47fa3b1b10
We need a fast and good (high avalanche properties) hash function for the png caching to avoid collissions (even in the very limited samples we have, since tiles are likely to have patters, such as all 0's and all 1's etc.). Bob Jenkins's public domain SpookyV2 is used here. It has great avalanache properties and is fast at ~3-bytes / cycle for large messages. Only trailing whitespace was removed from original sources and 4 tabs converted to spaces. Change-Id: Ife57237321625c836d85c894d939fd04a8f577bb Reviewed-on: https://gerrit.libreoffice.org/31292 Reviewed-by: Ashod Nakashian <ashnakash@gmail.com> Tested-by: Ashod Nakashian <ashnakash@gmail.com>
299 lines
12 KiB
C++
299 lines
12 KiB
C++
//
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// SpookyHash: a 128-bit noncryptographic hash function
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// By Bob Jenkins, public domain
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// Oct 31 2010: alpha, framework + SpookyHash::Mix appears right
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// Oct 31 2011: alpha again, Mix only good to 2^^69 but rest appears right
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// Dec 31 2011: beta, improved Mix, tested it for 2-bit deltas
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// Feb 2 2012: production, same bits as beta
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// Feb 5 2012: adjusted definitions of uint* to be more portable
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// Mar 30 2012: 3 bytes/cycle, not 4. Alpha was 4 but wasn't thorough enough.
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// August 5 2012: SpookyV2 (different results)
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//
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// Up to 3 bytes/cycle for long messages. Reasonably fast for short messages.
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// All 1 or 2 bit deltas achieve avalanche within 1% bias per output bit.
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//
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// This was developed for and tested on 64-bit x86-compatible processors.
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// It assumes the processor is little-endian. There is a macro
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// controlling whether unaligned reads are allowed (by default they are).
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// This should be an equally good hash on big-endian machines, but it will
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// compute different results on them than on little-endian machines.
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//
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// Google's CityHash has similar specs to SpookyHash, and CityHash is faster
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// on new Intel boxes. MD4 and MD5 also have similar specs, but they are orders
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// of magnitude slower. CRCs are two or more times slower, but unlike
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// SpookyHash, they have nice math for combining the CRCs of pieces to form
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// the CRCs of wholes. There are also cryptographic hashes, but those are even
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// slower than MD5.
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//
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#include <stddef.h>
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#ifdef _MSC_VER
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# define INLINE __forceinline
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typedef unsigned __int64 uint64;
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typedef unsigned __int32 uint32;
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typedef unsigned __int16 uint16;
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typedef unsigned __int8 uint8;
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#else
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# include <stdint.h>
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# define INLINE inline
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typedef uint64_t uint64;
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typedef uint32_t uint32;
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typedef uint16_t uint16;
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typedef uint8_t uint8;
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#endif
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class SpookyHash
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{
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public:
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//
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// SpookyHash: hash a single message in one call, produce 128-bit output
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//
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static void Hash128(
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const void *message, // message to hash
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size_t length, // length of message in bytes
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uint64 *hash1, // in/out: in seed 1, out hash value 1
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uint64 *hash2); // in/out: in seed 2, out hash value 2
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//
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// Hash64: hash a single message in one call, return 64-bit output
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//
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static uint64 Hash64(
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const void *message, // message to hash
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size_t length, // length of message in bytes
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uint64 seed) // seed
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{
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uint64 hash1 = seed;
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Hash128(message, length, &hash1, &seed);
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return hash1;
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}
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//
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// Hash32: hash a single message in one call, produce 32-bit output
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//
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static uint32 Hash32(
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const void *message, // message to hash
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size_t length, // length of message in bytes
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uint32 seed) // seed
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{
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uint64 hash1 = seed, hash2 = seed;
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Hash128(message, length, &hash1, &hash2);
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return (uint32)hash1;
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}
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//
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// Init: initialize the context of a SpookyHash
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//
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void Init(
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uint64 seed1, // any 64-bit value will do, including 0
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uint64 seed2); // different seeds produce independent hashes
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//
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// Update: add a piece of a message to a SpookyHash state
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//
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void Update(
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const void *message, // message fragment
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size_t length); // length of message fragment in bytes
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//
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// Final: compute the hash for the current SpookyHash state
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//
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// This does not modify the state; you can keep updating it afterward
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//
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// The result is the same as if SpookyHash() had been called with
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// all the pieces concatenated into one message.
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//
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void Final(
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uint64 *hash1, // out only: first 64 bits of hash value.
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uint64 *hash2); // out only: second 64 bits of hash value.
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//
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// left rotate a 64-bit value by k bytes
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//
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static INLINE uint64 Rot64(uint64 x, int k)
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{
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return (x << k) | (x >> (64 - k));
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}
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//
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// This is used if the input is 96 bytes long or longer.
