1 files changed, 100 insertions, 0 deletions

diff --git a/stack2.c b/stack2.c
new file mode 100644
index 0000000..57dce4f
--- /dev/null
+++ b/stack2.c
@@ -0,0 +1,100 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+#include "util.h"
+
+typedef int T;
+
+struct stack {
+        T *array;
+        size_t sz, p;
+};
+
+void
+stack_init(struct stack *stack)
+{
+        stack->array = NULL;
+        stack->sz = 0;
+        stack->p = 0;
+}
+
+bool
+stack_push(struct stack *stack, T data)
+{
+        if ( stack->array == NULL ) {
+                if ( (stack->array = malloc(10 * sizeof(*stack->array))) != NULL ) {
+                        stack->sz = 10;
+                        stack->p = 0;
+                }
+                else {
+                        ERROR("out of memory");
+                        return false;
+                }
+        }
+
+        if ( stack->p == stack->sz ) {
+                size_t new_sz;
+                T *new_array;
+
+                if ( (new_array = realloc(stack->array, (new_sz = (stack->sz * 3 / 2)) * sizeof(*stack->array))) != NULL ) {
+                        stack->array = new_array;
+                        stack->sz = new_sz;
+                }
+                else {
+                        ERROR("out of memory");
+                        return false;
+                }
+        }
+
+        stack->array[stack->p++] = data;
+        return true;
+}
+
+bool
+stack_pop(struct stack *stack, T *data)
+{
+        if ( stack->p != 0 ) {
+                *data = stack->array[--stack->p];
+                return true;
+        }
+        else
+                return false;
+}
+
+bool
+stack_empty(struct stack *stack)
+{
+        return stack->p == 0;
+}
+
+void
+stack_free(struct stack *stack)
+{
+        free(stack->array);
+}
+
+int
+main()
+{
+        struct stack stack[1];
+
+        stack_init(stack);
+
+        for ( int i = 0; i != 20; ++i )
+                stack_push(stack, i);
+
+        while ( !stack_empty(stack) ) {
+                int i;
+
+                if ( stack_pop(stack, &i) )
+                        printf("%d\n", i);
+                else
+                        ERROR("this shouldn't happen!");
+        }
+
+        stack_free(stack);
+
+        return EXIT_SUCCESS;
+}
+