Re: [clisp-list] proposed modifications to SOCKET-STATUS

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

> * In message <159...@is...>
> * On the subject of "Re: [clisp-list] proposed modifications to SOCKET-STATUS"
> * Sent on Tue, 28 Jan 2003 21:38:14 -0800
> * Honorable don...@is... (Don Cohen) writes:
>
>  > > Could you please tell us what those new values mean?
>  > 
>  > :ERROR: next i/o will generate an error
>  > :INPUT: only input is possible (or requested)
>  > :OUTPUT: only output is possible (or requested)
>  > :IO: both input and output are possible
>  > :EOF: input --> EOF, output impossible or not requested
>  > :APPEND: output possible, input --> EOF
>  > :WAIT: both output & input --> hang (or not requested)
> 
> What's this requested stuff?

see <http://clisp.cons.org/impnotes/socket.html#so-status>,
specifically the table "Possible values of socket-stream-or-list".

> Under what circumstance would io cause an error?

see select(2), "exceptfds".

> So, if I understand, input can do three things:
>  - wait
>  - eof
>  - return immediately with "real" input
> whereas output can only do 2:
>  - wait
>  - return immediately 

it can also signal an error if the other side has closed the
connection, but I don't know how to check for this.

> You call these
> 
> 		input
> 	  	wait	real	eof
>  output	      +-------------------------
> 	return| output	io	append
> 	 wait |	wait	input	eof
> 
> It seems to me that you might want another row for output when 
> the output direction has been closed.  In that case I guess output
> would give an error?

yes, almost:

[7]> (format o "foo")
NIL
[8]> (format o "foo~%")

[stream.d:13629] 
*** - UNIX error 32 (EPIPE): Broken pipe, child process terminated or socket closed
1. Break [9]> 


i.e., the error is only after a NL.

how do I check for this?


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