linux下实现多线程拷贝命令

实现多线程拷贝命令,如：./multithread_copy  srcfile destfile N（拷贝线程个数）

难点：

内存映射mmap。

给每一个线程合理的分配任务。

多线程的实现。

具体的实现代码如下：

/*************************************************************************
  > File Name: multithread_copy.c
  > Author: lucifer
  > Mail: [email protected] 
  > Created Time: 2014年11月14日 星期五 17时43分36秒
 ************************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <pthread.h>
#include <sys/mman.h>
#include <string.h>
#include <unistd.h>
#define N 5
int nthread = 0;

struct allocate_task
{
	char *start;
	char *end;
	int size;
	int num;
};
void sys_err(const char *str)
{
	perror(str);
	exit(-1);
}

void *thread_copy(void *arg)
{
	int i;
	struct allocate_task *s = (struct allocate_task *)arg;
	for(i = 0;i < nthread;i++)
	{		
		memcpy(s[i].end,s[i].start,s[i].size);	
	}	
}

int main(int argc, char *argv[])
{
	int fdsrc, fddest, i, err, total_size,task_size;
	struct stat sbuf;
	char *psrc,*pdest;


	if(argc < 3)
	{
		fprintf(stdout,"%s srcname destname\n",argv[0]);		
		exit(-1);
	}
	if(argc = 3)	
		nthread = N;	
	else
		nthread = atoi(argv[3]);
	if(stat(argv[1],&sbuf) < 0)
		sys_err("stat");
	total_size = sbuf.st_size;
	fddest = open(argv[2],O_CREAT |O_RDWR | O_TRUNC,0664);
	if(fddest < 0)
		sys_err("open");
	if(lseek(fddest,total_size - 1,SEEK_SET) < 0)
		sys_err("lseek");
	write(fddest,"\0",1);
	fdsrc = open(argv[1],O_RDONLY);
	if(fdsrc < 0)
		sys_err("open");
	psrc = mmap(NULL,total_size,PROT_READ,MAP_PRIVATE,fdsrc,0);
	if(psrc == MAP_FAILED)
		sys_err("mmap");
	pdest = mmap(NULL,total_size,PROT_WRITE,MAP_SHARED,fddest,0);
	if(pdest == MAP_FAILED)
		sys_err("mmap");
	close(fdsrc);
	close(fddest);
	struct allocate_task *work = malloc(nthread * sizeof(struct allocate_task));
	task_size = total_size / nthread;
	for(i = 0;i < nthread - 1;i++)
	{
		work[i].start = psrc + i * task_size;
		work[i].end = pdest + i * task_size;
		work[i].size = task_size;
	}
	work[i].start = psrc + i * task_size;
	work[i].end = pdest + i * task_size;
	work[i].size = total_size - task_size * (nthread - 1);
	work[i].num = i;


	pthread_t tid[nthread];

	for(i = 0;i < nthread;i++)
	{
		err = pthread_create(&tid[i],NULL,thread_copy,(void *)work);
		if(err != 0)
		{
			printf("%s\n",strerror(err));
			break;
		}

	}



	for(i = 0;i < nthread; i++)
	{
		pthread_join(tid[i],NULL);
	}

	free(work);
	return 0;	
}