igetput.c

操作系统课程设计

/*获取释放i节点内容程序iget()/iput()*/

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

struct inode * iget (dinodeid)    /* iget( ) */
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==dinodeid)
			/*existed */
			{
				existed = 1;
				temp->i_count ++;
				return temp;
			}else    /*not existed */
				temp =temp->i_forw;
			};
	  }
	/*	1. calculate the addr of the dinode in the file sys column */
	addr = DINODESTART + dinodeid * DINODESIZ;
	/*	2. malloc the new mode */
	newinode = (struct inode * ) malloc (sizeof (struct inode));
	/*	3.read the dinode to the mode */
	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=newinode;

	/*newinode->i_forw->i_back=newinode;*/

	if (newinode->i_forw)                    //~~~~edited
		newinode->i_forw->i_back=newinode;

	hinode[inodeid].i_forw=newinode;
	
	/* 5.initialize the mode */
	newinode->i_count=1;
	newinode->i_flag=0;    /* flag for not update */
	newinode->i_ino=dinodeid;
	return newinode;
}

void iput(pinode) /* iput ( ) */
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 mode */
			addr =DINODESTART + pinode->i_ino * DINODESIZ;
			fseek(fd, addr, SEEK_SET);
			fwrite (&pinode->di_number, DINODESIZ, 1 ,fd);
		}
		else
		{
			/*	rm the mode & the block of the file in the disk */
			if(pinode->di_size!=0)
			{
				block_num=pinode->di_size/BLOCKSIZ;
				for (i=0;i<block_num; i++)
				{
					if (pinode->di_addr[i]!=0)
						bfree(pinode->di_addr[i]);          
				}
			}
			ifree(pinode->i_ino);
		};

		/*	free the mode 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;
		};

		if (pinode->i_back==pinode)            //~~~edited
				hinode[pinode->i_ino%NHINO].i_forw=pinode->i_forw;

		free (pinode);
	};
}