rust/hg-core/src/utils/files.rs

rust-dirstate-status: add first Rust implementation of `dirstate.status`

Note: This patch also added the rayon crate as a Cargo dependency. It will
help us immensely in making Rust code parallel and easy to maintain. It is
a stable, well-known, and supported crate maintained by people on the Rust
team.

The current `dirstate.status` method has grown over the years through bug
reports and new features to the point where it got too big and too complex.

This series does not yet improve the logic, but adds a Rust fast-path to speed
up certain cases.

Tested on mozilla-try-2019-02-18 with zstd compression:
    - `hg diff` on an empty working copy:
        - c: 1.64(+-)0.04s
        - rust+c before this change: 2.84(+-)0.1s
        - rust+c: 849(+-)40ms
    - `hg commit` when creating a file:
        - c: 5.960s
        - rust+c before this change: 5.828s
        - rust+c: 4.668s
    - `hg commit` when updating a file:
        - c: 4.866s
        - rust+c before this change: 4.371s
        - rust+c: 3.855s
    - `hg status -mard`
        - c: 1.82(+-)0.04s
        - rust+c before this change: 2.64(+-)0.1s
        - rust+c: 896(+-)30ms

The numbers are clear: the current Rust `dirstatemap` implementation is super
slow, its performance needs to be addressed.
This will be done in a future series, immediately after this one, with the goal
of getting Rust to be at least to the speed of the Python + C implementation
in all cases before the 5.2 freeze. At worse, we gate dirstatemap to only be used
in those cases.

Cases where the fast-path is not executed:
    - for commands that need ignore support (`status`, for example)
    - if subrepos are found (should not be hard to add, but winter is coming)
    - any other matcher than an `alwaysmatcher`, like patterns, etc.
    - with extensions like `sparse` and `fsmonitor`

The next step after this is to rethink the logic to be closer to
Jane Street's Valentin Gatien-Baron's Rust fast-path which does a lot less
work when possible.

Differential Revision: https://phab.mercurial-scm.org/D7058

// files.rs
//
// Copyright 2019
// Raphaël Gomès <[e-mail]>,
// Yuya Nishihara <[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.

//! Functions for fiddling with files.

use crate::utils::hg_path::{HgPath, HgPathBuf};
use std::iter::FusedIterator;

use std::fs::Metadata;
use std::path::Path;

pub fn get_path_from_bytes(bytes: &[u8]) -> &Path {
    let os_str;
    #[cfg(unix)]
    {
        use std::os::unix::ffi::OsStrExt;
        os_str = std::ffi::OsStr::from_bytes(bytes);
    }
    // TODO Handle other platforms
    // TODO: convert from WTF8 to Windows MBCS (ANSI encoding).
    // Perhaps, the return type would have to be Result<PathBuf>.

    Path::new(os_str)
}

/// An iterator over repository path yielding itself and its ancestors.
#[derive(Copy, Clone, Debug)]
pub struct Ancestors<'a> {
    next: Option<&'a HgPath>,
}

impl<'a> Iterator for Ancestors<'a> {
    type Item = &'a HgPath;

    fn next(&mut self) -> Option<Self::Item> {
        let next = self.next;
        self.next = match self.next {
            Some(s) if s.is_empty() => None,
            Some(s) => {
                let p = s.bytes().rposition(|c| *c == b'/').unwrap_or(0);
                Some(HgPath::new(&s.as_bytes()[..p]))
            }
            None => None,
        };
        next
    }
}

impl<'a> FusedIterator for Ancestors<'a> {}

/// Returns an iterator yielding ancestor directories of the given repository
/// path.
///
/// The path is separated by '/', and must not start with '/'.
///
/// The path itself isn't included unless it is b"" (meaning the root
/// directory.)
pub fn find_dirs<'a>(path: &'a HgPath) -> Ancestors<'a> {
    let mut dirs = Ancestors { next: Some(path) };
    if !path.is_empty() {
        dirs.next(); // skip itself
    }
    dirs
}

/// TODO more than ASCII?
pub fn normalize_case(path: &HgPath) -> HgPathBuf {
    #[cfg(windows)] // NTFS compares via upper()
    return path.to_ascii_uppercase();
    #[cfg(unix)]
    path.to_ascii_lowercase()
}

#[derive(Eq, PartialEq, Ord, PartialOrd, Copy, Clone)]
pub struct HgMetadata {
    pub st_dev: u64,
    pub st_mode: u32,
    pub st_nlink: u64,
    pub st_size: u64,
    pub st_mtime: i64,
    pub st_ctime: i64,
}

// TODO support other plaforms
#[cfg(unix)]
impl HgMetadata {
    pub fn from_metadata(metadata: Metadata) -> Self {
        use std::os::unix::fs::MetadataExt;
        Self {
            st_dev: metadata.dev(),
            st_mode: metadata.mode(),
            st_nlink: metadata.nlink(),
            st_size: metadata.size(),
            st_mtime: metadata.mtime(),
            st_ctime: metadata.ctime(),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn find_dirs_some() {
        let mut dirs = super::find_dirs(HgPath::new(b"foo/bar/baz"));
        assert_eq!(dirs.next(), Some(HgPath::new(b"foo/bar")));
        assert_eq!(dirs.next(), Some(HgPath::new(b"foo")));
        assert_eq!(dirs.next(), Some(HgPath::new(b"")));
        assert_eq!(dirs.next(), None);
        assert_eq!(dirs.next(), None);
    }

    #[test]
    fn find_dirs_empty() {
        // looks weird, but mercurial.util.finddirs(b"") yields b""
        let mut dirs = super::find_dirs(HgPath::new(b""));
        assert_eq!(dirs.next(), Some(HgPath::new(b"")));
        assert_eq!(dirs.next(), None);
        assert_eq!(dirs.next(), None);
    }
}