rdwt.c

操作系统实验,文件系统,c语言实现的

#include <stdio.h>
#include "filesys.h"

unsigned int read(int fd1,char *buf,unsigned int size)
{
    unsigned long off;
    int block,block_off,i,j;
    struct inode *inode;
    char *temp_buf;
	inode=sys_ofile[user[user_id].u_ofile[fd1]].f_inode;
	printf("\nf_inode=%d\n",sys_ofile[user[user_id].u_ofile[fd1]].f_inode);
	if(! (sys_ofile[user[user_id].u_ofile[fd1]].f_flag&FREAD))
	{
		printf("\nthe file is not opened for read\n");
		return 0;
	}
	temp_buf=buf;
	off=sys_ofile[user[user_id].u_ofile[fd1]].f_off;
	if((off+size)>inode->di_size) size=inode->di_size-off;
	block_off=off%BLOCKSIZ;
	block=off/BLOCKSIZ;
	if(block-off+size<BLOCKSIZ)
	{
		fseek(fd,DATASTART+inode->di_addr[block]*BLOCKSIZ+block_off,SEEK_SET);
		fread(buf,1,size,fd);
		return size;
    }
	fseek(fd,DATASTART+inode->di_addr[block]*BLOCKSIZ+block_off,SEEK_SET);
	fread(temp_buf,1,BLOCKSIZ-block_off,fd);
	temp_buf+=BLOCKSIZ-block_off;
	j=(inode->di_size-off-block_off)/BLOCKSIZ;
	for(i=0;i<(size-block_off)/BLOCKSIZ;i++)
	{
		fseek(fd,DATASTART+inode->di_addr[j+i]*BLOCKSIZ,SEEK_SET);
		fread(temp_buf,1,BLOCKSIZ,fd);
		temp_buf+=BLOCKSIZ;
	}
	block_off=(size-block_off)%BLOCKSIZ;
	block=inode->di_addr[off+size/BLOCKSIZ+1];
	fseek(fd,DATASTART+block*BLOCKSIZ,SEEK_SET);
	fread(temp_buf,1,block_off,fd);
	sys_ofile[user[user_id].u_ofile[fd1]].f_off+=size;
	return size;
}

unsigned int write(unsigned short fd1,char *buf,unsigned int size)    /*write*/
{
	unsigned long off;
	int block,block_off,i,j, k=0;
	struct inode *inode;
	char *temp_buf;
	printf("f_off=%d\n",sys_ofile[user[user_id].u_ofile[fd1]].f_off); 
	inode=sys_ofile[user[user_id].u_ofile[fd1]].f_inode;
	printf("di_size=%d,i_ino=%d\n",inode->di_size,inode->i_ino); 
	/*if(! (sys_ofile[user[user_id].u_ofile[fd1]].f_flag & FWRITE))
	{
	printf("\nthe file is not opened for wrie\n");
	return 0;
	}
	*/
	temp_buf=buf;
	off=sys_ofile[user[user_id].u_ofile[fd1]].f_off;
	block_off=off%BLOCKSIZ;
	block=off/BLOCKSIZ;
	if(block_off+size<BLOCKSIZ)
	{
		fseek(fd,DATASTART+inode->di_addr[block]* BLOCKSIZ+block_off,SEEK_SET);
		fwrite(buf,1,size,fd);
		return size;
	}
	if(sys_ofile[user[user_id].u_ofile[fd1]].f_flag == FAPPEND) 
	{ 
		fseek(fd,DATASTART+inode->di_addr[block]*BLOCKSIZ+block_off,SEEK_SET); 
		fwrite(temp_buf,1,BLOCKSIZ-block_off,fd); 
		temp_buf+=BLOCKSIZ-block_off; 
		k=1; 
	} 
	printf("size=%d,block_off=%d\n",size,block_off); 
	for(i=0;i<(size-k*(BLOCKSIZ-block_off))/BLOCKSIZ;i++)
	{
		inode->di_addr[block+i]=balloc();
		fseek(fd,DATASTART+inode->di_addr[block+k+i]*BLOCKSIZ,SEEK_SET);
		fwrite(temp_buf,1,BLOCKSIZ,fd);
		temp_buf+=BLOCKSIZ;
	}
	block_off=(size-k*(BLOCKSIZ-block_off))%BLOCKSIZ;
	block=inode->di_addr[block+k+i]=balloc();
	fseek(fd,DATASTART+block*BLOCKSIZ,SEEK_SET);
	fwrite(temp_buf,1,block_off,fd);
	sys_ofile[user[user_id].u_ofile[fd1]].f_off+=size;
	inode->di_size=sys_ofile[user[user_id].u_ofile[fd1]].f_off; 
	return size;
}