annotate rust/hg-core/src/lib.rs @ 43826:5ac243a92e37

rust-performance: introduce FastHashMap type alias for HashMap

Rust's default hashing is slow, because it is meant for preventing collision
attacks.
For all of the current Rust code, we don't care about those attacks, because
if an person with bad intentions has write access to your repo, you have other
issues.

I've chosen to use the TwoXHash crate because it was made by a reputable member
of the Rust community and has very good benchmarks.

For now it does not seem to improve performance by much for the current code,
but it's something else to not worry about when benchmarking code: in a
previous experiment with copytracing in Rust, it accounted for more than 10%
of the time of the entire script.

Differential Revision: https://phab.mercurial-scm.org/D7116

// 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};
mod dirstate;
pub mod discovery;
pub mod testing; // unconditionally built, for use from integration tests
pub use dirstate::{
    dirs_multiset::{DirsMultiset, DirsMultisetIter},
    dirstate_map::DirstateMap,
    parsers::{pack_dirstate, parse_dirstate, PARENT_SIZE},
    status::status,
    CopyMap, CopyMapIter, DirstateEntry, DirstateParents, EntryState,
    StateMap, StateMapIter,
};
mod filepatterns;
pub mod matchers;
pub mod utils;

use crate::utils::hg_path::HgPathBuf;
pub use filepatterns::{
    build_single_regex, read_pattern_file, PatternSyntax, PatternTuple,
};
use std::collections::HashMap;
use twox_hash::RandomXxHashBuilder64;

/// 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, rev: Revision) -> Result<[Revision; 2], GraphError>;
}

pub type LineNumber = usize;

/// Rust's default hasher is too slow because it tries to prevent collision
/// attacks. We are not concerned about those: if an ill-minded person has
/// write access to your repository, you have other issues.
pub type FastHashMap<K, V> = HashMap<K, V, RandomXxHashBuilder64>;

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

#[derive(Clone, Debug, PartialEq)]
pub enum DirstateParseError {
    TooLittleData,
    Overflow,
    CorruptedEntry(String),
    Damaged,
}

impl From<std::io::Error> for DirstateParseError {
    fn from(e: std::io::Error) -> Self {
        DirstateParseError::CorruptedEntry(e.to_string())
    }
}

impl ToString for DirstateParseError {
    fn to_string(&self) -> String {
        use crate::DirstateParseError::*;
        match self {
            TooLittleData => "Too little data for dirstate.".to_string(),
            Overflow => "Overflow in dirstate.".to_string(),
            CorruptedEntry(e) => format!("Corrupted entry: {:?}.", e),
            Damaged => "Dirstate appears to be damaged.".to_string(),
        }
    }
}

#[derive(Debug, PartialEq)]
pub enum DirstatePackError {
    CorruptedEntry(String),
    CorruptedParent,
    BadSize(usize, usize),
}

impl From<std::io::Error> for DirstatePackError {
    fn from(e: std::io::Error) -> Self {
        DirstatePackError::CorruptedEntry(e.to_string())
    }
}
#[derive(Debug, PartialEq)]
pub enum DirstateMapError {
    PathNotFound(HgPathBuf),
    EmptyPath,
    ConsecutiveSlashes,
}

impl ToString for DirstateMapError {
    fn to_string(&self) -> String {
        use crate::DirstateMapError::*;
        match self {
            PathNotFound(_) => "expected a value, found none".to_string(),
            EmptyPath => "Overflow in dirstate.".to_string(),
            ConsecutiveSlashes => {
                "found invalid consecutive slashes in path".to_string()
            }
        }
    }
}

pub enum DirstateError {
    Parse(DirstateParseError),
    Pack(DirstatePackError),
    Map(DirstateMapError),
    IO(std::io::Error),
}

impl From<DirstateParseError> for DirstateError {
    fn from(e: DirstateParseError) -> Self {
        DirstateError::Parse(e)
    }
}

impl From<DirstatePackError> for DirstateError {
    fn from(e: DirstatePackError) -> Self {
        DirstateError::Pack(e)
    }
}

#[derive(Debug)]
pub enum PatternError {
    UnsupportedSyntax(String),
}

#[derive(Debug)]
pub enum PatternFileError {
    IO(std::io::Error),
    Pattern(PatternError, LineNumber),
}

impl From<std::io::Error> for PatternFileError {
    fn from(e: std::io::Error) -> Self {
        PatternFileError::IO(e)
    }
}

impl From<DirstateMapError> for DirstateError {
    fn from(e: DirstateMapError) -> Self {
        DirstateError::Map(e)
    }
}

impl From<std::io::Error> for DirstateError {
    fn from(e: std::io::Error) -> Self {
        DirstateError::IO(e)
    }
}