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 std::hash::{Hash, Hasher};
12 use std::marker::PhantomData;
14 use blake2b::Blake2bHasher;
15 use rustc_serialize::leb128;
17 fn write_unsigned_leb128_to_buf(buf: &mut [u8; 16], value: u64) -> usize {
18 leb128::write_unsigned_leb128_to(value as u128, |i, v| buf[i] = v)
21 fn write_signed_leb128_to_buf(buf: &mut [u8; 16], value: i64) -> usize {
22 leb128::write_signed_leb128_to(value as i128, |i, v| buf[i] = v)
25 /// When hashing something that ends up affecting properties like symbol names. We
26 /// want these symbol names to be calculated independent of other factors like
27 /// what architecture you're compiling *from*.
29 /// The hashing just uses the standard `Hash` trait, but the implementations of
30 /// `Hash` for the `usize` and `isize` types are *not* architecture independent
31 /// (e.g. they has 4 or 8 bytes). As a result we want to avoid `usize` and
32 /// `isize` completely when hashing.
34 /// To do that, we encode all integers to be hashed with some
35 /// arch-independent encoding.
37 /// At the moment, we pass i8/u8 straight through and encode
38 /// all other integers using leb128.
40 /// This hasher currently always uses the stable Blake2b algorithm
41 /// and allows for variable output lengths through its type
44 pub struct StableHasher<W> {
47 width: PhantomData<W>,
50 pub trait StableHasherResult: Sized {
51 fn finish(hasher: StableHasher<Self>) -> Self;
54 impl<W: StableHasherResult> StableHasher<W> {
55 pub fn new() -> Self {
57 state: Blake2bHasher::new(mem::size_of::<W>(), &[]),
63 pub fn finish(self) -> W {
68 impl StableHasherResult for [u8; 20] {
69 fn finish(mut hasher: StableHasher<Self>) -> Self {
70 let mut result: [u8; 20] = [0; 20];
71 result.copy_from_slice(hasher.state.finalize());
76 impl StableHasherResult for u64 {
77 fn finish(mut hasher: StableHasher<Self>) -> Self {
78 hasher.state.finalize();
83 impl<W> StableHasher<W> {
85 pub fn finalize(&mut self) -> &[u8] {
90 pub fn bytes_hashed(&self) -> u64 {
95 fn write_uleb128(&mut self, value: u64) {
96 let mut buf = [0; 16];
97 let len = write_unsigned_leb128_to_buf(&mut buf, value);
98 self.state.write(&buf[..len]);
99 self.bytes_hashed += len as u64;
103 fn write_ileb128(&mut self, value: i64) {
104 let mut buf = [0; 16];
105 let len = write_signed_leb128_to_buf(&mut buf, value);
106 self.state.write(&buf[..len]);
107 self.bytes_hashed += len as u64;
111 // For the non-u8 integer cases we leb128 encode them first. Because small
112 // integers dominate, this significantly and cheaply reduces the number of
113 // bytes hashed, which is good because blake2b is expensive.
114 impl<W> Hasher for StableHasher<W> {
115 fn finish(&self) -> u64 {
116 panic!("use StableHasher::finish instead");
120 fn write(&mut self, bytes: &[u8]) {
121 self.state.write(bytes);
122 self.bytes_hashed += bytes.len() as u64;
126 fn write_u8(&mut self, i: u8) {
127 self.state.write_u8(i);
128 self.bytes_hashed += 1;
132 fn write_u16(&mut self, i: u16) {
133 self.write_uleb128(i as u64);
137 fn write_u32(&mut self, i: u32) {
138 self.write_uleb128(i as u64);
142 fn write_u64(&mut self, i: u64) {
143 self.write_uleb128(i);
147 fn write_usize(&mut self, i: usize) {
148 self.write_uleb128(i as u64);
152 fn write_i8(&mut self, i: i8) {
153 self.state.write_i8(i);
154 self.bytes_hashed += 1;
158 fn write_i16(&mut self, i: i16) {
159 self.write_ileb128(i as i64);
163 fn write_i32(&mut self, i: i32) {
164 self.write_ileb128(i as i64);
168 fn write_i64(&mut self, i: i64) {
169 self.write_ileb128(i);
173 fn write_isize(&mut self, i: isize) {
174 self.write_ileb128(i as i64);
179 /// Something that implements `HashStable<CTX>` can be hashed in a way that is
180 /// stable across multiple compiliation sessions.
181 pub trait HashStable<CTX> {
182 fn hash_stable<W: StableHasherResult>(&self,
184 hasher: &mut StableHasher<W>);
187 // Implement HashStable by just calling `Hash::hash()`. This works fine for
188 // self-contained values that don't depend on the hashing context `CTX`.
