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Diffstat (limited to 'library/alloc/src/str.rs')
| -rw-r--r-- | library/alloc/src/str.rs | 576 |
1 files changed, 576 insertions, 0 deletions
diff --git a/library/alloc/src/str.rs b/library/alloc/src/str.rs new file mode 100644 index 00000000000..339592728ac --- /dev/null +++ b/library/alloc/src/str.rs @@ -0,0 +1,576 @@ +//! 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. + /// + /// # 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. + /// + /// # 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. + /// + /// # 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. + /// + /// # 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. + /// + /// [`Box<str>`]: Box + /// + /// # 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. + /// + /// # 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); + /// ``` + #[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`]: str::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`]: str::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> { + unsafe { Box::from_raw(Box::into_raw(v) as *mut str) } +} |