/*
* File: queue.h
* Purpose: Implement a first in, first out linked list
*
* Notes:
*/
#ifndef _QUEUE_H_
#define _QUEUE_H_
/********************************************************************/
/*
* Individual queue node
*/
typedef struct NODE
{
struct NODE *
next;
} QNODE;
/*
* Queue Struture - linked list of qentry items
*/
typedef struct
{
QNODE *
head;
QNODE *
tail;
} QUEUE;
/*
* Functions provided by queue.c
*/
void queue_init( QUEUE *
);
int queue_isempty( QUEUE *
);
void queue_add( QUEUE *, QNODE *
);
QNODE* queue_remove( QUEUE *
);
QNODE* queue_peek( QUEUE *
);
void queue_move( QUEUE *, QUEUE *
);
/********************************************************************/
#endif /* _QUEUE_H_ */
/*
* File: queue.c
* Purpose: Implement a first in, first out linked list
*
* Notes:
*/
#include "queue.h"
/********************************************************************/
/*
* Initialize the specified queue to an empty state
*
* Parameters:
* q Pointer to queue structure
*/
void queue_init( QUEUE *
q )
{
q->head =
NULL;
}
/********************************************************************/
/*
* Check for an empty queue
*
* Parameters:
* q Pointer to queue structure
*
* Return Value:
* 1 if Queue is empty
* 0 otherwise
*/
int queue_isempty( QUEUE *
q )
{
return ( q->head ==
NULL );
}
/********************************************************************/
/*
* Add an item to the end of the queue
*
* Parameters:
* q Pointer to queue structure
* node New node to add to the queue
*/
void queue_add( QUEUE *q, QNODE *
node )
{
if ( queue_isempty( q ) )
{
q->head = q->tail =
node;
}
else
{
q->tail->next =
node;
q->tail =
node;
}
node->next =
NULL;
}
/********************************************************************/
/*
* Remove and return first (oldest) entry from the specified queue
*
* Parameters:
* q Pointer to queue structure
*
* Return Value:
* Node at head of queue - NULL if queue is empty
*/
QNODE*
queue_remove( QUEUE *
q )
{
QNODE *
oldest;
if ( queue_isempty( q ) )
return NULL;
oldest = q->
head;
q->head = oldest->
next;
return oldest;
}
/********************************************************************/
/*
* Peek into the queue and return pointer to first (oldest) entry.
* The queue is not modified
*
* Parameters:
* q Pointer to queue structure
*
* Return Value:
* Node at head of queue - NULL if queue is empty
*/
QNODE*
queue_peek( QUEUE *
q )
{
return q->
head;
}
/********************************************************************/
/*
* Move entire contents of one queue to the other
*
* Parameters:
* src Pointer to source queue
* dst Pointer to destination queue
*/
void queue_move( QUEUE *dst, QUEUE *
src )
{
if ( queue_isempty( src ) )
return;
if ( queue_isempty( dst ) )
dst->head = src->
head;
else
dst->tail->next = src->
head;
dst->tail = src->
tail;
src->head =
NULL;
return;
}
/********************************************************************/
转载于:https://www.cnblogs.com/shangdawei/archive/2013/04/22/3036804.html
