| //! Unicode string slices. |
| //! |
| //! *[See also the `str` primitive type](../../std/primitive.str.html).* |
| //! |
| //! The `&str` type is one of the two main string types, the other being `String`. |
| //! Unlike its `String` counterpart, its contents are borrowed. |
| //! |
| //! # Basic Usage |
| //! |
| //! A basic string declaration of `&str` type: |
| //! |
| //! ``` |
| //! let hello_world = "Hello, World!"; |
| //! ``` |
| //! |
| //! Here we have declared a string literal, also known as a string slice. |
| //! String literals have a static lifetime, which means the string `hello_world` |
| //! is guaranteed to be valid for the duration of the entire program. |
| //! We can explicitly specify `hello_world`'s lifetime as well: |
| //! |
| //! ``` |
| //! let hello_world: &'static str = "Hello, world!"; |
| //! ``` |
| |
| #![stable(feature = "rust1", since = "1.0.0")] |
| // Many of the usings in this module are only used in the test configuration. |
| // It's cleaner to just turn off the unused_imports warning than to fix them. |
| #![allow(unused_imports)] |
| |
| use core::borrow::{Borrow, BorrowMut}; |
| use core::iter::FusedIterator; |
| use core::mem; |
| use core::ptr; |
| use core::str::pattern::{DoubleEndedSearcher, Pattern, ReverseSearcher, Searcher}; |
| use core::unicode::conversions; |
| |
| use crate::borrow::ToOwned; |
| use crate::boxed::Box; |
| use crate::slice::{Concat, Join, SliceIndex}; |
| use crate::string::String; |
| use crate::vec::Vec; |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::str::pattern; |
| #[stable(feature = "encode_utf16", since = "1.8.0")] |
| pub use core::str::EncodeUtf16; |
| #[stable(feature = "split_ascii_whitespace", since = "1.34.0")] |
| pub use core::str::SplitAsciiWhitespace; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::str::SplitWhitespace; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::str::{from_utf8, from_utf8_mut, Bytes, CharIndices, Chars}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::str::{from_utf8_unchecked, from_utf8_unchecked_mut, ParseBoolError}; |
| #[stable(feature = "str_escape", since = "1.34.0")] |
| pub use core::str::{EscapeDebug, EscapeDefault, EscapeUnicode}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::str::{FromStr, Utf8Error}; |
| #[allow(deprecated)] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::str::{Lines, LinesAny}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::str::{MatchIndices, RMatchIndices}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::str::{Matches, RMatches}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::str::{RSplit, Split}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::str::{RSplitN, SplitN}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::str::{RSplitTerminator, SplitTerminator}; |
| |
| /// Note: `str` in `Concat<str>` is not meaningful here. |
| /// This type parameter of the trait only exists to enable another impl. |
| #[unstable(feature = "slice_concat_ext", issue = "27747")] |
| impl<S: Borrow<str>> Concat<str> for [S] { |
| type Output = String; |
| |
| fn concat(slice: &Self) -> String { |
| Join::join(slice, "") |
| } |
| } |
| |
| #[unstable(feature = "slice_concat_ext", issue = "27747")] |
| impl<S: Borrow<str>> Join<&str> for [S] { |
| type Output = String; |
| |
| fn join(slice: &Self, sep: &str) -> String { |
| unsafe { String::from_utf8_unchecked(join_generic_copy(slice, sep.as_bytes())) } |
| } |
| } |
| |
| macro_rules! spezialize_for_lengths { |
| ($separator:expr, $target:expr, $iter:expr; $($num:expr),*) => { |
| let mut target = $target; |
| let iter = $iter; |
| let sep_bytes = $separator; |
| match $separator.len() { |
| $( |
