1/*
2 * Copyright 2017-present Facebook, Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17// This is version 2 of SpookyHash, incompatible with version 1.
18//
19// SpookyHash: a 128-bit noncryptographic hash function
20// By Bob Jenkins, public domain
21// Oct 31 2010: alpha, framework + SpookyHash::Mix appears right
22// Oct 31 2011: alpha again, Mix only good to 2^^69 but rest appears right
23// Dec 31 2011: beta, improved Mix, tested it for 2-bit deltas
24// Feb 2 2012: production, same bits as beta
25// Feb 5 2012: adjusted definitions of uint* to be more portable
26// Mar 30 2012: 3 bytes/cycle, not 4. Alpha was 4 but wasn't thorough enough.
27// August 5 2012: SpookyV2 (different results)
28//
29// Up to 3 bytes/cycle for long messages. Reasonably fast for short messages.
30// All 1 or 2 bit deltas achieve avalanche within 1% bias per output bit.
31//
32// This was developed for and tested on 64-bit x86-compatible processors.
33// It assumes the processor is little-endian. There is a macro
34// controlling whether unaligned reads are allowed (by default they are).
35// This should be an equally good hash on big-endian machines, but it will
36// compute different results on them than on little-endian machines.
37//
38// Google's CityHash has similar specs to SpookyHash, and CityHash is faster
39// on new Intel boxes. MD4 and MD5 also have similar specs, but they are orders
40// of magnitude slower. CRCs are two or more times slower, but unlike
41// SpookyHash, they have nice math for combining the CRCs of pieces to form
42// the CRCs of wholes. There are also cryptographic hashes, but those are even
43// slower than MD5.
44//
45
46#pragma once
47
48#include <cstddef>
49#include <cstdint>
50
51namespace folly {
52namespace hash {
53
54// clang-format off
55
56class SpookyHashV2
57{
58public:
59 //
60 // SpookyHash: hash a single message in one call, produce 128-bit output
61 //
62 static void Hash128(
63 const void *message, // message to hash
64 size_t length, // length of message in bytes
65 uint64_t *hash1, // in/out: in seed 1, out hash value 1
66 uint64_t *hash2); // in/out: in seed 2, out hash value 2
67
68 //
69 // Hash64: hash a single message in one call, return 64-bit output
70 //
71 static uint64_t Hash64(
72 const void *message, // message to hash
73 size_t length, // length of message in bytes
74 uint64_t seed) // seed
75 {
76 uint64_t hash1 = seed;
77 Hash128(message, length, &hash1, &seed);
78 return hash1;
79 }
80
81 //
82 // Hash32: hash a single message in one call, produce 32-bit output
83 //
84 static uint32_t Hash32(
85 const void *message, // message to hash
86 size_t length, // length of message in bytes
87 uint32_t seed) // seed
88 {
89 uint64_t hash1 = seed, hash2 = seed;
90 Hash128(message, length, &hash1, &hash2);
91 return (uint32_t)hash1;
92 }
93
94 //
95 // Init: initialize the context of a SpookyHash
96 //
97 void Init(
98 uint64_t seed1, // any 64-bit value will do, including 0
99 uint64_t seed2); // different seeds produce independent hashes
100
101 //
102 // Update: add a piece of a message to a SpookyHash state
103 //
104 void Update(
105 const void *message, // message fragment
106 size_t length); // length of message fragment in bytes
107
108
109 //
110 // Final: compute the hash for the current SpookyHash state
111 //
112 // This does not modify the state; you can keep updating it afterward
113 //
114 // The result is the same as if SpookyHash() had been called with
115 // all the pieces concatenated into one message.
116 //
117 void Final(
118 uint64_t *hash1, // out only: first 64 bits of hash value.
119 uint64_t *hash2) const; // out only: second 64 bits of hash value.
120
121 //
122 // left rotate a 64-bit value by k bytes
123 //
124 static inline uint64_t Rot64(uint64_t x, int k)
125 {
126 return (x << k) | (x >> (64 - k));
127 }
128
129 //
130 // This is used if the input is 96 bytes long or longer.
131 //
132 // The internal state is fully overwritten every 96 bytes.
133 // Every input bit appears to cause at least 128 bits of entropy
134 // before 96 other bytes are combined, when run forward or backward
135 // For every input bit,
136 // Two inputs differing in just that input bit
137 // Where "differ" means xor or subtraction
138 // And the base value is random
139 // When run forward or backwards one Mix
140 // I tried 3 pairs of each; they all differed by at least 212 bits.
