PROCEDURE Store;
{ stores contents of tree onto disc }
VAR
fileroot,
filename: filestring;
dummy_end: persondetails;
{a dummy end of file record is needed because EOF function
does not work correctly in Pascal/Z. See page 54}
slug: shorty;
i: integer;
test: boolean;
BEGIN
{ get file name
}
write ('Name of output file - ');
readln (filename);
reset(filename,fin);
if not eof(fin) {false if file does not exist}
then begin
i := 1;
setlength(fileroot, 0);
while filename[i] <> '.' do {strip CPM file type}
begin
append( fileroot, filename[i]);
{ filename[i] works ok to READ characters of a string,
but fileroot[i] will not WRITE characters into the string.
One of the sneaky differences between strings and arrays
of characters.}
i := i + 1;
end; {while}
append(fileroot, '.BAK');
test := rename (filename, fileroot);
writeln('Existing ', filename, ' renamed ', fileroot,'.');
writeln('New ',filename, ' being opened.');
end; {then}
rewrite (filename, fout);
disc := true;
{raise flag for use in DISPLAY procedure}
Preorder ( employee );
{Preorder is used rather than Inorder so that the tree is stored
in other than a sorted fashion. When putting the leaves back
onto the tree (in FETCH below), inserting them in a sorted order
will result in a lopsided tree - one pointer in each record will
always be NIL. In other words a linked list rather than a full
b - tree will result. The program will work, but the speed of
a balanced tree will be lost.
}
slug := '****************************************';
with dummy_end do
{for reasons I have been unable to divine, leaving 'city'
undefined gets a "string too long" fatal error. Filling
all fields of the record makes the error go away. If you
know why, please tell me. Buddenberg
}
begin
name := slug;
company := 'end of file marker';
address := slug;
city := slug;
state := slug;
zip := slug;
salary := slug;
end; {with}
write (fout, dummy_end);
END; {Store}
{$T-}
PROCEDURE Fetch;
{ reads data from disc and causes it to be placed onto tree }
VAR
filename: string 14;
fileend: boolean;
rec: persondetails;
BEGIN
write ('Name of file where the data is - ');
readln (filename);
reset (filename, fin);
fileend := false;
while not fileend do
BEGIN
read (fin, rec );
if rec.name = '****************************************'
then fileend := true;
if not fileend then
with rec do
begin
key := name;
new_salary := salary;
new_company := company;
new_address := address;
new_city := city;
new_state := state;
new_zip := zip
end; {with}
insert (Employee, key);
end; {while}
END; {fetch}
.
