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fuchsia / third_party / rust / 8e7601e10e0e3e3f9d7d4e5cd5ea515cd1c80fcf / . / library / core / src / str / mod.rs
blob: 029abf17539136d3adcac3d69f34a18a0959ce79 [file] [log] [blame]
//! String manipulation.
//!
//! For more details, see the [`std::str`] module.
//!
//! [`std::str`]: ../../std/str/index.html
#![stable(feature = "rust1", since = "1.0.0")]
mod converts;
mod count;
mod error;
mod iter;
mod traits;
mod validations;
use self::pattern::{DoubleEndedSearcher, Pattern, ReverseSearcher, Searcher};
use crate::char::{self, EscapeDebugExtArgs};
use crate::ops::Range;
use crate::slice::{self, SliceIndex};
use crate::ub_checks::assert_unsafe_precondition;
use crate::{ascii, mem};
pub mod pattern;
mod lossy;
#[unstable(feature = "str_from_raw_parts", issue = "119206")]
pub use converts::{from_raw_parts, from_raw_parts_mut};
#[stable(feature = "rust1", since = "1.0.0")]
pub use converts::{from_utf8, from_utf8_unchecked};
#[stable(feature = "str_mut_extras", since = "1.20.0")]
pub use converts::{from_utf8_mut, from_utf8_unchecked_mut};
#[stable(feature = "rust1", since = "1.0.0")]
pub use error::{ParseBoolError, Utf8Error};
#[stable(feature = "encode_utf16", since = "1.8.0")]
pub use iter::EncodeUtf16;
#[stable(feature = "rust1", since = "1.0.0")]
#[allow(deprecated)]
pub use iter::LinesAny;
#[stable(feature = "split_ascii_whitespace", since = "1.34.0")]
pub use iter::SplitAsciiWhitespace;
#[stable(feature = "split_inclusive", since = "1.51.0")]
pub use iter::SplitInclusive;
#[stable(feature = "rust1", since = "1.0.0")]
pub use iter::{Bytes, CharIndices, Chars, Lines, SplitWhitespace};
#[stable(feature = "str_escape", since = "1.34.0")]
pub use iter::{EscapeDebug, EscapeDefault, EscapeUnicode};
#[stable(feature = "str_match_indices", since = "1.5.0")]
pub use iter::{MatchIndices, RMatchIndices};
use iter::{MatchIndicesInternal, MatchesInternal, SplitInternal, SplitNInternal};
#[stable(feature = "str_matches", since = "1.2.0")]
pub use iter::{Matches, RMatches};
#[stable(feature = "rust1", since = "1.0.0")]
pub use iter::{RSplit, RSplitTerminator, Split, SplitTerminator};
#[stable(feature = "rust1", since = "1.0.0")]
pub use iter::{RSplitN, SplitN};
#[stable(feature = "utf8_chunks", since = "1.79.0")]
pub use lossy::{Utf8Chunk, Utf8Chunks};
#[stable(feature = "rust1", since = "1.0.0")]
pub use traits::FromStr;
#[unstable(feature = "str_internals", issue = "none")]
pub use validations::{next_code_point, utf8_char_width};
#[inline(never)]
#[cold]
#[track_caller]
#[rustc_allow_const_fn_unstable(const_eval_select)]
#[cfg(not(feature = "panic_immediate_abort"))]
const fn slice_error_fail(s: &str, begin: usize, end: usize) -> ! {
crate::intrinsics::const_eval_select((s, begin, end), slice_error_fail_ct, slice_error_fail_rt)
}
#[cfg(feature = "panic_immediate_abort")]
const fn slice_error_fail(s: &str, begin: usize, end: usize) -> ! {
slice_error_fail_ct(s, begin, end)
}
#[track_caller]
const fn slice_error_fail_ct(_: &str, _: usize, _: usize) -> ! {
panic!("failed to slice string");
}
#[track_caller]
fn slice_error_fail_rt(s: &str, begin: usize, end: usize) -> ! {
const MAX_DISPLAY_LENGTH: usize = 256;
let trunc_len = s.floor_char_boundary(MAX_DISPLAY_LENGTH);
let s_trunc = &s[..trunc_len];
let ellipsis = if trunc_len < s.len() { "[...]" } else { "" };
// 1. out of bounds
if begin > s.len() || end > s.len() {
let oob_index = if begin > s.len() { begin } else { end };
panic!("byte index {oob_index} is out of bounds of `{s_trunc}`{ellipsis}");
}
// 2. begin <= end
assert!(
begin <= end,
"begin <= end ({} <= {}) when slicing `{}`{}",
begin,
end,
s_trunc,
ellipsis
);
// 3. character boundary
let index = if !s.is_char_boundary(begin) { begin } else { end };
// find the character
let char_start = s.floor_char_boundary(index);
// `char_start` must be less than len and a char boundary
let ch = s[char_start..].chars().next().unwrap();
let char_range = char_start..char_start + ch.len_utf8();
panic!(
"byte index {} is not a char boundary; it is inside {:?} (bytes {:?}) of `{}`{}",
index, ch, char_range, s_trunc, ellipsis
);
}
impl str {
/// Returns the length of `self`.
///
/// This length is in bytes, not [`char`]s or graphemes. In other words,
/// it might not be what a human considers the length of the string.
///
/// [`char`]: prim@char
///
/// # Examples
///
/// ```
/// let len = "foo".len();
/// assert_eq!(3, len);
///
/// assert_eq!("ƒoo".len(), 4); // fancy f!
/// assert_eq!("ƒoo".chars().count(), 3);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_stable(feature = "const_str_len", since = "1.39.0")]
#[rustc_diagnostic_item = "str_len"]
#[rustc_no_implicit_autorefs]
#[must_use]
#[inline]
pub const fn len(&self) -> usize {
self.as_bytes().len()
}
/// Returns `true` if `self` has a length of zero bytes.
///
/// # Examples
///
/// ```
/// let s = "";
/// assert!(s.is_empty());
///
/// let s = "not empty";
/// assert!(!s.is_empty());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_stable(feature = "const_str_is_empty", since = "1.39.0")]
#[rustc_no_implicit_autorefs]
#[must_use]
#[inline]
pub const fn is_empty(&self) -> bool {
self.len() == 0
}
/// Converts a slice of bytes to a string slice.
///
/// A string slice ([`&str`]) is made of bytes ([`u8`]), and a byte slice
/// ([`&[u8]`][byteslice]) is made of bytes, so this function converts between
/// the two. Not all byte slices are valid string slices, however: [`&str`] requires
/// that it is valid UTF-8. `from_utf8()` checks to ensure that the bytes are valid
/// UTF-8, and then does the conversion.
///
/// [`&str`]: str
/// [byteslice]: prim@slice
///
/// If you are sure that the byte slice is valid UTF-8, and you don't want to
/// incur the overhead of the validity check, there is an unsafe version of
/// this function, [`from_utf8_unchecked`], which has the same
/// behavior but skips the check.
///
/// If you need a `String` instead of a `&str`, consider
/// [`String::from_utf8`][string].
///
/// [string]: ../std/string/struct.String.html#method.from_utf8
///
/// Because you can stack-allocate a `[u8; N]`, and you can take a
/// [`&[u8]`][byteslice] of it, this function is one way to have a
/// stack-allocated string. There is an example of this in the
/// examples section below.
///
/// [byteslice]: slice
///
/// # Errors
///
/// Returns `Err` if the slice is not UTF-8 with a description as to why the
/// provided slice is not UTF-8.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// // some bytes, in a vector
/// let sparkle_heart = vec![240, 159, 146, 150];
///
/// // We can use the ? (try) operator to check if the bytes are valid
/// let sparkle_heart = str::from_utf8(&sparkle_heart)?;
///
/// assert_eq!("💖", sparkle_heart);
/// # Ok::<_, std::str::Utf8Error>(())
/// ```
///
/// Incorrect bytes:
///
/// ```
/// // some invalid bytes, in a vector
/// let sparkle_heart = vec![0, 159, 146, 150];
///
/// assert!(str::from_utf8(&sparkle_heart).is_err());
/// ```
///
/// See the docs for [`Utf8Error`] for more details on the kinds of
/// errors that can be returned.
///
/// A "stack allocated string":
///
/// ```
/// // some bytes, in a stack-allocated array
/// let sparkle_heart = [240, 159, 146, 150];
///
/// // We know these bytes are valid, so just use `unwrap()`.
/// let sparkle_heart: &str = str::from_utf8(&sparkle_heart).unwrap();
///
/// assert_eq!("💖", sparkle_heart);
/// ```
#[stable(feature = "inherent_str_constructors", since = "1.87.0")]
#[rustc_const_stable(feature = "inherent_str_constructors", since = "1.87.0")]
#[rustc_diagnostic_item = "str_inherent_from_utf8"]
pub const fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error> {
converts::from_utf8(v)
}
/// Converts a mutable slice of bytes to a mutable string slice.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// // "Hello, Rust!" as a mutable vector
/// let mut hellorust = vec![72, 101, 108, 108, 111, 44, 32, 82, 117, 115, 116, 33];
///
/// // As we know these bytes are valid, we can use `unwrap()`
/// let outstr = str::from_utf8_mut(&mut hellorust).unwrap();
///
/// assert_eq!("Hello, Rust!", outstr);
/// ```
///
/// Incorrect bytes:
///
/// ```
/// // Some invalid bytes in a mutable vector
/// let mut invalid = vec![128, 223];
///
/// assert!(str::from_utf8_mut(&mut invalid).is_err());
/// ```
/// See the docs for [`Utf8Error`] for more details on the kinds of
/// errors that can be returned.
#[stable(feature = "inherent_str_constructors", since = "1.87.0")]
#[rustc_const_stable(feature = "const_str_from_utf8", since = "1.87.0")]
#[rustc_diagnostic_item = "str_inherent_from_utf8_mut"]
pub const fn from_utf8_mut(v: &mut [u8]) -> Result<&mut str, Utf8Error> {
converts::from_utf8_mut(v)
}
/// Converts a slice of bytes to a string slice without checking
/// that the string contains valid UTF-8.
///
/// See the safe version, [`from_utf8`], for more information.
///
/// # Safety
///
/// The bytes passed in must be valid UTF-8.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// // some bytes, in a vector
/// let sparkle_heart = vec![240, 159, 146, 150];
///
/// let sparkle_heart = unsafe {
/// str::from_utf8_unchecked(&sparkle_heart)
/// };
///
/// assert_eq!("💖", sparkle_heart);
/// ```
#[inline]
#[must_use]
#[stable(feature = "inherent_str_constructors", since = "1.87.0")]
#[rustc_const_stable(feature = "inherent_str_constructors", since = "1.87.0")]
#[rustc_diagnostic_item = "str_inherent_from_utf8_unchecked"]
pub const unsafe fn from_utf8_unchecked(v: &[u8]) -> &str {
// SAFETY: converts::from_utf8_unchecked has the same safety requirements as this function.
unsafe { converts::from_utf8_unchecked(v) }
}
/// Converts a slice of bytes to a string slice without checking
/// that the string contains valid UTF-8; mutable version.
///
/// See the immutable version, [`from_utf8_unchecked()`] for documentation and safety requirements.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let mut heart = vec![240, 159, 146, 150];
/// let heart = unsafe { str::from_utf8_unchecked_mut(&mut heart) };
///
/// assert_eq!("💖", heart);
/// ```
#[inline]
#[must_use]
#[stable(feature = "inherent_str_constructors", since = "1.87.0")]
#[rustc_const_stable(feature = "inherent_str_constructors", since = "1.87.0")]
#[rustc_diagnostic_item = "str_inherent_from_utf8_unchecked_mut"]
pub const unsafe fn from_utf8_unchecked_mut(v: &mut [u8]) -> &mut str {
// SAFETY: converts::from_utf8_unchecked_mut has the same safety requirements as this function.
unsafe { converts::from_utf8_unchecked_mut(v) }
}
/// Checks that `index`-th byte is the first byte in a UTF-8 code point
/// sequence or the end of the string.
///
/// The start and end of the string (when `index == self.len()`) are
/// considered to be boundaries.
///
/// Returns `false` if `index` is greater than `self.len()`.
