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Add TryFrom/From Conversion Methods for Vec<_> and Box<[_]> #195

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Add TryFrom/From Conversion Methods for Vec<_> and Box<[_]> #195

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138 changes: 138 additions & 0 deletions src/array_string.rs
View file
Open in desktop
Expand Up @@ -365,6 +365,102 @@ impl<const CAP: usize> ArrayString<CAP>
self.len = length as LenUint;
}

/// Converts `self` into an allocated byte-vector with the given capacity.
///
/// # Safety
///
/// The caller is responsible for ensuring that `capacity >= self.len()`.
pub unsafe fn into_bytes_with_capacity(self, capacity: usize) -> Vec<u8> {
debug_assert!(capacity >= self.len());

let mut vec = Vec::with_capacity(capacity);
let me = core::mem::ManuallyDrop::new(self);
let len = me.len();

// SAFETY: The caller ensures that we own a region of memory at least as large as `len`
// at the location pointed to by `vec`.
me.as_ptr().copy_to_nonoverlapping(vec.as_mut_ptr(), len);
vec.set_len(len);

vec
}

/// Converts `self` into an allocated vector of bytes.
///
/// # Allocation
///
/// This method allocates a vector with capacity equal to the capacity of the original
/// `ArrayString`.
///
/// To only allocate exactly enough space for the string stored in `self`, use the
/// [`into_boxed_str`](Self::into_boxed_str) method.
///
/// To allocate a specific amount of space, see the
/// [`into_bytes_with_capacity`](Self::into_bytes_with_capacity) method.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use arrayvec::ArrayString;
///
/// let s = ArrayString::<5>::from("hello").unwrap();
/// let bytes = s.into_bytes();
///
/// assert_eq!(&[104, 101, 108, 108, 111][..], &bytes[..]);
/// ```
#[inline]
pub fn into_bytes(self) -> Vec<u8> {
// SAFETY: The capacity of `self` is at least as large as the length of `self`.
unsafe {
self.into_bytes_with_capacity(CAP)
}
}

/// Converts this `ArrayString` into a [`Box`]`<`[`str`]`>`.
///
/// This will drop any excess capacity.
///
/// [`str`]: prim@str
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use arrayvec::ArrayString;
///
/// let s = ArrayString::<5>::from("hello").unwrap();
///
/// let b = s.into_boxed_str();
/// ```
#[inline]
pub fn into_boxed_str(self) -> Box<str> {
let len = self.len();
// SAFETY: We only require the memory capacity equal to the length of the initialized data region in `self`.
unsafe {
str::from_boxed_utf8_unchecked(self.into_bytes_with_capacity(len).into_boxed_slice())
}
}

/// Create a new `ArrayString` by consuming a boxed string, moving the heap-allocated `str` to a
/// stack-allocated array.
///
/// # Safety
///
/// The caller is responsible for ensuring that the string has a length no larger than the
/// capacity of `ArrayString`.
pub unsafe fn from_boxed_str_unchecked(boxed_string: Box<str>) -> Self {
debug_assert!(CAP >= boxed_string.len());
assert_capacity_limit!(CAP);
let len = boxed_string.len() as LenUint;
Self {
xs: *Box::from_raw(Box::into_raw(boxed_string) as *mut [MaybeUninit<u8>; CAP]) ,
len,
}
}

/// Return a string slice of the whole `ArrayString`.
pub fn as_str(&self) -> &str {
self
Expand Down Expand Up @@ -581,6 +677,48 @@ impl<'de, const CAP: usize> Deserialize<'de> for ArrayString<CAP>
}
}

impl<const CAP: usize> From<ArrayString<CAP>> for Box<str> {
#[inline]
fn from(array: ArrayString<CAP>) -> Self {
array.into_boxed_str()
}
}

impl<const CAP: usize> TryFrom<Box<str>> for ArrayString<CAP> {
type Error = CapacityError;

fn try_from(string: Box<str>) -> Result<Self, Self::Error> {
if CAP < string.len() {
Err(CapacityError::new(()))
} else {
Ok(unsafe { Self::from_boxed_str_unchecked(string) })
}
}
}

impl<const CAP: usize> From<ArrayString<CAP>> for Vec<u8> {
#[inline]
fn from(array: ArrayString<CAP>) -> Self {
array.into_bytes()
}
}

impl<const CAP: usize> From<ArrayString<CAP>> for String {
#[inline]
fn from(array: ArrayString<CAP>) -> Self {
array.to_string()
}
}

impl<const CAP: usize> TryFrom<String> for ArrayString<CAP> {
type Error = CapacityError;

