| use crate::stable_hasher; |
| use rustc_serialize::{ |
| opaque::{self, EncodeResult}, |
| Decodable, Encodable, |
| }; |
| use std::hash::{Hash, Hasher}; |
| use std::mem; |
| |
| #[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Copy)] |
| pub struct Fingerprint(u64, u64); |
| |
| impl Fingerprint { |
| pub const ZERO: Fingerprint = Fingerprint(0, 0); |
| |
| #[inline] |
| pub fn from_smaller_hash(hash: u64) -> Fingerprint { |
| Fingerprint(hash, hash) |
| } |
| |
| #[inline] |
| pub fn to_smaller_hash(&self) -> u64 { |
| self.0 |
| } |
| |
| #[inline] |
| pub fn as_value(&self) -> (u64, u64) { |
| (self.0, self.1) |
| } |
| |
| #[inline] |
| pub fn combine(self, other: Fingerprint) -> Fingerprint { |
| // See https://stackoverflow.com/a/27952689 on why this function is |
| // implemented this way. |
| Fingerprint( |
| self.0.wrapping_mul(3).wrapping_add(other.0), |
| self.1.wrapping_mul(3).wrapping_add(other.1), |
| ) |
| } |
| |
| // Combines two hashes in an order independent way. Make sure this is what |
| // you want. |
| #[inline] |
| pub fn combine_commutative(self, other: Fingerprint) -> Fingerprint { |
| let a = u128::from(self.1) << 64 | u128::from(self.0); |
| let b = u128::from(other.1) << 64 | u128::from(other.0); |
| |
| let c = a.wrapping_add(b); |
| |
| Fingerprint((c >> 64) as u64, c as u64) |
| } |
| |
| pub fn to_hex(&self) -> String { |
| format!("{:x}{:x}", self.0, self.1) |
| } |
| |
| pub fn encode_opaque(&self, encoder: &mut opaque::Encoder) -> EncodeResult { |
| let bytes: [u8; 16] = unsafe { mem::transmute([self.0.to_le(), self.1.to_le()]) }; |
| |
| encoder.emit_raw_bytes(&bytes); |
| Ok(()) |
| } |
| |
| pub fn decode_opaque(decoder: &mut opaque::Decoder<'_>) -> Result<Fingerprint, String> { |
| let mut bytes = [0; 16]; |
| |
| decoder.read_raw_bytes(&mut bytes)?; |
| |
| let [l, r]: [u64; 2] = unsafe { mem::transmute(bytes) }; |
| |
| Ok(Fingerprint(u64::from_le(l), u64::from_le(r))) |
| } |
| } |
| |
| impl std::fmt::Display for Fingerprint { |
| fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { |
| write!(formatter, "{:x}-{:x}", self.0, self.1) |
| } |
| } |
| |
| impl Hash for Fingerprint { |
| #[inline] |
| fn hash<H: Hasher>(&self, state: &mut H) { |
| state.write_fingerprint(self); |
| } |
| } |
| |
| trait FingerprintHasher { |
| fn write_fingerprint(&mut self, fingerprint: &Fingerprint); |
| } |
| |
| impl<H: Hasher> FingerprintHasher for H { |
| #[inline] |
| default fn write_fingerprint(&mut self, fingerprint: &Fingerprint) { |
| self.write_u64(fingerprint.0); |
| self.write_u64(fingerprint.1); |
| } |
| } |
| |
| impl FingerprintHasher for crate::unhash::Unhasher { |
| #[inline] |
| fn write_fingerprint(&mut self, fingerprint: &Fingerprint) { |
| // `Unhasher` only wants a single `u64` |
| self.write_u64(fingerprint.0); |
| } |
| } |
| |
| impl stable_hasher::StableHasherResult for Fingerprint { |
| #[inline] |
| fn finish(hasher: stable_hasher::StableHasher) -> Self { |
| let (_0, _1) = hasher.finalize(); |
| Fingerprint(_0, _1) |
| } |
| } |
| |
| impl_stable_hash_via_hash!(Fingerprint); |
| |
| impl<E: rustc_serialize::Encoder> Encodable<E> for Fingerprint { |
| fn encode(&self, s: &mut E) -> Result<(), E::Error> { |
| s.encode_fingerprint(self) |
| } |
| } |
| |
| impl<D: rustc_serialize::Decoder> Decodable<D> for Fingerprint { |
| fn decode(d: &mut D) -> Result<Self, D::Error> { |
| d.decode_fingerprint() |
| } |
| } |
| |
| pub trait FingerprintEncoder: rustc_serialize::Encoder { |
| fn encode_fingerprint(&mut self, f: &Fingerprint) -> Result<(), Self::Error>; |
| } |
| |
| pub trait FingerprintDecoder: rustc_serialize::Decoder { |
| fn decode_fingerprint(&mut self) -> Result<Fingerprint, Self::Error>; |
| } |
| |
| impl<E: rustc_serialize::Encoder> FingerprintEncoder for E { |
| default fn encode_fingerprint(&mut self, _: &Fingerprint) -> Result<(), E::Error> { |
| panic!("Cannot encode `Fingerprint` with `{}`", std::any::type_name::<E>()); |
| } |
| } |
| |
| impl FingerprintEncoder for opaque::Encoder { |
| fn encode_fingerprint(&mut self, f: &Fingerprint) -> EncodeResult { |
| f.encode_opaque(self) |
| } |
| } |
| |
| impl<D: rustc_serialize::Decoder> FingerprintDecoder for D { |
| default fn decode_fingerprint(&mut self) -> Result<Fingerprint, D::Error> { |
| panic!("Cannot decode `Fingerprint` with `{}`", std::any::type_name::<D>()); |
| } |
| } |
| impl FingerprintDecoder for opaque::Decoder<'_> { |
| fn decode_fingerprint(&mut self) -> Result<Fingerprint, String> { |
| Fingerprint::decode_opaque(self) |
| } |
| } |