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/*
* -------------------------------------------------------------------------------
* 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 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 SELF_TEST 1 */
#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 */
#ifdef linux
# include <endian.h> /* attempt to define endianness */
#endif
/*
* 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); \
}
/*
* --------------------------------------------------------------------
* This works on all machines. To be useful, it requires
* -- that the key be an array of uint32_t's, and
* -- that the length be the number of uint32_t'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 uint32_ts rather than in
* bytes. hashlittle() is more complicated than hashword() only because
* hashlittle() has to dance around fitting the key bytes into registers.
* --------------------------------------------------------------------
*/
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().
* --------------------------------------------------------------------
*/
void hashword2 (
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 *pc, /* IN: seed OUT: primary hash value */
uint32_t *pb) /* IN: more seed OUT: secondary hash value */
{
uint32_t a,b,c;
/* Set up the internal state */
a = b = c = 0xdeadbeef + ((uint32_t)(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_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 */
*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.
* -------------------------------------------------------------------------------
*/
uint32_t hashlittle( 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 (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0))
{
const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */
const uint8_t *k8;
/*------ 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 c; /* zero length strings require no mixing */
}
#else /* make valgrind happy */
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;
}
/*----------------------------- 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;
}
/*
* 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_t *pc, /* IN: primary initval, OUT: primary hash */
uint32_t *pb) /* IN: secondary initval, OUT: secondary hash */
{
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) + *pc;
c += *pb;
u.ptr = key;
if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0))
{
const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */
const uint8_t *k8;
/*------ 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_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 : *pc=c; *pb=b; return; /* zero length strings require no mixing */
}
#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;
}
/*----------------------------- 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 : *pc=c; *pb=b; return; /* 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 += 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 : *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.
*/
uint32_t hashbig( 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 (HASH_BIG_ENDIAN && ((u.i & 0x3) == 0))
{
const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */
const uint8_t *k8;
/*------ 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 c; /* zero length strings require no mixing */
}
#else /* make valgrind happy */
k8 = (const uint8_t *)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_t)k8[10])<<8; /* fall through */
case 10: c+=((uint32_t)k8[9])<<16; /* fall through */
case 9 : c+=((uint32_t)k8[8])<<24; /* fall through */
case 8 : b+=k[1]; a+=k[0]; break;
case 7 : b+=((uint32_t)k8[6])<<8; /* fall through */
case 6 : b+=((uint32_t)k8[5])<<16; /* fall through */
case 5 : b+=((uint32_t)k8[4])<<24; /* fall through */
