Dear PostgreSQL Developers,
This patch is a "diff -c" against the hashfunc.c from postgresql-8.3beta1.
It implements the 2006 version of the hash function by Bob Jenkins. Its
features include a better and faster hash function. I have included the
versions supporting big-endian and little-endian machines that will be
selected based on the machine configuration. Currently, I have hash_any()
just a stub calling hashlittle and hashbig. In order to allow the hash
index to support large indexes (>10^9 entries), the hash function needs
to be able to provide 64-bit hashes.
The functions hashbig2/hashlittle2 produce 2 32-bit hashes that can be
used as a 64-bit hash value. I would like some feedback as to how best
to include 64-bit hashes within our current 32-bit hash infrastructure.
The hash-merge can simple use one of the 2 32-bit pieces to provide
the current 32-bit hash values needed. Then they could be pulled directly
from the hash index and not need to be recalculated at run time. What
would be the best way to implement this in a way that will work on
machines without support for 64-bit integers?
The current patch passes all the regression tests, but has a few warnings
for the different variations of the new hash function. Until the design
has crystalized, I am not going to worry about them and I want testers to
have access to the different functions. I am doing the initial patches
to the hash index code based on a 32-bit hash, but I would like to add the
64-bit hash support pretty early in the development cycle in order to
allow for better testing. Any thoughts would be welcome.
Regards,
Ken
*** hashfunc.c pgsql/src/backend/access/hash/hashfunc.c,v 1.53 2007/09/21
22:52:52 tgl
--- hashfunc.c_NEW32 Wed Oct 17 13:58:10 2007
***************
*** 197,230 ****
* This hash function was written by Bob Jenkins
* ([EMAIL PROTECTED]), and superficially adapted
* for PostgreSQL by Neil Conway. For more information on this
! * hash function, see http://burtleburtle.net/bob/hash/doobs.html,
! * or Bob's article in Dr. Dobb's Journal, Sept. 1997.
*/
/*----------
* mix -- mix 3 32-bit values reversibly.
! * For every delta with one or two bits set, and the deltas of all three
! * high bits or all three low bits, whether the original value of a,b,c
! * is almost all zero or is uniformly distributed,
! * - If mix() is run forward or backward, at least 32 bits in a,b,c
! * have at least 1/4 probability of changing.
! * - If mix() is run forward, every bit of c will change between 1/3 and
! * 2/3 of the time. (Well, 22/100 and 78/100 for some 2-bit deltas.)
*----------
*/
#define mix(a,b,c) \
{ \
! a -= b; a -= c; a ^= ((c)>>13); \
! b -= c; b -= a; b ^= ((a)<<8); \
! c -= a; c -= b; c ^= ((b)>>13); \
! a -= b; a -= c; a ^= ((c)>>12); \
! b -= c; b -= a; b ^= ((a)<<16); \
! c -= a; c -= b; c ^= ((b)>>5); \
! a -= b; a -= c; a ^= ((c)>>3); \
! b -= c; b -= a; b ^= ((a)<<10); \
! c -= a; c -= b; c ^= ((b)>>15); \
}
/*
* hash_any() -- hash a variable-length key into a 32-bit value
* k : the key (the unaligned variable-length array
of bytes)
--- 197,1060 ----
* This hash function was written by Bob Jenkins
* ([EMAIL PROTECTED]), and superficially adapted
* for PostgreSQL by Neil Conway. For more information on this
! * hash function, see http://burtleburtle.net/bob/hash/#lookup
! * and http://burtleburtle.net/bob/hash/lookup3.txt. Further
! * information on the original version of the hash function can
! * be found in Bob's article in Dr. Dobb's Journal, Sept. 1997.
*/
+ #define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
+
+ #ifndef WORS_BIGENDIAN
+ #define HASH_LITTLE_ENDIAN 1
+ #define HASH_BIG_ENDIAN 0
+ #else
+ #define HASH_LITTLE_ENDIAN 0
+ #define HASH_BIG_ENDIAN 1
+ #endif
+
/*----------
* 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); \
+ }
+
+ /*----------
+ * This works on all machines. To be useful, it requires
+ * -- that the key be an array of uint32's, and
+ * -- that the length be the number of uint32's in the key
+ *
+ * The function hashword() is identical to hashlittle() on little-endian
+ * machines, and identical to hashbig() on big-endian machines,
+ * except that the length has to be measured in uint32s rather than in
+ * bytes. hashlittle() is more complicated than hashword() only because
+ * hashlittle() has to dance around fitting the key bytes into registers.
