Advanced Oracle PL/SQL Programming with Packages

5.24. PLVstk: Stack Manager

The PLVstk (PL/Vision STacK manager) package is a generic manager for both first-in-first-out (FIFO) and last-in-last-out (LIFO) stacks; it is built on PLVlst. See the companion disk (see http://examples.oreilly.com/advoracle) for details.

5.24.1. Package constants

defstk CONSTANT VARCHAR2(5) := 'stack';

The name of the default stack.

lifo CONSTANT VARCHAR2(4) := 'LIFO';

Indicates that you are working with a last-in-first-out stack. Used in calls to pop.

fifo CONSTANT VARCHAR2(4) := 'FIFO';

Indicates that you are working with a first-in-first-out stack. Used in calls to pop.

5.24.2. Creating and destroying stacks

PROCEDURE make 
   (stack_in IN VARCHAR2 := defstk,
    overwrite_in IN BOOLEAN := TRUE);

Allocates storage for a stack of up to 1,000 items with the specified name. By default, if the stack already exists it will be reinitialized to an empty stack.

PROCEDURE destroy (stack_in IN VARCHAR2 := defstk);

Releases all memory associated with this stack.

5.24.3. Modifying stack contents

PROCEDURE push (item_in IN VARCHAR2, stack_in IN VARCHAR2 := defstk);

Pushes an item onto the specified stack.

PROCEDURE pop (value_out IN OUT VARCHAR2, 
    stack_in IN VARCHAR2 := defstk,
    stack_type_in IN VARCHAR2 := lifo);

Pops an item off the top (LIFO) or bottom (FIFO) of the stack.

5.24.4. Analyzing stack contents

FUNCTION nitems (stack_in IN VARCHAR2 := defstk)
RETURN INTEGER;

Returns the number of items currently in the stack.

FUNCTION itemin (stack_in ...