#include <pthread.h>
#define BUFFER_SIZE 16 // 緩衝區數量
struct prodcons
{
// 緩衝區相關數據結構
int buffer[BUFFER_SIZE]; /* 實際數據存放的數組*/
pthread_mutex_t lock; /* 互斥體lock 用於對緩衝區的互斥操作 */
int readpos, writepos; /* 讀寫指針*/
pthread_cond_t notempty; /* 緩衝區非空的條件變量 */
pthread_cond_t notfull; /* 緩衝區未滿的條件變量 */
};
/* 初始化緩衝區結構 */
void init(struct prodcons *b)
{
pthread_mutex_init(&b->lock, NULL);
pthread_cond_init(&b->notempty, NULL);
pthread_cond_init(&b->notfull, NULL);
b->readpos = 0;
b->writepos = 0;
}
/* 將產品放入緩衝區,這裏是存入一個整數*/
void put(struct prodcons *b, int data)
{
pthread_mutex_lock(&b->lock);
/* 等待緩衝區未滿*/
if ((b->writepos + 1) % BUFFER_SIZE == b->readpos)
{
pthread_cond_wait(&b->notfull, &b->lock);
}
/* 寫數據,並移動指針 */
b->buffer[b->writepos] = data;
b->writepos++;
if (b->writepos >= BUFFER_SIZE)
b->writepos = 0;
/* 設置緩衝區非空的條件變量*/
pthread_cond_signal(&b->notempty);
pthread_mutex_unlock(&b->lock);
}
/* 從緩衝區中取出整數*/
int get(struct prodcons *b)
{
int data;
pthread_mutex_lock(&b->lock);
/* 等待緩衝區非空*/
if (b->writepos == b->readpos)
{
pthread_cond_wait(&b->notempty, &b->lock);
}
/* 讀數據,移動讀指針*/
data = b->buffer[b->readpos];
b->readpos++;
if (b->readpos >= BUFFER_SIZE)
b->readpos = 0;
/* 設置緩衝區未滿的條件變量*/
pthread_cond_signal(&b->notfull);
pthread_mutex_unlock(&b->lock);
return data;
}
/* 測試:生產者線程將1 到10000 的整數送入緩衝區,消費者線
程從緩衝區中獲取整數,兩者都打印信息*/
#define OVER ( - 1)
struct prodcons buffer;
void *producer(void *data)
{
int n;
for (n = 0; n < 50; n++)
{
printf("%d ---producer==>\n", n);
put(&buffer, n);
} put(&buffer, OVER);
return NULL;
}
void *consumer(void *data)
{
int d;
while (1)
{
d = get(&buffer);
if (d == OVER)
break;
printf("---consumer==>%d \n", d);
}
return NULL;
}
int main(void)
{
pthread_t th_a, th_b;
void *retval;
init(&buffer);
/* 創建生產者和消費者線程*/
pthread_create(&th_a, NULL, producer, 0);
pthread_create(&th_b, NULL, consumer, 0);
/* 等待兩個線程結束*/
pthread_join(th_a, &retval);
pthread_join(th_b, &retval);
return 0;
}