/*
 * Copyright (c) 2006 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

#include <errno.h>
#include <libkern/OSMemoryNotification.h>
#include <mach/mach.h>
#include <notify.h>
#include <stdlib.h>
#include <sys/time.h>

const char *kOSMemoryNotificationName = "com.apple.system.memorystatus";

struct _OSMemoryNotification {
	int token;
	mach_port_t port;
};

int
OSMemoryNotificationCreate(OSMemoryNotificationRef *note)
{
	OSMemoryNotificationRef ref = malloc(sizeof(struct _OSMemoryNotification));

	if (NULL == ref) {
		return ENOMEM;
	}
	
	if (NOTIFY_STATUS_OK != notify_register_mach_port(kOSMemoryNotificationName, &ref->port, 0, &ref->token))
		return ENOMEM;

	*note = ref;

	return 0;
}

int
OSMemoryNotificationDestroy(OSMemoryNotificationRef note)
{
	if (NOTIFY_STATUS_OK != notify_cancel(note->token))
		return EINVAL;

	if (KERN_SUCCESS != mach_port_deallocate(mach_task_self(), note->port))
		return EINVAL;

	free(note);

	return 0;
}
		
int
OSMemoryNotificationWait(OSMemoryNotificationRef note, OSMemoryNotificationLevel *level)
{

	return OSMemoryNotificationTimedWait(note, level, NULL);
}

static mach_msg_timeout_t
abs_to_timeout(const struct timeval *abstime)
{
	struct timeval rel, now;

	gettimeofday(&now, NULL);

	rel.tv_usec = abstime->tv_usec - now.tv_usec;
	rel.tv_sec = abstime->tv_sec - now.tv_sec;
	if (rel.tv_usec < 0) {
		rel.tv_usec += 1000000;
		rel.tv_sec--;
	}
	if (((int)rel.tv_sec < 0) || ((rel.tv_sec == 0) && (rel.tv_usec == 0))) {
		return 0;
	}
	return rel.tv_sec * 1000 + rel.tv_usec / 1000;
}

int
OSMemoryNotificationTimedWait(OSMemoryNotificationRef note, OSMemoryNotificationLevel *level, const struct timeval *abstime)
{
	mach_msg_empty_rcv_t msg = {{0}};
	mach_msg_return_t ret;
	uint64_t val;

	if (abstime) {
		mach_msg_timeout_t timeout = abs_to_timeout(abstime);

		if (0 == timeout)
			return ETIMEDOUT;

		ret = mach_msg(&msg.header, MACH_RCV_MSG | MACH_RCV_TIMEOUT, 0, sizeof msg, note->port, timeout, MACH_PORT_NULL);

		if (MACH_RCV_TIMED_OUT == ret) {
			return ETIMEDOUT;
		} 
	} else {
		ret = mach_msg(&msg.header, MACH_RCV_MSG, 0, sizeof msg, note->port, MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
	}

	if (MACH_MSG_SUCCESS != ret)
		return EINVAL;

	if (NOTIFY_STATUS_OK != notify_get_state(note->token, &val))
		return EINVAL;

	*level = (OSMemoryNotificationLevel)val;

	return 0;
}

OSMemoryNotificationLevel OSMemoryNotificationCurrentLevel(void)
{
	uint64_t val;
	int token;

	if (NOTIFY_STATUS_OK != notify_register_check(kOSMemoryNotificationName, &token))
		return OSMemoryNotificationLevelAny;

	if (NOTIFY_STATUS_OK != notify_get_state(token, &val))
		return OSMemoryNotificationLevelAny;

	if (NOTIFY_STATUS_OK != notify_cancel(token))
		return OSMemoryNotificationLevelAny;

	return (OSMemoryNotificationLevel)val;
}