mirror of https://github.com/rust-lang/rust
3055 lines
94 KiB
Rust
3055 lines
94 KiB
Rust
//! A UTF-8–encoded, growable string.
|
||
//!
|
||
//! This module contains the [`String`] type, the [`ToString`] trait for
|
||
//! converting to strings, and several error types that may result from
|
||
//! working with [`String`]s.
|
||
//!
|
||
//! # Examples
|
||
//!
|
||
//! There are multiple ways to create a new [`String`] from a string literal:
|
||
//!
|
||
//! ```
|
||
//! let s = "Hello".to_string();
|
||
//!
|
||
//! let s = String::from("world");
|
||
//! let s: String = "also this".into();
|
||
//! ```
|
||
//!
|
||
//! You can create a new [`String`] from an existing one by concatenating with
|
||
//! `+`:
|
||
//!
|
||
//! ```
|
||
//! let s = "Hello".to_string();
|
||
//!
|
||
//! let message = s + " world!";
|
||
//! ```
|
||
//!
|
||
//! If you have a vector of valid UTF-8 bytes, you can make a [`String`] out of
|
||
//! it. You can do the reverse too.
|
||
//!
|
||
//! ```
|
||
//! let sparkle_heart = vec![240, 159, 146, 150];
|
||
//!
|
||
//! // We know these bytes are valid, so we'll use `unwrap()`.
|
||
//! let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
|
||
//!
|
||
//! assert_eq!("💖", sparkle_heart);
|
||
//!
|
||
//! let bytes = sparkle_heart.into_bytes();
|
||
//!
|
||
//! assert_eq!(bytes, [240, 159, 146, 150]);
|
||
//! ```
|
||
|
||
#![stable(feature = "rust1", since = "1.0.0")]
|
||
|
||
use core::error::Error;
|
||
use core::fmt;
|
||
use core::hash;
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use core::iter::from_fn;
|
||
use core::iter::FusedIterator;
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use core::ops::Add;
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use core::ops::AddAssign;
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use core::ops::Bound::{Excluded, Included, Unbounded};
|
||
use core::ops::{self, Range, RangeBounds};
|
||
use core::ptr;
|
||
use core::slice;
|
||
use core::str::pattern::Pattern;
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use crate::alloc::Allocator;
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use crate::borrow::{Cow, ToOwned};
|
||
use crate::boxed::Box;
|
||
use crate::collections::TryReserveError;
|
||
use crate::str::{self, from_utf8_unchecked_mut, Chars, Utf8Error};
|
||
#[cfg(not(no_global_oom_handling))]
|
||
use crate::str::{from_boxed_utf8_unchecked, FromStr};
|
||
use crate::vec::Vec;
|
||
|
||
/// A UTF-8–encoded, growable string.
|
||
///
|
||
/// `String` is the most common string type. It has ownership over the contents
|
||
/// of the string, stored in a heap-allocated buffer (see [Representation](#representation)).
|
||
/// It is closely related to its borrowed counterpart, the primitive [`str`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// You can create a `String` from [a literal string][`&str`] with [`String::from`]:
|
||
///
|
||
/// [`String::from`]: From::from
|
||
///
|
||
/// ```
|
||
/// let hello = String::from("Hello, world!");
|
||
/// ```
|
||
///
|
||
/// You can append a [`char`] to a `String` with the [`push`] method, and
|
||
/// append a [`&str`] with the [`push_str`] method:
|
||
///
|
||
/// ```
|
||
/// let mut hello = String::from("Hello, ");
|
||
///
|
||
/// hello.push('w');
|
||
/// hello.push_str("orld!");
|
||
/// ```
|
||
///
|
||
/// [`push`]: String::push
|
||
/// [`push_str`]: String::push_str
|
||
///
|
||
/// If you have a vector of UTF-8 bytes, you can create a `String` from it with
|
||
/// the [`from_utf8`] method:
|
||
///
|
||
/// ```
|
||
/// // some bytes, in a vector
|
||
/// let sparkle_heart = vec![240, 159, 146, 150];
|
||
///
|
||
/// // We know these bytes are valid, so we'll use `unwrap()`.
|
||
/// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
|
||
///
|
||
/// assert_eq!("💖", sparkle_heart);
|
||
/// ```
|
||
///
|
||
/// [`from_utf8`]: String::from_utf8
|
||
///
|
||
/// # UTF-8
|
||
///
|
||
/// `String`s are always valid UTF-8. If you need a non-UTF-8 string, consider
|
||
/// [`OsString`]. It is similar, but without the UTF-8 constraint. Because UTF-8
|
||
/// is a variable width encoding, `String`s are typically smaller than an array of
|
||
/// the same `chars`:
|
||
///
|
||
/// ```
|
||
/// use std::mem;
|
||
///
|
||
/// // `s` is ASCII which represents each `char` as one byte
|
||
/// let s = "hello";
|
||
/// assert_eq!(s.len(), 5);
|
||
///
|
||
/// // A `char` array with the same contents would be longer because
|
||
/// // every `char` is four bytes
|
||
/// let s = ['h', 'e', 'l', 'l', 'o'];
|
||
/// let size: usize = s.into_iter().map(|c| mem::size_of_val(&c)).sum();
|
||
/// assert_eq!(size, 20);
|
||
///
|
||
/// // However, for non-ASCII strings, the difference will be smaller
|
||
/// // and sometimes they are the same
|
||
/// let s = "💖💖💖💖💖";
|
||
/// assert_eq!(s.len(), 20);
|
||
///
|
||
/// let s = ['💖', '💖', '💖', '💖', '💖'];
|
||
/// let size: usize = s.into_iter().map(|c| mem::size_of_val(&c)).sum();
|
||
/// assert_eq!(size, 20);
|
||
/// ```
|
||
///
|
||
/// This raises interesting questions as to how `s[i]` should work.
|
||
/// What should `i` be here? Several options include byte indices and
|
||
/// `char` indices but, because of UTF-8 encoding, only byte indices
|
||
/// would provide constant time indexing. Getting the `i`th `char`, for
|
||
/// example, is available using [`chars`]:
|
||
///
|
||
/// ```
|
||
/// let s = "hello";
|
||
/// let third_character = s.chars().nth(2);
|
||
/// assert_eq!(third_character, Some('l'));
|
||
///
|
||
/// let s = "💖💖💖💖💖";
|
||
/// let third_character = s.chars().nth(2);
|
||
/// assert_eq!(third_character, Some('💖'));
|
||
/// ```
|
||
///
|
||
/// Next, what should `s[i]` return? Because indexing returns a reference
|
||
/// to underlying data it could be `&u8`, `&[u8]`, or something else similar.
|
||
/// Since we're only providing one index, `&u8` makes the most sense but that
|
||
/// might not be what the user expects and can be explicitly achieved with
|
||
/// [`as_bytes()`]:
|
||
///
|
||
/// ```
|
||
/// // The first byte is 104 - the byte value of `'h'`
|
||
/// let s = "hello";
|
||
/// assert_eq!(s.as_bytes()[0], 104);
|
||
/// // or
|
||
/// assert_eq!(s.as_bytes()[0], b'h');
|
||
///
|
||
/// // The first byte is 240 which isn't obviously useful
|
||
/// let s = "💖💖💖💖💖";
|
||
/// assert_eq!(s.as_bytes()[0], 240);
|
||
/// ```
|
||
///
|
||
/// Due to these ambiguities/restrictions, indexing with a `usize` is simply
|
||
/// forbidden:
|
||
///
|
||
/// ```compile_fail,E0277
|
||
/// let s = "hello";
|
||
///
|
||
/// // The following will not compile!
|
||
/// println!("The first letter of s is {}", s[0]);
|
||
/// ```
|
||
///
|
||
/// It is more clear, however, how `&s[i..j]` should work (that is,
|
||
/// indexing with a range). It should accept byte indices (to be constant-time)
|
||
/// and return a `&str` which is UTF-8 encoded. This is also called "string slicing".
|
||
/// Note this will panic if the byte indices provided are not character
|
||
/// boundaries - see [`is_char_boundary`] for more details. See the implementations
|
||
/// for [`SliceIndex<str>`] for more details on string slicing. For a non-panicking
|
||
/// version of string slicing, see [`get`].
|
||
///
|
||
/// [`OsString`]: ../../std/ffi/struct.OsString.html "ffi::OsString"
|
||
/// [`SliceIndex<str>`]: core::slice::SliceIndex
|
||
/// [`as_bytes()`]: str::as_bytes
|
||
/// [`get`]: str::get
|
||
/// [`is_char_boundary`]: str::is_char_boundary
|
||
///
|
||
/// The [`bytes`] and [`chars`] methods return iterators over the bytes and
|
||
/// codepoints of the string, respectively. To iterate over codepoints along
|
||
/// with byte indices, use [`char_indices`].
|
||
///
|
||
/// [`bytes`]: str::bytes
|
||
/// [`chars`]: str::chars
|
||
/// [`char_indices`]: str::char_indices
|
||
///
|
||
/// # Deref
|
||
///
|
||
/// `String` implements <code>[Deref]<Target = [str]></code>, and so inherits all of [`str`]'s
|
||
/// methods. In addition, this means that you can pass a `String` to a
|
||
/// function which takes a [`&str`] by using an ampersand (`&`):
|
||
///
|
||
/// ```
|
||
/// fn takes_str(s: &str) { }
|
||
///
|
||
/// let s = String::from("Hello");
|
||
///
|
||
/// takes_str(&s);
|
||
/// ```
|
||
///
|
||
/// This will create a [`&str`] from the `String` and pass it in. This
|
||
/// conversion is very inexpensive, and so generally, functions will accept
|
||
/// [`&str`]s as arguments unless they need a `String` for some specific
|
||
/// reason.
|
||
///
|
||
/// In certain cases Rust doesn't have enough information to make this
|
||
/// conversion, known as [`Deref`] coercion. In the following example a string
|
||
/// slice [`&'a str`][`&str`] implements the trait `TraitExample`, and the function
|
||
/// `example_func` takes anything that implements the trait. In this case Rust
|
||
/// would need to make two implicit conversions, which Rust doesn't have the
|
||
/// means to do. For that reason, the following example will not compile.
|
||
///
|
||
/// ```compile_fail,E0277
|
||
/// trait TraitExample {}
|
||
///
|
||
/// impl<'a> TraitExample for &'a str {}
|
||
///
|
||
/// fn example_func<A: TraitExample>(example_arg: A) {}
|
||
///
|
||
/// let example_string = String::from("example_string");
|
||
/// example_func(&example_string);
|
||
/// ```
|
||
///
|
||
/// There are two options that would work instead. The first would be to
|
||
/// change the line `example_func(&example_string);` to
|
||
/// `example_func(example_string.as_str());`, using the method [`as_str()`]
|
||
/// to explicitly extract the string slice containing the string. The second
|
||
/// way changes `example_func(&example_string);` to
|
||
/// `example_func(&*example_string);`. In this case we are dereferencing a
|
||
/// `String` to a [`str`], then referencing the [`str`] back to
|
||
/// [`&str`]. The second way is more idiomatic, however both work to do the
|
||
/// conversion explicitly rather than relying on the implicit conversion.
|
||
///
|
||
/// # Representation
|
||
///
|
||
/// A `String` is made up of three components: a pointer to some bytes, a
|
||
/// length, and a capacity. The pointer points to the internal buffer which `String`
|
||
/// uses to store its data. The length is the number of bytes currently stored
|
||
/// in the buffer, and the capacity is the size of the buffer in bytes. As such,
|
||
/// the length will always be less than or equal to the capacity.
|
||
///
|
||
/// This buffer is always stored on the heap.
