-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 11/6/12 2:47 PM, Edward Shishkin wrote: > On 11/06/2012 04:49 PM, Michael W. Bombardieri wrote: >> Hi Edward, >> >> I was browsing the git repository for reiserfs... >> https://git.kernel.org/?p=linux/kernel/git/jeffm/reiserfsprogs.git;a=summary >> >> >> This code is entirely new to me. >> >> I have a patch which simplifies the yura_hash function in >> reiserfscore/hashes.c. Here is what it does: Hi Michael - Can you send the patch directly to me (or the list) so I can just git am it? It should have a subject like [PATCH] reiserfscore: clarify yura_hash or something. - -Jeff >> 1. Remove temporary variable 'c' 2. Remove two nested loops which >> always set pow=1 >> >> I tested this using the following code on i386 and amd64. >> >> int main(void) { char *test[] = { "a", "bb", "ccc", "dddd", >> "eeeee", "ffffff", "ggggggg", "red leather", "yellow leather", >> NULL }; size_t n; int i; u32 x; >> >> for (i = 0; test[i] != NULL; i++) { n = strlen(test[i]); >> printf("input=\"%s\" len=%u ", test[i], n); x = >> yura_hash(test[i], (int)n); printf("hash=%lu\n", x); } return >> (0); } >> >> The results between my version and the original yura_hash are >> identical: >> >> input="a" len=1 hash=4084352 input="bb" len=2 hash=4148480 >> input="ccc" len=3 hash=4802688 input="dddd" len=4 hash=11472896 >> input="eeeee" len=5 hash=79455104 input="ffffff" len=6 >> hash=772077312 input="ggggggg" len=7 hash=3531332224 input="red >> leather" len=11 hash=959593472 input="yellow leather" len=14 >> hash=410631168 >> >> I'm not sure if the yura_hash function is used heavily, or at >> all. I'm sending this patch in case you are interested to take a >> look. > > > Hello Michael, > > Your changes look OK to me. > > TBH, I don't like the fact that the pow is set to 1 by such tricky > ways in the mentioned nested loops: it might indicate mistakes in > the original code. > > Generally I think that this hash is not heavily used: everyone uses > either r5, or tea hash, so... Aсked-by: Edward Shishkin > <edward.shishkin@xxxxxxxxx> > > Thanks, Edward. P.S. This is a git repository of Jeff Mahoney, the > reiserfs maintainer, so don't forget cc him ;) > > > >> - Michael >> >> >> --- hashes.c Tue Nov 6 23:21:09 2012 +++ hashes_new.c Tue >> Nov 6 23:26:26 2012 @@ -175,37 +175,26 @@ u32 yura_hash (const >> signed char *msg, int len) { - int j, pow; - u32 a, c; - >> int i; - - for (pow=1,i=1; i < len; i++) pow = pow * 10; - - >> if (len == 1) - a = msg[0]-48; - else - a = (msg[0] - >> 48) * pow; - - for (i=1; i < len; i++) { - c = msg[i] - >> 48; - for (pow=1,j=i; j < len-1; j++) pow = pow * 10; - a = >> a + c * pow; - } - - for (; i < 40; i++) { - c = '0' - >> 48; - for (pow=1,j=i; j < len-1; j++) pow = pow * 10; - a = >> a + c * pow; - } - - for (; i < 256; i++) { - c = i; - >> for (pow=1,j=i; j < len-1; j++) pow = pow * 10; - a = a + c * >> pow; - } - - a = a << 7; - return a; + int i, j, >> pow; + u32 a; + + a = msg[0] - 48; + if (len != 1) { + >> for (i = 1, pow = 1; i < len; i++) + pow *= 10; + >> a *= pow; + } + for (i = 1; i < len; i++) { + for (j >> = i, pow = 1; j < len - 1; j++) + pow *= 10; + >> a += pow * (msg[i] - 48); + } + for (; i < 40; i++) + >> a += '0' - 48; + for (; i < 256; i++) + a += i; + a >> <<= 7; + return a; } >> > > -- To unsubscribe from this list: send the line "unsubscribe > reiserfs-devel" in the body of a message to > majordomo@xxxxxxxxxxxxxxx More majordomo info at > http://vger.kernel.org/majordomo-info.html - -- Jeff Mahoney SUSE Labs -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.18 (Darwin) Comment: GPGTools - http://gpgtools.org Comment: Using GnuPG with Mozilla - http://www.enigmail.net/ iQIcBAEBAgAGBQJQpCtsAAoJEB57S2MheeWyonwP/iFfh06TBivRigIsKui1lEsR Qu440GPB96WBr6TGSCcEgRb9GirVy0yPx/lNTmpyi2m27hn2RivMEgy6r8uVx+4K S7+FRaZ7ysKhmrcX44KBsoIvvDqKIFaOpaTpGWlPK5kfYnRZJ47y0hSWyQgL1C2x Bx2iiGo06wvUIv/tCSKcL95+wWHBYHbd7ouxZ3zZU4orrP40rtxjSxNJoa3PUrhE gNUZfnksQjlYWu5voNbbyR2RXfx5DCZrbag/Wjkr0/VaFv+SDi1vWKaFuYHA4K60 VfsJdJ08xqkPRczCNE+KrqhobDM6hDDisnSek1fWQF3nOLnrF+Gz6FsvhZ2WKkrj sLHP304B+Apcx1S8+exaq58Yap0k24WwCQ8brT6CobgSBcwNph0OhC7FdHVnmvtg 0VqGc6KVQMcWw6x7ktuXpN5zm7RilFDzdSCL2Np/a0ohsVKYB+LACmeMn01rOjrt hMZ44Ac+b0WdomwCVvp38f7P2TBLckpglWwyUVwaK0fcPi0Tv5bznKC4wXYiMIVu uuoDxHBLt1AFUoQB3ND4/PfCHHzThJreVpROd3U50lgJBkIRm6+E5PSUKyixZOjO DRGqhaSHV8Hf4vs3x9I3VSQog94cBTwscg/cnCQZZ4KBNVSffA8DdC4f5AkSazZg TZPsbMbSPKhaIICEmoJ7 =p/We -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe reiserfs-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
