+++ /dev/null
-/*
- * Copyright (C) - Bob Jenkins, May 2006, Public Domain.
- * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
- * Copyright (C) 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * 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.
- */
-
-#include <stdio.h> /* defines printf for tests */
-#include <time.h> /* defines time_t for timings in the test */
-#include <stdint.h> /* defines uint32_t etc */
-#include <sys/param.h> /* attempt to define endianness */
-#include <endian.h> /* attempt to define endianness */
-#include <string.h>
-#include <assert.h>
-#include <urcu/compiler.h>
-
-/*
- * My best guess at if you are big-endian or little-endian. This may
- * need adjustment.
- */
-#if (defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && \
- __BYTE_ORDER == __LITTLE_ENDIAN) || \
- (defined(i386) || defined(__i386__) || defined(__i486__) || \
- defined(__i586__) || defined(__i686__) || defined(vax) || defined(MIPSEL))
-# define HASH_LITTLE_ENDIAN 1
-# define HASH_BIG_ENDIAN 0
-#elif (defined(__BYTE_ORDER) && defined(__BIG_ENDIAN) && \
- __BYTE_ORDER == __BIG_ENDIAN) || \
- (defined(sparc) || defined(POWERPC) || defined(mc68000) || defined(sel))
-# define HASH_LITTLE_ENDIAN 0
-# define HASH_BIG_ENDIAN 1
-#else
-# define HASH_LITTLE_ENDIAN 0
-# define HASH_BIG_ENDIAN 0
-#endif
-
-#define hashsize(n) ((uint32_t)1<<(n))
-#define hashmask(n) (hashsize(n)-1)
-#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); \
-}
-
-static __attribute__((unused))
-uint32_t 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 a, b, c;
-
- /* Set up the internal state */
- a = b = c = 0xdeadbeef + (((uint32_t) length) << 2) + initval;
-
- /*----------------------------------------- handle most of the key */
- while (length > 3) {
- a += k[0];
- b += k[1];
- c += k[2];
- mix(a, b, c);
- length -= 3;
- k += 3;
- }
-
- /*----------------------------------- handle the last 3 uint32_t's */
- switch (length) { /* all the case statements fall through */
- case 3: c += k[2];
- case 2: b += k[1];
- case 1: a += k[0];
- final(a, b, c);
- case 0: /* case 0: nothing left to add */
- break;
- }
- /*---------------------------------------------- report the result */
- return c;
-}
-
-
-/*
- * hashword2() -- same as hashword(), but take two seeds and return two 32-bit
- * values. pc and pb must both be nonnull, and *pc and *pb must both be
- * initialized with seeds. If you pass in (*pb)==0, the output (*pc) will be
- * the same as the return value from hashword().
- */
-static __attribute__((unused))
-void hashword2(const uint32_t *k, size_t length,
- uint32_t *pc, uint32_t *pb)
-{
- uint32_t a, b, c;
-
- /* Set up the internal state */
- a = b = c = 0xdeadbeef + ((uint32_t) (length << 2)) + *pc;
- c += *pb;
-
- while (length > 3) {
- a += k[0];
- b += k[1];
- c += k[2];
- mix(a, b, c);
- length -= 3;
- k += 3;
- }
-
- switch (length) {
- case 3 :
- c += k[2];
- case 2 :
- b += k[1];
- case 1 :
- a += k[0];
- final(a, b, c);
- case 0: /* case 0: nothing left to add */
- break;
- }
-
- *pc = c;
- *pb = b;
-}
-
-/*
- * 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.
- */
-
-static uint32_t hashlittle(const void *key, size_t length, uint32_t initval)
-{
- uint32_t a,b,c;
- 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 (HASH_LITTLE_ENDIAN && ((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;
- }
-
- /*
- * "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).
- */
-#ifndef VALGRIND
-
- 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 /* make valgrind happy */
- const uint8_t *k8;
-
- k8 = (const uint8_t *)k;
- switch (length) {
- case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
- case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
- case 10: c+=((uint32_t)k8[9])<<8; /* fall through */
- case 9 : c+=k8[8]; /* fall through */
- case 8 : b+=k[1]; a+=k[0]; break;
- case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
- case 6 : b+=((uint32_t)k8[5])<<8; /* fall through */
- case 5 : b+=k8[4]; /* fall through */
- case 4 : a+=k[0]; break;
- case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
- case 2 : a+=((uint32_t)k8[1])<<8; /* fall through */
- case 1 : a+=k8[0]; break;
- case 0 : return c;
- }
-#endif /* !valgrind */
- } else if (HASH_LITTLE_ENDIAN && ((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;
- }
-
- 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;
-
- 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;
- }
-
- 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;
-}
-
-#if (CAA_BITS_PER_LONG == 64)
-/*
- * Hash function for number value.
- */
-unsigned long hash_key(void *_key, size_t length, unsigned long seed)
-{
- union {
- uint64_t v64;
- uint32_t v32[2];
- } v;
- union {
- uint64_t v64;
- uint32_t v32[2];
- } key;
-
- assert(length == sizeof(unsigned long));
- v.v64 = (uint64_t) seed;
- key.v64 = (uint64_t) _key;
- hashword2(key.v32, 2, &v.v32[0], &v.v32[1]);
- return v.v64;
-}
-#else
-/*
- * Hash function for number value.
- */
-unsigned long hash_key(void *_key, size_t length, unsigned long seed)
-{
- uint32_t key = (uint32_t) _key;
-
- assert(length == sizeof(uint32_t));
- return hashword(&key, 1, seed);
-}
-#endif
-
-/*
- * Hash function for string.
- */
-unsigned long hash_key_str(void *key, size_t length, unsigned long seed)
-{
- return hashlittle(key, length, seed);
-}
-
-/*
- * Hash function compare for number value.
- */
-unsigned long hash_compare_key(void *key1, size_t key1_len,
- void *key2, size_t key2_len)
-{
- if (key1_len != key2_len) {
- return -1;
- }
-
- if (key1 == key2) {
- return 0;
- }
-
- return 1;
-}
-
-/*
- * Hash compare function for string.
- */
-unsigned long hash_compare_key_str(void *key1, size_t key1_len,
- void *key2, size_t key2_len)
-{
- if (key1_len != key2_len) {
- return -1;
- }
-
- if (strncmp(key1, key2, key1_len) == 0) {
- return 0;
- }
-
- return 1;
-}
projects / lttng-tools.git / blobdiff