rust-cpython: implement Graph using C parents function
We introduce the `Index` struct that wraps the C index. It is
not intrinsically protected by the GIL (see the lengthy
discussion in its docstring). Improving on this seems
prematurate at this point.
A pointer to the parents function is stored on the parsers
C extension module as a capsule object.
This is the recommended way to export a C API for consumption
from other extensions.
See also: https://docs.python.org/2.7/c-api/capsule.html
In our case, we use it in cindex.rs, retrieving function
pointer from the capsule and storing it within the CIndex
struct, alongside with a pointer to the index. From there,
the implementation is very close to the one from hg-direct-ffi.
The naming convention for the capsule is inspired from the
one in datetime:
>>> import datetime
>>> datetime.datetime_CAPI
<capsule object "datetime.datetime_CAPI" at 0x7fb51201ecf0>
although in datetime's case, the capsule points to a struct holding
several type objects and methods.
Differential Revision: https://phab.mercurial-scm.org/D5438
// 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:
//! ```
//! >>> from mercurial.rustext import ancestor
//! >>> ancestor.__doc__
//! 'Generic DAG ancestor algorithms - Rust implementation'
//! ```
#[macro_use]
extern crate cpython;
extern crate hg;
extern crate libc;
mod ancestors;
mod cindex;
mod exceptions;
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, "__package__", "mercurial")?;
m.add(py, "ancestor", ancestors::init_module(py, &dotted_name)?)?;
m.add(py, "GraphError", py.get_type::<exceptions::GraphError>())?;
Ok(())
});