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core: Implement trim functions on byte slices

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Co-authored-by: Jubilee Young <workingjubilee@gmail.com>
This commit is contained in:
Danilo Bargen 2022-02-06 02:20:53 +01:00
parent 88fb06a1f3
commit f7448a77e4
1 changed files with 78 additions and 0 deletions
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78
library/core/src/slice/ascii.rs
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@ -80,6 +80,84 @@ pub fn make_ascii_lowercase(&mut self) {
pub fn escape_ascii(&self) -> EscapeAscii<'_> {
EscapeAscii { inner: self.iter().flat_map(EscapeByte) }
}
/// Returns a byte slice with leading ASCII whitespace bytes removed.
///
/// 'Whitespace' refers to the definition used by
/// `u8::is_ascii_whitespace`.
///
/// # Examples
///
/// ```
/// #![feature(byte_slice_trim_ascii)]
///
/// assert_eq!(b" \t hello world\n".trim_ascii_start(), b"hello world\n");
/// assert_eq!(b" ".trim_ascii_start(), b"");
/// assert_eq!(b"".trim_ascii_start(), b"");
/// ```
#[unstable(feature = "byte_slice_trim_ascii", issue = "94035")]
pub const fn trim_ascii_start(&self) -> &[u8] {
let mut bytes = self;
// Note: A pattern matching based approach (instead of indexing) allows
// making the function const.
while let [first, rest @ ..] = bytes {
if first.is_ascii_whitespace() {
bytes = rest;
} else {
break;
}
}
bytes
}
/// Returns a byte slice with trailing ASCII whitespace bytes removed.
///
/// 'Whitespace' refers to the definition used by
/// `u8::is_ascii_whitespace`.
///
/// # Examples
///
/// ```
/// #![feature(byte_slice_trim_ascii)]
///
/// assert_eq!(b"\r hello world\n ".trim_ascii_end(), b"\r hello world");
/// assert_eq!(b" ".trim_ascii_end(), b"");
/// assert_eq!(b"".trim_ascii_end(), b"");
/// ```
#[unstable(feature = "byte_slice_trim_ascii", issue = "94035")]
pub const fn trim_ascii_end(&self) -> &[u8] {
let mut bytes = self;
// Note: A pattern matching based approach (instead of indexing) allows
// making the function const.
while let [rest @ .., last] = bytes {
if last.is_ascii_whitespace() {
bytes = rest;
} else {
break;
}
}
bytes
}
/// Returns a byte slice with leading and trailing ASCII whitespace bytes
/// removed.
///
/// 'Whitespace' refers to the definition used by
/// `u8::is_ascii_whitespace`.
///
/// # Examples
///
/// ```
/// #![feature(byte_slice_trim_ascii)]
///
/// assert_eq!(b"\r hello world\n ".trim_ascii(), b"hello world");
/// assert_eq!(b" ".trim_ascii(), b"");
/// assert_eq!(b"".trim_ascii(), b"");
/// ```
#[unstable(feature = "byte_slice_trim_ascii", issue = "94035")]
pub const fn trim_ascii(&self) -> &[u8] {
self.trim_ascii_start().trim_ascii_end()
}
}
impl_fn_for_zst! {