view rust/hg-cpython/src/dirstate.rs @ 47123:d8ac62374943

dirstate-tree: Make `DirstateMap` borrow from a bytes buffer

… that has the contents of the `.hg/dirstate` file.
This only applies to the tree-based flavor of `DirstateMap`.

For now only the entire `&[u8]` slice is stored, so this is not useful yet.

Adding a lifetime parameter to the `DirstateMap` struct (in hg-core) makes
Python bindings non-trivial because we keep that struct in a Python object
that has a dynamic lifetime tied to Python’s reference-counting and GC.
As long as we keep the `PyBytes` that owns the borrowed bytes buffer next to
the borrowing struct, the buffer will live long enough for the borrows to stay
valid. However this relationship cannot be expressed in safe Rust code in a
way that would statisfy they borrow-checker. We use `unsafe` code to erase
that lifetime parameter, and encapsulate it in a safe abstraction similar to
the owning-ref crate: https://docs.rs/owning_ref/

Differential Revision: https://phab.mercurial-scm.org/D10557

// 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 copymap;
mod dirs_multiset;
mod dirstate_map;
mod dispatch;
mod non_normal_entries;
mod owning;
mod status;
use crate::{
    dirstate::{
        dirs_multiset::Dirs, dirstate_map::DirstateMap, status::status_wrapper,
    },
    exceptions,
};
use cpython::{
    exc, PyBytes, PyDict, PyErr, PyList, PyModule, PyObject, PyResult,
    PySequence, Python,
};
use hg::{utils::hg_path::HgPathBuf, DirstateEntry, EntryState, StateMap};
use libc::{c_char, c_int};
use std::convert::TryFrom;

// 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.
py_capsule_fn!(
    from mercurial.cext.parsers import make_dirstate_tuple_CAPI
        as make_dirstate_tuple_capi
        signature (
            state: c_char,
            mode: c_int,
            size: c_int,
            mtime: c_int,
        ) -> *mut RawPyObject
);

pub fn make_dirstate_tuple(
    py: Python,
    entry: &DirstateEntry,
) -> PyResult<PyObject> {
    // might be silly to retrieve capsule function in hot loop
    let make = make_dirstate_tuple_capi::retrieve(py)?;

    let &DirstateEntry {
        state,
        mode,
        size,
        mtime,
    } = entry;
    // Explicitly go through u8 first, then cast to platform-specific `c_char`
    // because Into<u8> has a specific implementation while `as c_char` would
    // just do a naive enum cast.
    let state_code: u8 = state.into();

    let maybe_obj = unsafe {
        let ptr = make(state_code as c_char, mode, size, mtime);
        PyObject::from_owned_ptr_opt(py, ptr)
    };
    maybe_obj.ok_or_else(|| PyErr::fetch(py))
}

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 =
                EntryState::try_from(state.data(py)[0]).map_err(|e| {
                    PyErr::new::<exc::ValueError, _>(py, e.to_string())
                })?;
            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((
                HgPathBuf::from(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)?;

    env_logger::init();

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

    m.add(
        py,
        "FallbackError",
        py.get_type::<exceptions::FallbackError>(),
    )?;
    m.add_class::<Dirs>(py)?;
    m.add_class::<DirstateMap>(py)?;
    m.add(
        py,
        "status",
        py_fn!(
            py,
            status_wrapper(
                dmap: DirstateMap,
                root_dir: PyObject,
                matcher: PyObject,
                ignorefiles: PyList,
                check_exec: bool,
                last_normal_time: i64,
                list_clean: bool,
                list_ignored: bool,
                list_unknown: bool,
                collect_traversed_dirs: bool
            )
        ),
    )?;

    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)
}