|
||
///
|
||
/// You can look at these with the [`as_ptr`], [`len`], and [`capacity`]
|
||
/// methods:
|
||
///
|
||
/// ```
|
||
/// use std::mem;
|
||
///
|
||
/// let story = String::from("Once upon a time...");
|
||
///
|
||
// FIXME Update this when vec_into_raw_parts is stabilized
|
||
/// // Prevent automatically dropping the String's data
|
||
/// let mut story = mem::ManuallyDrop::new(story);
|
||
///
|
||
/// let ptr = story.as_mut_ptr();
|
||
/// let len = story.len();
|
||
/// let capacity = story.capacity();
|
||
///
|
||
/// // story has nineteen bytes
|
||
/// assert_eq!(19, len);
|
||
///
|
||
/// // We can re-build a String out of ptr, len, and capacity. This is all
|
||
/// // unsafe because we are responsible for making sure the components are
|
||
/// // valid:
|
||
/// let s = unsafe { String::from_raw_parts(ptr, len, capacity) } ;
|
||
///
|
||
/// assert_eq!(String::from("Once upon a time..."), s);
|
||
/// ```
|
||
///
|
||
/// [`as_ptr`]: str::as_ptr
|
||
/// [`len`]: String::len
|
||
/// [`capacity`]: String::capacity
|
||
///
|
||
/// If a `String` has enough capacity, adding elements to it will not
|
||
/// re-allocate. For example, consider this program:
|
||
///
|
||
/// ```
|
||
/// let mut s = String::new();
|
||
///
|
||
/// println!("{}", s.capacity());
|
||
///
|
||
/// for _ in 0..5 {
|
||
/// s.push_str("hello");
|
||
/// println!("{}", s.capacity());
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// This will output the following:
|
||
///
|
||
/// ```text
|
||
/// 0
|
||
/// 8
|
||
/// 16
|
||
/// 16
|
||
/// 32
|
||
/// 32
|
||
/// ```
|
||
///
|
||
/// At first, we have no memory allocated at all, but as we append to the
|
||
/// string, it increases its capacity appropriately. If we instead use the
|
||
/// [`with_capacity`] method to allocate the correct capacity initially:
|
||
///
|
||
/// ```
|
||
/// let mut s = String::with_capacity(25);
|
||
///
|
||
/// println!("{}", s.capacity());
|
||
///
|
||
/// for _ in 0..5 {
|
||
/// s.push_str("hello");
|
||
/// println!("{}", s.capacity());
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// [`with_capacity`]: String::with_capacity
|
||
///
|
||
/// We end up with a different output:
|
||
///
|
||
/// ```text
|
||
/// 25
|
||
/// 25
|
||
/// 25
|
||
/// 25
|
||
/// 25
|
||
/// 25
|
||
/// ```
|
||
///
|
||
/// Here, there's no need to allocate more memory inside the loop.
|
||
///
|
||
/// [str]: prim@str "str"
|
||
/// [`str`]: prim@str "str"
|
||
/// [`&str`]: prim@str "&str"
|
||
/// [Deref]: core::ops::Deref "ops::Deref"
|
||
/// [`Deref`]: core::ops::Deref "ops::Deref"
|
||
/// [`as_str()`]: String::as_str
|
||
#[derive(PartialEq, PartialOrd, Eq, Ord)]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[cfg_attr(not(test), lang = "String")]
|
||
pub struct String {
|
||
vec: Vec<u8>,
|
||
}
|
||
|
||
/// A possible error value when converting a `String` from a UTF-8 byte vector.
|
||
///
|
||
/// This type is the error type for the [`from_utf8`] method on [`String`]. It
|
||
/// is designed in such a way to carefully avoid reallocations: the
|
||
/// [`into_bytes`] method will give back the byte vector that was used in the
|
||
/// conversion attempt.
|
||
///
|
||
/// [`from_utf8`]: String::from_utf8
|
||
/// [`into_bytes`]: FromUtf8Error::into_bytes
|
||
///
|
||
/// The [`Utf8Error`] type provided by [`std::str`] represents an error that may
|
||
/// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's
|
||
/// an analogue to `FromUtf8Error`, and you can get one from a `FromUtf8Error`
|
||
/// through the [`utf8_error`] method.
|
||
///
|
||
/// [`Utf8Error`]: str::Utf8Error "std::str::Utf8Error"
|
||
/// [`std::str`]: core::str "std::str"
|
||
/// [`&str`]: prim@str "&str"
|
||
/// [`utf8_error`]: FromUtf8Error::utf8_error
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // some invalid bytes, in a vector
|
||
/// let bytes = vec![0, 159];
|
||
///
|
||
/// let value = String::from_utf8(bytes);
|
||
///
|
||
/// assert!(value.is_err());
|
||
/// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes());
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[cfg_attr(not(no_global_oom_handling), derive(Clone))]
|
||
#[derive(Debug, PartialEq, Eq)]
|
||
pub struct FromUtf8Error {
|
||
bytes: Vec<u8>,
|
||
error: Utf8Error,
|
||
}
|
||
|
||
/// A possible error value when converting a `String` from a UTF-16 byte slice.
|
||
///
|
||
/// This type is the error type for the [`from_utf16`] method on [`String`].
|
||
///
|
||
/// [`from_utf16`]: String::from_utf16
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // 𝄞mu<invalid>ic
|
||
/// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
|
||
/// 0xD800, 0x0069, 0x0063];
|
||
///
|
||
/// assert!(String::from_utf16(v).is_err());
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[derive(Debug)]
|
||
pub struct FromUtf16Error(());
|
||
|
||
impl String {
|
||
/// Creates a new empty `String`.
|
||
///
|
||
/// Given that the `String` is empty, this will not allocate any initial
|
||
/// buffer. While that means that this initial operation is very
|
||
/// inexpensive, it may cause excessive allocation later when you add
|
||
/// data. If you have an idea of how much data the `String` will hold,
|
||
/// consider the [`with_capacity`] method to prevent excessive
|
||
/// re-allocation.
|
||
///
|
||
/// [`with_capacity`]: String::with_capacity
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s = String::new();
|
||
/// ```
|
||
#[inline]
|
||
#[rustc_const_stable(feature = "const_string_new", since = "1.39.0")]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[must_use]
|
||
pub const fn new() -> String {
|
||
String { vec: Vec::new() }
|
||
}
|
||
|
||
/// Creates a new empty `String` with at least the specified capacity.
|
||
///
|
||
/// `String`s have an internal buffer to hold their data. The capacity is
|
||
/// the length of that buffer, and can be queried with the [`capacity`]
|
||
/// method. This method creates an empty `String`, but one with an initial
|
||
/// buffer that can hold at least `capacity` bytes. This is useful when you
|
||
/// may be appending a bunch of data to the `String`, reducing the number of
|
||
/// reallocations it needs to do.
|
||
///
|
||
/// [`capacity`]: String::capacity
|
||
///
|
||
/// If the given capacity is `0`, no allocation will occur, and this method
|
||
/// is identical to the [`new`] method.
|
||
///
|
||
/// [`new`]: String::new
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::with_capacity(10);
|
||
///
|
||
/// // The String contains no chars, even though it has capacity for more
|
||
/// assert_eq!(s.len(), 0);
|
||
///
|
||
/// // These are all done without reallocating...
|
||
/// let cap = s.capacity();
|
||
/// for _ in 0..10 {
|
||
/// s.push('a');
|
||
/// }
|
||
///
|
||
/// assert_eq!(s.capacity(), cap);
|
||
///
|
||
/// // ...but this may make the string reallocate
|
||
/// s.push('a');
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[must_use]
|
||
pub fn with_capacity(capacity: usize) -> String {
|
||
String { vec: Vec::with_capacity(capacity) }
|
||
}
|
||
|
||
/// Creates a new empty `String` with at least the specified capacity.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// Returns [`Err`] if the capacity exceeds `isize::MAX` bytes,
|
||
/// or if the memory allocator reports failure.
|
||
///
|
||
#[inline]
|
||
#[unstable(feature = "try_with_capacity", issue = "91913")]
|
||
pub fn try_with_capacity(capacity: usize) -> Result<String, TryReserveError> {
|
||
Ok(String { vec: Vec::try_with_capacity(capacity)? })
|
||
}
|
||
|
||
// HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is
|
||
// required for this method definition, is not available. Since we don't
|
||
// require this method for testing purposes, I'll just stub it
|
||
// NB see the slice::hack module in slice.rs for more information
|
||
#[inline]
|
||
#[cfg(test)]
|
||
pub fn from_str(_: &str) -> String {
|
||
panic!("not available with cfg(test)");
|
||
}
|
||
|
||
/// Converts a vector of bytes to a `String`.
|
||
///
|
||
/// A string ([`String`]) is made of bytes ([`u8`]), and a vector of bytes
|
||
/// ([`Vec<u8>`]) is made of bytes, so this function converts between the
|
||
/// two. Not all byte slices are valid `String`s, however: `String`
|
||
/// requires that it is valid UTF-8. `from_utf8()` checks to ensure that
|
||
/// the bytes are valid UTF-8, and then does the conversion.
|
||
///
|
||
/// If you are sure that the byte slice is valid UTF-8, and you don't want
|
||
/// to incur the overhead of the validity check, there is an unsafe version
|
||
/// of this function, [`from_utf8_unchecked`], which has the same behavior
|
||
/// but skips the check.
|
||
///
|
||
/// This method will take care to not copy the vector, for efficiency's
|
||
/// sake.
|
||
///
|
||
/// If you need a [`&str`] instead of a `String`, consider
|
||
/// [`str::from_utf8`].
|
||
///
|
||
/// The inverse of this method is [`into_bytes`].
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// Returns [`Err`] if the slice is not UTF-8 with a description as to why the
|
||
/// provided bytes are not UTF-8. The vector you moved in is also included.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// // some bytes, in a vector
|
||
/// let sparkle_heart = vec![240, 159, 146, 150];
|
||
///
|
||
/// // We know these bytes are valid, so we'll use `unwrap()`.
|
||
/// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
|
||
///
|
||
/// assert_eq!("💖", sparkle_heart);
|
||
/// ```
|
||
///
|
||
/// Incorrect bytes:
|
||
///
|
||
/// ```
|
||
/// // some invalid bytes, in a vector
|
||
/// let sparkle_heart = vec![0, 159, 146, 150];
|
||
///
|
||
/// assert!(String::from_utf8(sparkle_heart).is_err());
|
||
/// ```
|
||
///
|
||
/// See the docs for [`FromUtf8Error`] for more details on what you can do
|
||
/// with this error.
|
||
///
|
||
/// [`from_utf8_unchecked`]: String::from_utf8_unchecked
|
||
/// [`Vec<u8>`]: crate::vec::Vec "Vec"
|
||
/// [`&str`]: prim@str "&str"
|
||
/// [`into_bytes`]: String::into_bytes
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn from_utf8(vec: Vec<u8>) -> Result<String, FromUtf8Error> {
|
||
match str::from_utf8(&vec) {
|
||
Ok(..) => Ok(String { vec }),
|
||
Err(e) => Err(FromUtf8Error { bytes: vec, error: e }),
|
||
}
|
||
}
|
||
|
||
/// Converts a slice of bytes to a string, including invalid characters.
|
||
///
|
||
/// Strings are made of bytes ([`u8`]), and a slice of bytes
|
||
/// ([`&[u8]`][byteslice]) is made of bytes, so this function converts
|
||
/// between the two. Not all byte slices are valid strings, however: strings
|
||
/// are required to be valid UTF-8. During this conversion,
|
||
/// `from_utf8_lossy()` will replace any invalid UTF-8 sequences with
|
||
/// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD], which looks like this: <20>
|
||
///
|
||
/// [byteslice]: prim@slice
|
||
/// [U+FFFD]: core::char::REPLACEMENT_CHARACTER
|
||
///
|
||
/// If you are sure that the byte slice is valid UTF-8, and you don't want
|
||
/// to incur the overhead of the conversion, there is an unsafe version
|
||
/// of this function, [`from_utf8_unchecked`], which has the same behavior
|
||
/// but skips the checks.
|
||
///
|
||
/// [`from_utf8_unchecked`]: String::from_utf8_unchecked
|
||
///
|
||
/// This function returns a [`Cow<'a, str>`]. If our byte slice is invalid
|
||
/// UTF-8, then we need to insert the replacement characters, which will
|
||
/// change the size of the string, and hence, require a `String`. But if
|
||
/// it's already valid UTF-8, we don't need a new allocation. This return
|
||
/// type allows us to handle both cases.
