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// ignore-tidy-filelength //! String manipulation. //! //! For more details, see the `std::str` module. #![stable(feature = "rust1", since = "1.0.0")] use self::pattern::Pattern; use self::pattern::{Searcher, ReverseSearcher, DoubleEndedSearcher}; use crate::char; use crate::fmt::{self, Write}; use crate::iter::{Map, Cloned, FusedIterator, TrustedLen, TrustedRandomAccess, Filter}; use crate::iter::{Flatten, FlatMap, Chain}; use crate::slice::{self, SliceIndex, Split as SliceSplit}; use crate::mem; use crate::ops::Try; use crate::option; pub mod pattern; #[unstable(feature = "str_internals", issue = "0")] #[allow(missing_docs)] pub mod lossy; /// Parse a value from a string /// /// `FromStr`'s [`from_str`] method is often used implicitly, through /// [`str`]'s [`parse`] method. See [`parse`]'s documentation for examples. /// /// [`from_str`]: #tymethod.from_str /// [`str`]: ../../std/primitive.str.html /// [`parse`]: ../../std/primitive.str.html#method.parse /// /// `FromStr` does not have a lifetime parameter, and so you can only parse types /// that do not contain a lifetime parameter themselves. In other words, you can /// parse an `i32` with `FromStr`, but not a `&i32`. You can parse a struct that /// contains an `i32`, but not one that contains an `&i32`. /// /// # Examples /// /// Basic implementation of `FromStr` on an example `Point` type: /// /// ``` /// use std::str::FromStr; /// use std::num::ParseIntError; /// /// #[derive(Debug, PartialEq)] /// struct Point { /// x: i32, /// y: i32 /// } /// /// impl FromStr for Point { /// type Err = ParseIntError; /// /// fn from_str(s: &str) -> Result<Self, Self::Err> { /// let coords: Vec<&str> = s.trim_matches(|p| p == '(' || p == ')' ) /// .split(',') /// .collect(); /// /// let x_fromstr = coords[0].parse::<i32>()?; /// let y_fromstr = coords[1].parse::<i32>()?; /// /// Ok(Point { x: x_fromstr, y: y_fromstr }) /// } /// } /// /// let p = Point::from_str("(1,2)"); /// assert_eq!(p.unwrap(), Point{ x: 1, y: 2} ) /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub trait FromStr: Sized { /// The associated error which can be returned from parsing. #[stable(feature = "rust1", since = "1.0.0")] type Err; /// Parses a string `s` to return a value of this type. /// /// If parsing succeeds, return the value inside [`Ok`], otherwise /// when the string is ill-formatted return an error specific to the /// inside [`Err`]. The error type is specific to implementation of the trait. /// /// [`Ok`]: ../../std/result/enum.Result.html#variant.Ok /// [`Err`]: ../../std/result/enum.Result.html#variant.Err /// /// # Examples /// /// Basic usage with [`i32`][ithirtytwo], a type that implements `FromStr`: /// /// [ithirtytwo]: ../../std/primitive.i32.html /// /// ``` /// use std::str::FromStr; /// /// let s = "5"; /// let x = i32::from_str(s).unwrap(); /// /// assert_eq!(5, x); /// ``` #[stable(feature = "rust1", since = "1.0.0")] fn from_str(s: &str) -> Result<Self, Self::Err>; } #[stable(feature = "rust1", since = "1.0.0")] impl FromStr for bool { type Err = ParseBoolError; /// Parse a `bool` from a string. /// /// Yields a `Result<bool, ParseBoolError>`, because `s` may or may not /// actually be parseable. /// /// # Examples /// /// ``` /// use std::str::FromStr; /// /// assert_eq!(FromStr::from_str("true"), Ok(true)); /// assert_eq!(FromStr::from_str("false"), Ok(false)); /// assert!(<bool as FromStr>::from_str("not even a boolean").is_err()); /// ``` /// /// Note, in many cases, the `.parse()` method on `str` is more proper. /// /// ``` /// assert_eq!("true".parse(), Ok(true)); /// assert_eq!("false".parse(), Ok(false)); /// assert!("not even a boolean".parse::<bool>().is_err()); /// ``` #[inline] fn from_str(s: &str) -> Result<bool, ParseBoolError> { match s { "true" => Ok(true), "false" => Ok(false), _ => Err(ParseBoolError { _priv: () }), } } } /// An error returned when parsing a `bool` using [`from_str`] fails /// /// [`from_str`]: ../../std/primitive.bool.html#method.from_str #[derive(Debug, Clone, PartialEq, Eq)] #[stable(feature = "rust1", since = "1.0.0")] pub struct ParseBoolError { _priv: () } #[stable(feature = "rust1", since = "1.0.0")] impl fmt::Display for ParseBoolError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { "provided string was not `true` or `false`".fmt(f) } } /* Section: Creating a string */ /// Errors which can occur when attempting to interpret a sequence of [`u8`] /// as a string. /// /// [`u8`]: ../../std/primitive.u8.html /// /// As such, the `from_utf8` family of functions and methods for both [`String`]s /// and [`&str`]s make use of this error, for example. /// /// [`String`]: ../../std/string/struct.String.html#method.from_utf8 /// [`&str`]: ../../std/str/fn.from_utf8.html /// /// # Examples /// /// This error type’s methods can be used to create functionality /// similar to `String::from_utf8_lossy` without allocating heap memory: /// /// ``` /// fn from_utf8_lossy<F>(mut input: &[u8], mut push: F) where F: FnMut(&str) { /// loop { /// match ::std::str::from_utf8(input) { /// Ok(valid) => { /// push(valid); /// break /// } /// Err(error) => { /// let (valid, after_valid) = input.split_at(error.valid_up_to()); /// unsafe { /// push(::std::str::from_utf8_unchecked(valid)) /// } /// push("\u{FFFD}"); /// /// if let Some(invalid_sequence_length) = error.error_len() { /// input = &after_valid[invalid_sequence_length..] /// } else { /// break /// } /// } /// } /// } /// } /// ``` #[derive(Copy, Eq, PartialEq, Clone, Debug)] #[stable(feature = "rust1", since = "1.0.0")] pub struct Utf8Error { valid_up_to: usize, error_len: Option<u8>, } impl Utf8Error { /// Returns the index in the given string up to which valid UTF-8 was /// verified. /// /// It is the maximum index such that `from_utf8(&input[..index])` /// would return `Ok(_)`. /// /// # Examples /// /// Basic usage: /// /// ``` /// use std::str; /// /// // some invalid bytes, in a vector /// let sparkle_heart = vec![0, 159, 146, 150]; /// /// // std::str::from_utf8 returns a Utf8Error /// let error = str::from_utf8(&sparkle_heart).unwrap_err(); /// /// // the second byte is invalid here /// assert_eq!(1, error.valid_up_to()); /// ``` #[stable(feature = "utf8_error", since = "1.5.0")] pub fn valid_up_to(&self) -> usize { self.valid_up_to } /// Provides more information about the failure: /// /// * `None`: the end of the input was reached unexpectedly. /// `self.valid_up_to()` is 1 to 3 bytes from the end of the input. /// If a byte stream (such as a file or a network socket) is being decoded incrementally, /// this could be a valid `char` whose UTF-8 byte sequence is spanning multiple chunks. /// /// * `Some(len)`: an unexpected byte was encountered. /// The length provided is that of the invalid byte sequence /// that starts at the index given by `valid_up_to()`. /// Decoding should resume after that sequence /// (after inserting a [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD]) in case of /// lossy decoding. /// /// [U+FFFD]: ../../std/char/constant.REPLACEMENT_CHARACTER.html #[stable(feature = "utf8_error_error_len", since = "1.20.0")] pub fn error_len(&self) -> Option<usize> { self.error_len.map(|len| len as usize) } } /// 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`]: ../../std/primitive.str.html /// [`u8`]: ../../std/primitive.u8.html /// [byteslice]: ../../std/primitive.slice.html /// /// 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`][fromutf8u], which has the same /// behavior but skips the check. /// /// [fromutf8u]: fn.from_utf8_unchecked.html /// /// 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]: ../../std/primitive.slice.html /// /// # 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: /// /// ``` /// use std::str; /// /// // some bytes, in a vector /// let sparkle_heart = vec![240, 159, 146, 150]; /// /// // We know these bytes are valid, so just use `unwrap()`. /// let sparkle_heart = str::from_utf8(&sparkle_heart).unwrap(); /// /// assert_eq!("💖", sparkle_heart); /// ``` /// /// Incorrect bytes: /// /// ``` /// use std::str; /// /// // 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`][error] for more details on the kinds of /// errors that can be returned. /// /// [error]: struct.Utf8Error.html /// /// A "stack allocated string": /// /// ``` /// use std::str; /// /// // 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::from_utf8(&sparkle_heart).unwrap(); /// /// assert_eq!("💖", sparkle_heart); /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error> { run_utf8_validation(v)?; Ok(unsafe { from_utf8_unchecked(v) }) } /// Converts a mutable slice of bytes to a mutable string slice. /// /// # Examples /// /// Basic usage: /// /// ``` /// use std::str; /// /// // "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: /// /// ``` /// use std::str; /// /// // 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`][error] for more details on the kinds of /// errors that can be returned. /// /// [error]: struct.Utf8Error.html #[stable(feature = "str_mut_extras", since = "1.20.0")] pub fn from_utf8_mut(v: &mut [u8]) -> Result<&mut str, Utf8Error> { run_utf8_validation(v)?; Ok(unsafe { from_utf8_unchecked_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`][fromutf8], for more information. /// /// [fromutf8]: fn.from_utf8.html /// /// # Safety /// /// This function is unsafe because it does not check that the bytes passed to /// it are valid UTF-8. If this constraint is violated, undefined behavior /// results, as the rest of Rust assumes that [`&str`]s are valid UTF-8. /// /// [`&str`]: ../../std/primitive.str.html /// /// # Examples /// /// Basic usage: /// /// ``` /// use std::str; /// /// // 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] #[stable(feature = "rust1", since = "1.0.0")] pub unsafe fn from_utf8_unchecked(v: &[u8]) -> &str { &*(v as *const [u8] as *const str) } /// 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()`][fromutf8], for more information. /// /// [fromutf8]: fn.from_utf8_unchecked.html /// /// # Examples /// /// Basic usage: /// /// ``` /// use std::str; /// /// let mut heart = vec![240, 159, 146, 150]; /// let heart = unsafe { str::from_utf8_unchecked_mut(&mut heart) }; /// /// assert_eq!