Messages in this thread | | | Subject | Re: [PATCH,RFC] ext3: Add support for non-native signed/unsigned htree hash algorithms | From | Matt Mackall <> | Date | Wed, 22 Oct 2008 11:30:08 -0500 |
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On Mon, 2008-10-20 at 23:43 -0400, Theodore Ts'o wrote: > The original ext3 hash algorithms assumed that variables of type char > were signed, as God and K&R intended. Unfortunately, this assumption > is not true on some architectures. Userspace support for marking > filesystems with non-native signed/unsigned chars was added two years > ago, but the kernel-side support was never added (until now). > > Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> > Cc: akpm@linux-foundation.org > Cc: linux-kernel@vger.kernel.org > --- > fs/ext3/hash.c | 42 +++++++++++++++++++++++++++++++++--------- > fs/ext3/namei.c | 7 +++++++ > fs/ext3/super.c | 15 +++++++++++++++ > include/linux/ext3_fs.h | 28 +++++++++++++++++++++++++++- > include/linux/ext3_fs_sb.h | 1 + > 5 files changed, 83 insertions(+), 10 deletions(-) > > diff --git a/fs/ext3/hash.c b/fs/ext3/hash.c > index c30e149..855eacb 100644 > --- a/fs/ext3/hash.c > +++ b/fs/ext3/hash.c > @@ -35,11 +35,20 @@ static void TEA_transform(__u32 buf[4], __u32 const in[]) > > > /* The old legacy hash */ > -static __u32 dx_hack_hash (const char *name, int len) > +static __u32 dx_hack_hash (const char *name, int len, int unsigned_flag) > { > - __u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9; > + __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9; > + const unsigned char *ucp = (const unsigned char *) name; > + const signed char *scp = (const signed char *) name; > + int c; > + > while (len--) { > - __u32 hash = hash1 + (hash0 ^ (*name++ * 7152373)); > + if (unsigned_flag) > + c = (int) *ucp++; > + else > + c = (int) *scp++;
Branch in the inner loop? Space after typecast?
> for (i=0; i < len; i++) { > if ((i % 4) == 0) > val = pad; > - val = msg[i] + (val << 8); > + if (unsigned_flag) > + c = (int) ucp[i]; > + else > + c = (int) scp[i]; > + > + val = c + (val << 8);
And here.
-- Mathematics is the supreme nostalgia of our time.
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