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authorOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>2005-10-30 15:03:49 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-30 17:37:32 -0800
commit451cbaa1c328082832a8fbcc427cd4416c602c5a (patch)
tree139c3d33d0cf3f9eba214c504e4173f54c6cf66d
parent4e57b6817880946a3a78d5d8cad1ace363f7e449 (diff)
downloadop-kernel-dev-451cbaa1c328082832a8fbcc427cd4416c602c5a.zip
op-kernel-dev-451cbaa1c328082832a8fbcc427cd4416c602c5a.tar.gz
[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.c10
-rw-r--r--fs/vfat/namei.c3
-rw-r--r--include/linux/msdos_fs.h11
3 files changed, 14 insertions, 10 deletions
diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 895049b..204d861 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 1c6f6b5..467346b 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 9a3d272..941da5c 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
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