("💖", heart); /// ``` #[inline] #[stable(feature = "str_mut_extras", since = "1.20.0")] pub unsafe fn from_utf8_unchecked_mut(v: &mut [u8]) -> &mut str { &mut *(v as *mut [u8] as *mut str) } #[stable(feature = "rust1", since = "1.0.0")] impl fmt::Display for Utf8Error { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { if let Some(error_len) = self.error_len { write!(f, "invalid utf-8 sequence of {} bytes from index {}", error_len, self.valid_up_to) } else { write!(f, "incomplete utf-8 byte sequence from index {}", self.valid_up_to) } } } /* Section: Iterators */ /// An iterator over the [`char`]s of a string slice. /// /// [`char`]: ../../std/primitive.char.html /// /// This struct is created by the [`chars`] method on [`str`]. /// See its documentation for more. /// /// [`chars`]: ../../std/primitive.str.html#method.chars /// [`str`]: ../../std/primitive.str.html #[derive(Clone, Debug)] #[stable(feature = "rust1", since = "1.0.0")] pub struct Chars<'a> { iter: slice::Iter<'a, u8> } /// Returns the initial codepoint accumulator for the first byte. /// The first byte is special, only want bottom 5 bits for width 2, 4 bits /// for width 3, and 3 bits for width 4. #[inline] fn utf8_first_byte(byte: u8, width: u32) -> u32 { (byte & (0x7F >> width)) as u32 } /// Returns the value of `ch` updated with continuation byte `byte`. #[inline] fn utf8_acc_cont_byte(ch: u32, byte: u8) -> u32 { (ch << 6) | (byte & CONT_MASK) as u32 } /// Checks whether the byte is a UTF-8 continuation byte (i.e., starts with the /// bits `10`). #[inline] fn utf8_is_cont_byte(byte: u8) -> bool { (byte & !CONT_MASK) == TAG_CONT_U8 } #[inline] fn unwrap_or_0(opt: Option<&u8>) -> u8 { match opt { Some(&byte) => byte, None => 0, } } /// Reads the next code point out of a byte iterator (assuming a /// UTF-8-like encoding). #[unstable(feature = "str_internals", issue = "0")] #[inline] pub fn next_code_point<'a, I: Iterator<Item = &'a u8>>(bytes: &mut I) -> Option<u32> { // Decode UTF-8 let x = *bytes.next()?; if x < 128 { return Some(x as u32) } // Multibyte case follows // Decode from a byte combination out of: [[[x y] z] w] // NOTE: Performance is sensitive to the exact formulation here let init = utf8_first_byte(x, 2); let y = unwrap_or_0(bytes.next()); let mut ch = utf8_acc_cont_byte(init, y); if x >= 0xE0 { // [[x y z] w] case // 5th bit in 0xE0 .. 0xEF is always clear, so `init` is still valid let z = unwrap_or_0(bytes.next()); let y_z = utf8_acc_cont_byte((y & CONT_MASK) as u32, z); ch = init << 12 | y_z; if x >= 0xF0 { // [x y z w] case // use only the lower 3 bits of `init` let w = unwrap_or_0(bytes.next()); ch = (init & 7) << 18 | utf8_acc_cont_byte(y_z, w); } } Some(ch) } /// Reads the last code point out of a byte iterator (assuming a /// UTF-8-like encoding). #[inline] fn next_code_point_reverse<'a, I>(bytes: &mut I) -> Option<u32> where I: DoubleEndedIterator<Item = &'a u8>, { // Decode UTF-8 let w = match *bytes.next_back()? { next_byte if next_byte < 128 => return Some(next_byte as u32), back_byte => back_byte, }; // Multibyte case follows // Decode from a byte combination out of: [x [y [z w]]] let mut ch; let z = unwrap_or_0(bytes.next_back()); ch = utf8_first_byte(z, 2); if utf8_is_cont_byte(z) { let y = unwrap_or_0(bytes.next_back()); ch = utf8_first_byte(y, 3); if utf8_is_cont_byte(y) { let x = unwrap_or_0(bytes.next_back()); ch = utf8_first_byte(x, 4); ch = utf8_acc_cont_byte(ch, y); } ch = utf8_acc_cont_byte(ch, z); } ch = utf8_acc_cont_byte(ch, w); Some(ch) } #[stable(feature = "rust1", since = "1.0.0")] impl<'a> Iterator for Chars<'a> { type Item = char; #[inline] fn next(&mut self) -> Option<char> { next_code_point(&mut self.iter).map(|ch| { // str invariant says `ch` is a valid Unicode Scalar Value unsafe { char::from_u32_unchecked(ch) } }) } #[inline] fn count(self) -> usize { // length in `char` is equal to the number of non-continuation bytes let bytes_len = self.iter.len(); let mut cont_bytes = 0; for &byte in self.iter { cont_bytes += utf8_is_cont_byte(byte) as usize; } bytes_len - cont_bytes } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { let len = self.iter.len(); // `(len + 3)` can't overflow, because we know that the `slice::Iter` // belongs to a slice in memory which has a maximum length of // `isize::MAX` (that's well below `usize::MAX`). ((len + 3) / 4, Some(len)) } #[inline] fn last(mut self) -> Option<char> { // No need to go through the entire string. self.next_back() } } #[stable(feature = "rust1", since = "1.0.0")] impl<'a> DoubleEndedIterator for Chars<'a> { #[inline] fn next_back(&mut self) -> Option<char> { next_code_point_reverse(&mut self.iter).map(|ch| { // str invariant says `ch` is a valid Unicode Scalar Value unsafe { char::from_u32_unchecked(ch) } }) } } #[stable(feature = "fused", since = "1.26.0")] impl FusedIterator for Chars<'_> {} impl<'a> Chars<'a> { /// Views the underlying data as a subslice of the original data. /// /// This has the same lifetime as the original slice, and so the /// iterator can continue to be used while this exists. /// /// # Examples /// /// ``` /// let mut chars = "abc".chars(); /// /// assert_eq!(chars.as_str(), "abc"); /// chars.next(); /// assert_eq!(chars.as_str(), "bc"); /// chars.next(); /// chars.next(); /// assert_eq!(chars.as_str(), ""); /// ``` #[stable(feature = "iter_to_slice", since = "1.4.0")] #[inline] pub fn as_str(&self) -> &'a str { unsafe { from_utf8_unchecked(self.iter.as_slice()) } } } /// An iterator over the [`char`]s of a string slice, and their positions. /// /// [`char`]: ../../std/primitive.char.html /// /// This struct is created by the [`char_indices`] method on [`str`]. /// See its documentation for more. /// /// [`char_indices`]: ../../std/primitive.str.html#method.char_indices /// [`str`]: ../../std/primitive.str.html #[derive(Clone, Debug)] #[stable(feature = "rust1", since = "1.0.0")] pub struct CharIndices<'a> { front_offset: usize, iter: Chars<'a>, } #[stable(feature = "rust1", since = "1.0.0")] impl<'a> Iterator for CharIndices<'a> { type Item = (usize, char); #[inline] fn next(&mut self) -> Option<(usize, char)> { let pre_len = self.iter.iter.len(); match self.iter.next() { None => None, Some(ch) => { let index = self.front_offset; let len = self.iter.iter.len(); self.front_offset += pre_len - len; Some((index, ch)) } } } #[inline] fn count(self) -> usize { self.iter.count() } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() } #[inline] fn last(mut self) -> Option<(usize, char)> { // No need to go through the entire string. self.next_back() } } #[stable(feature = "rust1", since = "1.0.0")] impl<'a> DoubleEndedIterator for CharIndices<'a> { #[inline] fn next_back(&mut self) -> Option<(usize, char)> { self.iter.next_back().map(|ch| { let index = self.front_offset + self.iter.iter.len(); (index, ch) }) } } #[stable(feature = "fused", since = "1.26.0")] impl FusedIterator for CharIndices<'_> {} impl<'a> CharIndices<'a> { /// Views the underlying data as a subslice of the original data. /// /// This has the same lifetime as the original slice, and so the /// iterator can continue to be used while this exists. #[stable(feature = "iter_to_slice", since = "1.4.0")] #[inline] pub fn as_str(&self) -> &'a str { self.iter.as_str() } } /// An iterator over the bytes of a string slice. /// /// This struct is created by the [`bytes`] method on [`str`]. /// See its documentation for more. /// /// [`bytes`]: ../../std/primitive.str.html#method.bytes /// [`str`]: ../../std/primitive.str.html #[stable(feature = "rust1", since = "1.0.0")] #[derive(Clone, Debug)] pub struct Bytes<'a>(Cloned<slice::Iter<'a, u8>>); #[stable(feature = "rust1", since = "1.0.0")] impl Iterator for Bytes<'_> { type Item = u8; #[inline] fn next(&mut self) -> Option<u8> { self.0.next() } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() } #[inline] fn count(self) -> usize { self.0.count() } #[inline] fn last(self) -> Option<Self::Item> { self.0.last() } #[inline] fn nth(&mut self, n: usize) -> Option<Self::Item> { self.0.nth(n) } #[inline] fn all<F>(&mut self, f: F) -> bool where F: FnMut(Self::Item) -> bool { self.0.all(f) } #[inline] fn any<F>(&mut self, f: F) -> bool where F: FnMut(Self::Item) -> bool { self.0.any(f) } #[inline] fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where P: FnMut(&Self::Item) -> bool { self.0.find(predicate) } #[inline] fn position<P>(&mut self, predicate: P) -> Option<usize> where P: FnMut(Self::Item) -> bool { self.0.position(predicate) } #[inline] fn rposition<P>(&mut self, predicate: P) -> Option<usize> where P: FnMut(Self::Item) -> bool { self.0.rposition(predicate) } } #[stable(feature = "rust1", since = "1.0.0")] impl DoubleEndedIterator for Bytes<'_> { #[inline] fn next_back(&mut self) -> Option<u8> { self.0.next_back() } #[inline] fn nth_back(&mut self, n: usize) -> Option<Self::Item> { self.0.nth_back(n) } #[inline] fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item> where P: FnMut(&Self::Item) -> bool { self.0.rfind(predicate) } } #[stable(feature = "rust1", since = "1.0.0")] impl ExactSizeIterator for Bytes<'_> { #[inline] fn len(&self) -> usize { self.0.len() } #[inline] fn is_empty(&self) -> bool { self.0.is_empty() } } #[stable(feature = "fused", since = "1.26.0")] impl FusedIterator for Bytes<'_> {} #[unstable(feature = "trusted_len", issue = "37572")] unsafe impl TrustedLen for Bytes<'_> {} #[doc(hidden)] unsafe impl TrustedRandomAccess for Bytes<'_> { unsafe fn get_unchecked(&mut self, i: usize) -> u8 { self.0.get_unchecked(i) } fn may_have_side_effect() -> bool { false } } /// This macro generates a Clone impl for string pattern API /// wrapper types of the form X<'a, P> macro_rules! derive_pattern_clone { (clone $t:ident with |$s:ident| $e:expr) => { impl<'a, P: Pattern<'a>> Clone for $t<'a, P> where P::Searcher: Clone { fn clone(&self) -> Self { let $s = self; $e } } } } /// This macro generates two public iterator structs /// wrapping a private internal one that makes use of the `Pattern` API. /// /// For all patterns `P: Pattern<'a>` the following items will be /// generated (generics omitted): /// /// struct $forward_iterator($internal_iterator); /// struct $reverse_iterator($internal_iterator); /// /// impl Iterator