[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>

1 files changed, 11 insertions, 0 deletions

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