|
||
///
|
||
/// [`Cow<'a, str>`]: crate::borrow::Cow "borrow::Cow"
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// // some bytes, in a vector
|
||
/// let sparkle_heart = vec![240, 159, 146, 150];
|
||
///
|
||
/// let sparkle_heart = String::from_utf8_lossy(&sparkle_heart);
|
||
///
|
||
/// assert_eq!("💖", sparkle_heart);
|
||
/// ```
|
||
///
|
||
/// Incorrect bytes:
|
||
///
|
||
/// ```
|
||
/// // some invalid bytes
|
||
/// let input = b"Hello \xF0\x90\x80World";
|
||
/// let output = String::from_utf8_lossy(input);
|
||
///
|
||
/// assert_eq!("Hello <20>World", output);
|
||
/// ```
|
||
#[must_use]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn from_utf8_lossy(v: &[u8]) -> Cow<'_, str> {
|
||
let mut iter = v.utf8_chunks();
|
||
|
||
let first_valid = if let Some(chunk) = iter.next() {
|
||
let valid = chunk.valid();
|
||
if chunk.invalid().is_empty() {
|
||
debug_assert_eq!(valid.len(), v.len());
|
||
return Cow::Borrowed(valid);
|
||
}
|
||
valid
|
||
} else {
|
||
return Cow::Borrowed("");
|
||
};
|
||
|
||
const REPLACEMENT: &str = "\u{FFFD}";
|
||
|
||
let mut res = String::with_capacity(v.len());
|
||
res.push_str(first_valid);
|
||
res.push_str(REPLACEMENT);
|
||
|
||
for chunk in iter {
|
||
res.push_str(chunk.valid());
|
||
if !chunk.invalid().is_empty() {
|
||
res.push_str(REPLACEMENT);
|
||
}
|
||
}
|
||
|
||
Cow::Owned(res)
|
||
}
|
||
|
||
/// Decode a UTF-16–encoded vector `v` into a `String`, returning [`Err`]
|
||
/// if `v` contains any invalid data.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // 𝄞music
|
||
/// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
|
||
/// 0x0073, 0x0069, 0x0063];
|
||
/// assert_eq!(String::from("𝄞music"),
|
||
/// String::from_utf16(v).unwrap());
|
||
///
|
||
/// // 𝄞mu<invalid>ic
|
||
/// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
|
||
/// 0xD800, 0x0069, 0x0063];
|
||
/// assert!(String::from_utf16(v).is_err());
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn from_utf16(v: &[u16]) -> Result<String, FromUtf16Error> {
|
||
// This isn't done via collect::<Result<_, _>>() for performance reasons.
|
||
// FIXME: the function can be simplified again when #48994 is closed.
|
||
let mut ret = String::with_capacity(v.len());
|
||
for c in char::decode_utf16(v.iter().cloned()) {
|
||
if let Ok(c) = c {
|
||
ret.push(c);
|
||
} else {
|
||
return Err(FromUtf16Error(()));
|
||
}
|
||
}
|
||
Ok(ret)
|
||
}
|
||
|
||
/// Decode a UTF-16–encoded slice `v` into a `String`, replacing
|
||
/// invalid data with [the replacement character (`U+FFFD`)][U+FFFD].
|
||
///
|
||
/// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`],
|
||
/// `from_utf16_lossy` returns a `String` since the UTF-16 to UTF-8
|
||
/// conversion requires a memory allocation.
|
||
///
|
||
/// [`from_utf8_lossy`]: String::from_utf8_lossy
|
||
/// [`Cow<'a, str>`]: crate::borrow::Cow "borrow::Cow"
|
||
/// [U+FFFD]: core::char::REPLACEMENT_CHARACTER
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // 𝄞mus<invalid>ic<invalid>
|
||
/// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
|
||
/// 0x0073, 0xDD1E, 0x0069, 0x0063,
|
||
/// 0xD834];
|
||
///
|
||
/// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"),
|
||
/// String::from_utf16_lossy(v));
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[must_use]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn from_utf16_lossy(v: &[u16]) -> String {
|
||
char::decode_utf16(v.iter().cloned())
|
||
.map(|r| r.unwrap_or(char::REPLACEMENT_CHARACTER))
|
||
.collect()
|
||
}
|
||
|
||
/// Decode a UTF-16LE–encoded vector `v` into a `String`, returning [`Err`]
|
||
/// if `v` contains any invalid data.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// #![feature(str_from_utf16_endian)]
|
||
/// // 𝄞music
|
||
/// let v = &[0x34, 0xD8, 0x1E, 0xDD, 0x6d, 0x00, 0x75, 0x00,
|
||
/// 0x73, 0x00, 0x69, 0x00, 0x63, 0x00];
|
||
/// assert_eq!(String::from("𝄞music"),
|
||
/// String::from_utf16le(v).unwrap());
|
||
///
|
||
/// // 𝄞mu<invalid>ic
|
||
/// let v = &[0x34, 0xD8, 0x1E, 0xDD, 0x6d, 0x00, 0x75, 0x00,
|
||
/// 0x00, 0xD8, 0x69, 0x00, 0x63, 0x00];
|
||
/// assert!(String::from_utf16le(v).is_err());
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "str_from_utf16_endian", issue = "116258")]
|
||
pub fn from_utf16le(v: &[u8]) -> Result<String, FromUtf16Error> {
|
||
if v.len() % 2 != 0 {
|
||
return Err(FromUtf16Error(()));
|
||
}
|
||
match (cfg!(target_endian = "little"), unsafe { v.align_to::<u16>() }) {
|
||
(true, ([], v, [])) => Self::from_utf16(v),
|
||
_ => char::decode_utf16(v.array_chunks::<2>().copied().map(u16::from_le_bytes))
|
||
.collect::<Result<_, _>>()
|
||
.map_err(|_| FromUtf16Error(())),
|
||
}
|
||
}
|
||
|
||
/// Decode a UTF-16LE–encoded slice `v` into a `String`, replacing
|
||
/// invalid data with [the replacement character (`U+FFFD`)][U+FFFD].
|
||
///
|
||
/// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`],
|
||
/// `from_utf16le_lossy` returns a `String` since the UTF-16 to UTF-8
|
||
/// conversion requires a memory allocation.
|
||
///
|
||
/// [`from_utf8_lossy`]: String::from_utf8_lossy
|
||
/// [`Cow<'a, str>`]: crate::borrow::Cow "borrow::Cow"
|
||
/// [U+FFFD]: core::char::REPLACEMENT_CHARACTER
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// #![feature(str_from_utf16_endian)]
|
||
/// // 𝄞mus<invalid>ic<invalid>
|
||
/// let v = &[0x34, 0xD8, 0x1E, 0xDD, 0x6d, 0x00, 0x75, 0x00,
|
||
/// 0x73, 0x00, 0x1E, 0xDD, 0x69, 0x00, 0x63, 0x00,
|
||
/// 0x34, 0xD8];
|
||
///
|
||
/// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"),
|
||
/// String::from_utf16le_lossy(v));
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "str_from_utf16_endian", issue = "116258")]
|
||
pub fn from_utf16le_lossy(v: &[u8]) -> String {
|
||
match (cfg!(target_endian = "little"), unsafe { v.align_to::<u16>() }) {
|
||
(true, ([], v, [])) => Self::from_utf16_lossy(v),
|
||
(true, ([], v, [_remainder])) => Self::from_utf16_lossy(v) + "\u{FFFD}",
|
||
_ => {
|
||
let mut iter = v.array_chunks::<2>();
|
||
let string = char::decode_utf16(iter.by_ref().copied().map(u16::from_le_bytes))
|
||
.map(|r| r.unwrap_or(char::REPLACEMENT_CHARACTER))
|
||
.collect();
|
||
if iter.remainder().is_empty() { string } else { string + "\u{FFFD}" }
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Decode a UTF-16BE–encoded vector `v` into a `String`, returning [`Err`]
|
||
/// if `v` contains any invalid data.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// #![feature(str_from_utf16_endian)]
|
||
/// // 𝄞music
|
||
/// let v = &[0xD8, 0x34, 0xDD, 0x1E, 0x00, 0x6d, 0x00, 0x75,
|
||
/// 0x00, 0x73, 0x00, 0x69, 0x00, 0x63];
|
||
/// assert_eq!(String::from("𝄞music"),
|
||
/// String::from_utf16be(v).unwrap());
|
||
///
|
||
/// // 𝄞mu<invalid>ic
|
||
/// let v = &[0xD8, 0x34, 0xDD, 0x1E, 0x00, 0x6d, 0x00, 0x75,
|
||
/// 0xD8, 0x00, 0x00, 0x69, 0x00, 0x63];
|
||
/// assert!(String::from_utf16be(v).is_err());
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "str_from_utf16_endian", issue = "116258")]
|
||
pub fn from_utf16be(v: &[u8]) -> Result<String, FromUtf16Error> {
|
||
if v.len() % 2 != 0 {
|
||
return Err(FromUtf16Error(()));
|
||
}
|
||
match (cfg!(target_endian = "big"), unsafe { v.align_to::<u16>() }) {
|
||
(true, ([], v, [])) => Self::from_utf16(v),
|
||
_ => char::decode_utf16(v.array_chunks::<2>().copied().map(u16::from_be_bytes))
|
||
.collect::<Result<_, _>>()
|
||
.map_err(|_| FromUtf16Error(())),
|
||
}
|
||
}
|
||
|
||
/// Decode a UTF-16BE–encoded slice `v` into a `String`, replacing
|
||
/// invalid data with [the replacement character (`U+FFFD`)][U+FFFD].
|
||
///
|
||
/// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`],
|
||
/// `from_utf16le_lossy` returns a `String` since the UTF-16 to UTF-8
|
||
/// conversion requires a memory allocation.
|
||
///
|
||
/// [`from_utf8_lossy`]: String::from_utf8_lossy
|
||
/// [`Cow<'a, str>`]: crate::borrow::Cow "borrow::Cow"
|
||
/// [U+FFFD]: core::char::REPLACEMENT_CHARACTER
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// #![feature(str_from_utf16_endian)]
|
||
/// // 𝄞mus<invalid>ic<invalid>
|
||
/// let v = &[0xD8, 0x34, 0xDD, 0x1E, 0x00, 0x6d, 0x00, 0x75,
|
||
/// 0x00, 0x73, 0xDD, 0x1E, 0x00, 0x69, 0x00, 0x63,
|
||
/// 0xD8, 0x34];
|
||
///
|
||
/// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"),
|
||
/// String::from_utf16be_lossy(v));
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "str_from_utf16_endian", issue = "116258")]
|
||
pub fn from_utf16be_lossy(v: &[u8]) -> String {
|
||
match (cfg!(target_endian = "big"), unsafe { v.align_to::<u16>() }) {
|
||
(true, ([], v, [])) => Self::from_utf16_lossy(v),
|
||
(true, ([], v, [_remainder])) => Self::from_utf16_lossy(v) + "\u{FFFD}",
|
||
_ => {
|
||
let mut iter = v.array_chunks::<2>();
|
||
let string = char::decode_utf16(iter.by_ref().copied().map(u16::from_be_bytes))
|
||
.map(|r| r.unwrap_or(char::REPLACEMENT_CHARACTER))
|
||
.collect();
|
||
if iter.remainder().is_empty() { string } else { string + "\u{FFFD}" }
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Decomposes a `String` into its raw components: `(pointer, length, capacity)`.
|
||
///
|
||
/// Returns the raw pointer to the underlying data, the length of
|
||
/// the string (in bytes), and the allocated capacity of the data
|
||
/// (in bytes). These are the same arguments in the same order as
|
||
/// the arguments to [`from_raw_parts`].
|
||
///
|
||
/// After calling this function, the caller is responsible for the
|
||
/// memory previously managed by the `String`. The only way to do
|
||
/// this is to convert the raw pointer, length, and capacity back
|
||
/// into a `String` with the [`from_raw_parts`] function, allowing
|
||
/// the destructor to perform the cleanup.
|
||
///
|
||
/// [`from_raw_parts`]: String::from_raw_parts
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(vec_into_raw_parts)]
|
||
/// let s = String::from("hello");
|
||
///
|
||
/// let (ptr, len, cap) = s.into_raw_parts();
|
||
///
|
||
/// let rebuilt = unsafe { String::from_raw_parts(ptr, len, cap) };
|
||
/// assert_eq!(rebuilt, "hello");
|
||
/// ```
|
||
#[must_use = "`self` will be dropped if the result is not used"]
|
||
#[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")]
|
||
pub fn into_raw_parts(self) -> (*mut u8, usize, usize) {
|
||
self.vec.into_raw_parts()
|
||
}
|
||
|
||
/// Creates a new `String` from a pointer, a length and a capacity.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// This is highly unsafe, due to the number of invariants that aren't
|
||
/// checked:
|
||
///
|
||
/// * The memory at `buf` needs to have been previously allocated by the
|
||
/// same allocator the standard library uses, with a required alignment of exactly 1.
|
||
/// * `length` needs to be less than or equal to `capacity`.
|
||
/// * `capacity` needs to be the correct value.
|
||
/// * The first `length` bytes at `buf` need to be valid UTF-8.
|
||
///
|
||
/// Violating these may cause problems like corrupting the allocator's
|
||
/// internal data structures. For example, it is normally **not** safe to
|
||
/// build a `String` from a pointer to a C `char` array containing UTF-8
|
||
/// _unless_ you are certain that array was originally allocated by the
|
||
/// Rust standard library's allocator.