#[inline]
fn try_from(string: String) -> Result<Self, Self::Error> {
Self::try_from(string.into_boxed_str())
}
}

impl<'a, const CAP: usize> TryFrom<&'a str> for ArrayString<CAP>
{
type Error = CapacityError<&'a str>;
Expand Down
181 changes: 173 additions & 8 deletions src/arrayvec.rs
View file
Open in desktop
@@ -1,5 +1,5 @@

use std::cmp;
use std::convert::TryFrom;
use std::iter;
use std::mem;
use std::ops::{Bound, Deref, DerefMut, RangeBounds};
Expand Down Expand Up @@ -61,9 +61,6 @@ macro_rules! panic_oob {
}

impl<T, const CAP: usize> ArrayVec<T, CAP> {
/// Capacity
const CAPACITY: usize = CAP;

/// Create a new empty `ArrayVec`.
///
/// The maximum capacity is given by the generic parameter `CAP`.
Expand Down Expand Up @@ -642,14 +639,83 @@ impl<T, const CAP: usize> ArrayVec<T, CAP> {

/// Return the inner fixed size array.
///
/// Safety:
/// # Safety
///
/// This operation is safe if and only if length equals capacity.
pub unsafe fn into_inner_unchecked(self) -> [T; CAP] {
debug_assert_eq!(self.len(), self.capacity());
let self_ = ManuallyDrop::new(self);
let array = ptr::read(self_.as_ptr() as *const [T; CAP]);
array
}

/// Converts `self` into an allocated vector with the given capacity.
///
/// # Safety
///
/// The caller is responsible for ensuring that `capacity >= self.len()`.
pub unsafe fn into_vec_with_capacity(self, capacity: usize) -> Vec<T> {
debug_assert!(capacity >= self.len());

let mut vec = Vec::with_capacity(capacity);
let me = ManuallyDrop::new(self);
let len = me.len();

// SAFETY: The caller ensures that we own a region of memory at least as large as `len`
// at the location pointed to by `vec`.
me.as_ptr().copy_to_nonoverlapping(vec.as_mut_ptr(), len);
vec.set_len(len);

vec
}

/// Converts `self` into an allocated vector.
///
/// # Allocation
///
/// This method allocates a vector with capacity equal to the capacity of the original `ArrayVec`.
///
/// To only allocate exactly enough space for the elements stored in `self`, use the
/// [`into_boxed_slice`](Self::into_boxed_slice) method.
///
/// To allocate a specific amount of space, see the
/// [`into_vec_with_capacity`](Self::into_vec_with_capacity) method.
#[inline]
pub fn into_vec(self) -> Vec<T> {
// SAFETY: The capacity of `self` is at least as large as the length of `self`.
unsafe {
self.into_vec_with_capacity(CAP)
}
}

/// Converts the `ArrayVec` into `Box<[T]>`.
///
/// Note that this will drop any excess capacity.
#[inline]
pub fn into_boxed_slice(self) -> Box<[T]> {
let len = self.len();
// SAFETY: We only require the memory capacity equal to the length of the initialized data region in `self`.
unsafe {
self.into_vec_with_capacity(len).into_boxed_slice()
}
}

/// Create a new `ArrayVec` by consuming a boxed slice, moving the heap-allocated slice to a
/// stack-allocated array.
///
/// # Safety
///
/// The caller is responsible for ensuring that the slice has a length no larger than the
/// capacity of `ArrayVec`.
pub unsafe fn from_boxed_slice_unchecked(boxed_slice: Box<[T]>) -> Self {
debug_assert!(CAP >= boxed_slice.len());
assert_capacity_limit!(CAP);
let len = boxed_slice.len() as LenUint;
Self {
xs: *Box::from_raw(Box::into_raw(boxed_slice) as *mut [MaybeUninit<T>; CAP]) ,
len,
}
}

/// Returns the ArrayVec, replacing the original with a new empty ArrayVec.
///
Expand Down Expand Up @@ -743,7 +809,6 @@ impl<T, const CAP: usize> From<[T; CAP]> for ArrayVec<T, CAP> {
}
}