///
/// # Examples
///
/// ```
/// let s = "Löwe 老虎 Léopard";
/// assert!(s.is_char_boundary(0));
/// // start of `老`
/// assert!(s.is_char_boundary(6));
/// assert!(s.is_char_boundary(s.len()));
///
/// // second byte of `ö`
/// assert!(!s.is_char_boundary(2));
///
/// // third byte of `老`
/// assert!(!s.is_char_boundary(8));
/// ```
#[must_use]
#[stable(feature = "is_char_boundary", since = "1.9.0")]
#[rustc_const_stable(feature = "const_is_char_boundary", since = "1.86.0")]
#[inline]
pub const fn is_char_boundary(&self, index: usize) -> bool {
// 0 is always ok.
// Test for 0 explicitly so that it can optimize out the check
// easily and skip reading string data for that case.
// Note that optimizing `self.get(..index)` relies on this.
if index == 0 {
return true;
}
if index >= self.len() {
// For `true` we have two options:
//
// - index == self.len()
// Empty strings are valid, so return true
// - index > self.len()
// In this case return false
//
// The check is placed exactly here, because it improves generated
// code on higher opt-levels. See PR #84751 for more details.
index == self.len()
} else {
self.as_bytes()[index].is_utf8_char_boundary()
}
}
/// Finds the closest `x` not exceeding `index` where [`is_char_boundary(x)`] is `true`.
///
/// This method can help you truncate a string so that it's still valid UTF-8, but doesn't
/// exceed a given number of bytes. Note that this is done purely at the character level
/// and can still visually split graphemes, even though the underlying characters aren't
/// split. For example, the emoji 🧑‍🔬 (scientist) could be split so that the string only
/// includes 🧑 (person) instead.
///
/// [`is_char_boundary(x)`]: Self::is_char_boundary
///
/// # Examples
///
/// ```
/// #![feature(round_char_boundary)]
/// let s = "❤️🧡💛💚💙💜";
/// assert_eq!(s.len(), 26);
/// assert!(!s.is_char_boundary(13));
///
/// let closest = s.floor_char_boundary(13);
/// assert_eq!(closest, 10);
/// assert_eq!(&s[..closest], "❤️🧡");
/// ```
#[unstable(feature = "round_char_boundary", issue = "93743")]
#[inline]
pub fn floor_char_boundary(&self, index: usize) -> usize {
if index >= self.len() {
self.len()
} else {
let lower_bound = index.saturating_sub(3);
let new_index = self.as_bytes()[lower_bound..=index]
.iter()
.rposition(|b| b.is_utf8_char_boundary());
// SAFETY: we know that the character boundary will be within four bytes
unsafe { lower_bound + new_index.unwrap_unchecked() }
}
}
/// Finds the closest `x` not below `index` where [`is_char_boundary(x)`] is `true`.
///
/// If `index` is greater than the length of the string, this returns the length of the string.
///
/// This method is the natural complement to [`floor_char_boundary`]. See that method
/// for more details.
///
/// [`floor_char_boundary`]: str::floor_char_boundary
/// [`is_char_boundary(x)`]: Self::is_char_boundary
///
/// # Examples
///
/// ```
/// #![feature(round_char_boundary)]
/// let s = "❤️🧡💛💚💙💜";
/// assert_eq!(s.len(), 26);
/// assert!(!s.is_char_boundary(13));
///
/// let closest = s.ceil_char_boundary(13);
/// assert_eq!(closest, 14);
/// assert_eq!(&s[..closest], "❤️🧡💛");
/// ```
#[unstable(feature = "round_char_boundary", issue = "93743")]
#[inline]
pub fn ceil_char_boundary(&self, index: usize) -> usize {
if index >= self.len() {
self.len()
} else {
let upper_bound = Ord::min(index + 4, self.len());
self.as_bytes()[index..upper_bound]
.iter()
.position(|b| b.is_utf8_char_boundary())
.map_or(upper_bound, |pos| pos + index)
}
}
/// Converts a string slice to a byte slice. To convert the byte slice back
/// into a string slice, use the [`from_utf8`] function.
///
/// # Examples
///
/// ```
/// let bytes = "bors".as_bytes();
/// assert_eq!(b"bors", bytes);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_stable(feature = "str_as_bytes", since = "1.39.0")]
#[must_use]
#[inline(always)]
#[allow(unused_attributes)]
pub const fn as_bytes(&self) -> &[u8] {
// SAFETY: const sound because we transmute two types with the same layout
unsafe { mem::transmute(self) }
}
/// Converts a mutable string slice to a mutable byte slice.
///
/// # Safety
///
/// The caller must ensure that the content of the slice is valid UTF-8
/// before the borrow ends and the underlying `str` is used.
///
/// Use of a `str` whose contents are not valid UTF-8 is undefined behavior.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let mut s = String::from("Hello");
/// let bytes = unsafe { s.as_bytes_mut() };
///
/// assert_eq!(b"Hello", bytes);
/// ```
///
/// Mutability:
///
/// ```
/// let mut s = String::from("🗻∈🌏");
///
/// unsafe {
/// let bytes = s.as_bytes_mut();
///
/// bytes[0] = 0xF0;
/// bytes[1] = 0x9F;
/// bytes[2] = 0x8D;
/// bytes[3] = 0x94;
/// }
///
/// assert_eq!("🍔∈🌏", s);
/// ```
#[stable(feature = "str_mut_extras", since = "1.20.0")]
#[rustc_const_stable(feature = "const_str_as_mut", since = "1.83.0")]
#[must_use]
#[inline(always)]
pub const unsafe fn as_bytes_mut(&mut self) -> &mut [u8] {
// SAFETY: the cast from `&str` to `&[u8]` is safe since `str`
// has the same layout as `&[u8]` (only std can make this guarantee).
// The pointer dereference is safe since it comes from a mutable reference which
// is guaranteed to be valid for writes.
unsafe { &mut *(self as *mut str as *mut [u8]) }
}
/// Converts a string slice to a raw pointer.
///
/// As string slices are a slice of bytes, the raw pointer points to a
/// [`u8`]. This pointer will be pointing to the first byte of the string
/// slice.
///
/// The caller must ensure that the returned pointer is never written to.
/// If you need to mutate the contents of the string slice, use [`as_mut_ptr`].
///
/// [`as_mut_ptr`]: str::as_mut_ptr
///
/// # Examples
///
/// ```
/// let s = "Hello";
/// let ptr = s.as_ptr();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_stable(feature = "rustc_str_as_ptr", since = "1.32.0")]
#[rustc_never_returns_null_ptr]
#[rustc_as_ptr]
#[must_use]
#[inline(always)]
pub const fn as_ptr(&self) -> *const u8 {
self as *const str as *const u8
}
/// Converts a mutable string slice to a raw pointer.
///
/// As string slices are a slice of bytes, the raw pointer points to a
/// [`u8`]. This pointer will be pointing to the first byte of the string
/// slice.
///
/// It is your responsibility to make sure that the string slice only gets
/// modified in a way that it remains valid UTF-8.
#[stable(feature = "str_as_mut_ptr", since = "1.36.0")]
#[rustc_const_stable(feature = "const_str_as_mut", since = "1.83.0")]
#[rustc_never_returns_null_ptr]
#[rustc_as_ptr]
#[must_use]
#[inline(always)]
pub const fn as_mut_ptr(&mut self) -> *mut u8 {
self as *mut str as *mut u8
}
/// Returns a subslice of `str`.
///
/// This is the non-panicking alternative to indexing the `str`. Returns
/// [`None`] whenever equivalent indexing operation would panic.
///
/// # Examples
///
/// ```
/// let v = String::from("🗻∈🌏");
///
/// assert_eq!(Some("🗻"), v.get(0..4));
///
/// // indices not on UTF-8 sequence boundaries
/// assert!(v.get(1..).is_none());
/// assert!(v.get(..8).is_none());
///
/// // out of bounds
/// assert!(v.get(..42).is_none());
/// ```
#[stable(feature = "str_checked_slicing", since = "1.20.0")]
#[rustc_const_unstable(feature = "const_index", issue = "143775")]
#[inline]
pub const fn get<I: ~const SliceIndex<str>>(&self, i: I) -> Option<&I::Output> {
i.get(self)
}
/// Returns a mutable subslice of `str`.
///
/// This is the non-panicking alternative to indexing the `str`. Returns
/// [`None`] whenever equivalent indexing operation would panic.
///
/// # Examples
///
/// ```
/// let mut v = String::from("hello");
/// // correct length
/// assert!(v.get_mut(0..5).is_some());
/// // out of bounds
/// assert!(v.get_mut(..42).is_none());
/// assert_eq!(Some("he"), v.get_mut(0..2).map(|v| &*v));
///
/// assert_eq!("hello", v);
/// {
/// let s = v.get_mut(0..2);
/// let s = s.map(|s| {
/// s.make_ascii_uppercase();
/// &*s
/// });
/// assert_eq!(Some("HE"), s);
/// }
/// assert_eq!("HEllo", v);
/// ```
#[stable(feature = "str_checked_slicing", since = "1.20.0")]
#[rustc_const_unstable(feature = "const_index", issue = "143775")]
#[inline]
pub const fn get_mut<I: ~const SliceIndex<str>>(&mut self, i: I) -> Option<&mut I::Output> {
i.get_mut(self)
}
/// Returns an unchecked subslice of `str`.
///
/// This is the unchecked alternative to indexing the `str`.
///
/// # Safety
///
/// Callers of this function are responsible that these preconditions are
/// satisfied:
///
/// * The starting index must not exceed the ending index;
/// * Indexes must be within bounds of the original slice;
/// * Indexes must lie on UTF-8 sequence boundaries.
///
/// Failing that, the returned string slice may reference invalid memory or
/// violate the invariants communicated by the `str` type.
///
/// # Examples
///
/// ```
/// let v = "🗻∈🌏";
/// unsafe {
/// assert_eq!("🗻", v.get_unchecked(0..4));
/// assert_eq!("∈", v.get_unchecked(4..7));
/// assert_eq!("🌏", v.get_unchecked(7..11));
/// }
/// ```
#[stable(feature = "str_checked_slicing", since = "1.20.0")]
#[inline]
pub unsafe fn get_unchecked<I: SliceIndex<str>>(&self, i: I) -> &I::Output {
// SAFETY: the caller must uphold the safety contract for `get_unchecked`;
// the slice is dereferenceable because `self` is a safe reference.
// The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
unsafe { &*i.get_unchecked(self) }
}
/// Returns a mutable, unchecked subslice of `str`.
///
/// This is the unchecked alternative to indexing the `str`.
///
/// # Safety
///
/// Callers of this function are responsible that these preconditions are
/// satisfied:
///
/// * The starting index must not exceed the ending index;
/// * Indexes must be within bounds of the original slice;
/// * Indexes must lie on UTF-8 sequence boundaries.
///
/// Failing that, the returned string slice may reference invalid memory or
/// violate the invariants communicated by the `str` type.
///
/// # Examples
///
/// ```
/// let mut v = String::from("🗻∈🌏");
/// unsafe {
/// assert_eq!("🗻", v.get_unchecked_mut(0..4));
/// assert_eq!("∈", v.get_unchecked_mut(4..7));
/// assert_eq!("🌏", v.get_unchecked_mut(7..11));
/// }
/// ```
#[stable(feature = "str_checked_slicing", since = "1.20.0")]
#[inline]
pub unsafe fn get_unchecked_mut<I: SliceIndex<str>>(&mut self, i: I) -> &mut I::Output {
// SAFETY: the caller must uphold the safety contract for `get_unchecked_mut`;
// the slice is dereferenceable because `self` is a safe reference.
// The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
unsafe { &mut *i.get_unchecked_mut(self) }
}
/// Creates a string slice from another string slice, bypassing safety
/// checks.
///
/// This is generally not recommended, use with caution! For a safe
/// alternative see [`str`] and [`Index`].
///
/// [`Index`]: crate::ops::Index
///
/// This new slice goes from `begin` to `end`, including `begin` but
/// excluding `end`.
///
/// To get a mutable string slice instead, see the
/// [`slice_mut_unchecked`] method.
