rust/hg-core/src/lib.rs

rust: itering less on MissingAncestors.bases for max()

Instead of iterating on the whole `self.bases` each time to find
its max, we keep the latter in a separate member attribute and
keep it up to date in `add_bases()`

On a perfdiscovery done on PyPy, with repos prepared with
`contrib/discovery-helper.sh 50 100`, this gives a slight
improvement (around 0.5% on wall time, but 10% on CPU)

before:
! wall 0.172801 comb 0.180000 user 0.180000 sys 0.000000 (median of 541)
after:
! wall 0.171798 comb 0.160000 user 0.160000 sys 0.000000 (median of 551)

(perf command run time upped because of bigger variability during this test).

Differential Revision: https://phab.mercurial-scm.org/D5945

// Copyright 2018 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.
mod ancestors;
pub mod dagops;
pub use ancestors::{AncestorsIterator, LazyAncestors, MissingAncestors};
pub mod testing;  // unconditionally built, for use from integration tests

/// Mercurial revision numbers
///
/// As noted in revlog.c, revision numbers are actually encoded in
/// 4 bytes, and are liberally converted to ints, whence the i32
pub type Revision = i32;


/// Marker expressing the absence of a parent
///
/// Independently of the actual representation, `NULL_REVISION` is guaranteed
/// to be smaller that all existing revisions.
pub const NULL_REVISION: Revision = -1;

/// Same as `mercurial.node.wdirrev`
///
/// This is also equal to `i32::max_value()`, but it's better to spell
/// it out explicitely, same as in `mercurial.node`
pub const WORKING_DIRECTORY_REVISION: Revision = 0x7fffffff;

/// The simplest expression of what we need of Mercurial DAGs.
pub trait Graph {
    /// Return the two parents of the given `Revision`.
    ///
    /// Each of the parents can be independently `NULL_REVISION`
    fn parents(&self, Revision) -> Result<[Revision; 2], GraphError>;
}

#[derive(Clone, Debug, PartialEq)]
pub enum GraphError {
    ParentOutOfRange(Revision),
    WorkingDirectoryUnsupported,
}