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/******************************************************************************
** $Id: stack.c,v 1.8 2012-01-26 19:54:21 gene Exp $
**=============================================================================
**
** This file is part of BibTool.
** It is distributed under the GNU General Public License.
** See the file COPYING for details.
**
** (c) 1996-2012 Gerd Neugebauer
**
** Net: gene@gerd-neugebauer.de
**
**-----------------------------------------------------------------------------
** 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>
/*****************************************************************************/
/* Internal Programs */
/*===========================================================================*/
#ifdef __STDC__
#define _ARG(A) A
#else
#define _ARG(A) ()
#endif
Uchar * pop_string _ARG((void)); /* stack.c */
void push_string _ARG((Uchar * s)); /* stack.c */
/*****************************************************************************/
/* External Programs */
/*===========================================================================*/
/*---------------------------------------------------------------------------*/
static Uchar **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 Uchar *s; /* */
{ /* */
if ( stack_ptr >= stack_size ) /* */
{ stack_size += 16; /* */
stack = (stack_ptr == 0 /* */
?(Uchar**)malloc((size_t)(stack_size*sizeof(Uchar*)))/* */
:(Uchar**)realloc((char*)stack, /* */
(size_t)(stack_size*sizeof(Uchar*))));/* */
if ( stack == NULL ) /* */
{ OUT_OF_MEMORY("stack"); } /* */
} /* */
stack[stack_ptr++] = s; /* */
DebugPrint2("pushing ",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.
**___________________________________________________ */
Uchar * pop_string() /* */
{ /* */
if ( stack_ptr <= 0 ) return NULL; /* */
/* */
DebugPrint2("poping ",stack[stack_ptr-1]); /* */
return stack[--stack_ptr]; /* */
} /*------------------------*/
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