for $forward_iterator /// { /* internal ends up calling Searcher::next_match() */ } /// /// impl DoubleEndedIterator for $forward_iterator /// where P::Searcher: DoubleEndedSearcher /// { /* internal ends up calling Searcher::next_match_back() */ } /// /// impl Iterator for $reverse_iterator /// where P::Searcher: ReverseSearcher /// { /* internal ends up calling Searcher::next_match_back() */ } /// /// impl DoubleEndedIterator for $reverse_iterator /// where P::Searcher: DoubleEndedSearcher /// { /* internal ends up calling Searcher::next_match() */ } /// /// The internal one is defined outside the macro, and has almost the same /// semantic as a DoubleEndedIterator by delegating to `pattern::Searcher` and /// `pattern::ReverseSearcher` for both forward and reverse iteration. /// /// "Almost", because a `Searcher` and a `ReverseSearcher` for a given /// `Pattern` might not return the same elements, so actually implementing /// `DoubleEndedIterator` for it would be incorrect. /// (See the docs in `str::pattern` for more details) /// /// However, the internal struct still represents a single ended iterator from /// either end, and depending on pattern is also a valid double ended iterator, /// so the two wrapper structs implement `Iterator` /// and `DoubleEndedIterator` depending on the concrete pattern type, leading /// to the complex impls seen above. macro_rules! generate_pattern_iterators { { // Forward iterator forward: $(#[$forward_iterator_attribute:meta])* struct $forward_iterator:ident; // Reverse iterator reverse: $(#[$reverse_iterator_attribute:meta])* struct $reverse_iterator:ident; // Stability of all generated items stability: $(#[$common_stability_attribute:meta])* // Internal almost-iterator that is being delegated to internal: $internal_iterator:ident yielding ($iterty:ty); // Kind of delegation - either single ended or double ended delegate $($t:tt)* } => { $(#[$forward_iterator_attribute])* $(#[$common_stability_attribute])* pub struct $forward_iterator<'a, P: Pattern<'a>>($internal_iterator<'a, P>); $(#[$common_stability_attribute])* impl<'a, P: Pattern<'a>> fmt::Debug for $forward_iterator<'a, P> where P::Searcher: fmt::Debug { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.debug_tuple(stringify!($forward_iterator)) .field(&self.0) .finish() } } $(#[$common_stability_attribute])* impl<'a, P: Pattern<'a>> Iterator for $forward_iterator<'a, P> { type Item = $iterty; #[inline] fn next(&mut self) -> Option<$iterty> { self.0.next() } } $(#[$common_stability_attribute])* impl<'a, P: Pattern<'a>> Clone for $forward_iterator<'a, P> where P::Searcher: Clone { fn clone(&self) -> Self { $forward_iterator(self.0.clone()) } } $(#[$reverse_iterator_attribute])* $(#[$common_stability_attribute])* pub struct $reverse_iterator<'a, P: Pattern<'a>>($internal_iterator<'a, P>); $(#[$common_stability_attribute])* impl<'a, P: Pattern<'a>> fmt::Debug for $reverse_iterator<'a, P> where P::Searcher: fmt::Debug { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.debug_tuple(stringify!($reverse_iterator)) .field(&self.0) .finish() } } $(#[$common_stability_attribute])* impl<'a, P: Pattern<'a>> Iterator for $reverse_iterator<'a, P> where P::Searcher: ReverseSearcher<'a> { type Item = $iterty; #[inline] fn next(&mut self) -> Option<$iterty> { self.0.next_back() } } $(#[$common_stability_attribute])* impl<'a, P: Pattern<'a>> Clone for $reverse_iterator<'a, P> where P::Searcher: Clone { fn clone(&self) -> Self { $reverse_iterator(self.0.clone()) } } #[stable(feature = "fused", since = "1.26.0")] impl<'a, P: Pattern<'a>> FusedIterator for $forward_iterator<'a, P> {} #[stable(feature = "fused", since = "1.26.0")] impl<'a, P: Pattern<'a>> FusedIterator for $reverse_iterator<'a, P> where P::Searcher: ReverseSearcher<'a> {} generate_pattern_iterators!($($t)* with $(#[$common_stability_attribute])*, $forward_iterator, $reverse_iterator, $iterty); }; { double ended; with $(#[$common_stability_attribute:meta])*, $forward_iterator:ident, $reverse_iterator:ident, $iterty:ty } => { $(#[$common_stability_attribute])* impl<'a, P: Pattern<'a>> DoubleEndedIterator for $forward_iterator<'a, P> where P::Searcher: DoubleEndedSearcher<'a> { #[inline] fn next_back(&mut self) -> Option<$iterty> { self.0.next_back() } } $(#[$common_stability_attribute])* impl<'a, P: Pattern<'a>> DoubleEndedIterator for $reverse_iterator<'a, P> where P::Searcher: DoubleEndedSearcher<'a> { #[inline] fn next_back(&mut self) -> Option<$iterty> { self.0.next() } } }; { single ended; with $(#[$common_stability_attribute:meta])*, $forward_iterator:ident, $reverse_iterator:ident, $iterty:ty } => {} } derive_pattern_clone!{ clone SplitInternal with |s| SplitInternal { matcher: s.matcher.clone(), ..*s } } struct SplitInternal<'a, P: Pattern<'a>> { start: usize, end: usize, matcher: P::Searcher, allow_trailing_empty: bool, finished: bool, } impl<'a, P: Pattern<'a>> fmt::Debug for SplitInternal<'a, P> where P::Searcher: fmt::Debug { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.debug_struct("SplitInternal") .field("start", &self.start) .field("end", &self.end) .field("matcher", &self.matcher) .field("allow_trailing_empty", &self.allow_trailing_empty) .field("finished", &self.finished) .finish() } } impl<'a, P: Pattern<'a>> SplitInternal<'a, P> { #[inline] fn get_end(&mut self) -> Option<&'a str> { if !self.finished && (self.allow_trailing_empty || self.end - self.start > 0) { self.finished = true; unsafe { let string = self.matcher.haystack().get_unchecked(self.start..self.end); Some(string) } } else { None } } #[inline] fn next(&mut self) -> Option<&'a str> { if self.finished { return None } let haystack = self.matcher.haystack(); match self.matcher.next_match() { Some((a, b)) => unsafe { let elt = haystack.get_unchecked(self.start..a); self.start = b; Some(elt) }, None => self.get_end(), } } #[inline] fn next_back(&mut self) -> Option<&'a str> where P::Searcher: ReverseSearcher<'a> { if self.finished { return None } if !self.allow_trailing_empty { self.allow_trailing_empty = true; match self.next_back() { Some(elt) if !elt.is_empty() => return Some(elt), _ => if self.finished { return None } } } let haystack = self.matcher.haystack(); match self.matcher.next_match_back() { Some((a, b)) => unsafe { let elt = haystack.get_unchecked(b..self.end); self.end = a; Some(elt) }, None => unsafe { self.finished = true; Some(haystack.get_unchecked(self.start..self.end)) }, } } } generate_pattern_iterators! { forward: /// Created with the method [`split`]. /// /// [`split`]: ../../std/primitive.str.html#method.split struct Split; reverse: /// Created with the method [`rsplit`]. /// /// [`rsplit`]: ../../std/primitive.str.html#method.rsplit struct RSplit; stability: #[stable(feature = "rust1", since = "1.0.0")] internal: SplitInternal yielding (&'a str); delegate double ended; } generate_pattern_iterators! { forward: /// Created with the method [`split_terminator`]. /// /// [`split_terminator`]: ../../std/primitive.str.html#method.split_terminator struct SplitTerminator; reverse: /// Created with the method [`rsplit_terminator`]. /// /// [`rsplit_terminator`]: ../../std/primitive.str.html#method.rsplit_terminator struct RSplitTerminator; stability: #[stable(feature = "rust1", since = "1.0.0")] internal: SplitInternal yielding (&'a str); delegate double ended; } derive_pattern_clone!{ clone SplitNInternal with |s| SplitNInternal { iter: s.iter.clone(), ..*s } } struct SplitNInternal<'a, P: Pattern<'a>> { iter: SplitInternal<'a, P>, /// The number of splits remaining count: usize, } impl<'a, P: Pattern<'a>> fmt::Debug for SplitNInternal<'a, P> where P::Searcher: fmt::Debug { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.debug_struct("SplitNInternal") .field("iter", &self.iter) .field("count", &self.count) .finish() } } impl<'a, P: Pattern<'a>> SplitNInternal<'a, P> { #[inline] fn next(&mut self) -> Option<&'a str> { match self.count { 0 => None, 1 => { self.count = 0; self.iter.get_end() } _ => { self.count -= 1; self.iter.next() } } } #[inline] fn next_back(&mut self) -> Option<&'a str> where P::Searcher: ReverseSearcher<'a> { match self.count { 0 => None, 1 => { self.count = 0; self.iter.get_end() } _ => { self.count -= 1; self.iter.next_back() } } } } generate_pattern_iterators! { forward: /// Created with the method [`splitn`]. /// /// [`splitn`]: ../../std/primitive.str.html#method.splitn struct SplitN; reverse: /// Created with the method [`rsplitn`]. /// /// [`rsplitn`]: ../../std/primitive.str.html#method.rsplitn struct RSplitN; stability: #[stable(feature = "rust1", since = "1.0.0")] internal: SplitNInternal yielding (&'a str); delegate single ended; } derive_pattern_clone!{ clone MatchIndicesInternal with |s| MatchIndicesInternal(s.0.clone()) } struct MatchIndicesInternal<'a, P: Pattern<'a>>(P::Searcher); impl<'a, P: Pattern<'a>> fmt::Debug for MatchIndicesInternal<'a, P> where P::Searcher: fmt::Debug { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.debug_tuple("MatchIndicesInternal") .field(&self.0) .finish() } } impl<'a, P: Pattern<'a>> MatchIndicesInternal<'a, P> { #[inline] fn next(&mut self) -> Option<(usize, &'a str)> { self.0.next_match().map(|(start, end)| unsafe { (start, self.0.haystack().get_unchecked(start..end)) }) } #[inline] fn next_back(&mut self) -> Option<(usize, &'a str)> where P::Searcher: ReverseSearcher<'a> { self.0.next_match_back().map(|(start, end)| unsafe { (start, self.0.haystack().get_unchecked(start..end)) }) } } generate_pattern_iterators! { forward: /// Created with the method [`match_indices`]. /// /// [`match_indices`]: ../../std/primitive.str.html#method.match_indices struct MatchIndices; reverse: /// Created with the method [`rmatch_indices`]. /// /// [`rmatch_indices`]: ../../std/primitive.str.html#method.rmatch_indices struct RMatchIndices; stability: #[stable(feature = "str_match_indices", since = "1.5.0")] internal: MatchIndicesInternal yielding ((usize, &'a str)); delegate double ended; } derive_pattern_clone!