RequestQueue.pas

Unit RequestQueue;
interface
Const

NULLQ = NIL;

type
tCode = string;
tPosQ = ^tNodoQ;
tItemQ = record    
	  code: tCode;
      param1: string;
      param2: string;
      param3: string;
		end;
  tNodoQ = record
    item: tItemQ;
    next: tPosQ;
  end;
  tQueue = record
  first: tPosQ;
  last: tPosQ;
  end;
  

procedure createEmptyQueue(var queue:tQueue);
function isEmptyQueue(Queue:tQueue):boolean;
function front(queue:tQueue):tItemQ;
function enqueue(item:tItemQ;var queue:tqueue):boolean;
procedure dequeue(var queue:tQueue);




implementation

(**********************************************************************)

Function isEmptyQueue (queue:tQueue):boolean;
(*Determina si la cola está vacía.*)
begin
	isEmptyQueue := (queue.first = NULLQ); 
end;

(**********************************************************************)


(**********************************************************************)

procedure createEmptyQueue (var queue:tqueue);
(*Crea una cola vacía.
PostCD: La cola queda inicializada y vacía.*)
begin
	queue.first:=NULLQ;
	queue.last:=NULLQ;
	
end;

(**********************************************************************)


(**********************************************************************)


Function front(queue:tQueue):tItemq;
(*Devuelve el contenido (tItemQ) 
* del frente de la cola (i.e. el elemento más antiguo).
PreCD: la cola no está vacía.*)
Begin
	front := queue.first^.item;
End;
(**********************************************************************)


(**********************************************************************)

procedure dequeue(var queue: tQueue);
(*Elimina el elemento que está en el frente de la cola.
PreCD: la cola no está vacía.*)
var
pos :tPosQ;
begin
			pos:=queue.first;
			queue.first := queue.first^.next;
			dispose(pos);
			pos := NULLQ;
			
end;
(**********************************************************************)


(************************************************************************)
function enqueue(item:tItemQ;var queue:tQueue):boolean;
(*Inserta un nuevo elemento (tItemQ) en la cola. 
* Devuelve false si no hay memoria 
* suficiente para realizar la operación.*)
var
	p:tPosq;
Begin
	
	new(P);
	p^.item:=item; //Creamos el elemento a agregar.
	p^.next:=NULLQ;
	if p <> NULLQ //Si hay memoria se agrega a la cola.
	then begin
		enqueue:= true;
	
	if isEmptyqueue(queue) //Si la cola está vacia...
	then
		queue.first := p //La cola está vacia.
	else 
		queue.last^.next := p;
		queue.last := p; //La cola tiene elementos.
	end
	else enqueue := false;
end;
(**********************************************************************)
End.



Begin
end.

TestQueue.pas

program TestQueue;

uses sysutils,RequestQueue;


// --------------------------------------------------------------------------------------
// Read a file text with the different task to do by the program                      ---
// It prints a message indicating the task to perform with the required parameters    ---
// The allowed tasks are: [C]reate, [Q]uit, [T]ransform, [F]avorites
// [A]buse, [D]iscard, [L]ike, [R]emove, [S]tatus, [U]pload
// --------------------------------------------------------------------------------------

procedure readTasks(taskFile:string);
var
   fileId:Text;
   line:string;
	 UL : tItemQ;
	 QRequest: tQueue;
	 i:integer;
begin
       {$i-}
       assign(fileId, taskFile);
       reset(fileId);
       {$i+}
       if (IOResult<>0) then begin
           writeln('**** Reading. Error when trying to open ', taskFile);
           halt(1);
       end;
	createEmptyQueue(QRequest);
	
	writeln('**** Starting bumping of file');
	writeln;
	i:=0;
    While (not EOF(fileId)) do
    begin
        
        readln(fileId, line);
        UL.code := trim(copy(line, 1, 2));
        UL.param1 := trim(copy(line, 3, 10));
        UL.param2 := trim(copy(line, 14, 15));
        UL.param3 := trim(copy(line, 30, 20));
        enqueue(UL,QRequest);
        i:=i+1;
        writeln('*Lines into queue ',i);
    end;
    
    writeln;
    writeln('****Starting showing Request Queue');
    writeln;
    
    while not(IsEmptyQueue(QRequest)) do begin
      writeln('*',front(QRequest).code,' ',front(QRequest).param1,' ',front(QRequest).param2,' ',front(QRequest).param3,' ');
      dequeue(QRequest);
      end;
      if IsEmptyQueue(QRequest)
		then writeln('**** The queue is empty');
end; 
	

// ---------------------------------------------------------------------------------

BEGIN
    
    if (paramCount>0) then 
        //Use the file specified as parameter
        readTasks(ParamStr(1)) 
    else
        //Use a "hard-coded" filename
        readTasks('create-users.txt');
	writeln;
	writeln('Press any key to exit....');
	
	readln;
END.