. The values passed to path_parts () are:
string
relatives
object
'string' is the path you want to translate, 'relatives' is the standard
relativity array, and 'object' specifies how you would like the return value:
if 'object' is True, an object will be returned; if 'object' is False, an array
will be returned. I think you'll find the object easier to deal with, and we'll
be using it throughout this document. The most important returned values (but
not all) for path_parts () are:
fake_full_path
fake_leading_dirs
fake_extra_path
fake_name
real_full_path
real_leading_dirs
real_extra_path
real_name
Just like you would think, fake_full_path contains the full virtual path of
'string', and real_full_path contains the full real path of 'string'. The
fake_name and real_name variables should always be the same, and contain the
final file or directory name. The leading_dirs contain everything except the
name, and the extra_path is everything from the / before "home" to the end of
the leading_dirs. To better illustrate, here is an example:
$p = $GLOBALS['phpgw']->vfs->path_parts (array(
     'string' => '/home/jason/dir/file',
     'relatives' => array(
         RELATIVE_NONE
     )
));
    * $p->fake_full_path - /home/jason/dir/file
    * $p->fake_leading_dirs - /home/jason/dir
    * $p->fake_extra_path - home/jason/dir
    * $p->fake_name - file
    * $p->real_full_path - /var/www/egroupware/files/home/jason/dir/file
    * $p->real_leading_dirs - /var/www/egroupware/files/home/jason/dir
    * $p->real_extra_path - home/jason/dir
    * $p->real_name - file
As you can see, path_parts () is a very useful function and will save you from
doing those darn substr ()'s yourself. For those of you used to the prior VFS,
note that getabsolutepath () is depreciated. getabsolutepath () still exists
(albeit in a much different form), and is responsible for some of the path
translation, but it is an internal function only. Applications should only use
path_parts (). We have shown you how to use path_parts () so you can experiment
with it using different paths and relativities as we explore relativity.
*****  3.2 cd_() *****
Part of the overall goal for the VFS in eGoupWare is to give the user a
seamless experience during their session. For example, if they upload a file
using a file manager to the directory /home/my_group/project1, and then go to
download an email attachment, the default directory will be /home/my_group/
project1. This is accomplished using the cd () function. Examples:
/* cd to their home directory */
$GLOBALS['phpgw']->vfs->cd (array(
     'string' => '/'
));

/* cd to /home/jason/dir */
$GLOBALS['phpgw']->vfs->cd (array(
     'string' => '/home/jason/dir',
     'relative' => False,
     'relatives' => array(
          RELATIVE_NONE
     )
));

/* When following the above, cd's to /home/jason/dir/dir2 */
$GLOBALS['phpgw']->vfs->cd (array(
     'string' => 'dir2',
     'relative' => True
));
If 'relative' is True, the 'string' is simply appended to the current path. If
you want to know what the current path is, use $GLOBALS['phpgw']->vfs->pwd ().
Now you're ready for relativity.
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*****  4. Relativity *****
Ok, just one last thing before we get into relativity. You will notice
throughout the examples the use of $fakebase. $GLOBALS['phpgw']->vfs->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 Fakebase_directory_
(changing_/home) 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. You should always use $fakebase when making applications.I
suggest doing $fakebase = $GLOBALS['phpgw']->vfs->fakebase; right off the bat
to keep things neater.
***** 4.1 What_is_it_and_how_does_it_work? *****
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.
$GLOBALS['phpgw']->vfs->mv (array(
    'from' => 'logo.png',
    'to' => 'logo.png',
    'relatives' => array(
          RELATIVE_USER,
          RELATIVE_ALL
     )
));
RELATIVE_USER means relative to the user's home directory. RELATIVE_ALL means
relative to the current directory, as set by cd () and as reported by pwd ().
So if the current directory was "$fakebase/my_group/project1", the call to mv
() would be processed as:
MOVE "$fakebase/jason/logo.png" TO "$fakebase/my_group/project1/logo.png"
and the actual file system call would be:
rename ('/var/www/egroupware/files/home/jason/logo.php', '/var/www/
egroupware/files/home/my_group/project1/logo.png');
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 outside the virtual
root.
$GLOBALS['phpgw']->vfs->mv (array(
     'from' => $GLOBALS['phpgw_info']['server']['temp_dir'] . '/' . $randomdir
. '/' . $randomfile,
     'to' => 'attachments/actual_name.ext',
     'relatives' => array(
          RELATIVE_NONE|VFS_REAL,
          RELATIVE_USER
     )
));
$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 outside 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):
rename ('/var/www/egroupware/tmp/0ak5adftgh7/jX42sC9M', '/var/www/
egroupware/files/home/jason/attachments/actual_name.ext');
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:
$GLOBALS['phpgw']->vfs->write (array(
     'string' => 'file.name~',
     'relatives' => array(
          RELATIVE_USER_APP
     ),
     'content' => $contents
));
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.
*****  4.2 Complete_List *****
Here is the complete list of RELATIVE defines, and what they do:
  RELATIVE_ROOT
      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.
  RELATIVE_USER
      User's home directory
  RELATIVE_CURR_USER
      Current user's home directory. If the current directory is $fakebase/
      my_group/project1, this will return is $fakebase/my_group
  RELATIVE_USER_APP
      Append .appname to the user's home directory, where appname is the
      current application's appname
  RELATIVE_PATH
      DO NOT USE. Relative to the current directory, used in RELATIVE_ALL
  RELATIVE_NONE
      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
  RELATIVE_CURRENT
      An alias for the currently set RELATIVE define, or RELATIVE_ALL if none
      is set (see the Defaults section)
  VFS_REAL
      File is outside of the virtual root. Usually used with RELATIVE_NONE
  RELATIVE_ALL
      Relative to the current directory. Use RELATIVE_ALLinstead of
      RELATIVE_PATH
*****  4.3 Defaults *****
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), unless 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:
$GLOBALS['phpgw']->vfs->set_relative (array(
     'mask' => RELATIVE_NONE|VFS_REAL
));

