--- /dev/null
+/*
+ * Copyright (C) - Bob Jenkins, May 2006, Public Domain.
+ * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
+ *
+ * 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>
+
+/*
+ * 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); \
+}
+
+/*
+ * 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 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;
+}
+
+/*
+ * 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;
+}
+
+/*
+ * 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