Date: Tue, 4 Sep 2012 12:07:33 +0000 (UTC) From: Gleb Smirnoff <glebius@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r240086 - in head: share/man/man9 sys/conf sys/libkern sys/net sys/sys Message-ID: <201209041207.q84C7Xl4051365@svn.freebsd.org>
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Author: glebius Date: Tue Sep 4 12:07:33 2012 New Revision: 240086 URL: http://svn.freebsd.org/changeset/base/240086 Log: - Move jenkins.h to jenkins_hash.c - Provide missing function that can do hashing of arbitrary sized buffer. - Refetch lookup3.c and do only minimal edits to it, so that diff between our jenkins_hash.c and lookup3.c is minimal. - Add declarations for jenkins_hash(), jenkins_hash32() to sys/hash.h. - Document these functions in hash(9) Obtained from: http://burtleburtle.net/bob/c/lookup3.c Added: head/sys/libkern/jenkins_hash.c - copied, changed from r240081, head/sys/libkern/jenkins.h Deleted: head/sys/libkern/jenkins.h Modified: head/share/man/man9/hash.9 head/sys/conf/files head/sys/net/flowtable.c head/sys/sys/hash.h Modified: head/share/man/man9/hash.9 ============================================================================== --- head/share/man/man9/hash.9 Tue Sep 4 12:02:23 2012 (r240085) +++ head/share/man/man9/hash.9 Tue Sep 4 12:07:33 2012 (r240086) @@ -26,7 +26,7 @@ .\" $OpenBSD: hash.9,v 1.5 2003/04/17 05:08:39 jmc Exp $ .\" $FreeBSD$ .\" -.Dd April 3, 2007 +.Dd September 4, 2012 .Dt HASH 9 .Os .Sh NAME @@ -36,7 +36,9 @@ .Nm hash32_str , .Nm hash32_strn , .Nm hash32_stre , -.Nm hash32_strne +.Nm hash32_strne , +.Nm jenkins_hash32 , +.Nm jenkins_hash .Nd general kernel hashing functions .Sh SYNOPSIS .In sys/hash.h @@ -50,6 +52,10 @@ .Fn hash32_stre "const void *buf" "int end" "const char **ep" "uint32_t hash" .Ft uint32_t .Fn hash32_strne "const void *buf" "size_t len" "int end" "const char **ep" "uint32_t hash" +.Ft uint32_t +.Fn jenkins_hash "const void *buf" "size_t len" "uint32_t hash" +.Ft uint32_t +.Fn jenkins_hash32 "const uint32_t *buf" "size_t count" "uint32_t hash" .Sh DESCRIPTION The .Fn hash32 @@ -107,6 +113,23 @@ is not .Dv NULL , it is set to the point in the buffer at which the hash function terminated hashing. +.Pp +The +.Fn jenkins_hash +function has same semantics as the +.Fn hash32_buf , +but provides more advanced hashing algorithm with better distribution. +.Pp +The +.Fn jenkins_hash32 +uses same hashing algorithm as the +.Fn jenkins_hash +function, but works only on +.Ft uint32_t +sized arrays, thus is simplier and faster. +It accepts an array of +.Ft uint32_t +values in its first argument and size of this array in the second argument. .Sh RETURN VALUES The .Fn hash32 @@ -150,12 +173,24 @@ be revisited. .Sh HISTORY The .Nm -functions were first committed to +functions first appeared in .Nx 1.6 . -The -.Ox -versions were written and massaged for -.Ox 2.3 -by Tobias Weingartner, -and finally committed for -.Ox 3.2 . +The current implementation of +.Nm hash32 +functions was first committed to +.Ox 3.2 , +and later imported to +.Fx 6.1 . +The +.Nm jenkins_hash +functions were added in +.Fx 10.0 . +.Sh AUTHORS +The +.Nm hash32 +functions were written by +.An Tobias Weingartner . +The +.Nm jenkins_hash +functions was written by +Bob Jenkins . Modified: head/sys/conf/files ============================================================================== --- head/sys/conf/files Tue Sep 4 12:02:23 2012 (r240085) +++ head/sys/conf/files Tue Sep 4 12:07:33 2012 (r240086) @@ -2797,6 +2797,7 @@ libkern/inet_aton.c standard libkern/inet_ntoa.c standard libkern/inet_ntop.c standard libkern/inet_pton.c standard +libkern/jenkins_hash.c standard libkern/mcount.c optional profiling-routine libkern/memcchr.c standard libkern/memcmp.c