replace MyStd{in|out}Stream with shareable streams
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`MyStd{in|out}Stream` were written based on the assumption that
`Std{in|out}Stream::stream` would only ever be called once. Turns out that's
not true for guest components which are composed of multiple subcomponents,
since each subcomponent will potentially want its own handle, so they need to be
shareable. The easiest way to do that is provide cloneable implementations of
`Host{In|Out}putStream` which operate synchronously.
Note that this amounts to doing synchronous I/O in an asynchronous context,
which we'd normally prefer to avoid, but the properly asynchronous
implementations `Host{In|Out}putStream` based on `AsyncRead`/`AsyncWrite` are
quite hairy and probably not worth it for "normal" stdio streams in Spin. If
this does prove to be a performance bottleneck, though, we can certainly revisit
it.
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
lann
approved these changes
Oct 27, 2023
fibonacci1729
approved these changes
Oct 27, 2023
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MyStd{in|out}Streamwere written based on the assumption thatStd{in|out}Stream::streamwould only ever be called once. Turns out that's not true for guest components which are composed of multiple subcomponents, since each subcomponent will potentially want its own handle, so they need to be shareable. The easiest way to do that is provide cloneable implementations ofHost{In|Out}putStreamwhich operate synchronously.Note that this amounts to doing synchronous I/O in an asynchronous context, which we'd normally prefer to avoid, but the properly asynchronous implementations
Host{In|Out}putStreambased onAsyncRead/AsyncWriteare quite hairy and probably not worth it for "normal" stdio streams in Spin. If this does prove to be a performance bottleneck, though, we can certainly revisit it.