How to get the base array from an `ArraySlice`?

Using Swift
1

Slice and Substring have a convenient base property, which is useful for getting access to the whole collection, but ArraySlice seems to have this functionality omitted. Is this intentional? Is it possible to get the whole array from an ArraySlice?

7 Likes
2 
extension ArraySlice {
    var horribleBase: Array<Element> { 
        unsafeBitCast(_owner!, to: Array<Element>.self) 
    }
}

:sweat_smile:

6 Likes
3

A suggestion:

extension ArraySlice {
-    var horribleBase: Array<Element> { 
+    var b͇͇ͭͥă̻̭̺͚̝̿̂ͦ́s̮̫ͪ̈e̎̾ͨ̂ͧ̓͑: Array<Element> {
        unsafeBitCast(_owner!, to: Array<Element>.self) 
    }
}
15 Likes
4

is the unsafeBitCast needed? _owner is AnyObject? so can we just use as!?

5 
let xs = [1, 2, 3]
let ys = xs[...]
let zs = ys._owner as? [Int] // 🛑 EXC_BAD_ACCESS

:sweat_smile:

1 Like
6

It's an instance of _ContiguousArrayStorage<Int>.

The unsafeBitCast only works because it happens that Array is just a struct wrapper around a _ContiguousArrayStorage or one of the other storage back ends (IIRC, don't quote me, check the source for yourself)

1 Like
7

Is this useful?
If it is useful should it be public API?

8

@tera I believe it is, which is why I asked. I'm working on code that generically uses a subsequence to "frame" it in its broader collection. It works great for strings via Substring, and other sequences that use Slice, but no such love for ArraySlice.

2 Likes