408 lines
12 KiB
Rust
408 lines
12 KiB
Rust
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use std::hash::{Hash, Hasher};
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use std::marker::PhantomData;
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use std::mem;
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use blake2b::Blake2bHasher;
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use rustc_serialize::leb128;
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fn write_unsigned_leb128_to_buf(buf: &mut [u8; 16], value: u64) -> usize {
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leb128::write_unsigned_leb128_to(value as u128, |i, v| buf[i] = v)
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}
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fn write_signed_leb128_to_buf(buf: &mut [u8; 16], value: i64) -> usize {
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leb128::write_signed_leb128_to(value as i128, |i, v| buf[i] = v)
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}
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/// When hashing something that ends up affecting properties like symbol names. We
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/// want these symbol names to be calculated independent of other factors like
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/// what architecture you're compiling *from*.
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///
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/// The hashing just uses the standard `Hash` trait, but the implementations of
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/// `Hash` for the `usize` and `isize` types are *not* architecture independent
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/// (e.g. they has 4 or 8 bytes). As a result we want to avoid `usize` and
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/// `isize` completely when hashing.
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///
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/// To do that, we encode all integers to be hashed with some
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/// arch-independent encoding.
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///
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/// At the moment, we pass i8/u8 straight through and encode
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/// all other integers using leb128.
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///
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/// This hasher currently always uses the stable Blake2b algorithm
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/// and allows for variable output lengths through its type
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/// parameter.
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pub struct StableHasher<W> {
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state: Blake2bHasher,
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bytes_hashed: u64,
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width: PhantomData<W>,
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}
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impl<W: StableHasherResult> ::std::fmt::Debug for StableHasher<W> {
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fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
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write!(f, "{:?}", self.state)
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}
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}
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pub trait StableHasherResult: Sized {
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fn finish(hasher: StableHasher<Self>) -> Self;
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}
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impl<W: StableHasherResult> StableHasher<W> {
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pub fn new() -> Self {
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StableHasher {
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state: Blake2bHasher::new(mem::size_of::<W>(), &[]),
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bytes_hashed: 0,
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width: PhantomData,
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}
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}
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pub fn finish(self) -> W {
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W::finish(self)
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}
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}
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impl StableHasherResult for [u8; 20] {
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fn finish(mut hasher: StableHasher<Self>) -> Self {
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let mut result: [u8; 20] = [0; 20];
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result.copy_from_slice(hasher.state.finalize());
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result
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}
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}
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impl StableHasherResult for u64 {
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fn finish(mut hasher: StableHasher<Self>) -> Self {
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hasher.state.finalize();
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hasher.state.finish()
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}
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}
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impl<W> StableHasher<W> {
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#[inline]
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pub fn finalize(&mut self) -> &[u8] {
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self.state.finalize()
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}
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#[inline]
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pub fn bytes_hashed(&self) -> u64 {
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self.bytes_hashed
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}
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#[inline]
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fn write_uleb128(&mut self, value: u64) {
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let mut buf = [0; 16];
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let len = write_unsigned_leb128_to_buf(&mut buf, value);
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self.state.write(&buf[..len]);
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self.bytes_hashed += len as u64;
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}
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#[inline]
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fn write_ileb128(&mut self, value: i64) {
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let mut buf = [0; 16];
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let len = write_signed_leb128_to_buf(&mut buf, value);
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self.state.write(&buf[..len]);
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self.bytes_hashed += len as u64;
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}
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}
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// For the non-u8 integer cases we leb128 encode them first. Because small
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// integers dominate, this significantly and cheaply reduces the number of
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// bytes hashed, which is good because blake2b is expensive.
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impl<W> Hasher for StableHasher<W> {
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fn finish(&self) -> u64 {
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panic!("use StableHasher::finish instead");
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}
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#[inline]
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fn write(&mut self, bytes: &[u8]) {
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self.state.write(bytes);
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self.bytes_hashed += bytes.len() as u64;
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}
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#[inline]
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fn write_u8(&mut self, i: u8) {
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self.state.write_u8(i);
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self.bytes_hashed += 1;
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}
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#[inline]
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fn write_u16(&mut self, i: u16) {
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self.write_uleb128(i as u64);
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}
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#[inline]
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fn write_u32(&mut self, i: u32) {
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self.write_uleb128(i as u64);
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}
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#[inline]
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fn write_u64(&mut self, i: u64) {
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self.write_uleb128(i);
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}
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#[inline]
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fn write_usize(&mut self, i: usize) {
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self.write_uleb128(i as u64);
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}
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#[inline]
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fn write_i8(&mut self, i: i8) {
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self.state.write_i8(i);
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self.bytes_hashed += 1;
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}
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#[inline]
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fn write_i16(&mut self, i: i16) {
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self.write_ileb128(i as i64);
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}
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#[inline]
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fn write_i32(&mut self, i: i32) {
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self.write_ileb128(i as i64);
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}
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#[inline]
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fn write_i64(&mut self, i: i64) {
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self.write_ileb128(i);
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}
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#[inline]
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fn write_isize(&mut self, i: isize) {
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self.write_ileb128(i as i64);
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}
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}
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/// Something that implements `HashStable<CTX>` can be hashed in a way that is
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/// stable across multiple compiliation sessions.
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pub trait HashStable<CTX> {
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fn hash_stable<W: StableHasherResult>(&self,
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hcx: &mut CTX,
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hasher: &mut StableHasher<W>);
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}
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// Implement HashStable by just calling `Hash::hash()`. This works fine for
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// self-contained values that don't depend on the hashing context `CTX`.