standard Copied and modified: head/sys/libkern/jenkins_hash.c (from r240081, head/sys/libkern/jenkins.h) ============================================================================== --- head/sys/libkern/jenkins.h Tue Sep 4 05:54:43 2012 (r240081, copy source) +++ head/sys/libkern/jenkins_hash.c Tue Sep 4 12:07:33 2012 (r240086) @@ -1,43 +1,44 @@ -#ifndef __LIBKERN_JENKINS_H__ -#define __LIBKERN_JENKINS_H__ /* * Taken from http://burtleburtle.net/bob/c/lookup3.c * $FreeBSD$ */ +#include <sys/hash.h> +#include <machine/endian.h> + /* ------------------------------------------------------------------------------- - lookup3.c, by Bob Jenkins, May 2006, Public Domain. - - These are functions for producing 32-bit hashes for hash table lookup. - hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final() - are externally useful functions. Routines to test the hash are included - if SELF_TEST is defined. You can use this free for any purpose. It's in - the public domain. It has no warranty. - - You probably want to use hashlittle(). hashlittle() and hashbig() - hash byte arrays. hashlittle() is faster than hashbig() on - little-endian machines. Intel and AMD are little-endian machines. - On second thought, you probably want hashlittle2(), which is identical to - hashlittle() except it returns two 32-bit hashes for the price of one. - You could implement hashbig2() if you wanted but I haven't bothered here. +lookup3.c, by Bob Jenkins, May 2006, Public Domain. - If you want to find a hash of, say, exactly 7 integers, do - a = i1; b = i2; c = i3; - mix(a,b,c); - a += i4; b += i5; c += i6; - mix(a,b,c); - a += i7; - final(a,b,c); - then use c as the hash value. If you have a variable length array of - 4-byte integers to hash, use hashword(). If you have a byte array (like - a character string), use hashlittle(). If you have several byte arrays, or - a mix of things, see the comments above hashlittle(). - - Why is this so big? I read 12 bytes at a time into 3 4-byte integers, - then mix those integers. This is fast (you can do a lot more thorough - mixing with 12*3 instructions on 3 integers than you can with 3 instructions - on 1 byte), but shoehorning those bytes into integers efficiently is messy. +These are functions for producing 32-bit hashes for hash table lookup. +hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final() +are externally useful functions. Routines to test the hash are included +if SELF_TEST is defined. You can use this free for any purpose. It's in +the public domain. It has no warranty. + +You probably want to use hashlittle(). hashlittle() and hashbig() +hash byte arrays. hashlittle() is is faster than hashbig() on +little-endian machines. Intel and AMD are little-endian machines. +On second thought, you probably want hashlittle2(), which is identical to +hashlittle() except it returns two 32-bit hashes for the price of one. +You could implement hashbig2() if you wanted but I haven't bothered here. + +If you want to find a hash of, say, exactly 7 integers, do + a = i1; b = i2; c = i3; + mix(a,b,c); + a += i4; b += i5; c += i6; + mix(a,b,c); + a += i7; + final(a,b,c); +then use c as the hash value. If you have a variable length array of +4-byte integers to hash, use hashword(). If you have a byte array (like +a character string), use hashlittle(). If you have several byte arrays, or +a mix of things, see the comments above hashlittle(). + +Why is this so big? I read 12 bytes at a time into 3 4-byte integers, +then mix those integers. This is fast (you can do a lot more thorough +mixing with 12*3 instructions on 3 integers than you can with 3 instructions +on 1 byte), but shoehorning those bytes into integers efficiently is