1 files changed, 469 insertions, 0 deletions
diff --git a/compiler/rustc_serialize/src/serialize.rs b/compiler/rustc_serialize/src/serialize.rs
new file mode 100644
index 000000000..36585b8d7
--- /dev/null
+++ b/compiler/rustc_serialize/src/serialize.rs
@@ -0,0 +1,469 @@
+//! Support code for encoding and decoding types.
+
+/*
+Core encoding and decoding interfaces.
+*/
+
+use std::borrow::Cow;
+use std::cell::{Cell, RefCell};
+use std::marker::PhantomData;
+use std::path;
+use std::rc::Rc;
+use std::sync::Arc;
+
+/// A note about error handling.
+///
+/// Encoders may be fallible, but in practice failure is rare and there are so
+/// many nested calls that typical Rust error handling (via `Result` and `?`)
+/// is pervasive and has non-trivial cost. Instead, impls of this trait must
+/// implement a delayed error handling strategy. If a failure occurs, they
+/// should record this internally, and all subsequent encoding operations can
+/// be processed or ignored, whichever is appropriate. Then they should provide
+/// a `finish` method that finishes up encoding. If the encoder is fallible,
+/// `finish` should return a `Result` that indicates success or failure.
+pub trait Encoder {
+    // Primitive types:
+    fn emit_usize(&mut self, v: usize);
+    fn emit_u128(&mut self, v: u128);
+    fn emit_u64(&mut self, v: u64);
+    fn emit_u32(&mut self, v: u32);
+    fn emit_u16(&mut self, v: u16);
+    fn emit_u8(&mut self, v: u8);
+    fn emit_isize(&mut self, v: isize);
+    fn emit_i128(&mut self, v: i128);
+    fn emit_i64(&mut self, v: i64);
+    fn emit_i32(&mut self, v: i32);
+    fn emit_i16(&mut self, v: i16);
+    fn emit_i8(&mut self, v: i8);
+    fn emit_bool(&mut self, v: bool);
+    fn emit_f64(&mut self, v: f64);
+    fn emit_f32(&mut self, v: f32);
+    fn emit_char(&mut self, v: char);
+    fn emit_str(&mut self, v: &str);
+    fn emit_raw_bytes(&mut self, s: &[u8]);
+
+    // Convenience for the derive macro:
+    fn emit_enum_variant<F>(&mut self, v_id: usize, f: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        self.emit_usize(v_id);
+        f(self);
+    }
+
+    // We put the field index in a const generic to allow the emit_usize to be
+    // compiled into a more efficient form. In practice, the variant index is
+    // known at compile-time, and that knowledge allows much more efficient
+    // codegen than we'd otherwise get. LLVM isn't always able to make the
+    // optimization that would otherwise be necessary here, likely due to the
+    // multiple levels of inlining and const-prop that are needed.
+    #[inline]
+    fn emit_fieldless_enum_variant<const ID: usize>(&mut self) {
+        self.emit_usize(ID)
+    }
+}
+
+// Note: all the methods in this trait are infallible, which may be surprising.
+// They used to be fallible (i.e. return a `Result`) but many of the impls just
+// panicked when something went wrong, and for the cases that didn't the
+// top-level invocation would also just panic on failure. Switching to
+// infallibility made things faster and lots of code a little simpler and more
+// concise.
+pub trait Decoder {
+    // Primitive types:
+    fn read_usize(&mut self) -> usize;
+    fn read_u128(&mut self) -> u128;
+    fn read_u64(&mut self) -> u64;
+    fn read_u32(&mut self) -> u32;
+    fn read_u16(&mut self) -> u16;
+    fn read_u8(&mut self) -> u8;
+    fn read_isize(&mut self) -> isize;
+    fn read_i128(&mut self) -> i128;
+    fn read_i64(&mut self) -> i64;
+    fn read_i32(&mut self) -> i32;
+    fn read_i16(&mut self) -> i16;
+    fn read_i8(&mut self) -> i8;
+    fn read_bool(&mut self) -> bool;
+    fn read_f64(&mut self) -> f64;
+    fn read_f32(&mut self) -> f32;
+    fn read_char(&mut self) -> char;
+    fn read_str(&mut self) -> &str;
+    fn read_raw_bytes(&mut self, len: usize) -> &[u8];
+}
+
+/// Trait for types that can be serialized
+///
+/// This can be implemented using the `Encodable`, `TyEncodable` and
+/// `MetadataEncodable` macros.
