day05 1.多线程基本概念 2.线程支持函数（多线程编程）

 1、使用两个线程完成两个文件的拷贝，分支线程1拷贝前一半，分支线程2拷贝后一半，主线程回收两个分支线程的资源

#include <myhead.h>int copy_file(const char *srcfile,const char *destfile,int start,int len);struct Buff
{const char *srcfile;const char *destfile;int len;int flag;
};void *task(void *arg)
{struct Buff *buff = (struct Buff *)arg;if(buff->flag == 1){copy_file(buff->srcfile,buff->destfile,0,buff->len/2);}else if (buff->flag == 2){copy_file(buff->srcfile,buff->destfile,buff->len/2,buff->len-buff->len/2);}
}int get_file_len(const char *srcfile,const char *destfile)
{//以只读打开源文件int sfd = open(srcfile,O_RDONLY);if(sfd == -1){perror("open srcfile error");return -1;}//以创建的形式打开目标文件	int dfd = open(destfile,O_WRONLY|O_CREAT|O_TRUNC,0664);if(dfd == -1){perror("open destfile error");return -1;}int size = lseek(sfd,0,SEEK_END);//关闭文件close(sfd);close(dfd);return size;
}int copy_file(const char *srcfile,const char *destfile,int start,int len)
{//以只读的形式打开源文件int sfd = open(srcfile,O_RDONLY);if(sfd == -1){perror("open srcfile error");return -1;}int dfd = open(destfile,O_WRONLY);if(dfd == -1){perror("open destfile error");return -1;}lseek(sfd,start,SEEK_SET);lseek(dfd,start,SEEK_SET);char buf[128]="";int sum =0;while(1){//从源文件中读取数据int res = read(sfd,buf,sizeof(buf));sum += res;if(res==0||sum>len){write(dfd,buf,res-(sum-len));break;}write(dfd,buf,res);}close(sfd);close(dfd);printf("拷贝成功\n");
}int main(int argc, const char *argv[])
{if(argc != 3)     //判断是否传入两个文件{printf("input file error\n");return -1;}const char *srcfile = argv[1];const char *destfile = argv[2];int len = get_file_len(srcfile,destfile);   //求出源文件的长度struct Buff buff1={srcfile,destfile,len,1};struct Buff buff2={srcfile,destfile,len,2};//定义两个线程变量pthread_t tid1,tid2;//创建两个线程if((pthread_create(&tid1,NULL,task,&buff1)) != 0){printf("tid1 创建失败\n");return -1;}if((pthread_create(&tid2,NULL,task,&buff2)) != 0){printf("tid2 创建失败\n");return -1;}//阻塞等两个线程的回收pthread_join(tid1,NULL);pthread_join(tid2,NULL);return 0;	
}