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

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

$GLOBALS['phpgw']->vfs->cp (array(
     'from' => '/usr/share/pixmaps/yes.xpm',
     'to' => 'icons/yes.xpm',
     'relatives' => array(
          RELATIVE_CURRENT,
          RELATIVE_USER
     )
));
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.
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*****  5. Function_reference *****
To view the function reference for the VFS, use the doc/inlinedocparser.php
script that comes with eGoupWare, ie http://localhost/doc/
inlinedocparser.php?fn=class.vfs_sql.inc.php.
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*****  6. Notes *****
*****  6.1 Database *****
Data about the files and directories within the virtual root is kept in the SQL
database. Currently, this information includes:
    * File ID (used internally, primary key for table)
    * Owner ID (phpGW account_id)
    * Created by ID (phpGW account_id)
    * Modified by ID (phpGW account_id)
    * Created (date)
    * Modified (date)
    * Size (bytes)
    * MIME type
    * Deleteable (Y/N/Other?)
    * Comment
    * App (appname of application that created the file)
    * Directory (directory the file or directory is in)
    * Name (name of file or directory)
    * Link directory (if the file or directory is linked, what the actual
      directory is)
    * Link name (if the file or directory is linked, what the actual name is)
    * Version (numeric version of the file)
The internal names of these (the database column names) are stored in the
$GLOBALS['phpgw']->vfs->attributes array, which is useful for loops, and is
guaranteed to be up-to-date.
Note that no information is kept about files outside the virtual root. If a
file is moved outside, all records of it are deleted from the database (other
than the journaling records). If a file is moved into the virtual root, some
information, specifically MIME-type, is not always stored in the database. The
vital information has defaults: owner is based on where the file is being
stored; size is correctly read; deleteable is set to Y.
*****  6.2 ACL_support *****
ACL support is built into the VFS. vfs->acl_check () does the actual checking,
and is called from all VFS functions as needed. If the file or directory sent
to acl_check () doesn't exist, the permissions for the parent directory are
used to determine access. ACL checking can be overridden at any time by setting
vfs->override_acl. For example:
$GLOBALS['phpgw']->vfs->override_acl = 1;
$GLOBALS['phpgw']->vfs->mkdir (array(
     'string' => $GLOBALS['fakebase']. '/' . $group_array['account_name'],
     'relatives' => array(
          RELATIVE_NONE
     )
));
$GLOBALS['phpgw']->vfs->override_acl = 0;
*****  6.3 Function_aliases *****
You might have noticed there are some functions that just pass the arguments on
to other functions. These are provided in part because of legacy and in part
for convenience. You can use either. Here is the list (alias -> actual):
    * copy -> cp
    * move -> rm
    * delete -> rm
    * dir -> ls
*****  6.4 Fakebase_directory_(changing_/home) *****
The old VFS was hard-coded to use '/home' as the fake base directory, even
though the user never saw it. With the new system, crafty administrators may
wish to change '/home' to something else, say '/users' or '/public_html'. The
fake base directory name is stored in $GLOBALS['phpgw']->vfs->fakebase, and
changing it will transparently change it throughout the VFS and all
applications. However, this must be done before any data is in the VFS
database. If you wish to change it afterwords, you'll have to manually update
the database, replacing the old value with the new value. Application
programmers need to recognize that /home is not absolute, and use $GLOBALS
['phpgw']->vfs->fakebase instead. I suggest setting $fakebase = $GLOBALS
['phpgw']->vfs->fakebase; right off the bat to keep things neater.
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***** 7. About_this_Document *****
***** 7.1 Copyright_and_License *****
Copyright (c) 2001, 2002 Jason Wies
Permission is granted to copy, distribute and/or modify this document under the
terms of the GNU Free Documentation License, Version 1.1 or any later version
published by the Free Software Foundation; with no Invarient Sections, with no
Front-Cover Texts, and no Back-Cover Texts.
A copy of the license is available at http://www.gnu.org/copyleft/fdl.html.
***** 7.2 History *****
Original document released in June 2001 by Jason Wies.
Updated February 2002 to include arrayized parameters, single quotes, and
GLOBALS.
***** 7.3 Contributing *****
Contributions are always welcome. Please send to the current maintainer, Jason
Wies, 
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