view rust/hg-core/src/revlog/nodemap_docket.rs @ 46243:63c923fd7fa8

setup: when possible, build and bundle man pages

This makes it so the manual pages are built as part of the Python
build, and includes them in any wheel generated. This should make
Python wheels a much more useful and complete way of distributing
Mercurial binaries.

Differential Revision: https://phab.mercurial-scm.org/D9640

use memmap::Mmap;
use std::convert::TryInto;
use std::path::{Path, PathBuf};

use super::revlog::RevlogError;
use crate::repo::Repo;
use crate::utils::strip_suffix;

const ONDISK_VERSION: u8 = 1;

pub(super) struct NodeMapDocket {
    pub data_length: usize,
    // TODO: keep here more of the data from `parse()` when we need it
}

impl NodeMapDocket {
    /// Return `Ok(None)` when the caller should proceed without a persistent
    /// nodemap:
    ///
    /// * This revlog does not have a `.n` docket file (it is not generated for
    ///   small revlogs), or
    /// * The docket has an unsupported version number (repositories created by
    ///   later hg, maybe that should be a requirement instead?), or
    /// * The docket file points to a missing (likely deleted) data file (this
    ///   can happen in a rare race condition).
    pub fn read_from_file(
        repo: &Repo,
        index_path: &Path,
    ) -> Result<Option<(Self, Mmap)>, RevlogError> {
        let docket_path = index_path.with_extension("n");
        let docket_bytes = match repo.store_vfs().read(&docket_path) {
            Err(e) if e.kind() == std::io::ErrorKind::NotFound => {
                return Ok(None)
            }
            Err(e) => return Err(RevlogError::IoError(e)),
            Ok(bytes) => bytes,
        };

        let mut input = if let Some((&ONDISK_VERSION, rest)) =
            docket_bytes.split_first()
        {
            rest
        } else {
            return Ok(None);
        };
        let input = &mut input;

        let uid_size = read_u8(input)? as usize;
        let _tip_rev = read_be_u64(input)?;
        // TODO: do we care about overflow for 4 GB+ nodemap files on 32-bit
        // systems?
        let data_length = read_be_u64(input)? as usize;
        let _data_unused = read_be_u64(input)?;
        let tip_node_size = read_be_u64(input)? as usize;
        let uid = read_bytes(input, uid_size)?;
        let _tip_node = read_bytes(input, tip_node_size)?;

        let uid =
            std::str::from_utf8(uid).map_err(|_| RevlogError::Corrupted)?;
        let docket = NodeMapDocket { data_length };

        let data_path = rawdata_path(&docket_path, uid);
        // TODO: use `std::fs::read` here when the `persistent-nodemap.mmap`
        // config is false?
        match repo.store_vfs().mmap_open(&data_path) {
            Ok(mmap) => {
                if mmap.len() >= data_length {
                    Ok(Some((docket, mmap)))
                } else {
                    Err(RevlogError::Corrupted)
                }
            }
            Err(error) => {
                if error.kind() == std::io::ErrorKind::NotFound {
                    Ok(None)
                } else {
                    Err(RevlogError::IoError(error))
                }
            }
        }
    }
}

fn read_bytes<'a>(
    input: &mut &'a [u8],
    count: usize,
) -> Result<&'a [u8], RevlogError> {
    if let Some(start) = input.get(..count) {
        *input = &input[count..];
        Ok(start)
    } else {
        Err(RevlogError::Corrupted)
    }
}

fn read_u8<'a>(input: &mut &[u8]) -> Result<u8, RevlogError> {
    Ok(read_bytes(input, 1)?[0])
}

fn read_be_u64<'a>(input: &mut &[u8]) -> Result<u64, RevlogError> {
    let array = read_bytes(input, std::mem::size_of::<u64>())?
        .try_into()
        .unwrap();
    Ok(u64::from_be_bytes(array))
}

fn rawdata_path(docket_path: &Path, uid: &str) -> PathBuf {
    let docket_name = docket_path
        .file_name()
        .expect("expected a base name")
        .to_str()
        .expect("expected an ASCII file name in the store");
    let prefix = strip_suffix(docket_name, ".n.a")
        .or_else(|| strip_suffix(docket_name, ".n"))
        .expect("expected docket path in .n or .n.a");
    let name = format!("{}-{}.nd", prefix, uid);
    docket_path
        .parent()
        .expect("expected a non-root path")
        .join(name)
}