spooky.cpp

// Spooky Hash
// A 128-bit noncryptographic hash, for checksums and table lookup
// By Bob Jenkins.  Public domain.
//   Oct 31 2010: published framework, disclaimer ShortHash isn't right
//   Nov 7 2010: disabled ShortHash
//   Oct 31 2011: replace end, shortMix, shortEnd, enable ShortHash again
//   April 10 2012: buffer overflow on platforms without unaligned reads
//   July 12 2012: was passing out variables in final to in/out in short
//   July 30 2012: I reintroduced the buffer overflow
//   August 5 2012: SpookyV2: d = should be d += in short hash, and remove extra mix from long hash

#include <memory.h>
#include "spooky.h"

#define ALLOW_UNALIGNED_READS 1

//
// short hash ... it could be used on any message,
// but it's used by Spooky just for short messages.
//
void SpookyHash::shortHash(
    const void* message,
    size_t length,
    uint64* hash1,
    uint64* hash2
) {
    uint64 buf[2 * sc_numVars];
    union {
        const uint8* p8;
        uint32* p32;
        uint64* p64;
        size_t i;
    } u;

    u.p8 = (const uint8*) message;

    if(!ALLOW_UNALIGNED_READS && (u.i & 0x7)) {
        memcpy(buf, message, length);
        u.p64 = buf;
    }

    size_t remainder = length % 32;
    uint64 a = *hash1;
    uint64 b = *hash2;
    uint64 c = sc_const;
    uint64 d = sc_const;

    if(length > 15) {
        const uint64* end = u.p64 + (length / 32) * 4;

        // handle all complete sets of 32 bytes
        for(
            ; u.p64 < end; u.p64 += 4
            ) {
            c += u.p64[0];
            d += u.p64[1];
            shortMix(a, b, c, d);
            a += u.p64[2];
            b += u.p64[3];
        }

        //Handle the case of 16+ remaining bytes.
        if(remainder >= 16) {
            c += u.p64[0];
            d += u.p64[1];
            shortMix(a, b, c, d);
            u.p64 += 2;
            remainder -= 16;
        }
    }

    // Handle the last 0..15 bytes, and its length
    d += ((uint64) length) << 56;
    switch(remainder) {
    case 15:d += ((uint64) u.p8[14]) << 48;
    case 14:d += ((uint64) u.p8[13]) << 40;
    case 13:d += ((uint64) u.p8[12]) << 32;
    case 12:d += u.p32[2];
        c += u.p64[0];
        break;
    case 11:d += ((uint64) u.p8[10]) << 16;
    case 10:d += ((uint64) u.p8[9]) << 8;
    case 9:d += (uint64) u.p8[8];
    case 8:c += u.p64[0];
        break;
    case 7:c += ((uint64) u.p8[6]) << 48;
    case 6:c += ((uint64) u.p8[5]) << 40;
    case 5:c += ((uint64) u.p8[4]) << 32;
    case 4:c += u.p32[0];
        break;
    case 3:c += ((uint64) u.p8[2]) << 16;
    case 2:c += ((uint64) u.p8[1]) << 8;
    case 1:c += (uint64) u.p8[0];
        break;
    case 0:c += sc_const;
        d += sc_const;
    }
    shortEnd(a, b, c, d);
    *hash1 = a;
    *hash2 = b;
}


// do the whole hash in one call
void SpookyHash::hash128(
    const void* message,
    size_t length,
    uint64* hash1,
    uint64* hash2
) {
    if(length < sc_bufSize) {
        shortHash(message, length, hash1, hash2);
        return;
    }

    uint64 h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11;
    uint64 buf[sc_numVars];
    uint64* pEnd;
    union {
        const uint8* p8;
        uint64* p64;
        size_t i;
    } u;
    size_t remainder;

    h0 = h3 = h6 = h9 = *hash1;
    h1 = h4 = h7 = h10 = *hash2;
    h2 = h5 = h8 = h11 = sc_const;

    u.p8 = (const uint8*) message;
    pEnd = u.p64 + (length / sc_blockSize) * sc_numVars;

    // handle all whole sc_blockSize blocks of bytes
    if(ALLOW_UNALIGNED_READS || ((u.i & 0x7) == 0)) {
        while(u.p64 < pEnd) {
            mix(u.p64, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11);
            u.p64 += sc_numVars;
        }
    } else {
        while(u.p64 < pEnd) {
            memcpy(buf, u.p64, sc_blockSize);
            mix(buf, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11);
            u.p64 += sc_numVars;
        }
    }

