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// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! A stack-allocated vector, allowing storage of N elements on the stack.
//!
//! Currently, only the N = 8 case is supported (due to Array only being impl-ed for [T; 8]).
use std::marker::Unsize;
use std::iter::Extend;
use std::ptr::drop_in_place;
use std::ops::{Deref, DerefMut};
use std::slice;
use std::fmt;
pub unsafe trait Array {
type Element;
type PartialStorage: Default + Unsize<[ManuallyDrop<Self::Element>]>;
const LEN: usize;
}
unsafe impl<T> Array for [T; 8] {
type Element = T;
type PartialStorage = [ManuallyDrop<T>; 8];
const LEN: usize = 8;
}
pub struct ArrayVec<A: Array> {
count: usize,
values: A::PartialStorage
}
impl<A: Array> ArrayVec<A> {
pub fn new() -> Self {
ArrayVec {
count: 0,
values: Default::default(),
}
}
}
impl<A> fmt::Debug for ArrayVec<A>
where A: Array,
A::Element: fmt::Debug {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
self[..].fmt(f)
}
}
impl<A: Array> Deref for ArrayVec<A> {
type Target = [A::Element];
fn deref(&self) -> &Self::Target {
unsafe {
slice::from_raw_parts(&self.values as *const _ as *const A::Element, self.count)
}
}
}
impl<A: Array> DerefMut for ArrayVec<A> {
fn deref_mut(&mut self) -> &mut [A::Element] {
unsafe {
slice::from_raw_parts_mut(&mut self.values as *mut _ as *mut A::Element, self.count)
}
}
}
impl<A: Array> Drop for ArrayVec<A> {
fn drop(&mut self) {
unsafe {
drop_in_place(&mut self[..])
}
}
}
impl<A: Array> Extend<A::Element> for ArrayVec<A> {
fn extend<I>(&mut self, iter: I) where I: IntoIterator<Item=A::Element> {
for el in iter {
unsafe {
let arr = &mut self.values as &mut [ManuallyDrop<_>];
arr[self.count].value = el;
}
self.count += 1;
}
}
}
// FIXME: This should use repr(transparent) from rust-lang/rfcs#1758.
#[allow(unions_with_drop_fields)]
pub union ManuallyDrop<T> {
value: T,
#[allow(dead_code)]
empty: (),
}
impl<T> Default for ManuallyDrop<T> {
fn default() -> Self {
ManuallyDrop { empty: () }
}
}
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