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view rust/hg-cpython/src/lib.rs @ 42768:30320c7bf79f
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
author | Rapha?l Gom?s <rgomes@octobus.net> |
---|---|
date | Tue, 09 Jul 2019 15:15:54 +0200 |
parents | 760a7851e9ba |
children | 6a551a2dc666 |
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// lib.rs // // Copyright 2018 Georges Racinet <gracinet@anybox.fr> // // This software may be used and distributed according to the terms of the // GNU General Public License version 2 or any later version. //! Python bindings of `hg-core` objects using the `cpython` crate. //! Once compiled, the resulting single shared library object can be placed in //! the `mercurial` package directly as `rustext.so` or `rustext.dll`. //! It holds several modules, so that from the point of view of Python, //! it behaves as the `cext` package. //! //! Example: //! //! ```text //! >>> from mercurial.rustext import ancestor //! >>> ancestor.__doc__ //! 'Generic DAG ancestor algorithms - Rust implementation' //! ``` /// This crate uses nested private macros, `extern crate` is still needed in /// 2018 edition. #[macro_use] extern crate cpython; pub mod ancestors; mod cindex; mod conversion; #[macro_use] pub mod ref_sharing; pub mod dagops; pub mod dirstate; pub mod parsers; pub mod discovery; pub mod exceptions; pub mod filepatterns; py_module_initializer!(rustext, initrustext, PyInit_rustext, |py, m| { m.add( py, "__doc__", "Mercurial core concepts - Rust implementation", )?; let dotted_name: String = m.get(py, "__name__")?.extract(py)?; m.add(py, "ancestor", ancestors::init_module(py, &dotted_name)?)?; m.add(py, "dagop", dagops::init_module(py, &dotted_name)?)?; m.add(py, "discovery", discovery::init_module(py, &dotted_name)?)?; m.add(py, "dirstate", dirstate::init_module(py, &dotted_name)?)?; m.add( py, "filepatterns", filepatterns::init_module(py, &dotted_name)?, )?; m.add( py, "parsers", parsers::init_parsers_module(py, &dotted_name)?, )?; m.add(py, "GraphError", py.get_type::<exceptions::GraphError>())?; m.add( py, "PatternFileError", py.get_type::<exceptions::PatternFileError>(), )?; m.add( py, "PatternError", py.get_type::<exceptions::PatternError>(), )?; Ok(()) });