mirror of
https://github.com/Z3Prover/z3
synced 2025-04-08 18:31:49 +00:00
94 lines
2.1 KiB
C++
94 lines
2.1 KiB
C++
/*++
|
|
Copyright (c) 2006 Microsoft Corporation
|
|
|
|
Module Name:
|
|
|
|
hash.cpp
|
|
|
|
Abstract:
|
|
|
|
Basic hash computation support.
|
|
|
|
Author:
|
|
|
|
Leonardo de Moura (leonardo) 2006-09-11.
|
|
|
|
Revision History:
|
|
|
|
--*/
|
|
|
|
#include"debug.h"
|
|
#include"hash.h"
|
|
#include <string.h>
|
|
|
|
static unsigned read_unsigned(const char *s) {
|
|
unsigned n;
|
|
memcpy(&n, s, sizeof(unsigned));
|
|
return n;
|
|
}
|
|
|
|
// I'm using Bob Jenkin's hash function.
|
|
// http://burtleburtle.net/bob/hash/doobs.html
|
|
unsigned string_hash(const char * str, unsigned length, unsigned init_value) {
|
|
unsigned a, b, c, len;
|
|
|
|
/* Set up the internal state */
|
|
len = length;
|
|
a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */
|
|
c = init_value; /* the previous hash value */
|
|
|
|
/*---------------------------------------- handle most of the key */
|
|
SASSERT(sizeof(unsigned) == 4);
|
|
while (len >= 12) {
|
|
a += read_unsigned(str);
|
|
b += read_unsigned(str+4);
|
|
c += read_unsigned(str+8);
|
|
mix(a,b,c);
|
|
str += 12; len -= 12;
|
|
}
|
|
|
|
/*------------------------------------- handle the last 11 bytes */
|
|
c += length;
|
|
switch(len) { /* all the case statements fall through */
|
|
case 11:
|
|
c+=((unsigned)str[10]<<24);
|
|
Z3_fallthrough;
|
|
case 10:
|
|
c+=((unsigned)str[9]<<16);
|
|
Z3_fallthrough;
|
|
case 9 :
|
|
c+=((unsigned)str[8]<<8);
|
|
Z3_fallthrough;
|
|
/* the first byte of c is reserved for the length */
|
|
case 8 :
|
|
b+=((unsigned)str[7]<<24);
|
|
Z3_fallthrough;
|
|
case 7 :
|
|
b+=((unsigned)str[6]<<16);
|
|
Z3_fallthrough;
|
|
case 6 :
|
|
b+=((unsigned)str[5]<<8);
|
|
Z3_fallthrough;
|
|
case 5 :
|
|
b+=str[4];
|
|
Z3_fallthrough;
|
|
case 4 :
|
|
a+=((unsigned)str[3]<<24);
|
|
Z3_fallthrough;
|
|
case 3 :
|
|
a+=((unsigned)str[2]<<16);
|
|
Z3_fallthrough;
|
|
case 2 :
|
|
a+=((unsigned)str[1]<<8);
|
|
Z3_fallthrough;
|
|
case 1 :
|
|
a+=str[0];
|
|
/* case 0: nothing left to add */
|
|
break;
|
|
}
|
|
mix(a,b,c);
|
|
/*-------------------------------------------- report the result */
|
|
return c;
|
|
}
|
|
|