| // loops with hardcoded sizes run much faster |
| // specialize the cases with small separator lengths |
| $num => { |
| for s in iter { |
| copy_slice_and_advance!(target, sep_bytes); |
| copy_slice_and_advance!(target, s.borrow().as_ref()); |
| } |
| }, |
| )* |
| _ => { |
| // arbitrary non-zero size fallback |
| for s in iter { |
| copy_slice_and_advance!(target, sep_bytes); |
| copy_slice_and_advance!(target, s.borrow().as_ref()); |
| } |
| } |
| } |
| }; |
| } |
| |
| macro_rules! copy_slice_and_advance { |
| ($target:expr, $bytes:expr) => { |
| let len = $bytes.len(); |
| let (head, tail) = { $target }.split_at_mut(len); |
| head.copy_from_slice($bytes); |
| $target = tail; |
| }; |
| } |
| |
| // Optimized join implementation that works for both Vec<T> (T: Copy) and String's inner vec |
| // Currently (2018-05-13) there is a bug with type inference and specialization (see issue #36262) |
| // For this reason SliceConcat<T> is not specialized for T: Copy and SliceConcat<str> is the |
| // only user of this function. It is left in place for the time when that is fixed. |
| // |
| // the bounds for String-join are S: Borrow<str> and for Vec-join Borrow<[T]> |
| // [T] and str both impl AsRef<[T]> for some T |
| // => s.borrow().as_ref() and we always have slices |
| fn join_generic_copy<B, T, S>(slice: &[S], sep: &[T]) -> Vec<T> |
| where |
| T: Copy, |
| B: AsRef<[T]> + ?Sized, |
| S: Borrow<B>, |
| { |
| let sep_len = sep.len(); |
| let mut iter = slice.iter(); |
| |
| // the first slice is the only one without a separator preceding it |
| let first = match iter.next() { |
| Some(first) => first, |
| None => return vec![], |
| }; |
| |
| // compute the exact total length of the joined Vec |
| // if the `len` calculation overflows, we'll panic |
| // we would have run out of memory anyway and the rest of the function requires |
| // the entire Vec pre-allocated for safety |
| let len = sep_len |
| .checked_mul(iter.len()) |
| .and_then(|n| { |
| slice.iter().map(|s| s.borrow().as_ref().len()).try_fold(n, usize::checked_add) |
| }) |
| .expect("attempt to join into collection with len > usize::MAX"); |
| |
| // crucial for safety |
| let mut result = Vec::with_capacity(len); |
| assert!(result.capacity() >= len); |
| |
| result.extend_from_slice(first.borrow().as_ref()); |
| |
| unsafe { |
| { |
| let pos = result.len(); |
| let target = result.get_unchecked_mut(pos..len); |
| |
| // copy separator and slices over without bounds checks |
| // generate loops with hardcoded offsets for small separators |
| // massive improvements possible (~ x2) |
| spezialize_for_lengths!(sep, target, iter; 0, 1, 2, 3, 4); |
| } |
| result.set_len(len); |
| } |
| result |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl Borrow<str> for String { |
| #[inline] |
| fn borrow(&self) -> &str { |
| &self[..] |
| } |
| } |
| |
| #[stable(feature = "string_borrow_mut", since = "1.36.0")] |
| impl BorrowMut<str> for String { |
| #[inline] |
| fn borrow_mut(&mut self) -> &mut str { |
| &mut self[..] |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl ToOwned for str { |
| type Owned = String; |
| #[inline] |
| fn to_owned(&self) -> String { |
| unsafe { String::from_utf8_unchecked(self.as_bytes().to_owned()) } |
| } |
| |
| fn clone_into(&self, target: &mut String) { |
| let mut b = mem::take(target).into_bytes(); |
| self.as_bytes().clone_into(&mut b); |
| *target = unsafe { String::from_utf8_unchecked(b) } |
| } |
| } |
| |
| /// Methods for string slices. |
| #[lang = "str_alloc"] |
| #[cfg(not(test))] |
| impl str { |
| /// Converts a `Box<str>` into a `Box<[u8]>` without copying or allocating. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// let s = "this is a string"; |
