1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use rustc_data_structures::stable_hasher;
15 #[derive(Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Clone, Copy, RustcEncodable, RustcDecodable)]
16 pub struct Fingerprint(u64, u64);
20 pub fn zero() -> Fingerprint {
25 pub fn from_smaller_hash(hash: u64) -> Fingerprint {
26 Fingerprint(hash, hash)
30 pub fn to_smaller_hash(&self) -> u64 {
35 pub fn combine(self, other: Fingerprint) -> Fingerprint {
36 // See https://stackoverflow.com/a/27952689 on why this function is
37 // implemented this way.
39 self.0.wrapping_mul(3).wrapping_add(other.0),
40 self.1.wrapping_mul(3).wrapping_add(other.1)
44 pub fn to_hex(&self) -> String {
45 format!("{:x}{:x}", self.0, self.1)
50 impl ::std::fmt::Display for Fingerprint {
51 fn fmt(&self, formatter: &mut ::std::fmt::Formatter) -> Result<(), ::std::fmt::Error> {
52 write!(formatter, "{:x}-{:x}", self.0, self.1)
56 impl stable_hasher::StableHasherResult for Fingerprint {
57 fn finish(mut hasher: stable_hasher::StableHasher<Self>) -> Self {
58 let hash_bytes: &[u8] = hasher.finalize();
60 assert!(hash_bytes.len() >= mem::size_of::<u64>() * 2);
61 let hash_bytes: &[u64] = unsafe {
62 slice::from_raw_parts(hash_bytes.as_ptr() as *const u64, 2)
65 // The bytes returned bytes the Blake2B hasher are always little-endian.
66 Fingerprint(u64::from_le(hash_bytes[0]), u64::from_le(hash_bytes[1]))
70 impl<CTX> stable_hasher::HashStable<CTX> for Fingerprint {
72 fn hash_stable<W: stable_hasher::StableHasherResult>(&self,
74 hasher: &mut stable_hasher::StableHasher<W>) {
75 ::std::hash::Hash::hash(self, hasher);