From: Aaron Patterson <tenderlove@...>
Date: 2013-07-10T09:52:58+09:00
Subject: [ruby-core:55892] Re: [ruby-trunk - Feature #5138] Add nonblocking IO that does not use exceptions for EOF and EWOULDBLOCK

On Wed, Jul 10, 2013 at 09:03:19AM +0900, Eric Wong wrote:
> "tenderlovemaking (Aaron Patterson)" <aaron@tenderlovemaking.com> wrote:
> > As for Erlang style return values.  It seems interesting, but that
> > means every call to `try_read_nonblock` would allocate an array.  The
> > only possible return values would be:
> 
> I prefer to avoid the requirement for allocating _anything_ in the
> common case.  So "no" to the tuple retvals.
> 
> How about making the destination buffer a required argument,

Does this mean someone would have to pre-allocate the buffer?  For
example, the "buffer" variable below would need to be defined as:

  buffer = " " * maxlen

> and returning:
> 
> 	Integer           - length in bytes on successful read
> 	Symbol            - :wait_readable/:wait_writable (common)
> 	nil               - EOF

Is this really advantageous over:

 	String            - the buffer read in
 	Symbol            - :wait_readable/:wait_writable (common)
 	nil               - EOF

Length of bytes can be derived from buffer length.

> 
>   case ret = io.try_read(maxlen, buffer)
>   when Integer
>     process_buffer(buffer, ret)
>   when nil
>     break
>   when Symbol
>     io.__send__(ret, timeout_sec) # :wait_readable,:wait_writable
>   end while true
> 
> I think making the buffer a required argument makes sense anyways for
> performance (not just GC, but keeping the CPU cache hot regardless of
> VM/language, too).

-- 
Aaron Patterson
http://tenderlovemaking.com/