view rust/hg-core/examples/nodemap/index.rs @ 46371:0903d6b9b1df

repository: introduce register_changeset callback

The new callback is called whenever a changeset is added to the repository
(commit, unbundle or exchange). Since the bulk operations already parse
the changeset (readfiles or full changesetrevision), always use the
latter to avoid redundant lookups. The first consumer of the new
interface needs to look at extra.

Differential Revision: https://phab.mercurial-scm.org/D9780

// Copyright 2019-2020 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.

//! Minimal `RevlogIndex`, readable from standard Mercurial file format
use hg::*;
use memmap::*;
use std::fs::File;
use std::ops::Deref;
use std::path::Path;
use std::slice;

pub struct Index {
    data: Box<dyn Deref<Target = [IndexEntry]> + Send>,
}

/// A fixed sized index entry. All numbers are big endian
#[repr(C)]
pub struct IndexEntry {
    not_used_yet: [u8; 24],
    p1: Revision,
    p2: Revision,
    node: Node,
    unused_node: [u8; 12],
}

pub const INDEX_ENTRY_SIZE: usize = 64;

impl IndexEntry {
    fn parents(&self) -> [Revision; 2] {
        [Revision::from_be(self.p1), Revision::from_be(self.p1)]
    }
}

impl RevlogIndex for Index {
    fn len(&self) -> usize {
        self.data.len()
    }

    fn node(&self, rev: Revision) -> Option<&Node> {
        if rev == NULL_REVISION {
            return None;
        }
        let i = rev as usize;
        if i >= self.len() {
            None
        } else {
            Some(&self.data[i].node)
        }
    }
}

impl Graph for &Index {
    fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError> {
        let [p1, p2] = (*self).data[rev as usize].parents();
        let len = (*self).len();
        if p1 < NULL_REVISION
            || p2 < NULL_REVISION
            || p1 as usize >= len
            || p2 as usize >= len
        {
            return Err(GraphError::ParentOutOfRange(rev));
        }
        Ok([p1, p2])
    }
}

struct IndexMmap(Mmap);

impl Deref for IndexMmap {
    type Target = [IndexEntry];

    fn deref(&self) -> &[IndexEntry] {
        let ptr = self.0.as_ptr() as *const IndexEntry;
        // Any misaligned data will be ignored.
        debug_assert_eq!(
            self.0.len() % std::mem::align_of::<IndexEntry>(),
            0,
            "Misaligned data in mmap"
        );
        unsafe { slice::from_raw_parts(ptr, self.0.len() / INDEX_ENTRY_SIZE) }
    }
}

impl Index {
    pub fn load_mmap(path: impl AsRef<Path>) -> Self {
        let file = File::open(path).unwrap();
        let msg = "Index file is missing, or missing permission";
        let mmap = unsafe { MmapOptions::new().map(&file) }.expect(msg);
        Self {
            data: Box::new(IndexMmap(mmap)),
        }
    }
}