SpookyV2.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 "SpookyV2.h"

#include <memory>

#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::Short(
  const void *message,
  size_t length,
  uint64_t *hash1,
  uint64_t *hash2) {
  uint64_t buf[2*sc_numVars];
  union {
    const uint8_t *p8;
    uint32_t *p32;
    uint64_t *p64;
    size_t i;
  } u;

  u.p8 = static_cast<const uint8_t *>(message);

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

  size_t remainder = length%32;
  uint64_t a=*hash1;
  uint64_t b=*hash2;
  uint64_t c=sc_const;
  uint64_t d=sc_const;

  if (length > 15) {
    const uint64_t *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 += (static_cast<uint64_t>(length)) << 56;
  switch (remainder) {
  case 15:
    d += (static_cast<uint64_t>(u.p8[14])) << 48;
  case 14:
    d += (static_cast<uint64_t>(u.p8[13])) << 40;
  case 13:
    d += (static_cast<uint64_t>(u.p8[12])) << 32;
  case 12:
    d += u.p32[2];
    c += u.p64[0];
    break;
  case 11:
    d += (static_cast<uint64_t>(u.p8[10])) << 16;
  case 10:
    d += (static_cast<uint64_t>(u.p8[9])) << 8;
  case 9:
    d += (static_cast<uint64_t>(u.p8[8]));
  case 8:
    c += u.p64[0];
    break;
  case 7:
    c += (static_cast<uint64_t>(u.p8[6])) << 48;
  case 6:
    c += (static_cast<uint64_t>(u.p8[5])) << 40;
  case 5:
    c += (static_cast<uint64_t>(u.p8[4])) << 32;
  case 4:
    c += u.p32[0];
    break;
  case 3:
    c += (static_cast<uint64_t>(u.p8[2])) << 16;
  case 2:
    c += (static_cast<uint64_t>(u.p8[1])) << 8;
  case 1:
    c += (static_cast<uint64_t>(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_t *hash1,
  uint64_t *hash2) {
  if (length < sc_bufSize) {
    Short(message, length, hash1, hash2);
    return;
  }

  uint64_t h0,h1,h2,h3,h4,h5,h6,h7,h8,h9,h10,h11;
  uint64_t buf[sc_numVars];
  uint64_t *end;
  union {
    const uint8_t *p8;
    uint64_t *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 = static_cast<const uint8_t *>(message);
  end = 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 < 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(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 - (reinterpret_cast<const uint8_t *>(end)-static_cast<const uint8_t *>(message)));
  memcpy(buf, end, remainder);
  memset((reinterpret_cast<uint8_t *>(buf))+remainder, 0, sc_blockSize-remainder);
  (reinterpret_cast<uint8_t *>(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
void SpookyHash::Init(uint64_t seed1, uint64_t 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_t h0,h1,h2,h3,h4,h5,h6,h7,h8,h9,h10,h11;
  size_t   newLength = length + m_remainder;
  uint8_t  remainder;
  union {
    const uint8_t *p8;
    uint64_t *p64;
    size_t i;
  } u;
  const uint64_t *end;

  // Is this message fragment too short?  If it is, stuff it away.
  if (newLength < sc_bufSize) {
    memcpy(&(reinterpret_cast<uint8_t *>(m_data))[m_remainder], message, length);
    m_length = length + m_length;
    m_remainder = static_cast<uint8_t>(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_t prefix = sc_bufSize-m_remainder;
    memcpy(&((reinterpret_cast<uint8_t *>(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 = (static_cast<const uint8_t *>(message)) + prefix;
    length -= prefix;
  } else {
    u.p8 = static_cast<const uint8_t *>(message);
  }

  // handle all whole blocks of sc_blockSize bytes
  end = u.p64 + (length/sc_blockSize)*sc_numVars;
  remainder = static_cast<uint8_t>(length-(reinterpret_cast<const uint8_t *>(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_t *hash1, uint64_t *hash2) {
  // init the variables
  if (m_length < sc_bufSize) {
    *hash1 = m_state[0];
    *hash2 = m_state[1];
    Short( m_data, m_length, hash1, hash2);
    return;
  }

  const uint64_t *data = static_cast<const uint64_t *>(m_data);
  uint8_t remainder = m_remainder;

  uint64_t h0 = m_state[0];
  uint64_t h1 = m_state[1];
  uint64_t h2 = m_state[2];
  uint64_t h3 = m_state[3];
  uint64_t h4 = m_state[4];
  uint64_t h5 = m_state[5];
  uint64_t h6 = m_state[6];
  uint64_t h7 = m_state[7];
  uint64_t h8 = m_state[8];
  uint64_t h9 = m_state[9];
  uint64_t h10 = m_state[10];
  uint64_t 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(&(reinterpret_cast<uint8_t *>(const_cast<uint64_t *>(data)))[remainder], 0, (sc_blockSize-remainder));

  (reinterpret_cast<uint8_t *>(const_cast<uint64_t *>(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;
}