{ clone MatchesInternal with |s| MatchesInternal(s.0.clone()) } struct MatchesInternal<'a, P: Pattern<'a>>(P::Searcher); impl<'a, P: Pattern<'a>> fmt::Debug for MatchesInternal<'a, P> where P::Searcher: fmt::Debug { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.debug_tuple("MatchesInternal") .field(&self.0) .finish() } } impl<'a, P: Pattern<'a>> MatchesInternal<'a, P> { #[inline] fn next(&mut self) -> Option<&'a str> { self.0.next_match().map(|(a, b)| unsafe { // Indices are known to be on utf8 boundaries self.0.haystack().get_unchecked(a..b) }) } #[inline] fn next_back(&mut self) -> Option<&'a str> where P::Searcher: ReverseSearcher<'a> { self.0.next_match_back().map(|(a, b)| unsafe { // Indices are known to be on utf8 boundaries self.0.haystack().get_unchecked(a..b) }) } } generate_pattern_iterators! { forward: /// Created with the method [`matches`]. /// /// [`matches`]: ../../std/primitive.str.html#method.matches struct Matches; reverse: /// Created with the method [`rmatches`]. /// /// [`rmatches`]: ../../std/primitive.str.html#method.rmatches struct RMatches; stability: #[stable(feature = "str_matches", since = "1.2.0")] internal: MatchesInternal yielding (&'a str); delegate double ended; } /// An iterator over the lines of a string, as string slices. /// /// This struct is created with the [`lines`] method on [`str`]. /// See its documentation for more. /// /// [`lines`]: ../../std/primitive.str.html#method.lines /// [`str`]: ../../std/primitive.str.html #[stable(feature = "rust1", since = "1.0.0")] #[derive(Clone, Debug)] pub struct Lines<'a>(Map<SplitTerminator<'a, char>, LinesAnyMap>); #[stable(feature = "rust1", since = "1.0.0")] impl<'a> Iterator for Lines<'a> { type Item = &'a str; #[inline] fn next(&mut self) -> Option<&'a str> { self.0.next() } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() } } #[stable(feature = "rust1", since = "1.0.0")] impl<'a> DoubleEndedIterator for Lines<'a> { #[inline] fn next_back(&mut self) -> Option<&'a str> { self.0.next_back() } } #[stable(feature = "fused", since = "1.26.0")] impl FusedIterator for Lines<'_> {} /// Created with the method [`lines_any`]. /// /// [`lines_any`]: ../../std/primitive.str.html#method.lines_any #[stable(feature = "rust1", since = "1.0.0")] #[rustc_deprecated(since = "1.4.0", reason = "use lines()/Lines instead now")] #[derive(Clone, Debug)] #[allow(deprecated)] pub struct LinesAny<'a>(Lines<'a>); impl_fn_for_zst! { /// A nameable, cloneable fn type #[derive(Clone)] struct LinesAnyMap impl<'a> Fn = |line: &'a str| -> &'a str { let l = line.len(); if l > 0 && line.as_bytes()[l - 1] == b'\r' { &line[0 .. l - 1] } else { line } }; } #[stable(feature = "rust1", since = "1.0.0")] #[allow(deprecated)] impl<'a> Iterator for LinesAny<'a> { type Item = &'a str; #[inline] fn next(&mut self) -> Option<&'a str> { self.0.next() } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() } } #[stable(feature = "rust1", since = "1.0.0")] #[allow(deprecated)] impl<'a> DoubleEndedIterator for LinesAny<'a> { #[inline] fn next_back(&mut self) -> Option<&'a str> { self.0.next_back() } } #[stable(feature = "fused", since = "1.26.0")] #[allow(deprecated)] impl FusedIterator for LinesAny<'_> {} /* Section: UTF-8 validation */ // use truncation to fit u64 into usize const NONASCII_MASK: usize = 0x80808080_80808080u64 as usize; /// Returns `true` if any byte in the word `x` is nonascii (>= 128). #[inline] fn contains_nonascii(x: usize) -> bool { (x & NONASCII_MASK) != 0 } /// Walks through `v` checking that it's a valid UTF-8 sequence, /// returning `Ok(())` in that case, or, if it is invalid, `Err(err)`. #[inline] fn run_utf8_validation(v: &[u8]) -> Result<(), Utf8Error> { let mut index = 0; let len = v.len(); let usize_bytes = mem::size_of::<usize>(); let ascii_block_size = 2 * usize_bytes; let blocks_end = if len >= ascii_block_size { len - ascii_block_size + 1 } else { 0 }; while index < len { let old_offset = index; macro_rules! err { ($error_len: expr) => { return Err(Utf8Error { valid_up_to: old_offset, error_len: $error_len, }) } } macro_rules! next { () => {{ index += 1; // we needed data, but there was none: error! if index >= len { err!(None) } v[index] }}} let first = v[index]; if first >= 128 { let w = UTF8_CHAR_WIDTH[first as usize]; // 2-byte encoding is for codepoints \u{0080} to \u{07ff} // first C2 80 last DF BF // 3-byte encoding is for codepoints \u{0800} to \u{ffff} // first E0 A0 80 last EF BF BF // excluding surrogates codepoints \u{d800} to \u{dfff} // ED A0 80 to ED BF BF // 4-byte encoding is for codepoints \u{1000}0 to \u{10ff}ff // first F0 90 80 80 last F4 8F BF BF // // Use the UTF-8 syntax from the RFC // // https://tools.ietf.org/html/rfc3629 // UTF8-1 = %x00-7F // UTF8-2 = %xC2-DF UTF8-tail // UTF8-3 = %xE0 %xA0-BF UTF8-tail / %xE1-EC 2( UTF8-tail ) / // %xED %x80-9F UTF8-tail / %xEE-EF 2( UTF8-tail ) // UTF8-4 = %xF0 %x90-BF 2( UTF8-tail ) / %xF1-F3 3( UTF8-tail ) / // %xF4 %x80-8F 2( UTF8-tail ) match w { 2 => if next!() & !CONT_MASK != TAG_CONT_U8 { err!(Some(1)) }, 3 => { match (first, next!()) { (0xE0 , 0xA0 ..= 0xBF) | (0xE1 ..= 0xEC, 0x80 ..= 0xBF) | (0xED , 0x80 ..= 0x9F) | (0xEE ..= 0xEF, 0x80 ..= 0xBF) => {} _ => err!(Some(1)) } if next!() & !CONT_MASK != TAG_CONT_U8 { err!(Some(2)) } } 4 => { match (first, next!()) { (0xF0 , 0x90 ..= 0xBF) | (0xF1 ..= 0xF3, 0x80 ..= 0xBF) | (0xF4 , 0x80 ..= 0x8F) => {} _ => err!(Some(1)) } if next!() & !CONT_MASK != TAG_CONT_U8 { err!(Some(2)) } if next!() & !CONT_MASK != TAG_CONT_U8 { err!(Some(3)) } } _ => err!(Some(1)) } index += 1; } else { // Ascii case, try to skip forward quickly. // When the pointer is aligned, read 2 words of data per iteration // until we find a word containing a non-ascii byte. let ptr = v.as_ptr(); let align = unsafe { // the offset is safe, because `index` is guaranteed inbounds ptr.add(index).align_offset(usize_bytes) }; if align == 0 { while index < blocks_end { unsafe { let block = ptr.add(index) as *const usize; // break if there is a nonascii byte let zu = contains_nonascii(*block); let zv = contains_nonascii(*block.offset(1)); if zu | zv { break; } } index += ascii_block_size; } // step from the point where the wordwise loop stopped while index < len && v[index] < 128 { index += 1; } } else { index += 1; } } } Ok(()) } // https://tools.ietf.org/html/rfc3629 static UTF8_CHAR_WIDTH: [u8; 256] = [ 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // 0x1F 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // 0x3F 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // 0x5F 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // 0x7F 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 0x9F 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 0xBF 0,0,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, // 0xDF 3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3, // 0xEF 4,4,4,4,4,0,0,0,0,0,0,0,0,0,0,0, // 0xFF ]; /// Given a first byte, determines how many bytes are in this UTF-8 character. #[unstable(feature = "str_internals", issue = "0")] #[inline] pub fn utf8_char_width(b: u8) -> usize { UTF8_CHAR_WIDTH[b as usize] as usize } /// Mask of the value bits of a continuation byte. const CONT_MASK: u8 = 0b0011_1111; /// Value of the tag bits (tag mask is !CONT_MASK) of a continuation byte. const TAG_CONT_U8: u8 = 0b1000_0000; /* Section: Trait implementations */ mod traits { use crate::cmp::Ordering; use crate::ops; use crate::slice::{self, SliceIndex}; /// Implements ordering of strings. /// /// Strings are ordered lexicographically by their byte values. This orders Unicode code /// points based on their positions in the code charts. This is not necessarily the same as /// "alphabetical" order, which varies by language and locale. Sorting strings according to /// culturally-accepted standards requires locale-specific data that is outside the scope of /// the `str` type. #[stable(feature = "rust1", since = "1.0.0")] impl Ord for str { #[inline] fn cmp(&self, other: &str) -> Ordering { self.as_bytes().cmp(other.as_bytes()) } } #[stable(feature = "rust1", since = "1.0.0")] impl PartialEq for str { #[inline] fn eq(&self, other: &str) -> bool { self.as_bytes() == other.as_bytes() } #[inline] fn ne(&self, other: &str) -> bool { !(*self).eq(other) } } #[stable(feature = "rust1", since = "1.0.0")] impl Eq for str {} /// Implements comparison operations on strings. /// /// Strings are compared lexicographically by their byte values. This compares Unicode code /// points based on their positions in the code charts. This is not necessarily the same as /// "alphabetical" order, which varies by language and locale. Comparing strings according to /// culturally-accepted standards requires locale-specific data that is outside the scope of /// the `str` type. #[stable(feature = "rust1", since = "1.0.0")] impl PartialOrd for str { #[inline] fn partial_cmp(&self, other: &str) -> Option<Ordering> { Some(self.cmp(other)) } } #[stable(feature = "rust1", since = "1.0.0")] impl<I> ops::Index<I> for str where I: SliceIndex<str>, { type Output = I::Output; #[inline] fn index(&self, index: I) -> &I::Output { index.index(self) } } #[stable(feature = "rust1", since = "1.0.0")] impl<I> ops::IndexMut<I> for str where I: SliceIndex<str>, { #[inline] fn index_mut(&mut self, index: I) -> &mut I::Output { index.index_mut(self) } } #[inline(never)] #[cold] fn str_index_overflow_fail() -> ! { panic!("attempted to index str up to maximum usize"); } /// Implements substring slicing with syntax `&self[..]` or `&mut self[..]`. /// /// Returns a slice of the whole string, i.e., returns `&self` or `&mut /// self`. Equivalent to `&self[0 .. len]` or `&mut self[0 .. len]`. Unlike /// other indexing operations, this can never panic. /// /// This operation is `O(1)`. /// /// Prior to 1.20.0, these indexing operations were still supported by /// direct implementation of `Index` and `IndexMut`. /// /// Equivalent to `&self[0 .. len]` or `&mut self[0 .. len]`. #[stable(feature = "str_checked_slicing", since = "1.20.0")] impl SliceIndex<str> for ops::RangeFull { type Output = str; #[inline] fn get(self, slice: &str) -> Option<&Self::Output> { Some(slice) } #[inline] fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { Some(slice) } #[inline] unsafe fn get_unchecked(self, slice: &str) -> &Self::Output { slice } #[inline] unsafe fn get_unchecked_mut(self, slice: &mut str) -> &mut Self::Output { slice } #[inline] fn index(self, slice: &str) -> &Self::Output { slice } #[inline] fn index_mut(self, slice: &mut str) -> &mut Self::Output { slice } } /// Implements substring slicing with syntax `&self[begin .. end]` or `&mut /// self[begin .. end]`. /// /// Returns a slice of the given string from the byte range /// [`begin`, `end`). /// /// This operation is `O(1)`. /// /// Prior to 1.20.0, these indexing operations were still supported by /// direct implementation of `Index` and `IndexMut`. /// /// # Panics /// /// Panics if `begin` or `end` does not point to the starting byte offset of /// a character (as defined by `is_char_boundary`), if `begin > end`, or if /// `end > len`. /// /// # Examples /// /// ``` /// let s = "Löwe 老虎 Léopard"; /// assert_eq!