| use crate::stable_hasher; |
| use std::mem; |
| use rustc_serialize::opaque::{EncodeResult, Encoder, Decoder}; |
| |
| #[derive(Eq, PartialEq, Ord, PartialOrd, Hash, 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 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 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 stable_hasher::StableHasherResult for Fingerprint { |
| #[inline] |
| fn finish(hasher: stable_hasher::StableHasher<Self>) -> Self { |
| let (_0, _1) = hasher.finalize(); |
| Fingerprint(_0, _1) |
| } |
| } |
| |
| impl_stable_hash_via_hash!(Fingerprint); |
| |
| impl rustc_serialize::UseSpecializedEncodable for Fingerprint { } |
| |
| impl rustc_serialize::UseSpecializedDecodable for Fingerprint { } |
| |
| impl rustc_serialize::SpecializedEncoder<Fingerprint> for Encoder { |
| fn specialized_encode(&mut self, f: &Fingerprint) -> Result<(), Self::Error> { |
| f.encode_opaque(self) |
| } |
| } |
| |
| impl<'a> rustc_serialize::SpecializedDecoder<Fingerprint> for Decoder<'a> { |
| fn specialized_decode(&mut self) -> Result<Fingerprint, Self::Error> { |
| Fingerprint::decode_opaque(self) |
| } |
| } |