///
/// [`slice_mut_unchecked`]: str::slice_mut_unchecked
///
/// # Safety
///
/// Callers of this function are responsible that three preconditions are
/// satisfied:
///
/// * `begin` must not exceed `end`.
/// * `begin` and `end` must be byte positions within the string slice.
/// * `begin` and `end` must lie on UTF-8 sequence boundaries.
///
/// # Examples
///
/// ```
/// let s = "Löwe 老虎 Léopard";
///
/// unsafe {
/// assert_eq!("Löwe 老虎 Léopard", s.slice_unchecked(0, 21));
/// }
///
/// let s = "Hello, world!";
///
/// unsafe {
/// assert_eq!("world", s.slice_unchecked(7, 12));
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[deprecated(since = "1.29.0", note = "use `get_unchecked(begin..end)` instead")]
#[must_use]
#[inline]
pub unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str {
// SAFETY: the caller must uphold the safety contract for `get_unchecked`;
// the slice is dereferenceable because `self` is a safe reference.
// The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
unsafe { &*(begin..end).get_unchecked(self) }
}
/// Creates a string slice from another string slice, bypassing safety
/// checks.
///
/// This is generally not recommended, use with caution! For a safe
/// alternative see [`str`] and [`IndexMut`].
///
/// [`IndexMut`]: crate::ops::IndexMut
///
/// This new slice goes from `begin` to `end`, including `begin` but
/// excluding `end`.
///
/// To get an immutable string slice instead, see the
/// [`slice_unchecked`] method.
///
/// [`slice_unchecked`]: str::slice_unchecked
///
/// # Safety
///
/// Callers of this function are responsible that three preconditions are
/// satisfied:
///
/// * `begin` must not exceed `end`.
/// * `begin` and `end` must be byte positions within the string slice.
/// * `begin` and `end` must lie on UTF-8 sequence boundaries.
#[stable(feature = "str_slice_mut", since = "1.5.0")]
#[deprecated(since = "1.29.0", note = "use `get_unchecked_mut(begin..end)` instead")]
#[inline]
pub unsafe fn slice_mut_unchecked(&mut self, begin: usize, end: usize) -> &mut str {
// SAFETY: the caller must uphold the safety contract for `get_unchecked_mut`;
// the slice is dereferenceable because `self` is a safe reference.
// The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
unsafe { &mut *(begin..end).get_unchecked_mut(self) }
}
/// Divides one string slice into two at an index.
///
/// The argument, `mid`, should be a byte offset from the start of the
/// string. It must also be on the boundary of a UTF-8 code point.
///
/// The two slices returned go from the start of the string slice to `mid`,
/// and from `mid` to the end of the string slice.
///
/// To get mutable string slices instead, see the [`split_at_mut`]
/// method.
///
/// [`split_at_mut`]: str::split_at_mut
///
/// # Panics
///
/// Panics if `mid` is not on a UTF-8 code point boundary, or if it is past
/// the end of the last code point of the string slice. For a non-panicking
/// alternative see [`split_at_checked`](str::split_at_checked).
///
/// # Examples
///
/// ```
/// let s = "Per Martin-Löf";
///
/// let (first, last) = s.split_at(3);
///
/// assert_eq!("Per", first);
/// assert_eq!(" Martin-Löf", last);
/// ```
#[inline]
#[must_use]
#[stable(feature = "str_split_at", since = "1.4.0")]
#[rustc_const_stable(feature = "const_str_split_at", since = "1.86.0")]
pub const fn split_at(&self, mid: usize) -> (&str, &str) {
match self.split_at_checked(mid) {
None => slice_error_fail(self, 0, mid),
Some(pair) => pair,
}
}
/// Divides one mutable string slice into two at an index.
///
/// The argument, `mid`, should be a byte offset from the start of the
/// string. It must also be on the boundary of a UTF-8 code point.
///
/// The two slices returned go from the start of the string slice to `mid`,
/// and from `mid` to the end of the string slice.
///
/// To get immutable string slices instead, see the [`split_at`] method.
///
/// [`split_at`]: str::split_at
///
/// # Panics
///
/// Panics if `mid` is not on a UTF-8 code point boundary, or if it is past
/// the end of the last code point of the string slice. For a non-panicking
/// alternative see [`split_at_mut_checked`](str::split_at_mut_checked).
///
/// # Examples
///
/// ```
/// let mut s = "Per Martin-Löf".to_string();
/// {
/// let (first, last) = s.split_at_mut(3);
/// first.make_ascii_uppercase();
/// assert_eq!("PER", first);
/// assert_eq!(" Martin-Löf", last);
/// }
/// assert_eq!("PER Martin-Löf", s);
/// ```
#[inline]
#[must_use]
#[stable(feature = "str_split_at", since = "1.4.0")]
#[rustc_const_stable(feature = "const_str_split_at", since = "1.86.0")]
pub const fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str) {
// is_char_boundary checks that the index is in [0, .len()]
if self.is_char_boundary(mid) {
// SAFETY: just checked that `mid` is on a char boundary.
unsafe { self.split_at_mut_unchecked(mid) }
} else {
slice_error_fail(self, 0, mid)
}
}
/// Divides one string slice into two at an index.
///
/// The argument, `mid`, should be a valid byte offset from the start of the
/// string. It must also be on the boundary of a UTF-8 code point. The
/// method returns `None` if that’s not the case.
///
/// The two slices returned go from the start of the string slice to `mid`,
/// and from `mid` to the end of the string slice.
///
/// To get mutable string slices instead, see the [`split_at_mut_checked`]
/// method.
///
/// [`split_at_mut_checked`]: str::split_at_mut_checked
///
/// # Examples
///
/// ```
/// let s = "Per Martin-Löf";
///
/// let (first, last) = s.split_at_checked(3).unwrap();
/// assert_eq!("Per", first);
/// assert_eq!(" Martin-Löf", last);
///
/// assert_eq!(None, s.split_at_checked(13)); // Inside “ö”
/// assert_eq!(None, s.split_at_checked(16)); // Beyond the string length
/// ```
#[inline]
#[must_use]
#[stable(feature = "split_at_checked", since = "1.80.0")]
#[rustc_const_stable(feature = "const_str_split_at", since = "1.86.0")]
pub const fn split_at_checked(&self, mid: usize) -> Option<(&str, &str)> {
// is_char_boundary checks that the index is in [0, .len()]
if self.is_char_boundary(mid) {
// SAFETY: just checked that `mid` is on a char boundary.
Some(unsafe { self.split_at_unchecked(mid) })
} else {
None
}
}
/// Divides one mutable string slice into two at an index.
///
/// The argument, `mid`, should be a valid byte offset from the start of the
/// string. It must also be on the boundary of a UTF-8 code point. The
/// method returns `None` if that’s not the case.
///
/// The two slices returned go from the start of the string slice to `mid`,
/// and from `mid` to the end of the string slice.
///
/// To get immutable string slices instead, see the [`split_at_checked`] method.
///
/// [`split_at_checked`]: str::split_at_checked
///
/// # Examples
///
/// ```
/// let mut s = "Per Martin-Löf".to_string();
/// if let Some((first, last)) = s.split_at_mut_checked(3) {
/// first.make_ascii_uppercase();
/// assert_eq!("PER", first);
/// assert_eq!(" Martin-Löf", last);
/// }
/// assert_eq!("PER Martin-Löf", s);
///
/// assert_eq!(None, s.split_at_mut_checked(13)); // Inside “ö”
/// assert_eq!(None, s.split_at_mut_checked(16)); // Beyond the string length
/// ```
#[inline]
#[must_use]
#[stable(feature = "split_at_checked", since = "1.80.0")]
#[rustc_const_stable(feature = "const_str_split_at", since = "1.86.0")]
pub const fn split_at_mut_checked(&mut self, mid: usize) -> Option<(&mut str, &mut str)> {
// is_char_boundary checks that the index is in [0, .len()]
if self.is_char_boundary(mid) {
// SAFETY: just checked that `mid` is on a char boundary.
Some(unsafe { self.split_at_mut_unchecked(mid) })
} else {
None
}
}
/// Divides one string slice into two at an index.
///
/// # Safety
///
/// The caller must ensure that `mid` is a valid byte offset from the start
/// of the string and falls on the boundary of a UTF-8 code point.
#[inline]
const unsafe fn split_at_unchecked(&self, mid: usize) -> (&str, &str) {
let len = self.len();
let ptr = self.as_ptr();
// SAFETY: caller guarantees `mid` is on a char boundary.
unsafe {
(
from_utf8_unchecked(slice::from_raw_parts(ptr, mid)),
from_utf8_unchecked(slice::from_raw_parts(ptr.add(mid), len - mid)),
)
}
}
/// Divides one string slice into two at an index.
///
/// # Safety
///
/// The caller must ensure that `mid` is a valid byte offset from the start
/// of the string and falls on the boundary of a UTF-8 code point.
const unsafe fn split_at_mut_unchecked(&mut self, mid: usize) -> (&mut str, &mut str) {
let len = self.len();
let ptr = self.as_mut_ptr();
// SAFETY: caller guarantees `mid` is on a char boundary.
unsafe {
(
from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr, mid)),
from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr.add(mid), len - mid)),
)
}
}
/// Returns an iterator over the [`char`]s of a string slice.
///
/// As a string slice consists of valid UTF-8, we can iterate through a
/// string slice by [`char`]. This method returns such an iterator.
///
/// It's important to remember that [`char`] represents a Unicode Scalar
/// Value, and might not match your idea of what a 'character' is. Iteration
/// over grapheme clusters may be what you actually want. This functionality
/// is not provided by Rust's standard library, check crates.io instead.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let word = "goodbye";
///
/// let count = word.chars().count();
/// assert_eq!(7, count);
///
/// let mut chars = word.chars();
///
/// assert_eq!(Some('g'), chars.next());
/// assert_eq!(Some('o'), chars.next());
/// assert_eq!(Some('o'), chars.next());
/// assert_eq!(Some('d'), chars.next());
/// assert_eq!(Some('b'), chars.next());
/// assert_eq!(Some('y'), chars.next());
/// assert_eq!(Some('e'), chars.next());
///
/// assert_eq!(None, chars.next());
/// ```
///
/// Remember, [`char`]s might not match your intuition about characters:
///
/// [`char`]: prim@char
///
/// ```
/// let y = "y̆";
///
/// let mut chars = y.chars();
///
/// assert_eq!(Some('y'), chars.next()); // not 'y̆'
/// assert_eq!(Some('\u{0306}'), chars.next());
///
/// assert_eq!(None, chars.next());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
#[rustc_diagnostic_item = "str_chars"]
pub fn chars(&self) -> Chars<'_> {
Chars { iter: self.as_bytes().iter() }
}
/// Returns an iterator over the [`char`]s of a string slice, and their
/// positions.
///
/// As a string slice consists of valid UTF-8, we can iterate through a
/// string slice by [`char`]. This method returns an iterator of both
/// these [`char`]s, as well as their byte positions.
///
/// The iterator yields tuples. The position is first, the [`char`] is
/// second.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let word = "goodbye";
///
/// let count = word.char_indices().count();
/// assert_eq!(7, count);
///
/// let mut char_indices = word.char_indices();
///
/// assert_eq!(Some((0, 'g')), char_indices.next());
/// assert_eq!(Some((1, 'o')), char_indices.next());
/// assert_eq!(Some((2, 'o')), char_indices.next());
/// assert_eq!(Some((3, 'd')), char_indices.next());
/// assert_eq!(Some((4, 'b')), char_indices.next());
/// assert_eq!(Some((5, 'y')), char_indices.next());
/// assert_eq!(Some((6, 'e')), char_indices.next());
///
/// assert_eq!(None, char_indices.next());
/// ```
///
/// Remember, [`char`]s might not match your intuition about characters:
///
/// [`char`]: prim@char
///
/// ```
/// let yes = "y̆es";
///
/// let mut char_indices = yes.char_indices();
///
/// assert_eq!(Some((0, 'y')), char_indices.next()); // not (0, 'y̆')
/// assert_eq!(Some((1, '\u{0306}')), char_indices.next());
///
/// // note the 3 here - the previous character took up two bytes
/// assert_eq!(Some((3, 'e')), char_indices.next());
/// assert_eq!(Some((4, 's')), char_indices.next());
///
/// assert_eq!(None, char_indices.next());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn char_indices(&self) -> CharIndices<'_> {
CharIndices { front_offset: 0, iter: self.chars() }
}
/// Returns an iterator over the bytes of a string slice.
