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<td width="68%" background="DDl_back2.jpg" height="44"><big><big><font face="黑体"><p align="center"> ● UNIX网络编程 (BM: clown) </font></big></big></td></tr>
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<tr><td width="100%" colspan="2" height="100" align="center" valign="top"><br><p align="center">[<a href="index.htm">回到开始</a>][<a href="54.htm">上一层</a>][<a href="104.htm">下一篇</a>]
<hr><p align="left"><small>发信人: clown (梧桐叶), 信区: UNP <br>
标 题: 信号量的例子--轮船过桥 <br>
发信站: UNIX编程 (2001年10月20日22:10:08 星期六), 站内信件 <br>
<br>
<br>
<br>
---------------- （信号灯sem_out） <br>
| | <br>
--------------------------------- <br>
| | <br>
| | <br>
河流 | | 《--轮船（从右向左行进） <br>
| 桥1 |桥2 <br>
| | <br>
---------------------------------- <br>
| | <br>
| 沼泽 | <br>
------- -----------------马路（单行道，从左向右） <br>
（信号灯sem_in） <br>
<br>
轮船和汽车的到达都是随机的。轮船过桥时要将桥升起来. <br>
<br>
有可能轮船的长度大于沼泽地的长度, 这里没有考虑这种情况, 也没有考虑汽车 <br>
在桥上通过所需要的时间. <br>
<br>
这里为了方便，汽车到达信号灯sem_in处阻塞以后，没有保存阻塞的 <br>
汽车数目。 <br>
<br>
//gcc file.c -lpthread <br>
<br>
#include <pthread.h> <br>
#include <semaphore.h> <br>
#include <errno.h> <br>
#include <unistd.h> <br>
<br>
sem_t sem_in; <br>
sem_t sem_out; <br>
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER; <br>
int array[10]; //沼泽地的长度可以存放10辆汽车 <br>
struct timespec tm; <br>
<br>
void car_input(void); <br>
void car_output(void); <br>
void car_moving(void); <br>
<br>
<br>
int main() <br>
{ <br>
pthread_t tid_in, tid_out, tid_mov; <br>
int ship = 1; <br>
<br>
tm.tv_sec = 0; <br>
tm.tv_nsec = 100*1000*1000; //100 milliseconds <br>
errno = 0; <br>
<br>
sem_init(&sem_in, 0, 1); <br>
sem_init(&sem_out, 0, 1); <br>
if(pthread_create(&tid_in, NULL, (void *)&car_input, NULL) != 0) { <br>
perror("create thread"); <br>
exit(1); <br>
} <br>
if(pthread_create(&tid_in, NULL, (void *)&car_output, NULL) != 0) { <br>
perror("create thread"); <br>
exit(1); <br>
} <br>
if(pthread_create(&tid_mov, NULL, (void *)&car_moving, NULL) != 0) { <br>
perror("create thread"); <br>
exit(1); <br>
} <br>
<br>
while(ship <= 5) { <br>
srand(time(NULL)); <br>
sleep(5 + rand() % 5); //sleep 5--10 seconds <br>
printf("ship %d arrived!\n", ship); <br>
sem_wait(&sem_out); <br>
printf("ship %d is passing the second bridge\n", ship); <br>
//suppose the ship need 3 seconds to pass the bridge <br>
sleep(3); <br>
sem_post(&sem_out); <br>
printf("ship %d passed the second bridge\n", ship); <br>
//suppose the ship need 3 seconds to arrive the other bridge <br>
sleep(3); <br>
sem_wait(&sem_in); <br>
printf("ship %d is passing the first bridge\n", ship); <br>
sleep(3); <br>
sem_post(&sem_in); <br>
printf("ship %d passed the first bridge, ok!\n", ship); <br>
ship ++; <br>
} <br>
<br>
<br>
//wait cars to pass <br>
sleep(3); <br>
return 0; <br>
} <br>
<br>
void car_input(void) <br>
{ <br>
static int car_in = 1; <br>
struct timespec random; <br>
while(1) { <br>
//the car's arrive is random <br>
srand(time(NULL)); <br>
random.tv_sec = 0; <br>
random.tv_nsec = (rand() % 200 + 100) * 1000 * 1000; <br>
nanosleep(&random, NULL); //100--299 milliseconds <br>
sem_wait(&sem_in); <br>
pthread_mutex_lock(&lock); <br>
if(array[9] == 0) { <br>
array[9] = 1; <br>
printf("car %d passed the first bridge\n", car_in++); <br>
} else <br>
printf("the car is blocked in the first bridge\n"); <br>
pthread_mutex_unlock(&lock); <br>
sem_post(&sem_in); <br>
nanosleep(&tm, NULL); <br>
} <br>
return; <br>
} <br>
<br>
void car_output(void) <br>
{ <br>
static int car_out = 1; <br>
while(1) { <br>
//the car is moving forward, :) <br>
if(array[0] == 0) { <br>
//no car need to pass the second bridge <br>
nanosleep(&tm, NULL); <br>
continue; <br>
} <br>
sem_wait(&sem_out); <br>
pthread_mutex_lock(&lock); <br>
printf("car %d passed the second bridge\n", car_out++); <br>
array[0] = 0; <br>
pthread_mutex_unlock(&lock); <br>
sem_post(&sem_out); <br>
nanosleep(&tm, NULL); <br>
} <br>
return; <br>
} <br>
<br>
void car_moving(void) <br>
{ <br>
int i; <br>
while(1) { <br>
pthread_mutex_lock(&lock); <br>
for(i = 0; i < 9; i++) { <br>
if(array[i] == 0) <br>
break; <br>
} <br>
if(i == 9) { <br>
printf("the road is blocked!\n"); <br>
pthread_mutex_unlock(&lock); <br>
nanosleep(&tm, NULL); <br>
continue; <br>
} <br>
for(; i < 9; i++) { <br>
array[i] = array[i+1]; <br>
if(array[i+1] == 1) <br>
printf("car is moving: %d-->%d \n", i+1, i); <br>
} <br>
array[9] = 0; <br>
pthread_mutex_unlock(&lock); <br>
nanosleep(&tm, NULL); <br>
} <br>
return; <br>
} <br>
<br>
<br>
<br>
-- <br>
易朽的是生命，似那转瞬即谢的花朵；然而永存的，是对未来的渴望， <br>
是那生生世世传递下来的，不朽的，生的激情。每一朵勇敢开放的花， <br>
都是一个死亡唇边的微笑。 <br>
※ 修改:·clown 於 10月21日09:18:11 修改本文·[FROM: 202.114.1.61] <br>
※ 来源:·UNIX编程 apue.dhs.org·[FROM: 202.114.1.61] <br>
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