141 //
142 static inline void Mix(
143 const uint64_t *data,
144 uint64_t &s0, uint64_t &s1, uint64_t &s2, uint64_t &s3,
145 uint64_t &s4, uint64_t &s5, uint64_t &s6, uint64_t &s7,
146 uint64_t &s8, uint64_t &s9, uint64_t &s10,uint64_t &s11)
147 {
148 s0 += data[0]; s2 ^= s10; s11 ^= s0; s0 = Rot64(s0,11); s11 += s1;
149 s1 += data[1]; s3 ^= s11; s0 ^= s1; s1 = Rot64(s1,32); s0 += s2;
150 s2 += data[2]; s4 ^= s0; s1 ^= s2; s2 = Rot64(s2,43); s1 += s3;
151 s3 += data[3]; s5 ^= s1; s2 ^= s3; s3 = Rot64(s3,31); s2 += s4;
152 s4 += data[4]; s6 ^= s2; s3 ^= s4; s4 = Rot64(s4,17); s3 += s5;
153 s5 += data[5]; s7 ^= s3; s4 ^= s5; s5 = Rot64(s5,28); s4 += s6;
154 s6 += data[6]; s8 ^= s4; s5 ^= s6; s6 = Rot64(s6,39); s5 += s7;
155 s7 += data[7]; s9 ^= s5; s6 ^= s7; s7 = Rot64(s7,57); s6 += s8;
156 s8 += data[8]; s10 ^= s6; s7 ^= s8; s8 = Rot64(s8,55); s7 += s9;
157 s9 += data[9]; s11 ^= s7; s8 ^= s9; s9 = Rot64(s9,54); s8 += s10;
158 s10 += data[10]; s0 ^= s8; s9 ^= s10; s10 = Rot64(s10,22); s9 += s11;
159 s11 += data[11]; s1 ^= s9; s10 ^= s11; s11 = Rot64(s11,46); s10 += s0;
160 }
161
162 //
163 // Mix all 12 inputs together so that h0, h1 are a hash of them all.
164 //
165 // For two inputs differing in just the input bits
166 // Where "differ" means xor or subtraction
167 // And the base value is random, or a counting value starting at that bit
168 // The final result will have each bit of h0, h1 flip
169 // For every input bit,
170 // with probability 50 +- .3%
171 // For every pair of input bits,
172 // with probability 50 +- 3%
173 //
174 // This does not rely on the last Mix() call having already mixed some.
175 // Two iterations was almost good enough for a 64-bit result, but a
176 // 128-bit result is reported, so End() does three iterations.
177 //
178 static inline void EndPartial(
179 uint64_t &h0, uint64_t &h1, uint64_t &h2, uint64_t &h3,
180 uint64_t &h4, uint64_t &h5, uint64_t &h6, uint64_t &h7,
181 uint64_t &h8, uint64_t &h9, uint64_t &h10,uint64_t &h11)
182 {
183 h11+= h1; h2 ^= h11; h1 = Rot64(h1,44);
184 h0 += h2; h3 ^= h0; h2 = Rot64(h2,15);
185 h1 += h3; h4 ^= h1; h3 = Rot64(h3,34);
186 h2 += h4; h5 ^= h2; h4 = Rot64(h4,21);
187 h3 += h5; h6 ^= h3; h5 = Rot64(h5,38);
188 h4 += h6; h7 ^= h4; h6 = Rot64(h6,33);
189 h5 += h7; h8 ^= h5; h7 = Rot64(h7,10);
190 h6 += h8; h9 ^= h6; h8 = Rot64(h8,13);
191 h7 += h9; h10^= h7; h9 = Rot64(h9,38);
192 h8 += h10; h11^= h8; h10= Rot64(h10,53);
193 h9 += h11; h0 ^= h9; h11= Rot64(h11,42);
194 h10+= h0; h1 ^= h10; h0 = Rot64(h0,54);
195 }
196
197 static inline void End(
198 const uint64_t *data,
199 uint64_t &h0, uint64_t &h1, uint64_t &h2, uint64_t &h3,
200 uint64_t &h4, uint64_t &h5, uint64_t &h6, uint64_t &h7,
201 uint64_t &h8, uint64_t &h9, uint64_t &h10,uint64_t &h11)
202 {
203 h0 += data[0]; h1 += data[1]; h2 += data[2]; h3 += data[3];
204 h4 += data[4]; h5 += data[5]; h6 += data[6]; h7 += data[7];
205 h8 += data[8]; h9 += data[9]; h10 += data[10]; h11 += data[11];
206 EndPartial(h0,h1,h2,h3,h4,h5,h6,h7,h8,h9,h10,h11);
207 EndPartial(h0,h1,h2,h3,h4,h5,h6,h7,h8,h9,h10,h11);
208 EndPartial(h0,h1,h2,h3,h4,h5,h6,h7,h8,h9,h10,h11);
209 }
210
211 //
212 // The goal is for each bit of the input to expand into 128 bits of
213 // apparent entropy before it is fully overwritten.
