C的双缓存队列怎么写
时间: 2023-09-10 20:04:42 浏览: 50
### 回答1:
双缓存队列(Double-Buffer Queue)是一种常用的数据结构,可以在多线程环境下保证数据同步和安全。下面是一个C语言实现的例子:
```
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define QUEUE_SIZE 10
#define THREAD_COUNT 2
int buffer1[QUEUE_SIZE];
int buffer2[QUEUE_SIZE];
int in1 = 0;
int out1 = 0;
int in2 = 0;
int out2 = 0;
int count = 0;
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t not_full = PTHREAD_COND_INITIALIZER;
pthread_cond_t not_empty = PTHREAD_COND_INITIALIZER;
void *producer(void *arg) {
while (1) {
pthread_mutex_lock(&lock);
while (count == QUEUE_SIZE) {
pthread_cond_wait(¬_full, &lock);
}
buffer1[in1] = rand() % 100;
++in1;
in1 %= QUEUE_SIZE;
++count;
pthread_cond_signal(¬_empty);
pthread_mutex_unlock(&lock);
}
return NULL;
}
void *consumer(void *arg) {
while (1) {
pthread_mutex_lock(&lock);
while (count == 0) {
pthread_cond_wait(¬_empty, &lock);
}
buffer2[in2] = buffer1[out1];
++in2;
in2 %= QUEUE_SIZE;
++out1;
out1 %= QUEUE_SIZE;
--count;
pthread_cond_signal(¬_full);
pthread_mutex_unlock(&lock);
}
return NULL;
}
int main(void) {
pthread_t producers[THREAD_COUNT];
pthread_t consumers[THREAD_COUNT];
int i;
for (i = 0; i < THREAD_COUNT; ++i) {
pthread_create(&producers[i], NULL, producer, NULL);
pthread_create(&consumers[i], NULL, consumer, NULL);
}
for (i = 0; i < THREAD_COUNT; ++i) {
pthread_join(producers[i], NULL);
pthread_join(consumers[i], NULL);
}
return 0;
}
```
在这个例子中
### 回答2:
C的双缓存队列是一种数据结构,它具有两个队列,用于在两个并行执行的线程之间传递数据。其中一个队列作为生产者队列,用于接收生产者线程生成的数据;另一个队列作为消费者队列,用于消费者线程从中读取数据。
下面是一个简单的C语言代码示例,展示了如何实现双缓存队列:
```c
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#define SIZE 10
typedef struct {
int data[SIZE];
int front;
int rear;
int count;
pthread_mutex_t mutex;
pthread_cond_t full;
pthread_cond_t empty;
} DoubleBufferQueue;
// 初始化双缓存队列
void init(DoubleBufferQueue* queue) {
queue->front = 0;
queue->rear = 0;
queue->count = 0;
pthread_mutex_init(&queue->mutex, NULL);
pthread_cond_init(&queue->full, NULL);
pthread_cond_init(&queue->empty, NULL);
}
// 添加数据到生产者队列
void produce(DoubleBufferQueue* queue, int item) {
pthread_mutex_lock(&queue->mutex);
while (queue->count >= SIZE) {
pthread_cond_wait(&queue->full, &queue->mutex);
}
queue->data[queue->rear] = item;
queue->rear = (queue->rear + 1) % SIZE;
queue->count++;
pthread_cond_signal(&queue->empty);
pthread_mutex_unlock(&queue->mutex);
}
// 从消费者队列中读取数据
int consume(DoubleBufferQueue* queue) {
int item;
pthread_mutex_lock(&queue->mutex);
while (queue->count == 0) {
pthread_cond_wait(&queue->empty, &queue->mutex);
}
item = queue->data[queue->front];
queue->front = (queue->front + 1) % SIZE;
queue->count--;
pthread_cond_signal(&queue->full);
pthread_mutex_unlock(&queue->mutex);
return item;
}
// 生产者线程函数
void* producer(void* arg) {
DoubleBufferQueue* queue = (DoubleBufferQueue*)arg;
int i;
for (i = 0; i < 20; i++) {
produce(queue, i);
printf("Produced: %d\n", i);
}
pthread_exit(NULL);
}
// 消费者线程函数
void* consumer(void* arg) {
DoubleBufferQueue* queue = (DoubleBufferQueue*)arg;
int i, item;
for (i = 0; i < 20; i++) {
item = consume(queue);
printf("Consumed: %d\n", item);
}
pthread_exit(NULL);
}
int main() {
pthread_t producerThread, consumerThread;
DoubleBufferQueue queue;
init(&queue);
pthread_create(&producerThread, NULL, producer, &queue);
pthread_create(&consumerThread, NULL, consumer, &queue);
pthread_join(producerThread, NULL);
pthread_join(consumerThread, NULL);
return 0;
}
```
在这个示例中,双缓存队列用于在生产者线程和消费者线程之间传递数字。生产者线程通过调用`produce`函数将数字添加到生产者队列中,消费者线程通过调用`consume`函数从消费者队列中读取数字。通过使用互斥锁和条件变量,实现了生产者和消费者的同步和互斥访问双缓存队列。
### 回答3:
C语言的双缓存队列可以通过定义一个结构体来实现。下面是一个简单的双缓存队列的实现:
```c
#include <stdio.h>
#include <stdlib.h>
#define MAX_SIZE 100
typedef struct {
int data[MAX_SIZE];
int front; // 指向队列首元素的索引
int rear; // 指向队列最后一个元素的下一个位置的索引
} DoubleBufferQueue;
void initQueue(DoubleBufferQueue *queue) {
queue->front = 0; // 初始队列首元素的索引为0
queue->rear = 0; // 初始队列最后一个元素的下一个位置的索引为0
}
int isEmpty(DoubleBufferQueue *queue) {
return queue->front == queue->rear;
}
int isFull(DoubleBufferQueue *queue) {
return (queue->rear + 1) % MAX_SIZE == queue->front;
}
void enqueue(DoubleBufferQueue *queue, int item) {
if (isFull(queue)) {
printf("队列已满,无法入队\n");
return;
}
queue->data[queue->rear] = item;
queue->rear = (queue->rear + 1) % MAX_SIZE;
}
int dequeue(DoubleBufferQueue *queue) {
if (isEmpty(queue)) {
printf("队列为空,无法出队\n");
return -1; // 返回一个特殊值表示错误
}
int item = queue->data[queue->front];
queue->front = (queue->front + 1) % MAX_SIZE;
return item;
}
int main() {
DoubleBufferQueue queue;
initQueue(&queue);
enqueue(&queue, 1);
enqueue(&queue, 2);
enqueue(&queue, 3);
while (!isEmpty(&queue)) {
printf("%d ", dequeue(&queue));
}
printf("\n");
return 0;
}
```
上述代码在初始化队列时,将队列的首元素和最后一个元素的下一个位置的索引都设置为0。然后,使用`enqueue`函数将元素添加到队列尾部,使用`dequeue`函数从队列头部取出元素。队列满时,无法继续进行入队操作;队列空时,无法继续进行出队操作。