view rust/hg-core/src/utils.rs @ 46472:98e39f04d60e

upgrade: implement partial upgrade for upgrading persistent-nodemap

Upgrading repositories to use persistent nodemap should be fast and easy as it
requires only two things:

1) Updating the requirements
2) Writing a persistent-nodemap on disk

For both of the steps above, we don't need to edit existing revlogs.

This patch makes upgrade only do the above mentioned two steps if we are
only upgarding to use persistent-nodemap feature.

Since `nodemap.persist_nodemap()` assumes that there exists a nodemap file for
the given revlog if we are trying to call it, this patch adds `force` argument
to create a file if does not exist which is true in our upgrade case.

The test changes demonstrate that we no longer write nodemap files for manifest
after upgrade which I think is desirable.

Differential Revision: https://phab.mercurial-scm.org/D9936

// utils 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.

//! Contains useful functions, traits, structs, etc. for use in core.

use crate::errors::{HgError, IoErrorContext};
use crate::utils::hg_path::HgPath;
use std::{io::Write, ops::Deref};

pub mod files;
pub mod hg_path;
pub mod path_auditor;

/// Useful until rust/issues/56345 is stable
///
/// # Examples
///
/// ```
/// use crate::hg::utils::find_slice_in_slice;
///
/// let haystack = b"This is the haystack".to_vec();
/// assert_eq!(find_slice_in_slice(&haystack, b"the"), Some(8));
/// assert_eq!(find_slice_in_slice(&haystack, b"not here"), None);
/// ```
pub fn find_slice_in_slice<T>(slice: &[T], needle: &[T]) -> Option<usize>
where
    for<'a> &'a [T]: PartialEq,
{
    slice
        .windows(needle.len())
        .position(|window| window == needle)
}

/// Replaces the `from` slice with the `to` slice inside the `buf` slice.
///
/// # Examples
///
/// ```
/// use crate::hg::utils::replace_slice;
/// let mut line = b"I hate writing tests!".to_vec();
/// replace_slice(&mut line, b"hate", b"love");
/// assert_eq!(
///     line,
///     b"I love writing tests!".to_vec()
/// );
/// ```
pub fn replace_slice<T>(buf: &mut [T], from: &[T], to: &[T])
where
    T: Clone + PartialEq,
{
    if buf.len() < from.len() || from.len() != to.len() {
        return;
    }
    for i in 0..=buf.len() - from.len() {
        if buf[i..].starts_with(from) {
            buf[i..(i + from.len())].clone_from_slice(to);
        }
    }
}

pub trait SliceExt {
    fn trim_end(&self) -> &Self;
    fn trim_start(&self) -> &Self;
    fn trim(&self) -> &Self;
    fn drop_prefix(&self, needle: &Self) -> Option<&Self>;
}

#[allow(clippy::trivially_copy_pass_by_ref)]
fn is_not_whitespace(c: &u8) -> bool {
    !(*c as char).is_whitespace()
}

impl SliceExt for [u8] {
    fn trim_end(&self) -> &[u8] {
        if let Some(last) = self.iter().rposition(is_not_whitespace) {
            &self[..=last]
        } else {
            &[]
        }
    }
    fn trim_start(&self) -> &[u8] {
        if let Some(first) = self.iter().position(is_not_whitespace) {
            &self[first..]
        } else {
            &[]
        }
    }

    /// ```
    /// use hg::utils::SliceExt;
    /// assert_eq!(
    ///     b"  to trim  ".trim(),
    ///     b"to trim"
    /// );
    /// assert_eq!(
    ///     b"to trim  ".trim(),
    ///     b"to trim"
    /// );
    /// assert_eq!(
    ///     b"  to trim".trim(),
    ///     b"to trim"
    /// );
    /// ```
    fn trim(&self) -> &[u8] {
        self.trim_start().trim_end()
    }

    fn drop_prefix(&self, needle: &Self) -> Option<&Self> {
        if self.starts_with(needle) {
            Some(&self[needle.len()..])
        } else {
            None
        }
    }
}

pub trait Escaped {
    /// Return bytes escaped for display to the user
    fn escaped_bytes(&self) -> Vec<u8>;
}

impl Escaped for u8 {
    fn escaped_bytes(&self) -> Vec<u8> {
        let mut acc = vec![];
        match self {
            c @ b'\'' | c @ b'\\' => {
                acc.push(b'\\');
                acc.push(*c);
            }
            b'\t' => {
                acc.extend(br"\\t");
            }
            b'\n' => {
                acc.extend(br"\\n");
            }
            b'\r' => {
                acc.extend(br"\\r");
            }
            c if (*c < b' ' || *c >= 127) => {
                write!(acc, "\\x{:x}", self).unwrap();
            }
            c => {
                acc.push(*c);
            }
        }
        acc
    }
}

impl<'a, T: Escaped> Escaped for &'a [T] {
    fn escaped_bytes(&self) -> Vec<u8> {
        self.iter().flat_map(Escaped::escaped_bytes).collect()
    }
}

impl<T: Escaped> Escaped for Vec<T> {
    fn escaped_bytes(&self) -> Vec<u8> {
        self.deref().escaped_bytes()
    }
}

impl<'a> Escaped for &'a HgPath {
    fn escaped_bytes(&self) -> Vec<u8> {
        self.as_bytes().escaped_bytes()
    }
}

// TODO: use the str method when we require Rust 1.45
pub(crate) fn strip_suffix<'a>(s: &'a str, suffix: &str) -> Option<&'a str> {
    if s.ends_with(suffix) {
        Some(&s[..s.len() - suffix.len()])
    } else {
        None
    }
}

pub fn current_dir() -> Result<std::path::PathBuf, HgError> {
    std::env::current_dir().map_err(|error| HgError::IoError {
        error,
        context: IoErrorContext::CurrentDir,
    })
}