| /// let boxed_str = s.to_owned().into_boxed_str(); |
| /// let boxed_bytes = boxed_str.into_boxed_bytes(); |
| /// assert_eq!(*boxed_bytes, *s.as_bytes()); |
| /// ``` |
| #[stable(feature = "str_box_extras", since = "1.20.0")] |
| #[inline] |
| pub fn into_boxed_bytes(self: Box<str>) -> Box<[u8]> { |
| self.into() |
| } |
| |
| /// Replaces all matches of a pattern with another string. |
| /// |
| /// `replace` creates a new [`String`], and copies the data from this string slice into it. |
| /// While doing so, it attempts to find matches of a pattern. If it finds any, it |
| /// replaces them with the replacement string slice. |
| /// |
| /// [`String`]: string/struct.String.html |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// let s = "this is old"; |
| /// |
| /// assert_eq!("this is new", s.replace("old", "new")); |
| /// ``` |
| /// |
| /// When the pattern doesn't match: |
| /// |
| /// ``` |
| /// let s = "this is old"; |
| /// assert_eq!(s, s.replace("cookie monster", "little lamb")); |
| /// ``` |
| #[must_use = "this returns the replaced string as a new allocation, \ |
| without modifying the original"] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn replace<'a, P: Pattern<'a>>(&'a self, from: P, to: &str) -> String { |
| let mut result = String::new(); |
| let mut last_end = 0; |
| for (start, part) in self.match_indices(from) { |
| result.push_str(unsafe { self.get_unchecked(last_end..start) }); |
| result.push_str(to); |
| last_end = start + part.len(); |
| } |
| result.push_str(unsafe { self.get_unchecked(last_end..self.len()) }); |
| result |
| } |
| |
| /// Replaces first N matches of a pattern with another string. |
| /// |
| /// `replacen` creates a new [`String`], and copies the data from this string slice into it. |
| /// While doing so, it attempts to find matches of a pattern. If it finds any, it |
| /// replaces them with the replacement string slice at most `count` times. |
| /// |
| /// [`String`]: string/struct.String.html |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// let s = "foo foo 123 foo"; |
| /// assert_eq!("new new 123 foo", s.replacen("foo", "new", 2)); |
| /// assert_eq!("faa fao 123 foo", s.replacen('o', "a", 3)); |
| /// assert_eq!("foo foo new23 foo", s.replacen(char::is_numeric, "new", 1)); |
| /// ``` |
| /// |
| /// When the pattern doesn't match: |
| /// |
| /// ``` |
| /// let s = "this is old"; |
| /// assert_eq!(s, s.replacen("cookie monster", "little lamb", 10)); |
| /// ``` |
| #[must_use = "this returns the replaced string as a new allocation, \ |
| without modifying the original"] |
| #[stable(feature = "str_replacen", since = "1.16.0")] |
| pub fn replacen<'a, P: Pattern<'a>>(&'a self, pat: P, to: &str, count: usize) -> String { |
| // Hope to reduce the times of re-allocation |
| let mut result = String::with_capacity(32); |
| let mut last_end = 0; |
| for (start, part) in self.match_indices(pat).take(count) { |
| result.push_str(unsafe { self.get_unchecked(last_end..start) }); |
| result.push_str(to); |
| last_end = start + part.len(); |
| } |
| result.push_str(unsafe { self.get_unchecked(last_end..self.len()) }); |
| result |
| } |
| |
| /// Returns the lowercase equivalent of this string slice, as a new [`String`]. |
| /// |
| /// 'Lowercase' is defined according to the terms of the Unicode Derived Core Property |
| /// `Lowercase`. |
| /// |
| /// Since some characters can expand into multiple characters when changing |
| /// the case, this function returns a [`String`] instead of modifying the |
| /// parameter in-place. |
| /// |
| /// [`String`]: string/struct.String.html |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// let s = "HELLO"; |
