a4f7ba376e
AccumulateVec is generic over the Array trait, which is currently only implemented for [T; 8].
106 lines
2.7 KiB
Rust
106 lines
2.7 KiB
Rust
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! A stack-allocated vector, allowing storage of N elements on the stack.
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//!
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//! Currently, only the N = 8 case is supported (due to Array only being impl-ed for [T; 8]).
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use std::marker::Unsize;
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use std::iter::Extend;
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use std::ptr::drop_in_place;
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use std::ops::{Deref, DerefMut};
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use std::slice;
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use std::fmt;
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pub unsafe trait Array {
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type Element;
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type PartialStorage: Default + Unsize<[ManuallyDrop<Self::Element>]>;
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const LEN: usize;
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}
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unsafe impl<T> Array for [T; 8] {
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type Element = T;
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type PartialStorage = [ManuallyDrop<T>; 8];
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const LEN: usize = 8;
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}
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pub struct ArrayVec<A: Array> {
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count: usize,
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values: A::PartialStorage
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}
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impl<A: Array> ArrayVec<A> {
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pub fn new() -> Self {
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ArrayVec {
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count: 0,
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values: Default::default(),
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}
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}
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}
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impl<A> fmt::Debug for ArrayVec<A>
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where A: Array,
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A::Element: fmt::Debug {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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self[..].fmt(f)
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}
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}
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impl<A: Array> Deref for ArrayVec<A> {
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type Target = [A::Element];
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fn deref(&self) -> &Self::Target {
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unsafe {
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slice::from_raw_parts(&self.values as *const _ as *const A::Element, self.count)
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}
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}
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}
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impl<A: Array> DerefMut for ArrayVec<A> {
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fn deref_mut(&mut self) -> &mut [A::Element] {
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unsafe {
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slice::from_raw_parts_mut(&mut self.values as *mut _ as *mut A::Element, self.count)
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}
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}
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}
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impl<A: Array> Drop for ArrayVec<A> {
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fn drop(&mut self) {
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unsafe {
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drop_in_place(&mut self[..])
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}
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}
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}
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impl<A: Array> Extend<A::Element> for ArrayVec<A> {
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fn extend<I>(&mut self, iter: I) where I: IntoIterator<Item=A::Element> {
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for el in iter {
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unsafe {
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let arr = &mut self.values as &mut [ManuallyDrop<_>];
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arr[self.count].value = el;
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}
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self.count += 1;
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}
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}
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}
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// FIXME: This should use repr(transparent) from rust-lang/rfcs#1758.
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#[allow(unions_with_drop_fields)]
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pub union ManuallyDrop<T> {
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value: T,
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#[allow(dead_code)]
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empty: (),
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}
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impl<T> Default for ManuallyDrop<T> {
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fn default() -> Self {
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ManuallyDrop { empty: () }
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}
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}
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