view rust/hg-cpython/src/dagops.rs @ 51225:89ce6a49bfeb

rust-index: implement common_ancestors_heads() and ancestors()

The only differences betwwen `common_ancestors_heads()` and
`find_gca_candidates()` seems to be that:

- the former accepts "overlapping" input revisions (meaning with duplicates).
- limitation to 24 inputs (in the C code), that we translate to using the
  arbitrary size bit sets in the Rust code because we cannot bail to Python.

Given that the input is expected to be small in most cases, we take the
heavy handed approach of going through a HashSet and wait for perfomance
assessment

In case this is used via `hg-cpython`, we can anyway absorb the overhead
by having `commonancestorheads` build a vector of unique values
directly, and introduce a thin wrapper over `find_gca_candidates`, to take
care of bit set type dispatching only.

As far as `ancestors` is concerneed, this is just chaining
`common_ancestors_heads()` with `find_deepest_revs`.

// dagops.rs
//
// Copyright 2019 Georges Racinet <[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::dagops` module provided by the
//! `hg-core` package.
//!
//! From Python, this will be seen as `mercurial.rustext.dagop`
use crate::PyRevision;
use crate::{conversion::rev_pyiter_collect, exceptions::GraphError};
use cpython::{PyDict, PyModule, PyObject, PyResult, Python};
use hg::dagops;
use hg::Revision;
use std::collections::HashSet;
use vcsgraph::ancestors::node_rank;
use vcsgraph::graph::{Parents, Rank};

use crate::revlog::pyindex_to_graph;

/// Using the the `index`, return heads out of any Python iterable of Revisions
///
/// This is the Rust counterpart for `mercurial.dagop.headrevs`
pub fn headrevs(
    py: Python,
    index: PyObject,
    revs: PyObject,
) -> PyResult<HashSet<PyRevision>> {
    let index = pyindex_to_graph(py, index)?;
    let mut as_set: HashSet<Revision> = rev_pyiter_collect(py, &revs, &index)?;
    dagops::retain_heads(&index, &mut as_set)
        .map_err(|e| GraphError::pynew(py, e))?;
    Ok(as_set.into_iter().map(Into::into).collect())
}

/// Computes the rank, i.e. the number of ancestors including itself,
/// of a node represented by its parents.
pub fn rank(
    py: Python,
    index: PyObject,
    p1r: PyRevision,
    p2r: PyRevision,
) -> PyResult<Rank> {
    node_rank(&pyindex_to_graph(py, index)?, &Parents([p1r.0, p2r.0]))
        .map_err(|e| GraphError::pynew_from_vcsgraph(py, e))
}

/// Create the module, with `__package__` given from parent
pub fn init_module(py: Python, package: &str) -> PyResult<PyModule> {
    let dotted_name = &format!("{}.dagop", package);
    let m = PyModule::new(py, dotted_name)?;
    m.add(py, "__package__", package)?;
    m.add(py, "__doc__", "DAG operations - Rust implementation")?;
    m.add(
        py,
        "headrevs",
        py_fn!(py, headrevs(index: PyObject, revs: PyObject)),
    )?;
    m.add(
        py,
        "rank",
        py_fn!(py, rank(index: PyObject, p1r: PyRevision, p2r: PyRevision)),
    )?;

    let sys = PyModule::import(py, "sys")?;
    let sys_modules: PyDict = sys.get(py, "modules")?.extract(py)?;
    sys_modules.set_item(py, dotted_name, &m)?;
    // Example C code (see pyexpat.c and import.c) will "give away the
    // reference", but we won't because it will be consumed once the
    // Rust PyObject is dropped.
    Ok(m)
}