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/*
* Copyright 2015 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// This is version 2 of SpookyHash, incompatible with version 1.
//
// SpookyHash: a 128-bit noncryptographic hash function
// By Bob Jenkins, public domain
// Oct 31 2010: alpha, framework + SpookyHash::Mix appears right
// Oct 31 2011: alpha again, Mix only good to 2^^69 but rest appears right
// Dec 31 2011: beta, improved Mix, tested it for 2-bit deltas
// Feb 2 2012: production, same bits as beta
// Feb 5 2012: adjusted definitions of uint* to be more portable
// Mar 30 2012: 3 bytes/cycle, not 4. Alpha was 4 but wasn't thorough enough.
// August 5 2012: SpookyV2 (different results)
//
// Up to 3 bytes/cycle for long messages. Reasonably fast for short messages.
// All 1 or 2 bit deltas achieve avalanche within 1% bias per output bit.
//
// This was developed for and tested on 64-bit x86-compatible processors.
// It assumes the processor is little-endian. There is a macro
// controlling whether unaligned reads are allowed (by default they are).
// This should be an equally good hash on big-endian machines, but it will
// compute different results on them than on little-endian machines.
//
// Google's CityHash has similar specs to SpookyHash, and CityHash is faster
// on new Intel boxes. MD4 and MD5 also have similar specs, but they are orders
// of magnitude slower. CRCs are two or more times slower, but unlike
// SpookyHash, they have nice math for combining the CRCs of pieces to form
// the CRCs of wholes. There are also cryptographic hashes, but those are even
// slower than MD5.
//
#ifndef FOLLY_SPOOKYHASHV2_H_
#define FOLLY_SPOOKYHASHV2_H_
#include <cstddef>
#include <cstdint>
namespace folly {
namespace hash {
class SpookyHashV2
{
public:
//
// SpookyHash: hash a single message in one call, produce 128-bit output
//
static void Hash128(
const void *message, // message to hash
size_t length, // length of message in bytes
uint64_t *hash1, // in/out: in seed 1, out hash value 1
uint64_t *hash2); // in/out: in seed 2, out hash value 2
//
// Hash64: hash a single message in one call, return 64-bit output
//
static uint64_t Hash64(
const void *message, // message to hash
size_t length, // length of message in bytes
uint64_t seed) // seed
{
uint64_t hash1 = seed;
Hash128(message, length, &hash1, &seed);
return hash1;
}
//
// Hash32: hash a single message in one call, produce 32-bit output
//
static uint32_t Hash32(
const void *message, // message to hash
size_t length, // length of message in bytes
uint32_t seed) // seed
{
uint64_t hash1 = seed, hash2 = seed;
Hash128(message, length, &hash1, &hash2);
return (uint32_t)hash1;
}
//
// Init: initialize the context of a SpookyHash
//
void Init(
uint64_t seed1, // any 64-bit value will do, including 0
uint64_t seed2); // different seeds produce independent hashes
//
// Update: add a piece of a message to a SpookyHash state
//
void Update(
const void *message, // message fragment
size_t length); // length of message fragment in bytes
//
// Final: compute the hash for the current SpookyHash state
//
// This does not modify the state; you can keep updating it afterward
//
// The result is the same as if SpookyHash() had been called with
// all the pieces concatenated into one message.
//
void Final(
uint64_t *hash1, // out only: first 64 bits of hash value.
uint64_t *hash2); // out only: second 64 bits of hash value.
//
// left rotate a 64-bit value by k bytes
//
static inline uint64_t Rot64(uint64_t x, int k)
{
return (x << k) | (x >> (64 - k));
}
//
// This is used if the input is 96 bytes long or longer.
//
// The internal state is fully overwritten every 96 bytes.
// Every input bit appears to cause at least 128 bits of entropy
// before 96 other bytes are combined, when run forward or backward
// For every input bit,
// Two inputs differing in just that input bit
// Where "differ" means xor or subtraction
// And the base value is random
// When run forward or backwards one Mix
// I tried 3 pairs of each; they all differed by at least 212 bits.
