igetput.c

操作系统实验,文件系统,c语言实现的

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

struct inode * iget(unsigned int dinodeid)    /*  iget()  */
{
	int existed=0,inodeid;
	long addr;
	struct inode *temp, *newinode;
	inodeid=dinodeid % NHINO;
	if(hinode[inodeid].i_forw==NULL)  //hinode为查找内存i节点的hash表
		existed=0;
	else
	{
		temp=hinode[inodeid].i_forw;
		while(temp)
		{
			if(temp->i_ino==inodeid)//existed ,i_ino是磁盘i节点标号
			{   
				existed=1;
				temp->i_count++;
				return temp;
			}
			else    /*not existed*/
				temp=temp->i_forw;
			
		};
    }
	
    //  not existed 因为前面有个return没有返回
	addr=DINODESTART+dinodeid*DINODESIZ;   //1.  calculate the addr of the dinode in the file sys column 
	newinode=(struct inode *)malloc (sizeof(struct inode));//2.  malloc the new inode
	fseek(fd,addr,SEEK_SET);               //3.  read the dinode to the inode 
	fread(&(newinode->di_number),DINODESIZ,1,fd);
	newinode->i_forw=hinode[inodeid].i_forw;//4.  put it into hinode [inodeid]queue
	newinode->i_back=newinode;
	if(newinode->i_forw!=NULL)
		newinode->i_forw->i_back=newinode;
	hinode[inodeid].i_forw=newinode;
	newinode->i_count=1;                  //5.  initialize the inode ,i_count引用计数
	newinode->i_flag=0;                   //f1ag for not update
	newinode->i_ino=dinodeid;
	newinode->di_size=3*(DIRSIZ+2);
	if(dinodeid == 3)
		newinode->di_size=BLOCKSIZ;
	
	return newinode;	
}


iput(struct inode *pinode)    /*iput()*/
{
	long addr;
	unsigned int block_num;
	int i;
	if(pinode->i_count>1)
	{
		pinode->i_count--;//引用计数减1后返回
        return;
	}
	else
	{
        if(pinode->di_number!=0)
        {
			/*  write back the inode  */
			addr=DINODESTART+pinode->i_ino*DINODESIZ;
			fseek(fd,addr,SEEK_SET);
			fwrite(&pinode->di_number,DINODESIZ,1,fd);
        }
        else  //关联文件数为0。删除该文件
        {
			/*  rm the inode & the block of the file in the disk  */
			block_num=pinode->di_size/BLOCKSIZ;
			for(i=0;i<block_num;i++)
			{
				bfree(pinode->di_addr[i]);
			}
			ifree(pinode->i_ino);			
		};
		/*  free the inode in the memory  */
		if(pinode->i_forw==NULL)
			pinode->i_back->i_forw=NULL;
        else
        {
			pinode->i_forw->i_back=pinode->i_back;
			pinode->i_back->i_forw=pinode->i_forw;
        };
		ifree(pinode);
    };
}