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#ifndef ubi_StackQueue_H
#define ubi_StackQueue_H
/* ========================================================================== **
* ubi_StackQueue.h
*
* Copyright (C) 1997 by Christopher R. Hertel
*
* Email: crh@ubiqx.mn.org
* -------------------------------------------------------------------------- **
* This module implements simple queues and stacks using a singly linked
* list.
* -------------------------------------------------------------------------- **
*
* 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.
*
* -------------------------------------------------------------------------- **
* This module uses a singly-linked list to implement both a queue and a
* stack. For a queue, entries are added at the tail and removed from the
* head of the list. For a stack, the entries are entered and removed from
* the head of the list. A traversal of the list will always start at the
* head of the list and proceed toward the tail. This is all mind-numbingly
* simple, but I'm surprised by the number of programs out there which
* re-implement this a dozen or so times.
*
* Note: When the list header is initialized, the Tail pointer is set to
* point to the Head pointer. This simplifies the InsTail function
* at little or no cost to InsHead or Remove. The one problem is
* that you can't initialize a stack or queue headerby simply zeroing
* it out. One sure way to initialize the header is to call
* ubi_sqInit(). Another option would be something like this:
*
* static ubi_sqList MyList = { NULL, (ubi_sqNodePtr)&MyList, 0 };
*
* See ubi_sqInit() and the ubi_sqList structure for more info.
*
* -------------------------------------------------------------------------- **
*
* Revision 0.1 1997/10/24 02:48:23 crh
* Initial revision.
*
* ========================================================================== **
*/
#include <stdlib.h>
/* ========================================================================== **
* Typedefs...
*
* ubi_sqNode - This is the basic node structure.
* ubi_sqNodePtr - Pointer to a node.
* ubi_sqList - This is the stack & queue header structure.
* ubi_sqListPtr - Pointer to a stack & queue header.
*
*/
typedef struct ubi_sqListNode
{
struct ubi_sqListNode *Next;
} ubi_sqNode;
typedef ubi_sqNode *ubi_sqNodePtr;
typedef struct
{
ubi_sqNodePtr Head;
ubi_sqNodePtr Tail;
unsigned long count;
} ubi_sqList;
typedef ubi_sqList *ubi_sqListPtr;
/* ========================================================================== **
* Macros...
*
* ubi_sqEnqueue - Add a new node at the tail of a queue.
* ubi_sqDequeue - Remove a node from the head of the queue.
* ubi_sqPush - Add a new node at the head of the queue.
* ubi_sqPop - Remove a node from the head of the queue (same as Dequeue).
* ubi_sqFirst - Return a pointer to the frontmost node in the queue.
* ubi_sqNext - Given a node, return a pointer to the next node.
* ubi_sqLast - Return a pointer to the last (valid) node in the queue.
*
* Note that all of these provide type casting of the parameters. The
* Enqueue/Dequeue macros are nothing more than nice front-ends to the
* Insert and Remove operations.
*
*/
#define ubi_sqEnqueue( L, N ) \
ubi_sqInsTail( (ubi_sqListPtr)(L), (ubi_sqNodePtr)(N) )
#define ubi_sqDequeue( L ) ubi_sqRemove( (ubi_sqListPtr)(L) )
#define ubi_sqPush( L, N ) \
ubi_sqInsHead( (ubi_sqListPtr)(L), (ubi_sqNodePtr)(N) )
#define ubi_sqPop ubi_sqDequeue
#define ubi_sqFirst( L ) (((ubi_sqListPtr)(L))->Head)
#define ubi_sqNext( N ) (((ubi_sqNodePtr)(N))->Next)
#define ubi_sqLast( L ) \
( (((ubi_sqListPtr)(L))->Head) ? (((ubi_sqListPtr)(L))->Tail) : NULL )
/* ========================================================================== **
* Function prototypes...
*/
ubi_sqListPtr ubi_sqInit( ubi_sqListPtr ListPtr );
/* ------------------------------------------------------------------------ **
* Initialize a stack & queue header.
*
* Input: ListPtr - A pointer to the list header that is to be
* initialized for use.
*
* Output: A pointer to the initialized list header (i.e., same as
* <ListPtr>).
*
* ------------------------------------------------------------------------ **
*/
ubi_sqNodePtr ubi_sqInsHead( ubi_sqListPtr ListPtr, ubi_sqNodePtr New );
/* ------------------------------------------------------------------------ **
* Insert a new node at the head of the list (push).
*
* Input: ListPtr - A pointer to the stack into which the node is to
* be inserted.
* New - Pointer to the node that is to be pushed onto the
* stack.
*
* Output: A pointer to the node that was added to the list (i.e., same
* same as <New>).
*
* ------------------------------------------------------------------------ **
*/
ubi_sqNodePtr ubi_sqInsTail( ubi_sqListPtr ListPtr, ubi_sqNodePtr New );
/* ------------------------------------------------------------------------ **
* Add a new node to the tail of the list (enqueue).
*
* Input: ListPtr - A pointer to the queue into which the node is to
* be inserted.
* New - Pointer to the node that is to be enqueued.
*
* Output: A pointer to the node that was inserted into the queue (i.e.,
* the same as <New>).
*
* ------------------------------------------------------------------------ **
*/
ubi_sqNodePtr ubi_sqRemove( ubi_sqListPtr ListPtr );
/* ------------------------------------------------------------------------ **
* Remove the frontmost entry from the queue, or topmost entry from the
* stack.
*
* Input: ListPtr - A pointer to the list from which the node is to be
* removed.
*
* Output: A pointer to the node that was removed.
*
* ------------------------------------------------------------------------ **
*/
/* ================================ The End ================================= */
#endif /* ubi_StackQueue_H */
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