//
static inline void Mix(
const uint64_t *data,
uint64_t &s0, uint64_t &s1, uint64_t &s2, uint64_t &s3,
uint64_t &s4, uint64_t &s5, uint64_t &s6, uint64_t &s7,
uint64_t &s8, uint64_t &s9, uint64_t &s10,uint64_t &s11)
{
s0 += data[0]; s2 ^= s10; s11 ^= s0; s0 = Rot64(s0,11); s11 += s1;
s1 += data[1]; s3 ^= s11; s0 ^= s1; s1 = Rot64(s1,32); s0 += s2;
s2 += data[2]; s4 ^= s0; s1 ^= s2; s2 = Rot64(s2,43); s1 += s3;
s3 += data[3]; s5 ^= s1; s2 ^= s3; s3 = Rot64(s3,31); s2 += s4;
s4 += data[4]; s6 ^= s2; s3 ^= s4; s4 = Rot64(s4,17); s3 += s5;
s5 += data[5]; s7 ^= s3; s4 ^= s5; s5 = Rot64(s5,28); s4 += s6;
s6 += data[6]; s8 ^= s4; s5 ^= s6; s6 = Rot64(s6,39); s5 += s7;
s7 += data[7]; s9 ^= s5; s6 ^= s7; s7 = Rot64(s7,57); s6 += s8;
s8 += data[8]; s10 ^= s6; s7 ^= s8; s8 = Rot64(s8,55); s7 += s9;
s9 += data[9]; s11 ^= s7; s8 ^= s9; s9 = Rot64(s9,54); s8 += s10;
s10 += data[10]; s0 ^= s8; s9 ^= s10; s10 = Rot64(s10,22); s9 += s11;
s11 += data[11]; s1 ^= s9; s10 ^= s11; s11 = Rot64(s11,46); s10 += s0;
}
//
// Mix all 12 inputs together so that h0, h1 are a hash of them all.
//
// For two inputs differing in just the input bits
// Where "differ" means xor or subtraction
// And the base value is random, or a counting value starting at that bit
// The final result will have each bit of h0, h1 flip
// For every input bit,
// with probability 50 +- .3%
// For every pair of input bits,
// with probability 50 +- 3%
//
// This does not rely on the last Mix() call having already mixed some.
// Two iterations was almost good enough for a 64-bit result, but a
// 128-bit result is reported, so End() does three iterations.
//
static inline void EndPartial(
uint64_t &h0, uint64_t &h1, uint64_t &h2, uint64_t &h3,
uint64_t &h4, uint64_t &h5, uint64_t &h6, uint64_t &h7,
uint64_t &h8, uint64_t &h9, uint64_t &h10,uint64_t &h11)
{
h11+= h1; h2 ^= h11; h1 = Rot64(h1,44);
h0 += h2; h3 ^= h0; h2 = Rot64(h2,15);
h1 += h3; h4 ^= h1; h3 = Rot64(h3,34);
h2 += h4; h5 ^= h2; h4 = Rot64(h4,21);
h3 += h5; h6 ^= h3; h5 = Rot64(h5,38);
h4 += h6; h7 ^= h4; h6 = Rot64(h6,33);
h5 += h7; h8 ^= h5; h7 = Rot64(h7,10);
h6 += h8; h9 ^= h6; h8 = Rot64(h8,13);
h7 += h9; h10^= h7; h9 = Rot64(h9,38);
h8 += h10; h11^= h8; h10= Rot64(h10,53);
h9 += h11; h0 ^= h9; h11= Rot64(h11,42);
h10+= h0; h1 ^= h10; h0 = Rot64(h0,54);
}
static inline void End(
const uint64_t *data,
uint64_t &h0, uint64_t &h1, uint64_t &h2, uint64_t &h3,
uint64_t &h4, uint64_t &h5, uint64_t &h6, uint64_t &h7,
uint64_t &h8, uint64_t &h9, uint64_t &h10,uint64_t &h11)
{
h0 += data[0]; h1 += data[1]; h2 += data[2]; h3 += data[3];
h4 += data[4]; h5 += data[5]; h6 += data[6]; h7 += data[7];
h8 += data[8]; h9 += data[9]; h10 += data[10]; h11 += data[11];
EndPartial(h0,h1,h2,h3,h4,h5,h6,h7,h8,h9,h10,h11);
EndPartial(h0,h1,h2,h3,h4,h5,h6,h7,h8,h9,h10,h11);
EndPartial(h0,h1,h2,h3,h4,h5,h6,h7,h8,h9,h10,h11);
}
//
// The goal is for each bit of the input to expand into 128 bits of
// apparent entropy before it is fully overwritten.
