Date: Mon, 12 Jun 2000 19:16:34 -0400 From: Sergey Babkin <babkin@bellatlantic.net> To: "Gary T. Corcoran" <gcorcoran@lucent.com> Cc: "Jordan K. Hubbard" <jkh@zippy.cdrom.com>, hackers@FreeBSD.ORG Subject: Re: Way off-topic, but anybody know how to resurrect files from FAT-12? Message-ID: <39456F52.BC507026@bellatlantic.net> References: <200006121452.HAA74024@zippy.cdrom.com> <39453A78.565BDECC@lucent.com>
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"Gary T. Corcoran" wrote: > > "Jordan K. Hubbard" wrote: > > > > I'm sitting here in Seoul, Korea (which is very nice, by the way) and > > I've just managed to delete all 82 images of Kyoto off the FAT-12 format > > Smartcard they were on. Waaaah! > > > > Way back in the Dark Ages I used to hack on FAT-12 code... > Going *way* back in the archives - (had to find a 5-1/4 inch floppy > drive!) it looks as if there are directory entry attributes at the byte > at dirptr+11, and the lower bits (ANDed with 0x1C) should be 0. Otherwise, > if I recall (don't have reference books here), there is a bit saying > the file is deleted (other bits say subdirectory, system file, etc.) > So you may just have to change that one byte (per file) to recover them > (in addition to changing the first byte of the file name which you > already did). The clusters in the FAT have to be re-connected. The number of the first cluster is still stored in the directory entry, as well as directory file size. Then hoping that the files were written sequentially you start from that cluster and link together as many free clusters going sequentially after it to cover this file size. FAT-12 is an array of 12-bit entries, each corresponding to a cluster. An entry contains the number of the next cluster in file. The last cluster in a file has some special value in its FAT entry, something like 0xFFF or 0xFFE, can't remember exactly. The unallocated clusters have value like 000 in their entries. The cluster size for FAT-12 will probably be equal to one sector, that is 512 bytes. At least that's true for diskettes but may be different for the Smartcard. > Hope this helps... > (otherwise find a copy of Norton Disk Doctor... :) Norton Quick Unerase. Which was later licensed by MS and included as standard DOS unerase. Jordan, I can attach either of them off-list if you want. The DOS unerase will work only with the same version of DOS, which for my copy I think is 6.22. -SB To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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