Non-blocking pipes still appear to be isBlocking

[Alan Bateman]

On 29/01/2024 22:09, Charles Oliver Nutter wrote:
> :
>
> (And yes, I know the implications for vthreads; this is for a user
> with legacy code expecting child process pipe streams to be blocking
> by default.)
>

The source/sink ends of a Pipe are selectable channels and can therefore 
be configured non-blocking. I wonder if the user's code chokes with 
usages like this:

pipe.source().configureBlocking(false);
pipe.sink().configureBlocking(false);

As regards the underlying blocking mode: It's okay for a 
SelectableChannel to implement blocking semantics when then underlying 
socket/fifo is configured non-blocking. Mostly they are the equal, 
meaning if the SelectableChannel blocking mode is true then the 
underlying socket/fifo's blocking mode is also true. For the network 
channels, the first use of a virtual thread will change the channel's 
socket to be non-blocking. The pipe channels are a bit different in that 
they eagerly change the underlying fifo to be non-blocking. Both are 
valid approaches as it's transparent to anything using the API. The pipe 
channel could be changed to work like the network channels and change it 
lazily, I think they were only done this week for expediency rather than 
anything else.

-Alan
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