stack.c

   1 #include <stdlib.h>
   2 #include "stack.h"
   3
   4 typedef struct _Stack {
   5         void** elems;
   6         int size;
   7 } Stack;
   8
   9 Stack* stack_init() {
  10         Stack* s = malloc(sizeof(Stack));
  11         s->size = 0;
  12         s->elems = NULL;
  13         return s;
  14 }
  15
  16 void* stack_pop(Stack* stack) {
  17         if (stack_empty(stack))
  18                 return NULL;
  19         stack->size -= 1;
  20         void* elem = stack->elems[stack->size];
  21         stack->elems[stack->size] = NULL;
  22         stack->elems = realloc(stack->elems, stack->size * sizeof(void*));
  23
  24         return elem;
  25 }
  26
  27 void stack_push(Stack* stack, void* elem) {
  28         if (stack == NULL)
  29                 return;
  30
  31         stack->size += 1;
  32         stack->elems = realloc(stack->elems, stack->size * sizeof(void*));
  33         stack->elems[stack->size - 1] = elem;
  34 }
  35
  36 void* stack_peek(Stack* stack) {
  37         if (stack_empty(stack))
  38                 return NULL;
  39         return stack->elems[stack->size - 1];
  40 }
  41
  42 bool stack_empty(Stack* stack) {
  43         return (stack == NULL || stack->size == 0);
  44 }
  45
  46 void** stack_clear(Stack** stack) {
  47         if (*stack == NULL)
  48                 return NULL;
  49         void** elems = (*stack)->elems;
  50         free(*stack);
  51         *stack = NULL;
  52         return elems;
  53 }