Category : Alternate Operating Systems - Quarterdeck DesqView, CP/M, etc
Archive   : PCCAPP.ZIP
Filename : FSI.H

/*
* This file is part of the Choices Operating System
* Developed by: The TAPESTRY Parallel Computing Laboratory
* University of Illinois at Urbana-Champaign
* Department of Computer Science
* 1304 W. Springfield Ave.
* Urbana, IL 61801
*
* Copyright (c) 1987, 1988, 1989, 1990, 1991, 1992
* The University of Illinois Board of Trustees.
* All Rights Reserved.
*
* Author: Peter W. Madany ([email protected])
* Contributing Author: Vincent F. Russo ([email protected])
* Contributing Author: Douglas E. Leyens ([email protected])
* Contributing Author: Lee Lup Yuen ([email protected])
* Project Manager and Principal Investigator: Roy Campbell ([email protected])
*
* Funded by: NSF TAPESTRY Grant No. 1-5-30035, NASA ICLASS Grant
* No. 1-5-25469 and No. NSG1471 and AT&T Metronet Grant No. 1-5-37411.
*
* Permission to use, copy, modify, and distribute this software and
* its documentation for educational, research, and non-profit purposes
* is hereby granted provided that the above copyright notice, the
* original authors names, and this permission notice appear in all such
* copies and supporting documentation; that no charge be made for such
* copies; and that the name of the University of Illinois not be used
* in advertising or publicity pertaining to distribution of the
* software without specific prior written permission. Any entity
* desiring permission to incorporate this software into commercial
* products should contact the Computing Research Laboratory, Department
* of Computer Science, University of Illinois, 1304 W. Springfield
* Avenue, Urbana, IL 61801. The University of Illinois makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*/
/*
* FileSystemInterface.h - user file system interface class
*/

#ifndef FileSystemInterface_h
#define FileSystemInterface_h
#ifdef __GNUG__
#pragma once
#pragma interface
#endif

#include "ProxiableObject.h"
#include "StoredObjectStar.h"
class UserClass;

class FileSystemInterface : public ProxiableObject
{
/* The FileSystemInterface class is a generic interface to a generic file
* system. This is specialized for specific filesystem types such as
* DOSFileSystemInterface. The global variable StandardFileSystemInterface
* always points to the specific FileSystemInterface that applications
* should use to access the filesystem.
*
* Brief explanation of the filesystem framework in Choices: the FileSystem
* Interface is primarily used by applicatins to open files. When a file is
* opened, a StoredObject is returned to the caller, and methods on that
* object may be called to manipulate the contents of the file. Users
* may specify a particular subclass of StoredObject for the object
* to be returned. A FileStream is a type of StoredObject that interprets
* the file contents as a stream of bytes. ReadFileStream and
* WriteFileStream are subclasses of FileStream that enable the user to read
* and write, respectively, to the file at the byte level. Automatic
* garbage collection permit the StoredObject to be closed and deleted
* automatically when no longer in use.
*
* Each StoredObject is associated with an underlying File, which is a
* machine-dependent handle to an actual file stored on disk. File is
* a generic class whose subclasses represent file handles for specific
* filesystems (eg. DOSFile). Files are also accessed at the byte level.
* StoredObject and its subclasses are responsible for translating
* their operations into byte-level operations on the underlying Files.
*
* In this filesystem framework, applications only need to work directly
* with FileSystemInterfaces and StoredObjects (including all subclasses).
* All other objects should not be manipulated directly by applications.
*/
public:
/* Method create: Create the file named "path" and return a StoredObject
* of class cls for writing to the file. mode indicates the permissions
* for the new file. Write into status one of the error codes described
* in FileSystem.h (or fs2.h). If the file already exists, report the
* error in status.
*/
virtual StoredObjectRef create (const char *path, UserClass *cls,
int mode, int &status) = 0;

/* Method openOrCreate: Open the file named "path" and return a
* StoredObject of class cls for writing to the file. Write into status
* one of the error codes described in FileSystem.h (or fs2.h). If the
* file already exists, it is truncated to null. If the file doesn't
* exist, it is created and its permissions are set according to mode.
*/
virtual StoredObjectRef openOrCreate (const char *path, UserClass *cls,
int mode, int &status) = 0;

/* Method open: Open the file named "path" and return a StoredObject of
* class cls for writing to the file. Write into status one of the error
* codes described in FileSystem.h (or fs2.h). If the file doesn't
* exist, report the error in status.
*/
virtual StoredObjectRef open (const char *path, UserClass *cls,
int &status) = 0;

/* Method chdir: Change the current directory to dirname. Return one
* of the error codes described in FileSystem.h (or fs2.h).
*/
virtual int chdir (const char *dirname) = 0;

/* Method unlink: Delete the file named "pathname". Return one of the
* error codes described in FileSystem.h (or fs2.h).
*/
virtual int unlink (const char *pathname) = 0;
};

// This variable is used by applications for accessing filesystem services.
extern FileSystemInterface *StandardFileSystemInterface;

#endif FileSystemInterface_h