/* 
   Unix SMB/CIFS implementation.

   common events code for signal events

   Copyright (C) Andrew Tridgell	2007
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"
#include "system/filesys.h"
#include "system/select.h"
#include "lib/util/dlinklist.h"
#include "lib/events/events.h"
#include "lib/events/events_internal.h"

#define NUM_SIGNALS 64

/*
  the poor design of signals means that this table must be static global
*/
static struct {
	struct signal_event *sig_handlers[NUM_SIGNALS];
	uint32_t signal_count[NUM_SIGNALS];
	uint32_t got_signal;
	int pipe_hack[2];
} sig_state;


/*
  signal handler - redirects to registered signals
*/
static void signal_handler(int signum)
{
	char c = 0;
	sig_state.signal_count[signum]++;
	sig_state.got_signal++;
	/* doesn't matter if this pipe overflows */
	write(sig_state.pipe_hack[1], &c, 1);
}


/*
  destroy a signal event
*/
static int signal_event_destructor(struct signal_event *se)
{
	se->event_ctx->num_signal_handlers--;
	DLIST_REMOVE(sig_state.sig_handlers[se->signum], se);
	if (sig_state.sig_handlers[se->signum] == NULL) {
		signal(se->signum, SIG_DFL);
	}
	return 0;
}

/*
  this is part of the pipe hack needed to avoid the signal race condition
*/
static void signal_pipe_handler(struct event_context *ev, struct fd_event *fde, 
				uint16_t flags, void *private)
{
	char c[16];
	/* its non-blocking, doesn't matter if we read too much */
	read(sig_state.pipe_hack[0], c, sizeof(c));
}

/*
  add a signal event
  return NULL on failure (memory allocation error)
*/
struct signal_event *common_event_add_signal(struct event_context *ev, 
					    TALLOC_CTX *mem_ctx,
					    int signum,
					    event_signal_handler_t handler, 
					    void *private_data) 
{
	struct signal_event *se;

	if (signum >= NUM_SIGNALS) {
		return NULL;
	}

	se = talloc(mem_ctx?mem_ctx:ev, struct signal_event);
	if (se == NULL) return NULL;

	se->event_ctx		= ev;
	se->handler		= handler;
	se->private_data	= private_data;
	se->signum              = signum;

	if (sig_state.sig_handlers[signum] == NULL) {
		signal(signum, signal_handler);
	}

	DLIST_ADD(sig_state.sig_handlers[signum], se);

	talloc_set_destructor(se, signal_event_destructor);

	if (ev->pipe_fde == NULL) {
		if (sig_state.pipe_hack[0] == 0 && 
		    sig_state.pipe_hack[1] == 0) {
			pipe(sig_state.pipe_hack);
			set_blocking(sig_state.pipe_hack[0], False);
			set_blocking(sig_state.pipe_hack[1], False);
		}
		ev->pipe_fde = event_add_fd(ev, ev, sig_state.pipe_hack[0],
					    EVENT_FD_READ, signal_pipe_handler, NULL);
	}
	ev->num_signal_handlers++;

	return se;
}


/*
  check if a signal is pending
  return != 0 if a signal was pending
*/
int common_event_check_signal(struct event_context *ev)
{
	int i;
	if (sig_state.got_signal == 0) {
		return 0;
	}
	
	for (i=0;i<NUM_SIGNALS+1;i++) {
		uint32_t count = sig_state.signal_count[i];
		if (count != 0) {
			struct signal_event *se, *next;
			for (se=sig_state.sig_handlers[i];se;se=next) {
				next = se->next;
				se->handler(ev, se, i, count, se->private_data);
			}
			sig_state.signal_count[i] -= count;
			sig_state.got_signal -= count;
		}
	}

	return 1;
}