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Add try_into_owned_nocopy method #1022

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merged 2 commits into from
Nov 7, 2021
Merged

Add try_into_owned_nocopy method #1022

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31189d0
Add try_into_owned_nocopy method
jturner314 Jun 1, 2021
061ffce
Use type aliases to simplify type signatures
jturner314 Jun 1, 2021
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94 changes: 85 additions & 9 deletions src/data_traits.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,9 @@ use std::ptr::NonNull;
use alloc::sync::Arc;
use alloc::vec::Vec;

use crate::{ArrayBase, CowRepr, Dimension, OwnedArcRepr, OwnedRepr, RawViewRepr, ViewRepr};
use crate::{
ArcArray, Array, ArrayBase, CowRepr, Dimension, OwnedArcRepr, OwnedRepr, RawViewRepr, ViewRepr,
};

/// Array representation trait.
///
Expand Down Expand Up @@ -97,16 +99,25 @@ pub unsafe trait Data: RawData {
/// Converts the array to a uniquely owned array, cloning elements if necessary.
#[doc(hidden)]
#[allow(clippy::wrong_self_convention)]
fn into_owned<D>(self_: ArrayBase<Self, D>) -> ArrayBase<OwnedRepr<Self::Elem>, D>
fn into_owned<D>(self_: ArrayBase<Self, D>) -> Array<Self::Elem, D>
where
Self::Elem: Clone,
D: Dimension;

/// Converts the array into `Array<A, D>` if this is possible without
/// cloning the array elements. Otherwise, returns `self_` unchanged.
#[doc(hidden)]
fn try_into_owned_nocopy<D>(
self_: ArrayBase<Self, D>,
) -> Result<Array<Self::Elem, D>, ArrayBase<Self, D>>
where
D: Dimension;

/// Return a shared ownership (copy on write) array based on the existing one,
/// cloning elements if necessary.
#[doc(hidden)]
#[allow(clippy::wrong_self_convention)]
fn to_shared<D>(self_: &ArrayBase<Self, D>) -> ArrayBase<OwnedArcRepr<Self::Elem>, D>
fn to_shared<D>(self_: &ArrayBase<Self, D>) -> ArcArray<Self::Elem, D>
where
Self::Elem: Clone,
D: Dimension,
Expand Down Expand Up @@ -259,7 +270,7 @@ where
}

unsafe impl<A> Data for OwnedArcRepr<A> {
fn into_owned<D>(mut self_: ArrayBase<Self, D>) -> ArrayBase<OwnedRepr<Self::Elem>, D>
fn into_owned<D>(mut self_: ArrayBase<Self, D>) -> Array<Self::Elem, D>
where
A: Clone,
D: Dimension,
Expand All @@ -273,8 +284,29 @@ unsafe impl<A> Data for OwnedArcRepr<A> {
}
}

fn try_into_owned_nocopy<D>(
self_: ArrayBase<Self, D>,
) -> Result<Array<Self::Elem, D>, ArrayBase<Self, D>>
where
D: Dimension,
{
match Arc::try_unwrap(self_.data.0) {
Ok(owned_data) => unsafe {
// Safe because the data is equivalent.
Ok(ArrayBase::from_data_ptr(owned_data, self_.ptr)
.with_strides_dim(self_.strides, self_.dim))
},
Err(arc_data) => unsafe {
// Safe because the data is equivalent; we're just
// reconstructing `self_`.
Err(ArrayBase::from_data_ptr(OwnedArcRepr(arc_data), self_.ptr)
.with_strides_dim(self_.strides, self_.dim))
},
}
}

#[allow(clippy::wrong_self_convention)]
fn to_shared<D>(self_: &ArrayBase<Self, D>) -> ArrayBase<OwnedArcRepr<Self::Elem>, D>
fn to_shared<D>(self_: &ArrayBase<Self, D>) -> ArcArray<Self::Elem, D>
where
Self::Elem: Clone,
D: Dimension,
Expand Down Expand Up @@ -327,13 +359,23 @@ unsafe impl<A> RawDataMut for OwnedRepr<A> {

unsafe impl<A> Data for OwnedRepr<A> {
#[inline]
fn into_owned<D>(self_: ArrayBase<Self, D>) -> ArrayBase<OwnedRepr<Self::Elem>, D>
fn into_owned<D>(self_: ArrayBase<Self, D>) -> Array<Self::Elem, D>
where
A: Clone,
D: Dimension,
{
self_
}

