// NewCustom returns a new ImoHash using the provided sample size
// and sample threshhold values. The entire file will be hashed
// (i.e. no sampling), if sampleSize < 1.
func NewCustom(sampleSize, sampleThreshold int) ImoHash {
h := ImoHash{
hasher: murmur3.New128(),
sampleSize: sampleSize,
sampleThreshold: sampleThreshold,
}
return h
}
func GenerateBlockID(inodeID []byte, block uint64) []byte {
h := murmur3.New128()
h.Write(inodeID)
binary.Write(h, binary.BigEndian, block)
s1, s2 := h.Sum128()
b := bytes.NewBuffer([]byte(""))
binary.Write(b, binary.BigEndian, s1)
binary.Write(b, binary.BigEndian, s2)
return b.Bytes()
}
// baseHashes returns the four hash values of data that are used to create k
// hashes
func baseHashes(data []byte) [4]uint64 {
a1 := []byte{1} // to grab another bit of data
hasher := murmur3.New128()
hasher.Write(data)
v1, v2 := hasher.Sum128()
hasher.Write(a1)
v3, v4 := hasher.Sum128()
return [4]uint64{
v1, v2, v3, v4,
}
}
// M generates n bytes of pseudo-random data according to the
// method described in the imohash algorithm description.
func M(n int) []byte {
r := make([]byte, 0, n)
hasher := murmur3.New128()
for len(r) < n {
hasher.Write([]byte{'A'})
r = hasher.Sum(r)
}
return r[0:n]
}
func GetID(fsid []byte, inode, block uint64) []byte {
// TODO: Figure out what arrangement we want to use for the hash
h := murmur3.New128()
h.Write(fsid)
binary.Write(h, binary.BigEndian, inode)
binary.Write(h, binary.BigEndian, block)
s1, s2 := h.Sum128()
b := bytes.NewBuffer([]byte(""))
binary.Write(b, binary.BigEndian, s1)
binary.Write(b, binary.BigEndian, s2)
return b.Bytes()
}