| /// |
| /// assert_eq!("hello", s.to_lowercase()); |
| /// ``` |
| /// |
| /// A tricky example, with sigma: |
| /// |
| /// ``` |
| /// let sigma = "Σ"; |
| /// |
| /// assert_eq!("σ", sigma.to_lowercase()); |
| /// |
| /// // but at the end of a word, it's ς, not σ: |
| /// let odysseus = "ὈΔΥΣΣΕΎΣ"; |
| /// |
| /// assert_eq!("ὀδυσσεύς", odysseus.to_lowercase()); |
| /// ``` |
| /// |
| /// Languages without case are not changed: |
| /// |
| /// ``` |
| /// let new_year = "农历新年"; |
| /// |
| /// assert_eq!(new_year, new_year.to_lowercase()); |
| /// ``` |
| #[stable(feature = "unicode_case_mapping", since = "1.2.0")] |
| pub fn to_lowercase(&self) -> String { |
| let mut s = String::with_capacity(self.len()); |
| for (i, c) in self[..].char_indices() { |
| if c == 'Σ' { |
| // Σ maps to σ, except at the end of a word where it maps to ς. |
| // This is the only conditional (contextual) but language-independent mapping |
| // in `SpecialCasing.txt`, |
| // so hard-code it rather than have a generic "condition" mechanism. |
| // See https://github.com/rust-lang/rust/issues/26035 |
| map_uppercase_sigma(self, i, &mut s) |
| } else { |
| match conversions::to_lower(c) { |
| [a, '\0', _] => s.push(a), |
| [a, b, '\0'] => { |
| s.push(a); |
| s.push(b); |
| } |
| [a, b, c] => { |
| s.push(a); |
| s.push(b); |
| s.push(c); |
| } |
| } |
| } |
| } |
| return s; |
| |
| fn map_uppercase_sigma(from: &str, i: usize, to: &mut String) { |
| // See http://www.unicode.org/versions/Unicode7.0.0/ch03.pdf#G33992 |
| // for the definition of `Final_Sigma`. |
| debug_assert!('Σ'.len_utf8() == 2); |
| let is_word_final = case_ignoreable_then_cased(from[..i].chars().rev()) |
| && !case_ignoreable_then_cased(from[i + 2..].chars()); |
| to.push_str(if is_word_final { "ς" } else { "σ" }); |
| } |
| |
| fn case_ignoreable_then_cased<I: Iterator<Item = char>>(iter: I) -> bool { |
| use core::unicode::derived_property::{Case_Ignorable, Cased}; |
| match iter.skip_while(|&c| Case_Ignorable(c)).next() { |
| Some(c) => Cased(c), |
| None => false, |
| } |
| } |
| } |
| |
| /// Returns the uppercase equivalent of this string slice, as a new [`String`]. |
| /// |
| /// 'Uppercase' is defined according to the terms of the Unicode Derived Core Property |
| /// `Uppercase`. |
| /// |
| /// Since some characters can expand into multiple characters when changing |
| /// the case, this function returns a [`String`] instead of modifying the |
| /// parameter in-place. |
| /// |
| /// [`String`]: string/struct.String.html |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// let s = "hello"; |
| /// |
| /// assert_eq!("HELLO", s.to_uppercase()); |
| /// ``` |
| /// |
| /// Scripts without case are not changed: |
| /// |
| /// ``` |
| /// let new_year = "农历新年"; |
| /// |
| /// assert_eq!(new_year, new_year.to_uppercase()); |
| /// ``` |
| /// |
| /// One character can become multiple: |
| /// ``` |
| /// let s = "tschüß"; |
| /// |
| /// assert_eq!("TSCHÜSS", s.to_uppercase()); |
| /// ``` |
| #[stable(feature = "unicode_case_mapping", since = "1.2.0")] |
| pub fn to_uppercase(&self) -> String { |
| let mut s = String::with_capacity(self.len()); |
| for c in self[..].chars() { |
| match conversions::to_upper(c) { |
| [a, '\0', _] => s.push(a), |
| [a, b, '\0'] => { |
| s.push(a); |
| s.push(b); |
| } |
| [a, b, c] => { |
| s.push(a); |
| s.push(b); |
| s.push(c); |
| } |
| } |
| } |
| s |
| } |
| |
| /// Converts a [`Box<str>`] into a [`String`] without copying or allocating. |
| /// |
| /// [`String`]: string/struct.String.html |
| /// [`Box<str>`]: boxed/struct.Box.html |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// let string = String::from("birthday gift"); |
