ballfre.c

基于UNIX6的文件系统模拟程序

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

static unsigned int block_buf[BLOCKSIZ];

unsigned int balloc()
{
	unsigned int free_block,free_block_num;
	int i;

	if(filsys.s_nfree == 0)
	{
		printf("\nDisk Full!!\n");
		return DISKFULL;
	}

	free_block = filsys.s_free[filsys.s_pfree];
	if(filsys.s_pfree == NICFREE -1)
	{
		fseek(fd,DATASTART+free_block*BLOCKSIZ,SEEK_SET);
		fread(block_buf,1,BLOCKSIZ,fd);
		free_block_num = block_buf[NICFREE];
		for(i=0;i<free_block_num;i++)
		{
			filsys.s_free[NICFREE-1-i]=block_buf[i];
		}
		filsys.s_pfree = NICFREE-free_block_num;
	}
	else
		filsys.s_pfree++;

	filsys.s_nfree--;
	filsys.s_fmod = SUPDATE;

	return free_block;
}



bfree(block_num)
unsigned int block_num;
{
	int i;

	if(filsys.s_pfree == 0) /* s_free full */
	{
		block_buf[NICFREE] = NICFREE;
		for(i=0;i<NICFREE;i++)
		{
			block_buf[i]=filsys.s_free[NICFREE-1-i];
		}
		filsys.s_pfree = NICFREE -1;
		fseek(fd,DATASTART+block_num*BLOCKSIZ,SEEK_SET);
		fwrite(block_buf,1,BLOCKSIZ,fd);
	}
	else
		filsys.s_pfree--;
	filsys.s_free[filsys.s_pfree] = block_num;
	filsys.s_nfree++;
	filsys.s_fmod=SUPDATE;
}