+++ /dev/null
-/*
- * Copyright (C) 2011-2012 Free Software Foundation, Inc.
- *
- * Author: Nikos Mavrogiannopoulos
- *
- * This file is part of GnuTLS.
- *
- * The GnuTLS is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public License
- * as published by the Free Software Foundation; either version 3 of
- * the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this program. If not, see <http://www.gnu.org/licenses/>
- *
- */
-
-#include <int.h>
-
-#define INIT_VAL 0x33a1
-/*
--------------------------------------------------------------------------------
-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.
-
-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.
--------------------------------------------------------------------------------
-*/
-#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
-
-/*
--------------------------------------------------------------------------------
-mix -- mix 3 32-bit values reversibly.
-
-This is reversible, so any information in (a,b,c) before mix() is
-still in (a,b,c) after mix().
-
-If four pairs of (a,b,c) inputs are run through mix(), or through
-mix() in reverse, there are at least 32 bits of the output that
-are sometimes the same for one pair and different for another pair.
-This was tested for:
-* pairs that differed by one bit, by two bits, in any combination
- of top bits of (a,b,c), or in any combination of bottom bits of
- (a,b,c).
-* "differ" is defined as +, -, ^, or ~^. For + and -, I transformed
- the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
- is commonly produced by subtraction) look like a single 1-bit
- difference.
-* the base values were pseudorandom, all zero but one bit set, or
- all zero plus a counter that starts at zero.
-
-Some k values for my "a-=c; a^=rot(c,k); c+=b;" arrangement that
-satisfy this are
- 4 6 8 16 19 4
- 9 15 3 18 27 15
- 14 9 3 7 17 3
-Well, "9 15 3 18 27 15" didn't quite get 32 bits diffing
-for "differ" defined as + with a one-bit base and a two-bit delta. I
-used http://burtleburtle.net/bob/hash/avalanche.html to choose
-the operations, constants, and arrangements of the variables.
-
-This does not achieve avalanche. There are input bits of (a,b,c)
-that fail to affect some output bits of (a,b,c), especially of a. The
-most thoroughly mixed value is c, but it doesn't really even achieve
-avalanche in c.
-
-This allows some parallelism. Read-after-writes are good at doubling
-the number of bits affected, so the goal of mixing pulls in the opposite
-direction as the goal of parallelism. I did what I could. Rotates
-seem to cost as much as shifts on every machine I could lay my hands
-on, and rotates are much kinder to the top and bottom bits, so I used
-rotates.
--------------------------------------------------------------------------------
-*/
-#define mix(a,b,c) \
-{ \
- a -= c; a ^= rot(c, 4); c += b; \
- b -= a; b ^= rot(a, 6); a += c; \
- c -= b; c ^= rot(b, 8); b += a; \
- a -= c; a ^= rot(c,16); c += b; \
- b -= a; b ^= rot(a,19); a += c; \
- c -= b; c ^= rot(b, 4); b += a; \
-}
-
-/*
--------------------------------------------------------------------------------
-final -- final mixing of 3 32-bit values (a,b,c) into c
-
-Pairs of (a,b,c) values differing in only a few bits will usually
-produce values of c that look totally different. This was tested for
-* pairs that differed by one bit, by two bits, in any combination
- of top bits of (a,b,c), or in any combination of bottom bits of
- (a,b,c).
-* "differ" is defined as +, -, ^, or ~^. For + and -, I transformed
- the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
- is commonly produced by subtraction) look like a single 1-bit
- difference.
-* the base values were pseudorandom, all zero but one bit set, or
- all zero plus a counter that starts at zero.
-
-These constants passed:
- 14 11 25 16 4 14 24
- 12 14 25 16 4 14 24
-and these came close:
- 4 8 15 26 3 22 24
- 10 8 15 26 3 22 24
- 11 8 15 26 3 22 24
--------------------------------------------------------------------------------
-*/
-#define final(a,b,c) \
-{ \
- c ^= b; c -= rot(b,14); \
- a ^= c; a -= rot(c,11); \
- b ^= a; b -= rot(a,25); \
- c ^= b; c -= rot(b,16); \
- a ^= c; a -= rot(c,4); \
- b ^= a; b -= rot(a,14); \
- c ^= b; c -= rot(b,24); \
-}
-
-
-/*
--------------------------------------------------------------------------------
-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 _asn1_bhash( const void *key, size_t length)
-{
- uint32_t a,b,c; /* internal state */
- const uint8_t *k;
-
- /* Set up the internal state */
- a = b = c = 0xdeadbeef + ((uint32_t)length) + INIT_VAL;
-
- 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;
-}
-
-
-
projects / platform / upstream / libtasn1.git / commitdiff