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[PATCH] fat: cleanup and optimization of checksum

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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>
This commit is contained in:
OGAWA Hirofumi 2005-10-30 15:03:49 -08:00 committed by Linus Torvalds
parent 4e57b68178
commit 451cbaa1c3
3 changed files with 14 additions and 10 deletions
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10
fs/fat/dir.c
View File

@ -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;
}

3
fs/vfat/namei.c
View File

@ -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++) {

11
include/linux/msdos_fs.h
View File

@ -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