裸机中环形队列与RTOS中消息队列的区别

typedef struct ringq{   int head; /* 头部，出队列方向*/   int tail; /* 尾部，入队列方向*/    int tag ;   int size ; /* 队列总尺寸 */   int space[RINGQ_MAX]; /* 队列空间 */}RINGQ;

q->head = q->tail = q->tag = 0;

( q->head == q->tail) && (q->tag == 0)

 ((q->head == q->tail) && (q->tag == 1))

q->tail =  (q->tail + 1) % q->size ;

q->head =  (q->head + 1) % q->size

#ifndef __RINGQ_H__#define __RINGQ_H__
#ifdef __cplusplusextern "C" {#endif 
#define QUEUE_MAX 20
typedef struct ringq{   int head; /* 头部，出队列方向*/   int tail; /* 尾部，入队列方向*/    int tag ; /* 为空还是为满的标志位*/    int size ; /* 队列总尺寸 */   int space[QUEUE_MAX]; /* 队列空间 */}RINGQ;
/*   第一种设计方法:     当head == tail 时，tag = 0 为空，等于 = 1 为满。*/
extern int ringq_init(RINGQ * p_queue);
extern int ringq_free(RINGQ * p_queue);

/* 加入数据到队列 */extern int ringq_push(RINGQ * p_queue,int data);
/* 从队列取数据 */extern int ringq_poll(RINGQ * p_queue,int *p_data);

#define ringq_is_empty(q) ( (q->head == q->tail) && (q->tag == 0))
#define ringq_is_full(q) ( (q->head == q->tail) && (q->tag == 1))
#define print_ringq(q) printf("ring head %d,tail %d,tag %d\n", q->head,q->tail,q->tag);#ifdef __cplusplus}#endif 
#endif /* __RINGQ_H__ */

#include #include "ringq.h"
int ringq_init(RINGQ * p_queue){   p_queue->size = QUEUE_MAX ;
   p_queue->head = 0;   p_queue->tail = 0;
   p_queue->tag = 0;
   return 0;}
int ringq_free(RINGQ * p_queue){  return 0;}

int ringq_push(RINGQ * p_queue,int data){  print_ringq(p_queue);
  if(ringq_is_full(p_queue))   {
     printf("ringq is full\n");     return -1;   }
   p_queue->space[p_queue->tail] = data;
   p_queue->tail = (p_queue->tail + 1) % p_queue->size ;
   /* 这个时候一定队列满了*/   if(p_queue->tail == p_queue->head)    {       p_queue->tag = 1;    }
    return p_queue->tag ;  }
int ringq_poll(RINGQ * p_queue,int * p_data){   print_ringq(p_queue);  if(ringq_is_empty(p_queue))   {
      printf("ringq is empty\n");     return -1;   }
   *p_data = p_queue->space[p_queue->head];
   p_queue->head = (p_queue->head + 1) % p_queue->size ;
    /* 这个时候一定队列空了*/   if(p_queue->tail == p_queue->head)    {       p_queue->tag = 0;    }        return p_queue->tag ;}

xQueue = xQueueCreate(QUEUE_LEN, QUEUE_SIZE);