rust/hg-core/src/utils.rs

rust-parsers: switch to parse/pack_dirstate to mutate-on-loop

Both `parse_dirstate` and `pack_dirstate` can operate directly on the data
they're passed, which prevents the creation of intermediate data structures,
simplifies the function signatures and reduces boilerplate. They are exposed
directly to the Python for now, but a later patch will make use of them inside
`hg-core`.

Differential Revision: https://phab.mercurial-scm.org/D6628

pub mod files;

use std::convert::AsMut;

/// Takes a slice and copies it into an array.
///
/// # Panics
///
/// Will panic if the slice and target array don't have the same length.
pub fn copy_into_array<A, T>(slice: &[T]) -> A
where
    A: Sized + Default + AsMut<[T]>,
    T: Copy,
{
    let mut a = Default::default();
    <A as AsMut<[T]>>::as_mut(&mut a).copy_from_slice(slice);
    a
}

/// 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 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 + 1]
        } 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()
    }
}