(&s[0 .. 1], "L"); /// /// assert_eq!(&s[1 .. 9], "öwe 老"); /// /// // these will panic: /// // byte 2 lies within `ö`: /// // &s[2 ..3]; /// /// // byte 8 lies within `老` /// // &s[1 .. 8]; /// /// // byte 100 is outside the string /// // &s[3 .. 100]; /// ``` #[stable(feature = "str_checked_slicing", since = "1.20.0")] impl SliceIndex<str> for ops::Range<usize> { type Output = str; #[inline] fn get(self, slice: &str) -> Option<&Self::Output> { if self.start <= self.end && slice.is_char_boundary(self.start) && slice.is_char_boundary(self.end) { Some(unsafe { self.get_unchecked(slice) }) } else { None } } #[inline] fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { if self.start <= self.end && slice.is_char_boundary(self.start) && slice.is_char_boundary(self.end) { Some(unsafe { self.get_unchecked_mut(slice) }) } else { None } } #[inline] unsafe fn get_unchecked(self, slice: &str) -> &Self::Output { let ptr = slice.as_ptr().add(self.start); let len = self.end - self.start; super::from_utf8_unchecked(slice::from_raw_parts(ptr, len)) } #[inline] unsafe fn get_unchecked_mut(self, slice: &mut str) -> &mut Self::Output { let ptr = slice.as_mut_ptr().add(self.start); let len = self.end - self.start; super::from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr, len)) } #[inline] fn index(self, slice: &str) -> &Self::Output { let (start, end) = (self.start, self.end); self.get(slice).unwrap_or_else(|| super::slice_error_fail(slice, start, end)) } #[inline] fn index_mut(self, slice: &mut str) -> &mut Self::Output { // is_char_boundary checks that the index is in [0, .len()] // cannot reuse `get` as above, because of NLL trouble if self.start <= self.end && slice.is_char_boundary(self.start) && slice.is_char_boundary(self.end) { unsafe { self.get_unchecked_mut(slice) } } else { super::slice_error_fail(slice, self.start, self.end) } } } /// Implements substring slicing with syntax `&self[.. end]` or `&mut /// self[.. end]`. /// /// Returns a slice of the given string from the byte range [`0`, `end`). /// Equivalent to `&self[0 .. end]` or `&mut self[0 .. end]`. /// /// This operation is `O(1)`. /// /// Prior to 1.20.0, these indexing operations were still supported by /// direct implementation of `Index` and `IndexMut`. /// /// # Panics /// /// Panics if `end` does not point to the starting byte offset of a /// character (as defined by `is_char_boundary`), or if `end > len`. #[stable(feature = "str_checked_slicing", since = "1.20.0")] impl SliceIndex<str> for ops::RangeTo<usize> { type Output = str; #[inline] fn get(self, slice: &str) -> Option<&Self::Output> { if slice.is_char_boundary(self.end) { Some(unsafe { self.get_unchecked(slice) }) } else { None } } #[inline] fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { if slice.is_char_boundary(self.end) { Some(unsafe { self.get_unchecked_mut(slice) }) } else { None } } #[inline] unsafe fn get_unchecked(self, slice: &str) -> &Self::Output { let ptr = slice.as_ptr(); super::from_utf8_unchecked(slice::from_raw_parts(ptr, self.end)) } #[inline] unsafe fn get_unchecked_mut(self, slice: &mut str) -> &mut Self::Output { let ptr = slice.as_mut_ptr(); super::from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr, self.end)) } #[inline] fn index(self, slice: &str) -> &Self::Output { let end = self.end; self.get(slice).unwrap_or_else(|| super::slice_error_fail(slice, 0, end)) } #[inline] fn index_mut(self, slice: &mut str) -> &mut Self::Output { // is_char_boundary checks that the index is in [0, .len()] if slice.is_char_boundary(self.end) { unsafe { self.get_unchecked_mut(slice) } } else { super::slice_error_fail(slice, 0, self.end) } } } /// Implements substring slicing with syntax `&self[begin ..]` or `&mut /// self[begin ..]`. /// /// Returns a slice of the given string from the byte range [`begin`, /// `len`). Equivalent to `&self[begin .. len]` or `&mut self[begin .. /// len]`. /// /// This operation is `O(1)`. /// /// Prior to 1.20.0, these indexing operations were still supported by /// direct implementation of `Index` and `IndexMut`. /// /// # Panics /// /// Panics if `begin` does not point to the starting byte offset of /// a character (as defined by `is_char_boundary`), or if `begin >= len`. #[stable(feature = "str_checked_slicing", since = "1.20.0")] impl SliceIndex<str> for ops::RangeFrom<usize> { type Output = str; #[inline] fn get(self, slice: &str) -> Option<&Self::Output> { if slice.is_char_boundary(self.start) { Some(unsafe { self.get_unchecked(slice) }) } else { None } } #[inline] fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { if slice.is_char_boundary(self.start) { Some(unsafe { self.get_unchecked_mut(slice) }) } else { None } } #[inline] unsafe fn get_unchecked(self, slice: &str) -> &Self::Output { let ptr = slice.as_ptr().add(self.start); let len = slice.len() - self.start; super::from_utf8_unchecked(slice::from_raw_parts(ptr, len)) } #[inline] unsafe fn get_unchecked_mut(self, slice: &mut str) -> &mut Self::Output { let ptr = slice.as_mut_ptr().add(self.start); let len = slice.len() - self.start; super::from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr, len)) } #[inline] fn index(self, slice: &str) -> &Self::Output { let (start, end) = (self.start, slice.len()); self.get(slice).unwrap_or_else(|| super::slice_error_fail(slice, start, end)) } #[inline] fn index_mut(self, slice: &mut str) -> &mut Self::Output { // is_char_boundary checks that the index is in [0, .len()] if slice.is_char_boundary(self.start) { unsafe { self.get_unchecked_mut(slice) } } else { super::slice_error_fail(slice, self.start, slice.len()) } } } /// Implements substring slicing with syntax `&self[begin ..= end]` or `&mut /// self[begin ..= end]`. /// /// Returns a slice of the given string from the byte range /// [`begin`, `end`]. Equivalent to `&self [begin .. end + 1]` or `&mut /// self[begin .. end + 1]`, except if `end` has the maximum value for /// `usize`. /// /// This operation is `O(1)`. /// /// # Panics /// /// Panics if `begin` does not point to the starting byte offset of /// a character (as defined by `is_char_boundary`), if `end` does not point /// to the ending byte offset of a character (`end + 1` is either a starting /// byte offset or equal to `len`), if `begin > end`, or if `end >= len`. #[stable(feature = "inclusive_range", since = "1.26.0")] impl SliceIndex<str> for ops::RangeInclusive<usize> { type Output = str; #[inline] fn get(self, slice: &str) -> Option<&Self::Output> { if *self.end() == usize::max_value() { None } else { (*self.start()..self.end()+1).get(slice) } } #[inline] fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { if *self.end() == usize::max_value() { None } else { (*self.start()..self.end()+1).get_mut(slice) } } #[inline] unsafe fn get_unchecked(self, slice: &str) -> &Self::Output { (*self.start()..self.end()+1).get_unchecked(slice) } #[inline] unsafe fn get_unchecked_mut(self, slice: &mut str) -> &mut Self::Output { (*self.start()..self.end()+1).get_unchecked_mut(slice) } #[inline] fn index(self, slice: &str) -> &Self::Output { if *self.end() == usize::max_value() { str_index_overflow_fail(); } (*self.start()..self.end()+1).index(slice) } #[inline] fn index_mut(self, slice: &mut str) -> &mut Self::Output { if *self.end() == usize::max_value() { str_index_overflow_fail(); } (*self.start()..self.end()+1).index_mut(slice) } } /// Implements substring slicing with syntax `&self[..= end]` or `&mut /// self[..= end]`. /// /// Returns a slice of the given string from the byte range [0, `end`]. /// Equivalent to `&self [0 .. end + 1]`, except if `end` has the maximum /// value for `usize`. /// /// This operation is `O(1)`. /// /// # Panics /// /// Panics if `end` does not point to the ending byte offset of a character /// (`end + 1` is either a starting byte offset as defined by /// `is_char_boundary`, or equal to `len`), or if `end >= len`. #[stable(feature = "inclusive_range", since = "1.26.0")] impl SliceIndex<str> for ops::RangeToInclusive<usize> { type Output = str; #[inline] fn get(self, slice: &str) -> Option<&Self::Output> { if self.end == usize::max_value() { None } else { (..self.end+1).get(slice) } } #[inline] fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { if self.end == usize::max_value() { None } else { (..self.end+1).get_mut(slice) } } #[inline] unsafe fn get_unchecked(self, slice: &str) -> &Self::Output { (..self.end+1).get_unchecked(slice) } #[inline] unsafe fn get_unchecked_mut(self, slice: &mut str) -> &mut Self::Output { (..self.end+1).get_unchecked_mut(slice) } #[inline] fn index(self, slice: &str) -> &Self::Output { if self.end == usize::max_value() { str_index_overflow_fail(); } (..self.end+1).index(slice) } #[inline] fn index_mut(self, slice: &mut str) -> &mut Self::Output { if self.end == usize::max_value() { str_index_overflow_fail(); } (..self.end+1).index_mut(slice) } } } // truncate `&str` to length at most equal to `max` // return `true` if it were truncated, and the new str. fn truncate_to_char_boundary(s: &str, mut max: usize) -> (bool, &str) { if max >= s.len() { (false, s) } else { while !s.is_char_boundary(max) { max -= 1; } (true, &s[..max]) } } #[inline(never)] #[cold] fn slice_error_fail(s: &str, begin: usize, end: usize) -> ! { const MAX_DISPLAY_LENGTH: usize = 256; let (truncated, s_trunc) = truncate_to_char_boundary(s, MAX_DISPLAY_LENGTH); let ellipsis = if truncated { "[...]" } 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 {} is out of bounds of `{}`{}", oob_index, 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 mut char_start = index; while !s.is_char_boundary(char_start) { char_start -= 1; } // `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); } #[lang = "str"] #[cfg(not(test))] impl str { /// Returns the length of `self`. /// /// This length is in bytes, not [`char`]s or graphemes. In other words, /// it may not be what a human considers the length of the string. /// /// # Examples /// /// Basic usage: /// /// ``` /// let len = "foo".len(); /// assert_eq!