///
/// As a string slice consists of a sequence of bytes, we can iterate
/// through a string slice by byte. This method returns such an iterator.
///
/// # Examples
///
/// ```
/// let mut bytes = "bors".bytes();
///
/// assert_eq!(Some(b'b'), bytes.next());
/// assert_eq!(Some(b'o'), bytes.next());
/// assert_eq!(Some(b'r'), bytes.next());
/// assert_eq!(Some(b's'), bytes.next());
///
/// assert_eq!(None, bytes.next());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn bytes(&self) -> Bytes<'_> {
Bytes(self.as_bytes().iter().copied())
}
/// Splits a string slice by whitespace.
///
/// The iterator returned will return string slices that are sub-slices of
/// the original string slice, separated by any amount of whitespace.
///
/// 'Whitespace' is defined according to the terms of the Unicode Derived
/// Core Property `White_Space`. If you only want to split on ASCII whitespace
/// instead, use [`split_ascii_whitespace`].
///
/// [`split_ascii_whitespace`]: str::split_ascii_whitespace
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let mut iter = "A few words".split_whitespace();
///
/// assert_eq!(Some("A"), iter.next());
/// assert_eq!(Some("few"), iter.next());
/// assert_eq!(Some("words"), iter.next());
///
/// assert_eq!(None, iter.next());
/// ```
///
/// All kinds of whitespace are considered:
///
/// ```
/// let mut iter = " Mary had\ta\u{2009}little \n\t lamb".split_whitespace();
/// assert_eq!(Some("Mary"), iter.next());
/// assert_eq!(Some("had"), iter.next());
/// assert_eq!(Some("a"), iter.next());
/// assert_eq!(Some("little"), iter.next());
/// assert_eq!(Some("lamb"), iter.next());
///
/// assert_eq!(None, iter.next());
/// ```
///
/// If the string is empty or all whitespace, the iterator yields no string slices:
/// ```
/// assert_eq!("".split_whitespace().next(), None);
/// assert_eq!(" ".split_whitespace().next(), None);
/// ```
#[must_use = "this returns the split string as an iterator, \
without modifying the original"]
#[stable(feature = "split_whitespace", since = "1.1.0")]
#[rustc_diagnostic_item = "str_split_whitespace"]
#[inline]
pub fn split_whitespace(&self) -> SplitWhitespace<'_> {
SplitWhitespace { inner: self.split(IsWhitespace).filter(IsNotEmpty) }
}
/// Splits a string slice by ASCII whitespace.
///
/// The iterator returned will return string slices that are sub-slices of
/// the original string slice, separated by any amount of ASCII whitespace.
///
/// This uses the same definition as [`char::is_ascii_whitespace`].
/// To split by Unicode `Whitespace` instead, use [`split_whitespace`].
///
/// [`split_whitespace`]: str::split_whitespace
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let mut iter = "A few words".split_ascii_whitespace();
///
/// assert_eq!(Some("A"), iter.next());
/// assert_eq!(Some("few"), iter.next());
/// assert_eq!(Some("words"), iter.next());
///
/// assert_eq!(None, iter.next());
/// ```
///
/// Various kinds of ASCII whitespace are considered
/// (see [`char::is_ascii_whitespace`]):
///
/// ```
/// let mut iter = " Mary had\ta little \n\t lamb".split_ascii_whitespace();
/// assert_eq!(Some("Mary"), iter.next());
/// assert_eq!(Some("had"), iter.next());
/// assert_eq!(Some("a"), iter.next());
/// assert_eq!(Some("little"), iter.next());
/// assert_eq!(Some("lamb"), iter.next());
///
/// assert_eq!(None, iter.next());
/// ```
///
/// If the string is empty or all ASCII whitespace, the iterator yields no string slices:
/// ```
/// assert_eq!("".split_ascii_whitespace().next(), None);
/// assert_eq!(" ".split_ascii_whitespace().next(), None);
/// ```
#[must_use = "this returns the split string as an iterator, \
without modifying the original"]
#[stable(feature = "split_ascii_whitespace", since = "1.34.0")]
#[inline]
pub fn split_ascii_whitespace(&self) -> SplitAsciiWhitespace<'_> {
let inner =
self.as_bytes().split(IsAsciiWhitespace).filter(BytesIsNotEmpty).map(UnsafeBytesToStr);
SplitAsciiWhitespace { inner }
}
/// Returns an iterator over the lines of a string, as string slices.
///
/// Lines are split at line endings that are either newlines (`\n`) or
/// sequences of a carriage return followed by a line feed (`\r\n`).
///
/// Line terminators are not included in the lines returned by the iterator.
///
/// Note that any carriage return (`\r`) not immediately followed by a
/// line feed (`\n`) does not split a line. These carriage returns are
/// thereby included in the produced lines.
///
/// The final line ending is optional. A string that ends with a final line
/// ending will return the same lines as an otherwise identical string
/// without a final line ending.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let text = "foo\r\nbar\n\nbaz\r";
/// let mut lines = text.lines();
///
/// assert_eq!(Some("foo"), lines.next());
/// assert_eq!(Some("bar"), lines.next());
/// assert_eq!(Some(""), lines.next());
/// // Trailing carriage return is included in the last line
/// assert_eq!(Some("baz\r"), lines.next());
///
/// assert_eq!(None, lines.next());
/// ```
///
/// The final line does not require any ending:
///
/// ```
/// let text = "foo\nbar\n\r\nbaz";
/// let mut lines = text.lines();
///
/// assert_eq!(Some("foo"), lines.next());
/// assert_eq!(Some("bar"), lines.next());
/// assert_eq!(Some(""), lines.next());
/// assert_eq!(Some("baz"), lines.next());
///
/// assert_eq!(None, lines.next());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn lines(&self) -> Lines<'_> {
Lines(self.split_inclusive('\n').map(LinesMap))
}
/// Returns an iterator over the lines of a string.
#[stable(feature = "rust1", since = "1.0.0")]
#[deprecated(since = "1.4.0", note = "use lines() instead now", suggestion = "lines")]
#[inline]
#[allow(deprecated)]
pub fn lines_any(&self) -> LinesAny<'_> {
LinesAny(self.lines())
}
/// Returns an iterator of `u16` over the string encoded
/// as native endian UTF-16 (without byte-order mark).
///
/// # Examples
///
/// ```
/// let text = "Zażółć gęślą jaźń";
///
/// let utf8_len = text.len();
/// let utf16_len = text.encode_utf16().count();
///
/// assert!(utf16_len <= utf8_len);
/// ```
#[must_use = "this returns the encoded string as an iterator, \
without modifying the original"]
#[stable(feature = "encode_utf16", since = "1.8.0")]
pub fn encode_utf16(&self) -> EncodeUtf16<'_> {
EncodeUtf16 { chars: self.chars(), extra: 0 }
}
/// Returns `true` if the given pattern matches a sub-slice of
/// this string slice.
///
/// Returns `false` if it does not.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Examples
///
/// ```
/// let bananas = "bananas";
///
/// assert!(bananas.contains("nana"));
/// assert!(!bananas.contains("apples"));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn contains<P: Pattern>(&self, pat: P) -> bool {
pat.is_contained_in(self)
}
/// Returns `true` if the given pattern matches a prefix of this
/// string slice.
///
/// Returns `false` if it does not.
///
/// The [pattern] can be a `&str`, in which case this function will return true if
/// the `&str` is a prefix of this string slice.
///
/// The [pattern] can also be a [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
/// These will only be checked against the first character of this string slice.
/// Look at the second example below regarding behavior for slices of [`char`]s.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Examples
///
/// ```
/// let bananas = "bananas";
///
/// assert!(bananas.starts_with("bana"));
/// assert!(!bananas.starts_with("nana"));
/// ```
///
/// ```
/// let bananas = "bananas";
///
/// // Note that both of these assert successfully.
/// assert!(bananas.starts_with(&['b', 'a', 'n', 'a']));
/// assert!(bananas.starts_with(&['a', 'b', 'c', 'd']));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_diagnostic_item = "str_starts_with"]
pub fn starts_with<P: Pattern>(&self, pat: P) -> bool {
pat.is_prefix_of(self)
}
/// Returns `true` if the given pattern matches a suffix of this
/// string slice.
///
/// Returns `false` if it does not.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Examples
///
/// ```
/// let bananas = "bananas";
///
/// assert!(bananas.ends_with("anas"));
/// assert!(!bananas.ends_with("nana"));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_diagnostic_item = "str_ends_with"]
pub fn ends_with<P: Pattern>(&self, pat: P) -> bool
where
for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
{
pat.is_suffix_of(self)
}
/// Returns the byte index of the first character of this string slice that
/// matches the pattern.
///
/// Returns [`None`] if the pattern doesn't match.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Examples
///
/// Simple patterns:
///
/// ```
/// let s = "Löwe 老虎 Léopard Gepardi";
///
/// assert_eq!(s.find('L'), Some(0));
/// assert_eq!(s.find('é'), Some(14));
/// assert_eq!(s.find("pard"), Some(17));
/// ```
///
/// More complex patterns using point-free style and closures:
///
/// ```
/// let s = "Löwe 老虎 Léopard";
///
/// assert_eq!(s.find(char::is_whitespace), Some(5));
/// assert_eq!(s.find(char::is_lowercase), Some(1));
/// assert_eq!(s.find(|c: char| c.is_whitespace() || c.is_lowercase()), Some(1));
/// assert_eq!(s.find(|c: char| (c < 'o') && (c > 'a')), Some(4));
/// ```
///
/// Not finding the pattern:
///
/// ```
/// let s = "Löwe 老虎 Léopard";
/// let x: &[_] = &['1', '2'];
///
/// assert_eq!(s.find(x), None);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn find<P: Pattern>(&self, pat: P) -> Option<usize> {
pat.into_searcher(self).next_match().map(|(i, _)| i)
}
/// Returns the byte index for the first character of the last match of the pattern in
/// this string slice.
///
/// Returns [`None`] if the pattern doesn't match.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Examples
///
/// Simple patterns:
///
/// ```
/// let s = "Löwe 老虎 Léopard Gepardi";
///
/// assert_eq!(s.rfind('L'), Some(13));
/// assert_eq!(s.rfind('é'), Some(14));
/// assert_eq!(s.rfind("pard"), Some(24));
/// ```
///
/// More complex patterns with closures:
///
/// ```
/// let s = "Löwe 老虎 Léopard";
///
/// assert_eq!(s.rfind(char::is_whitespace), Some(12));
/// assert_eq!(s.rfind(char::is_lowercase), Some(20));
/// ```
///
/// Not finding the pattern:
///
/// ```
/// let s = "Löwe 老虎 Léopard";
/// let x: &[_] = &['1', '2'];
///
/// assert_eq!(s.rfind(x), None);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn rfind<P: Pattern>(&self, pat: P) -> Option<usize>
where
for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
{
pat.into_searcher(self).next_match_back().map(|(i, _)| i)
}
/// Returns an iterator over substrings of this string slice, separated by
/// characters matched by a pattern.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// If there are no matches the full string slice is returned as the only
/// item in the iterator.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Iterator behavior
///
/// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
/// allows a reverse search and forward/reverse search yields the same
/// elements. This is true for, e.g., [`char`], but not for `&str`.
///
/// If the pattern allows a reverse search but its results might differ
/// from a forward search, the [`rsplit`] method can be used.
