[BRLTTY] brlapi freeze under Windows

[James Teh]

On 23/09/2008 11:21 AM, James Teh wrote:
> 1. Initialise brlapi.
> 2. Write some text to the display, just to ensure all is working.
> 3. Press a key on the display.
> 4. Write some more text to the display without first calling
> readKey(False). This call will block.
Further investigation reveals that the brlapi server (i.e. brltty 
itself) blocks in step 3; i.e. when the key is pressed. I can determine 
this because I cannot stop the brlapi service; brltty never responds to 
the service termination request.

I suspect it is blocking when it tries to write the key to the client. I 
don't quite understand the code yet, but am I right in assuming that it 
relies on the behaviour of Unix sockets whereby a certain amount of data 
can be written (buffered) without the write operation blocking? I am not 
certain, but perhaps this is different with local named pipes in 
Windows; i.e. perhaps they block on the write operation waiting for the 
remote end to read the data. MSDN mentions a FILE_FLAG_WRITE_THROUGH 
mode for network named pipes which causes this behaviour, but it says it 
doesn't apply to local named pipes. It is unclear as to whether it is 
just always enabled for local named pipes (no buffering), which I 
suspect is the case.

Jamie

-- 
James Teh
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