+///
+/// * `Encodable` should be used in crates that don't depend on
+///   `rustc_middle`.
+/// * `MetadataEncodable` is used in `rustc_metadata` for types that contain
+///   `rustc_metadata::rmeta::Lazy`.
+/// * `TyEncodable` should be used for types that are only serialized in crate
+///   metadata or the incremental cache. This is most types in `rustc_middle`.
+pub trait Encodable<S: Encoder> {
+    fn encode(&self, s: &mut S);
+}
+
+/// Trait for types that can be deserialized
+///
+/// This can be implemented using the `Decodable`, `TyDecodable` and
+/// `MetadataDecodable` macros.
+///
+/// * `Decodable` should be used in crates that don't depend on
+///   `rustc_middle`.
+/// * `MetadataDecodable` is used in `rustc_metadata` for types that contain
+///   `rustc_metadata::rmeta::Lazy`.
+/// * `TyDecodable` should be used for types that are only serialized in crate
+///   metadata or the incremental cache. This is most types in `rustc_middle`.
+pub trait Decodable<D: Decoder>: Sized {
+    fn decode(d: &mut D) -> Self;
+}
+
+macro_rules! direct_serialize_impls {
+    ($($ty:ident $emit_method:ident $read_method:ident),*) => {
+        $(
+            impl<S: Encoder> Encodable<S> for $ty {
+                fn encode(&self, s: &mut S) {
+                    s.$emit_method(*self);
+                }
+            }
+
+            impl<D: Decoder> Decodable<D> for $ty {
+                fn decode(d: &mut D) -> $ty {
+                    d.$read_method()
+                }
+            }
+        )*
+    }
+}
+
+direct_serialize_impls! {
+    usize emit_usize read_usize,
+    u8 emit_u8 read_u8,
+    u16 emit_u16 read_u16,
+    u32 emit_u32 read_u32,
+    u64 emit_u64 read_u64,
+    u128 emit_u128 read_u128,
+
+    isize emit_isize read_isize,
+    i8 emit_i8 read_i8,
+    i16 emit_i16 read_i16,
+    i32 emit_i32 read_i32,
+    i64 emit_i64 read_i64,
+    i128 emit_i128 read_i128,
+
+    f32 emit_f32 read_f32,
+    f64 emit_f64 read_f64,
+    bool emit_bool read_bool,
+    char emit_char read_char
+}
+
+impl<S: Encoder, T: ?Sized> Encodable<S> for &T
+where
+    T: Encodable<S>,
+{
+    fn encode(&self, s: &mut S) {
+        (**self).encode(s)
+    }
+}
+
+impl<S: Encoder> Encodable<S> for ! {
+    fn encode(&self, _s: &mut S) {
+        unreachable!();
+    }
+}
+
+impl<D: Decoder> Decodable<D> for ! {
+    fn decode(_d: &mut D) -> ! {
+        unreachable!()
+    }
+}
+
+impl<S: Encoder> Encodable<S> for ::std::num::NonZeroU32 {
+    fn encode(&self, s: &mut S) {
+        s.emit_u32(self.get());
+    }
+}
+
+impl<D: Decoder> Decodable<D> for ::std::num::NonZeroU32 {
+    fn decode(d: &mut D) -> Self {
+        ::std::num::NonZeroU32::new(d.read_u32()).unwrap()
+    }
+}
+
+impl<S: Encoder> Encodable<S> for str {
+    fn encode(&self, s: &mut S) {
+        s.emit_str(self);
+    }
+}
+
+impl<S: Encoder> Encodable<S> for String {
+    fn encode(&self, s: &mut S) {
+        s.emit_str(&self[..]);
+    }
+}
+
+impl<D: Decoder> Decodable<D> for String {
+    fn decode(d: &mut D) -> String {
+        d.read_str().to_owned()
+    }
+}
+
+impl<S: Encoder> Encodable<S> for () {
+    fn encode(&self, _s: &mut S) {}
+}
+
+impl<D: Decoder> Decodable<D> for () {
+    fn decode(_: &mut D) -> () {}
+}
+
+impl<S: Encoder, T> Encodable<S> for PhantomData<T> {
+    fn encode(&self, _s: &mut S) {}