+ *----------
+ */
+ Datum
+ hashword(
+ const uint32 *k, /* the key, an array of uint32 values */
+ size_t length, /* the length of the key, in uint32s */
+ uint32 initval) /* the previous hash, or an arbitrary value */
+ {
+ uint32 a,b,c;
+
+ /* Set up the internal state */
+ a = b = c = 0xdeadbeef + (((uint32)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'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 UInt32GetDatum(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().
+ *----------
+ */
+ void hashword2 (
+ const uint32 *k, /* the key, an array of uint32 values */
+ size_t length, /* the length of the key, in uint32s */
+ uint32 *pc, /* IN: seed OUT: primary hash value */
+ uint32 *pb) /* IN: more seed OUT: secondary hash value */
+ {
+ uint32 a,b,c;
+
+ /* Set up the internal state */
+ a = b = c = 0xdeadbeef + ((uint32)(length<<2)) + *pc;
+ c += *pb;
+
+ /*------------------------------------------------- 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'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
*/
+ *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 **)k, do it like this:
+ * for (i=0, h=0; i<n; ++i) h = hashlittle( k[i], len[i], h);
+ *
+ * By Bob Jenkins, 2006. [EMAIL PROTECTED] 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.
+ *----------
+ */
+
+ Datum
+ hashlittle( const void *key, size_t length, uint32 initval)
+ {
+ uint32 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)length) + initval;
+
+ u.ptr = key;
+ if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
+ const uint32 *k = (const uint32 *)key; /* read 32-bit chunks */
+ #ifdef VALGRIND
+ const uint8 *k8;
+ #endif
+
+ /*------ 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).
+ */
+ #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 UInt32GetDatum(c); /* zero length requires no mixing */
+ }
+
+ #else /* make valgrind happy */
+
+ k8 = (const uint8 *)k;
+ switch(length)
+ {
+ case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
+ case 11: c+=((uint32)k8[10])<<16; /* fall through */
+ case 10: c+=((uint32)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)k8[6])<<16; /* fall through */
+ case 6 : b+=((uint32)k8[5])<<8; /* fall through */
+ case 5 : b+=k8[4]; /* fall through */
+ case 4 : a+=k[0]; break;
+ case 3 : a+=((uint32)k8[2])<<16; /* fall through */
+ case 2 : a+=((uint32)k8[1])<<8; /* fall through */
+ case 1 : a+=k8[0]; break;
+ case 0 : return UInt32GetDatum(c);
+ }
+
+ #endif /* !valgrind */
+
+ } else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
+ const uint16 *k = (const uint16 *)key; /* read 16-bit chunks */
+ const uint8 *k8;
+
+ /*--------------- all but last block: aligned reads and different mixing
*/
+ while (length > 12)
+ {
+ a += k[0] + (((uint32)k[1])<<16);
+ b += k[2] + (((uint32)k[3])<<16);
+ c += k[4] + (((uint32)k[5])<<16);
+ mix(a,b,c);
+ length -= 12;
+ k += 6;
+ }
+
+ /*----------------------------- handle the last (probably partial) block
*/
+ k8 = (const uint8 *)k;
+ switch(length)
+ {
+ case 12: c+=k[4]+(((uint32)k[5])<<16);
+ b+=k[2]+(((uint32)k[3])<<16);
+ a+=k[0]+(((uint32)k[1])<<16);
+ break;
