63 lines
2 KiB
C++
63 lines
2 KiB
C++
/*
|
|
Copyright (c) 2013 Microsoft Corporation. All rights reserved.
|
|
Released under Apache 2.0 license as described in the file LICENSE.
|
|
|
|
Author: Leonardo de Moura
|
|
*/
|
|
namespace lean {
|
|
|
|
void mix(unsigned & a, unsigned & b, unsigned & 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);
|
|
}
|
|
|
|
// Bob Jenkin's hash function.
|
|
// http://burtleburtle.net/bob/hash/doobs.html
|
|
unsigned hash_str(unsigned length, char const * str, 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 */
|
|
while (len >= 12) {
|
|
a += reinterpret_cast<unsigned const *>(str)[0];
|
|
b += reinterpret_cast<unsigned const *>(str)[1];
|
|
c += reinterpret_cast<unsigned const *>(str)[2];
|
|
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);
|
|
case 10: c+=((unsigned)str[9] << 16);
|
|
case 9 : c+=((unsigned)str[8] << 8);
|
|
/* the first byte of c is reserved for the length */
|
|
case 8 : b+=((unsigned)str[7] << 24);
|
|
case 7 : b+=((unsigned)str[6] << 16);
|
|
case 6 : b+=((unsigned)str[5] << 8);
|
|
case 5 : b+=str[4];
|
|
case 4 : a+=((unsigned)str[3] << 24);
|
|
case 3 : a+=((unsigned)str[2] << 16);
|
|
case 2 : a+=((unsigned)str[1] << 8);
|
|
case 1 : a+=str[0];
|
|
/* case 0: nothing left to add */
|
|
}
|
|
mix(a, b, c);
|
|
/*-------------------------------------------- report the result */
|
|
return c;
|
|
}
|
|
|
|
}
|