///
/// [`rsplit`]: str::rsplit
///
/// # Examples
///
/// Simple patterns:
///
/// ```
/// let v: Vec<&str> = "Mary had a little lamb".split(' ').collect();
/// assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]);
///
/// let v: Vec<&str> = "".split('X').collect();
/// assert_eq!(v, [""]);
///
/// let v: Vec<&str> = "lionXXtigerXleopard".split('X').collect();
/// assert_eq!(v, ["lion", "", "tiger", "leopard"]);
///
/// let v: Vec<&str> = "lion::tiger::leopard".split("::").collect();
/// assert_eq!(v, ["lion", "tiger", "leopard"]);
///
/// let v: Vec<&str> = "AABBCC".split("DD").collect();
/// assert_eq!(v, ["AABBCC"]);
///
/// let v: Vec<&str> = "abc1def2ghi".split(char::is_numeric).collect();
/// assert_eq!(v, ["abc", "def", "ghi"]);
///
/// let v: Vec<&str> = "lionXtigerXleopard".split(char::is_uppercase).collect();
/// assert_eq!(v, ["lion", "tiger", "leopard"]);
/// ```
///
/// If the pattern is a slice of chars, split on each occurrence of any of the characters:
///
/// ```
/// let v: Vec<&str> = "2020-11-03 23:59".split(&['-', ' ', ':', '@'][..]).collect();
/// assert_eq!(v, ["2020", "11", "03", "23", "59"]);
/// ```
///
/// A more complex pattern, using a closure:
///
/// ```
/// let v: Vec<&str> = "abc1defXghi".split(|c| c == '1' || c == 'X').collect();
/// assert_eq!(v, ["abc", "def", "ghi"]);
/// ```
///
/// If a string contains multiple contiguous separators, you will end up
/// with empty strings in the output:
///
/// ```
/// let x = "||||a||b|c".to_string();
/// let d: Vec<_> = x.split('|').collect();
///
/// assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);
/// ```
///
/// Contiguous separators are separated by the empty string.
///
/// ```
/// let x = "(///)".to_string();
/// let d: Vec<_> = x.split('/').collect();
///
/// assert_eq!(d, &["(", "", "", ")"]);
/// ```
///
/// Separators at the start or end of a string are neighbored
/// by empty strings.
///
/// ```
/// let d: Vec<_> = "010".split("0").collect();
/// assert_eq!(d, &["", "1", ""]);
/// ```
///
/// When the empty string is used as a separator, it separates
/// every character in the string, along with the beginning
/// and end of the string.
///
/// ```
/// let f: Vec<_> = "rust".split("").collect();
/// assert_eq!(f, &["", "r", "u", "s", "t", ""]);
/// ```
///
/// Contiguous separators can lead to possibly surprising behavior
/// when whitespace is used as the separator. This code is correct:
///
/// ```
/// let x = " a b c".to_string();
/// let d: Vec<_> = x.split(' ').collect();
///
/// assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);
/// ```
///
/// It does _not_ give you:
///
/// ```,ignore
/// assert_eq!(d, &["a", "b", "c"]);
/// ```
///
/// Use [`split_whitespace`] for this behavior.
///
/// [`split_whitespace`]: str::split_whitespace
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn split<P: Pattern>(&self, pat: P) -> Split<'_, P> {
Split(SplitInternal {
start: 0,
end: self.len(),
matcher: pat.into_searcher(self),
allow_trailing_empty: true,
finished: false,
})
}
/// Returns an iterator over substrings of this string slice, separated by
/// characters matched by a pattern.
///
/// Differs from the iterator produced by `split` in that `split_inclusive`
/// leaves the matched part as the terminator of the substring.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Examples
///
/// ```
/// let v: Vec<&str> = "Mary had a little lamb\nlittle lamb\nlittle lamb."
/// .split_inclusive('\n').collect();
/// assert_eq!(v, ["Mary had a little lamb\n", "little lamb\n", "little lamb."]);
/// ```
///
/// If the last element of the string is matched,
/// that element will be considered the terminator of the preceding substring.
/// That substring will be the last item returned by the iterator.
///
/// ```
/// let v: Vec<&str> = "Mary had a little lamb\nlittle lamb\nlittle lamb.\n"
/// .split_inclusive('\n').collect();
/// assert_eq!(v, ["Mary had a little lamb\n", "little lamb\n", "little lamb.\n"]);
/// ```
#[stable(feature = "split_inclusive", since = "1.51.0")]
#[inline]
pub fn split_inclusive<P: Pattern>(&self, pat: P) -> SplitInclusive<'_, P> {
SplitInclusive(SplitInternal {
start: 0,
end: self.len(),
matcher: pat.into_searcher(self),
allow_trailing_empty: false,
finished: false,
})
}
/// Returns an iterator over substrings of the given string slice, separated
/// by characters matched by a pattern and yielded in reverse order.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Iterator behavior
///
/// The returned iterator requires that the pattern supports a reverse
/// search, and it will be a [`DoubleEndedIterator`] if a forward/reverse
/// search yields the same elements.
///
/// For iterating from the front, the [`split`] method can be used.
///
/// [`split`]: str::split
///
/// # Examples
///
/// Simple patterns:
///
/// ```
/// let v: Vec<&str> = "Mary had a little lamb".rsplit(' ').collect();
/// assert_eq!(v, ["lamb", "little", "a", "had", "Mary"]);
///
/// let v: Vec<&str> = "".rsplit('X').collect();
/// assert_eq!(v, [""]);
///
/// let v: Vec<&str> = "lionXXtigerXleopard".rsplit('X').collect();
/// assert_eq!(v, ["leopard", "tiger", "", "lion"]);
///
/// let v: Vec<&str> = "lion::tiger::leopard".rsplit("::").collect();
/// assert_eq!(v, ["leopard", "tiger", "lion"]);
/// ```
///
/// A more complex pattern, using a closure:
///
/// ```
/// let v: Vec<&str> = "abc1defXghi".rsplit(|c| c == '1' || c == 'X').collect();
/// assert_eq!(v, ["ghi", "def", "abc"]);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn rsplit<P: Pattern>(&self, pat: P) -> RSplit<'_, P>
where
for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
{
RSplit(self.split(pat).0)
}
/// Returns an iterator over substrings of the given string slice, separated
/// by characters matched by a pattern.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// Equivalent to [`split`], except that the trailing substring
/// is skipped if empty.
///
/// [`split`]: str::split
///
/// This method can be used for string data that is _terminated_,
/// rather than _separated_ by a pattern.
///
/// # Iterator behavior
///
/// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
/// allows a reverse search and forward/reverse search yields the same
/// elements. This is true for, e.g., [`char`], but not for `&str`.
///
/// If the pattern allows a reverse search but its results might differ
/// from a forward search, the [`rsplit_terminator`] method can be used.
///
/// [`rsplit_terminator`]: str::rsplit_terminator
///
/// # Examples
///
/// ```
/// let v: Vec<&str> = "A.B.".split_terminator('.').collect();
/// assert_eq!(v, ["A", "B"]);
///
/// let v: Vec<&str> = "A..B..".split_terminator(".").collect();
/// assert_eq!(v, ["A", "", "B", ""]);
///
/// let v: Vec<&str> = "A.B:C.D".split_terminator(&['.', ':'][..]).collect();
/// assert_eq!(v, ["A", "B", "C", "D"]);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn split_terminator<P: Pattern>(&self, pat: P) -> SplitTerminator<'_, P> {
SplitTerminator(SplitInternal { allow_trailing_empty: false, ..self.split(pat).0 })
}
/// Returns an iterator over substrings of `self`, separated by characters
/// matched by a pattern and yielded in reverse order.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// Equivalent to [`split`], except that the trailing substring is
/// skipped if empty.
///
/// [`split`]: str::split
///
/// This method can be used for string data that is _terminated_,
/// rather than _separated_ by a pattern.
///
/// # Iterator behavior
///
/// The returned iterator requires that the pattern supports a
/// reverse search, and it will be double ended if a forward/reverse
/// search yields the same elements.
///
/// For iterating from the front, the [`split_terminator`] method can be
/// used.
///
/// [`split_terminator`]: str::split_terminator
///
/// # Examples
///
/// ```
/// let v: Vec<&str> = "A.B.".rsplit_terminator('.').collect();
/// assert_eq!(v, ["B", "A"]);
///
/// let v: Vec<&str> = "A..B..".rsplit_terminator(".").collect();
/// assert_eq!(v, ["", "B", "", "A"]);
///
/// let v: Vec<&str> = "A.B:C.D".rsplit_terminator(&['.', ':'][..]).collect();
/// assert_eq!(v, ["D", "C", "B", "A"]);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn rsplit_terminator<P: Pattern>(&self, pat: P) -> RSplitTerminator<'_, P>
where
for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
{
RSplitTerminator(self.split_terminator(pat).0)
}
/// Returns an iterator over substrings of the given string slice, separated
/// by a pattern, restricted to returning at most `n` items.
///
/// If `n` substrings are returned, the last substring (the `n`th substring)
/// will contain the remainder of the string.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Iterator behavior
///
/// The returned iterator will not be double ended, because it is
/// not efficient to support.
///
/// If the pattern allows a reverse search, the [`rsplitn`] method can be
/// used.
///
/// [`rsplitn`]: str::rsplitn
///
/// # Examples
///
/// Simple patterns:
///
/// ```
/// let v: Vec<&str> = "Mary had a little lambda".splitn(3, ' ').collect();
/// assert_eq!(v, ["Mary", "had", "a little lambda"]);
///
/// let v: Vec<&str> = "lionXXtigerXleopard".splitn(3, "X").collect();
/// assert_eq!(v, ["lion", "", "tigerXleopard"]);
///
/// let v: Vec<&str> = "abcXdef".splitn(1, 'X').collect();
/// assert_eq!(v, ["abcXdef"]);
///
/// let v: Vec<&str> = "".splitn(1, 'X').collect();
/// assert_eq!(v, [""]);
/// ```
///
/// A more complex pattern, using a closure:
///
/// ```
/// let v: Vec<&str> = "abc1defXghi".splitn(2, |c| c == '1' || c == 'X').collect();
/// assert_eq!(v, ["abc", "defXghi"]);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn splitn<P: Pattern>(&self, n: usize, pat: P) -> SplitN<'_, P> {
SplitN(SplitNInternal { iter: self.split(pat).0, count: n })
}
/// Returns an iterator over substrings of this string slice, separated by a
/// pattern, starting from the end of the string, restricted to returning at
/// most `n` items.
///
/// If `n` substrings are returned, the last substring (the `n`th substring)
/// will contain the remainder of the string.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Iterator behavior
///
/// The returned iterator will not be double ended, because it is not
/// efficient to support.
///
/// For splitting from the front, the [`splitn`] method can be used.
///
/// [`splitn`]: str::splitn
///
/// # Examples
///
/// Simple patterns:
///
/// ```
/// let v: Vec<&str> = "Mary had a little lamb".rsplitn(3, ' ').collect();
/// assert_eq!(v, ["lamb", "little", "Mary had a"]);
///
/// let v: Vec<&str> = "lionXXtigerXleopard".rsplitn(3, 'X').collect();
/// assert_eq!(v, ["leopard", "tiger", "lionX"]);
///
/// let v: Vec<&str> = "lion::tiger::leopard".rsplitn(2, "::").collect();
/// assert_eq!(v, ["leopard", "lion::tiger"]);
/// ```
///
/// A more complex pattern, using a closure:
///
/// ```
/// let v: Vec<&str> = "abc1defXghi".rsplitn(2, |c| c == '1' || c == 'X').collect();
/// assert_eq!(v, ["ghi", "abc1def"]);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn rsplitn<P: Pattern>(&self, n: usize, pat: P) -> RSplitN<'_, P>
where
for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
{
RSplitN(self.splitn(n, pat).0)
}
/// Splits the string on the first occurrence of the specified delimiter and
/// returns prefix before delimiter and suffix after delimiter.
///
/// # Examples
///
/// ```
/// assert_eq!("cfg".split_once('='), None);
/// assert_eq!("cfg=".split_once('='), Some(("cfg", "")));
/// assert_eq!("cfg=foo".split_once('='), Some(("cfg", "foo")));
/// assert_eq!("cfg=foo=bar".split_once('='), Some(("cfg", "foo=bar")));
/// ```
#[stable(feature = "str_split_once", since = "1.52.0")]
#[inline]
pub fn split_once<P: Pattern>(&self, delimiter: P) -> Option<(&'_ str, &'_ str)> {
let (start, end) = delimiter.into_searcher(self).next_match()?;
// SAFETY: `Searcher` is known to return valid indices.
unsafe { Some((self.get_unchecked(..start), self.get_unchecked(end..))) }
}
/// Splits the string on the last occurrence of the specified delimiter and
/// returns prefix before delimiter and suffix after delimiter.