+ case 11: c+=((uint32)k8[10])<<16; /* fall through */
+ case 10: c+=k[4];
+ b+=k[2]+(((uint32)k[3])<<16);
+ a+=k[0]+(((uint32)k[1])<<16);
+ break;
+ case 9 : c+=k8[8]; /* fall through */
+ case 8 : b+=k[2]+(((uint32)k[3])<<16);
+ a+=k[0]+(((uint32)k[1])<<16);
+ break;
+ case 7 : b+=((uint32)k8[6])<<16; /* fall through */
+ case 6 : b+=k[2];
+ a+=k[0]+(((uint32)k[1])<<16);
+ break;
+ case 5 : b+=k8[4]; /* fall through */
+ case 4 : a+=k[0]+(((uint32)k[1])<<16);
+ break;
+ case 3 : a+=((uint32)k8[2])<<16; /* fall through */
+ case 2 : a+=k[0];
+ break;
+ case 1 : a+=k8[0];
+ break;
+ case 0 : return UInt32GetDatum(c); /* zero length requires no mixing
*/
+ }
+
+ } else { /* need to read the key one byte at a time
*/
+ const uint8 *k = (const uint8 *)key;
+
+ /*--------------- all but the last block: affect some 32 bits of (a,b,c)
*/
+ while (length > 12)
+ {
+ a += k[0];
+ a += ((uint32)k[1])<<8;
+ a += ((uint32)k[2])<<16;
+ a += ((uint32)k[3])<<24;
+ b += k[4];
+ b += ((uint32)k[5])<<8;
+ b += ((uint32)k[6])<<16;
+ b += ((uint32)k[7])<<24;
+ c += k[8];
+ c += ((uint32)k[9])<<8;
+ c += ((uint32)k[10])<<16;
+ c += ((uint32)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)k[11])<<24;
+ case 11: c+=((uint32)k[10])<<16;
+ case 10: c+=((uint32)k[9])<<8;
+ case 9 : c+=k[8];
+ case 8 : b+=((uint32)k[7])<<24;
+ case 7 : b+=((uint32)k[6])<<16;
+ case 6 : b+=((uint32)k[5])<<8;
+ case 5 : b+=k[4];
+ case 4 : a+=((uint32)k[3])<<24;
+ case 3 : a+=((uint32)k[2])<<16;
+ case 2 : a+=((uint32)k[1])<<8;
+ case 1 : a+=k[0];
+ break;
+ case 0 : return UInt32GetDatum(c);
+ }
+ }
+
+ final(a,b,c);
+ return UInt32GetDatum(c);
+ }
+
+
+ /*----------
+ * hashlittle2: return 2 32-bit hash values
+ *
+ * This is identical to hashlittle(), except it returns two 32-bit hash
+ * values instead of just one. This is good enough for hash table
+ * lookup with 2^^64 buckets, or if you want a second hash if you're not
+ * happy with the first, or if you want a probably-unique 64-bit ID for
+ * the key. *pc is better mixed than *pb, so use *pc first. If you want
+ * a 64-bit value do something like "*pc + (((uint64_t)*pb)<<32)".
+ *----------
+ */
+ void hashlittle2(
+ const void *key, /* the key to hash */
+ size_t length, /* length of the key */
+ uint32 *pc, /* IN: primary initval, OUT: primary hash */
+ uint32 *pb) /* IN: secondary initval, OUT: secondary hash */
+ {
+ uint32 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)length) + *pc;
+ c += *pb;
+
+ u.ptr = key;
+ if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
+ const uint32 *k = (const uint32 *)key; /* read 32-bit chunks */
+ #ifdef VALGRIND
+ const uint8 *k8;
+ #endif
+
+ /*------ 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).
+ */
+ #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 : *pc=c; *pb=b; return; /* zero length strings require no mixing
*/
+ }
+
+ #else /* make valgrind happy */
+
+ k8 = (const uint8 *)k;
+ switch(length)
+ {
+ case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
+ case 11: c+=((uint32)k8[10])<<16; /* fall through */
+ case 10: c+=((uint32)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)k8[6])<<16; /* fall through */
