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/* vi: set sw=4 ts=4: */
/*
 * Mini hwclock implementation for busybox
 *
 * Copyright (C) 2002 Robert Griebl <griebl@gmx.de>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
*/

#include <sys/utsname.h>
#include <getopt.h>
#include "libbb.h"

/* Copied from linux/rtc.h to eliminate the kernel dependency */
struct linux_rtc_time {
	int tm_sec;
	int tm_min;
	int tm_hour;
	int tm_mday;
	int tm_mon;
	int tm_year;
	int tm_wday;
	int tm_yday;
	int tm_isdst;
};

#define RTC_SET_TIME   _IOW('p', 0x0a, struct linux_rtc_time) /* Set RTC time    */
#define RTC_RD_TIME    _IOR('p', 0x09, struct linux_rtc_time) /* Read RTC time   */

#if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS
# ifndef _GNU_SOURCE
#  define _GNU_SOURCE
# endif
#endif

static const char *rtcname;

static int xopen_rtc(int flags)
{
	int rtc;

	if (!rtcname) {
		rtc = open("/dev/rtc", flags);
		if (rtc >= 0)
			return rtc;
		rtc = open("/dev/rtc0", flags);
		if (rtc >= 0)
			return rtc;
		rtcname = "/dev/misc/rtc";
	}
	return xopen(rtcname, flags);
}

static time_t read_rtc(int utc)
{
	struct tm tm;
	char *oldtz = 0;
	time_t t = 0;
	int rtc = xopen_rtc(O_RDONLY);

	memset(&tm, 0, sizeof(struct tm));
	xioctl(rtc, RTC_RD_TIME, &tm);
	tm.tm_isdst = -1; /* not known */

	close(rtc);

	if (utc) {
		oldtz = getenv("TZ");
		putenv((char*)"TZ=UTC0");
		tzset();
	}

	t = mktime(&tm);

	if (utc) {
		unsetenv("TZ");
		if (oldtz)
			putenv(oldtz - 3);
		tzset();
	}
	return t;
}

static void write_rtc(time_t t, int utc)
{
	struct tm tm;
	int rtc = xopen_rtc(O_WRONLY);

	tm = *(utc ? gmtime(&t) : localtime(&t));
	tm.tm_isdst = 0;

	xioctl(rtc, RTC_SET_TIME, &tm);

	close(rtc);
}

static void show_clock(int utc)
{
	//struct tm *ptm;
	time_t t;
	char *cp;

	t = read_rtc(utc);
	//ptm = localtime(&t);  /* Sets 'tzname[]' */

	cp = ctime(&t);
	if (cp[0])
		cp[strlen(cp) - 1] = '\0';

	//printf("%s  %.6f seconds %s\n", cp, 0.0, utc ? "" : (ptm->tm_isdst ? tzname[1] : tzname[0]));
	printf("%s  0.000000 seconds\n", cp);
}

static void to_sys_clock(int utc)
{
	struct timeval tv;
	const struct timezone tz = { timezone/60 - 60*daylight, 0 };

	tv.tv_sec = read_rtc(utc);
	tv.tv_usec = 0;
	if (settimeofday(&tv, &tz))
		bb_perror_msg_and_die("settimeofday() failed");
}

static void from_sys_clock(int utc)
{
	struct timeval tv;

	gettimeofday(&tv, NULL);
	//if (gettimeofday(&tv, NULL))
	//	bb_perror_msg_and_die("gettimeofday() failed");
	write_rtc(tv.tv_sec, utc);
}

#if ENABLE_FEATURE_HWCLOCK_ADJTIME_FHS
# define ADJTIME_PATH "/var/lib/hwclock/adjtime"
#else
# define ADJTIME_PATH "/etc/adjtime"
#endif
static int check_utc(void)
{
	int utc = 0;
	FILE *f = fopen(ADJTIME_PATH, "r");

	if (f) {
		RESERVE_CONFIG_BUFFER(buffer, 128);

		while (fgets(buffer, sizeof(buffer), f)) {
			int len = strlen(buffer);

			while (len && isspace(buffer[len - 1]))
				len--;

			buffer[len] = 0;

			if (strncmp(buffer, "UTC", 3) == 0) {
				utc = 1;
				break;
			}
		}
		fclose(f);
		RELEASE_CONFIG_BUFFER(buffer);
	}
	return utc;
}

#define HWCLOCK_OPT_LOCALTIME   0x01
#define HWCLOCK_OPT_UTC         0x02
#define HWCLOCK_OPT_SHOW        0x04
#define HWCLOCK_OPT_HCTOSYS     0x08
#define HWCLOCK_OPT_SYSTOHC     0x10
#define HWCLOCK_OPT_RTCFILE     0x20

int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int hwclock_main(int argc, char **argv)
{
	unsigned opt;
	int utc;

#if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS
	static const char hwclock_longopts[] ALIGN1 =
		"localtime\0" No_argument "l"
		"utc\0"       No_argument "u"
		"show\0"      No_argument "r"
		"hctosys\0"   No_argument "s"
		"systohc\0"   No_argument "w"
		"file\0"      Required_argument "f"
		;
	applet_long_options = hwclock_longopts;
#endif
	opt_complementary = "r--ws:w--rs:s--wr:l--u:u--l";
	opt = getopt32(argv, "lurswf:", &rtcname);

	/* If -u or -l wasn't given check if we are using utc */
	if (opt & (HWCLOCK_OPT_UTC | HWCLOCK_OPT_LOCALTIME))
		utc = opt & HWCLOCK_OPT_UTC;
	else
		utc = check_utc();

	if (opt & HWCLOCK_OPT_HCTOSYS) {
		to_sys_clock(utc);
		return 0;
	}
	if (opt & HWCLOCK_OPT_SYSTOHC) {
		from_sys_clock(utc);
		return 0;
	}
	/* default HWCLOCK_OPT_SHOW */
	show_clock(utc);
	return 0;
}