1//Copyright (c) 2011-2012 Mail.RU
2//Copyright (c) 2011-2012 Maksim Kalinchenko
3//Copyright (c) 2012 Sokolov Yura aka funny-falcon
4//
5//MIT License
6//
7//Permission is hereby granted, free of charge, to any person obtaining
8//a copy of this software and associated documentation files (the
9//"Software"), to deal in the Software without restriction, including
10//without limitation the rights to use, copy, modify, merge, publish,
11//distribute, sublicense, and/or sell copies of the Software, and to
12//permit persons to whom the Software is furnished to do so, subject to
13//the following conditions:
14//
15//The above copyright notice and this permission notice shall be
16//included in all copies or substantial portions of the Software.
17//
18//THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
19//EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20//MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
21//NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
22//LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
23//OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
24//WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25
26#include <stdexcept>
27
28
29#define L 0xFFFFFFFF
30
31static unsigned int L27_38[] = {L / 27, L / 28, L / 29, L / 30, L / 31, L / 32,
32 L / 33, L / 34, L / 35, L / 36, L / 37, L / 38,
33 L / 39, L / 40, L / 41, L / 42, L / 43, L / 44,
34 L / 45, L / 46, L / 47, L / 48, L / 49, L / 50,
35 L / 51, L / 52, L / 53, L / 54, L / 55, L / 56,
36 L / 57, L / 58, L / 59, L / 60, L / 61, L / 62
37 };
38static unsigned int LL27_38[] = {L/(26*27), L/(27*28), L/(28*29), L/(29*30), L/(30*31), L/(31*32),
39 L/(32*33), L/(33*34), L/(34*35), L/(35*36), L/(36*37), L/(37*38),
40 L/(38*39), L/(39*40), L/(40*41), L/(41*42), L/(42*43), L/(43*44),
41 L/(44*45), L/(45*46), L/(46*47), L/(47*48), L/(48*49), L/(49*50),
42 L/(50*51), L/(51*52), L/(52*53), L/(53*54), L/(54*55), L/(55*56),
43 L/(56*57), L/(57*58), L/(58*59), L/(59*60), L/(60*61), L/(61*62)
44 };
45
46unsigned int sumburConsistentHash(unsigned int hashed_int, unsigned int capacity)
47{
48 unsigned int h = hashed_int;
49 unsigned int capa = capacity;
50 unsigned int part, n, i, c;
51
52 if (capa == 0)
53 throw std::runtime_error("Sumbur is not applicable to empty cluster");
54
55 part = L / capa;
56
57 if (L - h < part) return 0;
58
59 n = 1;
60
61 do {
62 if (h >= L / 2) h -= L / 2;
63 else {
64 n = 2;
65 if (L / 2 - h < part) return 1;
66 }
67 if (capa == 2) return 1;
68
69#define curslice(i) (L / (i * (i - 1)))
70#define unroll(i) \
71 if (curslice(i) <= h) h -= curslice(i); \
72 else { \
73 h += curslice(i) * (i - n - 1); \
74 n = i; \
75 if (L / i - h < part) return n-1; \
76 } \
77 if (capa == i) return (n-1)
78
79 unroll(3); unroll(4); unroll(5);
80 unroll(6); unroll(7); unroll(8);
81 unroll(9); unroll(10); unroll(11);
82 unroll(12); unroll(13); unroll(14);
83 unroll(15); unroll(16); unroll(17);
84 unroll(18); unroll(19); unroll(20);
85 unroll(21); unroll(22); unroll(23);
86 unroll(24); unroll(25); unroll(26);
87
88 for (i = 27; i <= capa && i <= 62; i++) {
89 c = LL27_38[i-27];
90 if (c <= h) {
91 h -= c;
92 }
93 else {
94 h += c * (i - n - 1);
95 n = i;
96 if (L27_38[i-27] - h < part) return n-1;
97 }
98 }
99
100 for(i = 63; i <= capa; i++) {
101 c = L / (i * (i - 1));
102 if (c <= h) {
103 h -= c;
104 }
105 else {
106 h += c * (i - n - 1);
107 n = i;
108 if (L / i - h < part) return n - 1;
109 }
110 }
111 } while(0);
112 return n - 1;
113}
114