Auto merge of #8233 - ehuss:siphasher, r=alexcrichton

Move SipHasher to an isolated module.

This allows removing the blanket `#![allow(deprecated)]` sprinkled whenever it is used.

We could alternatively use the [siphasher](https://crates.io/crates/siphasher) crate, but I don't think it is necessary at this time.

src/cargo/core/compiler/context/compilation_files.rs

@@ -1,7 +1,7 @@
 use std::collections::HashMap;
 use std::env;
 use std::fmt;
-use std::hash::{Hash, Hasher, SipHasher};
+use std::hash::{Hash, Hasher};
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 
@@ -11,7 +11,7 @@ use log::info;
 use super::{BuildContext, CompileKind, Context, FileFlavor, Layout};
 use crate::core::compiler::{CompileMode, CompileTarget, CrateType, FileType, Unit};
 use crate::core::{Target, TargetKind, Workspace};
-use crate::util::{self, CargoResult};
+use crate::util::{self, CargoResult, StableHasher};
 
 /// The `Metadata` is a hash used to make unique file names for each unit in a
 /// build. It is also use for symbol mangling.
@@ -481,7 +481,7 @@ fn compute_metadata(
     if !should_use_metadata(bcx, unit) {
         return None;
     }
-    let mut hasher = SipHasher::new();
+    let mut hasher = StableHasher::new();
 
     // This is a generic version number that can be changed to make
     // backwards-incompatible changes to any file structures in the output
@@ -556,7 +556,7 @@ fn compute_metadata(
     Some(Metadata(hasher.finish()))
 }
 
-fn hash_rustc_version(bcx: &BuildContext<'_, '_>, hasher: &mut SipHasher) {
+fn hash_rustc_version(bcx: &BuildContext<'_, '_>, hasher: &mut StableHasher) {
     let vers = &bcx.rustc().version;
     if vers.pre.is_empty() || bcx.config.cli_unstable().separate_nightlies {
         // For stable, keep the artifacts separate. This helps if someone is

src/cargo/core/compiler/context/mod.rs

@@ -1,4 +1,3 @@
-#![allow(deprecated)]
 use std::collections::{BTreeSet, HashMap, HashSet};
 use std::path::PathBuf;
 use std::sync::{Arc, Mutex};

src/cargo/util/hasher.rs

@@ -0,0 +1,24 @@
+//! Implementation of a hasher that produces the same values across releases.
+//!
+//! The hasher should be fast and have a low chance of collisions (but is not
+//! sufficient for cryptographic purposes).
+#![allow(deprecated)]
+
+use std::hash::{Hasher, SipHasher};
+
+pub struct StableHasher(SipHasher);
+
+impl StableHasher {
+    pub fn new() -> StableHasher {
+        StableHasher(SipHasher::new())
+    }
+}
+
+impl Hasher for StableHasher {
+    fn finish(&self) -> u64 {
+        self.0.finish()
+    }
+    fn write(&mut self, bytes: &[u8]) {
+        self.0.write(bytes)
+    }
+}

src/cargo/util/hex.rs

@@ -1,7 +1,6 @@
-#![allow(deprecated)]
+use super::StableHasher;
-
 use std::fs::File;
-use std::hash::{Hash, Hasher, SipHasher};
+use std::hash::{Hash, Hasher};
 use std::io::Read;
 
 pub fn to_hex(num: u64) -> String {
@@ -18,13 +17,13 @@ pub fn to_hex(num: u64) -> String {
 }
 
 pub fn hash_u64<H: Hash>(hashable: H) -> u64 {
-    let mut hasher = SipHasher::new();
+    let mut hasher = StableHasher::new();
     hashable.hash(&mut hasher);
     hasher.finish()
 }
 
 pub fn hash_u64_file(mut file: &File) -> std::io::Result<u64> {
-    let mut hasher = SipHasher::new_with_keys(0, 0);
+    let mut hasher = StableHasher::new();
     let mut buf = [0; 64 * 1024];
     loop {
         let n = file.read(&mut buf)?;

src/cargo/util/mod.rs

@@ -9,6 +9,7 @@ pub use self::errors::{CargoResult, CargoResultExt, CliResult, Test};
 pub use self::errors::{CargoTestError, CliError, ProcessError};
 pub use self::flock::{FileLock, Filesystem};
 pub use self::graph::Graph;
+pub use self::hasher::StableHasher;
 pub use self::hex::{hash_u64, short_hash, to_hex};
 pub use self::into_url::IntoUrl;
 pub use self::into_url_with_base::IntoUrlWithBase;
@@ -39,6 +40,7 @@ pub mod diagnostic_server;
 pub mod errors;
 mod flock;
 pub mod graph;
+mod hasher;
 pub mod hex;
 pub mod important_paths;
 pub mod into_url;

src/cargo/util/rustc.rs

@@ -1,8 +1,6 @@
-#![allow(deprecated)] // for SipHasher
-
 use std::collections::hash_map::{Entry, HashMap};
 use std::env;
-use std::hash::{Hash, Hasher, SipHasher};
+use std::hash::{Hash, Hasher};
 use std::path::{Path, PathBuf};
 use std::sync::Mutex;
 
@@ -11,7 +9,7 @@ use serde::{Deserialize, Serialize};
 
 use crate::core::InternedString;
 use crate::util::paths;
-use crate::util::{self, profile, CargoResult, CargoResultExt, ProcessBuilder};
+use crate::util::{self, profile, CargoResult, CargoResultExt, ProcessBuilder, StableHasher};
 
 /// Information on the `rustc` executable
 #[derive(Debug)]
@@ -222,7 +220,7 @@ impl Drop for Cache {
 }
 
 fn rustc_fingerprint(path: &Path, rustup_rustc: &Path) -> CargoResult<u64> {
-    let mut hasher = SipHasher::new();
+    let mut hasher = StableHasher::new();
 
     let path = paths::resolve_executable(path)?;
     path.hash(&mut hasher);
@@ -266,7 +264,7 @@ fn rustc_fingerprint(path: &Path, rustup_rustc: &Path) -> CargoResult<u64> {
 }
 
 fn process_fingerprint(cmd: &ProcessBuilder) -> u64 {
-    let mut hasher = SipHasher::new();
+    let mut hasher = StableHasher::new();
     cmd.get_args().hash(&mut hasher);
     let mut env = cmd.get_envs().iter().collect::<Vec<_>>();
     env.sort_unstable();