Chapter 13: Programming Projects
1. Write a line oriented text editor program in C++ that
accepts the input of the file to be edited on the
command line. If the file name is not input on the
command line, the program indicates that the file does
not exist and terminates. If the file is present,
the contents of the file are read into memory and
placed into a list for further processing.
A line editor is represented by a doubly linked list of
nodes, each of which contains a pointer to the text of
the line. In addition, each node contains the number
of bytes in the text line. There is one external
pointer to this list, which points to the "current"
line position in the text being edited. The
list has a header node, which contains the string:
'----Top of File----'
and a trailer node, which contains the string:
'----Bottom of File----'
Write a line editor that only supports the listing of
lines of text to the screen. The program will execute
and display the first line of text in the file along
with the line number of that line. The program will
then show its prompt, a '?', and is ready to
accept commands. For example:
----Top of File----
1: main()
?
If a list or print of lines goes to the end of the
file, the trailer node holding
'----Bottom of File----'
must be displayed as the last line.
Each node of the linked list holds a CTextLine
class item. A CTextLine is a class that is
derived from CRecord which is an abstract base
class that generically defines records that are
held within a document. The CTextLine class has
the following data members.
char *textLine; // the text of a line from the file
size_t textLgth; // the length of the line being held
The abstract base class CRecord defines two pure
virtual functions for reading input from the disk and
for placing data onto the disk.
virtual void readRecord( size_t length) const = 0;
virtual void writeRecord( size_t length) const = 0;
The CTextLine class implements its own versions
of these functions in order to read and write data to
disk.
This program will create the following C++ classes.
CDocument - opens a disk file and stores or retrieves
data from the file depending upon which
method of the class is called. The
constructor is passed two arguments:
- the name of the file to open, if the file
does not exist a boolean is set indicating such.
- the address of a CRecord class or
derived class.
This class has a pointer to the
CRecord class which holds the
address passed as a parameter of the
constructor. Overload the following
operators:
++ : move to next item in document
-- : move to previous item in document
+ : add a new item to the document
- : delete an item from the document
Use the pointer to the CRecord type
to access the correct derived class that
knows how to read and write data of the
correct type to and from the disk.
CView - displays data on the screen, one screen at a
time
CCommandSet - this class holds the commands allowed and
maps those keys to methods within this
class. The initial command set will be
as follows:
( means that the RETURN key is
pressed)
show next line in file
m,np show the lines of
text starting with line number
m and ending with line
number 'n'
n show the text for line number
'n'
np show the next 'n' lines
of text in the file
w filename write the contents of the
linked list to the
'filename' specified.
q quit the editor
2. Develop the following classes:
CDataBase - a data base class that opens a data
file and an index file. This class
supports a 'has-a' relationship with
CRecord and CIndex.
This class will support methods for:
- define the location of a key in each record
as being a specified number of bytes from
the beginning of the record and being a
stated number of bytes in length.
- receiving an address of CRecord type
object and placing the data held in the
object on the data file through polymorphic
behavior
- retrieving data from the data file by using
an address of a CRecord type object
that reads the data file.
- has an instance of CIndex type data
that is used to maintain a sorted list of
keys into the data file.
CRecord - an abstract base class that defines
generic behavior for a record that is to
be written to or read from the data file
of the data base.
CIndex - a class that keeps a sorted array of keys
into the data file. A key is a structure
that has a the following format:
struct Key
{
char *keyValue; // holds the value that is
// used as a key to access
// the associated data
// record; keys are always
// characters
long dataOffset; // the number of bytes
// from the beginning of
// the data file where the
// associated record is
// stored
};
The index is saved into an index file when
the data base is closed.
Also, develop a test program that will save student
information, CStudent, into the data base, using
student social security number as the key.
CStudent will be a derived class from
CRecord. Make the program present a
menu, CMenu, that has the following items.
1. Add students
2. View students
3. Quit application
The program must acquire student data interactively
from the keyboard and store that data into the data
base. When processing a request to view the data, the
data will be show in the ascending order of the key
field, student social security number.
CStudent has the following data members.
Social Security Number
Last Name
First Name
Street
City
State
Zip
Area Code
Phone
Major