Improve usability of spans for outparams. #7708
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A few changes here: 1) Allow setting the size of a Span (to a value no larger than its current size). This enables use of a Span over a non-const type as an outparam that you fill with data and then set the size of the data. 2) Allow converting a Span<T> to a Span<const T>, so once you fill such a non-const-type Span with data you can pass it to functions expecting a Span over a const type without having to manually create one. 3) Change data_equal to allow comparing Span<T> to Span<const T>.
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A few changes here: 1) Allow setting the size of a Span (to a value no larger than its current size). This enables use of a Span over a non-const type as an outparam that you fill with data and then set the size of the data. 2) Allow converting a Span<T> to a Span<const T>, so once you fill such a non-const-type Span with data you can pass it to functions expecting a Span over a const type without having to manually create one. 3) Change data_equal to allow comparing Span<T> to Span<const T>.
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A few changes here:
Allow setting the size of a Span (to a value no larger than its current size). This enables use of a Span over a non-const type as an outparam that you fill with data and then set the size of the data.
Allow converting a
Span<T>to aSpan<const T>, so once you fill such a non-const-type Span with data you can pass it to functions expecting a Span over a const type without having to manually create one.Change data_equal to allow comparing
Span<T>toSpan<const T>.Problem
Hard to use Span where we want to. See #7666 (comment)
Change overview
Address the shortcomings that comment pointed out.
Testing
Some automated tests included. I also did some manual tests that various things that should not compile do not:
Span<uint8_t>().data_equal(Span<uint16_t>())MutableByteSpan s = ByteSpan()Wish we had automated ways to test "this should not compile"....