(3, len); /// /// let len = "ƒoo".len(); // fancy f! /// assert_eq!(4, len); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] #[rustc_const_unstable(feature = "const_str_len")] pub const fn len(&self) -> usize { self.as_bytes().len() } /// Returns `true` if `self` has a length of zero bytes. /// /// # Examples /// /// Basic usage: /// /// ``` /// let s = ""; /// assert!(s.is_empty()); /// /// let s = "not empty"; /// assert!(!s.is_empty()); /// ``` #[inline] #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_unstable(feature = "const_str_len")] pub const fn is_empty(&self) -> bool { self.len() == 0 } /// Checks that `index`-th byte lies at the start and/or end of a /// UTF-8 code point sequence. /// /// 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)); /// ``` #[stable(feature = "is_char_boundary", since = "1.9.0")] #[inline] pub fn is_char_boundary(&self, index: usize) -> bool { // 0 and len are always ok. // Test for 0 explicitly so that it can optimize out the check // easily and skip reading string data for that case. if index == 0 || index == self.len() { return true; } match self.as_bytes().get(index) { None => false, // This is bit magic equivalent to: b < 128 || b >= 192 Some(&b) => (b as i8) >= -0x40, } } /// Converts a string slice to a byte slice. To convert the byte slice back /// into a string slice, use the [`str::from_utf8`] function. /// /// [`str::from_utf8`]: ./str/fn.from_utf8.html /// /// # Examples /// /// Basic usage: /// /// ``` /// let bytes = "bors".as_bytes(); /// assert_eq!(b"bors", bytes); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline(always)] #[rustc_const_unstable(feature="const_str_as_bytes")] pub const fn as_bytes(&self) -> &[u8] { union Slices<'a> { str: &'a str, slice: &'a [u8], } unsafe { Slices { str: self }.slice } } /// Converts a mutable string slice to a mutable byte slice. To convert the /// mutable byte slice back into a mutable string slice, use the /// [`str::from_utf8_mut`] function. /// /// [`str::from_utf8_mut`]: ./str/fn.from_utf8_mut.html /// /// # 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")] #[inline(always)] pub unsafe fn as_bytes_mut(&mut self) -> &mut [u8] { &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`]. /// /// [`u8`]: primitive.u8.html /// [`as_mut_ptr`]: #method.as_mut_ptr /// /// # Examples /// /// Basic usage: /// /// ``` /// let s = "Hello"; /// let ptr = s.as_ptr(); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] 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. /// /// [`u8`]: primitive.u8.html #[stable(feature = "str_as_mut_ptr", since = "1.36.0")] #[inline] pub 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. /// /// [`None`]: option/enum.Option.html#variant.None /// /// # 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")] #[inline] pub fn get<I: 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. /// /// [`None`]: option/enum.Option.html#variant.None /// /// # 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")] #[inline] pub fn get_mut<I: SliceIndex<str>>(&mut self, i: I) -> Option<&mut I::Output> { i.get_mut(self) } /// Returns a 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 come before 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 { 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 come before 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 { 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`]. /// /// [`str`]: primitive.str.html /// [`Index`]: ops/trait.Index.html /// /// 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`]: #method.slice_mut_unchecked /// /// # Safety /// /// Callers of this function are responsible that three preconditions are /// satisfied: /// /// * `begin` must come before `end`. /// * `begin` and `end` must be byte positions within the string slice. /// * `begin` and `end` must lie on UTF-8 sequence boundaries. /// /// # Examples /// /// Basic usage: /// /// ``` /// 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")] #[rustc_deprecated(since = "1.29.0", reason = "use `get_unchecked(begin..end)` instead")] #[inline] pub unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str { (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`]. /// /// [`str`]: primitive.str.html /// [`IndexMut`]: ops/trait.IndexMut.html /// /// 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`]: #method.slice_unchecked /// /// # Safety /// /// Callers of this function are responsible that three preconditions are /// satisfied: /// /// * `begin` must come before `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")] #[rustc_deprecated(since = "1.29.0", reason = "use `get_unchecked_mut(begin..end)` instead")] #[inline] pub unsafe fn slice_mut_unchecked(&mut self, begin: usize, end: usize) -> &mut str { (begin..end).get_unchecked_mut(self) } /// Divide 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`]: #method.split_at_mut /// /// # Panics /// /// Panics if `mid` is not on a UTF-8 code point boundary, or if it is /// beyond the last code point of the string slice. /// /// # Examples /// /// Basic usage: /// /// ``` /// let s = "Per Martin-Löf"; /// /// let (first, last) = s.split_at(3); /// /// assert_eq!("Per", first); /// assert_eq!(" Martin-Löf", last); /// ``` #[inline] #[stable(feature = "str_split_at", since = "1.4.0")] pub fn split_at(&self, mid: usize) -> (&str, &str) { // is_char_boundary checks that the index is in [0, .len()] if self.is_char_boundary(mid) { unsafe { (self.get_unchecked(0..mid), self.get_unchecked(mid..self.len())) } } else { slice_error_fail(self, 0, mid) } } /// Divide 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`]: #method.split_at /// /// # Panics /// /// Panics if `mid` is not on a UTF-8 code point boundary, or if it is /// beyond the last code point of the string slice. /// /// # Examples /// /// Basic usage: /// /// ``` /// 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] #[stable(feature = "str_split_at", since = "1.4.0")] pub 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) { let len = self.len(); let ptr = self.as_mut_ptr(); 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 ))) } } else { slice_error_fail(self, 0, 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 may not match your idea of what a 'character' is. Iteration /// over grapheme clusters may be what you actually want. /// /// # 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 may not match your human intuition about characters: /// /// ``` /// 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] 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 may not match your human intuition about characters: /// /// ``` /// 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 last 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() } } /// 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 /// /// Basic usage: /// /// ``` /// 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().cloned()) } /// 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`]: #method.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()); /// ``` #[stable(feature = "split_whitespace", since = "1.1.0")] #[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. /// /// To split by Unicode `Whitespace` instead, use [`split_whitespace`]. /// /// [`split_whitespace`]: #method.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()); /// ``` /// /// All kinds of ASCII whitespace are considered: /// /// ``` /// 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()); /// ``` #[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 } } /// An iterator over the lines of a string, as string slices. /// /// Lines are ended with either a newline (`\n`) or a carriage return with /// a line feed (`\r\n`). /// /// The final line ending is optional. /// /// # Examples /// /// Basic usage: /// /// ``` /// let text = "foo\r\nbar\n\nbaz\n"; /// 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()); /// ``` /// /// The final line ending isn't required: /// /// ``` /// 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_terminator('\n').map(LinesAnyMap)) } /// An iterator over the lines of a string. #[stable(feature = "rust1", since = "1.0.0")] #[rustc_deprecated(since = "1.4.0", reason = "use lines() instead now")] #[inline] #[allow(deprecated)] pub fn lines_any(&self) -> LinesAny<'_> { LinesAny(self.lines()) } /// Returns an iterator of `u16` over the string encoded as UTF-16. /// /// # Examples /// /// Basic usage: /// /// ``` /// let text = "Zażółć gęślą jaźń"; /// /// let utf8_len = text.len(); /// let utf16_len = text.encode_utf16().count(); /// /// assert!(utf16_len <= utf8_len); /// ``` #[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. /// /// # Examples /// /// Basic usage: /// /// ``` /// let bananas = "bananas"; /// /// assert!(bananas.contains("nana")); /// assert!(!bananas.contains("apples")); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn contains<'a, P: Pattern<'a>>(&'a 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. /// /// # Examples /// /// Basic usage: /// /// ``` /// let bananas = "bananas"; /// /// assert!(bananas.starts_with("bana")); /// assert!(!bananas.starts_with("nana")); /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn starts_with<'a, P: Pattern<'a>>(&'a 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. /// /// # Examples /// /// Basic usage: /// /// ``` /// let bananas = "bananas"; /// /// assert!(bananas.ends_with("anas")); /// assert!(!bananas.ends_with("nana")); /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn ends_with<'a, P: Pattern<'a>>(&'a self, pat: P) -> bool where P::Searcher: 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`], or a closure that determines if /// a character matches. /// /// [`None`]: option/enum.Option.html#variant.None /// /// # Examples /// /// Simple patterns: /// /// ``` /// let s = "Löwe 老虎 Léopard"; /// /// assert_eq!