214 // n trials both set and cleared at least m bits of h0 h1 h2 h3
215 // n: 2 m: 29
216 // n: 3 m: 46
217 // n: 4 m: 57
218 // n: 5 m: 107
219 // n: 6 m: 146
220 // n: 7 m: 152
221 // when run forwards or backwards
222 // for all 1-bit and 2-bit diffs
223 // with diffs defined by either xor or subtraction
224 // with a base of all zeros plus a counter, or plus another bit, or random
225 //
226 static inline void ShortMix(uint64_t &h0, uint64_t &h1,
227 uint64_t &h2, uint64_t &h3)
228 {
229 h2 = Rot64(h2,50); h2 += h3; h0 ^= h2;
230 h3 = Rot64(h3,52); h3 += h0; h1 ^= h3;
231 h0 = Rot64(h0,30); h0 += h1; h2 ^= h0;
232 h1 = Rot64(h1,41); h1 += h2; h3 ^= h1;
233 h2 = Rot64(h2,54); h2 += h3; h0 ^= h2;
234 h3 = Rot64(h3,48); h3 += h0; h1 ^= h3;
235 h0 = Rot64(h0,38); h0 += h1; h2 ^= h0;
236 h1 = Rot64(h1,37); h1 += h2; h3 ^= h1;
237 h2 = Rot64(h2,62); h2 += h3; h0 ^= h2;
238 h3 = Rot64(h3,34); h3 += h0; h1 ^= h3;
239 h0 = Rot64(h0,5); h0 += h1; h2 ^= h0;
240 h1 = Rot64(h1,36); h1 += h2; h3 ^= h1;
241 }
242
243 //
244 // Mix all 4 inputs together so that h0, h1 are a hash of them all.
245 //
246 // For two inputs differing in just the input bits
247 // Where "differ" means xor or subtraction
248 // And the base value is random, or a counting value starting at that bit
249 // The final result will have each bit of h0, h1 flip
250 // For every input bit,
251 // with probability 50 +- .3% (it is probably better than that)
252 // For every pair of input bits,
253 // with probability 50 +- .75% (the worst case is approximately that)
254 //
255 static inline void ShortEnd(uint64_t &h0, uint64_t &h1,
256 uint64_t &h2, uint64_t &h3)
257 {
258 h3 ^= h2; h2 = Rot64(h2,15); h3 += h2;
259 h0 ^= h3; h3 = Rot64(h3,52); h0 += h3;
260 h1 ^= h0; h0 = Rot64(h0,26); h1 += h0;
261 h2 ^= h1; h1 = Rot64(h1,51); h2 += h1;
262 h3 ^= h2; h2 = Rot64(h2,28); h3 += h2;
263 h0 ^= h3; h3 = Rot64(h3,9); h0 += h3;
264 h1 ^= h0; h0 = Rot64(h0,47); h1 += h0;
265 h2 ^= h1; h1 = Rot64(h1,54); h2 += h1;
266 h3 ^= h2; h2 = Rot64(h2,32); h3 += h2;
267 h0 ^= h3; h3 = Rot64(h3,25); h0 += h3;
268 h1 ^= h0; h0 = Rot64(h0,63); h1 += h0;
269 }
270
271private:
272
273 //
274 // Short is used for messages under 192 bytes in length
275 // Short has a low startup cost, the normal mode is good for long
276 // keys, the cost crossover is at about 192 bytes. The two modes were
277 // held to the same quality bar.
278 //
279 static void Short(
280 const void *message, // message (byte array, not necessarily aligned)
281 size_t length, // length of message (in bytes)
282 uint64_t *hash1, // in/out: in the seed, out the hash value
283 uint64_t *hash2); // in/out: in the seed, out the hash value
284
285 // number of uint64_t's in internal state
286 static constexpr size_t sc_numVars = 12;
287
288 // size of the internal state
289 static constexpr size_t sc_blockSize = sc_numVars*8;
290
291 // size of buffer of unhashed data, in bytes
292 static constexpr size_t sc_bufSize = 2*sc_blockSize;
293
294 //
295 // sc_const: a constant which:
296 // * is not zero
297 // * is odd
298 // * is a not-very-regular mix of 1's and 0's
299 // * does not need any other special mathematical properties
300 //
301 static constexpr uint64_t sc_const = 0xdeadbeefdeadbeefULL;
302
303 uint64_t m_data[2*sc_numVars]; // unhashed data, for partial messages
304 uint64_t m_state[sc_numVars]; // internal state of the hash
305 size_t m_length; // total length of the input so far
306 uint8_t m_remainder; // length of unhashed data stashed in m_data
307};
308
309// clang-format on
310
311} // namespace hash
312} // namespace folly
313