+ case 6 : b+=((uint32)k8[5])<<8; /* fall through */
+ case 5 : b+=k8[4]; /* fall through */
+ case 4 : a+=k[0]; break;
+ case 3 : a+=((uint32)k8[2])<<16; /* fall through */
+ case 2 : a+=((uint32)k8[1])<<8; /* fall through */
+ case 1 : a+=k8[0]; break;
+ case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing
*/
+ }
+
+ #endif /* !valgrind */
+
+ } else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
+ const uint16 *k = (const uint16 *)key; /* read 16-bit chunks */
+ const uint8 *k8;
+
+ /*--------------- all but last block: aligned reads and different mixing
*/
+ while (length > 12)
+ {
+ a += k[0] + (((uint32)k[1])<<16);
+ b += k[2] + (((uint32)k[3])<<16);
+ c += k[4] + (((uint32)k[5])<<16);
+ mix(a,b,c);
+ length -= 12;
+ k += 6;
+ }
+
+ /*----------------------------- handle the last (probably partial) block
*/
+ k8 = (const uint8 *)k;
+ switch(length)
+ {
+ case 12: c+=k[4]+(((uint32)k[5])<<16);
+ b+=k[2]+(((uint32)k[3])<<16);
+ a+=k[0]+(((uint32)k[1])<<16);
+ break;
+ case 11: c+=((uint32)k8[10])<<16; /* fall through */
+ case 10: c+=k[4];
+ b+=k[2]+(((uint32)k[3])<<16);
+ a+=k[0]+(((uint32)k[1])<<16);
+ break;
+ case 9 : c+=k8[8]; /* fall through */
+ case 8 : b+=k[2]+(((uint32)k[3])<<16);
+ a+=k[0]+(((uint32)k[1])<<16);
+ break;
+ case 7 : b+=((uint32)k8[6])<<16; /* fall through */
+ case 6 : b+=k[2];
+ a+=k[0]+(((uint32)k[1])<<16);
+ break;
+ case 5 : b+=k8[4]; /* fall through */
+ case 4 : a+=k[0]+(((uint32)k[1])<<16);
+ break;
+ case 3 : a+=((uint32)k8[2])<<16; /* fall through */
+ case 2 : a+=k[0];
+ break;
+ case 1 : a+=k8[0];
+ break;
+ case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing
*/
+ }
+
+ } else { /* need to read the key one byte at a time
*/
+ const uint8 *k = (const uint8 *)key;
+
+ /*--------------- all but the last block: affect some 32 bits of (a,b,c)
*/
+ while (length > 12)
+ {
+ a += k[0];
+ a += ((uint32)k[1])<<8;
+ a += ((uint32)k[2])<<16;
+ a += ((uint32)k[3])<<24;
+ b += k[4];
+ b += ((uint32)k[5])<<8;
+ b += ((uint32)k[6])<<16;
+ b += ((uint32)k[7])<<24;
+ c += k[8];
+ c += ((uint32)k[9])<<8;
+ c += ((uint32)k[10])<<16;
+ c += ((uint32)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)k[11])<<24;
+ case 11: c+=((uint32)k[10])<<16;
+ case 10: c+=((uint32)k[9])<<8;
+ case 9 : c+=k[8];
+ case 8 : b+=((uint32)k[7])<<24;
+ case 7 : b+=((uint32)k[6])<<16;
+ case 6 : b+=((uint32)k[5])<<8;
+ case 5 : b+=k[4];
+ case 4 : a+=((uint32)k[3])<<24;
+ case 3 : a+=((uint32)k[2])<<16;
+ case 2 : a+=((uint32)k[1])<<8;
+ case 1 : a+=k[0];
+ break;
+ case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing
*/
+ }
+ }
+
+ final(a,b,c);
+ *pc=c; *pb=b;
+ }
+
+
+
+ /*----------
+ * 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.
+ *----------
+ */
+ Datum
+ hashbig( const void *key, size_t length, uint32 initval)
+ {
+ uint32 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)length) + initval;
+
+ u.ptr = key;
+ if (HASH_BIG_ENDIAN && ((u.i & 0x3) == 0)) {
+ const uint32 *k = (const uint32 *)key; /* read 32-bit chunks */
+ #ifdef VALGRIND
+ const uint8 *k8;
+ #endif
+
+ /*------ 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).
