1// lookup3 by Bob Jekins, code is public domain.
2
3#include "Platform.h"
4
5#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
6
7#define mix(a,b,c) \
8{ \
9  a -= c;  a ^= rot(c, 4);  c += b; \
10  b -= a;  b ^= rot(a, 6);  a += c; \
11  c -= b;  c ^= rot(b, 8);  b += a; \
12  a -= c;  a ^= rot(c,16);  c += b; \
13  b -= a;  b ^= rot(a,19);  a += c; \
14  c -= b;  c ^= rot(b, 4);  b += a; \
15}
16
17#define final(a,b,c) \
18{ \
19  c ^= b; c -= rot(b,14); \
20  a ^= c; a -= rot(c,11); \
21  b ^= a; b -= rot(a,25); \
22  c ^= b; c -= rot(b,16); \
23  a ^= c; a -= rot(c,4);  \
24  b ^= a; b -= rot(a,14); \
25  c ^= b; c -= rot(b,24); \
26}
27
28uint32_t lookup3 ( const void * key, int length, uint32_t initval )
29{
30  uint32_t a,b,c;                                          /* internal state */
31
32  a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;
33
34  const uint32_t *k = (const uint32_t *)key;         /* read 32-bit chunks */
35
36  /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
37  while (length > 12)
38  {
39    a += k[0];
40    b += k[1];
41    c += k[2];
42    mix(a,b,c);
43    length -= 12;
44    k += 3;
45  }
46
47  switch(length)
48  {
49    case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
50    case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
51    case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
52    case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
53    case 8 : b+=k[1]; a+=k[0]; break;
54    case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
55    case 6 : b+=k[1]&0xffff; a+=k[0]; break;
56    case 5 : b+=k[1]&0xff; a+=k[0]; break;
57    case 4 : a+=k[0]; break;
58    case 3 : a+=k[0]&0xffffff; break;
59    case 2 : a+=k[0]&0xffff; break;
60    case 1 : a+=k[0]&0xff; break;
61    case 0 : { return c; }              /* zero length strings require no mixing */
62  }
63
64  final(a,b,c);
65
66  return c;
67}
68
69void lookup3_test ( const void * key, int len, uint32_t seed, void * out )
70{
71  *(uint32_t*)out = lookup3(key,len,seed);
72}
73