[API Proposal]: Add span based apis for Array.CreateInstance/GetValue/SetValue

[afxres]

Background and motivation

Avoid extra memory allocate during reflections/serialization

API Proposal

Array.CreateInstance(Type, int[])
Array.CreateInstance(Type, int[], int[])
Array.GetValue(int[])
Array.SetValue(object, int[])
+ Array.CreateInstance(Type, Span<int>)
+ Array.CreateInstance(Type, Span<int>, Span<int>)
+ Array.GetValue(Span<int>)
+ Array.SetValue(object, Span<int>)
...

API Usage

var lengths = (stackalloc int[] { 1, 2 });
var lowerBounds = (stackalloc int[] { 3, 4 });
var array = Array.CreateInstance(typeof(int), lengths, lowerBounds);
// we can use 'MemoryMarshal.GetArrayDataReference' instead of 'GetValue/SetValue'
// but 'CreateInstance' still have to allocate extra memories
var reference = Unsafe.As<byte, int>(ref MemoryMarshal.GetArrayDataReference(array));

Alternative Designs

No response

Risks

No response

[ghost]

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Issue Details

---

Background and motivation

Avoid extra memory allocate during reflections/serialization

API Proposal

Array.CreateInstance(Type, int[])
Array.CreateInstance(Type, int[], int[])
Array.GetValue(int[])
Array.SetValue(object, int[])
+ Array.CreateInstance(Type, Span<int>)
+ Array.CreateInstance(Type, Span<int>, Span<int>)
+ Array.GetValue(Span<int>)
+ Array.SetValue(object, Span<int>)
...

API Usage

var lengths = (stackalloc int[] { 1, 2 });
var lowerBounds = (stackalloc int[] { 3, 4 });
var array = Array.CreateInstance(typeof(int), lengths, lowerBounds);
// we can use 'MemoryMarshal.GetArrayDataReference' instead of 'GetValue/SetValue'
// but 'CreateInstance' still have to allocate extra memories
var reference = Unsafe.As<byte, int>(ref MemoryMarshal.GetArrayDataReference(array));

Alternative Designs

No response

Risks

No response

Author:	afxres
Assignees:	-
Labels:	api-suggestion, area-System.Memory, untriaged
Milestone:	-

[tannergooding]

CC. @jkotas, @BruceForstall

This seems like general goodness and helps make certain type of multi-dimensional array handling "better".

However, Array is special so I wanted to confirm that there aren't any concerns or considerations that might block such functionality from being exposed.

I imagine if it is, we may want CreateInstance<T>(...) to match the other Array proposal that Jan has open.

[jkotas]

This seems like general goodness and helps make certain type of multi-dimensional array handling "better".

It makes it better, but it is not going to be by much. These APIs are still going to be slow APIs that do a lot of work even after this change.

we may want CreateInstance(...) to match the other Array proposal that Jan has open.

Do you mean #76478? There is no CreateInstance<T> in that proposal. If you know T, you can just use new T[...].

[tannergooding]

Yes, that's the one I was thinking of.

[tannergooding]

Going to close this based on the feedback above. We already have overloads that avoid allocating for the common cases of 1/2/3 lengths. For more lengths we may end up adding params Span<T> support as part of a more holistic effort when the language feature becomes available.