///
/// # Examples
///
/// ```
/// assert_eq!("cfg".rsplit_once('='), None);
/// assert_eq!("cfg=foo".rsplit_once('='), Some(("cfg", "foo")));
/// assert_eq!("cfg=foo=bar".rsplit_once('='), Some(("cfg=foo", "bar")));
/// ```
#[stable(feature = "str_split_once", since = "1.52.0")]
#[inline]
pub fn rsplit_once<P: Pattern>(&self, delimiter: P) -> Option<(&'_ str, &'_ str)>
where
for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
{
let (start, end) = delimiter.into_searcher(self).next_match_back()?;
// SAFETY: `Searcher` is known to return valid indices.
unsafe { Some((self.get_unchecked(..start), self.get_unchecked(end..))) }
}
/// Returns an iterator over the disjoint matches of a pattern within the
/// given string slice.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Iterator behavior
///
/// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
/// allows a reverse search and forward/reverse search yields the same
/// elements. This is true for, e.g., [`char`], but not for `&str`.
///
/// If the pattern allows a reverse search but its results might differ
/// from a forward search, the [`rmatches`] method can be used.
///
/// [`rmatches`]: str::rmatches
///
/// # Examples
///
/// ```
/// let v: Vec<&str> = "abcXXXabcYYYabc".matches("abc").collect();
/// assert_eq!(v, ["abc", "abc", "abc"]);
///
/// let v: Vec<&str> = "1abc2abc3".matches(char::is_numeric).collect();
/// assert_eq!(v, ["1", "2", "3"]);
/// ```
#[stable(feature = "str_matches", since = "1.2.0")]
#[inline]
pub fn matches<P: Pattern>(&self, pat: P) -> Matches<'_, P> {
Matches(MatchesInternal(pat.into_searcher(self)))
}
/// Returns an iterator over the disjoint matches of a pattern within this
/// string slice, yielded in reverse order.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Iterator behavior
///
/// The returned iterator requires that the pattern supports a reverse
/// search, and it will be a [`DoubleEndedIterator`] if a forward/reverse
/// search yields the same elements.
///
/// For iterating from the front, the [`matches`] method can be used.
///
/// [`matches`]: str::matches
///
/// # Examples
///
/// ```
/// let v: Vec<&str> = "abcXXXabcYYYabc".rmatches("abc").collect();
/// assert_eq!(v, ["abc", "abc", "abc"]);
///
/// let v: Vec<&str> = "1abc2abc3".rmatches(char::is_numeric).collect();
/// assert_eq!(v, ["3", "2", "1"]);
/// ```
#[stable(feature = "str_matches", since = "1.2.0")]
#[inline]
pub fn rmatches<P: Pattern>(&self, pat: P) -> RMatches<'_, P>
where
for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
{
RMatches(self.matches(pat).0)
}
/// Returns an iterator over the disjoint matches of a pattern within this string
/// slice as well as the index that the match starts at.
///
/// For matches of `pat` within `self` that overlap, only the indices
/// corresponding to the first match are returned.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Iterator behavior
///
/// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
/// allows a reverse search and forward/reverse search yields the same
/// elements. This is true for, e.g., [`char`], but not for `&str`.
///
/// If the pattern allows a reverse search but its results might differ
/// from a forward search, the [`rmatch_indices`] method can be used.
///
/// [`rmatch_indices`]: str::rmatch_indices
///
/// # Examples
///
/// ```
/// let v: Vec<_> = "abcXXXabcYYYabc".match_indices("abc").collect();
/// assert_eq!(v, [(0, "abc"), (6, "abc"), (12, "abc")]);
///
/// let v: Vec<_> = "1abcabc2".match_indices("abc").collect();
/// assert_eq!(v, [(1, "abc"), (4, "abc")]);
///
/// let v: Vec<_> = "ababa".match_indices("aba").collect();
/// assert_eq!(v, [(0, "aba")]); // only the first `aba`
/// ```
#[stable(feature = "str_match_indices", since = "1.5.0")]
#[inline]
pub fn match_indices<P: Pattern>(&self, pat: P) -> MatchIndices<'_, P> {
MatchIndices(MatchIndicesInternal(pat.into_searcher(self)))
}
/// Returns an iterator over the disjoint matches of a pattern within `self`,
/// yielded in reverse order along with the index of the match.
///
/// For matches of `pat` within `self` that overlap, only the indices
/// corresponding to the last match are returned.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Iterator behavior
///
/// The returned iterator requires that the pattern supports a reverse
/// search, and it will be a [`DoubleEndedIterator`] if a forward/reverse
/// search yields the same elements.
///
/// For iterating from the front, the [`match_indices`] method can be used.
///
/// [`match_indices`]: str::match_indices
///
/// # Examples
///
/// ```
/// let v: Vec<_> = "abcXXXabcYYYabc".rmatch_indices("abc").collect();
/// assert_eq!(v, [(12, "abc"), (6, "abc"), (0, "abc")]);
///
/// let v: Vec<_> = "1abcabc2".rmatch_indices("abc").collect();
/// assert_eq!(v, [(4, "abc"), (1, "abc")]);
///
/// let v: Vec<_> = "ababa".rmatch_indices("aba").collect();
/// assert_eq!(v, [(2, "aba")]); // only the last `aba`
/// ```
#[stable(feature = "str_match_indices", since = "1.5.0")]
#[inline]
pub fn rmatch_indices<P: Pattern>(&self, pat: P) -> RMatchIndices<'_, P>
where
for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
{
RMatchIndices(self.match_indices(pat).0)
}
/// Returns a string slice with leading and trailing whitespace removed.
///
/// 'Whitespace' is defined according to the terms of the Unicode Derived
/// Core Property `White_Space`, which includes newlines.
///
/// # Examples
///
/// ```
/// let s = "\n Hello\tworld\t\n";
///
/// assert_eq!("Hello\tworld", s.trim());
/// ```
#[inline]
#[must_use = "this returns the trimmed string as a slice, \
without modifying the original"]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_diagnostic_item = "str_trim"]
pub fn trim(&self) -> &str {
self.trim_matches(char::is_whitespace)
}
/// Returns a string slice with leading whitespace removed.
///
/// 'Whitespace' is defined according to the terms of the Unicode Derived
/// Core Property `White_Space`, which includes newlines.
///
/// # Text directionality
///
/// A string is a sequence of bytes. `start` in this context means the first
/// position of that byte string; for a left-to-right language like English or
/// Russian, this will be left side, and for right-to-left languages like
/// Arabic or Hebrew, this will be the right side.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let s = "\n Hello\tworld\t\n";
/// assert_eq!("Hello\tworld\t\n", s.trim_start());
/// ```
///
/// Directionality:
///
/// ```
/// let s = " English ";
/// assert!(Some('E') == s.trim_start().chars().next());
///
/// let s = " עברית ";
/// assert!(Some('ע') == s.trim_start().chars().next());
/// ```
#[inline]
#[must_use = "this returns the trimmed string as a new slice, \
without modifying the original"]
#[stable(feature = "trim_direction", since = "1.30.0")]
#[rustc_diagnostic_item = "str_trim_start"]
pub fn trim_start(&self) -> &str {
self.trim_start_matches(char::is_whitespace)
}
/// Returns a string slice with trailing whitespace removed.
///
/// 'Whitespace' is defined according to the terms of the Unicode Derived
/// Core Property `White_Space`, which includes newlines.
///
/// # Text directionality
///
/// A string is a sequence of bytes. `end` in this context means the last
/// position of that byte string; for a left-to-right language like English or
/// Russian, this will be right side, and for right-to-left languages like
/// Arabic or Hebrew, this will be the left side.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let s = "\n Hello\tworld\t\n";
/// assert_eq!("\n Hello\tworld", s.trim_end());
/// ```
///
/// Directionality:
///
/// ```
/// let s = " English ";
/// assert!(Some('h') == s.trim_end().chars().rev().next());
///
/// let s = " עברית ";
/// assert!(Some('ת') == s.trim_end().chars().rev().next());
/// ```
#[inline]
#[must_use = "this returns the trimmed string as a new slice, \
without modifying the original"]
#[stable(feature = "trim_direction", since = "1.30.0")]
#[rustc_diagnostic_item = "str_trim_end"]
pub fn trim_end(&self) -> &str {
self.trim_end_matches(char::is_whitespace)
}
/// Returns a string slice with leading whitespace removed.
///
/// 'Whitespace' is defined according to the terms of the Unicode Derived
/// Core Property `White_Space`.
///
/// # Text directionality
///
/// A string is a sequence of bytes. 'Left' in this context means the first
/// position of that byte string; for a language like Arabic or Hebrew
/// which are 'right to left' rather than 'left to right', this will be
/// the _right_ side, not the left.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let s = " Hello\tworld\t";
///
/// assert_eq!("Hello\tworld\t", s.trim_left());
/// ```
///
/// Directionality:
///
/// ```
/// let s = " English";
/// assert!(Some('E') == s.trim_left().chars().next());
///
/// let s = " עברית";
/// assert!(Some('ע') == s.trim_left().chars().next());
/// ```
#[must_use = "this returns the trimmed string as a new slice, \
without modifying the original"]
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
#[deprecated(since = "1.33.0", note = "superseded by `trim_start`", suggestion = "trim_start")]
pub fn trim_left(&self) -> &str {
self.trim_start()
}
/// Returns a string slice with trailing whitespace removed.
///
/// 'Whitespace' is defined according to the terms of the Unicode Derived
/// Core Property `White_Space`.
///
/// # Text directionality
///
/// A string is a sequence of bytes. 'Right' in this context means the last
/// position of that byte string; for a language like Arabic or Hebrew
/// which are 'right to left' rather than 'left to right', this will be
/// the _left_ side, not the right.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let s = " Hello\tworld\t";
///
/// assert_eq!(" Hello\tworld", s.trim_right());
/// ```
///
/// Directionality:
///
/// ```
/// let s = "English ";
/// assert!(Some('h') == s.trim_right().chars().rev().next());
///
/// let s = "עברית ";
/// assert!(Some('ת') == s.trim_right().chars().rev().next());
/// ```
#[must_use = "this returns the trimmed string as a new slice, \
without modifying the original"]
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
#[deprecated(since = "1.33.0", note = "superseded by `trim_end`", suggestion = "trim_end")]
pub fn trim_right(&self) -> &str {
self.trim_end()
}
/// Returns a string slice with all prefixes and suffixes that match a
/// pattern repeatedly removed.
///
/// The [pattern] can be a [`char`], a slice of [`char`]s, or a function
/// or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Examples
///
/// Simple patterns:
///
/// ```
/// assert_eq!("11foo1bar11".trim_matches('1'), "foo1bar");
/// assert_eq!("123foo1bar123".trim_matches(char::is_numeric), "foo1bar");
///
/// let x: &[_] = &['1', '2'];
/// assert_eq!("12foo1bar12".trim_matches(x), "foo1bar");
/// ```
///
/// A more complex pattern, using a closure:
///
/// ```
/// assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar");
/// ```
#[must_use = "this returns the trimmed string as a new slice, \
without modifying the original"]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn trim_matches<P: Pattern>(&self, pat: P) -> &str
where
for<'a> P::Searcher<'a>: DoubleEndedSearcher<'a>,
{
let mut i = 0;
let mut j = 0;
let mut matcher = pat.into_searcher(self);
if let Some((a, b)) = matcher.next_reject() {
i = a;
j = b; // Remember earliest known match, correct it below if
// last match is different
}
if let Some((_, b)) = matcher.next_reject_back() {
j = b;
}
// SAFETY: `Searcher` is known to return valid indices.
unsafe { self.get_unchecked(i..j) }
}
/// Returns a string slice with all prefixes that match a pattern
/// repeatedly removed.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Text directionality
///
/// A string is a sequence of bytes. `start` in this context means the first
/// position of that byte string; for a left-to-right language like English or
/// Russian, this will be left side, and for right-to-left languages like
/// Arabic or Hebrew, this will be the right side.
