1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67
// Copyright 2020 bluss and ndarray developers. // // 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. use std::mem::size_of; use std::mem::ManuallyDrop; use std::mem::MaybeUninit; use crate::imp_prelude::*; use crate::RawDataSubst; /// Methods specific to arrays with `MaybeUninit` elements. /// /// ***See also all methods for [`ArrayBase`]*** /// /// [`ArrayBase`]: struct.ArrayBase.html impl<A, S, D> ArrayBase<S, D> where S: RawDataSubst<A, Elem=MaybeUninit<A>>, D: Dimension, { /// **Promise** that the array's elements are all fully initialized, and convert /// the array from element type `MaybeUninit<A>` to `A`. /// /// For example, it can convert an `Array<MaybeUninit<f64>, D>` to `Array<f64, D>`. /// /// ## Safety /// /// Safe to use if all the array's elements have been initialized. /// /// Note that for owned and shared ownership arrays, the promise must include all of the /// array's storage; it is for example possible to slice these in place, but that must /// only be done after all elements have been initialized. pub unsafe fn assume_init(self) -> ArrayBase<<S as RawDataSubst<A>>::Output, D> { // NOTE: Fully initialized includes elements not reachable in current slicing/view. let ArrayBase { data, ptr, dim, strides } = self; // transmute from storage of MaybeUninit<A> to storage of A let data = unlimited_transmute::<S, S::Output>(data); let ptr = ptr.cast::<A>(); ArrayBase { data, ptr, dim, strides, } } } /// Transmute from A to B. /// /// Like transmute, but does not have the compile-time size check which blocks /// using regular transmute for "S to S::Output". /// /// **Panics** if the size of A and B are different. unsafe fn unlimited_transmute<A, B>(data: A) -> B { assert_eq!(size_of::<A>(), size_of::<B>()); let old_data = ManuallyDrop::new(data); (&*old_data as *const A as *const B).read() }