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/* stack.c -- Stack routines for Khepera
* Created: Wed Nov 9 19:40:00 1994 by faith@cs.unc.edu
* Revised: Sun Nov 19 13:30:19 1995 by faith@cs.unc.edu
* Copyright 1994, 1995 Rickard E. Faith (faith@cs.unc.edu)
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Library General Public License as published
* by the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* $Id: stack.c,v 1.4 1996/02/26 15:39:12 faith Exp $
*
* \section{Stack Routines}
*
* \intro The stack routines provide support for a general stack of
* pointers to "void". Because of the simplicity of the stack object, no
* statistics are maintained. (Althought the list routines can also be used
* as a stack, the stack implemented here is more efficient.)
*
*/
#include "maaP.h"
#include "obstack.h"
#ifdef DMALLOC_FUNC_CHECK
/* Must be true functions */
#define obstack_chunk_alloc malloc
#define obstack_chunk_free free
#else
#define obstack_chunk_alloc xmalloc
#define obstack_chunk_free xfree
#endif
typedef struct data {
const void *datum;
struct data *prev;
} *dataType;
typedef struct stack {
struct data *data;
struct obstack *obstack;
} *stackType;
/* \doc |stk_create| initializes a stack object. */
stk_Stack stk_create( void )
{
stackType s;
s = xmalloc( sizeof( struct stack ) );
s->data = NULL;
s->obstack = xmalloc( sizeof( struct obstack ) );
obstack_init( s->obstack );
return s;
}
/* \doc |stk_destroy| destroys all memory associated with the |stack|. The
memory used by data is \emph{not} freed---this memory is the
responsibility of the user. */
void stk_destroy( stk_Stack stack )
{
stackType s = (stackType)stack;
obstack_free( s->obstack, NULL );
xfree( s->obstack );
xfree( stack ); /* terminal */
}
/* \doc |stk_push| places |datum| on the top of the |stack|. */
void stk_push( stk_Stack stack, void *datum )
{
stackType s = (stackType)stack;
dataType d = (dataType)obstack_alloc( s->obstack, sizeof( struct data ) );
d->datum = datum;
d->prev = s->data;
s->data = d;
}
/* \doc |stk_pop| removes the top of the |stack| and returns the pointer.
If the |stack| is empty, |stk_pop| returns "NULL". */
void *stk_pop( stk_Stack stack )
{
stackType s = (stackType)stack;
void *datum = NULL;
if (s->data) {
dataType old = s->data;
datum = (void *)old->datum; /* Discard const */
s->data = s->data->prev;
obstack_free( s->obstack, old );
}
return datum;
}
/* \doc |stk_top| returns a pointer to the datum on the top of the |stack|,
but does \emph{not} remove this datum from the |stack|. If the |stack|
is empty, |stk_pop| returns "NULL". */
void *stk_top( stk_Stack stack )
{
stackType s = (stackType)stack;
if (s->data)
return (void *)s->data->datum; /* Discard const */
return NULL;
}
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