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//
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// The internal state is fully overwritten every 96 bytes.
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// Every input bit appears to cause at least 128 bits of entropy
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// before 96 other bytes are combined, when run forward or backward
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// For every input bit,
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// Two inputs differing in just that input bit
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// Where "differ" means xor or subtraction
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// And the base value is random
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// When run forward or backwards one Mix
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// I tried 3 pairs of each; they all differed by at least 212 bits.
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//
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static INLINE void Mix(
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const uint64 *data,
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uint64 &s0, uint64 &s1, uint64 &s2, uint64 &s3,
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uint64 &s4, uint64 &s5, uint64 &s6, uint64 &s7,
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uint64 &s8, uint64 &s9, uint64 &s10,uint64 &s11)
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{
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s0 += data[0]; s2 ^= s10; s11 ^= s0; s0 = Rot64(s0,11); s11 += s1;
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s1 += data[1]; s3 ^= s11; s0 ^= s1; s1 = Rot64(s1,32); s0 += s2;
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s2 += data[2]; s4 ^= s0; s1 ^= s2; s2 = Rot64(s2,43); s1 += s3;
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s3 += data[3]; s5 ^= s1; s2 ^= s3; s3 = Rot64(s3,31); s2 += s4;
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s4 += data[4]; s6 ^= s2; s3 ^= s4; s4 = Rot64(s4,17); s3 += s5;
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s5 += data[5]; s7 ^= s3; s4 ^= s5; s5 = Rot64(s5,28); s4 += s6;
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s6 += data[6]; s8 ^= s4; s5 ^= s6; s6 = Rot64(s6,39); s5 += s7;
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s7 += data[7]; s9 ^= s5; s6 ^= s7; s7 = Rot64(s7,57); s6 += s8;
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s8 += data[8]; s10 ^= s6; s7 ^= s8; s8 = Rot64(s8,55); s7 += s9;
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s9 += data[9]; s11 ^= s7; s8 ^= s9; s9 = Rot64(s9,54); s8 += s10;
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s10 += data[10]; s0 ^= s8; s9 ^= s10; s10 = Rot64(s10,22); s9 += s11;
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s11 += data[11]; s1 ^= s9; s10 ^= s11; s11 = Rot64(s11,46); s10 += s0;
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}
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//
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// Mix all 12 inputs together so that h0, h1 are a hash of them all.
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//
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// For two inputs differing in just the input bits
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// Where "differ" means xor or subtraction
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// And the base value is random, or a counting value starting at that bit
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// The final result will have each bit of h0, h1 flip
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// For every input bit,
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// with probability 50 +- .3%
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// For every pair of input bits,
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// with probability 50 +- 3%
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//
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// This does not rely on the last Mix() call having already mixed some.
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// Two iterations was almost good enough for a 64-bit result, but a
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// 128-bit result is reported, so End() does three iterations.
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//
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static INLINE void EndPartial(
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uint64 &h0, uint64 &h1, uint64 &h2, uint64 &h3,
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uint64 &h4, uint64 &h5, uint64 &h6, uint64 &h7,
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uint64 &h8, uint64 &h9, uint64 &h10,uint64 &h11)
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{
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h11+= h1; h2 ^= h11; h1 = Rot64(h1,44);
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h0 += h2; h3 ^= h0; h2 = Rot64(h2,15);
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h1 += h3; h4 ^= h1; h3 = Rot64(h3,34);
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h2 += h4; h5 ^= h2; h4 = Rot64(h4,21);
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h3 += h5; h6 ^= h3; h5 = Rot64(h5,38);
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h4 += h6; h7 ^= h4; h6 = Rot64(h6,33);
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h5 += h7; h8 ^= h5; h7 = Rot64(h7,10);
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h6 += h8; h9 ^= h6; h8 = Rot64(h8,13);
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h7 += h9; h10^= h7; h9 = Rot64(h9,38);
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h8 += h10; h11^= h8; h10= Rot64(h10,53);
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h9 += h11; h0 ^= h9; h11= Rot64(h11,42);
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h10+= h0; h1 ^= h10; h0 = Rot64(h0,54);
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}
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static INLINE void End(
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const uint64 *data,
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uint64 &h0, uint64 &h1, uint64 &h2, uint64 &h3,
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uint64 &h4, uint64 &h5, uint64 &h6, uint64 &h7,
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uint64 &h8, uint64 &h9, uint64 &h10,uint64 &h11)
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{
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h0 += data[0]; h1 += data[1]; h2 += data[2]; h3 += data[3];
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h4 += data[4]; h5 += data[5]; h6 += data[6]; h7 += data[7];
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h8 += data[8]; h9 += data[9]; h10 += data[10]; h11 += data[11];
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EndPartial(h0,h1,h2,h3,h4,h5,h6,h7,h8,h9,h10,h11);
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EndPartial(h0,h1,h2,h3,h4,h5,h6,h7,h8,h9,h10,h11);
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EndPartial(h0,h1,h2,h3,h4,h5,h6,h7,h8,h9,h10,h11);
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}
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//
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// The goal is for each bit of the input to expand into 128 bits of
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// apparent entropy before it is fully overwritten.
