From: noer AT cygnus DOT com (Geoffrey Noer)
Subject: Re: pty code
9 Feb 1998 14:51:51 -0800
Message-ID: <199802092250.OAA12929.cygnus.cygwin32.developers@rtl.cygnus.com>
References: <199802092111 DOT QAA06948 AT subrogation DOT cygnus DOT com>
Reply-To: cygwin32-developers AT cygnus DOT com
Content-Type: text
To: cygwin32-developers AT cygnus DOT com

Ian Lance Taylor wrote:
> 
> I figured out a simple way to make Sergey's code work with ptys--the
> code which calls stat before opening the slave.  I'm going to check
> this in.
> 
> Sergey suggested another approach: have the slave write a bunch of
> characters when closing, enough to wake up any read, and then have the
> read check whether the slave was closed.  I haven't been able to think
> of a way to make that work in any manner that I find satisfactorily
> reliable.  We can't really assume anything about the data which comes
> from the slave.  We have to make sure that the master reads the last
> few bytes the slave wrote before closing the pty.
> 
> Ian

OK, FYI, I'm probably going to be checking in the following patch
from Sergey relatively soon.  I don't think it conflicts...

Geoffr



The following patch implements non-blocking read on all types of file
handles (it's neccessary to have X-window and tty versions of Xemacs
up and
running with cygwin) and contains some bug fixes.

fhandler.cc    (fhandler_base::fhandler_base): initialize openflags_
variable.

hinfo.cc        (hinfo_vec::not_open): fixed a bug in checking open
fd's
range.

select.cc        (cygwin32_select): restore fd sets if select() call
was
interrupted by a signal.

syscalls.cc    include sys/socket.h
                    (_read): if non-blocking i/o is set, check for
data
availability by calling cygwin32_select() with a zero timeout,
                    set ERRNO to EAGAIN and return -1 if no data is
available.

tty.cc            (fhandler_pty_master::read): removed a check for
data
availability if non-blocking i/o is set.

winsup.h        prototype for select_init() removed, prototype for
cygwin32_select() added.


-- 
Geoffrey Noer
noer AT cygnus DOT com