rust/hg-cpython/src/dirstate.rs

rust-parsers: switch to parse/pack_dirstate to mutate-on-loop

Both `parse_dirstate` and `pack_dirstate` can operate directly on the data
they're passed, which prevents the creation of intermediate data structures,
simplifies the function signatures and reduces boilerplate. They are exposed
directly to the Python for now, but a later patch will make use of them inside
`hg-core`.

Differential Revision: https://phab.mercurial-scm.org/D6628

// dirstate.rs
//
// Copyright 2019 Raphaël Gomès <[e-mail]>
//
// This software may be used and distributed according to the terms of the
// GNU General Public License version 2 or any later version.

//! Bindings for the `hg::dirstate` module provided by the
//! `hg-core` package.
//!
//! From Python, this will be seen as `mercurial.rustext.dirstate`
mod dirs_multiset;
use crate::dirstate::dirs_multiset::Dirs;
use cpython::{
    PyBytes, PyDict, PyErr, PyModule, PyObject, PyResult, PySequence, Python,
};
use hg::{DirstateEntry, StateMap};
use libc::{c_char, c_int};
#[cfg(feature = "python27")]
use python27_sys::PyCapsule_Import;
#[cfg(feature = "python3")]
use python3_sys::PyCapsule_Import;
use std::ffi::CStr;
use std::mem::transmute;

/// C code uses a custom `dirstate_tuple` type, checks in multiple instances
/// for this type, and raises a Python `Exception` if the check does not pass.
/// Because this type differs only in name from the regular Python tuple, it
/// would be a good idea in the near future to remove it entirely to allow
/// for a pure Python tuple of the same effective structure to be used,
/// rendering this type and the capsule below useless.
type MakeDirstateTupleFn = extern "C" fn(
    state: c_char,
    mode: c_int,
    size: c_int,
    mtime: c_int,
) -> PyObject;

/// This is largely a copy/paste from cindex.rs, pending the merge of a
/// `py_capsule_fn!` macro in the rust-cpython project:
/// https://github.com/dgrunwald/rust-cpython/pull/169
pub fn decapsule_make_dirstate_tuple(
    py: Python,
) -> PyResult<MakeDirstateTupleFn> {
    unsafe {
        let caps_name = CStr::from_bytes_with_nul_unchecked(
            b"mercurial.cext.parsers.make_dirstate_tuple_CAPI\0",
        );
        let from_caps = PyCapsule_Import(caps_name.as_ptr(), 0);
        if from_caps.is_null() {
            return Err(PyErr::fetch(py));
        }
        Ok(transmute(from_caps))
    }
}

pub fn extract_dirstate(py: Python, dmap: &PyDict) -> Result<StateMap, PyErr> {
    dmap.items(py)
        .iter()
        .map(|(filename, stats)| {
            let stats = stats.extract::<PySequence>(py)?;
            let state = stats.get_item(py, 0)?.extract::<PyBytes>(py)?;
            let state = state.data(py)[0] as i8;
            let mode = stats.get_item(py, 1)?.extract(py)?;
            let size = stats.get_item(py, 2)?.extract(py)?;
            let mtime = stats.get_item(py, 3)?.extract(py)?;
            let filename = filename.extract::<PyBytes>(py)?;
            let filename = filename.data(py);
            Ok((
                filename.to_owned(),
                DirstateEntry {
                    state,
                    mode,
                    size,
                    mtime,
                },
            ))
        })
        .collect()
}

/// Create the module, with `__package__` given from parent
pub fn init_module(py: Python, package: &str) -> PyResult<PyModule> {
    let dotted_name = &format!("{}.dirstate", package);
    let m = PyModule::new(py, dotted_name)?;

    m.add(py, "__package__", package)?;
    m.add(py, "__doc__", "Dirstate - Rust implementation")?;

    m.add_class::<Dirs>(py)?;

    let sys = PyModule::import(py, "sys")?;
    let sys_modules: PyDict = sys.get(py, "modules")?.extract(py)?;
    sys_modules.set_item(py, dotted_name, &m)?;

    Ok(m)
}