arrayvec/src/array_string.rs at arraystring-wip · gz/arrayvec · GitHub

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use std::borrow::Borrow;

use std::fmt;

use std::mem;

use std::ops::Deref;

use std::str;

use std::slice;

use array::Array;

use array::Index;

/// A string with a fixed capacity.

///

/// The `ArrayString` is a string backed by a fixed size array. It keeps track

/// of its length.

///

/// The string is a contiguous value that you can store directly on the stack

/// if needed.

///

/// Due to technical restrictions, this struct does not implement `Copy` even

/// though it would be safe to do so.

#[derive(Copy)]

pub struct ArrayString<A: Array<Item=u8>> {

xs: A,

len: A::Index,

}

unsafe fn new_array<A: Array<Item=u8>>() -> A {

// Note: Returning an uninitialized value here only works

// if we can be sure the data is never used. The nullable pointer

// inside enum optimization conflicts with this this for example,

// so we need to be extra careful. See `NoDrop` enum.

mem::uninitialized()

}

impl<A: Array<Item=u8>> ArrayString<A> {

/// Create a new empty `ArrayString`.

///

/// Capacity is inferred from the type parameter.

///

/// ```

/// use arrayvec::ArrayString;

///

/// let mut string = ArrayString::<[_; 16]>::new();

/// string.push_str("foo");

/// assert_eq!(&string[..], "foo");

/// assert_eq!(string.capacity(), 16);

/// ```

pub fn new() -> ArrayString<A> {

unsafe {

ArrayString {

xs: new_array(),

len: Index::from(0),

}

/// Return the capacity of the `ArrayString`.

///

/// ```

/// use arrayvec::ArrayString;

///

/// let string = ArrayString::<[_; 3]>::new();

/// assert_eq!(string.capacity(), 3);

/// ```

#[inline]

pub fn capacity(&self) -> usize { A::capacity() }

/// Adds the given char to the end of the string.

///

/// Returns `None` if the push succeeds, or and returns `Some(c)` if the

/// backing array is not large enough to fit the additional char.

///

/// ```

/// use arrayvec::ArrayString;

///

/// let mut string = ArrayString::<[_; 2]>::new();

///

/// let none1 = string.push('a');

/// let none2 = string.push('b');

/// let overflow = string.push('c');

///

/// assert_eq!(&string[..], "ab");

/// assert_eq!(none1, None);

/// assert_eq!(none2, None);

/// assert_eq!(overflow, Some('c'));

/// ```

pub fn push(&mut self, c: char) -> Option<char> {

use std::fmt::Write;

self.write_char(c).err().map(|_| c)

}

/// Adds the given string slice to the end of the string.

///

/// Returns `None` if the push succeeds, or and returns `Some(s)` if the

/// backing array is not large enough to fit the string.

///

/// ```

/// use arrayvec::ArrayString;

///

/// let mut string = ArrayString::<[_; 2]>::new();

///

/// let none1 = string.push_str("a");

/// let overflow1 = string.push_str("bc");

/// let none2 = string.push_str("d");

/// let overflow2 = string.push_str("ef");

///

/// assert_eq!(&string[..], "ad");

/// assert_eq!(none1, None);

/// assert_eq!(none2, None);

/// assert_eq!(overflow1, Some("bc"));

/// assert_eq!(overflow2, Some("ef"));

/// ```

pub fn push_str<'a>(&mut self, s: &'a str) -> Option<&'a str> {

use std::io::Write;

if self.len() + s.len() > self.capacity() {

return Some(s);

}

unsafe {

let sl = slice::from_raw_parts_mut(self.xs.as_mut_ptr(), A::capacity());

(&mut sl[self.len()..]).write(s.as_bytes()).unwrap();

let newl = self.len() + s.len();

self.set_len(newl);

}

None

}

/// Make the string empty.

pub fn clear(&mut self) {

unsafe {

self.set_len(0);

}

/// Set the strings's length.

///

/// May panic if `length` is greater than the capacity.

///

/// This function is `unsafe` because it changes the notion of the

/// number of “valid” bytes in the string. Use with care.

#[inline]

pub unsafe fn set_len(&mut self, length: usize) {

debug_assert!(length <= self.capacity());

self.len = Index::from(length);

}

impl<A: Array<Item=u8>> Deref for ArrayString<A> {

type Target = str;

#[inline]

fn deref(&self) -> &str {

unsafe {

let sl = slice::from_raw_parts(self.xs.as_ptr(), self.len.to_usize());

str::from_utf8_unchecked(sl)

}

impl<A: Array<Item=u8>> Borrow<str> for ArrayString<A> {

fn borrow(&self) -> &str { self }

}

impl<A: Array<Item=u8>> AsRef<str> for ArrayString<A> {

fn as_ref(&self) -> &str { self }

}

impl<A: Array<Item=u8>> fmt::Debug for ArrayString<A> where A::Item: fmt::Debug {

fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { (**self).fmt(f) }

}

/// `Write` appends written data to the end of the string.

impl<A: Array<Item=u8>> fmt::Write for ArrayString<A> {

fn write_str(&mut self, s: &str) -> fmt::Result {

match self.push_str(s) {

None => Ok(()),

Some(_) => Err(fmt::Error),

}

impl<A: Array<Item=u8> + Copy> Clone for ArrayString<A> {

fn clone(&self) -> ArrayString<A> {

*self

}

arrayvec/src/array_string.rs at arraystring-wip · gz/arrayvec · GitHub

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