Kai Meyer <kai@xxxxxxxxxx> writes:
> Thanks for the helpful response. I'm not entirely sure I understand the
> next part though. I hacked a dirty entry dumper tool:
>
> #include <stdio.h>
> #include <linux/msdos_fs.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <unistd.h>
> #include <string.h>
>
> int main(int argc, char** argv)
> {
> off_t pos = atoi(argv[2]);
> unsigned long block;
> off_t sector;
> unsigned int offset;
> int fd = open(argv[1], O_RDONLY);
> char buf[512];
> struct msdos_dir_entry dirent;
> block = pos / (4096 / 32);
> sector = block * 8;
> offset = pos % (4096 / 32);
> printf("block %lu, sector %lu, offset %u\n", block, sector,
> offset);
> lseek(fd, sector * 512, SEEK_SET);
> if (read(fd, buf, 512) < 0) {
> fprintf(stderr, "Unable to read from device %s\n",
> argv[1]);
> return -1;
> }
> memcpy(&dirent, buf + offset, sizeof(dirent));
> printf("name %s\n", dirent.name);
> printf("attr %u\n", dirent.attr);
> printf("lcase %u\n", dirent.lcase);
> printf("ctime_cs %u\n", dirent.ctime_cs);
> printf("ctime %u\n", dirent.ctime);
> printf("cdate %u\n", dirent.cdate);
> printf("adate %u\n", dirent.adate);
> printf("starthi %u\n", dirent.starthi);
> printf("time %u\n", dirent.time);
> printf("date %u\n", dirent.date);
> printf("start %u\n", dirent.start);
> printf("size %u\n", dirent.size);
> }
>
> Here's what it outputs:
>
> ./vfat_entry /dev/sblsnap0 523793
> block 4092, sector 32736, offset 17
> name
> attr 255
> lcase 255
> ctime_cs 255
> ctime 12799
> cdate 12670
> adate 8224
> starthi 8224
> time 23072
> date 21061
> start 32
> size 2171155456
>
> So, I take starthi, and shift 16 bits left, then and in the start value.
> That should give me the byte address of the first cluster of the file,
> correct?
>
> Then I need to follow the cluster chain until I get a bad value.
It looks like wrong as dirent. Did you use 523793 really? If so, I think
523791 is correct value. :)
--
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
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