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/* stack.c -- Stack routines for Khepera
* Created: Wed Nov 9 19:40:00 1994 by faith@dict.org
* Copyright 1994, 1995, 2002 Rickard E. Faith (faith@dict.org)
* Copyright 2002-2008 Aleksey Cheusov (vle@gmx.net)
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* \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"
typedef struct data {
const void *datum;
struct data *prev;
} *dataType;
typedef struct stack {
struct data *data;
} *stackType;
/* \doc |stk_create| initializes a stack object. */
stk_Stack stk_create(void)
{
stackType s;
s = xmalloc(sizeof(struct stack));
s->data = NULL;
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)
{
while (!stk_isempty(stack)){
stk_pop(stack);
}
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)malloc(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 = __UNCONST(old->datum); /* Discard const */
s->data = s->data->prev;
free(old);
}
return datum;
}
/* \doc |stk_isempty| return 1 if |stack| is empty, or 0 otherwise.
*/
int stk_isempty(stk_Stack stack)
{
stackType s = (stackType)stack;
if (s->data) {
return 0;
}else{
return 1;
}
}
/* \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 __UNCONST(s->data->datum); /* Discard const */
return NULL;
}
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