igetput.c

基于UNIX6的文件系统模拟程序

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

struct inode *iget(dinodeid)
unsigned int dinodeid;
{
	int existed=0,inodeid;
	long addr;
	struct inode *temp,*newinode;

	inodeid = dinodeid%NHINO;
	if(hinode[inodeid].i_forw == NULL)
		existed=0;
	else
	{
		temp = hinode[inodeid].i_forw;
		while(temp)
		{
			if(temp->i_ino == inodeid)
			/*existed*/
			{

				existed = 1;
				temp->i_count++;
				return temp;
			}
			/*not existed*/
			else
				temp = temp->i_forw;
		};
	}
	/*not existed*/
	/* 1.calculate the addr of the dinode in the file sys column */
	addr = DINODESTART+dinodeid*DINODESIZ;
	/* 2.malloc the new inode */
	newinode = (struct inode *)malloc(sizeof(struct inode));
	/* 3.read the dinode to the inode */
	fseek(fd,addr,SEEK_SET);
	fread(&(newinode->di_number),DINODESIZ,1,fd);
	/* 4.put it into hinode[inodeid] queue */
	newinode->i_forw = hinode[inodeid].i_forw;
	newinode->i_back = &hinode[inodeid];//newinode;
	if(newinode->i_forw != NULL)
		newinode->i_forw->i_back = newinode;
	hinode[inodeid].i_forw = newinode;
	/* 5. initialize the inode */
	newinode->i_count = 1;
	newinode->i_flag = 0; /*flag for not update */
	newinode->i_ino = dinodeid;

	return newinode;
}


iput(pinode)
struct inode *pinode;
{
	long addr;
	unsigned int block_num;
	int i;

	if(pinode->i_count >1)
	{
		pinode->i_count--;
		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);

//			printf("in iput %d",pinode->di_size);
		}
		else
		{
			/*rm the inode &the block of the file in the disk */
			block_num = pinode->di_size/BLOCKSIZ;
			for(i=0;i<block_num;i++)
			{
				balloc(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;
		}
		free(pinode);
	}
}