-
Notifications
You must be signed in to change notification settings - Fork 12.8k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
The standard implementations of Hasher have architecture-dependent results when hashing integers. This causes problems when the hashes are stored within metadata - metadata written by one host architecture can't be read by another. To fix that, implement an architecture-independent StableHasher and use it in all places an architecture-independent hasher is needed. Fixes #38177.
- Loading branch information
Showing
14 changed files
with
269 additions
and
229 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,176 @@ | ||
| // Copyright 2016 The Rust Project Developers. See the COPYRIGHT | ||
| // file at the top-level directory of this distribution and at | ||
| // http://rust-lang.org/COPYRIGHT. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
| // option. This file may not be copied, modified, or distributed | ||
| // except according to those terms. | ||
|
|
||
| use std::hash::Hasher; | ||
| use std::marker::PhantomData; | ||
| use std::mem; | ||
| use blake2b::Blake2bHasher; | ||
| use rustc_serialize::leb128; | ||
|
|
||
| fn write_unsigned_leb128_to_buf(buf: &mut [u8; 16], value: u64) -> usize { | ||
| leb128::write_unsigned_leb128_to(value, |i, v| buf[i] = v) | ||
| } | ||
|
|
||
| fn write_signed_leb128_to_buf(buf: &mut [u8; 16], value: i64) -> usize { | ||
| leb128::write_signed_leb128_to(value, |i, v| buf[i] = v) | ||
| } | ||
|
|
||
| /// When hashing something that ends up affecting properties like symbol names. We | ||
| /// want these symbol names to be calculated independent of other factors like | ||
| /// what architecture you're compiling *from*. | ||
| /// | ||
| /// The hashing just uses the standard `Hash` trait, but the implementations of | ||
| /// `Hash` for the `usize` and `isize` types are *not* architecture independent | ||
| /// (e.g. they has 4 or 8 bytes). As a result we want to avoid `usize` and | ||
| /// `isize` completely when hashing. | ||
| /// | ||
| /// To do that, we encode all integers to be hashed with some | ||
| /// arch-independent encoding. | ||
| /// | ||
| /// At the moment, we pass i8/u8 straight through and encode | ||
| /// all other integers using leb128. | ||
| /// | ||
| /// This hasher currently always uses the stable Blake2b algorithm | ||
| /// and allows for variable output lengths through its type | ||
| /// parameter. | ||
| #[derive(Debug)] | ||
| pub struct StableHasher<W> { | ||
| state: Blake2bHasher, | ||
| bytes_hashed: u64, | ||
| width: PhantomData<W>, | ||
| } | ||
|
|
||
| pub trait StableHasherResult: Sized { | ||
| fn finish(hasher: StableHasher<Self>) -> Self; | ||
| } | ||
|
|
||
| impl<W: StableHasherResult> StableHasher<W> { | ||
| pub fn new() -> Self { | ||
| StableHasher { | ||
| state: Blake2bHasher::new(mem::size_of::<W>(), &[]), | ||
| bytes_hashed: 0, | ||
| width: PhantomData, | ||
| } | ||
| } | ||
|
|
||
| pub fn finish(self) -> W { | ||
| W::finish(self) | ||
| } | ||
| } | ||
|
|
||
| impl StableHasherResult for [u8; 20] { | ||
| fn finish(mut hasher: StableHasher<Self>) -> Self { | ||
| let mut result: [u8; 20] = [0; 20]; | ||
| result.copy_from_slice(hasher.state.finalize()); | ||
| result | ||
| } | ||
| } | ||
|
|
||
| impl StableHasherResult for u64 { | ||
| fn finish(mut hasher: StableHasher<Self>) -> Self { | ||
| hasher.state.finalize(); | ||
| hasher.state.finish() | ||
| } | ||
| } | ||
|
|
||
| impl<W> StableHasher<W> { | ||
| #[inline] | ||
| pub fn finalize(&mut self) -> &[u8] { | ||
| self.state.finalize() | ||
| } | ||
|
|
||
| #[inline] | ||
| pub fn bytes_hashed(&self) -> u64 { | ||
| self.bytes_hashed | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write_uleb128(&mut self, value: u64) { | ||
| let mut buf = [0; 16]; | ||
| let len = write_unsigned_leb128_to_buf(&mut buf, value); | ||
| self.state.write(&buf[..len]); | ||
| self.bytes_hashed += len as u64; | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write_ileb128(&mut self, value: i64) { | ||
| let mut buf = [0; 16]; | ||
| let len = write_signed_leb128_to_buf(&mut buf, value); | ||
| self.state.write(&buf[..len]); | ||
| self.bytes_hashed += len as u64; | ||
| } | ||
| } | ||
|
|
||
| // For the non-u8 integer cases we leb128 encode them first. Because small | ||
| // integers dominate, this significantly and cheaply reduces the number of | ||
| // bytes hashed, which is good because blake2b is expensive. | ||
| impl<W> Hasher for StableHasher<W> { | ||
| fn finish(&self) -> u64 { | ||
| panic!("use StableHasher::finish instead"); | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write(&mut self, bytes: &[u8]) { | ||
| self.state.write(bytes); | ||
| self.bytes_hashed += bytes.len() as u64; | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write_u8(&mut self, i: u8) { | ||
| self.state.write_u8(i); | ||
| self.bytes_hashed += 1; | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write_u16(&mut self, i: u16) { | ||
| self.write_uleb128(i as u64); | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write_u32(&mut self, i: u32) { | ||
| self.write_uleb128(i as u64); | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write_u64(&mut self, i: u64) { | ||
| self.write_uleb128(i); | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write_usize(&mut self, i: usize) { | ||
| self.write_uleb128(i as u64); | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write_i8(&mut self, i: i8) { | ||
| self.state.write_i8(i); | ||
| self.bytes_hashed += 1; | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write_i16(&mut self, i: i16) { | ||
| self.write_ileb128(i as i64); | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write_i32(&mut self, i: i32) { | ||
| self.write_ileb128(i as i64); | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write_i64(&mut self, i: i64) { | ||
| self.write_ileb128(i); | ||
| } | ||
|
|
||
| #[inline] | ||
| fn write_isize(&mut self, i: isize) { | ||
| self.write_ileb128(i as i64); | ||
| } | ||
| } |
Oops, something went wrong.