/*-
 * Copyright (c) 2008 Robert N. M. Watson
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/mman.h>
#include <sys/time.h>

#include <err.h>
#include <fcntl.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

#include "/zoo/kris/contention/dev/evilmem/evilmem.h"

/*
 * Small wrapper library to substitute implementations of gettimeofday(2) and
 * time(3) with lower resolution variations.  time(3) is unconditionally
 * degraded, since it will return a truncated time anyway.  gettimeofday(3)
 * checks the TIMEWRAPPER environmental variable, which can be set to either
 * "PRECISE" or "FAST".
 */

static int		timewrapper_initialized;
static clockid_t	timewrapper_clock;

/*
 * Select whatever system default is present for CLOCK_REALTIME as the
 * default if the environmental variable is unset, or set to an invalid
 * value.
 */
#define	TIMEWRAPPER_ENV		"TIMEWRAPPER"
#define	TIMEWRAPPER_DEFAULT	CLOCK_REALTIME
#define	TIMEWRAPPER_STRPRECISE	"PRECISE"
#define	TIMEWRAPPER_STRFAST	"FAST"

static struct evilmem *evilm;

static void
timewrapper_initialize(void)
{
	const char *whichclock_env;
	int em_fd;


#if 0
	whichclock_env = getenv(TIMEWRAPPER_ENV);
	if (whichclock_env == NULL) {
		timewrapper_clock = TIMEWRAPPER_DEFAULT;
		timewrapper_initialized = 1;
		return;
	}

	if (strcmp(whichclock_env, TIMEWRAPPER_STRPRECISE) == 0)
		timewrapper_clock = CLOCK_REALTIME_PRECISE;
	else if (strcmp(whichclock_env, TIMEWRAPPER_STRFAST) == 0)
		timewrapper_clock = CLOCK_REALTIME_FAST;
	else
		timewrapper_clock = TIMEWRAPPER_DEFAULT;
#endif
	timewrapper_clock = CLOCK_REALTIME_FAST;
	timewrapper_initialized = 1;

	em_fd = open("/dev/evilmem", O_RDONLY);
	if (em_fd < 0)
		err(-1, "open: evilmem");

	/* XXXRW: Should have an ioctl to request page size for evilmem. */
	evilm = mmap(NULL, getpagesize(), PROT_READ, MAP_SHARED, em_fd, 0);
	if (evilm == MAP_FAILED)
		err(-1, "mmap");
	close(em_fd);
}

int
gettimeofday(struct timeval *tp, struct timezone *tzp)
{
	struct timespec ts;

	if (!timewrapper_initialized)
		timewrapper_initialize();

	/*
	 * XXXRW: Not ideal, since returning EINVAL from gettimeofday() isn't
	 * expected.  Fall back to the gettimeofday() system call instead?
	 */
	if (evil_gettime(&ts) < 0)
		return (-1);

	tp->tv_sec = ts.tv_sec;
	tp->tv_usec = ts.tv_nsec / 1000;

	return (0);
}

time_t
time(time_t *tloc)
{
	struct timespec ts;

	if (clock_gettime(CLOCK_SECOND, &ts) < 0) {
		if (tloc != NULL)
			*tloc = -1;
		return (-1);
	}

	if (tloc != NULL)
		*tloc = ts.tv_sec;

	return (ts.tv_sec);
}


int
evil_gettime(struct timespec *ts)
{
	int em_generation_before, em_generation_after;

	if (evilm->em_magic != EVILMEM_MAGIC)
		errx(-1, "evilmem magic");
	do {
		em_generation_before = evilm->em_generation_before;
		ts->tv_sec = evilm->em_time.tv_sec;
		ts->tv_nsec = evilm->em_time.tv_nsec;
		em_generation_after = evilm->em_generation_after;
	} while (em_generation_before != em_generation_after);

	return(0);
}

#if 0
		em_ts = evilm->em_time;
	if (clock_gettime(CLOCK_REALTIME, &syscall_ts) < 0)
		err(-1, "clock_gettime");

	printf("evilmem: %jd.%08jd\n", (intmax_t)em_ts.tv_sec,
	    (intmax_t)em_ts.tv_nsec);
	printf("syscall: %jd.%08jd\n", (intmax_t)syscall_ts.tv_sec,
	    (intmax_t)syscall_ts.tv_nsec);
	return (0);
}

#endif