/*------------------------------------------------------------------*/
/* stackadt.c:  A Stack ADT                                         */
/*------------------------------------------------------------------*/

#include <assert.h>
#include <stdlib.h>
#include "stackadt.h"

#define MAX_STACK_SIZE 100

struct Stack 
{
   int piContents[MAX_STACK_SIZE];
   int iTop;
};

/*------------------------------------------------------------------*/

Stack_T Stack_new(void)

/* Return a new Stack_T. */
 
{
  Stack_T oStack;
  oStack = (Stack_T)malloc(sizeof(*oStack));
  assert(oStack != NULL);
  oStack->iTop = 0; 
  return oStack; 
}

/*------------------------------------------------------------------*/

void Stack_free(Stack_T oStack)

/* Free oStack. */

{
   if (oStack == NULL)
      return;
   free(oStack);
}

/*------------------------------------------------------------------*/

void Stack_push(Stack_T oStack, int iItem) 

/* Push iItem onto oStack. 
   It is a checked runtime error for oStack to be NULL or full. */

{
   assert(oStack != NULL);
   assert(! Stack_isFull(oStack));

   oStack->piContents[oStack->iTop] = iItem;
   oStack->iTop++;
}

/*------------------------------------------------------------------*/

int Stack_pop(Stack_T oStack) 

/* Pop oStack, and return the popped item.
   It is a checked runtime error for oStack to be NULL or empty. */ 

{
   assert(oStack != NULL);
   assert(! Stack_isEmpty(oStack));

   oStack->iTop--;
   return oStack->piContents[oStack->iTop];
}

/*------------------------------------------------------------------*/
 
int Stack_isEmpty(Stack_T oStack) 

/* Return 1 (TRUE) iff oStack is empty. 
   It is a checked runtime error for oStack to be NULL. */

{
   assert(oStack != NULL);
   return oStack->iTop == 0; 
}

/*------------------------------------------------------------------*/
 
int Stack_isFull(Stack_T oStack) 

/* Return 1 (TRUE) iff oStack is full. 
   It is a checked runtime error for oStack to be NULL. */

{
   assert(oStack != NULL);
   return oStack->iTop == MAX_STACK_SIZE; 
}