|
||
///
|
||
/// The ownership of `buf` is effectively transferred to the
|
||
/// `String` which may then deallocate, reallocate or change the
|
||
/// contents of memory pointed to by the pointer at will. Ensure
|
||
/// that nothing else uses the pointer after calling this
|
||
/// function.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::mem;
|
||
///
|
||
/// unsafe {
|
||
/// let s = String::from("hello");
|
||
///
|
||
// FIXME Update this when vec_into_raw_parts is stabilized
|
||
/// // Prevent automatically dropping the String's data
|
||
/// let mut s = mem::ManuallyDrop::new(s);
|
||
///
|
||
/// let ptr = s.as_mut_ptr();
|
||
/// let len = s.len();
|
||
/// let capacity = s.capacity();
|
||
///
|
||
/// let s = String::from_raw_parts(ptr, len, capacity);
|
||
///
|
||
/// assert_eq!(String::from("hello"), s);
|
||
/// }
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub unsafe fn from_raw_parts(buf: *mut u8, length: usize, capacity: usize) -> String {
|
||
unsafe { String { vec: Vec::from_raw_parts(buf, length, capacity) } }
|
||
}
|
||
|
||
/// Converts a vector of bytes to a `String` without checking that the
|
||
/// string contains valid UTF-8.
|
||
///
|
||
/// See the safe version, [`from_utf8`], for more details.
|
||
///
|
||
/// [`from_utf8`]: String::from_utf8
|
||
///
|
||
/// # 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, it may cause
|
||
/// memory unsafety issues with future users of the `String`, as the rest of
|
||
/// the standard library assumes that `String`s are valid UTF-8.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // some bytes, in a vector
|
||
/// let sparkle_heart = vec![240, 159, 146, 150];
|
||
///
|
||
/// let sparkle_heart = unsafe {
|
||
/// String::from_utf8_unchecked(sparkle_heart)
|
||
/// };
|
||
///
|
||
/// assert_eq!("💖", sparkle_heart);
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub unsafe fn from_utf8_unchecked(bytes: Vec<u8>) -> String {
|
||
String { vec: bytes }
|
||
}
|
||
|
||
/// Converts a `String` into a byte vector.
|
||
///
|
||
/// This consumes the `String`, so we do not need to copy its contents.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s = String::from("hello");
|
||
/// let bytes = s.into_bytes();
|
||
///
|
||
/// assert_eq!(&[104, 101, 108, 108, 111][..], &bytes[..]);
|
||
/// ```
|
||
#[inline]
|
||
#[must_use = "`self` will be dropped if the result is not used"]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn into_bytes(self) -> Vec<u8> {
|
||
self.vec
|
||
}
|
||
|
||
/// Extracts a string slice containing the entire `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s = String::from("foo");
|
||
///
|
||
/// assert_eq!("foo", s.as_str());
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "string_as_str", since = "1.7.0")]
|
||
pub fn as_str(&self) -> &str {
|
||
self
|
||
}
|
||
|
||
/// Converts a `String` into a mutable string slice.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("foobar");
|
||
/// let s_mut_str = s.as_mut_str();
|
||
///
|
||
/// s_mut_str.make_ascii_uppercase();
|
||
///
|
||
/// assert_eq!("FOOBAR", s_mut_str);
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "string_as_str", since = "1.7.0")]
|
||
pub fn as_mut_str(&mut self) -> &mut str {
|
||
self
|
||
}
|
||
|
||
/// Appends a given string slice onto the end of this `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("foo");
|
||
///
|
||
/// s.push_str("bar");
|
||
///
|
||
/// assert_eq!("foobar", s);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[rustc_confusables("append", "push")]
|
||
pub fn push_str(&mut self, string: &str) {
|
||
self.vec.extend_from_slice(string.as_bytes())
|
||
}
|
||
|
||
/// Copies elements from `src` range to the end of the string.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the starting point or end point do not lie on a [`char`]
|
||
/// boundary, or if they're out of bounds.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(string_extend_from_within)]
|
||
/// let mut string = String::from("abcde");
|
||
///
|
||
/// string.extend_from_within(2..);
|
||
/// assert_eq!(string, "abcdecde");
|
||
///
|
||
/// string.extend_from_within(..2);
|
||
/// assert_eq!(string, "abcdecdeab");
|
||
///
|
||
/// string.extend_from_within(4..8);
|
||
/// assert_eq!(string, "abcdecdeabecde");
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "string_extend_from_within", issue = "103806")]
|
||
pub fn extend_from_within<R>(&mut self, src: R)
|
||
where
|
||
R: RangeBounds<usize>,
|
||
{
|
||
let src @ Range { start, end } = slice::range(src, ..self.len());
|
||
|
||
assert!(self.is_char_boundary(start));
|
||
assert!(self.is_char_boundary(end));
|
||
|
||
self.vec.extend_from_within(src);
|
||
}
|
||
|
||
/// Returns this `String`'s capacity, in bytes.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s = String::with_capacity(10);
|
||
///
|
||
/// assert!(s.capacity() >= 10);
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn capacity(&self) -> usize {
|
||
self.vec.capacity()
|
||
}
|
||
|
||
/// Reserves capacity for at least `additional` bytes more than the
|
||
/// current length. The allocator may reserve more space to speculatively
|
||
/// avoid frequent allocations. After calling `reserve`,
|
||
/// capacity will be greater than or equal to `self.len() + additional`.
|
||
/// Does nothing if capacity is already sufficient.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the new capacity overflows [`usize`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// let mut s = String::new();
|
||
///
|
||
/// s.reserve(10);
|
||
///
|
||
/// assert!(s.capacity() >= 10);
|
||
/// ```
|
||
///
|
||
/// This might not actually increase the capacity:
|
||
///
|
||
/// ```
|
||
/// let mut s = String::with_capacity(10);
|
||
/// s.push('a');
|
||
/// s.push('b');
|
||
///
|
||
/// // s now has a length of 2 and a capacity of at least 10
|
||
/// let capacity = s.capacity();
|
||
/// assert_eq!(2, s.len());
|
||
/// assert!(capacity >= 10);
|
||
///
|
||
/// // Since we already have at least an extra 8 capacity, calling this...
|
||
/// s.reserve(8);
|
||
///
|
||
/// // ... doesn't actually increase.
|
||
/// assert_eq!(capacity, s.capacity());
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn reserve(&mut self, additional: usize) {
|
||
self.vec.reserve(additional)
|
||
}
|
||
|
||
/// Reserves the minimum capacity for at least `additional` bytes more than
|
||
/// the current length. Unlike [`reserve`], this will not
|
||
/// deliberately over-allocate to speculatively avoid frequent allocations.
|
||
/// After calling `reserve_exact`, capacity will be greater than or equal to
|
||
/// `self.len() + additional`. Does nothing if the capacity is already
|
||
/// sufficient.
|
||
///
|
||
/// [`reserve`]: String::reserve
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the new capacity overflows [`usize`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// let mut s = String::new();
|
||
///
|
||
/// s.reserve_exact(10);
|
||
///
|
||
/// assert!(s.capacity() >= 10);
|
||
/// ```
|
||
///
|
||
/// This might not actually increase the capacity:
|
||
///
|
||
/// ```
|
||
/// let mut s = String::with_capacity(10);
|
||
/// s.push('a');
|
||
/// s.push('b');
|
||
///
|
||
/// // s now has a length of 2 and a capacity of at least 10
|
||
/// let capacity = s.capacity();
|
||
/// assert_eq!(2, s.len());
|
||
/// assert!(capacity >= 10);
|
||
///
|
||
/// // Since we already have at least an extra 8 capacity, calling this...
|
||
/// s.reserve_exact(8);
|
||
///
|
||
/// // ... doesn't actually increase.
|
||
/// assert_eq!(capacity, s.capacity());
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn reserve_exact(&mut self, additional: usize) {
|
||
self.vec.reserve_exact(additional)
|
||
}
|
||
|
||
/// Tries to reserve capacity for at least `additional` bytes more than the
|
||
/// current length. The allocator may reserve more space to speculatively
|
||
/// avoid frequent allocations. After calling `try_reserve`, capacity will be
|
||
/// greater than or equal to `self.len() + additional` if it returns
|
||
/// `Ok(())`. Does nothing if capacity is already sufficient. This method
|
||
/// preserves the contents even if an error occurs.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// If the capacity overflows, or the allocator reports a failure, then an error
|
||
/// is returned.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::collections::TryReserveError;
|
||
///
|
||
/// fn process_data(data: &str) -> Result<String, TryReserveError> {
|
||
/// let mut output = String::new();
|
||
///
|
||
/// // Pre-reserve the memory, exiting if we can't
|
||
/// output.try_reserve(data.len())?;
|
||
///
|
||
/// // Now we know this can't OOM in the middle of our complex work
|
||
/// output.push_str(data);
|
||
///
|
||
/// Ok(output)
|
||
/// }
|
||
/// # process_data("rust").expect("why is the test harness OOMing on 4 bytes?");
|
||
/// ```
|
||
#[stable(feature = "try_reserve", since = "1.57.0")]
|
||
pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
|
||
self.vec.try_reserve(additional)
|
||
}
|
||
|
||
/// Tries to reserve the minimum capacity for at least `additional` bytes
|
||
/// more than the current length. Unlike [`try_reserve`], this will not
|
||
/// deliberately over-allocate to speculatively avoid frequent allocations.
|
||
/// After calling `try_reserve_exact`, capacity will be greater than or
|
||
/// equal to `self.len() + additional` if it returns `Ok(())`.
|
||
/// Does nothing if the capacity is already sufficient.
|
||
///
|
||
/// Note that the allocator may give the collection more space than it
|
||
/// requests. Therefore, capacity can not be relied upon to be precisely
|
||
/// minimal. Prefer [`try_reserve`] if future insertions are expected.
|
||
///
|
||
/// [`try_reserve`]: String::try_reserve
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// If the capacity overflows, or the allocator reports a failure, then an error
|
||
/// is returned.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::collections::TryReserveError;
|
||
///
|
||
/// fn process_data(data: &str) -> Result<String, TryReserveError> {
|
||
/// let mut output = String::new();
|
||
///
|
||
/// // Pre-reserve the memory, exiting if we can't
|
||
/// output.try_reserve_exact(data.len())?;
|
||
///
|
||
/// // Now we know this can't OOM in the middle of our complex work
|
||
/// output.push_str(data);
|
||
///
|
||
/// Ok(output)
|
||
/// }
|
||
/// # process_data("rust").expect("why is the test harness OOMing on 4 bytes?");
|
||
/// ```
|
||
#[stable(feature = "try_reserve", since = "1.57.0")]
|
||
pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> {
|
||
self.vec.try_reserve_exact(additional)
|
||
}
|
||
|
||
/// Shrinks the capacity of this `String` to match its length.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("foo");
|
||
///
|
||
/// s.reserve(100);
|
||
/// assert!(s.capacity() >= 100);
|
||
///
|
||
/// s.shrink_to_fit();
|
||
/// assert_eq!(3, s.capacity());
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn shrink_to_fit(&mut self) {
|
||
self.vec.shrink_to_fit()
|
||
}
|
||
|
||
/// Shrinks the capacity of this `String` with a lower bound.
|
||
///
|
||
/// The capacity will remain at least as large as both the length
|
||
/// and the supplied value.
|
||
///
|
||
/// If the current capacity is less than the lower limit, this is a no-op.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("foo");
|
||
///
|
||
/// s.reserve(100);
|
||
/// assert!(s.capacity() >= 100);
|
||
///
|
||
/// s.shrink_to(10);
|
||
/// assert!(s.capacity() >= 10);
|
||
/// s.shrink_to(0);
|
||
/// assert!(s.capacity() >= 3);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "shrink_to", since = "1.56.0")]
|
||
pub fn shrink_to(&mut self, min_capacity: usize) {
|
||
self.vec.shrink_to(min_capacity)
|
||
}
|
||
|
||
/// Appends the given [`char`] to the end of this `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("abc");
|
||
///
|
||
/// s.push('1');
|
||
/// s.push('2');
|
||
/// s.push('3');
|
||
///
|
||
/// assert_eq!("abc123", s);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn push(&mut self, ch: char) {
|
||
match ch.len_utf8() {
|
||
1 => self.vec.push(ch as u8),
|
||
_ => self.vec.extend_from_slice(ch.encode_utf8(&mut [0; 4]).as_bytes()),
|
||
}
|
||
}
|
||
|
||
/// Returns a byte slice of this `String`'s contents.
