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| author | OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> | 2005-10-30 15:03:49 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-10-30 17:37:32 -0800 |
| commit | 451cbaa1c328082832a8fbcc427cd4416c602c5a (patch) | |
| tree | 139c3d33d0cf3f9eba214c504e4173f54c6cf66d | |
| parent | 4e57b6817880946a3a78d5d8cad1ace363f7e449 (diff) | |
| download | lwn-451cbaa1c328082832a8fbcc427cd4416c602c5a.tar.gz lwn-451cbaa1c328082832a8fbcc427cd4416c602c5a.zip | |
[PATCH] fat: cleanup and optimization of checksum
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | fs/fat/dir.c | 10 | ||||
| -rw-r--r-- | fs/vfat/namei.c | 3 | ||||
| -rw-r--r-- | include/linux/msdos_fs.h | 11 |
3 files changed, 14 insertions, 10 deletions
diff --git a/fs/fat/dir.c b/fs/fat/dir.c index 895049b2ac9c..204d8614406f 100644 --- a/fs/fat/dir.c +++ b/fs/fat/dir.c @@ -263,7 +263,6 @@ parse_record: unsigned char id; unsigned char slot; unsigned char slots; - unsigned char sum; unsigned char alias_checksum; if (!unicode) { @@ -317,9 +316,7 @@ parse_long: goto parse_long; if (IS_FREE(de->name) || (de->attr & ATTR_VOLUME)) continue; - for (sum = 0, i = 0; i < 11; i++) - sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + de->name[i]; - if (sum != alias_checksum) + if (fat_checksum(de->name) != alias_checksum) nr_slots = 0; } @@ -479,7 +476,6 @@ GetNew: unsigned char id; unsigned char slot; unsigned char slots; - unsigned char sum; unsigned char alias_checksum; if (!unicode) { @@ -534,9 +530,7 @@ ParseLong: goto ParseLong; if (IS_FREE(de->name) || (de->attr & ATTR_VOLUME)) goto RecEnd; - for (sum = 0, i = 0; i < 11; i++) - sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + de->name[i]; - if (sum != alias_checksum) + if (fat_checksum(de->name) != alias_checksum) long_slots = 0; } diff --git a/fs/vfat/namei.c b/fs/vfat/namei.c index 1c6f6b57ef1c..467346b123d9 100644 --- a/fs/vfat/namei.c +++ b/fs/vfat/namei.c @@ -621,8 +621,7 @@ static int vfat_build_slots(struct inode *dir, const unsigned char *name, } /* build the entry of long file name */ - for (cksum = i = 0; i < 11; i++) - cksum = (((cksum&1)<<7)|((cksum&0xfe)>>1)) + msdos_name[i]; + cksum = fat_checksum(msdos_name); *nr_slots = usize / 13; for (ps = slots, i = *nr_slots; i > 0; i--, ps++) { diff --git a/include/linux/msdos_fs.h b/include/linux/msdos_fs.h index 9a3d27257984..941da5c016a0 100644 --- a/include/linux/msdos_fs.h +++ b/include/linux/msdos_fs.h @@ -282,6 +282,17 @@ static inline u8 fat_attr(struct inode *inode) MSDOS_I(inode)->i_attrs; } +static inline unsigned char fat_checksum(const __u8 *name) +{ + unsigned char s = name[0]; + s = (s<<7) + (s>>1) + name[1]; s = (s<<7) + (s>>1) + name[2]; + s = (s<<7) + (s>>1) + name[3]; s = (s<<7) + (s>>1) + name[4]; + s = (s<<7) + (s>>1) + name[5]; s = (s<<7) + (s>>1) + name[6]; + s = (s<<7) + (s>>1) + name[7]; s = (s<<7) + (s>>1) + name[8]; + s = (s<<7) + (s>>1) + name[9]; s = (s<<7) + (s>>1) + name[10]; + return s; +} + static inline sector_t fat_clus_to_blknr(struct msdos_sb_info *sbi, int clus) { return ((sector_t)clus - FAT_START_ENT) * sbi->sec_per_clus |