Remove Memory(::ByteData) constructor

[nhz2]

Fixes #211

TranscodingStreams.jl/src/TranscodingStreams.jl

Line 8 in 8fdabed

const ByteData = Union{Vector{UInt8},Base.CodeUnits{UInt8}}

This may cause issues as CodeUnits may not be stored densely in memory.
Ref: JuliaLang/julia#54002

[mkitti]

This looks like a breaking change. Could we deprecate the use of ByteData before we remove it?

[nhz2]

This is a bug fix. It isn't possible to turn a general CodeUnits into a Memory. Is there any not already buggy code this would break?

[jakobnissen]

The constructor is unused in the codebase, unexported, and explicitly mentioned to be internal in the documentation. I would rather see that constructor completely removed.

[jakobnissen]

IMO, remove this constructor completely, also from the docs. Make the user pass in a pointer themselves if they need this type.

[mkitti]

I agree with the change. Possibly agree with removing the constructor. How is Memory usually constructed?

[nhz2]

To remove the Memory(::Vector{UInt8}) constructor, https://github.com/JuliaIO/CodecLz4.jl/blob/55c2c423f8b757f2325dc83dd5473107375f823c/test/frame_compression.jl#L55-L56 would need to be updated. Though I agree that this should be removed, it already caused some issues, Ref: JuliaIO/CodecLz4.jl#47

Memory is usually constructed with Memory(ptr::Ptr{UInt8}, size::UInt)

[mkitti]

While I agree with @jakobnissen that there is a more fundamental issue, I think this pull request can go through to advance things in the right direction. I suspect that we will need a more fundamental refactoring here to eliminate free pointers hanging around.

I'm deprecating for now to avoid compatibility issues. I'll remove completely in the next breaking release.