|
||
///
|
||
/// The inverse of this method is [`from_utf8`].
|
||
///
|
||
/// [`from_utf8`]: String::from_utf8
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s = String::from("hello");
|
||
///
|
||
/// assert_eq!(&[104, 101, 108, 108, 111], s.as_bytes());
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn as_bytes(&self) -> &[u8] {
|
||
&self.vec
|
||
}
|
||
|
||
/// Shortens this `String` to the specified length.
|
||
///
|
||
/// If `new_len` is greater than or equal to the string's current length, this has no
|
||
/// effect.
|
||
///
|
||
/// Note that this method has no effect on the allocated capacity
|
||
/// of the string
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if `new_len` does not lie on a [`char`] boundary.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("hello");
|
||
///
|
||
/// s.truncate(2);
|
||
///
|
||
/// assert_eq!("he", s);
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn truncate(&mut self, new_len: usize) {
|
||
if new_len <= self.len() {
|
||
assert!(self.is_char_boundary(new_len));
|
||
self.vec.truncate(new_len)
|
||
}
|
||
}
|
||
|
||
/// Removes the last character from the string buffer and returns it.
|
||
///
|
||
/// Returns [`None`] if this `String` is empty.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("abč");
|
||
///
|
||
/// assert_eq!(s.pop(), Some('č'));
|
||
/// assert_eq!(s.pop(), Some('b'));
|
||
/// assert_eq!(s.pop(), Some('a'));
|
||
///
|
||
/// assert_eq!(s.pop(), None);
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn pop(&mut self) -> Option<char> {
|
||
let ch = self.chars().rev().next()?;
|
||
let newlen = self.len() - ch.len_utf8();
|
||
unsafe {
|
||
self.vec.set_len(newlen);
|
||
}
|
||
Some(ch)
|
||
}
|
||
|
||
/// Removes a [`char`] from this `String` at a byte position and returns it.
|
||
///
|
||
/// This is an *O*(*n*) operation, as it requires copying every element in the
|
||
/// buffer.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if `idx` is larger than or equal to the `String`'s length,
|
||
/// or if it does not lie on a [`char`] boundary.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("abç");
|
||
///
|
||
/// assert_eq!(s.remove(0), 'a');
|
||
/// assert_eq!(s.remove(1), 'ç');
|
||
/// assert_eq!(s.remove(0), 'b');
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[rustc_confusables("delete", "take")]
|
||
pub fn remove(&mut self, idx: usize) -> char {
|
||
let ch = match self[idx..].chars().next() {
|
||
Some(ch) => ch,
|
||
None => panic!("cannot remove a char from the end of a string"),
|
||
};
|
||
|
||
let next = idx + ch.len_utf8();
|
||
let len = self.len();
|
||
unsafe {
|
||
ptr::copy(self.vec.as_ptr().add(next), self.vec.as_mut_ptr().add(idx), len - next);
|
||
self.vec.set_len(len - (next - idx));
|
||
}
|
||
ch
|
||
}
|
||
|
||
/// Remove all matches of pattern `pat` in the `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(string_remove_matches)]
|
||
/// let mut s = String::from("Trees are not green, the sky is not blue.");
|
||
/// s.remove_matches("not ");
|
||
/// assert_eq!("Trees are green, the sky is blue.", s);
|
||
/// ```
|
||
///
|
||
/// Matches will be detected and removed iteratively, so in cases where
|
||
/// patterns overlap, only the first pattern will be removed:
|
||
///
|
||
/// ```
|
||
/// #![feature(string_remove_matches)]
|
||
/// let mut s = String::from("banana");
|
||
/// s.remove_matches("ana");
|
||
/// assert_eq!("bna", s);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "string_remove_matches", reason = "new API", issue = "72826")]
|
||
pub fn remove_matches<'a, P>(&'a mut self, pat: P)
|
||
where
|
||
P: for<'x> Pattern<'x>,
|
||
{
|
||
use core::str::pattern::Searcher;
|
||
|
||
let rejections = {
|
||
let mut searcher = pat.into_searcher(self);
|
||
// Per Searcher::next:
|
||
//
|
||
// A Match result needs to contain the whole matched pattern,
|
||
// however Reject results may be split up into arbitrary many
|
||
// adjacent fragments. Both ranges may have zero length.
|
||
//
|
||
// In practice the implementation of Searcher::next_match tends to
|
||
// be more efficient, so we use it here and do some work to invert
|
||
// matches into rejections since that's what we want to copy below.
|
||
let mut front = 0;
|
||
let rejections: Vec<_> = from_fn(|| {
|
||
let (start, end) = searcher.next_match()?;
|
||
let prev_front = front;
|
||
front = end;
|
||
Some((prev_front, start))
|
||
})
|
||
.collect();
|
||
rejections.into_iter().chain(core::iter::once((front, self.len())))
|
||
};
|
||
|
||
let mut len = 0;
|
||
let ptr = self.vec.as_mut_ptr();
|
||
|
||
for (start, end) in rejections {
|
||
let count = end - start;
|
||
if start != len {
|
||
// SAFETY: per Searcher::next:
|
||
//
|
||
// The stream of Match and Reject values up to a Done will
|
||
// contain index ranges that are adjacent, non-overlapping,
|
||
// covering the whole haystack, and laying on utf8
|
||
// boundaries.
|
||
unsafe {
|
||
ptr::copy(ptr.add(start), ptr.add(len), count);
|
||
}
|
||
}
|
||
len += count;
|
||
}
|
||
|
||
unsafe {
|
||
self.vec.set_len(len);
|
||
}
|
||
}
|
||
|
||
/// Retains only the characters specified by the predicate.
|
||
///
|
||
/// In other words, remove all characters `c` such that `f(c)` returns `false`.
|
||
/// This method operates in place, visiting each character exactly once in the
|
||
/// original order, and preserves the order of the retained characters.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("f_o_ob_ar");
|
||
///
|
||
/// s.retain(|c| c != '_');
|
||
///
|
||
/// assert_eq!(s, "foobar");
|
||
/// ```
|
||
///
|
||
/// Because the elements are visited exactly once in the original order,
|
||
/// external state may be used to decide which elements to keep.
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("abcde");
|
||
/// let keep = [false, true, true, false, true];
|
||
/// let mut iter = keep.iter();
|
||
/// s.retain(|_| *iter.next().unwrap());
|
||
/// assert_eq!(s, "bce");
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "string_retain", since = "1.26.0")]
|
||
pub fn retain<F>(&mut self, mut f: F)
|
||
where
|
||
F: FnMut(char) -> bool,
|
||
{
|
||
struct SetLenOnDrop<'a> {
|
||
s: &'a mut String,
|
||
idx: usize,
|
||
del_bytes: usize,
|
||
}
|
||
|
||
impl<'a> Drop for SetLenOnDrop<'a> {
|
||
fn drop(&mut self) {
|
||
let new_len = self.idx - self.del_bytes;
|
||
debug_assert!(new_len <= self.s.len());
|
||
unsafe { self.s.vec.set_len(new_len) };
|
||
}
|
||
}
|
||
|
||
let len = self.len();
|
||
let mut guard = SetLenOnDrop { s: self, idx: 0, del_bytes: 0 };
|
||
|
||
while guard.idx < len {
|
||
let ch =
|
||
// SAFETY: `guard.idx` is positive-or-zero and less that len so the `get_unchecked`
|
||
// is in bound. `self` is valid UTF-8 like string and the returned slice starts at
|
||
// a unicode code point so the `Chars` always return one character.
|
||
unsafe { guard.s.get_unchecked(guard.idx..len).chars().next().unwrap_unchecked() };
|
||
let ch_len = ch.len_utf8();
|
||
|
||
if !f(ch) {
|
||
guard.del_bytes += ch_len;
|
||
} else if guard.del_bytes > 0 {
|
||
// SAFETY: `guard.idx` is in bound and `guard.del_bytes` represent the number of
|
||
// bytes that are erased from the string so the resulting `guard.idx -
|
||
// guard.del_bytes` always represent a valid unicode code point.
|
||
//
|
||
// `guard.del_bytes` >= `ch.len_utf8()`, so taking a slice with `ch.len_utf8()` len
|
||
// is safe.
|
||
ch.encode_utf8(unsafe {
|
||
crate::slice::from_raw_parts_mut(
|
||
guard.s.as_mut_ptr().add(guard.idx - guard.del_bytes),
|
||
ch.len_utf8(),
|
||
)
|
||
});
|
||
}
|
||
|
||
// Point idx to the next char
|
||
guard.idx += ch_len;
|
||
}
|
||
|
||
drop(guard);
|
||
}
|
||
|
||
/// Inserts a character into this `String` at a byte position.
|
||
///
|
||
/// This is an *O*(*n*) operation as it requires copying every element in the
|
||
/// buffer.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if `idx` is larger than the `String`'s length, or if it does not
|
||
/// lie on a [`char`] boundary.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::with_capacity(3);
|
||
///
|
||
/// s.insert(0, 'f');
|
||
/// s.insert(1, 'o');
|
||
/// s.insert(2, 'o');
|
||
///
|
||
/// assert_eq!("foo", s);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[rustc_confusables("set")]
|
||
pub fn insert(&mut self, idx: usize, ch: char) {
|
||
assert!(self.is_char_boundary(idx));
|
||
let mut bits = [0; 4];
|
||
let bits = ch.encode_utf8(&mut bits).as_bytes();
|
||
|
||
unsafe {
|
||
self.insert_bytes(idx, bits);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
unsafe fn insert_bytes(&mut self, idx: usize, bytes: &[u8]) {
|
||
let len = self.len();
|
||
let amt = bytes.len();
|
||
self.vec.reserve(amt);
|
||
|
||
unsafe {
|
||
ptr::copy(self.vec.as_ptr().add(idx), self.vec.as_mut_ptr().add(idx + amt), len - idx);
|
||
ptr::copy_nonoverlapping(bytes.as_ptr(), self.vec.as_mut_ptr().add(idx), amt);
|
||
self.vec.set_len(len + amt);
|
||
}
|
||
}
|
||
|
||
/// Inserts a string slice into this `String` at a byte position.
|
||
///
|
||
/// This is an *O*(*n*) operation as it requires copying every element in the
|
||
/// buffer.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if `idx` is larger than the `String`'s length, or if it does not
|
||
/// lie on a [`char`] boundary.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("bar");
|
||
///
|
||
/// s.insert_str(0, "foo");
|
||
///
|
||
/// assert_eq!("foobar", s);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "insert_str", since = "1.16.0")]
|
||
pub fn insert_str(&mut self, idx: usize, string: &str) {
|
||
assert!(self.is_char_boundary(idx));
|
||
|
||
unsafe {
|
||
self.insert_bytes(idx, string.as_bytes());
|
||
}
|
||
}
|
||
|
||
/// Returns a mutable reference to the contents of this `String`.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// This function is unsafe because the returned `&mut Vec` allows writing
|
||
/// bytes which are not valid UTF-8. If this constraint is violated, using
|
||
/// the original `String` after dropping the `&mut Vec` may violate memory
|
||
/// safety, as the rest of the standard library assumes that `String`s are
|
||
/// valid UTF-8.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("hello");
|
||
///
|
||
/// unsafe {
|
||
/// let vec = s.as_mut_vec();
|
||
/// assert_eq!(&[104, 101, 108, 108, 111][..], &vec[..]);
|
||
///
|
||
/// vec.reverse();
|
||
/// }
|
||
/// assert_eq!(s, "olleh");
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8> {
|
||
&mut self.vec
|
||
}
|
||
|
||
/// Returns the length of this `String`, in bytes, not [`char`]s or
|
||
/// graphemes. In other words, it might not be what a human considers the
|
||
/// length of the string.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let a = String::from("foo");
|
||
/// assert_eq!(a.len(), 3);
|
||
///
|
||
/// let fancy_f = String::from("ƒoo");
|
||
/// assert_eq!(fancy_f.len(), 4);
|
||
/// assert_eq!(fancy_f.chars().count(), 3);
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[rustc_confusables("length", "size")]
|
||
pub fn len(&self) -> usize {
|
||
self.vec.len()
|
||
}
|
||
|
||
/// Returns `true` if this `String` has a length of zero, and `false` otherwise.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut v = String::new();
|
||
/// assert!(v.is_empty());
|
||
///
|
||
/// v.push('a');
|
||
/// assert!(!v.is_empty());
|
||
/// ```
|
||
#[inline]
|
||
#[must_use]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn is_empty(&self) -> bool {
|
||
self.len() == 0
|
||
}
|
||
|
||
/// Splits the string into two at the given byte index.