///
/// # Examples
///
/// ```
/// assert_eq!("11foo1bar11".trim_start_matches('1'), "foo1bar11");
/// assert_eq!("123foo1bar123".trim_start_matches(char::is_numeric), "foo1bar123");
///
/// let x: &[_] = &['1', '2'];
/// assert_eq!("12foo1bar12".trim_start_matches(x), "foo1bar12");
/// ```
#[must_use = "this returns the trimmed string as a new slice, \
without modifying the original"]
#[stable(feature = "trim_direction", since = "1.30.0")]
pub fn trim_start_matches<P: Pattern>(&self, pat: P) -> &str {
let mut i = self.len();
let mut matcher = pat.into_searcher(self);
if let Some((a, _)) = matcher.next_reject() {
i = a;
}
// SAFETY: `Searcher` is known to return valid indices.
unsafe { self.get_unchecked(i..self.len()) }
}
/// Returns a string slice with the prefix removed.
///
/// If the string starts with the pattern `prefix`, returns the substring after the prefix,
/// wrapped in `Some`. Unlike [`trim_start_matches`], this method removes the prefix exactly once.
///
/// If the string does not start with `prefix`, returns `None`.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
/// [`trim_start_matches`]: Self::trim_start_matches
///
/// # Examples
///
/// ```
/// assert_eq!("foo:bar".strip_prefix("foo:"), Some("bar"));
/// assert_eq!("foo:bar".strip_prefix("bar"), None);
/// assert_eq!("foofoo".strip_prefix("foo"), Some("foo"));
/// ```
#[must_use = "this returns the remaining substring as a new slice, \
without modifying the original"]
#[stable(feature = "str_strip", since = "1.45.0")]
pub fn strip_prefix<P: Pattern>(&self, prefix: P) -> Option<&str> {
prefix.strip_prefix_of(self)
}
/// Returns a string slice with the suffix removed.
///
/// If the string ends with the pattern `suffix`, returns the substring before the suffix,
/// wrapped in `Some`. Unlike [`trim_end_matches`], this method removes the suffix exactly once.
///
/// If the string does not end with `suffix`, returns `None`.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
/// [`trim_end_matches`]: Self::trim_end_matches
///
/// # Examples
///
/// ```
/// assert_eq!("bar:foo".strip_suffix(":foo"), Some("bar"));
/// assert_eq!("bar:foo".strip_suffix("bar"), None);
/// assert_eq!("foofoo".strip_suffix("foo"), Some("foo"));
/// ```
#[must_use = "this returns the remaining substring as a new slice, \
without modifying the original"]
#[stable(feature = "str_strip", since = "1.45.0")]
pub fn strip_suffix<P: Pattern>(&self, suffix: P) -> Option<&str>
where
for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
{
suffix.strip_suffix_of(self)
}
/// Returns a string slice with the optional prefix removed.
///
/// If the string starts with the pattern `prefix`, returns the substring after the prefix.
/// Unlike [`strip_prefix`], this method always returns `&str` for easy method chaining,
/// instead of returning [`Option<&str>`].
///
/// If the string does not start with `prefix`, returns the original string unchanged.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
/// [`strip_prefix`]: Self::strip_prefix
///
/// # Examples
///
/// ```
/// #![feature(trim_prefix_suffix)]
///
/// // Prefix present - removes it
/// assert_eq!("foo:bar".trim_prefix("foo:"), "bar");
/// assert_eq!("foofoo".trim_prefix("foo"), "foo");
///
/// // Prefix absent - returns original string
/// assert_eq!("foo:bar".trim_prefix("bar"), "foo:bar");
///
/// // Method chaining example
/// assert_eq!("<https://example.com/>".trim_prefix('<').trim_suffix('>'), "https://example.com/");
/// ```
#[must_use = "this returns the remaining substring as a new slice, \
without modifying the original"]
#[unstable(feature = "trim_prefix_suffix", issue = "142312")]
pub fn trim_prefix<P: Pattern>(&self, prefix: P) -> &str {
prefix.strip_prefix_of(self).unwrap_or(self)
}
/// Returns a string slice with the optional suffix removed.
///
/// If the string ends with the pattern `suffix`, returns the substring before the suffix.
/// Unlike [`strip_suffix`], this method always returns `&str` for easy method chaining,
/// instead of returning [`Option<&str>`].
///
/// If the string does not end with `suffix`, returns the original string unchanged.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
/// [`strip_suffix`]: Self::strip_suffix
///
/// # Examples
///
/// ```
/// #![feature(trim_prefix_suffix)]
///
/// // Suffix present - removes it
/// assert_eq!("bar:foo".trim_suffix(":foo"), "bar");
/// assert_eq!("foofoo".trim_suffix("foo"), "foo");
///
/// // Suffix absent - returns original string
/// assert_eq!("bar:foo".trim_suffix("bar"), "bar:foo");
///
/// // Method chaining example
/// assert_eq!("<https://example.com/>".trim_prefix('<').trim_suffix('>'), "https://example.com/");
/// ```
#[must_use = "this returns the remaining substring as a new slice, \
without modifying the original"]
#[unstable(feature = "trim_prefix_suffix", issue = "142312")]
pub fn trim_suffix<P: Pattern>(&self, suffix: P) -> &str
where
for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
{
suffix.strip_suffix_of(self).unwrap_or(self)
}
/// Returns a string slice with all suffixes that match a pattern
/// repeatedly removed.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Text directionality
///
/// A string is a sequence of bytes. `end` in this context means the last
/// position of that byte string; for a left-to-right language like English or
/// Russian, this will be right side, and for right-to-left languages like
/// Arabic or Hebrew, this will be the left side.
///
/// # Examples
///
/// Simple patterns:
///
/// ```
/// assert_eq!("11foo1bar11".trim_end_matches('1'), "11foo1bar");
/// assert_eq!("123foo1bar123".trim_end_matches(char::is_numeric), "123foo1bar");
///
/// let x: &[_] = &['1', '2'];
/// assert_eq!("12foo1bar12".trim_end_matches(x), "12foo1bar");
/// ```
///
/// A more complex pattern, using a closure:
///
/// ```
/// assert_eq!("1fooX".trim_end_matches(|c| c == '1' || c == 'X'), "1foo");
/// ```
#[must_use = "this returns the trimmed string as a new slice, \
without modifying the original"]
#[stable(feature = "trim_direction", since = "1.30.0")]
pub fn trim_end_matches<P: Pattern>(&self, pat: P) -> &str
where
for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
{
let mut j = 0;
let mut matcher = pat.into_searcher(self);
if let Some((_, b)) = matcher.next_reject_back() {
j = b;
}
// SAFETY: `Searcher` is known to return valid indices.
unsafe { self.get_unchecked(0..j) }
}
/// Returns a string slice with all prefixes that match a pattern
/// repeatedly removed.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Text directionality
///
/// A string is a sequence of bytes. 'Left' in this context means the first
/// position of that byte string; for a language like Arabic or Hebrew
/// which are 'right to left' rather than 'left to right', this will be
/// the _right_ side, not the left.
///
/// # Examples
///
/// ```
/// assert_eq!("11foo1bar11".trim_left_matches('1'), "foo1bar11");
/// assert_eq!("123foo1bar123".trim_left_matches(char::is_numeric), "foo1bar123");
///
/// let x: &[_] = &['1', '2'];
/// assert_eq!("12foo1bar12".trim_left_matches(x), "foo1bar12");
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[deprecated(
since = "1.33.0",
note = "superseded by `trim_start_matches`",
suggestion = "trim_start_matches"
)]
pub fn trim_left_matches<P: Pattern>(&self, pat: P) -> &str {
self.trim_start_matches(pat)
}
/// Returns a string slice with all suffixes that match a pattern
/// repeatedly removed.
///
/// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
/// function or closure that determines if a character matches.
///
/// [`char`]: prim@char
/// [pattern]: self::pattern
///
/// # Text directionality
///
/// A string is a sequence of bytes. 'Right' in this context means the last
/// position of that byte string; for a language like Arabic or Hebrew
/// which are 'right to left' rather than 'left to right', this will be
/// the _left_ side, not the right.
///
/// # Examples
///
/// Simple patterns:
///
/// ```
/// assert_eq!("11foo1bar11".trim_right_matches('1'), "11foo1bar");
/// assert_eq!("123foo1bar123".trim_right_matches(char::is_numeric), "123foo1bar");
///
/// let x: &[_] = &['1', '2'];
/// assert_eq!("12foo1bar12".trim_right_matches(x), "12foo1bar");
/// ```
///
/// A more complex pattern, using a closure:
///
/// ```
/// assert_eq!("1fooX".trim_right_matches(|c| c == '1' || c == 'X'), "1foo");
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[deprecated(
since = "1.33.0",
note = "superseded by `trim_end_matches`",
suggestion = "trim_end_matches"
)]
pub fn trim_right_matches<P: Pattern>(&self, pat: P) -> &str
where
for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
{
self.trim_end_matches(pat)
}
/// Parses this string slice into another type.
///
/// Because `parse` is so general, it can cause problems with type
/// inference. As such, `parse` is one of the few times you'll see
/// the syntax affectionately known as the 'turbofish': `::<>`. This
/// helps the inference algorithm understand specifically which type
/// you're trying to parse into.
///
/// `parse` can parse into any type that implements the [`FromStr`] trait.
///
/// # Errors
///
/// Will return [`Err`] if it's not possible to parse this string slice into
/// the desired type.
///
/// [`Err`]: FromStr::Err
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let four: u32 = "4".parse().unwrap();
///
/// assert_eq!(4, four);
/// ```
///
/// Using the 'turbofish' instead of annotating `four`:
///
/// ```
/// let four = "4".parse::<u32>();
///
/// assert_eq!(Ok(4), four);
/// ```
///
/// Failing to parse:
///
/// ```
/// let nope = "j".parse::<u32>();
///
/// assert!(nope.is_err());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn parse<F: FromStr>(&self) -> Result<F, F::Err> {
FromStr::from_str(self)
}
/// Checks if all characters in this string are within the ASCII range.
///
/// # Examples
///
/// ```
/// let ascii = "hello!\n";
/// let non_ascii = "Grüße, Jürgen ❤";
///
/// assert!(ascii.is_ascii());
/// assert!(!non_ascii.is_ascii());
/// ```
#[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
#[rustc_const_stable(feature = "const_slice_is_ascii", since = "1.74.0")]
#[must_use]
#[inline]
pub const fn is_ascii(&self) -> bool {
// We can treat each byte as character here: all multibyte characters
// start with a byte that is not in the ASCII range, so we will stop
// there already.
self.as_bytes().is_ascii()
}
/// If this string slice [`is_ascii`](Self::is_ascii), returns it as a slice
/// of [ASCII characters](`ascii::Char`), otherwise returns `None`.
#[unstable(feature = "ascii_char", issue = "110998")]
#[must_use]
#[inline]
pub const fn as_ascii(&self) -> Option<&[ascii::Char]> {
// Like in `is_ascii`, we can work on the bytes directly.
self.as_bytes().as_ascii()
}
/// Converts this string slice into a slice of [ASCII characters](ascii::Char),
/// without checking whether they are valid.
///
/// # Safety
///
/// Every character in this string must be ASCII, or else this is UB.
#[unstable(feature = "ascii_char", issue = "110998")]
#[must_use]
#[inline]
pub const unsafe fn as_ascii_unchecked(&self) -> &[ascii::Char] {
assert_unsafe_precondition!(
check_library_ub,
"as_ascii_unchecked requires that the string is valid ASCII",
(it: &str = self) => it.is_ascii()
);
// SAFETY: the caller promised that every byte of this string slice
// is ASCII.
unsafe { self.as_bytes().as_ascii_unchecked() }
}
/// Checks that two strings are an ASCII case-insensitive match.
///
/// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
/// but without allocating and copying temporaries.
///
/// # Examples
///
/// ```
/// assert!("Ferris".eq_ignore_ascii_case("FERRIS"));
/// assert!("Ferrös".eq_ignore_ascii_case("FERRöS"));
/// assert!(!"Ferrös".eq_ignore_ascii_case("FERRÖS"));
/// ```
#[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
#[rustc_const_stable(feature = "const_eq_ignore_ascii_case", since = "1.89.0")]
#[must_use]
#[inline]
pub const fn eq_ignore_ascii_case(&self, other: &str) -> bool {
self.as_bytes().eq_ignore_ascii_case(other.as_bytes())
}
/// Converts this string to its ASCII upper case equivalent in-place.
