rust/compiler/rustc_serialize/src/collection_impls.rs
Nicholas Nethercote 1acbe7573d Use delayed error handling for Encodable and Encoder infallible.
There are two impls of the `Encoder` trait: `opaque::Encoder` and
`opaque::FileEncoder`. The former encodes into memory and is infallible, the
latter writes to file and is fallible.

Currently, standard `Result`/`?`/`unwrap` error handling is used, but this is a
bit verbose and has non-trivial cost, which is annoying given how rare failures
are (especially in the infallible `opaque::Encoder` case).

This commit changes how `Encoder` fallibility is handled. All the `emit_*`
methods are now infallible. `opaque::Encoder` requires no great changes for
this. `opaque::FileEncoder` now implements a delayed error handling strategy.
If a failure occurs, it records this via the `res` field, and all subsequent
encoding operations are skipped if `res` indicates an error has occurred. Once
encoding is complete, the new `finish` method is called, which returns a
`Result`. In other words, there is now a single `Result`-producing method
instead of many of them.

This has very little effect on how any file errors are reported if
`opaque::FileEncoder` has any failures.

Much of this commit is boring mechanical changes, removing `Result` return
values and `?` or `unwrap` from expressions. The more interesting parts are as
follows.
- serialize.rs: The `Encoder` trait gains an `Ok` associated type. The
  `into_inner` method is changed into `finish`, which returns
  `Result<Vec<u8>, !>`.
- opaque.rs: The `FileEncoder` adopts the delayed error handling
  strategy. Its `Ok` type is a `usize`, returning the number of bytes
  written, replacing previous uses of `FileEncoder::position`.
- Various methods that take an encoder now consume it, rather than being
  passed a mutable reference, e.g. `serialize_query_result_cache`.
2022-06-08 07:01:26 +10:00

