1 use crate::stable_hasher;
4 use serialize::opaque::{EncodeResult, Encoder, Decoder};
6 #[derive(Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Clone, Copy)]
7 pub struct Fingerprint(u64, u64);
11 pub const ZERO: Fingerprint = Fingerprint(0, 0);
14 pub fn from_smaller_hash(hash: u64) -> Fingerprint {
15 Fingerprint(hash, hash)
19 pub fn to_smaller_hash(&self) -> u64 {
24 pub fn as_value(&self) -> (u64, u64) {
29 pub fn combine(self, other: Fingerprint) -> Fingerprint {
30 // See https://stackoverflow.com/a/27952689 on why this function is
31 // implemented this way.
33 self.0.wrapping_mul(3).wrapping_add(other.0),
34 self.1.wrapping_mul(3).wrapping_add(other.1)
38 // Combines two hashes in an order independent way. Make sure this is what
41 pub fn combine_commutative(self, other: Fingerprint) -> Fingerprint {
42 let a = (self.1 as u128) << 64 | self.0 as u128;
43 let b = (other.1 as u128) << 64 | other.0 as u128;
45 let c = a.wrapping_add(b);
47 Fingerprint((c >> 64) as u64, c as u64)
50 pub fn to_hex(&self) -> String {
51 format!("{:x}{:x}", self.0, self.1)
54 pub fn encode_opaque(&self, encoder: &mut Encoder) -> EncodeResult {
55 let bytes: [u8; 16] = unsafe { mem::transmute([self.0.to_le(), self.1.to_le()]) };
57 encoder.emit_raw_bytes(&bytes);
61 pub fn decode_opaque<'a>(decoder: &mut Decoder<'a>) -> Result<Fingerprint, String> {
62 let mut bytes = [0; 16];
64 decoder.read_raw_bytes(&mut bytes)?;
66 let [l, r]: [u64; 2] = unsafe { mem::transmute(bytes) };
68 Ok(Fingerprint(u64::from_le(l), u64::from_le(r)))
72 impl ::std::fmt::Display for Fingerprint {
73 fn fmt(&self, formatter: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
74 write!(formatter, "{:x}-{:x}", self.0, self.1)
78 impl stable_hasher::StableHasherResult for Fingerprint {
80 fn finish(hasher: stable_hasher::StableHasher<Self>) -> Self {
81 let (_0, _1) = hasher.finalize();
86 impl_stable_hash_via_hash!(Fingerprint);
88 impl serialize::UseSpecializedEncodable for Fingerprint { }
90 impl serialize::UseSpecializedDecodable for Fingerprint { }
92 impl serialize::SpecializedEncoder<Fingerprint> for serialize::opaque::Encoder {
93 fn specialized_encode(&mut self, f: &Fingerprint) -> Result<(), Self::Error> {
98 impl<'a> serialize::SpecializedDecoder<Fingerprint> for serialize::opaque::Decoder<'a> {
99 fn specialized_decode(&mut self) -> Result<Fingerprint, Self::Error> {
100 Fingerprint::decode_opaque(self)