// n trials both set and cleared at least m bits of h0 h1 h2 h3
// n: 2 m: 29
// n: 3 m: 46
// n: 4 m: 57
// n: 5 m: 107
// n: 6 m: 146
// n: 7 m: 152
// when run forwards or backwards
// for all 1-bit and 2-bit diffs
// with diffs defined by either xor or subtraction
// with a base of all zeros plus a counter, or plus another bit, or random
//
static inline void ShortMix(uint64_t &h0, uint64_t &h1,
uint64_t &h2, uint64_t &h3)
{
h2 = Rot64(h2,50); h2 += h3; h0 ^= h2;
h3 = Rot64(h3,52); h3 += h0; h1 ^= h3;
h0 = Rot64(h0,30); h0 += h1; h2 ^= h0;
h1 = Rot64(h1,41); h1 += h2; h3 ^= h1;
h2 = Rot64(h2,54); h2 += h3; h0 ^= h2;
h3 = Rot64(h3,48); h3 += h0; h1 ^= h3;
h0 = Rot64(h0,38); h0 += h1; h2 ^= h0;
h1 = Rot64(h1,37); h1 += h2; h3 ^= h1;
h2 = Rot64(h2,62); h2 += h3; h0 ^= h2;
h3 = Rot64(h3,34); h3 += h0; h1 ^= h3;
h0 = Rot64(h0,5); h0 += h1; h2 ^= h0;
h1 = Rot64(h1,36); h1 += h2; h3 ^= h1;
}
//
// Mix all 4 inputs together so that h0, h1 are a hash of them all.
//
// For two inputs differing in just the input bits
// Where "differ" means xor or subtraction
// And the base value is random, or a counting value starting at that bit
// The final result will have each bit of h0, h1 flip
// For every input bit,
// with probability 50 +- .3% (it is probably better than that)
// For every pair of input bits,
// with probability 50 +- .75% (the worst case is approximately that)
//
static inline void ShortEnd(uint64_t &h0, uint64_t &h1,
uint64_t &h2, uint64_t &h3)
{
h3 ^= h2; h2 = Rot64(h2,15); h3 += h2;
h0 ^= h3; h3 = Rot64(h3,52); h0 += h3;
h1 ^= h0; h0 = Rot64(h0,26); h1 += h0;
h2 ^= h1; h1 = Rot64(h1,51); h2 += h1;
h3 ^= h2; h2 = Rot64(h2,28); h3 += h2;
h0 ^= h3; h3 = Rot64(h3,9); h0 += h3;
h1 ^= h0; h0 = Rot64(h0,47); h1 += h0;
h2 ^= h1; h1 = Rot64(h1,54); h2 += h1;
h3 ^= h2; h2 = Rot64(h2,32); h3 += h2;
h0 ^= h3; h3 = Rot64(h3,25); h0 += h3;
h1 ^= h0; h0 = Rot64(h0,63); h1 += h0;
}
private:
//
// Short is used for messages under 192 bytes in length
// Short has a low startup cost, the normal mode is good for long
// keys, the cost crossover is at about 192 bytes. The two modes were
// held to the same quality bar.
//
static void Short(
const void *message, // message (byte array, not necessarily aligned)
size_t length, // length of message (in bytes)
uint64_t *hash1, // in/out: in the seed, out the hash value
uint64_t *hash2); // in/out: in the seed, out the hash value
// number of uint64_t's in internal state
static const size_t sc_numVars = 12;
// size of the internal state
static const size_t sc_blockSize = sc_numVars*8;
// size of buffer of unhashed data, in bytes
static const size_t sc_bufSize = 2*sc_blockSize;
//
// sc_const: a constant which:
// * is not zero
// * is odd
// * is a not-very-regular mix of 1's and 0's
// * does not need any other special mathematical properties
//
static const uint64_t sc_const = 0xdeadbeefdeadbeefLL;
uint64_t m_data[2*sc_numVars]; // unhashed data, for partial messages
uint64_t m_state[sc_numVars]; // internal state of the hash
size_t m_length; // total length of the input so far
uint8_t m_remainder; // length of unhashed data stashed in m_data
};
} // namespace hash
} // namespace folly
#endif
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