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Genericise drain function over storage
This commit is contained in:
Sosthène Guédon
parent
7759201dd4
commit
3e7c9aa7fe
@ -68,71 +68,6 @@ pub type String<const N: usize> = StringInner<OwnedVecStorage<u8, N>>;
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/// A dynamic capacity [`String`](https://doc.rust-lang.org/std/string/struct.String.html).
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pub type StringView = StringInner<ViewVecStorage<u8>>;
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impl StringView {
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/// Removes the specified range from the string in bulk, returning all
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/// removed characters as an iterator.
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///
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/// The returned iterator keeps a mutable borrow on the string to optimize
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/// its implementation.
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///
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/// # Panics
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///
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/// Panics if the starting point or end point do not lie on a [`char`]
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/// boundary, or if they're out of bounds.
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///
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/// # Leaking
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///
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/// If the returned iterator goes out of scope without being dropped (due to
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/// [`core::mem::forget`], for example), the string may still contain a copy
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/// of any drained characters, or may have lost characters arbitrarily,
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/// including characters outside the range.
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///
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/// # Examples
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///
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/// ```
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/// use heapless::String;
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///
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/// let mut s = String::<32>::try_from("α is alpha, β is beta").unwrap();
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/// let beta_offset = s.find('β').unwrap_or(s.len());
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///
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/// // Remove the range up until the β from the string
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/// let t: String<32> = s.drain(..beta_offset).collect();
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/// assert_eq!(t, "α is alpha, ");
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/// assert_eq!(s, "β is beta");
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///
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/// // A full range clears the string, like `clear()` does
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/// s.drain(..);
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/// assert_eq!(s, "");
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/// ```
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pub fn drain<R>(&mut self, range: R) -> Drain<'_>
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where
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R: RangeBounds<usize>,
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{
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// Memory safety
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//
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// The `String` version of `Drain` does not have the memory safety issues
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// of the `Vec` version. The data is just plain bytes.
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// Because the range removal happens in `Drop`, if the `Drain` iterator is leaked,
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// the removal will not happen.
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let Range { start, end } = crate::slice::range(range, ..self.len());
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assert!(self.is_char_boundary(start));
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assert!(self.is_char_boundary(end));
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// Take out two simultaneous borrows. The &mut String won't be accessed
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// until iteration is over, in Drop.
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let self_ptr = self as *mut _;
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// SAFETY: `slice::range` and `is_char_boundary` do the appropriate bounds checks.
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let chars_iter = unsafe { self.get_unchecked(start..end) }.chars();
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Drain {
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start,
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end,
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iter: chars_iter,
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string: self_ptr,
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}
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}
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}
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impl<const N: usize> String<N> {
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/// Constructs a new, empty `String` with a fixed capacity of `N` bytes.
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///
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@ -275,7 +210,9 @@ impl<const N: usize> String<N> {
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pub fn into_bytes(self) -> Vec<u8, N> {
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self.vec
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}
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}
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impl<S: VecStorage<u8> + ?Sized> StringInner<S> {
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/// Removes the specified range from the string in bulk, returning all
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/// removed characters as an iterator.
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///
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@ -315,11 +252,30 @@ impl<const N: usize> String<N> {
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where
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R: RangeBounds<usize>,
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{
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self.as_mut_view().drain(range)
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}
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}
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// Memory safety
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//
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// The `String` version of `Drain` does not have the memory safety issues
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// of the `Vec` version. The data is just plain bytes.
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// Because the range removal happens in `Drop`, if the `Drain` iterator is leaked,
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// the removal will not happen.
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let Range { start, end } = crate::slice::range(range, ..self.len());
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assert!(self.is_char_boundary(start));
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assert!(self.is_char_boundary(end));
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// Take out two simultaneous borrows. The &mut String won't be accessed
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// until iteration is over, in Drop.
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let self_ptr = self.as_mut_view() as *mut _;
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// SAFETY: `slice::range` and `is_char_boundary` do the appropriate bounds checks.
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let chars_iter = unsafe { self.get_unchecked(start..end) }.chars();
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Drain {
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start,
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end,
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iter: chars_iter,
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string: self_ptr,
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}
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}
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impl<S: VecStorage<u8> + ?Sized> StringInner<S> {
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/// Get a reference to the `String`, erasing the `N` const-generic.
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///
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///
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@ -479,48 +479,9 @@ impl<T, const N: usize> Vec<T, N> {
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}
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new
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}
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/// Removes the specified range from the vector in bulk, returning all
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/// removed elements as an iterator. If the iterator is dropped before
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/// being fully consumed, it drops the remaining removed elements.
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///
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/// The returned iterator keeps a mutable borrow on the vector to optimize
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/// its implementation.
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///
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/// # Panics
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///
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/// Panics if the starting point is greater than the end point or if
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/// the end point is greater than the length of the vector.
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///
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/// # Leaking
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///
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/// If the returned iterator goes out of scope without being dropped (due to
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/// [`mem::forget`], for example), the vector may have lost and leaked
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/// elements arbitrarily, including elements outside the range.
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///
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/// # Examples
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///
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/// ```
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/// use heapless::Vec;
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///
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/// let mut v = Vec::<_, 8>::from_array([1, 2, 3]);
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/// let u: Vec<_, 8> = v.drain(1..).collect();
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/// assert_eq!(v, &[1]);
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/// assert_eq!(u, &[2, 3]);
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///
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/// // A full range clears the vector, like `clear()` does.
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/// v.drain(..);
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/// assert_eq!(v, &[]);
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/// ```
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pub fn drain<R>(&mut self, range: R) -> Drain<'_, T>
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where
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R: RangeBounds<usize>,
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{
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self.as_mut_view().drain(range)
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}
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}
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impl<T> VecView<T> {
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impl<T, S: VecStorage<T> + ?Sized> VecInner<T, S> {
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/// Removes the specified range from the vector in bulk, returning all
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/// removed elements as an iterator. If the iterator is dropped before
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/// being fully consumed, it drops the remaining removed elements.
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@ -573,7 +534,7 @@ impl<T> VecView<T> {
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unsafe {
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// Set `self.vec` length's to `start`, to be safe in case `Drain` is leaked.
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self.set_len(start);
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let vec = NonNull::from(self);
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let vec = NonNull::from(self.as_mut_view());
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let range_slice = slice::from_raw_parts(vec.as_ref().as_ptr().add(start), end - start);
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Drain {
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tail_start: end,
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@ -583,9 +544,7 @@ impl<T> VecView<T> {
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}
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}
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}
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}
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impl<T, S: VecStorage<T> + ?Sized> VecInner<T, S> {
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/// Get a reference to the `Vec`, erasing the `N` const-generic.
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///
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///
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