|
||
///
|
||
/// Returns a newly allocated `String`. `self` contains bytes `[0, at)`, and
|
||
/// the returned `String` contains bytes `[at, len)`. `at` must be on the
|
||
/// boundary of a UTF-8 code point.
|
||
///
|
||
/// Note that the capacity of `self` does not change.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if `at` is not on a `UTF-8` code point boundary, or if it is beyond the last
|
||
/// code point of the string.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// # fn main() {
|
||
/// let mut hello = String::from("Hello, World!");
|
||
/// let world = hello.split_off(7);
|
||
/// assert_eq!(hello, "Hello, ");
|
||
/// assert_eq!(world, "World!");
|
||
/// # }
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "string_split_off", since = "1.16.0")]
|
||
#[must_use = "use `.truncate()` if you don't need the other half"]
|
||
pub fn split_off(&mut self, at: usize) -> String {
|
||
assert!(self.is_char_boundary(at));
|
||
let other = self.vec.split_off(at);
|
||
unsafe { String::from_utf8_unchecked(other) }
|
||
}
|
||
|
||
/// Truncates this `String`, removing all contents.
|
||
///
|
||
/// While this means the `String` will have a length of zero, it does not
|
||
/// touch its capacity.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("foo");
|
||
///
|
||
/// s.clear();
|
||
///
|
||
/// assert!(s.is_empty());
|
||
/// assert_eq!(0, s.len());
|
||
/// assert_eq!(3, s.capacity());
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn clear(&mut self) {
|
||
self.vec.clear()
|
||
}
|
||
|
||
/// Removes the specified range from the string in bulk, returning all
|
||
/// removed characters as an iterator.
|
||
///
|
||
/// The returned iterator keeps a mutable borrow on the string to optimize
|
||
/// its implementation.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the starting point or end point do not lie on a [`char`]
|
||
/// boundary, or if they're out of bounds.
|
||
///
|
||
/// # Leaking
|
||
///
|
||
/// If the returned iterator goes out of scope without being dropped (due to
|
||
/// [`core::mem::forget`], for example), the string may still contain a copy
|
||
/// of any drained characters, or may have lost characters arbitrarily,
|
||
/// including characters outside the range.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("α is alpha, β is beta");
|
||
/// let beta_offset = s.find('β').unwrap_or(s.len());
|
||
///
|
||
/// // Remove the range up until the β from the string
|
||
/// let t: String = s.drain(..beta_offset).collect();
|
||
/// assert_eq!(t, "α is alpha, ");
|
||
/// assert_eq!(s, "β is beta");
|
||
///
|
||
/// // A full range clears the string, like `clear()` does
|
||
/// s.drain(..);
|
||
/// assert_eq!(s, "");
|
||
/// ```
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
pub fn drain<R>(&mut self, range: R) -> Drain<'_>
|
||
where
|
||
R: RangeBounds<usize>,
|
||
{
|
||
// Memory safety
|
||
//
|
||
// The String version of Drain does not have the memory safety issues
|
||
// of the vector version. The data is just plain bytes.
|
||
// Because the range removal happens in Drop, if the Drain iterator is leaked,
|
||
// the removal will not happen.
|
||
let Range { start, end } = slice::range(range, ..self.len());
|
||
assert!(self.is_char_boundary(start));
|
||
assert!(self.is_char_boundary(end));
|
||
|
||
// Take out two simultaneous borrows. The &mut String won't be accessed
|
||
// until iteration is over, in Drop.
|
||
let self_ptr = self as *mut _;
|
||
// SAFETY: `slice::range` and `is_char_boundary` do the appropriate bounds checks.
|
||
let chars_iter = unsafe { self.get_unchecked(start..end) }.chars();
|
||
|
||
Drain { start, end, iter: chars_iter, string: self_ptr }
|
||
}
|
||
|
||
/// Removes the specified range in the string,
|
||
/// and replaces it with the given string.
|
||
/// The given string doesn't need to be the same length as the range.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the starting point or end point do not lie on a [`char`]
|
||
/// boundary, or if they're out of bounds.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("α is alpha, β is beta");
|
||
/// let beta_offset = s.find('β').unwrap_or(s.len());
|
||
///
|
||
/// // Replace the range up until the β from the string
|
||
/// s.replace_range(..beta_offset, "Α is capital alpha; ");
|
||
/// assert_eq!(s, "Α is capital alpha; β is beta");
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "splice", since = "1.27.0")]
|
||
pub fn replace_range<R>(&mut self, range: R, replace_with: &str)
|
||
where
|
||
R: RangeBounds<usize>,
|
||
{
|
||
// Memory safety
|
||
//
|
||
// Replace_range does not have the memory safety issues of a vector Splice.
|
||
// of the vector version. The data is just plain bytes.
|
||
|
||
// WARNING: Inlining this variable would be unsound (#81138)
|
||
let start = range.start_bound();
|
||
match start {
|
||
Included(&n) => assert!(self.is_char_boundary(n)),
|
||
Excluded(&n) => assert!(self.is_char_boundary(n + 1)),
|
||
Unbounded => {}
|
||
};
|
||
// WARNING: Inlining this variable would be unsound (#81138)
|
||
let end = range.end_bound();
|
||
match end {
|
||
Included(&n) => assert!(self.is_char_boundary(n + 1)),
|
||
Excluded(&n) => assert!(self.is_char_boundary(n)),
|
||
Unbounded => {}
|
||
};
|
||
|
||
// Using `range` again would be unsound (#81138)
|
||
// We assume the bounds reported by `range` remain the same, but
|
||
// an adversarial implementation could change between calls
|
||
unsafe { self.as_mut_vec() }.splice((start, end), replace_with.bytes());
|
||
}
|
||
|
||
/// Converts this `String` into a <code>[Box]<[str]></code>.
|
||
///
|
||
/// Before doing the conversion, this method discards excess capacity like [`shrink_to_fit`].
|
||
/// Note that this call may reallocate and copy the bytes of the string.
|
||
///
|
||
/// [`shrink_to_fit`]: String::shrink_to_fit
|
||
/// [str]: prim@str "str"
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s = String::from("hello");
|
||
///
|
||
/// let b = s.into_boxed_str();
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_str", since = "1.4.0")]
|
||
#[must_use = "`self` will be dropped if the result is not used"]
|
||
#[inline]
|
||
pub fn into_boxed_str(self) -> Box<str> {
|
||
let slice = self.vec.into_boxed_slice();
|
||
unsafe { from_boxed_utf8_unchecked(slice) }
|
||
}
|
||
|
||
/// Consumes and leaks the `String`, returning a mutable reference to the contents,
|
||
/// `&'a mut str`.
|
||
///
|
||
/// The caller has free choice over the returned lifetime, including `'static`. Indeed,
|
||
/// this function is ideally used for data that lives for the remainder of the program's life,
|
||
/// as dropping the returned reference will cause a memory leak.
|
||
///
|
||
/// It does not reallocate or shrink the `String`, so the leaked allocation may include unused
|
||
/// capacity that is not part of the returned slice. If you want to discard excess capacity,
|
||
/// call [`into_boxed_str`], and then [`Box::leak`] instead. However, keep in mind that
|
||
/// trimming the capacity may result in a reallocation and copy.
|
||
///
|
||
/// [`into_boxed_str`]: Self::into_boxed_str
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let x = String::from("bucket");
|
||
/// let static_ref: &'static mut str = x.leak();
|
||
/// assert_eq!(static_ref, "bucket");
|
||
/// ```
|
||
#[stable(feature = "string_leak", since = "1.72.0")]
|
||
#[inline]
|
||
pub fn leak<'a>(self) -> &'a mut str {
|
||
let slice = self.vec.leak();
|
||
unsafe { from_utf8_unchecked_mut(slice) }
|
||
}
|
||
}
|
||
|
||
impl FromUtf8Error {
|
||
/// Returns a slice of [`u8`]s bytes that were attempted to convert to a `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // some invalid bytes, in a vector
|
||
/// let bytes = vec![0, 159];
|
||
///
|
||
/// let value = String::from_utf8(bytes);
|
||
///
|
||
/// assert_eq!(&[0, 159], value.unwrap_err().as_bytes());
|
||
/// ```
|
||
#[must_use]
|
||
#[stable(feature = "from_utf8_error_as_bytes", since = "1.26.0")]
|
||
pub fn as_bytes(&self) -> &[u8] {
|
||
&self.bytes[..]
|
||
}
|
||
|
||
/// Returns the bytes that were attempted to convert to a `String`.
|
||
///
|
||
/// This method is carefully constructed to avoid allocation. It will
|
||
/// consume the error, moving out the bytes, so that a copy of the bytes
|
||
/// does not need to be made.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // some invalid bytes, in a vector
|
||
/// let bytes = vec![0, 159];
|
||
///
|
||
/// let value = String::from_utf8(bytes);
|
||
///
|
||
/// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes());
|
||
/// ```
|
||
#[must_use = "`self` will be dropped if the result is not used"]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn into_bytes(self) -> Vec<u8> {
|
||
self.bytes
|
||
}
|
||
|
||
/// Fetch a `Utf8Error` to get more details about the conversion failure.
|
||
///
|
||
/// The [`Utf8Error`] type provided by [`std::str`] represents an error that may
|
||
/// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's
|
||
/// an analogue to `FromUtf8Error`. See its documentation for more details
|
||
/// on using it.
|
||
///
|
||
/// [`std::str`]: core::str "std::str"
|
||
/// [`&str`]: prim@str "&str"
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // some invalid bytes, in a vector
|
||
/// let bytes = vec![0, 159];
|
||
///
|
||
/// let error = String::from_utf8(bytes).unwrap_err().utf8_error();
|
||
///
|
||
/// // the first byte is invalid here
|
||
/// assert_eq!(1, error.valid_up_to());
|
||
/// ```
|
||
#[must_use]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn utf8_error(&self) -> Utf8Error {
|
||
self.error
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl fmt::Display for FromUtf8Error {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Display::fmt(&self.error, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl fmt::Display for FromUtf16Error {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Display::fmt("invalid utf-16: lone surrogate found", f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Error for FromUtf8Error {
|
||
#[allow(deprecated)]
|
||
fn description(&self) -> &str {
|
||
"invalid utf-8"
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Error for FromUtf16Error {
|
||
#[allow(deprecated)]
|
||
fn description(&self) -> &str {
|
||
"invalid utf-16"
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Clone for String {
|
||
fn clone(&self) -> Self {
|
||
String { vec: self.vec.clone() }
|
||
}
|
||
|
||
/// Clones the contents of `source` into `self`.
|
||
///
|
||
/// This method is preferred over simply assigning `source.clone()` to `self`,
|
||
/// as it avoids reallocation if possible.
|
||
fn clone_from(&mut self, source: &Self) {
|
||
self.vec.clone_from(&source.vec);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl FromIterator<char> for String {
|
||
fn from_iter<I: IntoIterator<Item = char>>(iter: I) -> String {
|
||
let mut buf = String::new();
|
||
buf.extend(iter);
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "string_from_iter_by_ref", since = "1.17.0")]
|
||
impl<'a> FromIterator<&'a char> for String {
|
||
fn from_iter<I: IntoIterator<Item = &'a char>>(iter: I) -> String {
|
||
let mut buf = String::new();
|
||
buf.extend(iter);
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a> FromIterator<&'a str> for String {
|
||
fn from_iter<I: IntoIterator<Item = &'a str>>(iter: I) -> String {
|
||
let mut buf = String::new();
|
||
buf.extend(iter);
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "extend_string", since = "1.4.0")]
|
||
impl FromIterator<String> for String {
|
||
fn from_iter<I: IntoIterator<Item = String>>(iter: I) -> String {
|
||
let mut iterator = iter.into_iter();
|
||
|
||
// Because we're iterating over `String`s, we can avoid at least
|
||
// one allocation by getting the first string from the iterator
|
||
// and appending to it all the subsequent strings.