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// n trials both set and cleared at least m bits of h0 h1 h2 h3
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// n: 2 m: 29
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// n: 3 m: 46
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// n: 4 m: 57
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// n: 5 m: 107
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// n: 6 m: 146
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// n: 7 m: 152
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// when run forwards or backwards
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// for all 1-bit and 2-bit diffs
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// with diffs defined by either xor or subtraction
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// with a base of all zeros plus a counter, or plus another bit, or random
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//
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static INLINE void ShortMix(uint64 &h0, uint64 &h1, uint64 &h2, uint64 &h3)
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{
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h2 = Rot64(h2,50); h2 += h3; h0 ^= h2;
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h3 = Rot64(h3,52); h3 += h0; h1 ^= h3;
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h0 = Rot64(h0,30); h0 += h1; h2 ^= h0;
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h1 = Rot64(h1,41); h1 += h2; h3 ^= h1;
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h2 = Rot64(h2,54); h2 += h3; h0 ^= h2;
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h3 = Rot64(h3,48); h3 += h0; h1 ^= h3;
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h0 = Rot64(h0,38); h0 += h1; h2 ^= h0;
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h1 = Rot64(h1,37); h1 += h2; h3 ^= h1;
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h2 = Rot64(h2,62); h2 += h3; h0 ^= h2;
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h3 = Rot64(h3,34); h3 += h0; h1 ^= h3;
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h0 = Rot64(h0,5); h0 += h1; h2 ^= h0;
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h1 = Rot64(h1,36); h1 += h2; h3 ^= h1;
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}
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//
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// Mix all 4 inputs together so that h0, h1 are a hash of them all.
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//
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// For two inputs differing in just the input bits
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// Where "differ" means xor or subtraction
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// And the base value is random, or a counting value starting at that bit
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// The final result will have each bit of h0, h1 flip
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// For every input bit,
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// with probability 50 +- .3% (it is probably better than that)
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// For every pair of input bits,
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// with probability 50 +- .75% (the worst case is approximately that)
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//
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static INLINE void ShortEnd(uint64 &h0, uint64 &h1, uint64 &h2, uint64 &h3)
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{
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h3 ^= h2; h2 = Rot64(h2,15); h3 += h2;
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h0 ^= h3; h3 = Rot64(h3,52); h0 += h3;
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h1 ^= h0; h0 = Rot64(h0,26); h1 += h0;
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h2 ^= h1; h1 = Rot64(h1,51); h2 += h1;
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h3 ^= h2; h2 = Rot64(h2,28); h3 += h2;
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h0 ^= h3; h3 = Rot64(h3,9); h0 += h3;
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h1 ^= h0; h0 = Rot64(h0,47); h1 += h0;
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h2 ^= h1; h1 = Rot64(h1,54); h2 += h1;
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h3 ^= h2; h2 = Rot64(h2,32); h3 += h2;
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h0 ^= h3; h3 = Rot64(h3,25); h0 += h3;
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h1 ^= h0; h0 = Rot64(h0,63); h1 += h0;
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}
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private:
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//
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// Short is used for messages under 192 bytes in length
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// Short has a low startup cost, the normal mode is good for long
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// keys, the cost crossover is at about 192 bytes. The two modes were
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// held to the same quality bar.
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//
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static void Short(
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const void *message, // message (array of bytes, not necessarily aligned)
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size_t length, // length of message (in bytes)
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uint64 *hash1, // in/out: in the seed, out the hash value
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uint64 *hash2); // in/out: in the seed, out the hash value
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// number of uint64's in internal state
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static const size_t sc_numVars = 12;
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// size of the internal state
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static const size_t sc_blockSize = sc_numVars*8;
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// size of buffer of unhashed data, in bytes
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static const size_t sc_bufSize = 2*sc_blockSize;
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//
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// sc_const: a constant which:
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// * is not zero
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// * is odd
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// * is a not-very-regular mix of 1's and 0's
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// * does not need any other special mathematical properties
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//
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static const uint64 sc_const = 0xdeadbeefdeadbeefLL;
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uint64 m_data[2*sc_numVars]; // unhashed data, for partial messages
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uint64 m_state[sc_numVars]; // internal state of the hash
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size_t m_length; // total length of the input so far
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uint8 m_remainder; // length of unhashed data stashed in m_data
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};
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