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// 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 Alembic_Util_SpookyV2_h

#define Alembic_Util_SpookyV2_h

#include <Alembic/Util/Export.h>

#include <Alembic/Util/PlainOldDataType.h>

namespace Alembic {

namespace Util {

namespace ALEMBIC_VERSION_NS {

class ALEMBIC_EXPORT SpookyHash

{

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 (array of bytes, 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'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

};

} // End namespace ALEMBIC_VERSION_NS

using namespace ALEMBIC_VERSION_NS;

} // End namespace Util

} // End namespace Alembic

#endif