C语言写一个双线程的文件复制程序

在C语言中编写一个多线程文件复制程序涉及到`pthread.h`库，这是一个处理线程的头文件。下面是一个简单的示例，它创建两个线程分别负责读取源文件和写入目标文件：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <pthread.h>

#define BUFFER_SIZE 4096
#define SRC_FILE "source.txt"
#define DST_FILE "destination.txt"

void* read_thread(void *arg) {
    FILE *src = fopen(SRC_FILE, "rb");
    char buffer[BUFFER_SIZE];
    int bytes;

    while ((bytes = fread(buffer, sizeof(char), BUFFER_SIZE, src)) > 0) {
        pthread_mutex_lock(&mutex);
        fwrite(buffer, bytes, 1, dst);
        pthread_mutex_unlock(&mutex);
    }
    fclose(src);

    return NULL;
}

void* write_thread(void *arg) {
    FILE *dst = fopen(DST_FILE, "wb");
    pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

    // 初始化和解锁是多余的，这里是示例，实际上不需要这样做
    pthread_mutex_init(&mutex, NULL);
    pthread_mutex_lock(&mutex); // 确保先获取锁

    read_thread(NULL); // 调用另一个线程

    pthread_mutex_destroy(&mutex);
    fclose(dst);

    return NULL;
}

int main() {
    pthread_t reader_thread, writer_thread;

    if (pthread_create(&reader_thread, NULL, read_thread, NULL) != 0) {
        perror("Error creating reader thread");
        exit(1);
    }

    if (pthread_create(&writer_thread, NULL, write_thread, NULL) != 0) {
        perror("Error creating writer thread");
        exit(1);
    }

    pthread_join(reader_thread, NULL);
    pthread_join(writer_thread, NULL);

    printf("File copy completed.\n");

    return 0;
}