Programming Lab #4: Tree-structured Directories
Assigned: Mon 13 Apr 1998
Due: Mon 20 Apr 1998
For this project you will write a program which:
In particular, you should use the representation of general trees discussed in the
Weiss textbook (pp. ). In addition to the firstChild and
leftSibling pointers discussed there, we would also like to support
access from a child node to that node's parent. The natural way to do this would
be to use a separate reference within each node to the node's parent. Therefore,
each of your tree nodes should have three references to other nodes in addition to
a data field.
The data contained in the trees should be generic, i.e., you should use Object
as the corresponding type in your general tree class. For this specific use of
general trees (i.e., for the directory structure simulation), you will use a
specific class which describes a simple file or directory.
Your implementation should create an empty directory structure for the user when
it is first
started up, and then accept commands to ...
Note The sections of the textbook which describe file systems applications
of general trees may be helpful, but this application is different from the one
described there. Nevertheless, you will want to read the approprate sections
on the implementation of general trees using binary trees.
For details on the methods you should support, the command-line interface,
error reporting, etc., see below.
Note also that, just as for the linked list iterator class given in the text on
page 400, your insertion and removal methods should throw an ItemNotFound
exception.
We'll use single- or double-character commands as follows
(in keeping with the syle of unix, we'll use lowercase letters):
one argument, the name of the directory.
Note: creates the directory only; does not change current directory.
one argument, the name of the file; also reads in a single string
(terminated by end of line) which is the contents of the file.
one argument, the pathname of the intended new current directory;
the pathname is a list of identifiers separated by slashes. If there
is an initial slash, the path starts at the top of the tree. If not,
the path is relative to the current directory. In addition to identifiers,
the special code "^" may be used, which indicates the parent of the current
directory (relative to where we are in the path). This is like the unix "..".
no argument. Lists out the names of the files and directories in the current
directory, one per line. Each name which is the name of a directory (rather
than a file) should have a slash placed after the name.
one argument: a filename. This command prints out the contents of the named
file, without changing the current directory. A filename may be either a
simple name (of a file in the current directory) or a pathname plus a filename.
one argument: the name of the directory or file to be removed (may include a
full pathname).
A note on errors: for each of the above operations/methods, you should
give an explicit report if an error occurs, i.e., if there is no way to perform
the requested operation.
Here is a sample run showing typical input/output (you should feel free to use
appropriate introductory text and prompts of your own design):
Your project will be assessed on the basis of both a "live" demonstration
and a hard copy description and print-out of the project code.
The printed version
should specify both members of your group and should specifically mention any free
late days used, remaining problems or bugs, special enhancements, etc. In addition
to "raw code", you should include a brief introduction describing anything that is
special in your approach to the problem (bugs, enhancements, etc., should also be
mentioned here).
Your grade will be determined in part by the correctness of your code, but also
by virtue of the techniques you use to implement it.
I will be available in lab on Monday mornings from 10:00 - 11:30 for demonstrations.
You may also demonstrate at other times (Thursday morning office hours will likely
be popular), including by appointment, but you must demonstrate your project and hand
in your hard copy by the due date unless you receive a specific provision otherwise
(see also the information about free late days on the syllabus).
md command:
make a directory
mf command:
make a file
cd command:
change directory
ls command:
list out directory
pf command:
print a file
rm command:
remove a file or directory
Welcome to Directorium, your directory system value store!
Enter commands one per line, and input values where indicated:
> ls
*empty directory*
> md foobar
[created directory "foobar"]
>
Thanks for using Directorium, come again soon!
