/*
 * Copyright (c) 1997 David Brownlee (abs@mono.org). Licence at end of file.
 * Attempt to find ffs filesystems in the event of a lost disklabel.
 *
 * This program itself will not modify any data on a disk, but using
 * disklabel and fsck _can_ cause loss of data - you have been warned!
 *
 * Compile with 'cc -Wall -O -o ffs_find ffs_find.c'.
 *
 * To use, run 'ffs_find /dev/rXXNc' (eg rsd0c, rsd1c, or rwd0c etc), note the
 * possible filesystems, disklabel appropriately and try to fsck.
 * (May want to use /dev/rXXNd on i386).
 *
 * It reports possible filesystems by checking for two 'superblock like'
 * blocks fs.fs_sblkno blocks apart.
 *
 * Caveats:
 *	It can find false positives. (It should check more rigorously).
 *	It assumes 512 byte blocks.
 *	It assumes the first & second superblocks of a filesystem are intact,
 *	and at offsets of fs.fs_sblkno and fs.fs_sblkno*2 respectively.
 *	The 'trick' with sbplus is not particularly palatable, 
 *
 * Comments/suggestions welcome!
 */

#include <stdio.h>
#include <string.h>
#include <sys/param.h>
#include <sys/types.h>

#ifdef __FreeBSD__
#include <ufs/ufs/dinode.h>
#include <ufs/ffs/fs.h>
#else
#include <sys/ufs/ffs_fs.h
#define FS_UFS1_MAGIC  FS_MAGIC
#define FS_UFS2_MAGIC  FS_MAGIC
#endif

#define BLOCKSIZE	1024
#define SB_SIZE		2048

/*
#define	SB_SIZE	(((sizeof(struct fs)+BLOCKSIZE-1)/BLOCKSIZE)*BLOCKSIZE)
#define SB_SIZE SBLOCKSIZE
*/

typedef struct
{
	struct fs	data;
	char	pad[SB_SIZE];
} fsplus;

#define SBLOCK_FLOPPY        0
#define SBLOCK_UFS1       8192
#define SBLOCK_UFS2      65536
#define SBLOCK_PIGGY    262144
#define SBLOCKSIZE        8192
#define SBLOCKSEARCH \
        { SBLOCK_UFS2, SBLOCK_UFS1, SBLOCK_FLOPPY, SBLOCK_PIGGY, -1 }

static int sblock_try[] = SBLOCKSEARCH;

int main(int argc,char **argv)
{
	FILE	*fds;
	fsplus	sblock;
	int i;
	u_int32_t	blockno,
	    size,
	    last;

	if( argc!=2 )
	{
		fputs("Usage: ffs_find special\n",stderr);
		exit(3);
	}
	if( (fds=fopen(argv[1],"r"))==0 )
	{
		perror(argv[1]);
		exit(3);
	}

        for (i = 0; sblock_try[i] != -1; i++) {
		fseek(fds, sblock_try[i], SEEK_SET);
		fread(&sblock.data,SB_SIZE,1,fds);
	}
	
	fseek(fds, 0 , SEEK_SET);
	
	if( fread(&sblock.data,SB_SIZE,1,fds)==0 )
	{
		fputs("Unable to read start of partition.\n",stderr);
		exit(3);
	}
	last=0;
	blockno = 0;
	do {
		if( sblock.data.fs_magic == FS_UFS1_MAGIC ||
		    sblock.data.fs_magic == FS_UFS2_MAGIC )
		{
			printf("\n%lu\n",blockno);
			fflush(stdout);
			if( last && last==blockno-sblock.data.fs_sblkno )
			{
				size=sblock.data.fs_size*(sblock.data.fs_fsize/BLOCKSIZE);
				printf("Possible filesystem at offset %u, size %u (%uMB).\n",
				    last-sblock.data.fs_sblkno,size,
				    size/(1024*1024/BLOCKSIZE));
				/*
				 * Do not skip to end of possible filesystem, as may be
				 * false positive
				 */
			}
			last=blockno;
		}
		if (SB_SIZE > BLOCKSIZE)
			memmove(&sblock.data,((char *)&sblock.data)+BLOCKSIZE,
			    SB_SIZE-BLOCKSIZE);
		++blockno;
	} while(fread(((char *)&sblock.data)+SB_SIZE-BLOCKSIZE,BLOCKSIZE,1,fds));
	return(0);
}