messy. ------------------------------------------------------------------------------- */ @@ -146,12 +147,10 @@ and these came close: hashlittle() has to dance around fitting the key bytes into registers. -------------------------------------------------------------------- */ -static uint32_t -jenkins_hashword( - const uint32_t *k, /* the key, an array of uint32_t values */ - size_t length, /* the length of the key, in uint32_ts */ - uint32_t initval /* the previous hash, or an arbitrary value */ -) +uint32_t jenkins_hash32( +const uint32_t *k, /* the key, an array of uint32_t values */ +size_t length, /* the length of the key, in uint32_ts */ +uint32_t initval) /* the previous hash, or an arbitrary value */ { uint32_t a,b,c; @@ -182,4 +181,283 @@ jenkins_hashword( /*------------------------------------------------------ report the result */ return c; } -#endif + +#if BYTE_ORDER == LITTLE_ENDIAN +/* +------------------------------------------------------------------------------- +hashlittle() -- hash a variable-length key into a 32-bit value + k : the key (the unaligned variable-length array of bytes) + length : the length of the key, counting by bytes + initval : can be any 4-byte value +Returns a 32-bit value. Every bit of the key affects every bit of +the return value. Two keys differing by one or two bits will have +totally different hash values. + +The best hash table sizes are powers of 2. There is no need to do +mod a prime (mod is sooo slow!). If you need less than 32 bits, +use a bitmask. For example, if you need only 10 bits, do + h = (h & hashmask(10)); +In which case, the hash table should have hashsize(10) elements. + +If you are hashing n strings (uint8_t **)k, do it like this: + for (i=0, h=0; i<n; ++i) h = hashlittle( k[i], len[i], h); + +By Bob Jenkins, 2006. bob_jenkins@burtleburtle.net. You may use this +code any way you wish, private, educational, or commercial. It's free. + +Use for hash table lookup, or anything where one collision in 2^^32 is +acceptable. Do NOT use for cryptographic purposes. +------------------------------------------------------------------------------- +*/ + +uint32_t jenkins_hash( const void *key, size_t length, uint32_t initval) +{ + uint32_t a,b,c; /* internal state */ + union { const void *ptr; size_t i; } u; /* needed for Mac Powerbook G4 */ + + /* Set up the internal state */ + a = b = c = 0xdeadbeef + ((uint32_t)length) + initval; + + u.ptr = key; + if ((u.i & 0x3) == 0) { + const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */ + + /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */ + while (length > 12) + { + a += k[0]; + b += k[1]; + c += k[2]; + mix(a,b,c); + length -= 12; + k += 3; + } + + /*----------------------------- handle the last (probably partial) block */ + /* + * "k[2]&0xffffff" actually reads beyond the end of the string, but + * then masks off the part it's not allowed to read. Because the + * string is aligned, the masked-off tail is in the same word as the + * rest of the string. Every machine with memory protection I've seen + * does it on word boundaries, so is OK with this. But VALGRIND will + * still catch it and complain. The masking trick does make the hash + * noticably faster for short strings (like English words). + */ + + switch(length) + { + case 12: c+=k[2]; b+=k[1]; a+=k[0]; break; + case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break; + case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break; + case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break; + case 8 : b+=k[1]; a+=k[0]; break; + case 7 : b+=k[1]&0xffffff; a+=k[0]; break; + case 6 : b+=k[1]&0xffff; a+=k[0]; break; + case 5 : b+=k[1]&0xff; a+=k[0]; break; + case 4 : a+=k[0]; break; + case 3 : a+=k[0]&0xffffff; break; + case 2 : a+=k[0]&0xffff; break; + case 1 : a+=k[0]&0xff; break; + case 0 : return c; /* zero length strings require no mixing */ + } + + } else if ((u.i & 0x1) == 0) { + const uint16_t *k = (const uint16_t *)key; /* read 16-bit chunks */ + const uint8_t *k8; + + /*--------------- all but last block: aligned reads and different mixing */ + while (length > 12) + { + a += k[0] + (((uint32_t)k[1])<<16); + b += k[2] + (((uint32_t)k[3])<<16); + c += k[4] + (((uint32_t)k[5])<<16); + mix(a,b,c); + length -= 12; + k += 6; + } + + /*----------------------------- handle the last (probably partial) block */ + k8 = (const uint8_t *)k; + switch(length) + { + case 12: c+=k[4]+(((uint32_t)k[5])<<16); + b+=k[2]+(((uint32_t)k[3])<<16); + a+=k[0]+(((uint32_t)k[1])<<16); + break; + case 11: c+=((uint32_t)k8[10])<<16; /* fall through */ + case 10: c+=k[4]; + b+=k[2]+(((uint32_t)k[3])<<16); + a+=k[0]+(((uint32_t)k[1])<<16); + break; + case 9 : c+=k8[8]; /* fall through */ + case 8 : b+=k[2]+(((uint32_t)k[3])<<16); + a+=k[0]+(((uint32_t)k[1])<<16); + break; + case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */ + case 6 : b+=k[2]; + a+=k[0]+(((uint32_t)k[1])<<16); + break; + case 5 : b+=k8[4]; /* fall through */ + case 4 : a+=k[0]+(((uint32_t)k[1])<<16); + break; + case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */ + case 2 : a+=k[0]; + break; + case 1 : a+=k8[0]; + break; + case 0 : return c; /* zero length requires no mixing */ + } + + } else { /* need to read the key one byte at a time */ + const uint8_t *k = (const uint8_t *)key; + + /*--------------- all but the last block: affect some 32 bits of (a,b,c) */ + while (length > 12) + { + a += k[0]; + a += ((uint32_t)k[1])<<8; + a += ((uint32_t)k[2])<<16; + a += ((uint32_t)k[3])<<24; + b += k[4]; + b += ((uint32_t)k[5])<<8; + b += ((uint32_t)k[6])<<16; + b += ((uint32_t)k[7])<<24; + c += k[8]; + c += ((uint32_t)k[9])<<8; + c += ((uint32_t)k[10])<<16; + c += ((uint32_t)k[11])<<24; + mix(a,b,c); + length -= 12; + k += 12; + } + + /*-------------------------------- last block: affect all 32 bits of (c) */ + switch(length) /* all the case statements fall through */ + { + case 12: c+=((uint32_t)k[11])<<24; + case 11: c+=((uint32_t)k[10])<<16; + case 10: c+=((uint32_t)k[9])<<8; + case 9 : c+=k[8]; + case 8 : b+=((uint32_t)k[7])<<24; + case 7 : b+=((uint32_t)k[6])<<16; + case 6 : b+=((uint32_t)k[5])<<8; + case 5 : b+=k[4]; + case 4 : a+=((uint32_t)k[3])<<24; + case 3 : a+=((uint32_t)k[2])<<16; + case 2 : a+=((uint32_t)k[1])<<8; + case 1 : a+=k[0]; + break; + case 0 : return c; + } + } + + final(a,b,c); + return c; +} + +#else /* !(BYTE_ORDER == LITTLE_ENDIAN) */ + +/* + * hashbig(): + * This is the same as hashword() on big-endian machines. It is different + * from hashlittle() on all machines. hashbig() takes advantage of + * big-endian byte ordering. + */ +uint32_t jenkins_hash( const void *key, size_t length, uint32_t initval) +{ + uint32_t a,b,c; + union { const void *ptr; size_t i; } u; /* to cast key to (size_t) happily */ + + /* Set up the internal state */ + a = b = c = 0xdeadbeef + ((uint32_t)length) + initval; + + u.ptr = key; + if ((u.i & 0x3) == 0) { + const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */ + + /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */ + while (length > 12) + { + a += k[0]; + b += k[1]; + c += k[2]; + mix(a,b,c); + length -= 12; + k += 3; + } + + /*----------------------------- handle the last (probably partial) block */ + /* + * "k[2]<<8" actually reads beyond the end of the string, but + * then shifts out the part it's not allowed to read. Because the + * string is aligned, the illegal read is in the same word as the + * rest of the string. Every