1 files changed, 90 insertions, 0 deletions
diff --git a/extension/stack.c b/extension/stack.c
new file mode 100644
index 00000000..6150442c
--- /dev/null
+++ b/extension/stack.c
@@ -0,0 +1,90 @@
+/*
+ * stack.c -- Implementation for stack functions for use by extensions.
+ */
+
+/* 
+ * Copyright (C) 2012, 2013 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;
+}