1acbe7573d
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`.
70 lines
1.6 KiB
Rust
70 lines
1.6 KiB
Rust
//! Calculation and management of a Strict Version Hash for crates
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//!
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//! The SVH is used for incremental compilation to track when HIR
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//! nodes have changed between compilations, and also to detect
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//! mismatches where we have two versions of the same crate that were
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//! compiled from distinct sources.
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use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
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use std::fmt;
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use std::hash::{Hash, Hasher};
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use crate::stable_hasher;
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#[derive(Copy, Clone, PartialEq, Eq, Debug)]
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pub struct Svh {
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hash: u64,
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}
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impl Svh {
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/// Creates a new `Svh` given the hash. If you actually want to
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/// compute the SVH from some HIR, you want the `calculate_svh`
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/// function found in `rustc_incremental`.
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pub fn new(hash: u64) -> Svh {
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Svh { hash }
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}
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pub fn as_u64(&self) -> u64 {
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self.hash
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}
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pub fn to_string(&self) -> String {
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format!("{:016x}", self.hash)
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}
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}
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impl Hash for Svh {
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fn hash<H>(&self, state: &mut H)
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where
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H: Hasher,
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{
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self.hash.to_le().hash(state);
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}
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}
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impl fmt::Display for Svh {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.pad(&self.to_string())
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}
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}
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impl<S: Encoder> Encodable<S> for Svh {
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fn encode(&self, s: &mut S) {
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s.emit_u64(self.as_u64().to_le());
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}
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}
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impl<D: Decoder> Decodable<D> for Svh {
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fn decode(d: &mut D) -> Svh {
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Svh::new(u64::from_le(d.read_u64()))
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}
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}
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impl<T> stable_hasher::HashStable<T> for Svh {
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#[inline]
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fn hash_stable(&self, ctx: &mut T, hasher: &mut stable_hasher::StableHasher) {
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let Svh { hash } = *self;
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hash.hash_stable(ctx, hasher);
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}
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}
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