Move raw bytes handling to Encoder/Decoder.

compiler/rustc_data_structures/src/fingerprint.rs

@@ -1,7 +1,7 @@
 use crate::stable_hasher;
 use rustc_serialize::{
     opaque::{self, EncodeResult, FileEncodeResult},
-    Decodable, Encodable,
+    Decodable, Decoder, Encodable, Encoder,
 };
 use std::hash::{Hash, Hasher};
 use std::mem::{self, MaybeUninit};
@@ -158,7 +158,7 @@ impl<E: rustc_serialize::Encoder> FingerprintEncoder for 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);
+        self.emit_raw_bytes(&bytes)?;
         Ok(())
     }
 }

compiler/rustc_incremental/src/persist/file_format.rs

@@ -15,6 +15,7 @@ use std::io::{self, Read};
 use std::path::Path;
 
 use rustc_serialize::opaque::{FileEncodeResult, FileEncoder};
+use rustc_serialize::Encoder;
 
 /// The first few bytes of files generated by incremental compilation.
 const FILE_MAGIC: &[u8] = b"RSIC";

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -2073,10 +2073,10 @@ pub(super) fn encode_metadata(tcx: TyCtxt<'_>) -> EncodedMetadata {
 
 fn encode_metadata_impl(tcx: TyCtxt<'_>) -> EncodedMetadata {
     let mut encoder = opaque::Encoder::new(vec![]);
-    encoder.emit_raw_bytes(METADATA_HEADER);
+    encoder.emit_raw_bytes(METADATA_HEADER).unwrap();
 
     // Will be filled with the root position after encoding everything.
-    encoder.emit_raw_bytes(&[0, 0, 0, 0]);
+    encoder.emit_raw_bytes(&[0, 0, 0, 0]).unwrap();
 
     let source_map_files = tcx.sess.source_map().files();
     let source_file_cache = (source_map_files[0].clone(), 0);

compiler/rustc_metadata/src/rmeta/table.rs

@@ -2,6 +2,7 @@ use crate::rmeta::*;
 
 use rustc_index::vec::Idx;
 use rustc_serialize::opaque::Encoder;
+use rustc_serialize::Encoder as _;
 use std::convert::TryInto;
 use std::marker::PhantomData;
 use std::num::NonZeroUsize;
@@ -172,7 +173,7 @@ where
 
     pub(crate) fn encode(&self, buf: &mut Encoder) -> Lazy<Table<I, T>> {
         let pos = buf.position();
-        buf.emit_raw_bytes(&self.bytes);
+        buf.emit_raw_bytes(&self.bytes).unwrap();
         Lazy::from_position_and_meta(NonZeroUsize::new(pos as usize).unwrap(), self.bytes.len())
     }
 }

compiler/rustc_serialize/src/opaque.rs

@@ -1,5 +1,5 @@
 use crate::leb128::{self, max_leb128_len};
-use crate::serialize;
+use crate::serialize::{self, Decoder as _, Encoder as _};
 use std::borrow::Cow;
 use std::fs::File;
 use std::io::{self, Write};
@@ -30,11 +30,6 @@ impl Encoder {
     pub fn position(&self) -> usize {
         self.data.len()
     }
-
-    #[inline]
-    pub fn emit_raw_bytes(&mut self, s: &[u8]) {
-        self.data.extend_from_slice(s);
-    }
 }
 
 macro_rules! write_leb128 {
@@ -154,7 +149,13 @@ impl serialize::Encoder for Encoder {
     #[inline]
     fn emit_str(&mut self, v: &str) -> EncodeResult {
         self.emit_usize(v.len())?;
-        self.emit_raw_bytes(v.as_bytes());
+        self.emit_raw_bytes(v.as_bytes())?;
+        Ok(())
+    }
+
+    #[inline]
+    fn emit_raw_bytes(&mut self, s: &[u8]) -> EncodeResult {
+        self.data.extend_from_slice(s);
         Ok(())
     }
 }
@@ -208,11 +209,6 @@ impl FileEncoder {
         self.flushed + self.buffered
     }
 
