Apple AppleShare 3.0 File Server Controls - Manual (Page 5)

File Manager The Macintosh File Manager normally handles local requests for
file access. When Macintosh File Sharing is turned on, however, the File
Sharing Extension intercepts all file access calls from the File Manager.
Server additions Applications, INITs, extensions, and other types of
programs can access the File Server Extension by using server control calls.
A program that uses server control calls is referred to as a server addition.
This guide tells you how to create server additions by using server control
calls in your own programs.
Data files
Both the AppleShare File Server 3.0 and Macintosh File Sharing use two data
files to store user and directory information: the Users & Groups Data File
and the AppleShare PDS file.
Users & Groups Data File The Users & Groups Data File contains a database of
the users and groups defined on your computer. You define users and groups
for the AppleShare File Server 3.0 by using the AppleShare Admin application.
You define users and groups with Macintosh File Sharing by using the Users &
Groups control panel. The data file is a B-Tree file. With the AppleShare
File Server 3.0, the AppleShare Admin and File Server Extension files use the
Users & Groups Data File. With Macintosh File Sharing, the Network Extension
and File Sharing Extension files use the Users & Groups Data File.
AppleShare PDS The AppleShare PDS file is an invisible file that resides at
the root of every unlocked volume. PDS stands for parallel directory
structure. The AppleShare PDS file contains the access privilege and share-
point information for the volume on which the file resides. The PDS file
determines the access privileges of the volume's users and groups, which are
defined in the Users & Groups Data File. Because the PDS file is created in
conjunction with the Users & Groups Data File, the Users & Groups Data File
must not be removed from the volume. (If the Users & Groups Data File is
lost, the access privilege and share-point information contained in the PDS
file is lost as well.)
The PDS file for CD-ROM drives resides in the File Sharing folder (in the
Preferences folder) for Macintosh File Sharing, and in the File Server folder
(in the Preferences folder) for the AppleShare File Server 3.0.
Using server control calls
This section presents each of the server control calls available with the
AppleShare File Server 3.0. The server control calls are presented in logical
functional groups, more or less in the order in which you would use them in
server additions.
For each server control call, there is a function named MycallName.
Typically, this function shows how to fill in the parameter block, make the
server control call, and retrieve any result values returned by the call.
When necessary, the MycallName functions also include code that makes the
server control calls supported by Macintosh File Sharing behave as much as
possible in the same manner as they behave when used under the AppleShare
File Server 3.0. For example, a MycallName function may return a value that
is normally returned by the AppleShare File Server 3.0 but that is not
supplied by Macintosh File Sharing. In other cases, for example with the
SCGetExpFldr call, the function contains code that makes the call work "as
advertised."