|
||
match iterator.next() {
|
||
None => String::new(),
|
||
Some(mut buf) => {
|
||
buf.extend(iterator);
|
||
buf
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_str2", since = "1.45.0")]
|
||
impl<A: Allocator> FromIterator<Box<str, A>> for String {
|
||
fn from_iter<I: IntoIterator<Item = Box<str, A>>>(iter: I) -> String {
|
||
let mut buf = String::new();
|
||
buf.extend(iter);
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "herd_cows", since = "1.19.0")]
|
||
impl<'a> FromIterator<Cow<'a, str>> for String {
|
||
fn from_iter<I: IntoIterator<Item = Cow<'a, str>>>(iter: I) -> String {
|
||
let mut iterator = iter.into_iter();
|
||
|
||
// Because we're iterating over CoWs, we can (potentially) avoid at least
|
||
// one allocation by getting the first item and appending to it all the
|
||
// subsequent items.
|
||
match iterator.next() {
|
||
None => String::new(),
|
||
Some(cow) => {
|
||
let mut buf = cow.into_owned();
|
||
buf.extend(iterator);
|
||
buf
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Extend<char> for String {
|
||
fn extend<I: IntoIterator<Item = char>>(&mut self, iter: I) {
|
||
let iterator = iter.into_iter();
|
||
let (lower_bound, _) = iterator.size_hint();
|
||
self.reserve(lower_bound);
|
||
iterator.for_each(move |c| self.push(c));
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_one(&mut self, c: char) {
|
||
self.push(c);
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_reserve(&mut self, additional: usize) {
|
||
self.reserve(additional);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "extend_ref", since = "1.2.0")]
|
||
impl<'a> Extend<&'a char> for String {
|
||
fn extend<I: IntoIterator<Item = &'a char>>(&mut self, iter: I) {
|
||
self.extend(iter.into_iter().cloned());
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_one(&mut self, &c: &'a char) {
|
||
self.push(c);
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_reserve(&mut self, additional: usize) {
|
||
self.reserve(additional);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a> Extend<&'a str> for String {
|
||
fn extend<I: IntoIterator<Item = &'a str>>(&mut self, iter: I) {
|
||
iter.into_iter().for_each(move |s| self.push_str(s));
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_one(&mut self, s: &'a str) {
|
||
self.push_str(s);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_str2", since = "1.45.0")]
|
||
impl<A: Allocator> Extend<Box<str, A>> for String {
|
||
fn extend<I: IntoIterator<Item = Box<str, A>>>(&mut self, iter: I) {
|
||
iter.into_iter().for_each(move |s| self.push_str(&s));
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "extend_string", since = "1.4.0")]
|
||
impl Extend<String> for String {
|
||
fn extend<I: IntoIterator<Item = String>>(&mut self, iter: I) {
|
||
iter.into_iter().for_each(move |s| self.push_str(&s));
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_one(&mut self, s: String) {
|
||
self.push_str(&s);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "herd_cows", since = "1.19.0")]
|
||
impl<'a> Extend<Cow<'a, str>> for String {
|
||
fn extend<I: IntoIterator<Item = Cow<'a, str>>>(&mut self, iter: I) {
|
||
iter.into_iter().for_each(move |s| self.push_str(&s));
|
||
}
|
||
|
||
#[inline]
|
||
fn extend_one(&mut self, s: Cow<'a, str>) {
|
||
self.push_str(&s);
|
||
}
|
||
}
|
||
|
||
/// A convenience impl that delegates to the impl for `&str`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// assert_eq!(String::from("Hello world").find("world"), Some(6));
|
||
/// ```
|
||
#[unstable(
|
||
feature = "pattern",
|
||
reason = "API not fully fleshed out and ready to be stabilized",
|
||
issue = "27721"
|
||
)]
|
||
impl<'a, 'b> Pattern<'a> for &'b String {
|
||
type Searcher = <&'b str as Pattern<'a>>::Searcher;
|
||
|
||
fn into_searcher(self, haystack: &'a str) -> <&'b str as Pattern<'a>>::Searcher {
|
||
self[..].into_searcher(haystack)
|
||
}
|
||
|
||
#[inline]
|
||
fn is_contained_in(self, haystack: &'a str) -> bool {
|
||
self[..].is_contained_in(haystack)
|
||
}
|
||
|
||
#[inline]
|
||
fn is_prefix_of(self, haystack: &'a str) -> bool {
|
||
self[..].is_prefix_of(haystack)
|
||
}
|
||
|
||
#[inline]
|
||
fn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str> {
|
||
self[..].strip_prefix_of(haystack)
|
||
}
|
||
|
||
#[inline]
|
||
fn is_suffix_of(self, haystack: &'a str) -> bool {
|
||
self[..].is_suffix_of(haystack)
|
||
}
|
||
|
||
#[inline]
|
||
fn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str> {
|
||
self[..].strip_suffix_of(haystack)
|
||
}
|
||
}
|
||
|
||
macro_rules! impl_eq {
|
||
($lhs:ty, $rhs: ty) => {
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[allow(unused_lifetimes)]
|
||
impl<'a, 'b> PartialEq<$rhs> for $lhs {
|
||
#[inline]
|
||
fn eq(&self, other: &$rhs) -> bool {
|
||
PartialEq::eq(&self[..], &other[..])
|
||
}
|
||
#[inline]
|
||
fn ne(&self, other: &$rhs) -> bool {
|
||
PartialEq::ne(&self[..], &other[..])
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[allow(unused_lifetimes)]
|
||
impl<'a, 'b> PartialEq<$lhs> for $rhs {
|
||
#[inline]
|
||
fn eq(&self, other: &$lhs) -> bool {
|
||
PartialEq::eq(&self[..], &other[..])
|
||
}
|
||
#[inline]
|
||
fn ne(&self, other: &$lhs) -> bool {
|
||
PartialEq::ne(&self[..], &other[..])
|
||
}
|
||
}
|
||
};
|
||
}
|
||
|
||
impl_eq! { String, str }
|
||
impl_eq! { String, &'a str }
|
||
#[cfg(not(no_global_oom_handling))]
|
||
impl_eq! { Cow<'a, str>, str }
|
||
#[cfg(not(no_global_oom_handling))]
|
||
impl_eq! { Cow<'a, str>, &'b str }
|
||
#[cfg(not(no_global_oom_handling))]
|
||
impl_eq! { Cow<'a, str>, String }
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Default for String {
|
||
/// Creates an empty `String`.
|
||
#[inline]
|
||
fn default() -> String {
|
||
String::new()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl fmt::Display for String {
|
||
#[inline]
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Display::fmt(&**self, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl fmt::Debug for String {
|
||
#[inline]
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Debug::fmt(&**self, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl hash::Hash for String {
|
||
#[inline]
|
||
fn hash<H: hash::Hasher>(&self, hasher: &mut H) {
|
||
(**self).hash(hasher)
|
||
}
|
||
}
|
||
|
||
/// Implements the `+` operator for concatenating two strings.
|
||
///
|
||
/// This consumes the `String` on the left-hand side and re-uses its buffer (growing it if
|
||
/// necessary). This is done to avoid allocating a new `String` and copying the entire contents on
|
||
/// every operation, which would lead to *O*(*n*^2) running time when building an *n*-byte string by
|
||
/// repeated concatenation.
|
||
///
|
||
/// The string on the right-hand side is only borrowed; its contents are copied into the returned
|
||
/// `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Concatenating two `String`s takes the first by value and borrows the second:
|
||
///
|
||
/// ```
|
||
/// let a = String::from("hello");
|
||
/// let b = String::from(" world");
|
||
/// let c = a + &b;
|
||
/// // `a` is moved and can no longer be used here.
|
||
/// ```
|
||
///
|
||
/// If you want to keep using the first `String`, you can clone it and append to the clone instead:
|
||
///
|
||
/// ```
|
||
/// let a = String::from("hello");
|
||
/// let b = String::from(" world");
|
||
/// let c = a.clone() + &b;
|
||
/// // `a` is still valid here.
|
||
/// ```
|
||
///
|
||
/// Concatenating `&str` slices can be done by converting the first to a `String`:
|
||
///
|
||
/// ```
|
||
/// let a = "hello";
|
||
/// let b = " world";
|
||
/// let c = a.to_string() + b;
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Add<&str> for String {
|
||
type Output = String;
|
||
|
||
#[inline]
|
||
fn add(mut self, other: &str) -> String {
|
||
self.push_str(other);
|
||
self
|
||
}
|
||
}
|
||
|
||
/// Implements the `+=` operator for appending to a `String`.
|
||
///
|
||
/// This has the same behavior as the [`push_str`][String::push_str] method.
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "stringaddassign", since = "1.12.0")]
|
||
impl AddAssign<&str> for String {
|
||
#[inline]
|
||
fn add_assign(&mut self, other: &str) {
|
||
self.push_str(other);
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<I> ops::Index<I> for String
|
||
where
|
||
I: slice::SliceIndex<str>,
|
||
{
|
||
type Output = I::Output;
|
||
|
||
#[inline]
|
||
fn index(&self, index: I) -> &I::Output {
|
||
index.index(self.as_str())
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<I> ops::IndexMut<I> for String
|
||
where
|
||
I: slice::SliceIndex<str>,
|
||
{
|
||
#[inline]
|
||
fn index_mut(&mut self, index: I) -> &mut I::Output {
|
||
index.index_mut(self.as_mut_str())
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl ops::Deref for String {
|
||
type Target = str;
|
||
|
||
#[inline]
|
||
fn deref(&self) -> &str {
|
||
unsafe { str::from_utf8_unchecked(&self.vec) }
|
||
}
|
||
}
|
||
|
||
#[unstable(feature = "deref_pure_trait", issue = "87121")]
|
||
unsafe impl ops::DerefPure for String {}
|
||
|
||
#[stable(feature = "derefmut_for_string", since = "1.3.0")]
|
||
impl ops::DerefMut for String {
|
||
#[inline]
|
||
fn deref_mut(&mut self) -> &mut str {
|
||
unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) }
|
||
}
|
||
}
|
||
|
||
/// A type alias for [`Infallible`].
|
||
///
|
||
/// This alias exists for backwards compatibility, and may be eventually deprecated.
|
||
///
|
||
/// [`Infallible`]: core::convert::Infallible "convert::Infallible"
|
||
#[stable(feature = "str_parse_error", since = "1.5.0")]
|
||
pub type ParseError = core::convert::Infallible;
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl FromStr for String {
|
||
type Err = core::convert::Infallible;
|
||
#[inline]
|
||
fn from_str(s: &str) -> Result<String, Self::Err> {
|
||
Ok(String::from(s))
|
||
}
|
||
}
|
||
|
||
/// A trait for converting a value to a `String`.
|
||
///
|
||
/// This trait is automatically implemented for any type which implements the
|
||
/// [`Display`] trait. As such, `ToString` shouldn't be implemented directly:
|
||
/// [`Display`] should be implemented instead, and you get the `ToString`
|
||
/// implementation for free.
|
||
///
|
||
/// [`Display`]: fmt::Display
|
||
#[cfg_attr(not(test), rustc_diagnostic_item = "ToString")]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub trait ToString {
|
||
/// Converts the given value to a `String`.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let i = 5;
|
||
/// let five = String::from("5");
|
||
///
|
||
/// assert_eq!(five, i.to_string());
|
||
/// ```
|
||
#[rustc_conversion_suggestion]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[cfg_attr(not(test), rustc_diagnostic_item = "to_string_method")]
|
||
fn to_string(&self) -> String;
|
||
}
|
||
|
||
/// # Panics
|
||
///
|
||
/// In this implementation, the `to_string` method panics
|
||
/// if the `Display` implementation returns an error.
|
||
/// This indicates an incorrect `Display` implementation
|
||
/// since `fmt::Write for String` never returns an error itself.