+ */
+ #ifndef VALGRIND
+
+ 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 UInt32GetDatum(c); /* zero length requires no mixing
*/
+ }
+
+ #else /* make valgrind happy */
+
+ k8 = (const uint8 *)k;
+ switch(length) /* all the case statements fall through
*/
+ {
+ case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
+ case 11: c+=((uint32)k8[10])<<8; /* fall through */
+ case 10: c+=((uint32)k8[9])<<16; /* fall through */
+ case 9 : c+=((uint32)k8[8])<<24; /* fall through */
+ case 8 : b+=k[1]; a+=k[0]; break;
+ case 7 : b+=((uint32)k8[6])<<8; /* fall through */
+ case 6 : b+=((uint32)k8[5])<<16; /* fall through */
+ case 5 : b+=((uint32)k8[4])<<24; /* fall through */
+ case 4 : a+=k[0]; break;
+ case 3 : a+=((uint32)k8[2])<<8; /* fall through */
+ case 2 : a+=((uint32)k8[1])<<16; /* fall through */
+ case 1 : a+=((uint32)k8[0])<<24; break;
+ case 0 : return UInt32GetDatum(c);
+ }
+
+ #endif /* !VALGRIND */
+
+ } else { /* need to read the key one byte at a time
*/
+ const uint8 *k = (const uint8 *)key;
+
+ /*--------------- all but the last block: affect some 32 bits of (a,b,c)
*/
+ while (length > 12)
+ {
+ a += ((uint32)k[0])<<24;
+ a += ((uint32)k[1])<<16;
+ a += ((uint32)k[2])<<8;
+ a += ((uint32)k[3]);
+ b += ((uint32)k[4])<<24;
+ b += ((uint32)k[5])<<16;
+ b += ((uint32)k[6])<<8;
+ b += ((uint32)k[7]);
+ c += ((uint32)k[8])<<24;
+ c += ((uint32)k[9])<<16;
+ c += ((uint32)k[10])<<8;
+ c += ((uint32)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)k[10])<<8;
+ case 10: c+=((uint32)k[9])<<16;
+ case 9 : c+=((uint32)k[8])<<24;
+ case 8 : b+=k[7];
+ case 7 : b+=((uint32)k[6])<<8;
+ case 6 : b+=((uint32)k[5])<<16;
+ case 5 : b+=((uint32)k[4])<<24;
+ case 4 : a+=k[3];
+ case 3 : a+=((uint32)k[2])<<8;
+ case 2 : a+=((uint32)k[1])<<16;
+ case 1 : a+=((uint32)k[0])<<24;
+ break;
+ case 0 : return UInt32GetDatum(c);
+ }
+ }
+
+ final(a,b,c);
+ return UInt32GetDatum(c);
+ }
+
+ /*----------
+ * hashbig2: return 2 32-bit hash values
+ *
+ * This is identical to hashbig(), except it returns two 32-bit hash
+ * values instead of just one. This is good enough for hash table
+ * lookup with 2^^64 buckets, or if you want a second hash if you're not
+ * happy with the first, or if you want a probably-unique 64-bit ID for
+ * the key. *pc is better mixed than *pb, so use *pc first. If you want
+ * a 64-bit value do something like "*pc + (((uint64_t)*pb)<<32)".
+ *----------
+ */
+ void hashbig2(
+ const void *key, /* the key to hash */
+ size_t length, /* length of the key */
+ uint32 *pc, /* IN: primary initval, OUT: primary hash */
+ uint32 *pb) /* IN: secondary initval, OUT: secondary hash */
+ {
+ uint32 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)length) + *pc;
+ c += *pb;
+
+ u.ptr = key;
+ if (HASH_BIG_ENDIAN && ((u.i & 0x3) == 0)) {
+ const uint32 *k = (const uint32 *)key; /* read 32-bit chunks */
+ #ifdef VALGRIND
+ const uint8 *k8;
+ #endif
+
+ /*------ 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).
+ */
+ #ifndef VALGRIND
+
+ 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 : *pc=c; *pb=b; return; /* zero length strings require no mixing
*/
+ }
+
+ #else /* make valgrind happy */
+
+ k8 = (const uint8 *)k;
+ switch(length) /* all the case statements fall through
*/
+ {
+ case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
+ case 11: c+=((uint32)k8[10])<<8; /* fall through */
+ case 10: c+=((uint32)k8[9])<<16; /* fall through */
+ case 9 : c+=((uint32)k8[8])<<24; /* fall through */
+ case 8 : b+=k[1]; a+=k[0]; break;
+ case 7 : b+=((uint32)k8[6])<<8; /* fall through */