+}
+
+impl<D: Decoder, T> Decodable<D> for PhantomData<T> {
+    fn decode(_: &mut D) -> PhantomData<T> {
+        PhantomData
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Box<[T]> {
+    fn decode(d: &mut D) -> Box<[T]> {
+        let v: Vec<T> = Decodable::decode(d);
+        v.into_boxed_slice()
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for Rc<T> {
+    fn encode(&self, s: &mut S) {
+        (**self).encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Rc<T> {
+    fn decode(d: &mut D) -> Rc<T> {
+        Rc::new(Decodable::decode(d))
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for [T] {
+    default fn encode(&self, s: &mut S) {
+        s.emit_usize(self.len());
+        for e in self.iter() {
+            e.encode(s);
+        }
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for Vec<T> {
+    fn encode(&self, s: &mut S) {
+        let slice: &[T] = self;
+        slice.encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Vec<T> {
+    default fn decode(d: &mut D) -> Vec<T> {
+        let len = d.read_usize();
+        // SAFETY: we set the capacity in advance, only write elements, and
+        // only set the length at the end once the writing has succeeded.
+        let mut vec = Vec::with_capacity(len);
+        unsafe {
+            let ptr: *mut T = vec.as_mut_ptr();
+            for i in 0..len {
+                std::ptr::write(ptr.offset(i as isize), Decodable::decode(d));
+            }
+            vec.set_len(len);
+        }
+        vec
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>, const N: usize> Encodable<S> for [T; N] {
+    fn encode(&self, s: &mut S) {
+        let slice: &[T] = self;
+        slice.encode(s);
+    }
+}
+
+impl<D: Decoder, const N: usize> Decodable<D> for [u8; N] {
+    fn decode(d: &mut D) -> [u8; N] {
+        let len = d.read_usize();
+        assert!(len == N);
+        let mut v = [0u8; N];
+        for i in 0..len {
+            v[i] = Decodable::decode(d);
+        }
+        v
+    }
+}
+
+impl<'a, S: Encoder, T: Encodable<S>> Encodable<S> for Cow<'a, [T]>
+where
+    [T]: ToOwned<Owned = Vec<T>>,
+{
+    fn encode(&self, s: &mut S) {
+        let slice: &[T] = self;
+        slice.encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D> + ToOwned> Decodable<D> for Cow<'static, [T]>
+where
+    [T]: ToOwned<Owned = Vec<T>>,
+{
+    fn decode(d: &mut D) -> Cow<'static, [T]> {
+        let v: Vec<T> = Decodable::decode(d);
+        Cow::Owned(v)
+    }
+}
+
+impl<'a, S: Encoder> Encodable<S> for Cow<'a, str> {
+    fn encode(&self, s: &mut S) {
+        let val: &str = self;
+        val.encode(s)
+    }
+}
+
+impl<'a, D: Decoder> Decodable<D> for Cow<'a, str> {
+    fn decode(d: &mut D) -> Cow<'static, str> {
+        let v: String = Decodable::decode(d);
+        Cow::Owned(v)
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for Option<T> {
+    fn encode(&self, s: &mut S) {
+        match *self {
+            None => s.emit_enum_variant(0, |_| {}),
+            Some(ref v) => s.emit_enum_variant(1, |s| v.encode(s)),
+        }
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Option<T> {
+    fn decode(d: &mut D) -> Option<T> {
+        match d.read_usize() {
+            0 => None,
+            1 => Some(Decodable::decode(d)),
