Re: [clisp-list] FFI - Creating c-places in LISP? -> READ-SOME-SEQUEN CE

[Sam S. <sd...@gn...>]

> * In message <AOE...@sy...>
> * On the subject of "RE: [clisp-list] FFI - Creating c-places in LISP? -> READ-SOME-SEQUEN CE"
> * Sent on Wed, 2 Oct 2002 08:01:08 -0700
> * Honorable "Dave Richards" <da...@sy...> writes:
>
> > The contract of the READ-*-ONCE (WRITE-*-ONCE) functions is to make a
> > single read() (write()) OS call.  They will return the number of
> > objects (bytes or characters) read (written) - just like READ-SEQUENCE
> > (WRITE-SEQUENCE).
> > If this number is smaller than the size of the SEQUENCE argument, the
> > next i/o call will either block or return EOF (i.e., no more data is
> > immediately available).
> > We can even return a second value: NIL, :EOF, or :BLOCK.
> >
> > I think this is what you want.  Am I right?
> 
> In the previous discussion about TCP-based servers, I raised the issue
> than the sockets needed to be marked non-blocking.  I thought we'd
> concluded that doing so could potentially break existing stream code.
> Did I misunderstand?  Non-blocking is required to ensure that each I/O
> only performs what is possible with no delay and that the server is
> then available to perform other work.  This is what I meant by partial
> read()s/write()s.

CMIIAW: if you have a regular blocking socket and you call read/write
on it and it has _something_, it will not block.
the only way it might block is if it has _nothing_.
So you can use the regular CLISP buffered socket streams with the
proposed WRITE-SEQUENCE-ONCE and READ-SEQUENCE-ONCE and use the second
value to decide whether the next i/o will block or not.
Alternatively you can use SOCKET-STATUS before i/o: this should be
cheap enough because you will be doing block i/o, not byte i/o.

WAIM?

-- 
Sam Steingold (http://www.podval.org/~sds) running RedHat7.3 GNU/Linux
<http://www.camera.org> <http://www.iris.org.il> <http://www.memri.org/>
<http://www.mideasttruth.com/> <http://www.palestine-central.com/links.html>
The software said it requires Windows 3.1 or better, so I installed Linux.