machine with memory protection I've seen + * does it on word boundaries, so is OK with this. But VALGRIND will + * still catch it and complain. The masking trick does make the hash + * noticably faster for short strings (like English words). + */ + + switch(length) + { + case 12: c+=k[2]; b+=k[1]; a+=k[0]; break; + case 11: c+=k[2]&0xffffff00; b+=k[1]; a+=k[0]; break; + case 10: c+=k[2]&0xffff0000; b+=k[1]; a+=k[0]; break; + case 9 : c+=k[2]&0xff000000; b+=k[1]; a+=k[0]; break; + case 8 : b+=k[1]; a+=k[0]; break; + case 7 : b+=k[1]&0xffffff00; a+=k[0]; break; + case 6 : b+=k[1]&0xffff0000; a+=k[0]; break; + case 5 : b+=k[1]&0xff000000; a+=k[0]; break; + case 4 : a+=k[0]; break; + case 3 : a+=k[0]&0xffffff00; break; + case 2 : a+=k[0]&0xffff0000; break; + case 1 : a+=k[0]&0xff000000; break; + case 0 : return c; /* zero length strings require no mixing */ + } + + } else { /* need to read the key one byte at a time */ + const uint8_t *k = (const uint8_t *)key; + + /*--------------- all but the last block: affect some 32 bits of (a,b,c) */ + while (length > 12) + { + a += ((uint32_t)k[0])<<24; + a += ((uint32_t)k[1])<<16; + a += ((uint32_t)k[2])<<8; + a += ((uint32_t)k[3]); + b += ((uint32_t)k[4])<<24; + b += ((uint32_t)k[5])<<16; + b += ((uint32_t)k[6])<<8; + b += ((uint32_t)k[7]); + c += ((uint32_t)k[8])<<24; + c += ((uint32_t)k[9])<<16; + c += ((uint32_t)k[10])<<8; + c += ((uint32_t)k[11]); + mix(a,b,c); + length -= 12; + k += 12; + } + + /*-------------------------------- last block: affect all 32 bits of (c) */ + switch(length) /* all the case statements fall through */ + { + case 12: c+=k[11]; + case 11: c+=((uint32_t)k[10])<<8; + case 10: c+=((uint32_t)k[9])<<16; + case 9 : c+=((uint32_t)k[8])<<24; + case 8 : b+=k[7]; + case 7 : b+=((uint32_t)k[6])<<8; + case 6 : b+=((uint32_t)k[5])<<16; + case 5 : b+=((uint32_t)k[4])<<24; + case 4 : a+=k[3]; + case 3 : a+=((uint32_t)k[2])<<8; + case 2 : a+=((uint32_t)k[1])<<16; + case 1 : a+=((uint32_t)k[0])<<24; + break; + case 0 : return c; + } + } + + final(a,b,c); + return c; +} +#endif Modified: head/sys/net/flowtable.c ============================================================================== --- head/sys/net/flowtable.c Tue Sep 4 12:02:23 2012 (r240085) +++ head/sys/net/flowtable.c Tue Sep 4 12:07:33 2012 (r240086) @@ -41,6 +41,7 @@ __FBSDID("$FreeBSD$"); #include <sys/bitstring.h> #include <sys/condvar.h> #include <sys/callout.h> +#include <sys/hash.h> #include <sys/kernel.h> #include <sys/kthread.h> #include <sys/limits.h> @@ -73,7 +74,6 @@ __FBSDID("$FreeBSD$"); #include <netinet/udp.h> #include <netinet/sctp.h> -#include <libkern/jenkins.h> #include <ddb/ddb.h> struct ipv4_tuple { @@ -585,7 +585,7 @@ ipv4_flow_lookup_hash_internal( } else offset = V_flow_hashjitter + proto; - return (jenkins_hashword(key, 3, offset)); + return (jenkins_hash32(key, 3, offset)); } static struct flentry * @@ -791,7 +791,7 @@ ipv6_flow_lookup_hash_internal( } else offset = V_flow_hashjitter + proto; - return (jenkins_hashword(key, 9, offset)); + return (jenkins_hash32(key, 9, offset)); } static struct flentry * Modified: head/sys/sys/hash.h ============================================================================== --- head/sys/sys/hash.h Tue Sep 4 12:02:23 2012 (r240085) +++ head/sys/sys/hash.h Tue Sep 4 12:07:33 2012 (r240086) @@ -118,4 +118,13 @@ hash32_strne(const void *buf, size_t len return hash; } + +#ifdef _KERNEL +/* + * Hashing function from Bob Jenkins. Implementation in libkern/jenkins_hash.c. + */ +uint32_t jenkins_hash(const void *, size_t, uint32_t); +uint32_t jenkins_hash32(const uint32_t *, size_t, uint32_t); +#endif /* _KERNEL */ + #endif /* !_SYS_HASH_H_ */
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