view rust/hg-core/src/dirstate.rs @ 46775:c94fa884240b

rust: Preallocate the returned `Vec` in `utils::files::relativize_path`

Profiling `rhg files > /dev/null` on an old snapshot of mozilla-central
(with `perf` and the Firefox Profiler:
https://github.com/firefox-devtools/profiler/blob/main/docs-user/guide-perf-profiling.md)
showed non-trivial time spend in this function and in `realloc`.

This change makes the wall-clock time for that process on my machine
go from ~190 ms to ~150 ms.

Differential Revision: https://phab.mercurial-scm.org/D10199

// dirstate module
//
// 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.

use crate::errors::HgError;
use crate::revlog::Node;
use crate::{utils::hg_path::HgPathBuf, FastHashMap};
use bytes_cast::{unaligned, BytesCast};
use std::collections::hash_map;
use std::convert::TryFrom;

pub mod dirs_multiset;
pub mod dirstate_map;
#[cfg(feature = "dirstate-tree")]
pub mod dirstate_tree;
pub mod parsers;
pub mod status;

#[derive(Debug, PartialEq, Clone, BytesCast)]
#[repr(C)]
pub struct DirstateParents {
    pub p1: Node,
    pub p2: Node,
}

/// The C implementation uses all signed types. This will be an issue
/// either when 4GB+ source files are commonplace or in 2038, whichever
/// comes first.
#[derive(Debug, PartialEq, Copy, Clone)]
pub struct DirstateEntry {
    pub state: EntryState,
    pub mode: i32,
    pub mtime: i32,
    pub size: i32,
}

#[derive(BytesCast)]
#[repr(C)]
struct RawEntry {
    state: u8,
    mode: unaligned::I32Be,
    size: unaligned::I32Be,
    mtime: unaligned::I32Be,
    length: unaligned::I32Be,
}

/// A `DirstateEntry` with a size of `-2` means that it was merged from the
/// other parent. This allows revert to pick the right status back during a
/// merge.
pub const SIZE_FROM_OTHER_PARENT: i32 = -2;

#[cfg(not(feature = "dirstate-tree"))]
pub type StateMap = FastHashMap<HgPathBuf, DirstateEntry>;
#[cfg(not(feature = "dirstate-tree"))]
pub type StateMapIter<'a> = hash_map::Iter<'a, HgPathBuf, DirstateEntry>;

#[cfg(feature = "dirstate-tree")]
pub type StateMap = dirstate_tree::tree::Tree;
#[cfg(feature = "dirstate-tree")]
pub type StateMapIter<'a> = dirstate_tree::iter::Iter<'a>;
pub type CopyMap = FastHashMap<HgPathBuf, HgPathBuf>;
pub type CopyMapIter<'a> = hash_map::Iter<'a, HgPathBuf, HgPathBuf>;

#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum EntryState {
    Normal,
    Added,
    Removed,
    Merged,
    Unknown,
}

impl TryFrom<u8> for EntryState {
    type Error = HgError;

    fn try_from(value: u8) -> Result<Self, Self::Error> {
        match value {
            b'n' => Ok(EntryState::Normal),
            b'a' => Ok(EntryState::Added),
            b'r' => Ok(EntryState::Removed),
            b'm' => Ok(EntryState::Merged),
            b'?' => Ok(EntryState::Unknown),
            _ => Err(HgError::CorruptedRepository(format!(
                "Incorrect dirstate entry state {}",
                value
            ))),
        }
    }
}

impl Into<u8> for EntryState {
    fn into(self) -> u8 {
        match self {
            EntryState::Normal => b'n',
            EntryState::Added => b'a',
            EntryState::Removed => b'r',
            EntryState::Merged => b'm',
            EntryState::Unknown => b'?',
        }
    }
}