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/*** stack.c ******************************************************************
**
** This file is part of BibTool.
** It is distributed under the GNU General Public License.
** See the file COPYING for details.
**
** (c) 1996-2017 Gerd Neugebauer
**
** Net: gene@gerd-neugebauer.de
**
** This program 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 2, or (at your option)
** any later version.
**
** This program 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., 675 Mass Ave, Cambridge, MA 02139, USA.
**
**-----------------------------------------------------------------------------
** Description:
** This module provides a single stack of strings. There are two
** operations on this stack, namely to push a string onto the
** stack and a pop operation to get the topmost element from the
** stack and remove it or to get a signal that the stack is
** empty.
**
** The stack is implemented as an array which grows on demand.
** Currently the memory of the stack is not returned to the
** operating system. This seems to be not problemeatic since this
** memory is not assumed to be really large. Normally just a few
** strings are pushed to the stack at any time.
**
******************************************************************************/
#include <bibtool/general.h>
#include <bibtool/error.h>
#include <bibtool/stack.h>
/*****************************************************************************/
/* Internal Programs */
/*===========================================================================*/
#ifdef __STDC__
#define _ARG(A) A
#else
#define _ARG(A) ()
#endif
Symbol pop_string _ARG((void)); /* stack.c */
void push_string _ARG((Symbol s)); /* stack.c */
/*****************************************************************************/
/* External Programs */
/*===========================================================================*/
/*---------------------------------------------------------------------------*/
static Symbol *stack;
static size_t stack_size = 0;
static size_t stack_ptr = 0;
/*-----------------------------------------------------------------------------
** Function: push_string()
** Purpose: Push a string onto the stack. Only the memory for the
** stack is allocated. The string is stored as pointer to
** existing memory. No copy of the string is made.
**
** If no memory is left then an error is raised and the program
** is terminated.
** Arguments:
** s String to push to the stack.
** Returns: nothing
**___________________________________________________ */
void push_string(s) /* */
register Symbol s; /* */
{ /* */
if ( stack_ptr >= stack_size ) /* */
{ stack_size += 16; /* */
stack = (stack_ptr == 0 /* */
?(Symbol*)malloc((size_t)(stack_size*sizeof(Symbol)))/* */
:(Symbol*)realloc((char*)stack, /* */
(size_t)(stack_size*sizeof(Symbol))));/* */
if ( stack == NULL ) /* */
{ OUT_OF_MEMORY("stack"); } /* */
} /* */
DebugPrint2("pushing ", SymbolValue(s)); /* */
stack[stack_ptr++] = s; /* */
} /*------------------------*/
/*-----------------------------------------------------------------------------
** Function: pop_string()
** Purpose: Pop a string from the stack. It the stack is empty
** then |NULL| is returned. Thus the |NULL| value should
** not be pushed to the stack since this can be confused
** with the end of the stack.
** Arguments: none
** Returns: The old top element or |NULL| if the stack is empty.
**___________________________________________________ */
Symbol pop_string() /* */
{ /* */
if ( stack_ptr <= 0 ) return NO_SYMBOL; /* */
/* */
DebugPrint2("poping ", /* */
SymbolValue(stack[stack_ptr-1])); /* */
return stack[--stack_ptr]; /* */
} /*------------------------*/
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