case 4 : a+=k[0]; break;
case 3 : a+=((uint32_t)k8[2])<<8; /* fall through */
case 2 : a+=((uint32_t)k8[1])<<16; /* fall through */
case 1 : a+=((uint32_t)k8[0])<<24; break;
case 0 : return c;
}
#endif /* !VALGRIND */
}
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;
}
#ifdef SELF_TEST
/* used for timings */
void driver1()
{
uint8_t buf[256];
uint32_t i;
uint32_t h=0;
time_t a,z;
time(&a);
for (i=0; i<256; ++i)
buf[i] = 'x';
for (i=0; i<1; ++i)
h = hashlittle(&buf[0],1,h);
time(&z);
if (z-a > 0)
printf("time %d %.8x\n", z-a, h);
}
/* check that every input bit changes every output bit half the time */
#define HASHSTATE 1
#define HASHLEN 1
#define MAXPAIR 60
#define MAXLEN 70
void driver2()
{
uint8_t qa[MAXLEN+1], qb[MAXLEN+2], *a = &qa[0], *b = &qb[1];
uint32_t c[HASHSTATE], d[HASHSTATE], i=0, j=0, k, l, m=0, z;
uint32_t e[HASHSTATE],f[HASHSTATE],g[HASHSTATE],h[HASHSTATE];
uint32_t x[HASHSTATE],y[HASHSTATE];
uint32_t hlen;
printf("No more than %d trials should ever be needed \n",MAXPAIR/2);
for (hlen=0; hlen < MAXLEN; ++hlen)
{
z=0;
for (i=0; i<hlen; ++i) /*----------------------- for each input byte, */
{
for (j=0; j<8; ++j) /*------------------------ for each input bit, */
{
for (m=1; m<8; ++m) /*------------ for serveral possible initvals, */
{
for (l=0; l<HASHSTATE; ++l)
e[l]=f[l]=g[l]=h[l]=x[l]=y[l]=~((uint32_t)0);
/*---- check that every output bit is affected by that input bit */
for (k=0; k<MAXPAIR; k+=2)
{
uint32_t finished=1;
/* keys have one bit different */
for (l=0; l<hlen+1; ++l)
a[l] = b[l] = (uint8_t)0;
/* have a and b be two keys differing in only one bit */
a[i] ^= (k<<j);
a[i] ^= (k>>(8-j));
c[0] = hashlittle(a, hlen, m);
b[i] ^= ((k+1)<<j);
b[i] ^= ((k+1)>>(8-j));
d[0] = hashlittle(b, hlen, m);
/* check every bit is 1, 0, set, and not set at least once */
for (l=0; l<HASHSTATE; ++l)
{
e[l] &= (c[l]^d[l]);
f[l] &= ~(c[l]^d[l]);
g[l] &= c[l];
h[l] &= ~c[l];
x[l] &= d[l];
y[l] &= ~d[l];
if (e[l]|f[l]|g[l]|h[l]|x[l]|y[l]) finished=0;
}
if (finished) break;
}
if (k>z)
z=k;
if (k==MAXPAIR)
{
printf("Some bit didn't change: ");
printf("%.8x %.8x %.8x %.8x %.8x %.8x ", e[0],f[0],g[0],h[0],x[0],y[0]);
printf("i %d j %d m %d len %d\n", i, j, m, hlen);
}
if (z==MAXPAIR)
goto done;
}
}
}
done:
if (z < MAXPAIR)
{
printf("Mix success %2d bytes %2d initvals ",i,m);
printf("required %d trials\n", z/2);
}
}
printf("\n");
}
/* Check for reading beyond the end of the buffer and alignment problems */
void driver3()
{
uint8_t buf[MAXLEN+20], *b;
uint32_t len;
uint8_t q[] = "This is the time for all good men to come to the aid of their country...";
uint32_t h;
uint8_t qq[] = "xThis is the time for all good men to come to the aid of their country...";
uint32_t i;
uint8_t qqq[] = "xxThis is the time for all good men to come to the aid of their country...";
uint32_t j;
uint8_t qqqq[] = "xxxThis is the time for all good men to come to the aid of their country...";
uint32_t ref,x,y;
uint8_t *p;
printf("Endianness. These lines should all be the same (for values filled in):\n");
printf("%.8x %.8x %.8x\n",
hashword((const uint32_t *)q, (sizeof(q)-1)/4, 13),
hashword((const uint32_t *)q, (sizeof(q)-5)/4, 13),
hashword((const uint32_t *)q, (sizeof(q)-9)/4, 13));
p = q;
printf("%.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
hashlittle(p, sizeof(q)-1, 13), hashlittle(p, sizeof(q)-2, 13),
hashlittle(p, sizeof(q)-3, 13), hashlittle(p, sizeof(q)-4, 13),
hashlittle(p, sizeof(q)-5, 13), hashlittle(p, sizeof(q)-6, 13),
hashlittle(p, sizeof(q)-7, 13), hashlittle(p, sizeof(q)-8, 13),
hashlittle(p, sizeof(q)-9, 13), hashlittle(p, sizeof(q)-10, 13),
hashlittle(p, sizeof(q)-11, 13), hashlittle(p, sizeof(q)-12, 13));
p = &qq[1];
printf("%.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
hashlittle(p, sizeof(q)-1, 13), hashlittle(p, sizeof(q)-2, 13),
