UINT64 Hash64(const BYTE *k, UINT Length)
{
UINT a, b, c, LocalLength;
/* Set up the internal state */
LocalLength = Length;
a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */
c = 0x9b9773e9;
/*---------------------------------------- handle most of the key */
while (LocalLength >= 12)
{
a += (k[0] + ((UINT)k[1]<<8) + ((UINT)k[2]<<16) + ((UINT)k[3]<<24));
b += (k[4] + ((UINT)k[5]<<8) + ((UINT)k[6]<<16) + ((UINT)k[7]<<24));
c += (k[8] + ((UINT)k[9]<<8) + ((UINT)k[10]<<16)+ ((UINT)k[11]<<24));
HashMix(a, b, c);
k += 12;
LocalLength -= 12;
}
/*------------------------------------- handle the last 11 bytes */
c += Length;
switch(LocalLength) /* all the case statements fall through */
{
case 11: c += ((UINT)k[10]<<24);
case 10: c += ((UINT)k[9]<<16);
case 9 : c += ((UINT)k[8]<<8);
/* the first byte of c is reserved for the length */
case 8 : b += ((UINT)k[7]<<24);
case 7 : b += ((UINT)k[6]<<16);
case 6 : b += ((UINT)k[5]<<8);
case 5 : b += k[4];
case 4 : a += ((UINT)k[3]<<24);
case 3 : a += ((UINT)k[2]<<16);
case 2 : a += ((UINT)k[1]<<8);
case 1 : a += k[0];
/* case 0: nothing left to add */
}
HashMix(a, b, c);
/*-------------------------------------------- report the result */
return UINT64(c) + UINT64(UINT64(a) << 32);
}
void BloomFilter::insert(size_t hash) {
for (size_t i = 0; i < hash_keys_.size(); i++) {
uint32_t mix = HashMix(hash_keys_[i], hash);
uint32_t index = mix % bit_size_;
size_t byte = index / 8;
size_t bit = index % 8;
// set the bit
data_[byte] |= (1 << bit);
}
}
// Notice that bytes are from left-to-right, whereas bits are taken from right-to-left..
// This is not a problem as long as they are same in insert and exists..
bool BloomFilter::exists(size_t hash) const {
for (size_t i= 0; i < hash_keys_.size(); i++) {
uint32_t mix = HashMix(hash_keys_[i], hash);
uint32_t index = mix % bit_size_;
size_t byte = index / 8;
size_t bit = index % 8;
// check if the bit is set.
if (!(data_.at(byte) & (1 << bit)))
return false;
}
return true;
}
