Category : Files from Magazines
Archive : DDJ1189.ZIP
Filename : STEVENS.LST
Output of file : STEVENS.LST contained in archive : DDJ1189.ZIP
by Al Stevens
[LISTING ONE]
// -------- linklist.h
#ifndef LINKLIST
#define LINKLIST
#include
class LinkedList {
typedef struct list_entry {
struct list_entry *NextEntry;
struct list_entry *PrevEntry;
void *entrydata;
} ListEntry;
ListEntry *FirstEntry;
ListEntry *LastEntry;
ListEntry *CurrEntry;
public:
// ---- constructor
LinkedList(void)
{ FirstEntry = LastEntry = CurrEntry = NULL; }
// ---- destructor
~LinkedList(void);
// ---- add an entry
void addentry(void *newentry, int size);
// ---- delete the current entry
void delete_entry(void);
// ---- get the first entry in the list
void *getfirst(void);
// ---- get the next entry in the list
void *getnext(void);
// ---- get the previous entry in the list
void *getprev(void);
// ---- get the last entry in the list
void *getlast(void);
// ---- get the current entry in the list
void *getcurr(void)
{return CurrEntry==NULL ? NULL : CurrEntry->entrydata;}
};
#endif
[LISTING TWO]
// -------------- linklist.cpp
#include
#include "linklist.h"
// ------- linked list destructor
LinkedList::~LinkedList(void)
{
ListEntry *thisentry = FirstEntry;
while (thisentry != NULL) {
delete thisentry->entrydata;
ListEntry *hold = thisentry;
thisentry = thisentry->NextEntry;
delete hold;
}
}
// --------- add an entry to the list
void LinkedList::addentry(void *newentry, int size)
{
/* ------- build the new entry ------- */
ListEntry *thisentry = new ListEntry;
thisentry->entrydata = new char[size];
memcpy(thisentry->entrydata, newentry, size);
if (CurrEntry == NULL) {
thisentry->PrevEntry = NULL;
// ---- adding to the beginning of the list
if (FirstEntry != NULL) {
/* ---- already entries in this list ---- */
thisentry->NextEntry = FirstEntry;
FirstEntry->PrevEntry = thisentry;
}
else {
// ----- adding to an empty list
thisentry->NextEntry = NULL;
LastEntry = thisentry;
}
FirstEntry = thisentry;
}
else {
// ------- inserting into the list
thisentry->NextEntry = CurrEntry->NextEntry;
thisentry->PrevEntry = CurrEntry;
if (CurrEntry == LastEntry)
// ---- adding to the end of the list
LastEntry = thisentry;
else
// ---- inserting between existing entries
CurrEntry->NextEntry->PrevEntry = thisentry;
CurrEntry->NextEntry = thisentry;
}
CurrEntry = thisentry;
}
// ---------- delete the current entry from the list
void LinkedList::delete_entry(void)
{
if (CurrEntry != NULL) {
if (CurrEntry->NextEntry != NULL)
CurrEntry->NextEntry->PrevEntry = CurrEntry->PrevEntry;
else
LastEntry = CurrEntry->PrevEntry;
if (CurrEntry->PrevEntry != NULL)
CurrEntry->PrevEntry->NextEntry = CurrEntry->NextEntry;
else
FirstEntry = CurrEntry->NextEntry;
delete CurrEntry->entrydata;
ListEntry *hold = CurrEntry->NextEntry;
delete CurrEntry;
CurrEntry = hold;
}
}
// ---- get the first entry in the list
void *LinkedList::getfirst(void)
{
CurrEntry = FirstEntry;
return CurrEntry == NULL ? NULL : CurrEntry->entrydata;
}
// ---- get the next entry in the list
void *LinkedList::getnext(void)
{
if (CurrEntry == NULL)
CurrEntry = FirstEntry;
else
CurrEntry = CurrEntry->NextEntry;
return CurrEntry == NULL ? NULL : CurrEntry->entrydata;
}
// ---- get the previous entry in the list
void *LinkedList::getprev(void)
{
if (CurrEntry == NULL)
CurrEntry = LastEntry;
else
CurrEntry = CurrEntry->PrevEntry;
return CurrEntry == NULL ? NULL : CurrEntry->entrydata;
}
// ---- get the last entry in the list
void *LinkedList::getlast(void)
{
CurrEntry = LastEntry;
return CurrEntry == NULL ? NULL : CurrEntry->entrydata;
}
[LISTING THREE]
// -------- demolist.cpp
#include
#include "strings.h"
#include "linklist.h"
void collectnames(LinkedList& namelist);
int menu(void);
void displaynames(LinkedList& namelist);
void stepforward(LinkedList& namelist);
void stepbackward(LinkedList& namelist);
string insertname(LinkedList& namelist);
void main(void)
{
cout << "Enter some names followed by \"end\"\n";
// ------ a linked list of names
LinkedList namelist;
collectnames(namelist);
int key = 0;
while (key != 6) {
switch (key = menu()) {
case 1:
displaynames(namelist);
break;
case 2:
stepforward(namelist);
break;
case 3:
stepbackward(namelist);
break;
case 4:
insertname(namelist);
break;
case 5:
namelist.delete_entry();
break;
case 6:
cout << "Quitting...";
break;
default:
break;
}
}
}
void collectnames(LinkedList& namelist)
{
// ------- until the user types "end"
while (insertname(namelist) != "end")
;
}
int menu(void)
{
cout << "\n1 = display the names";
cout << "\n2 = step forward through the names";
cout << "\n3 = step backward through the names";
cout << "\n4 = insert a name";
cout << "\n5 = delete the current name";
cout << "\n6 = quit";
cout << "\nEnter selection: ";
int key;
cin >> key;
return key;
}
// ------ read the names in a list and display them
void displaynames(LinkedList& namelist)
{
cout << "------ NAME LIST ------\n";
char *name = namelist.getfirst();
while (name != NULL) {
cout << name << "\n";
name = namelist.getnext();
}
cout << "-----------------------\n";
}
// ------- step forward through the list of names
void stepforward(LinkedList& namelist)
{
char *name = namelist.getnext();
cout << (name ? name : "-- End of list --") << "\n";
}
// ------- step backwardward through the list of names
void stepbackward(LinkedList& namelist)
{
char *name = namelist.getprev();
cout << (name ? name : "-- Beginning of list --") << "\n";
}
// ------- insert a name into the list
string insertname(LinkedList& namelist)
{
cout << "Enter a name: ";
// ----- a string to hold one name
string name(80);
// ------- read a name
cin >> name.stradr();
// ------- add it to the list
if (name != "end")
namelist.addentry(name.stradr(), name.length());
return name;
}
Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!
This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.
But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: http://www.os2museum.com/wp/mtswslnk/