creat.c

操作系统实验,文件系统,c语言实现的

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

creat(unsigned int user_id,char *filename,unsigned short mode)
{
	unsigned int di_ith,di_ino;
	struct inode *inode;
	int i,j;
	di_ino=namei(filename);
	if(di_ino!=NULL)    /*  already existed  */
	{
		inode=iget(di_ino);
		if(access(user_id,inode,mode)==0)
		{
			iput(inode);
			printf("\ncreat access not allowed\n");
			return;
		}
		/*  free all the bloCk ofthe 01d file  */
		for(i=0;i<inode->di_size/BLOCKSIZ+1;i++)
		{
			bfree(inode->di_addr[i]);
		}
		/* to do:add code here to update the pointer of the sys_file  */
		for(i=0;i<SYSOPENFILE;i++)
			if(sys_ofile[i].f_inode==inode)
			{
				sys_ofile[i].f_off=0;
			}
			for(i=0;i<NOFILE;i++)
				if(user[user_id].u_ofile[i]==SYSOPENFILE+1)
				{
					user[user_id].u_uid=inode->di_uid;
					user[user_id].u_gid=inode->di_gid;
					for(j=0;j<SYSOPENFILE;j++)
						if(sys_ofile[j].f_count==0)
						{
							user[user_id].u_ofile[i]=j;
							sys_ofile[j].f_flag=mode;
						}
						return i;
				}
	}
	else  /* not existed before */
	{
		inode=ialloc();
		di_ith=iname(filename);
		dir.size++;
		dir.direct[di_ith].d_ino=inode->i_ino;
		dir.direct[di_ith+1].d_ino=0;
		
		inode->di_mode=user[user_id].u_default_mode|DIFILE;
		inode->di_uid=user[user_id].u_uid;
		inode->di_gid=user[user_id].u_gid;
		inode->di_size=file_block;
		inode->di_number=1;
		
		
		for(i=0;i<SYSOPENFILE;i++)
			if(sys_ofile[i].f_count==0)
				break;
			for(j=0;j<NOFILE;i++)
				if(user[user_id].u_ofile[j]==SYSOPENFILE+1)
					break;
				user[user_id].u_ofile[j]=i;
				sys_ofile[i].f_flag=mode;
				sys_ofile[i].f_count=0;
				sys_ofile[i].f_off=0;
				sys_ofile[i].f_inode=inode;
				
				return  j;
	}
}