(s.find('L'), Some(0)); /// assert_eq!(s.find('é'), Some(14)); /// assert_eq!(s.find("Léopard"), Some(13)); /// ``` /// /// 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<'a, P: Pattern<'a>>(&'a self, pat: P) -> Option<usize> { pat.into_searcher(self).next_match().map(|(i, _)| i) } /// Returns the byte index of the last character of this string slice that /// matches the pattern. /// /// Returns [`None`] if the pattern doesn't match. /// /// The pattern can be a `&str`, [`char`], or a closure that determines if /// a character matches. /// /// [`None`]: option/enum.Option.html#variant.None /// /// # Examples /// /// Simple patterns: /// /// ``` /// let s = "Löwe 老虎 Léopard"; /// /// assert_eq!(s.rfind('L'), Some(13)); /// assert_eq!(s.rfind('é'), Some(14)); /// ``` /// /// 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<'a, P: Pattern<'a>>(&'a self, pat: P) -> Option<usize> where P::Searcher: ReverseSearcher<'a> { pat.into_searcher(self).next_match_back().map(|(i, _)| i) } /// An iterator over substrings of this string slice, separated by /// characters matched by a pattern. /// /// The pattern can be any type that implements the Pattern trait. Notable /// examples are `&str`, [`char`], and closures that determines the split. /// /// # 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`. /// /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html /// /// If the pattern allows a reverse search but its results might differ /// from a forward search, the [`rsplit`] method can be used. /// /// [`rsplit`]: #method.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> = "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"]); /// ``` /// /// 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`]: #method.split_whitespace #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn split<'a, P: Pattern<'a>>(&'a self, pat: P) -> Split<'a, P> { Split(SplitInternal { start: 0, end: self.len(), matcher: pat.into_searcher(self), allow_trailing_empty: true, finished: false, }) } /// 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 any type that implements the Pattern trait. Notable /// examples are `&str`, [`char`], and closures that determines the split. /// /// # 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. /// /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html /// /// For iterating from the front, the [`split`] method can be used. /// /// [`split`]: #method.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<'a, P: Pattern<'a>>(&'a self, pat: P) -> RSplit<'a, P> where P::Searcher: ReverseSearcher<'a> { RSplit(self.split(pat).0) } /// An iterator over substrings of the given string slice, separated by /// characters matched by a pattern. /// /// The pattern can be any type that implements the Pattern trait. Notable /// examples are `&str`, [`char`], and closures that determines the split. /// /// Equivalent to [`split`], except that the trailing substring /// is skipped if empty. /// /// [`split`]: #method.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`. /// /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html /// /// 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`]: #method.rsplit_terminator /// /// # Examples /// /// Basic usage: /// /// ``` /// 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", ""]); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn split_terminator<'a, P: Pattern<'a>>(&'a self, pat: P) -> SplitTerminator<'a, P> { SplitTerminator(SplitInternal { allow_trailing_empty: false, ..self.split(pat).0 }) } /// An iterator over substrings of `self`, separated by characters /// matched by a pattern and yielded in reverse order. /// /// The pattern can be any type that implements the Pattern trait. Notable /// examples are `&str`, [`char`], and closures that determines the split. /// Additional libraries might provide more complex patterns like /// regular expressions. /// /// Equivalent to [`split`], except that the trailing substring is /// skipped if empty. /// /// [`split`]: #method.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`]: #method.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"]); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn rsplit_terminator<'a, P: Pattern<'a>>(&'a self, pat: P) -> RSplitTerminator<'a, P> where P::Searcher: ReverseSearcher<'a> { RSplitTerminator(self.split_terminator(pat).0) } /// 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 any type that implements the Pattern trait. Notable /// examples are `&str`, [`char`], and closures that determines the split. /// /// # 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`]: #method.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<'a, P: Pattern<'a>>(&'a self, n: usize, pat: P) -> SplitN<'a, P> { SplitN(SplitNInternal { iter: self.split(pat).0, count: n, }) } /// 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 any type that implements the Pattern trait. Notable /// examples are `&str`, [`char`], and closures that determines the split. /// /// # 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`]: #method.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<'a, P: Pattern<'a>>(&'a self, n: usize, pat: P) -> RSplitN<'a, P> where P::Searcher: ReverseSearcher<'a> { RSplitN(self.splitn(n, pat).0) } /// An iterator over the disjoint matches of a pattern within the given string /// slice. /// /// The pattern can be any type that implements the Pattern trait. Notable /// examples are `&str`, [`char`], and closures that determines the split. /// /// # 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`. /// /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html /// /// If the pattern allows a reverse search but its results might differ /// from a forward search, the [`rmatches`] method can be used. /// /// [`rmatches`]: #method.rmatches /// /// # Examples /// /// Basic usage: /// /// ``` /// 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<'a, P: Pattern<'a>>(&'a self, pat: P) -> Matches<'a, P> { Matches(MatchesInternal(pat.into_searcher(self))) } /// An iterator over the disjoint matches of a pattern within this string slice, /// yielded in reverse order. /// /// The pattern can be a `&str`, [`char`], or a closure that determines if /// a character matches. /// /// # 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. /// /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html /// /// For iterating from the front, the [`matches`] method can be used. /// /// [`matches`]: #method.matches /// /// # Examples /// /// Basic usage: /// /// ``` /// 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<'a, P: Pattern<'a>>(&'a self, pat: P) -> RMatches<'a, P> where P::Searcher: ReverseSearcher<'a> { RMatches(self.matches(pat).0) } /// 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`], or a closure that determines /// if a character matches. /// /// # 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`. /// /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html /// /// 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`]: #method.rmatch_indices /// /// # Examples /// /// Basic usage: /// /// ``` /// 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<'a, P: Pattern<'a>>(&'a self, pat: P) -> MatchIndices<'a, P> { MatchIndices(MatchIndicesInternal(pat.into_searcher(self))) } /// 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`], or a closure that determines if a /// character matches. /// /// # 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. /// /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html /// /// For iterating from the front, the [`match_indices`] method can be used. /// /// [`match_indices`]: #method.match_indices /// /// # Examples /// /// Basic usage: /// /// ``` /// 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<'a, P: Pattern<'a>>(&'a self, pat: P) -> RMatchIndices<'a, P> where P::Searcher: 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`. /// /// # Examples /// /// Basic usage: /// /// ``` /// let s = " Hello\tworld\t"; /// /// assert_eq!("Hello\tworld", s.trim()); /// ``` #[must_use = "this returns the trimmed string as a slice, \ without modifying the original"] #[stable(feature = "rust1", since = "1.0.0")] pub fn trim(&self) -> &str { self.trim_matches(|c: char| c.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. `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 /// like Arabic or Hebrew, this will be the right side. /// /// # Examples /// /// Basic usage: /// /// ``` /// let s = " Hello\tworld\t"; /// assert_eq!("Hello\tworld\t", 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()); /// ``` #[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(&self) -> &str { self.trim_start_matches(|c: char| c.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`. /// /// # 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 /// like Arabic or Hebrew, this will be the left side. /// /// # Examples /// /// Basic usage: /// /// ``` /// let s = " Hello\tworld\t"; /// assert_eq!(" 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()); /// ``` #[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(&self) -> &str { self.trim_end_matches(|c: char| c.