> On Jul 18, 2016, at 8:57 AM, Erica Sadun via swift-evolution
> <[email protected]> wrote:
>> On Jul 13, 2016, at 5:39 PM, Dave Abrahams via swift-evolution
>> <[email protected] <mailto:[email protected]>> wrote:
>>
>>
>> on Wed Jul 13 2016, Brent Royal-Gordon <[email protected]
>> <mailto:[email protected]>> wrote:
>>> I think grouping these into a type is a sensible approach, but I don't
>>> like that it allows the creation of meaningless MemoryLayout
>>> instances. The simplest fix would be to make `MemoryLayout` an empty
>>> enum instead of an empty struct. This would convey that no
>>> MemoryLayout instances do or can exist.
>>
>> +1.
>
> +1 as well.
If MemoryLayout were not a generic type, its instances would not necessarily be
meaningless; it could be used to lay out memory in a size + alignment-safe way.
You would need to restructure most of the API you've been talking about, though.
John.
>
> /// Accesses the memory layout of `T` through its
> /// `size`, `stride`, and `alignment` properties
> public enum MemoryLayout {
> /// Returns the contiguous memory footprint of `T`.
> ///
> /// Does not include any dynamically-allocated or "remote"
> /// storage. In particular, `MemoryLayout.size`, when
> /// `T` is a class type, is the same regardless of how many
> /// stored properties `T` has.
> public static var size: Int { return _sizeof(T.self) }
>
> /// For instances of `T` in an `Array`, returns the number of
> /// bytes from the start of one instance to the start of the
> /// next. This is the same as the number of bytes moved when an
> /// `UnsafePointer` is incremented. `T` may have a lower minimal
> /// alignment that trades runtime performance for space
> /// efficiency. The result is always positive.
> public static var stride: Int { return _strideof(T.self) }
>
> /// Returns the default memory alignment of `T`.
> public static var alignment: Int { return _alignof(T.self) }
> }
>
>
> -- E
>
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