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macro_rules! impl_stable_hash_via_hash {
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($t:ty) => (
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impl<CTX> HashStable<CTX> for $t {
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#[inline]
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fn hash_stable<W: StableHasherResult>(&self,
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_: &mut CTX,
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hasher: &mut StableHasher<W>) {
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::std::hash::Hash::hash(self, hasher);
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}
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}
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);
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}
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impl_stable_hash_via_hash!(i8);
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impl_stable_hash_via_hash!(i16);
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impl_stable_hash_via_hash!(i32);
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impl_stable_hash_via_hash!(i64);
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impl_stable_hash_via_hash!(isize);
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impl_stable_hash_via_hash!(u8);
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impl_stable_hash_via_hash!(u16);
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impl_stable_hash_via_hash!(u32);
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impl_stable_hash_via_hash!(u64);
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impl_stable_hash_via_hash!(usize);
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impl_stable_hash_via_hash!(u128);
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impl_stable_hash_via_hash!(i128);
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impl_stable_hash_via_hash!(char);
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impl_stable_hash_via_hash!(());
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impl<CTX> HashStable<CTX> for f32 {
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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let val: u32 = unsafe {
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::std::mem::transmute(*self)
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};
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val.hash_stable(ctx, hasher);
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}
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}
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impl<CTX> HashStable<CTX> for f64 {
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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let val: u64 = unsafe {
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::std::mem::transmute(*self)
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};
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val.hash_stable(ctx, hasher);
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}
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}
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impl<T1: HashStable<CTX>, CTX> HashStable<CTX> for (T1,) {
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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self.0.hash_stable(ctx, hasher);
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}
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}
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impl<T1: HashStable<CTX>, T2: HashStable<CTX>, CTX> HashStable<CTX> for (T1, T2) {
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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self.0.hash_stable(ctx, hasher);
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self.1.hash_stable(ctx, hasher);
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}
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}
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impl<T: HashStable<CTX>, CTX> HashStable<CTX> for [T] {
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default fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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self.len().hash_stable(ctx, hasher);
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for item in self {
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item.hash_stable(ctx, hasher);
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}
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}
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}
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impl<T: HashStable<CTX>, CTX> HashStable<CTX> for Vec<T> {
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#[inline]
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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(&self[..]).hash_stable(ctx, hasher);
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}
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}
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impl<T: HashStable<CTX>, CTX> HashStable<CTX> for ::std::rc::Rc<T> {
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#[inline]
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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(**self).hash_stable(ctx, hasher);
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}
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}
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impl<T: HashStable<CTX>, CTX> HashStable<CTX> for ::std::sync::Arc<T> {
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#[inline]
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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(**self).hash_stable(ctx, hasher);
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}
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}
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impl<CTX> HashStable<CTX> for str {
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#[inline]
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fn hash_stable<W: StableHasherResult>(&self,
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_: &mut CTX,
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hasher: &mut StableHasher<W>) {
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self.len().hash(hasher);
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self.as_bytes().hash(hasher);
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}
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}
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impl<CTX> HashStable<CTX> for String {
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#[inline]
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fn hash_stable<W: StableHasherResult>(&self,
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hcx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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(&self[..]).hash_stable(hcx, hasher);
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}
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}
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impl<CTX> HashStable<CTX> for bool {
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#[inline]
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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(if *self { 1u8 } else { 0u8 }).hash_stable(ctx, hasher);
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}
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}
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impl<T, CTX> HashStable<CTX> for Option<T>
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where T: HashStable<CTX>
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{
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#[inline]
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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if let Some(ref value) = *self {
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1u8.hash_stable(ctx, hasher);
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value.hash_stable(ctx, hasher);
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} else {
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0u8.hash_stable(ctx, hasher);
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}
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}
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}
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impl<'a, T, CTX> HashStable<CTX> for &'a T
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where T: HashStable<CTX>
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{
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#[inline]
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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(**self).hash_stable(ctx, hasher);
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}
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}
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impl<T, CTX> HashStable<CTX> for ::std::mem::Discriminant<T> {
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#[inline]
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fn hash_stable<W: StableHasherResult>(&self,
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_: &mut CTX,
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hasher: &mut StableHasher<W>) {
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::std::hash::Hash::hash(self, hasher);
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}
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}
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impl<K, V, CTX> HashStable<CTX> for ::std::collections::BTreeMap<K, V>
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where K: Ord + HashStable<CTX>,
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V: HashStable<CTX>,
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{
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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self.len().hash_stable(ctx, hasher);
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for (k, v) in self {
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k.hash_stable(ctx, hasher);
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v.hash_stable(ctx, hasher);
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}
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}
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}
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impl<T, CTX> HashStable<CTX> for ::std::collections::BTreeSet<T>
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where T: Ord + HashStable<CTX>,
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{
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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self.len().hash_stable(ctx, hasher);
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for v in self {
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v.hash_stable(ctx, hasher);
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}
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}
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}
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impl<I: ::indexed_vec::Idx, T, CTX> HashStable<CTX> for ::indexed_vec::IndexVec<I, T>
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where T: HashStable<CTX>,
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{
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fn hash_stable<W: StableHasherResult>(&self,
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ctx: &mut CTX,
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hasher: &mut StableHasher<W>) {
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self.len().hash_stable(ctx, hasher);
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for v in &self.raw {
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v.hash_stable(ctx, hasher);
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}
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}
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}
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