+ case 6 : b+=((uint32)k8[5])<<16; /* fall through */
+ case 5 : b+=((uint32)k8[4])<<24; /* fall through */
+ case 4 : a+=k[0]; break;
+ case 3 : a+=((uint32)k8[2])<<8; /* fall through */
+ case 2 : a+=((uint32)k8[1])<<16; /* fall through */
+ case 1 : a+=((uint32)k8[0])<<24; break;
+ case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing
*/
+ }
+
+ #endif /* !VALGRIND */
+
+ } else { /* need to read the key one byte at a time
*/
+ const uint8 *k = (const uint8 *)key;
+
+ /*--------------- all but the last block: affect some 32 bits of (a,b,c)
*/
+ while (length > 12)
+ {
+ a += ((uint32)k[0])<<24;
+ a += ((uint32)k[1])<<16;
+ a += ((uint32)k[2])<<8;
+ a += ((uint32)k[3]);
+ b += ((uint32)k[4])<<24;
+ b += ((uint32)k[5])<<16;
+ b += ((uint32)k[6])<<8;
+ b += ((uint32)k[7]);
+ c += ((uint32)k[8])<<24;
+ c += ((uint32)k[9])<<16;
+ c += ((uint32)k[10])<<8;
+ c += ((uint32)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)k[10])<<8;
+ case 10: c+=((uint32)k[9])<<16;
+ case 9 : c+=((uint32)k[8])<<24;
+ case 8 : b+=k[7];
+ case 7 : b+=((uint32)k[6])<<8;
+ case 6 : b+=((uint32)k[5])<<16;
+ case 5 : b+=((uint32)k[4])<<24;
+ case 4 : a+=k[3];
+ case 3 : a+=((uint32)k[2])<<8;
+ case 2 : a+=((uint32)k[1])<<16;
+ case 1 : a+=((uint32)k[0])<<24;
+ break;
+ case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing
*/
+ }
+ }
+
+ final(a,b,c);
+ *pc=c; *pb=b;
+ }
+
/*
* hash_any() -- hash a variable-length key into a 32-bit value
* k : the key (the unaligned variable-length array
of bytes)
***************
*** 239,298 ****
Datum
hash_any(register const unsigned char *k, register int keylen)
{
! register uint32 a,
! b,
! c,
! len;
!
! /* Set up the internal state */
! len = keylen;
! a = b = 0x9e3779b9; /* the golden ratio; an
arbitrary value */
! c = 3923095; /* initialize with an arbitrary
value */
!
! /* handle most of the key */
! while (len >= 12)
! {
! a += (k[0] + ((uint32) k[1] << 8) + ((uint32) k[2] << 16) +
((uint32) k[3] << 24));
! b += (k[4] + ((uint32) k[5] << 8) + ((uint32) k[6] << 16) +
((uint32) k[7] << 24));
! c += (k[8] + ((uint32) k[9] << 8) + ((uint32) k[10] << 16) +
((uint32) k[11] << 24));
! mix(a, b, c);
! k += 12;
! len -= 12;
! }
!
! /* handle the last 11 bytes */
! c += keylen;
! switch (len) /* all the case statements fall
through */
! {
! case 11:
! c += ((uint32) k[10] << 24);
! case 10:
! c += ((uint32) k[9] << 16);
! case 9:
! c += ((uint32) k[8] << 8);
! /* the first byte of c is reserved for the length */
! case 8:
! b += ((uint32) k[7] << 24);
! case 7:
! b += ((uint32) k[6] << 16);
! case 6:
! b += ((uint32) k[5] << 8);
! case 5:
! b += k[4];
! case 4:
! a += ((uint32) k[3] << 24);
! case 3:
! a += ((uint32) k[2] << 16);
! case 2:
! a += ((uint32) k[1] << 8);
! case 1:
! a += k[0];
! /* case 0: nothing left to add */
! }
! mix(a, b, c);
!
! /* report the result */
! return UInt32GetDatum(c);
}
/*
--- 1069,1079 ----
Datum
hash_any(register const unsigned char *k, register int keylen)
{
! #ifndef WORDS_BIGENDIAN
! return hashlittle(k, keylen, 3923095);
! #else
! return hashbig(k, keylen, 3923095);
! #endif
}
/*
***************
*** 305,316 ****
Datum
hash_uint32(uint32 k)
{
! register uint32 a,
! b,
! c;
! a = 0x9e3779b9 + k;
! b = 0x9e3779b9;
c = 3923095 + (uint32) sizeof(uint32);
mix(a, b, c);
--- 1086,1095 ----
Datum
hash_uint32(uint32 k)
{
! register uint32 a, b, c;
! a = 0xdeadbeef + k;
! b = 0xdeadbeef;
c = 3923095 + (uint32) sizeof(uint32);
mix(a, b, c);
---------------------------(end of broadcast)---------------------------
TIP 4: Have you searched our list archives?
http://archives.postgresql.org
