/* Last changed Time-stamp: <2013-07-02 15:32:58 mtw> */

/* hash_util.c */

#include <stdio.h>

#include <math.h>

#include <string.h>

#include <stdlib.h>

#include "config.h"

#include "utils.h"

#include "hash_util.h"

#define PRIVATE static

#define PUBLIC

static char UNUSED rcsid[] = "$Id: hash_util.c,v 1.9 2006/07/17 09:22:31 xtof Exp $";

/* modify hash_f(), hash_comp() and the typedef of hash_entry in hash_utils.h

to suit your application */

PUBLIC void * lookup_hash (void *x);

PUBLIC int write_hash (void *x);

PUBLIC void delete_hash (void *x);

PUBLIC void kill_hash();

PUBLIC void initialize_hash();

PUBLIC int hash_comp(void *x, void *y);

inline PRIVATE unsigned hash_f (void *x);

/* HASHBITS usually defined via configure and config.h */

#ifndef HASHBITS

#define HASHBITS 24

#endif

#define HASHSIZE (((unsigned long) 1<<HASHBITS)-1)

/* #define HASHSIZE 67108864 -1 */ /* 2^26 -1 must be power of 2 -1 */

/* #define HASHSIZE 33554432 -1 */ /* 2^25 -1 must be power of 2 -1 */

/* #define HASHSIZE 16777216 -1 */ /* 2^24 -1 must be power of 2 -1 */

/* #define HASHSIZE 4194304 -1 */ /* 2^22 -1 must be power of 2 -1 */

PRIVATE void *hashtab[HASHSIZE+1];

PUBLIC unsigned long collisions=0;

/* ----------------------------------------------------------------- */

/* stolen from perl source */

char coeff[] = {

61,59,53,47,43,41,37,31,29,23,17,13,11,7,3,1,

61,59,53,47,43,41,37,31,29,23,17,13,11,7,3,1,

61,59,53,47,43,41,37,31,29,23,17,13,11,7,3,1,

61,59,53,47,43,41,37,31,29,23,17,13,11,7,3,1,

61,59,53,47,43,41,37,31,29,23,17,13,11,7,3,1,

61,59,53,47,43,41,37,31,29,23,17,13,11,7,3,1,

61,59,53,47,43,41,37,31,29,23,17,13,11,7,3,1,

61,59,53,47,43,41,37,31,29,23,17,13,11,7,3,1};

/* key must not be longer than 128 */

inline

PRIVATE unsigned old_hash_f(void *x)

{

register char *s;

register int i;

register int hash;

s = ((hash_entry *)x)->structure;

for (i=0, hash = 0;

/* while */ *s;

s++, i++ , hash *= 5 ) {

hash += *s * coeff[i];

}

/* printf("%7d\t", hash); */

return ((hash) & (HASHSIZE)); /* modulo HASHSIZE for normalization */

}

PUBLIC int hash_comp(void *x, void *y) {

return strcmp(((hash_entry *)x)->structure, ((hash_entry *)y)->structure);

}

/* ----------------------------------------------------------------- */

PUBLIC void * lookup_hash (void *x) /* returns NULL unless x is in the hash */

{

unsigned int hashval;

hashval=hash_f(x);

/* xtof poset debug ! */

#ifdef _DEBUG_HASH_

fprintf(stderr,

"lookup %s => %d\n",

((hash_entry *)x)->structure,

hashval);

#endif

if (hashtab[hashval]==NULL) return NULL;

while (hashtab[hashval]){

if (hash_comp(x,hashtab[hashval])==0) return hashtab[hashval];

hashval = ((hashval+1) & (HASHSIZE));

}

return NULL;

}

/* ----------------------------------------------------------------- */

PUBLIC int write_hash (void *x) /* returns 1 if x already was in the hash */

{

unsigned int hashval;

hashval=hash_f(x);

#ifdef _DEBUG_HASH_

fprintf(stderr,

"write %s => %d\n",

((hash_entry *)x)->structure,

hashval);

