From: Francis Cianfrocca <garbagecat10@...>
Date: 2006-08-09T11:51:21+09:00
Subject: Re: Signaling Ruby from C/C++

Ok, Asterix, this was driving me crazy because I know I've done it 
before.

Here's some code from an early version of EventMachine. Note that this 
code is Windows-only. For Unix, you need something a little different 
(socketpair).

/*******************************************/

static int Pipe[2];

// C code called from a Ruby instance method.
// We create an instance variable of whatever object
// self is.

int sp = _pipe (Pipe, 4096, _O_BINARY);
if (sp) {
  // no pipe, handle the error somehow.
}

char buf [100];
snprintf (buf, sizeof(buf), "@rd = IO.new( %d, \"r\")", Pipe[0]);
rb_eval_string (buf);

/********************************************/

After executing this code, the object that called it has an instance 
variable named @rd which is an IO object you can select for readability 
in Ruby (or use a Ruby global if you want). The Windows program can 
write bytes to Pipe[1]. Obviously make sure Pipe isn't allocated on the 
stack, and obviously make sure you close both sides of the pipe when 
you're done with it.

Also, be very wary that _pipe produces a half-duplex pipe in Windows! 
Unlike some Unix flavors, you may not write Pipe[0] and you may not read 
Pipe[1]. If you do, you'll get bizarre errors.

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