From: Eric Wong <normalperson@...>
Date: 2013-07-10T10:52:26+09:00
Subject: [ruby-core:55895] Re: [ruby-trunk - Feature #5138] Add nonblocking IO that does not use exceptions for EOF and EWOULDBLOCK

Aaron Patterson <tenderlove@ruby-lang.org> wrote:
> 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

Yes, but it could just be:   buffer = ""

Ruby will internally resize the string and won't waste memory
bandwidth prefilling it with 0x20

> > 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.

It would force developers to think about buffer reuse (which helps a lot
with big copy loops).  Otherwise, it won't help for for apps which
already reuse buffers.