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: fmt::Display + ?Sized> ToString for T {
|
||
// A common guideline is to not inline generic functions. However,
|
||
// removing `#[inline]` from this method causes non-negligible regressions.
|
||
// See <https://github.com/rust-lang/rust/pull/74852>, the last attempt
|
||
// to try to remove it.
|
||
#[inline]
|
||
default fn to_string(&self) -> String {
|
||
let mut buf = String::new();
|
||
let mut formatter = core::fmt::Formatter::new(&mut buf);
|
||
// Bypass format_args!() to avoid write_str with zero-length strs
|
||
fmt::Display::fmt(self, &mut formatter)
|
||
.expect("a Display implementation returned an error unexpectedly");
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "ascii_char", issue = "110998")]
|
||
impl ToString for core::ascii::Char {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
self.as_str().to_owned()
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "char_to_string_specialization", since = "1.46.0")]
|
||
impl ToString for char {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
String::from(self.encode_utf8(&mut [0; 4]))
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "bool_to_string_specialization", since = "1.68.0")]
|
||
impl ToString for bool {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
String::from(if *self { "true" } else { "false" })
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "u8_to_string_specialization", since = "1.54.0")]
|
||
impl ToString for u8 {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
let mut buf = String::with_capacity(3);
|
||
let mut n = *self;
|
||
if n >= 10 {
|
||
if n >= 100 {
|
||
buf.push((b'0' + n / 100) as char);
|
||
n %= 100;
|
||
}
|
||
buf.push((b'0' + n / 10) as char);
|
||
n %= 10;
|
||
}
|
||
buf.push((b'0' + n) as char);
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "i8_to_string_specialization", since = "1.54.0")]
|
||
impl ToString for i8 {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
let mut buf = String::with_capacity(4);
|
||
if self.is_negative() {
|
||
buf.push('-');
|
||
}
|
||
let mut n = self.unsigned_abs();
|
||
if n >= 10 {
|
||
if n >= 100 {
|
||
buf.push('1');
|
||
n -= 100;
|
||
}
|
||
buf.push((b'0' + n / 10) as char);
|
||
n %= 10;
|
||
}
|
||
buf.push((b'0' + n) as char);
|
||
buf
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "str_to_string_specialization", since = "1.9.0")]
|
||
impl ToString for str {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
String::from(self)
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "cow_str_to_string_specialization", since = "1.17.0")]
|
||
impl ToString for Cow<'_, str> {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
self[..].to_owned()
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "string_to_string_specialization", since = "1.17.0")]
|
||
impl ToString for String {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
self.to_owned()
|
||
}
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "fmt_arguments_to_string_specialization", since = "1.71.0")]
|
||
impl ToString for fmt::Arguments<'_> {
|
||
#[inline]
|
||
fn to_string(&self) -> String {
|
||
crate::fmt::format(*self)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl AsRef<str> for String {
|
||
#[inline]
|
||
fn as_ref(&self) -> &str {
|
||
self
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "string_as_mut", since = "1.43.0")]
|
||
impl AsMut<str> for String {
|
||
#[inline]
|
||
fn as_mut(&mut self) -> &mut str {
|
||
self
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl AsRef<[u8]> for String {
|
||
#[inline]
|
||
fn as_ref(&self) -> &[u8] {
|
||
self.as_bytes()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl From<&str> for String {
|
||
/// Converts a `&str` into a [`String`].
|
||
///
|
||
/// The result is allocated on the heap.
|
||
#[inline]
|
||
fn from(s: &str) -> String {
|
||
s.to_owned()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "from_mut_str_for_string", since = "1.44.0")]
|
||
impl From<&mut str> for String {
|
||
/// Converts a `&mut str` into a [`String`].
|
||
///
|
||
/// The result is allocated on the heap.
|
||
#[inline]
|
||
fn from(s: &mut str) -> String {
|
||
s.to_owned()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "from_ref_string", since = "1.35.0")]
|
||
impl From<&String> for String {
|
||
/// Converts a `&String` into a [`String`].
|
||
///
|
||
/// This clones `s` and returns the clone.
|
||
#[inline]
|
||
fn from(s: &String) -> String {
|
||
s.clone()
|
||
}
|
||
}
|
||
|
||
// note: test pulls in std, which causes errors here
|
||
#[cfg(not(test))]
|
||
#[stable(feature = "string_from_box", since = "1.18.0")]
|
||
impl From<Box<str>> for String {
|
||
/// Converts the given boxed `str` slice to a [`String`].
|
||
/// It is notable that the `str` slice is owned.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s1: String = String::from("hello world");
|
||
/// let s2: Box<str> = s1.into_boxed_str();
|
||
/// let s3: String = String::from(s2);
|
||
///
|
||
/// assert_eq!("hello world", s3)
|
||
/// ```
|
||
fn from(s: Box<str>) -> String {
|
||
s.into_string()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "box_from_str", since = "1.20.0")]
|
||
impl From<String> for Box<str> {
|
||
/// Converts the given [`String`] to a boxed `str` slice that is owned.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s1: String = String::from("hello world");
|
||
/// let s2: Box<str> = Box::from(s1);
|
||
/// let s3: String = String::from(s2);
|
||
///
|
||
/// assert_eq!("hello world", s3)
|
||
/// ```
|
||
fn from(s: String) -> Box<str> {
|
||
s.into_boxed_str()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "string_from_cow_str", since = "1.14.0")]
|
||
impl<'a> From<Cow<'a, str>> for String {
|
||
/// Converts a clone-on-write string to an owned
|
||
/// instance of [`String`].
|
||
///
|
||
/// This extracts the owned string,
|
||
/// clones the string if it is not already owned.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```
|
||
/// # use std::borrow::Cow;
|
||
/// // If the string is not owned...
|
||
/// let cow: Cow<'_, str> = Cow::Borrowed("eggplant");
|
||
/// // It will allocate on the heap and copy the string.
|
||
/// let owned: String = String::from(cow);
|
||
/// assert_eq!(&owned[..], "eggplant");
|
||
/// ```
|
||
fn from(s: Cow<'a, str>) -> String {
|
||
s.into_owned()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a> From<&'a str> for Cow<'a, str> {
|
||
/// Converts a string slice into a [`Borrowed`] variant.
|
||
/// No heap allocation is performed, and the string
|
||
/// is not copied.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```
|
||
/// # use std::borrow::Cow;
|
||
/// assert_eq!(Cow::from("eggplant"), Cow::Borrowed("eggplant"));
|
||
/// ```
|
||
///
|
||
/// [`Borrowed`]: crate::borrow::Cow::Borrowed "borrow::Cow::Borrowed"
|
||
#[inline]
|
||
fn from(s: &'a str) -> Cow<'a, str> {
|
||
Cow::Borrowed(s)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a> From<String> for Cow<'a, str> {
|
||
/// Converts a [`String`] into an [`Owned`] variant.
|
||
/// No heap allocation is performed, and the string
|
||
/// is not copied.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```
|
||
/// # use std::borrow::Cow;
|
||
/// let s = "eggplant".to_string();
|
||
/// let s2 = "eggplant".to_string();
|
||
/// assert_eq!(Cow::from(s), Cow::<'static, str>::Owned(s2));
|
||
/// ```
|
||
///
|
||
/// [`Owned`]: crate::borrow::Cow::Owned "borrow::Cow::Owned"
|
||
#[inline]
|
||
fn from(s: String) -> Cow<'a, str> {
|
||
Cow::Owned(s)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "cow_from_string_ref", since = "1.28.0")]
|
||
impl<'a> From<&'a String> for Cow<'a, str> {
|
||
/// Converts a [`String`] reference into a [`Borrowed`] variant.
|
||
/// No heap allocation is performed, and the string
|
||
/// is not copied.
|
||
///
|
||
/// # Example
|
||
///
|
||
/// ```
|
||
/// # use std::borrow::Cow;
|
||
/// let s = "eggplant".to_string();
|
||
/// assert_eq!(Cow::from(&s), Cow::Borrowed("eggplant"));
|
||
/// ```
|
||
///
|
||
/// [`Borrowed`]: crate::borrow::Cow::Borrowed "borrow::Cow::Borrowed"
|
||
#[inline]
|
||
fn from(s: &'a String) -> Cow<'a, str> {
|
||
Cow::Borrowed(s.as_str())
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "cow_str_from_iter", since = "1.12.0")]
|
||
impl<'a> FromIterator<char> for Cow<'a, str> {
|
||
fn from_iter<I: IntoIterator<Item = char>>(it: I) -> Cow<'a, str> {
|
||
Cow::Owned(FromIterator::from_iter(it))
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "cow_str_from_iter", since = "1.12.0")]
|
||
impl<'a, 'b> FromIterator<&'b str> for Cow<'a, str> {
|
||
fn from_iter<I: IntoIterator<Item = &'b str>>(it: I) -> Cow<'a, str> {
|
||
Cow::Owned(FromIterator::from_iter(it))
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "cow_str_from_iter", since = "1.12.0")]
|
||
impl<'a> FromIterator<String> for Cow<'a, str> {
|
||
fn from_iter<I: IntoIterator<Item = String>>(it: I) -> Cow<'a, str> {
|
||
Cow::Owned(FromIterator::from_iter(it))
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "from_string_for_vec_u8", since = "1.14.0")]
|
||
impl From<String> for Vec<u8> {
|
||
/// Converts the given [`String`] to a vector [`Vec`] that holds values of type [`u8`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let s1 = String::from("hello world");
|
||
/// let v1 = Vec::from(s1);
|
||
///
|
||
/// for b in v1 {
|
||
/// println!("{b}");
|
||
/// }
|
||
/// ```
|
||
fn from(string: String) -> Vec<u8> {
|
||
string.into_bytes()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl fmt::Write for String {
|
||
#[inline]
|
||
fn write_str(&mut self, s: &str) -> fmt::Result {
|
||
self.push_str(s);
|
||
Ok(())
|
||
}
|
||
|
||
#[inline]
|
||
fn write_char(&mut self, c: char) -> fmt::Result {
|
||
self.push(c);
|
||
Ok(())
|
||
}
|
||
}
|
||
|
||
/// A draining iterator for `String`.
|
||
///
|
||
/// This struct is created by the [`drain`] method on [`String`]. See its
|
||
/// documentation for more.
|
||
///
|
||
/// [`drain`]: String::drain
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
pub struct Drain<'a> {
|
||
/// Will be used as &'a mut String in the destructor
|
||
string: *mut String,
|
||
/// Start of part to remove
|
||
start: usize,
|
||
/// End of part to remove
|
||
end: usize,
|
||
/// Current remaining range to remove
|
||
iter: Chars<'a>,
|
||
}
|
||
|
||
#[stable(feature = "collection_debug", since = "1.17.0")]
|
||
impl fmt::Debug for Drain<'_> {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
f.debug_tuple("Drain").field(&self.as_str()).finish()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
unsafe impl Sync for Drain<'_> {}
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
unsafe impl Send for Drain<'_> {}
|
||
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
impl Drop for Drain<'_> {
|
||
fn drop(&mut self) {
|
||
unsafe {
|
||
// Use Vec::drain. "Reaffirm" the bounds checks to avoid
|
||
// panic code being inserted again.
|
||
let self_vec = (*self.string).as_mut_vec();
|
||
if self.start <= self.end && self.end <= self_vec.len() {
|
||
self_vec.drain(self.start..self.end);
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<'a> Drain<'a> {
|
||
/// Returns the remaining (sub)string of this iterator as a slice.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut s = String::from("abc");
|
||
/// let mut drain = s.drain(..);
|
||
/// assert_eq!(drain.as_str(), "abc");
|
||
/// let _ = drain.next().unwrap();
|
||
/// assert_eq!(drain.as_str(), "bc");
|
||
/// ```
|
||
#[must_use]
|
||
#[stable(feature = "string_drain_as_str", since = "1.55.0")]
|
||
pub fn as_str(&self) -> &str {
|
||
self.iter.as_str()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "string_drain_as_str", since = "1.55.0")]
|
||
impl<'a> AsRef<str> for Drain<'a> {
|
||
fn as_ref(&self) -> &str {
|
||
self.as_str()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "string_drain_as_str", since = "1.55.0")]
|
||
impl<'a> AsRef<[u8]> for Drain<'a> {
|
||
fn as_ref(&self) -> &[u8] {
|
||
self.as_str().as_bytes()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
impl Iterator for Drain<'_> {
|
||
type Item = char;
|
||
|
||
#[inline]
|
||
fn next(&mut self) -> Option<char> {
|
||
self.iter.next()
|
||
}
|
||
|
||
fn size_hint(&self) -> (usize, Option<usize>) {
|
||
self.iter.size_hint()
|
||
}
|
||
|
||
#[inline]
|
||
fn last(mut self) -> Option<char> {
|
||
self.next_back()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
impl DoubleEndedIterator for Drain<'_> {
|
||
#[inline]
|
||
fn next_back(&mut self) -> Option<char> {
|
||
self.iter.next_back()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "fused", since = "1.26.0")]
|
||
impl FusedIterator for Drain<'_> {}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "from_char_for_string", since = "1.46.0")]
|
||
impl From<char> for String {
|
||
/// Allocates an owned [`String`] from a single character.
|
||
///
|
||
/// # Example
|
||
/// ```rust
|
||
/// let c: char = 'a';
|
||
/// let s: String = String::from(c);
|
||
/// assert_eq!("a", &s[..]);
|
||
/// ```
|
||
#[inline]
|
||
fn from(c: char) -> Self {
|
||
c.to_string()
|
||
}
|
||
}
|