Allow for reading raw bytes from rustc_serialize::Decoder without unsafe code.

[rust.git] / compiler / rustc_data_structures / src / fingerprint.rs

diff --git a/compiler/rustc_data_structures/src/fingerprint.rs b/compiler/rustc_data_structures/src/fingerprint.rs
index 681b49e2ea97bfaca49751da7d8ab1d79335ad1b..c0c0e7be3ca85cb36b95f4a9e6c933d08c833b65 100644 (file)
--- a/compiler/rustc_data_structures/src/fingerprint.rs
+++ b/compiler/rustc_data_structures/src/fingerprint.rs
@@ -1,10 +1,7 @@
 use crate::stable_hasher;
-use rustc_serialize::{
-    opaque::{self, EncodeResult, FileEncodeResult},
-    Decodable, Encodable,
-};
+use rustc_serialize::{Decodable, Encodable};
+use std::convert::TryInto;
 use std::hash::{Hash, Hasher};
-use std::mem::{self, MaybeUninit};
 
 #[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Copy)]
 #[repr(C)]
@@ -64,14 +61,27 @@ pub fn to_hex(&self) -> String {
         format!("{:x}{:x}", self.0, self.1)
     }
 
-    pub fn decode_opaque(decoder: &mut opaque::Decoder<'_>) -> Result<Fingerprint, String> {
-        let mut bytes: [MaybeUninit<u8>; 16] = MaybeUninit::uninit_array();
+    #[inline]
+    pub fn to_le_bytes(&self) -> [u8; 16] {
+        // This seems to optimize to the same machine code as
+        // `unsafe { mem::transmute(*k) }`. Well done, LLVM! :)
+        let mut result = [0u8; 16];
+
+        let first_half: &mut [u8; 8] = (&mut result[0..8]).try_into().unwrap();
+        *first_half = self.0.to_le_bytes();
 
-        decoder.read_raw_bytes(&mut bytes)?;
+        let second_half: &mut [u8; 8] = (&mut result[8..16]).try_into().unwrap();
+        *second_half = self.1.to_le_bytes();
 
-        let [l, r]: [u64; 2] = unsafe { mem::transmute(bytes) };
+        result
+    }
 
-        Ok(Fingerprint(u64::from_le(l), u64::from_le(r)))
+    #[inline]
+    pub fn from_le_bytes(bytes: [u8; 16]) -> Fingerprint {
+        Fingerprint(
+            u64::from_le_bytes(bytes[0..8].try_into().unwrap()),
+            u64::from_le_bytes(bytes[8..16].try_into().unwrap()),
+        )
     }
 }
 
@@ -130,55 +140,19 @@ fn finish(hasher: stable_hasher::StableHasher) -> Self {
 impl_stable_hash_via_hash!(Fingerprint);
 
 impl<E: rustc_serialize::Encoder> Encodable<E> for Fingerprint {
+    #[inline]
     fn encode(&self, s: &mut E) -> Result<(), E::Error> {
-        s.encode_fingerprint(self)
+        s.emit_raw_bytes(&self.to_le_bytes()[..])?;
+        Ok(())
     }
 }
 
 impl<D: rustc_serialize::Decoder> Decodable<D> for Fingerprint {
+    #[inline]
     fn decode(d: &mut D) -> Result<Self, D::Error> {
-        d.decode_fingerprint()
-    }
-}
-
-pub trait FingerprintEncoder: rustc_serialize::Encoder {
-    fn encode_fingerprint(&mut self, f: &Fingerprint) -> Result<(), Self::Error>;
-}
-
-pub trait FingerprintDecoder: rustc_serialize::Decoder {
-    fn decode_fingerprint(&mut self) -> Result<Fingerprint, Self::Error>;
-}
-
-impl<E: rustc_serialize::Encoder> FingerprintEncoder for E {
-    default fn encode_fingerprint(&mut self, _: &Fingerprint) -> Result<(), E::Error> {
-        panic!("Cannot encode `Fingerprint` with `{}`", std::any::type_name::<E>());
-    }
-}
-
-impl FingerprintEncoder for opaque::Encoder {
-    fn encode_fingerprint(&mut self, f: &Fingerprint) -> EncodeResult {
-        let bytes: [u8; 16] = unsafe { mem::transmute([f.0.to_le(), f.1.to_le()]) };
-        self.emit_raw_bytes(&bytes);
-        Ok(())
-    }
-}
-
-impl FingerprintEncoder for opaque::FileEncoder {
-    fn encode_fingerprint(&mut self, f: &Fingerprint) -> FileEncodeResult {
-        let bytes: [u8; 16] = unsafe { mem::transmute([f.0.to_le(), f.1.to_le()]) };
-        self.emit_raw_bytes(&bytes)
-    }
-}
-
-impl<D: rustc_serialize::Decoder> FingerprintDecoder for D {
-    default fn decode_fingerprint(&mut self) -> Result<Fingerprint, D::Error> {
-        panic!("Cannot decode `Fingerprint` with `{}`", std::any::type_name::<D>());
-    }
-}
-
-impl FingerprintDecoder for opaque::Decoder<'_> {
-    fn decode_fingerprint(&mut self) -> Result<Fingerprint, String> {
-        Fingerprint::decode_opaque(self)
+        let mut bytes = [0u8; 16];
+        d.read_raw_bytes_into(&mut bytes[..])?;
+        Ok(Fingerprint::from_le_bytes(bytes))
     }
 }