#[inline]
fn try_into_owned_nocopy<D>(
self_: ArrayBase<Self, D>,
) -> Result<Array<Self::Elem, D>, ArrayBase<Self, D>>
where
D: Dimension,
{
Ok(self_)
}
}

unsafe impl<A> DataMut for OwnedRepr<A> {}
Expand Down Expand Up @@ -383,13 +425,22 @@ unsafe impl<'a, A> RawData for ViewRepr<&'a A> {
}

unsafe impl<'a, A> Data for ViewRepr<&'a A> {
fn into_owned<D>(self_: ArrayBase<Self, D>) -> ArrayBase<OwnedRepr<Self::Elem>, D>
fn into_owned<D>(self_: ArrayBase<Self, D>) -> Array<Self::Elem, D>
where
Self::Elem: Clone,
D: Dimension,
{
self_.to_owned()
}

fn try_into_owned_nocopy<D>(
self_: ArrayBase<Self, D>,
) -> Result<Array<Self::Elem, D>, ArrayBase<Self, D>>
where
D: Dimension,
{
Err(self_)
}
}

unsafe impl<'a, A> RawDataClone for ViewRepr<&'a A> {
Expand Down Expand Up @@ -428,13 +479,22 @@ unsafe impl<'a, A> RawDataMut for ViewRepr<&'a mut A> {
}

unsafe impl<'a, A> Data for ViewRepr<&'a mut A> {
fn into_owned<D>(self_: ArrayBase<Self, D>) -> ArrayBase<OwnedRepr<Self::Elem>, D>
fn into_owned<D>(self_: ArrayBase<Self, D>) -> Array<Self::Elem, D>
where
Self::Elem: Clone,
D: Dimension,
{
self_.to_owned()
}

fn try_into_owned_nocopy<D>(
self_: ArrayBase<Self, D>,
) -> Result<Array<Self::Elem, D>, ArrayBase<Self, D>>
where
D: Dimension,
{
Err(self_)
}
}

unsafe impl<'a, A> DataMut for ViewRepr<&'a mut A> {}
Expand Down Expand Up @@ -590,7 +650,7 @@ where

unsafe impl<'a, A> Data for CowRepr<'a, A> {
#[inline]
fn into_owned<D>(self_: ArrayBase<CowRepr<'a, A>, D>) -> ArrayBase<OwnedRepr<Self::Elem>, D>
fn into_owned<D>(self_: ArrayBase<CowRepr<'a, A>, D>) -> Array<Self::Elem, D>
where
A: Clone,
D: Dimension,
Expand All @@ -604,6 +664,22 @@ unsafe impl<'a, A> Data for CowRepr<'a, A> {
},
}
}

fn try_into_owned_nocopy<D>(
self_: ArrayBase<Self, D>,
) -> Result<Array<Self::Elem, D>, ArrayBase<Self, D>>
where
D: Dimension,
{
match self_.data {
CowRepr::View(_) => Err(self_),
CowRepr::Owned(data) => unsafe {
// safe because the data is equivalent so ptr, dims remain valid
Ok(ArrayBase::from_data_ptr(data, self_.ptr)
.with_strides_dim(self_.strides, self_.dim))
},
}
}
}

unsafe impl<'a, A> DataMut for CowRepr<'a, A> where A: Clone {}
Expand Down
28 changes: 28 additions & 0 deletions src/impl_methods.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -241,6 +241,34 @@ where
S::into_owned(self)
}

/// Converts the array into `Array<A, D>` if this is possible without
/// cloning the array elements. Otherwise, returns `self` unchanged.
///
/// ```
/// use ndarray::{array, rcarr2, ArcArray2, Array2};
///
/// // Reference-counted, clone-on-write `ArcArray`.
/// let a: ArcArray2<_> = rcarr2(&[[1., 2.], [3., 4.]]);
/// {
/// // Another reference to the same data.
/// let b: ArcArray2<_> = a.clone();
/// // Since there are two references to the same data, `.into_owned()`
/// // would require cloning the data, so `.try_into_owned_nocopy()`
/// // returns `Err`.
/// assert!(b.try_into_owned_nocopy().is_err());
/// }
/// // Here, since the second reference has been dropped, the `ArcArray`
/// // can be converted into an `Array` without cloning the data.
/// let unique: Array2<_> = a.try_into_owned_nocopy().unwrap();
/// assert_eq!(unique, array![[1., 2.], [3., 4.]]);
/// ```
pub fn try_into_owned_nocopy(self) -> Result<Array<A, D>, Self>
where
S: Data,
{
S::try_into_owned_nocopy(self)
}

/// Turn the array into a shared ownership (copy on write) array,
/// without any copying.
pub fn into_shared(self) -> ArcArray<A, D>
Expand Down