Background

Description

In our operating system, the disk is divided disk blocks. Each block is divided into bytes. The file manager is responsible for keeping track of unused (free) disk blocks and all necessary information about every file. The file manager handles requests to create new files, extend existing files, truncate existing files, and delete existing files. It is also possible to print all information within the file manager.

You will implement classes to model the file manager and files within the file manager. You will use the author's Linked List class as well as a modified version of that code to support sorted linked lists.

The number of disk blocks in our system and the number of bytes per disk block will be command line parameters.

Here are your tasks. Operations such as construction, destruction, accessors, and mutators (as necessary) are assumed and not listed for classes.

1. Obtain the author's linked list files from Mr. Frey's public directory for this project /afs/umbc.edu/users/f/r/frey/pub/CMSC341/Proj2/
2. Use the author's code to implement a sorted linked list class.
3. Implement main( ) in Proj2.cpp to read and process the command file
4. Implement the File class. The file class contains all pertinent information about a file within the file manager. The information maintained by the File class are
   1. The file name
   2. The actual size of the file
   3. The allocated size of the file
   4. The number of blocks allocated to the file
   5. A list of disk blocks allocated to the file
   The operations of the File class are
   1. Print all information about a File
   2. Necessary comparison operator(s)
5. Implement the FileManager (FM) class.
   The FM class maintains the following information
   1. A list of free disk blocks, sorted by disk block number
   2. A list of Files, sorted by file name
   The FM class supports the following operations
   1. Create a new file with the specified name and size in bytes.
   2. Extend an existing file by the specified number of bytes
   3. Truncate an existing file by the specified number of bytes
   4. Delete the specified file
   5. Print the contents of the File Manager
   Disk block numbers are integers (starting at zero). Note in the sample output that disk blocks must be printed as ranges.

   FM Errors

   All FM errors must be handled with an appropriate exception.

   The file manager must detect the following errors:

   1. Insufficient disk space when an request to allocate disk blocks cannot be fulfilled because there are not enough free blocks.
   2. No such file whenever an attempt is made to extend, truncate, or delete a non-existing file.
   3. Duplicate file whenever an attempt is made to create a file that already exists.
   4. File Underflow whenever an attempt is made to truncate a file by more bytes than are in the file. In this case, the file should remain unchanged.

6. Answer the questions posed in 341-Spring07-proj2_questions.txt. Copy the file /afs/umbc.edu/users/f/r/frey/pub/CMSC341/Proj2/341-Spring07-p1_questions.txt to your own directory and edit it to provide your answers to the questions. Don't forget to submit the edited file; it's 10% of this project's grade.
7. Implement a makefile for your project. Note that your executable MUST be named Proj2 so that the grading scripts will find and execute your code.

Other Project Requirements

1. All "lists" in this project must be implemented as Linked-Lists using the author's code as a base. Vectors are not permitted in any class.
2. Only the FileManager class can be instantiated in main( ). The File class is only used by the FileManager. Your design and implementation must prohibit the use of File by any other class or program.
3. FileManager errors must be implemented using appropriate exceptions

The Command Line

Note that you must check command line arguments to ensure that they are valid, e.g. that the command file can be opened, and print an appropriate message if an error is found.

The Command File

The command file format follows:

• CREATE <filename> <size in bytes>
  Duplicate file names are not permitted in the file manager.
• DELETE <filename>
  It is an error to attempt to delete a non-existent file.
• EXTEND <filename> <number of bytes>
  Increases the size of the file by the specified number of bytes.
• TRUNCATE <filename> <number of bytes>
  Decreases the size of the file by the specified number of bytes.
  It is an error to attempt to TRUNCATE a file by more than the size of the file. In this case, the file is unchanged.
• PRINT -- Prints the contents of the FileManager
  The following information is required for PRINT
  • The disk block size
  • The number of allocated blocks
  • The number of free blocks
  • The list of free blocks
  • All relevant information about each file including
    • Filename
    • Actual size in bytes
    • Allocated size in bytes
    • Size of the allocated, but unused space
    • List of blocks allocated to the file

Sample Output

A sample command file is also available. Use this command file with a block size of 1024. /afs/umbc.edu/users/f/r/frey/pub/CMSC341/Proj2/p2-commands.txt
The sample command file is not a thorough test of the project, but just that -- a sample. Be sure to create you own command files for thoroughly testing of your code.

Files To Be Submitted

• Proj2.cpp containing main ( )
• Proj2Aux.h and Proj2Aux.cpp if needed
• .h and .cpp files for any class you implement
• 341-Spring07-proj2_questions.txt - containing your answers to the questions.

Submit Tools

If you don't submit a project correctly, you will not get credit for it. Why throw away all that hard work you did to write the project?
Check your submittals. Make sure they work. Do this before the due date.

Documentation for the submit program is on the web at http://www.gl.umbc.edu/submit/. One of the tools provided by the submit program is
submitls. It lists the names of the files you have submitted.

Additionally, there are two programs for use only by CMSC-341 students (not part of the UCS submit program). They are in the directory /afs/umbc.edu/users/f/r/frey/pub/CMSC341/ and are named submitmake and submitrun. You can use these programs to make or run your submitted projects.

The syntax is similar to that for submit:

submitmake <class> <project>

Example:  submitmake cs341 Proj2

This "makes" the project, and shows you the report from the make utility. It cleans up the directory after making the project (removes .o files), but leaves the executable in place.

submitrun <class> <project> [command-line args]

Example:   submitrun cs341Proj2 checkers checkfile.dat

This runs the project, assuming there is an executable (i.e. submitmake was run successfully). Any data files used by your project must be in your local directory.

Grading and Academic Integrity

Project grading is described in the Project Policy handout.

Your answers to 341-Spring07-proj2_questions.txt are worth 10% of your project grade.

Cheating in any form will not be tolerated. Please re-read the Project Policy handout for further details on honesty in doing projects for this course.

Remember, the due date is firm. Submittals made after midnight of the due date will not be accepted. Do not submit any files after that time.