多线程拷贝文件

                                                              PS：多进程拷贝文件--->（多进程拷贝文件-CSDN博客）

要求如下

        创建两个线程thread1和thread2拷贝同一个文件，thread1拷贝前一半，thread2拷贝后一半。

demo.c      (编译 gcc demo.c -lpthread）

#include 
typedef struct _ARG
{
    const char *srcfile;
    const char *destfile;
    int start;
    int len;
} arg_t;
int get_file_len(const char *srcfile)
{
    int srcfd;
    if (-1 == (srcfd = open(srcfile, O_RDONLY)))
    {
        perror("open error");
        exit(-1);
    }
    int len = lseek(srcfd, 0, SEEK_END);
    close(srcfd);
    return len;
}
int copy_file(const char *src, const char *dest, int start, int len)
{
    char buff[16] = {0};
    int ret, count;
    int srcfd, destfd;
    if (-1 == (srcfd = open(src, O_RDONLY)))
    {
        perror("open src error");
        exit(-1);
    }
    if (-1 == (destfd = open(dest, O_WRONLY)))
    {
        perror("open dest error");
        exit(-1);
    }
    lseek(srcfd, start, SEEK_SET);
    lseek(destfd, start, SEEK_SET);
    while (1)
    {
        if (-1 == (ret = read(srcfd, buff, sizeof(buff))))
        {
            perror("read error");
            exit(-1);
        };
        if (len < sizeof(buff))
        {
            write(destfd, buff, len);
            break;
        }
        else
        {
            write(destfd, buff, ret);
        }
        len -= ret;
    }
    close(srcfd);
    close(destfd);
    return 0;
}
int init_file(const char *destfile)
{
    int fd;
    if (-1 == (fd = open(destfile, O_WRONLY | O_CREAT | O_TRUNC, 0666)))
    {
        perror("open error");
        exit(-1);
    }
 
    close(fd);
    return 0;
}
 
void *thread1(void *args)
{
    // 子线程1拷贝前一半
    arg_t args1;
    args1 = *(arg_t *)args;
    copy_file(args1.srcfile, args1.destfile, args1.start, args1.len);
    printf("子线程1拷贝前一半完成...\n");
}
void *thread2(void *args)
{
    // 子线程2拷贝后一半
    arg_t args2;
    args2 = *(arg_t *)args;
    copy_file(args2.srcfile, args2.destfile, args2.start, args2.len);
    printf("子线程2拷贝后一半完成...\n");
}
 
int main(int argc, const char *argv[])
{
    // 入参合理性检查
    if (argc != 3)
    {
        printf("usage error:%s srcfile destfile\n", argv[0]);
        exit(-1);
    }
    // 创建两个线程
    pthread_t pid1, pid2;
    int fd;
    int len;
    init_file(argv[2]);
    len = get_file_len(argv[1]);
    arg_t argg[] = {
        [0] = {argv[1], argv[2], 0, len / 2},
        [1] = {argv[1], argv[2], len / 2, (len-(len/2))}};
    if (errno = (pthread_create(&pid1, NULL, thread1, (void *)&argg[0])) != 0)
    {
        perror("pthread_create error");
        exit(-1);
    }
    if (errno = (pthread_create(&pid2, NULL, thread2, (void *)&argg[1])) != 0)
    {
        perror("pthread_create error");
        exit(-1);
    }
    // 主线程
    pthread_join(pid1, NULL);
    pthread_join(pid2, NULL);
    return 0;
}