| /// let boxed_str = string.clone().into_boxed_str(); |
| /// |
| /// assert_eq!(boxed_str.into_string(), string); |
| /// ``` |
| #[stable(feature = "box_str", since = "1.4.0")] |
| #[inline] |
| pub fn into_string(self: Box<str>) -> String { |
| let slice = Box::<[u8]>::from(self); |
| unsafe { String::from_utf8_unchecked(slice.into_vec()) } |
| } |
| |
| /// Creates a new [`String`] by repeating a string `n` times. |
| /// |
| /// # Panics |
| /// |
| /// This function will panic if the capacity would overflow. |
| /// |
| /// [`String`]: string/struct.String.html |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// assert_eq!("abc".repeat(4), String::from("abcabcabcabc")); |
| /// ``` |
| /// |
| /// A panic upon overflow: |
| /// |
| /// ```should_panic |
| /// // this will panic at runtime |
| /// "0123456789abcdef".repeat(usize::max_value()); |
| /// ``` |
| #[stable(feature = "repeat_str", since = "1.16.0")] |
| pub fn repeat(&self, n: usize) -> String { |
| unsafe { String::from_utf8_unchecked(self.as_bytes().repeat(n)) } |
| } |
| |
| /// Returns a copy of this string where each character is mapped to its |
| /// ASCII upper case equivalent. |
| /// |
| /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', |
| /// but non-ASCII letters are unchanged. |
| /// |
| /// To uppercase the value in-place, use [`make_ascii_uppercase`]. |
| /// |
| /// To uppercase ASCII characters in addition to non-ASCII characters, use |
| /// [`to_uppercase`]. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let s = "Grüße, Jürgen ❤"; |
| /// |
| /// assert_eq!("GRüßE, JüRGEN ❤", s.to_ascii_uppercase()); |
| /// ``` |
| /// |
| /// [`make_ascii_uppercase`]: #method.make_ascii_uppercase |
| /// [`to_uppercase`]: #method.to_uppercase |
| #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] |
| #[inline] |
| pub fn to_ascii_uppercase(&self) -> String { |
| let mut bytes = self.as_bytes().to_vec(); |
| bytes.make_ascii_uppercase(); |
| // make_ascii_uppercase() preserves the UTF-8 invariant. |
| unsafe { String::from_utf8_unchecked(bytes) } |
| } |
| |
| /// Returns a copy of this string where each character is mapped to its |
| /// ASCII lower case equivalent. |
| /// |
| /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', |
| /// but non-ASCII letters are unchanged. |
| /// |
| /// To lowercase the value in-place, use [`make_ascii_lowercase`]. |
| /// |
| /// To lowercase ASCII characters in addition to non-ASCII characters, use |
| /// [`to_lowercase`]. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let s = "Grüße, Jürgen ❤"; |
| /// |
| /// assert_eq!("grüße, jürgen ❤", s.to_ascii_lowercase()); |
| /// ``` |
| /// |
| /// [`make_ascii_lowercase`]: #method.make_ascii_lowercase |
| /// [`to_lowercase`]: #method.to_lowercase |
| #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] |
| #[inline] |
| pub fn to_ascii_lowercase(&self) -> String { |
| let mut bytes = self.as_bytes().to_vec(); |
| bytes.make_ascii_lowercase(); |
| // make_ascii_lowercase() preserves the UTF-8 invariant. |
| unsafe { String::from_utf8_unchecked(bytes) } |
| } |
| } |
| |
| /// Converts a boxed slice of bytes to a boxed string slice without checking |
| /// that the string contains valid UTF-8. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// let smile_utf8 = Box::new([226, 152, 186]); |
| /// let smile = unsafe { std::str::from_boxed_utf8_unchecked(smile_utf8) }; |
| /// |
| /// assert_eq!("☺", &*smile); |
| /// ``` |
| #[stable(feature = "str_box_extras", since = "1.20.0")] |
| #[inline] |
| pub unsafe fn from_boxed_utf8_unchecked(v: Box<[u8]>) -> Box<str> { |
| Box::from_raw(Box::into_raw(v) as *mut str) |
| } |