hashlittle(p, sizeof(q)-3, 13), hashlittle(p, sizeof(q)-4, 13),
hashlittle(p, sizeof(q)-5, 13), hashlittle(p, sizeof(q)-6, 13),
hashlittle(p, sizeof(q)-7, 13), hashlittle(p, sizeof(q)-8, 13),
hashlittle(p, sizeof(q)-9, 13), hashlittle(p, sizeof(q)-10, 13),
hashlittle(p, sizeof(q)-11, 13), hashlittle(p, sizeof(q)-12, 13));
p = &qqq[2];
printf("%.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
hashlittle(p, sizeof(q)-1, 13), hashlittle(p, sizeof(q)-2, 13),
hashlittle(p, sizeof(q)-3, 13), hashlittle(p, sizeof(q)-4, 13),
hashlittle(p, sizeof(q)-5, 13), hashlittle(p, sizeof(q)-6, 13),
hashlittle(p, sizeof(q)-7, 13), hashlittle(p, sizeof(q)-8, 13),
hashlittle(p, sizeof(q)-9, 13), hashlittle(p, sizeof(q)-10, 13),
hashlittle(p, sizeof(q)-11, 13), hashlittle(p, sizeof(q)-12, 13));
p = &qqqq[3];
printf("%.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
hashlittle(p, sizeof(q)-1, 13), hashlittle(p, sizeof(q)-2, 13),
hashlittle(p, sizeof(q)-3, 13), hashlittle(p, sizeof(q)-4, 13),
hashlittle(p, sizeof(q)-5, 13), hashlittle(p, sizeof(q)-6, 13),
hashlittle(p, sizeof(q)-7, 13), hashlittle(p, sizeof(q)-8, 13),
hashlittle(p, sizeof(q)-9, 13), hashlittle(p, sizeof(q)-10, 13),
hashlittle(p, sizeof(q)-11, 13), hashlittle(p, sizeof(q)-12, 13));
printf("\n");
/* check that hashlittle2 and hashlittle produce the same results */
i=47; j=0;
hashlittle2(q, sizeof(q), &i, &j);
if (hashlittle(q, sizeof(q), 47) != i)
printf("hashlittle2 and hashlittle mismatch\n");
/* check that hashword2 and hashword produce the same results */
len = 0xdeadbeef;
i=47, j=0;
hashword2(&len, 1, &i, &j);
if (hashword(&len, 1, 47) != i)
printf("hashword2 and hashword mismatch %x %x\n",
i, hashword(&len, 1, 47));
/* check hashlittle doesn't read before or after the ends of the string */
for (h=0, b=buf+1; h<8; ++h, ++b)
{
for (i=0; i<MAXLEN; ++i)
{
len = i;
for (j=0; j<i; ++j) *(b+j)=0;
/* these should all be equal */
ref = hashlittle(b, len, (uint32_t)1);
*(b+i)=(uint8_t)~0;
*(b-1)=(uint8_t)~0;
x = hashlittle(b, len, (uint32_t)1);
y = hashlittle(b, len, (uint32_t)1);
if ((ref != x) || (ref != y))
{
printf("alignment error: %.8x %.8x %.8x %d %d\n",ref,x,y,
h, i);
}
}
}
}
/* check for problems with nulls */
void driver4()
{
uint8_t buf[1];
uint32_t h,i,state[HASHSTATE];
buf[0] = ~0;
for (i=0; i<HASHSTATE; ++i) state[i] = 1;
printf("These should all be different\n");
for (i=0, h=0; i<8; ++i)
{
h = hashlittle(buf, 0, h);
printf("%2ld 0-byte strings, hash is %.8x\n", i, h);
}
}
void driver5()
{
uint32_t b,c;
b=0, c=0, hashlittle2("", 0, &c, &b);
printf("hash is %.8lx %.8lx\n", c, b); /* deadbeef deadbeef */
b=0xdeadbeef, c=0, hashlittle2("", 0, &c, &b);
printf("hash is %.8lx %.8lx\n", c, b); /* bd5b7dde deadbeef */
b=0xdeadbeef, c=0xdeadbeef, hashlittle2("", 0, &c, &b);
printf("hash is %.8lx %.8lx\n", c, b); /* 9c093ccd bd5b7dde */
b=0, c=0, hashlittle2("Four score and seven years ago", 30, &c, &b);
printf("hash is %.8lx %.8lx\n", c, b); /* 17770551 ce7226e6 */
b=1, c=0, hashlittle2("Four score and seven years ago", 30, &c, &b);
printf("hash is %.8lx %.8lx\n", c, b); /* e3607cae bd371de4 */
b=0, c=1, hashlittle2("Four score and seven years ago", 30, &c, &b);
printf("hash is %.8lx %.8lx\n", c, b); /* cd628161 6cbea4b3 */
c = hashlittle("Four score and seven years ago", 30, 0);
printf("hash is %.8lx\n", c); /* 17770551 */
c = hashlittle("Four score and seven years ago", 30, 1);
printf("hash is %.8lx\n", c); /* cd628161 */
}
int main()
{
driver1(); /* test that the key is hashed: used for timings */
driver2(); /* test that whole key is hashed thoroughly */
driver3(); /* test that nothing but the key is hashed */
driver4(); /* test hashing multiple buffers (all buffers are null) */
driver5(); /* test the hash against known vectors */
return 1;
}
#endif /* SELF_TEST */
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