blockmanage.c

操作系统简单的登入程序

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

unsigned int balloc();
int bfree(unsigned int pos);
void updateblockmap(unsigned short order,char flag);
/*
balloc function write the ainode to the filesys.o(ainode's address  is already allocated).
change the super->s_nfree 
*/
unsigned int balloc()
{
	unsigned short number;
	unsigned short i;
	if(super->s_nfree==0)
	{
		printf("\nDisk Full!!!\n");
		return  DISKFULL;
	}
        number=super->s_pfree;

		*(super->s_free+number)='1';

	    updateblockmap(number,super->s_free[number]);

    if(--super->s_nfree!=0)
	{
		for(i=0;i<BLOCKNUM;i++)
		{
			if(*(super->s_free+(i+super->s_pfree)%BLOCKNUM)!='1')
			{
				super->s_pfree=(i+super->s_pfree)%BLOCKNUM;

				updatesys();

				break;	
			}

		}		
	}

	return number;
	
}	

int bfree(pos)
unsigned int pos;
{
	if(super->s_nfree+1>BLOCKNUM)
	{
		printf("\nDisk Error!!!\n");
		return  DISKFULL;	
	}
	super->s_nfree++;

	*(super->s_free+pos)='0';

	super->s_pfree=pos;

	updatesys();

	updateblockmap(pos,'0');

	return DISKSUCCESS;
}

void updateblockmap(unsigned short order,char flag)
{
	fd=fopen("filesystem","r+");

	fseek(fd,(BLOCKSIZE+order),SEEK_SET);
	fwrite(&flag,sizeof(char),1,fd);

	fseek(fd,0,SEEK_SET);
	fwrite(super,sizeof(struct filesys),1,fd);
	
	fclose(fd);
}