/// Try to create an `ArrayVec` from a slice. This will return an error if the slice was too big to
/// fit.
///
Expand All @@ -755,13 +820,13 @@ impl<T, const CAP: usize> From<[T; CAP]> for ArrayVec<T, CAP> {
/// assert_eq!(array.len(), 3);
/// assert_eq!(array.capacity(), 4);
/// ```
impl<T, const CAP: usize> std::convert::TryFrom<&[T]> for ArrayVec<T, CAP>
impl<T, const CAP: usize> TryFrom<&[T]> for ArrayVec<T, CAP>
where T: Clone,
{
type Error = CapacityError;

fn try_from(slice: &[T]) -> Result<Self, Self::Error> {
if Self::CAPACITY < slice.len() {
if CAP < slice.len() {
Err(CapacityError::new(()))
} else {
let mut array = Self::new();
Expand All @@ -771,6 +836,106 @@ impl<T, const CAP: usize> std::convert::TryFrom<&[T]> for ArrayVec<T, CAP>
}
}

/// Create a `Box<[T]>` from an `ArrayVec<T>`.
///
/// ```
/// use arrayvec::ArrayVec;
///
/// let array = ArrayVec::from([1, 2, 3]);
/// let slice = Box::<[_]>::from(array.clone());
/// assert_eq!(array.as_slice(), slice.as_ref());
/// ```
impl<T, const CAP: usize> From<ArrayVec<T, CAP>> for Box<[T]> {
#[inline]
fn from(array: ArrayVec<T, CAP>) -> Self {
array.into_boxed_slice()
}
}

/// Try to create an `ArrayVec` from a `Box<[_]>`. This will return an error if the boxed slice was too big to
/// fit.
///
/// ```
/// use arrayvec::ArrayVec;
/// use std::convert::TryInto as _;
///
/// let slice: Box<[_]> = Box::new([1, 2, 3]);
/// let array: ArrayVec<_, 4> = slice.clone().try_into().unwrap();
/// assert_eq!(array.len(), 3);
/// assert_eq!(array.capacity(), 4);
/// ```
impl<T, const CAP: usize> TryFrom<Box<[T]>> for ArrayVec<T, CAP> {
type Error = CapacityError;

fn try_from(slice: Box<[T]>) -> Result<Self, Self::Error> {
if CAP < slice.len() {
Err(CapacityError::new(()))
} else {
Ok(unsafe { Self::from_boxed_slice_unchecked(slice) })
}
}
}

/// Try to create an `ArrayVec` from a `Box<[_; N]>`. This will return an error if the boxed array was too big to
/// fit.
///
/// ```
/// use arrayvec::ArrayVec;
/// use std::convert::TryInto as _;
///
/// let slice: Box<[_; 3]> = Box::new([1, 2, 3]);
/// let array: ArrayVec<_, 4> = slice.clone().try_into().unwrap();
/// assert_eq!(array.len(), 3);
/// assert_eq!(array.capacity(), 4);
/// ```
impl<T, const N: usize, const CAP: usize> TryFrom<Box<[T; N]>> for ArrayVec<T, CAP> {
type Error = CapacityError;

#[inline]
fn try_from(array: Box<[T; N]>) -> Result<Self, Self::Error> {
Self::try_from(array as Box<[_]>)
}
}

/// Create a `Vec<T>` from an `ArrayVec<T>`.
///
/// ```
/// use arrayvec::ArrayVec;
/// use std::convert::TryInto as _;
///
/// let array: ArrayVec<_, 4> = vec![1, 2, 3].try_into().unwrap();
/// let vector = Vec::from(array.clone());
/// assert_eq!(array.capacity(), vector.capacity());
/// assert_eq!(array.as_slice(), vector.as_slice());
/// ```
impl<T, const CAP: usize> From<ArrayVec<T, CAP>> for Vec<T> {
#[inline]
fn from(array: ArrayVec<T, CAP>) -> Self {
array.into_vec()
}
}

/// Try to create an `ArrayVec` from a `Vec`. This will return an error if the vector was too big to
/// fit.
///
/// ```
/// use arrayvec::ArrayVec;
/// use std::convert::TryInto as _;
///
/// let vec = vec![1, 2, 3];
/// let array: ArrayVec<_, 4> = vec.clone().try_into().unwrap();
/// assert_eq!(array.len(), 3);
/// assert_eq!(array.capacity(), 4);
/// assert_eq!(vec.as_slice(), array.as_slice());
/// ```
impl<T, const CAP: usize> TryFrom<Vec<T>> for ArrayVec<T, CAP> {
type Error = CapacityError;

#[inline]
fn try_from(vec: Vec<T>) -> Result<Self, Self::Error> {
Self::try_from(vec.into_boxed_slice())
}
}

/// Iterate the `ArrayVec` with references to each element.
///
Expand Down