-    #[inline]
-    pub fn emit_raw_bytes(&mut self, s: &[u8]) -> FileEncodeResult {
-        self.write_all(s)
-    }
-
     pub fn flush(&mut self) -> FileEncodeResult {
         // This is basically a copy of `BufWriter::flush`. If `BufWriter` ever
         // offers a raw buffer access API, we can use it, and remove this.
@@ -508,6 +504,11 @@ impl serialize::Encoder for FileEncoder {
         self.emit_usize(v.len())?;
         self.emit_raw_bytes(v.as_bytes())
     }
+
+    #[inline]
+    fn emit_raw_bytes(&mut self, s: &[u8]) -> FileEncodeResult {
+        self.write_all(s)
+    }
 }
 
 // -----------------------------------------------------------------------------
@@ -539,26 +540,6 @@ impl<'a> Decoder<'a> {
     pub fn advance(&mut self, bytes: usize) {
         self.position += bytes;
     }
-
-    #[inline]
-    pub fn read_raw_bytes(&mut self, s: &mut [MaybeUninit<u8>]) -> Result<(), String> {
-        let start = self.position;
-        let end = start + s.len();
-        assert!(end <= self.data.len());
-
-        // SAFETY: Both `src` and `dst` point to at least `s.len()` elements:
-        // `src` points to at least `s.len()` elements by above assert, and
-        // `dst` points to `s.len()` elements by derivation from `s`.
-        unsafe {
-            let src = self.data.as_ptr().add(start);
-            let dst = s.as_mut_ptr() as *mut u8;
-            ptr::copy_nonoverlapping(src, dst, s.len());
-        }
-
-        self.position = end;
-
-        Ok(())
-    }
 }
 
 macro_rules! read_leb128 {
@@ -677,6 +658,26 @@ impl<'a> serialize::Decoder for Decoder<'a> {
     fn error(&mut self, err: &str) -> Self::Error {
         err.to_string()
     }
+
+    #[inline]
+    fn read_raw_bytes(&mut self, s: &mut [MaybeUninit<u8>]) -> Result<(), String> {
+        let start = self.position;
+        let end = start + s.len();
+        assert!(end <= self.data.len());
+
+        // SAFETY: Both `src` and `dst` point to at least `s.len()` elements:
+        // `src` points to at least `s.len()` elements by above assert, and
+        // `dst` points to `s.len()` elements by derivation from `s`.
+        unsafe {
+            let src = self.data.as_ptr().add(start);
+            let dst = s.as_mut_ptr() as *mut u8;
+            ptr::copy_nonoverlapping(src, dst, s.len());
+        }
+
+        self.position = end;
+
+        Ok(())
+    }
 }
 
 // Specializations for contiguous byte sequences follow. The default implementations for slices
@@ -689,7 +690,7 @@ impl<'a> serialize::Decoder for Decoder<'a> {
 impl serialize::Encodable<Encoder> for [u8] {
     fn encode(&self, e: &mut Encoder) -> EncodeResult {
         serialize::Encoder::emit_usize(e, self.len())?;
-        e.emit_raw_bytes(self);
+        e.emit_raw_bytes(self)?;
         Ok(())
     }
 }

compiler/rustc_serialize/src/serialize.rs

@@ -7,6 +7,7 @@ Core encoding and decoding interfaces.
 use std::borrow::Cow;
 use std::cell::{Cell, RefCell};
 use std::marker::PhantomData;
+use std::mem::MaybeUninit;
 use std::path;
 use std::rc::Rc;
 use std::sync::Arc;
@@ -200,6 +201,14 @@ pub trait Encoder {
     {
         f(self)
     }
+
+    #[inline]
+    fn emit_raw_bytes(&mut self, s: &[u8]) -> Result<(), Self::Error> {
+        for &c in s.iter() {
+            self.emit_u8(c)?;
+        }
+        Ok(())
+    }
 }
 
 pub trait Decoder {
@@ -377,6 +386,15 @@ pub trait Decoder {
 
     // Failure
     fn error(&mut self, err: &str) -> Self::Error;
+
+    #[inline]
+    fn read_raw_bytes(&mut self, s: &mut [MaybeUninit<u8>]) -> Result<(), Self::Error> {
+        for c in s.iter_mut() {
+            let h = self.read_u8()?;
+            unsafe { *c.as_mut_ptr() = h };
+        }
+        Ok(())
+    }
 }
 
 /// Trait for types that can be serialized