189 macro_rules! impl_stable_hash_via_hash {
191 impl<CTX> HashStable<CTX> for $t {
193 fn hash_stable<W: StableHasherResult>(&self,
195 hasher: &mut StableHasher<W>) {
196 ::std::hash::Hash::hash(self, hasher);
202 impl_stable_hash_via_hash!(i8);
203 impl_stable_hash_via_hash!(i16);
204 impl_stable_hash_via_hash!(i32);
205 impl_stable_hash_via_hash!(i64);
206 impl_stable_hash_via_hash!(isize);
208 impl_stable_hash_via_hash!(u8);
209 impl_stable_hash_via_hash!(u16);
210 impl_stable_hash_via_hash!(u32);
211 impl_stable_hash_via_hash!(u64);
212 impl_stable_hash_via_hash!(usize);
214 impl_stable_hash_via_hash!(u128);
215 impl_stable_hash_via_hash!(i128);
217 impl_stable_hash_via_hash!(char);
218 impl_stable_hash_via_hash!(());
220 impl<CTX> HashStable<CTX> for f32 {
221 fn hash_stable<W: StableHasherResult>(&self,
223 hasher: &mut StableHasher<W>) {
224 let val: u32 = unsafe {
225 ::std::mem::transmute(*self)
227 val.hash_stable(ctx, hasher);
231 impl<CTX> HashStable<CTX> for f64 {
232 fn hash_stable<W: StableHasherResult>(&self,
234 hasher: &mut StableHasher<W>) {
235 let val: u64 = unsafe {
236 ::std::mem::transmute(*self)
238 val.hash_stable(ctx, hasher);
242 impl<T1: HashStable<CTX>, T2: HashStable<CTX>, CTX> HashStable<CTX> for (T1, T2) {
243 fn hash_stable<W: StableHasherResult>(&self,
245 hasher: &mut StableHasher<W>) {
246 self.0.hash_stable(ctx, hasher);
247 self.1.hash_stable(ctx, hasher);
251 impl<T: HashStable<CTX>, CTX> HashStable<CTX> for [T] {
252 default fn hash_stable<W: StableHasherResult>(&self,
254 hasher: &mut StableHasher<W>) {
255 self.len().hash_stable(ctx, hasher);
257 item.hash_stable(ctx, hasher);
262 impl<T: HashStable<CTX>, CTX> HashStable<CTX> for Vec<T> {
264 fn hash_stable<W: StableHasherResult>(&self,
266 hasher: &mut StableHasher<W>) {
267 (&self[..]).hash_stable(ctx, hasher);
271 impl<CTX> HashStable<CTX> for str {
273 fn hash_stable<W: StableHasherResult>(&self,
275 hasher: &mut StableHasher<W>) {
276 self.len().hash(hasher);
277 self.as_bytes().hash(hasher);
281 impl<CTX> HashStable<CTX> for bool {
283 fn hash_stable<W: StableHasherResult>(&self,
285 hasher: &mut StableHasher<W>) {
286 (if *self { 1u8 } else { 0u8 }).hash_stable(ctx, hasher);
291 impl<T, CTX> HashStable<CTX> for Option<T>
292 where T: HashStable<CTX>
295 fn hash_stable<W: StableHasherResult>(&self,
297 hasher: &mut StableHasher<W>) {
298 if let Some(ref value) = *self {
299 1u8.hash_stable(ctx, hasher);
300 value.hash_stable(ctx, hasher);
302 0u8.hash_stable(ctx, hasher);
307 impl<'a, T, CTX> HashStable<CTX> for &'a T
308 where T: HashStable<CTX>
311 fn hash_stable<W: StableHasherResult>(&self,
313 hasher: &mut StableHasher<W>) {
314 (**self).hash_stable(ctx, hasher);
318 impl<T, CTX> HashStable<CTX> for ::std::mem::Discriminant<T> {
320 fn hash_stable<W: StableHasherResult>(&self,
322 hasher: &mut StableHasher<W>) {
323 ::std::hash::Hash::hash(self, hasher);
327 impl<K, V, CTX> HashStable<CTX> for ::std::collections::BTreeMap<K, V>
328 where K: Ord + HashStable<CTX>,
331 fn hash_stable<W: StableHasherResult>(&self,
333 hasher: &mut StableHasher<W>) {
334 self.len().hash_stable(ctx, hasher);
336 k.hash_stable(ctx, hasher);
337 v.hash_stable(ctx, hasher);
342 impl<T, CTX> HashStable<CTX> for ::std::collections::BTreeSet<T>
343 where T: Ord + HashStable<CTX>,
345 fn hash_stable<W: StableHasherResult>(&self,
347 hasher: &mut StableHasher<W>) {
348 self.len().hash_stable(ctx, hasher);
350 v.hash_stable(ctx, hasher);
355 impl<I: ::indexed_vec::Idx, T, CTX> HashStable<CTX> for ::indexed_vec::IndexVec<I, T>
356 where T: HashStable<CTX>,
358 fn hash_stable<W: StableHasherResult>(&self,
360 hasher: &mut StableHasher<W>) {
361 self.len().hash_stable(ctx, hasher);
363 v.hash_stable(ctx, hasher);