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/*
* stack.c -- Implementation for stack functions for use by extensions.
*/
/*
* Copyright (C) 2012 the Free Software Foundation, Inc.
*
* This file is part of GAWK, the GNU implementation of the
* AWK Programming Language.
*
* GAWK is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* GAWK is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
*/
#include <stdlib.h>
#include "stack.h"
#define INITIAL_STACK 20
static size_t size;
static void **stack;
static int index = -1;
/* stack_empty --- return true if stack is empty */
int
stack_empty()
{
return index < 0;
}
/* stack_top --- return top object on the stack */
void *
stack_top()
{
if (stack_empty() || stack == NULL)
return NULL;
return stack[index];
}
/* stack_pop --- pop top object and return it */
void *
stack_pop()
{
if (stack_empty() || stack == NULL)
return NULL;
return stack[index--];
}
/* stack_push --- push an object onto the stack */
int stack_push(void *object)
{
void **new_stack;
size_t new_size = 2 * size;
if (stack == NULL) {
stack = (void **) malloc(INITIAL_STACK * sizeof(void *));
if (stack == NULL)
return 0;
size = INITIAL_STACK;
} else if (index + 1 >= size) {
if (new_size < size)
return 0;
new_stack = realloc(stack, new_size * sizeof(void *));
if (new_stack == NULL)
return 0;
size = new_size;
stack = new_stack;
}
stack[++index] = object;
return 1;
}
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