91 lines
1.9 KiB
C
91 lines
1.9 KiB
C
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/*
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* stack.c -- Implementation for stack functions for use by extensions.
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*/
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/*
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* Copyright (C) 2012, 2013 the Free Software Foundation, Inc.
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*
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* This file is part of GAWK, the GNU implementation of the
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* AWK Programming Language.
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*
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* GAWK is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* GAWK is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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*/
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#include <stdlib.h>
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#include "stack.h"
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#define INITIAL_STACK 20
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static size_t size;
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static void **stack;
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static int index = -1;
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/* stack_empty --- return true if stack is empty */
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int
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stack_empty()
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{
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return index < 0;
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}
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/* stack_top --- return top object on the stack */
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void *
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stack_top()
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{
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if (stack_empty() || stack == NULL)
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return NULL;
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return stack[index];
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}
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/* stack_pop --- pop top object and return it */
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void *
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stack_pop()
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{
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if (stack_empty() || stack == NULL)
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return NULL;
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return stack[index--];
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}
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/* stack_push --- push an object onto the stack */
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int stack_push(void *object)
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{
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void **new_stack;
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size_t new_size = 2 * size;
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if (stack == NULL) {
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stack = (void **) malloc(INITIAL_STACK * sizeof(void *));
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if (stack == NULL)
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return 0;
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size = INITIAL_STACK;
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} else if (index + 1 >= size) {
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if (new_size < size)
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return 0;
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new_stack = realloc(stack, new_size * sizeof(void *));
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if (new_stack == NULL)
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return 0;
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size = new_size;
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stack = new_stack;
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}
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stack[++index] = object;
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return 1;
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}
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