///
/// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
/// but non-ASCII letters are unchanged.
///
/// To return a new uppercased value without modifying the existing one, use
/// [`to_ascii_uppercase()`].
///
/// [`to_ascii_uppercase()`]: #method.to_ascii_uppercase
///
/// # Examples
///
/// ```
/// let mut s = String::from("Grüße, Jürgen ❤");
///
/// s.make_ascii_uppercase();
///
/// assert_eq!("GRüßE, JüRGEN ❤", s);
/// ```
#[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
#[rustc_const_stable(feature = "const_make_ascii", since = "1.84.0")]
#[inline]
pub const fn make_ascii_uppercase(&mut self) {
// SAFETY: changing ASCII letters only does not invalidate UTF-8.
let me = unsafe { self.as_bytes_mut() };
me.make_ascii_uppercase()
}
/// Converts this string to its ASCII lower case equivalent in-place.
///
/// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
/// but non-ASCII letters are unchanged.
///
/// To return a new lowercased value without modifying the existing one, use
/// [`to_ascii_lowercase()`].
///
/// [`to_ascii_lowercase()`]: #method.to_ascii_lowercase
///
/// # Examples
///
/// ```
/// let mut s = String::from("GRÜßE, JÜRGEN ❤");
///
/// s.make_ascii_lowercase();
///
/// assert_eq!("grÜße, jÜrgen ❤", s);
/// ```
#[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
#[rustc_const_stable(feature = "const_make_ascii", since = "1.84.0")]
#[inline]
pub const fn make_ascii_lowercase(&mut self) {
// SAFETY: changing ASCII letters only does not invalidate UTF-8.
let me = unsafe { self.as_bytes_mut() };
me.make_ascii_lowercase()
}
/// Returns a string slice with leading ASCII whitespace removed.
///
/// 'Whitespace' refers to the definition used by
/// [`u8::is_ascii_whitespace`].
///
/// [`u8::is_ascii_whitespace`]: u8::is_ascii_whitespace
///
/// # Examples
///
/// ```
/// assert_eq!(" \t \u{3000}hello world\n".trim_ascii_start(), "\u{3000}hello world\n");
/// assert_eq!(" ".trim_ascii_start(), "");
/// assert_eq!("".trim_ascii_start(), "");
/// ```
#[must_use = "this returns the trimmed string as a new slice, \
without modifying the original"]
#[stable(feature = "byte_slice_trim_ascii", since = "1.80.0")]
#[rustc_const_stable(feature = "byte_slice_trim_ascii", since = "1.80.0")]
#[inline]
pub const fn trim_ascii_start(&self) -> &str {
// SAFETY: Removing ASCII characters from a `&str` does not invalidate
// UTF-8.
unsafe { core::str::from_utf8_unchecked(self.as_bytes().trim_ascii_start()) }
}
/// Returns a string slice with trailing ASCII whitespace removed.
///
/// 'Whitespace' refers to the definition used by
/// [`u8::is_ascii_whitespace`].
///
/// [`u8::is_ascii_whitespace`]: u8::is_ascii_whitespace
///
/// # Examples
///
/// ```
/// assert_eq!("\r hello world\u{3000}\n ".trim_ascii_end(), "\r hello world\u{3000}");
/// assert_eq!(" ".trim_ascii_end(), "");
/// assert_eq!("".trim_ascii_end(), "");
/// ```
#[must_use = "this returns the trimmed string as a new slice, \
without modifying the original"]
#[stable(feature = "byte_slice_trim_ascii", since = "1.80.0")]
#[rustc_const_stable(feature = "byte_slice_trim_ascii", since = "1.80.0")]
#[inline]
pub const fn trim_ascii_end(&self) -> &str {
// SAFETY: Removing ASCII characters from a `&str` does not invalidate
// UTF-8.
unsafe { core::str::from_utf8_unchecked(self.as_bytes().trim_ascii_end()) }
}
/// Returns a string slice with leading and trailing ASCII whitespace
/// removed.
///
/// 'Whitespace' refers to the definition used by
/// [`u8::is_ascii_whitespace`].
///
/// [`u8::is_ascii_whitespace`]: u8::is_ascii_whitespace
///
/// # Examples
///
/// ```
/// assert_eq!("\r hello world\n ".trim_ascii(), "hello world");
/// assert_eq!(" ".trim_ascii(), "");
/// assert_eq!("".trim_ascii(), "");
/// ```
#[must_use = "this returns the trimmed string as a new slice, \
without modifying the original"]
#[stable(feature = "byte_slice_trim_ascii", since = "1.80.0")]
#[rustc_const_stable(feature = "byte_slice_trim_ascii", since = "1.80.0")]
#[inline]
pub const fn trim_ascii(&self) -> &str {
// SAFETY: Removing ASCII characters from a `&str` does not invalidate
// UTF-8.
unsafe { core::str::from_utf8_unchecked(self.as_bytes().trim_ascii()) }
}
/// Returns an iterator that escapes each char in `self` with [`char::escape_debug`].
///
/// Note: only extended grapheme codepoints that begin the string will be
/// escaped.
///
/// # Examples
///
/// As an iterator:
///
/// ```
/// for c in "❤\n!".escape_debug() {
/// print!("{c}");
/// }
/// println!();
/// ```
///
/// Using `println!` directly:
///
/// ```
/// println!("{}", "❤\n!".escape_debug());
/// ```
///
///
/// Both are equivalent to:
///
/// ```
/// println!("❤\\n!");
/// ```
///
/// Using `to_string`:
///
/// ```
/// assert_eq!("❤\n!".escape_debug().to_string(), "❤\\n!");
/// ```
#[must_use = "this returns the escaped string as an iterator, \
without modifying the original"]
#[stable(feature = "str_escape", since = "1.34.0")]
pub fn escape_debug(&self) -> EscapeDebug<'_> {
let mut chars = self.chars();
EscapeDebug {
inner: chars
.next()
.map(|first| first.escape_debug_ext(EscapeDebugExtArgs::ESCAPE_ALL))
.into_iter()
.flatten()
.chain(chars.flat_map(CharEscapeDebugContinue)),
}
}
/// Returns an iterator that escapes each char in `self` with [`char::escape_default`].
///
/// # Examples
///
/// As an iterator:
///
/// ```
/// for c in "❤\n!".escape_default() {
/// print!("{c}");
/// }
/// println!();
/// ```
///
/// Using `println!` directly:
///
/// ```
/// println!("{}", "❤\n!".escape_default());
/// ```
///
///
/// Both are equivalent to:
///
/// ```
/// println!("\\u{{2764}}\\n!");
/// ```
///
/// Using `to_string`:
///
/// ```
/// assert_eq!("❤\n!".escape_default().to_string(), "\\u{2764}\\n!");
/// ```
#[must_use = "this returns the escaped string as an iterator, \
without modifying the original"]
#[stable(feature = "str_escape", since = "1.34.0")]
pub fn escape_default(&self) -> EscapeDefault<'_> {
EscapeDefault { inner: self.chars().flat_map(CharEscapeDefault) }
}
/// Returns an iterator that escapes each char in `self` with [`char::escape_unicode`].
///
/// # Examples
///
/// As an iterator:
///
/// ```
/// for c in "❤\n!".escape_unicode() {
/// print!("{c}");
/// }
/// println!();
/// ```
///
/// Using `println!` directly:
///
/// ```
/// println!("{}", "❤\n!".escape_unicode());
/// ```
///
///
/// Both are equivalent to:
///
/// ```
/// println!("\\u{{2764}}\\u{{a}}\\u{{21}}");
/// ```
///
/// Using `to_string`:
///
/// ```
/// assert_eq!("❤\n!".escape_unicode().to_string(), "\\u{2764}\\u{a}\\u{21}");
/// ```
#[must_use = "this returns the escaped string as an iterator, \
without modifying the original"]
#[stable(feature = "str_escape", since = "1.34.0")]
pub fn escape_unicode(&self) -> EscapeUnicode<'_> {
EscapeUnicode { inner: self.chars().flat_map(CharEscapeUnicode) }
}
/// Returns the range that a substring points to.
///
/// Returns `None` if `substr` does not point within `self`.
///
/// Unlike [`str::find`], **this does not search through the string**.
/// Instead, it uses pointer arithmetic to find where in the string
/// `substr` is derived from.
///
/// This is useful for extending [`str::split`] and similar methods.
///
/// Note that this method may return false positives (typically either
/// `Some(0..0)` or `Some(self.len()..self.len())`) if `substr` is a
/// zero-length `str` that points at the beginning or end of another,
/// independent, `str`.
///
/// # Examples
/// ```
/// #![feature(substr_range)]
///
/// let data = "a, b, b, a";
/// let mut iter = data.split(", ").map(|s| data.substr_range(s).unwrap());
///
/// assert_eq!(iter.next(), Some(0..1));
/// assert_eq!(iter.next(), Some(3..4));
/// assert_eq!(iter.next(), Some(6..7));
/// assert_eq!(iter.next(), Some(9..10));
/// ```
#[must_use]
#[unstable(feature = "substr_range", issue = "126769")]
pub fn substr_range(&self, substr: &str) -> Option<Range<usize>> {
self.as_bytes().subslice_range(substr.as_bytes())
}
/// Returns the same string as a string slice `&str`.
///
/// This method is redundant when used directly on `&str`, but
/// it helps dereferencing other string-like types to string slices,
/// for example references to `Box<str>` or `Arc<str>`.
#[inline]
#[unstable(feature = "str_as_str", issue = "130366")]
pub fn as_str(&self) -> &str {
self
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl AsRef<[u8]> for str {
#[inline]
fn as_ref(&self) -> &[u8] {
self.as_bytes()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_unstable(feature = "const_default", issue = "143894")]
impl const Default for &str {
/// Creates an empty str
#[inline]
fn default() -> Self {
""
}
}
#[stable(feature = "default_mut_str", since = "1.28.0")]
#[rustc_const_unstable(feature = "const_default", issue = "143894")]
impl const Default for &mut str {
/// Creates an empty mutable str
#[inline]
fn default() -> Self {
// SAFETY: The empty string is valid UTF-8.
unsafe { from_utf8_unchecked_mut(&mut []) }
}
}
impl_fn_for_zst! {
/// A nameable, cloneable fn type
#[derive(Clone)]
struct LinesMap impl<'a> Fn = |line: &'a str| -> &'a str {
let Some(line) = line.strip_suffix('\n') else { return line };
let Some(line) = line.strip_suffix('\r') else { return line };
line
};
#[derive(Clone)]
struct CharEscapeDebugContinue impl Fn = |c: char| -> char::EscapeDebug {
c.escape_debug_ext(EscapeDebugExtArgs {
escape_grapheme_extended: false,
escape_single_quote: true,
escape_double_quote: true
})
};
#[derive(Clone)]
struct CharEscapeUnicode impl Fn = |c: char| -> char::EscapeUnicode {
c.escape_unicode()
};
#[derive(Clone)]
struct CharEscapeDefault impl Fn = |c: char| -> char::EscapeDefault {
c.escape_default()
};
#[derive(Clone)]
struct IsWhitespace impl Fn = |c: char| -> bool {
c.is_whitespace()
};
#[derive(Clone)]
struct IsAsciiWhitespace impl Fn = |byte: &u8| -> bool {
byte.is_ascii_whitespace()
};
#[derive(Clone)]
struct IsNotEmpty impl<'a, 'b> Fn = |s: &'a &'b str| -> bool {
!s.is_empty()
};
#[derive(Clone)]
struct BytesIsNotEmpty impl<'a, 'b> Fn = |s: &'a &'b [u8]| -> bool {
!s.is_empty()
};
#[derive(Clone)]
struct UnsafeBytesToStr impl<'a> Fn = |bytes: &'a [u8]| -> &'a str {
// SAFETY: not safe
unsafe { from_utf8_unchecked(bytes) }
};
}
// This is required to make `impl From<&str> for Box<dyn Error>` and `impl<E> From<E> for Box<dyn Error>` not overlap.
#[stable(feature = "error_in_core_neg_impl", since = "1.65.0")]
impl !crate::error::Error for &str {}