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rust-cpython: add macro for sharing references...
rust-cpython: add macro for sharing references Following an experiment done by Georges Racinet, we now have a working way of sharing references between Python and Rust. This is needed in many points of the codebase, for example every time we need to expose an iterator to a Rust-backed Python class. In a few words, references are (unsafely) marked as `'static` and coupled with manual reference counting; we are doing manual borrow-checking. This changes introduces two declarative macro to help reduce boilerplate. While it is better than not using macros, they are not perfect. They need to: - Integrate with the garbage collector for container types (not needed as of yet), as stated in the docstring - Allow for leaking multiple attributes at the same time - Inject the `py_shared_state` data attribute in `py_class`-generated structs - Automatically namespace the functions and attributes they generate For at least the last two points, we will need to write a procedural macro instead of a declarative one. While this reference-sharing mechanism is being ironed out I thought it best not to implement it yet. Lastly, and implementation detail renders our Rust-backed Python iterators too strict to be proper drop-in replacements, as will be illustrated in a future patch: if the data structure referenced by a non-depleted iterator is mutated, an `AlreadyBorrowed` exception is raised, whereas Python would allow it, only to raise a `RuntimeError` if `next` is called on said iterator. This will have to be addressed at some point. Differential Revision: https://phab.mercurial-scm.org/D6631

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dirstate.rs
79 lines | 2.0 KiB | application/rls-services+xml | RustLexer
// dirstate module
//
// Copyright 2019 Raphaël Gomès <rgomes@octobus.net>
//
// This software may be used and distributed according to the terms of the
// GNU General Public License version 2 or any later version.
use crate::DirstateParseError;
use std::collections::HashMap;
use std::convert::TryFrom;
pub mod dirs_multiset;
pub mod parsers;
#[derive(Debug, PartialEq, Clone)]
pub struct DirstateParents {
pub p1: [u8; 20],
pub p2: [u8; 20],
}
/// The C implementation uses all signed types. This will be an issue
/// either when 4GB+ source files are commonplace or in 2038, whichever
/// comes first.
#[derive(Debug, PartialEq, Copy, Clone)]
pub struct DirstateEntry {
pub state: EntryState,
pub mode: i32,
pub mtime: i32,
pub size: i32,
}
pub type StateMap = HashMap<Vec<u8>, DirstateEntry>;
pub type CopyMap = HashMap<Vec<u8>, Vec<u8>>;
/// The Python implementation passes either a mapping (dirstate) or a flat
/// iterable (manifest)
pub enum DirsIterable<'a> {
Dirstate(&'a HashMap<Vec<u8>, DirstateEntry>),
Manifest(&'a Vec<Vec<u8>>),
}
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum EntryState {
Normal,
Added,
Removed,
Merged,
Unknown,
}
impl TryFrom<u8> for EntryState {
type Error = DirstateParseError;
fn try_from(value: u8) -> Result<Self, Self::Error> {
match value {
b'n' => Ok(EntryState::Normal),
b'a' => Ok(EntryState::Added),
b'r' => Ok(EntryState::Removed),
b'm' => Ok(EntryState::Merged),
b'?' => Ok(EntryState::Unknown),
_ => Err(DirstateParseError::CorruptedEntry(format!(
"Incorrect entry state {}",
value
))),
}
}
}
impl Into<u8> for EntryState {
fn into(self) -> u8 {
match self {
EntryState::Normal => b'n',
EntryState::Added => b'a',
EntryState::Removed => b'r',
EntryState::Merged => b'm',
EntryState::Unknown => b'?',
}
}
}