IO process thread -> thread -> day5

目录

练习

一、Invert the thread

1.1 函数

1.2 执行结果

 二、Thread code to copy pictures

2.1 函数

2.2 执行结果

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练习

1. 定义一个全局变量,char str[] = "123456",Two threads are required to be defined：线程A, 线程B
        1）. 要求AThe thread loop prints the global stringstr;
        2）. 要求BThe thread loop inverts the global stringstr：将strThe contents of are inverted as "654321",Inverted to"123456"....
           注意：It is printed upside down, not upside down
        3）. 要求A线程打印出的str字符串内容为;123456或者654321.Out of order is not allowed,例如：623451 653451,,,、

2. Requires two threads to copy an image,AThe thread copies the first half,BThe thread copies the second half,不允许使用sleep函数,不允许使用flag.

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一、Invert the thread

定义一个全局变量,char str[] = "123456",Two threads are required to be defined：线程A, 线程B

        1. 要求AThe thread loop prints the global stringstr;

        2. 要求BThe thread loop inverts the global stringstr：将strThe contents of are inverted as "654321",Inverted to"123456"....

           注意：It is printed upside down, not upside down

        3. 要求A线程打印出的str字符串内容为：123456或者654321

This time, a mutex is used

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1.1 函数

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <string.h>

char str[]="123456";
pthread_mutex_t mutex;

void* callback1(void* arg)
{
	pthread_detach(pthread_self());
	int len=strlen(str);
	char temp;
	while(1)
	{
		pthread_mutex_lock(&mutex);
		for(int i=0;i<len/2;i++)
		{
			temp=str[i];
			str[i]=str[len-i-1];
			str[len-i-1]=temp;
		}
		pthread_mutex_unlock(&mutex); 
	}
	pthread_exit(NULL);
}

void* callback2(void* arg)
{
	pthread_detach(pthread_self());

	while(1)
	{
		pthread_mutex_lock(&mutex);
		printf("str=%s\n",str);
		pthread_mutex_unlock(&mutex); 
	}
}
int main(int argc, const char *argv[])
{
	printf("程序开始\n");
	if(pthread_mutex_init(&mutex,NULL) != 0)
	{
		perror("pthread_mutex_init");
		return -1;
	}
	pthread_t tid1,tid2;
	printf("The mutex was created successfully\n");
	//创建线程
	if(pthread_create(&tid1,NULL,callback1,NULL) != 0)
	{
		perror("pthread_create");
		return -1;
	}
	if(pthread_create(&tid2,NULL,callback2,NULL) != 0)
	{
		perror("pthread_create");
		return -1;
	}
	pthread_join(tid1,NULL);
	pthread_join(tid2,NULL);
	pthread_mutex_destroy(&mutex);

	return 0;
}

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1.2 执行结果

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 二、Thread code to copy pictures

The difficulty lies in the created threadA与B,Not sure which one executes first,会导致,Only half of it will be copied.

I will create it firstA,等A执行完后,再创建B,再执行.

should be put in the codefd_r和fd_w定义成全局变量,This only needs to be executed in the main functionopen（打开文件）一次就好了,But I modified it for a long time to execute the result,不想再改了,Please modify as necessary.

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2.1 函数

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>


pthread_mutex_t mutex; //The variable that stores the mutex
char buf; 		//The variable used for storage when reading the file

void* cpy1(void* arg)
{
	pthread_detach(pthread_self()); //自己分离自己,等线程退出后,Automatically reclaim thread resources
	pthread_mutex_lock(&mutex); 	//上锁

	int fd_r=open("./1.png",O_RDONLY);
	int fd_w=open("./cpy.png",O_RDWR | O_CREAT | O_APPEND,0777);
	if(fd_r<0 || fd_w<0)
	{
		perror("open");
		return NULL;
	}
	off_t len=lseek(fd_r,0,SEEK_END);
	printf("len=%ld\n",len);
	lseek(fd_r,0,SEEK_SET);
	lseek(fd_w,0,SEEK_SET);
	for(int i=0;i<len/2;i++)
	{
		if(read(fd_r,&buf,1) <= 0)
		{
			perror("read");
			return NULL;
		}
		write(fd_w,&buf,1);
	}
	close(fd_r);
	close(fd_w);

	pthread_mutex_unlock(&mutex); 	//解锁
	pthread_exit(NULL);  			//结束线程
}
void* cpy2(void* arg)
{
	pthread_detach(pthread_self());
	pthread_mutex_lock(&mutex);

	int fd_r=open("./1.png",O_RDONLY);
	int fd_w=open("./cpy.png",O_RDWR | O_CREAT | O_APPEND,0777);
	if(fd_r<0 || fd_w<0)
	{
		perror("open");
		return NULL;
	}
	off_t len=lseek(fd_r,0,SEEK_END);
	printf("len=%ld\n",len);
	lseek(fd_r,len/2,SEEK_SET);
	lseek(fd_w,len/2,SEEK_SET);
	for(int i=len/2;i<len;i++)
	{
		if(read(fd_r,&buf,1) <= 0)
		{
			perror("read");
			return NULL;
		}
		write(fd_w,&buf,1);
	}
	close(fd_r);
	close(fd_w);

	pthread_mutex_unlock(&mutex);
	pthread_exit(NULL);
}

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2.2 执行结果