#endif

while (hashtab[hashval]){

if (hash_comp(x,hashtab[hashval])==0) return 1;

hashval = ((hashval+1) & (HASHSIZE));

collisions++;

}

hashtab[hashval]=x;

return 0;

}

/* ----------------------------------------------------------------- */

PUBLIC void initialize_hash ()

{

}

/* ----------------------------------------------------------------- */

PUBLIC void kill_hash ()

{

unsigned int i;

for (i=0;i<HASHSIZE+1;i++) {

if (hashtab[i]) {

free (((hash_entry *)hashtab[i])->structure);

/*free (hashtab[i]);*/

hashtab[i]=NULL;

}

}

}

/* ----------------------------------------------------------------- */

PUBLIC void delete_hash (void *x) /* doesn't work in case of collsions */

{ /* doesn't free anything ! */

unsigned int hashval;

hashval=hash_f(x);

while (hashtab[hashval]){

if (hash_comp(x,hashtab[hashval])==0) {

hashtab[hashval]=NULL;

return;

}

hashval = ((hashval+1) & (HASHSIZE));

}

}

/* ----------------------------------------------------------------- */

/*

--------------------------------------------------------------------

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.)

mix() takes 36 machine instructions, but only 18 cycles on a superscalar

machine (like a Pentium or a Sparc). No faster mixer seems to work,

that's the result of my brute-force search. There were about 2^^68

hashes to choose from. I only tested about a billion of those.

--------------------------------------------------------------------

*/

#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() -- hash a variable-length key into a 32-bit value

k : the key (the unaligned variable-length array of bytes)

len : 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. Every 1-bit and 2-bit delta achieves avalanche.

About 6*len+35 instructions.

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 (char **)k, do it like this:

for (i=0, h=0; i<n; ++i) h = hash( k[i], len[i], h);

By Bob Jenkins, 1996. bob_jenkins@burtleburtle.net. You may use this

code any way you wish, private, educational, or commercial. It's free.

See http://burtleburtle.net/bob/hash/evahash.html

Use for hash table lookup, or anything where one collision in 2^^32 is

acceptable. Do NOT use for cryptographic purposes.

--------------------------------------------------------------------

*/

inline

PRIVATE unsigned hash_f(void *x)

{

register unsigned char *k; /* the key */

register unsigned length; /* the length of the key */

register unsigned initval=0; /* the previous hash, or an arbitrary value */

register unsigned a,b,c,len;

/* Set up the internal state */

k = ((hash_entry *)x)->structure;

len = length = (unsigned) strlen(k);

a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */

c = initval; /* the previous hash value */

/*---------------------------------------- handle most of the key */

while (len >= 12)

{

a += (k[0] +((unsigned)k[1]<<8) +((unsigned)k[2]<<16) +((unsigned)k[3]<<24));

b += (k[4] +((unsigned)k[5]<<8) +((unsigned)k[6]<<16) +((unsigned)k[7]<<24));

c += (k[8] +((unsigned)k[9]<<8) +((unsigned)k[10]<<16)+((unsigned)k[11]<<24));

mix(a,b,c);

k += 12; len -= 12;

}

/*------------------------------------- handle the last 11 bytes */

c += length;

switch(len) /* all the case statements fall through */

{

case 11: c+=((unsigned)k[10]<<24);

case 10: c+=((unsigned)k[9]<<16);

case 9 : c+=((unsigned)k[8]<<8);

/* the first byte of c is reserved for the length */

case 8 : b+=((unsigned)k[7]<<24);

case 7 : b+=((unsigned)k[6]<<16);

case 6 : b+=((unsigned)k[5]<<8);

case 5 : b+=k[4];

case 4 : a+=((unsigned)k[3]<<24);

case 3 : a+=((unsigned)k[2]<<16);

case 2 : a+=((unsigned)k[1]<<8);

case 1 : a+=k[0];

/* case 0: nothing left to add */

}

mix(a,b,c);

/*-------------------------------------------- report the result */

return (c & HASHSIZE);

}