268 lines
6.5 KiB
Rust

//! Implementations of serialization for structures found in liballoc
use std::hash::{BuildHasher, Hash};
use crate::{Decodable, Decoder, Encodable, Encoder};
use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet, LinkedList, VecDeque};
use std::rc::Rc;
use std::sync::Arc;
use smallvec::{Array, SmallVec};
impl<S: Encoder, A: Array<Item: Encodable<S>>> Encodable<S> for SmallVec<A> {
fn encode(&self, s: &mut S) {
let slice: &[A::Item] = self;
slice.encode(s);
}
}
impl<D: Decoder, A: Array<Item: Decodable<D>>> Decodable<D> for SmallVec<A> {
fn decode(d: &mut D) -> SmallVec<A> {
let len = d.read_usize();
(0..len).map(|_| Decodable::decode(d)).collect()
}
}
impl<S: Encoder, T: Encodable<S>> Encodable<S> for LinkedList<T> {
fn encode(&self, s: &mut S) {
s.emit_usize(self.len());
for e in self.iter() {
e.encode(s);
}
}
}
impl<D: Decoder, T: Decodable<D>> Decodable<D> for LinkedList<T> {
fn decode(d: &mut D) -> LinkedList<T> {
let len = d.read_usize();
(0..len).map(|_| Decodable::decode(d)).collect()
}
}
impl<S: Encoder, T: Encodable<S>> Encodable<S> for VecDeque<T> {
fn encode(&self, s: &mut S) {
s.emit_usize(self.len());
for e in self.iter() {
e.encode(s);
}
}
}
impl<D: Decoder, T: Decodable<D>> Decodable<D> for VecDeque<T> {
fn decode(d: &mut D) -> VecDeque<T> {
let len = d.read_usize();
(0..len).map(|_| Decodable::decode(d)).collect()
}
}
impl<S: Encoder, K, V> Encodable<S> for BTreeMap<K, V>
where
K: Encodable<S> + PartialEq + Ord,
V: Encodable<S>,
{
fn encode(&self, e: &mut S) {
e.emit_usize(self.len());
for (key, val) in self.iter() {
key.encode(e);
val.encode(e);
}
}
}
impl<D: Decoder, K, V> Decodable<D> for BTreeMap<K, V>
where
K: Decodable<D> + PartialEq + Ord,
V: Decodable<D>,
{
fn decode(d: &mut D) -> BTreeMap<K, V> {
let len = d.read_usize();
let mut map = BTreeMap::new();
for _ in 0..len {
let key = Decodable::decode(d);
let val = Decodable::decode(d);
map.insert(key, val);
}
map
}
}
impl<S: Encoder, T> Encodable<S> for BTreeSet<T>
where
T: Encodable<S> + PartialEq + Ord,
{
fn encode(&self, s: &mut S) {
s.emit_usize(self.len());
for e in self.iter() {
e.encode(s);
}
}
}
impl<D: Decoder, T> Decodable<D> for BTreeSet<T>
where
T: Decodable<D> + PartialEq + Ord,
{
fn decode(d: &mut D) -> BTreeSet<T> {
let len = d.read_usize();
let mut set = BTreeSet::new();
for _ in 0..len {
set.insert(Decodable::decode(d));
}
set
}
}
impl<E: Encoder, K, V, S> Encodable<E> for HashMap<K, V, S>
where
K: Encodable<E> + Eq,
V: Encodable<E>,
S: BuildHasher,
{
fn encode(&self, e: &mut E) {
e.emit_usize(self.len());
for (key, val) in self.iter() {
key.encode(e);
val.encode(e);
}
}
}
impl<D: Decoder, K, V, S> Decodable<D> for HashMap<K, V, S>
where
K: Decodable<D> + Hash + Eq,
V: Decodable<D>,
S: BuildHasher + Default,
{
fn decode(d: &mut D) -> HashMap<K, V, S> {
let len = d.read_usize();
let state = Default::default();
let mut map = HashMap::with_capacity_and_hasher(len, state);
for _ in 0..len {
let key = Decodable::decode(d);
let val = Decodable::decode(d);
map.insert(key, val);
}
map
}
}
impl<E: Encoder, T, S> Encodable<E> for HashSet<T, S>
where
T: Encodable<E> + Eq,
S: BuildHasher,
{
fn encode(&self, s: &mut E) {
s.emit_usize(self.len());
for e in self.iter() {
e.encode(s);
}
}
}
impl<D: Decoder, T, S> Decodable<D> for HashSet<T, S>
where
T: Decodable<D> + Hash + Eq,
S: BuildHasher + Default,
{
fn decode(d: &mut D) -> HashSet<T, S> {
let len = d.read_usize();
let state = Default::default();
let mut set = HashSet::with_capacity_and_hasher(len, state);
for _ in 0..len {
set.insert(Decodable::decode(d));
}
set
}
}
impl<E: Encoder, K, V, S> Encodable<E> for indexmap::IndexMap<K, V, S>
where
K: Encodable<E> + Hash + Eq,
V: Encodable<E>,
S: BuildHasher,
{
fn encode(&self, e: &mut E) {
e.emit_usize(self.len());
for (key, val) in self.iter() {
key.encode(e);
val.encode(e);
}
}
}
impl<D: Decoder, K, V, S> Decodable<D> for indexmap::IndexMap<K, V, S>
where
K: Decodable<D> + Hash + Eq,
V: Decodable<D>,
S: BuildHasher + Default,
{
fn decode(d: &mut D) -> indexmap::IndexMap<K, V, S> {
let len = d.read_usize();
let state = Default::default();
let mut map = indexmap::IndexMap::with_capacity_and_hasher(len, state);
for _ in 0..len {
let key = Decodable::decode(d);
let val = Decodable::decode(d);
map.insert(key, val);
}
map
}
}
impl<E: Encoder, T, S> Encodable<E> for indexmap::IndexSet<T, S>
where
T: Encodable<E> + Hash + Eq,
S: BuildHasher,
{
fn encode(&self, s: &mut E) {
s.emit_usize(self.len());
for e in self.iter() {
e.encode(s);
}
}
}
impl<D: Decoder, T, S> Decodable<D> for indexmap::IndexSet<T, S>
where
T: Decodable<D> + Hash + Eq,
S: BuildHasher + Default,
{
fn decode(d: &mut D) -> indexmap::IndexSet<T, S> {
let len = d.read_usize();
let state = Default::default();
let mut set = indexmap::IndexSet::with_capacity_and_hasher(len, state);
for _ in 0..len {
set.insert(Decodable::decode(d));
}
set
}
}
impl<E: Encoder, T: Encodable<E>> Encodable<E> for Rc<[T]> {
fn encode(&self, s: &mut E) {
let slice: &[T] = self;
slice.encode(s);
}
}
impl<D: Decoder, T: Decodable<D>> Decodable<D> for Rc<[T]> {
fn decode(d: &mut D) -> Rc<[T]> {
let vec: Vec<T> = Decodable::decode(d);
vec.into()
}
}
impl<E: Encoder, T: Encodable<E>> Encodable<E> for Arc<[T]> {
fn encode(&self, s: &mut E) {
let slice: &[T] = self;
slice.encode(s);
}
}
impl<D: Decoder, T: Decodable<D>> Decodable<D> for Arc<[T]> {
fn decode(d: &mut D) -> Arc<[T]> {
let vec: Vec<T> = Decodable::decode(d);
vec.into()
}
}