    // handle the last partial block of sc_blockSize bytes
    remainder = (length - ((const uint8*) pEnd - (const uint8*) message));
    memcpy(buf, pEnd, remainder);
    memset(((uint8*) buf) + remainder, 0, sc_blockSize - remainder);
    ((uint8*) buf)[sc_blockSize - 1] = remainder;

    // do some final mixing
    end(buf, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11);
    *hash1 = h0;
    *hash2 = h1;
}


// init spooky state
SpookyHash::SpookyHash(uint64 seed1, uint64 seed2) :
    m_length(0),
    m_remainder(0)
{
    m_state[0] = seed1;
    m_state[1] = seed2;
}


// add a message fragment to the state
void SpookyHash::update(const void* message, size_t length) {
    uint64 h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11;
    size_t newLength = length + m_remainder;
    uint8 remainder;
    union {
        const uint8* p8;
        uint64* p64;
        size_t i;
    } u;
    const uint64* end;

    // Is this message fragment too short?  If it is, stuff it away.
    if(newLength < sc_bufSize) {
        memcpy(&((uint8*) m_data)[m_remainder], message, length);
        m_length = length + m_length;
        m_remainder = (uint8) newLength;
        return;
    }

    // init the variables
    if(m_length < sc_bufSize) {
        h0 = h3 = h6 = h9 = m_state[0];
        h1 = h4 = h7 = h10 = m_state[1];
        h2 = h5 = h8 = h11 = sc_const;
    } else {
        h0 = m_state[0];
        h1 = m_state[1];
        h2 = m_state[2];
        h3 = m_state[3];
        h4 = m_state[4];
        h5 = m_state[5];
        h6 = m_state[6];
        h7 = m_state[7];
        h8 = m_state[8];
        h9 = m_state[9];
        h10 = m_state[10];
        h11 = m_state[11];
    }
    m_length = length + m_length;

    // if we've got anything stuffed away, use it now
    if(m_remainder) {
        uint8 prefix = sc_bufSize - m_remainder;
        memcpy(&(((uint8*) m_data)[m_remainder]), message, prefix);
        u.p64 = m_data;
        mix(u.p64, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11);
        mix(&u.p64[sc_numVars], h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11);
        u.p8 = ((const uint8*) message) + prefix;
        length -= prefix;
    } else {
        u.p8 = (const uint8*) message;
    }

    // handle all whole blocks of sc_blockSize bytes
    end = u.p64 + (length / sc_blockSize) * sc_numVars;
    remainder = (uint8) (length - ((const uint8*) end - u.p8));
    if(ALLOW_UNALIGNED_READS || (u.i & 0x7) == 0) {
        while(u.p64 < end) {
            mix(u.p64, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11);
            u.p64 += sc_numVars;
        }
    } else {
        while(u.p64 < end) {
            memcpy(m_data, u.p8, sc_blockSize);
            mix(m_data, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11);
            u.p64 += sc_numVars;
        }
    }

    // stuff away the last few bytes
    m_remainder = remainder;
    memcpy(m_data, end, remainder);

    // stuff away the variables
    m_state[0] = h0;
    m_state[1] = h1;
    m_state[2] = h2;
    m_state[3] = h3;
    m_state[4] = h4;
    m_state[5] = h5;
    m_state[6] = h6;
    m_state[7] = h7;
    m_state[8] = h8;
    m_state[9] = h9;
    m_state[10] = h10;
    m_state[11] = h11;
}


// report the hash for the concatenation of all message fragments so far
void SpookyHash::final(uint64* hash1, uint64* hash2) {
    // init the variables
    if(m_length < sc_bufSize) {
        *hash1 = m_state[0];
        *hash2 = m_state[1];
        shortHash(m_data, m_length, hash1, hash2);
        return;
    }

    const uint64* data = (const uint64*) m_data;
    uint8 remainder = m_remainder;

    uint64 h0 = m_state[0];
    uint64 h1 = m_state[1];
    uint64 h2 = m_state[2];
    uint64 h3 = m_state[3];
    uint64 h4 = m_state[4];
    uint64 h5 = m_state[5];
    uint64 h6 = m_state[6];
    uint64 h7 = m_state[7];
    uint64 h8 = m_state[8];
    uint64 h9 = m_state[9];
    uint64 h10 = m_state[10];
    uint64 h11 = m_state[11];

    if(remainder >= sc_blockSize) {
        // m_data can contain two blocks; handle any whole first block
        mix(data, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11);
        data += sc_numVars;
        remainder -= sc_blockSize;
    }

    // mix in the last partial block, and the length mod sc_blockSize
    memset(&((uint8*) data)[remainder], 0, (sc_blockSize - remainder));

    ((uint8*) data)[sc_blockSize - 1] = remainder;

    // do some final mixing
    end(data, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11);

    *hash1 = h0;
    *hash2 = h1;
}