iallfre.c

基于UNIX6的文件系统模拟程序

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


static struct dinode block_buf[BLOCKSIZ/DINODESIZ];

struct inode *ialloc()
{
	struct inode *temp_inode;
	unsigned int cur_di;
	int i,count,block_end_flag;

	if(filsys.s_pinode == NICINOD) /* s_inode empty */
	{
		i = 0 ;
		count = 0;
		block_end_flag = 1;
		cur_di = filsys.s_rinode;	
		while((count<NICINOD)||(count <= filsys.s_ninode))
		{
			if(block_end_flag)
			{
				fseek(fd,DINODESTART + cur_di*DINODESIZ,SEEK_SET);
				fread(block_buf,1,BLOCKSIZ,fd);
				block_end_flag = 0;
				i = 0;
			}
			while(block_buf[i].di_mode == DIEMPTY)
			{
				cur_di++;
				i++;
			}
			if(i == NICINOD)
				block_end_flag = 1;
			else
			{
				filsys.s_inode[filsys.s_pinode--] = cur_di;
				count ++;
			}
		}
		filsys.s_rinode = cur_di;
	}
	temp_inode = iget(filsys.s_inode[filsys.s_pinode]);
	fseek(fd,DINODESTART+filsys.s_inode[filsys.s_pinode]*DINODESIZ,SEEK_SET);
	fwrite(&temp_inode->di_number,1,sizeof(struct dinode),fd);
	filsys.s_pinode++;
	filsys.s_ninode--;
	filsys.s_fmod = SUPDATE;
	return temp_inode;
}



ifree(dinodeid)
unsigned dinodeid;
{
	filsys.s_ninode++;
	if(filsys.s_pinode != NICINOD) /* not full */
	{
		filsys.s_inode[filsys.s_pinode] = dinodeid;
		filsys.s_pinode++;
	}
	else /* full */
	{
		if(dinodeid < filsys.s_rinode)
		{
			filsys.s_inode[NICINOD] = dinodeid;
			filsys.s_rinode = dinodeid;
		}
	}
}