+            _ => panic!("Encountered invalid discriminant while decoding `Option`."),
+        }
+    }
+}
+
+impl<S: Encoder, T1: Encodable<S>, T2: Encodable<S>> Encodable<S> for Result<T1, T2> {
+    fn encode(&self, s: &mut S) {
+        match *self {
+            Ok(ref v) => s.emit_enum_variant(0, |s| v.encode(s)),
+            Err(ref v) => s.emit_enum_variant(1, |s| v.encode(s)),
+        }
+    }
+}
+
+impl<D: Decoder, T1: Decodable<D>, T2: Decodable<D>> Decodable<D> for Result<T1, T2> {
+    fn decode(d: &mut D) -> Result<T1, T2> {
+        match d.read_usize() {
+            0 => Ok(T1::decode(d)),
+            1 => Err(T2::decode(d)),
+            _ => panic!("Encountered invalid discriminant while decoding `Result`."),
+        }
+    }
+}
+
+macro_rules! peel {
+    ($name:ident, $($other:ident,)*) => (tuple! { $($other,)* })
+}
+
+macro_rules! tuple {
+    () => ();
+    ( $($name:ident,)+ ) => (
+        impl<D: Decoder, $($name: Decodable<D>),+> Decodable<D> for ($($name,)+) {
+            fn decode(d: &mut D) -> ($($name,)+) {
+                ($({ let element: $name = Decodable::decode(d); element },)+)
+            }
+        }
+        impl<S: Encoder, $($name: Encodable<S>),+> Encodable<S> for ($($name,)+) {
+            #[allow(non_snake_case)]
+            fn encode(&self, s: &mut S) {
+                let ($(ref $name,)+) = *self;
+                $($name.encode(s);)+
+            }
+        }
+        peel! { $($name,)+ }
+    )
+}
+
+tuple! { T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, }
+
+impl<S: Encoder> Encodable<S> for path::Path {
+    fn encode(&self, e: &mut S) {
+        self.to_str().unwrap().encode(e);
+    }
+}
+
+impl<S: Encoder> Encodable<S> for path::PathBuf {
+    fn encode(&self, e: &mut S) {
+        path::Path::encode(self, e);
+    }
+}
+
+impl<D: Decoder> Decodable<D> for path::PathBuf {
+    fn decode(d: &mut D) -> path::PathBuf {
+        let bytes: String = Decodable::decode(d);
+        path::PathBuf::from(bytes)
+    }
+}
+
+impl<S: Encoder, T: Encodable<S> + Copy> Encodable<S> for Cell<T> {
+    fn encode(&self, s: &mut S) {
+        self.get().encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D> + Copy> Decodable<D> for Cell<T> {
+    fn decode(d: &mut D) -> Cell<T> {
+        Cell::new(Decodable::decode(d))
+    }
+}
+
+// FIXME: #15036
+// Should use `try_borrow`, returning an
+// `encoder.error("attempting to Encode borrowed RefCell")`
+// from `encode` when `try_borrow` returns `None`.
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for RefCell<T> {
+    fn encode(&self, s: &mut S) {
+        self.borrow().encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for RefCell<T> {
+    fn decode(d: &mut D) -> RefCell<T> {
+        RefCell::new(Decodable::decode(d))
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for Arc<T> {
+    fn encode(&self, s: &mut S) {
+        (**self).encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Arc<T> {
+    fn decode(d: &mut D) -> Arc<T> {
+        Arc::new(Decodable::decode(d))
+    }
+}
+
+impl<S: Encoder, T: ?Sized + Encodable<S>> Encodable<S> for Box<T> {
+    fn encode(&self, s: &mut S) {
+        (**self).encode(s);
+    }
+}
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Box<T> {
+    fn decode(d: &mut D) -> Box<T> {
+        Box::new(Decodable::decode(d))
+    }
+}