> On Oct 14, 2017, at 10:29, Braden Scothern via swift-users
> <swift-users@swift.org> wrote:
>
> There is a lot of value in these being mutating functions when working with C
> APIs that need a buffer for it to write to.
>
> If you have a collection and ensure it had allocated it's memory, you can
> then have the C API write directly into the collection's storage avoiding
> extra copy operations.
>
> I personally take advantage of this a lot. Because I'm wrapping a C library
> in Swift as part of my work.
>
> If this was changed to only non mutating functions, it still wouldn't be able
> to guarantee that the buffer isn't mutating the collection without always
> doing a deep copy. It is very easy to go from an UnsafeBufferPointer ->
> UnsafeMutableBufferPointer and have people change things.
The types wouldn’t change, just whether the method is marked `mutating`.
The reason I have doubts whether it’s worth it is that even if the
implementation gets duplicated as non-mutating, it won’t prevent cases where a
{*}BufferPointer needs to be a var: whenever it is passed into a generic
MutableCollection context, it will need to be a var in order to be usable.
Is it worth it?
Cheers,
Guillaume Lessard
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