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()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[rustc_deprecated( since = "1.33.0", reason = "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()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[rustc_deprecated( since = "1.33.0", reason = "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`] or a closure that determines if a /// character matches. /// /// # 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<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a str where P::Searcher: 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; } unsafe { // Searcher is known to return valid indices 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`], or a closure that determines if /// a character matches. /// /// # 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: /// /// ``` /// 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<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a str { let mut i = self.len(); let mut matcher = pat.into_searcher(self); if let Some((a, _)) = matcher.next_reject() { i = a; } unsafe { // Searcher is known to return valid indices self.get_unchecked(i..self.len()) } } /// Returns a string slice with all suffixes that match a pattern /// repeatedly removed. /// /// The pattern can be a `&str`, [`char`], or a closure that /// determines if a character matches. /// /// # 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_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<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a str where P::Searcher: ReverseSearcher<'a> { let mut j = 0; let mut matcher = pat.into_searcher(self); if let Some((_, b)) = matcher.next_reject_back() { j = b; } unsafe { // Searcher is known to return valid indices 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`], or a closure that determines if /// a character matches. /// /// [`char`]: primitive.char.html /// /// # 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 /// like Arabic or Hebrew, this will be the right side. /// /// # Examples /// /// Basic usage: /// /// ``` /// 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")] #[rustc_deprecated( since = "1.33.0", reason = "superseded by `trim_start_matches`", suggestion = "trim_start_matches", )] pub fn trim_left_matches<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a 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`], or a closure that /// determines if a character matches. /// /// [`char`]: primitive.char.html /// /// # 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 /// like Arabic or Hebrew, this will be the left side. /// /// # 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")] #[rustc_deprecated( since = "1.33.0", reason = "superseded by `trim_end_matches`", suggestion = "trim_end_matches", )] pub fn trim_right_matches<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a str where P::Searcher: 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 any type that implements the [`FromStr`] trait. /// /// [`FromStr`]: str/trait.FromStr.html /// /// # Errors /// /// Will return [`Err`] if it's not possible to parse this string slice into /// the desired type. /// /// [`Err`]: str/trait.FromStr.html#associatedtype.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")] #[inline] pub 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.bytes().all(|b| b.is_ascii()) } /// 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")] #[inline] pub 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 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] pub fn make_ascii_uppercase(&mut self) { 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 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] pub fn make_ascii_lowercase(&mut self) { let me = unsafe { self.as_bytes_mut() }; me.make_ascii_lowercase() } /// Return an iterator that escapes each char in `self` with [`char::escape_debug`]. /// /// Note: only extended grapheme codepoints that begin the string will be /// escaped. /// /// [`char::escape_debug`]: ../std/primitive.char.html#method.escape_debug /// /// # 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!"); /// ``` #[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(true)) .into_iter() .flatten() .chain(chars.flat_map(CharEscapeDebugContinue)) } } /// Return an iterator that escapes each char in `self` with [`char::escape_default`]. /// /// [`char::escape_default`]: ../std/primitive.char.html#method.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!"); /// ``` #[stable(feature = "str_escape", since = "1.34.0")] pub fn escape_default(&self) -> EscapeDefault<'_> { EscapeDefault { inner: self.chars().flat_map(CharEscapeDefault) } } /// Return an iterator that escapes each char in `self` with [`char::escape_unicode`]. /// /// [`char::escape_unicode`]: ../std/primitive.char.html#method.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}"); /// ``` #[stable(feature = "str_escape", since = "1.34.0")] pub fn escape_unicode(&self) -> EscapeUnicode<'_> { EscapeUnicode { inner: self.chars().flat_map(CharEscapeUnicode) } } } impl_fn_for_zst! { #[derive(Clone)] struct CharEscapeDebugContinue impl Fn = |c: char| -> char::EscapeDebug { c.escape_debug_ext(false) }; #[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() }; } #[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")] impl Default for &str { /// Creates an empty str fn default() -> Self { "" } } #[stable(feature = "default_mut_str", since = "1.28.0")] impl Default for &mut str { /// Creates an empty mutable str fn default() -> Self { unsafe { from_utf8_unchecked_mut(&mut []) } } } /// An iterator over the non-whitespace substrings of a string, /// separated by any amount of whitespace. /// /// This struct is created by the [`split_whitespace`] method on [`str`]. /// See its documentation for more. /// /// [`split_whitespace`]: ../../std/primitive.str.html#method.split_whitespace /// [`str`]: ../../std/primitive.str.html #[stable(feature = "split_whitespace", since = "1.1.0")] #[derive(Clone, Debug)] pub struct SplitWhitespace<'a> { inner: Filter<Split<'a, IsWhitespace>, IsNotEmpty>, } /// An iterator over the non-ASCII-whitespace substrings of a string, /// separated by any amount of ASCII whitespace. /// /// This struct is created by the [`split_ascii_whitespace`] method on [`str`]. /// See its documentation for more. /// /// [`split_ascii_whitespace`]: ../../std/primitive.str.html#method.split_ascii_whitespace /// [`str`]: ../../std/primitive.str.html #[stable(feature = "split_ascii_whitespace", since = "1.34.0")] #[derive(Clone, Debug)] pub struct SplitAsciiWhitespace<'a> { inner: Map<Filter<SliceSplit<'a, u8, IsAsciiWhitespace>, BytesIsNotEmpty>, UnsafeBytesToStr>, } impl_fn_for_zst! { #[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 { unsafe { from_utf8_unchecked(bytes) } }; } #[stable(feature = "split_whitespace", since = "1.1.0")] impl<'a> Iterator for SplitWhitespace<'a> { type Item = &'a str; #[inline] fn next(&mut self) -> Option<&'a str> { self.inner.next() } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() } } #[stable(feature = "split_whitespace", since = "1.1.0")] impl<'a> DoubleEndedIterator for SplitWhitespace<'a> { #[inline] fn next_back(&mut self) -> Option<&'a str> { self.inner.next_back() } } #[stable(feature = "fused", since = "1.26.0")] impl FusedIterator for SplitWhitespace<'_> {} #[stable(feature = "split_ascii_whitespace", since = "1.34.0")] impl<'a> Iterator for SplitAsciiWhitespace<'a> { type Item = &'a str; #[inline] fn next(&mut self) -> Option<&'a str> { self.inner.next() } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() } } #[stable(feature = "split_ascii_whitespace", since = "1.34.0")] impl<'a> DoubleEndedIterator for SplitAsciiWhitespace<'a> { #[inline] fn next_back(&mut self) -> Option<&'a str> { self.inner.next_back() } } #[stable(feature = "split_ascii_whitespace", since = "1.34.0")] impl FusedIterator for SplitAsciiWhitespace<'_> {} /// An iterator of [`u16`] over the string encoded as UTF-16. /// /// [`u16`]: ../../std/primitive.u16.html /// /// This struct is created by the [`encode_utf16`] method on [`str`]. /// See its documentation for more. /// /// [`encode_utf16`]: ../../std/primitive.str.html#method.encode_utf16 /// [`str`]: ../../std/primitive.str.html #[derive(Clone)] #[stable(feature = "encode_utf16", since = "1.8.0")] pub struct EncodeUtf16<'a> { chars: Chars<'a>, extra: u16, } #[stable(feature = "collection_debug", since = "1.17.0")] impl fmt::Debug for EncodeUtf16<'_> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.pad("EncodeUtf16 { .. }") } } #[stable(feature = "encode_utf16", since = "1.8.0")] impl<'a> Iterator for EncodeUtf16<'a> { type Item = u16; #[inline] fn next(&mut self) -> Option<u16> { if self.extra != 0 { let tmp = self.extra; self.extra = 0; return Some(tmp); } let mut buf = [0; 2]; self.chars.next().map(|ch| { let n = ch.encode_utf16(&mut buf).len(); if n == 2 { self.extra = buf[1]; } buf[0] }) } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { let (low, high) = self.chars.size_hint(); // every char gets either one u16 or two u16, // so this iterator is between 1 or 2 times as // long as the underlying iterator. (low, high.and_then(|n| n.checked_mul(2))) } } #[stable(feature = "fused", since = "1.26.0")] impl FusedIterator for EncodeUtf16<'_> {} /// The return type of [`str::escape_debug`]. /// /// [`str::escape_debug`]: ../../std/primitive.str.html#method.escape_debug #[stable(feature = "str_escape", since = "1.34.0")] #[derive(Clone, Debug)] pub struct EscapeDebug<'a> { inner: Chain< Flatten<option::IntoIter<char::EscapeDebug>>, FlatMap<Chars<'a>, char::EscapeDebug, CharEscapeDebugContinue> >, } /// The return type of [`str::escape_default`]. /// /// [`str::escape_default`]: ../../std/primitive.str.html#method.escape_default #[stable(feature = "str_escape", since = "1.34.0")] #[derive(Clone, Debug)] pub struct EscapeDefault<'a> { inner: FlatMap<Chars<'a>, char::EscapeDefault, CharEscapeDefault>, } /// The return type of [`str::escape_unicode`]. /// /// [`str::escape_unicode`]: ../../std/primitive.str.html#method.escape_unicode #[stable(feature = "str_escape", since = "1.34.0")] #[derive(Clone, Debug)] pub struct EscapeUnicode<'a> { inner: FlatMap<Chars<'a>, char::EscapeUnicode, CharEscapeUnicode>, } macro_rules! escape_types_impls { ($( $Name: ident ),+) => {$( #[stable(feature = "str_escape", since = "1.34.0")] impl<'a> fmt::Display for $Name<'a> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { self.clone().try_for_each(|c| f.write_char(c)) } } #[stable(feature = "str_escape", since = "1.34.0")] impl<'a> Iterator for $Name<'a> { type Item = char; #[inline] fn next(&mut self) -> Option<char> { self.inner.next() } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() } #[inline] fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> { self.inner.try_fold(init, fold) } #[inline] fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where Fold: FnMut(Acc, Self::Item) -> Acc, { self.inner.fold(init, fold) } } #[stable(feature = "str_escape", since = "1.34.0")] impl<'a> FusedIterator for $Name<'a> {} )+} } escape_types_impls!(EscapeDebug, EscapeDefault, EscapeUnicode);