/* 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 source tree.
*/

#include "libbb.h"
/* After libbb.h, since it needs sys/types.h on some systems */
#include <sys/utsname.h>
#include "rtc_.h"

/* diff code is disabled: it's not sys/hw clock diff, it's some useless
 * "time between hwclock was started and we saw CMOS tick" quantity.
 * It's useless since hwclock is started at a random moment,
 * thus the quantity is also random, useless. Showing 0.000000 does not
 * deprive us from any useful info.
 *
 * SHOW_HWCLOCK_DIFF code in this file shows the difference between system
 * and hw clock. It is useful, but not compatible with standard hwclock.
 * Thus disabled.
 */
#define SHOW_HWCLOCK_DIFF 0


#if !SHOW_HWCLOCK_DIFF
# define read_rtc(pp_rtcname, sys_tv, utc) read_rtc(pp_rtcname, utc)
#endif
static time_t read_rtc(const char **pp_rtcname, struct timeval *sys_tv, int utc)
{
        struct tm tm_time;
        int fd;

        fd = rtc_xopen(pp_rtcname, O_RDONLY);

        rtc_read_tm(&tm_time, fd);

#if SHOW_HWCLOCK_DIFF
        {
                int before = tm_time.tm_sec;
                while (1) {
                        rtc_read_tm(&tm_time, fd);
                        gettimeofday(sys_tv, NULL);
                        if (before != (int)tm_time.tm_sec)
                                break;
                }
        }
#endif

        if (ENABLE_FEATURE_CLEAN_UP)
                close(fd);

        return rtc_tm2time(&tm_time, utc);
}

static void show_clock(const char **pp_rtcname, int utc)
{
#if SHOW_HWCLOCK_DIFF
        struct timeval sys_tv;
#endif
        time_t t = read_rtc(pp_rtcname, &sys_tv, utc);

#if ENABLE_LOCALE_SUPPORT
        /* Standard hwclock uses locale-specific output format */
        char cp[64];
        struct tm *ptm = localtime(&t);
        strftime(cp, sizeof(cp), "%c", ptm);
#else
        char *cp = ctime(&t);
        chomp(cp);
#endif

#if !SHOW_HWCLOCK_DIFF
        printf("%s  0.000000 seconds\n", cp);
#else
        {
                long diff = sys_tv.tv_sec - t;
                if (diff < 0 /*&& tv.tv_usec != 0*/) {
                        /* Why we need diff++? */
                        /* diff >= 0 is ok: | diff < 0, can't just use tv.tv_usec: */
                        /*   45.520820      |   43.520820 */
                        /* - 44.000000      | - 45.000000 */
                        /* =  1.520820      | = -1.479180, not -2.520820! */
                        diff++;
                        /* Should be 1000000 - tv.tv_usec, but then we must check tv.tv_usec != 0 */
                        sys_tv.tv_usec = 999999 - sys_tv.tv_usec;
                }
                printf("%s  %ld.%06lu seconds\n", cp, diff, (unsigned long)sys_tv.tv_usec);
        }
#endif
}

static void to_sys_clock(const char **pp_rtcname, int utc)
{
        struct timeval tv;
        struct timezone tz;

        tz.tz_minuteswest = timezone/60;
        /* ^^^ used to also subtract 60*daylight, but it's wrong:
         * daylight!=0 means "this timezone has some DST
         * during the year", not "DST is in effect now".
         */
        tz.tz_dsttime = 0;

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

static void from_sys_clock(const char **pp_rtcname, int utc)
{
#if 1
        struct timeval tv;
        struct tm tm_time;
        int rtc;

        rtc = rtc_xopen(pp_rtcname, O_WRONLY);
        gettimeofday(&tv, NULL);
        /* Prepare tm_time */
        if (sizeof(time_t) == sizeof(tv.tv_sec)) {
                if (utc)
                        gmtime_r((time_t*)&tv.tv_sec, &tm_time);
                else
                        localtime_r((time_t*)&tv.tv_sec, &tm_time);
        } else {
                time_t t = tv.tv_sec;
                if (utc)
                        gmtime_r(&t, &tm_time);
                else
                        localtime_r(&t, &tm_time);
        }
#else
/* Bloated code which tries to set hw clock with better precision.
 * On x86, even though code does set hw clock within <1ms of exact
 * whole seconds, apparently hw clock (at least on some machines)
 * doesn't reset internal fractional seconds to 0,
 * making all this a pointless excercise.
 */
        /* If we see that we are N usec away from whole second,
         * we'll sleep for N-ADJ usecs. ADJ corrects for the fact
         * that CPU is not infinitely fast.
         * On infinitely fast CPU, next wakeup would be
         * on (exactly_next_whole_second - ADJ). On real CPUs,
         * this difference between current time and whole second
         * is less than ADJ (assuming system isn't heavily loaded).
         */
        /* Small value of 256us gives very precise sync for 2+ GHz CPUs.
         * Slower CPUs will fail to sync and will go to bigger
         * ADJ values. qemu-emulated armv4tl with ~100 MHz
         * performance ends up using ADJ ~= 4*1024 and it takes
         * 2+ secs (2 tries with successively larger ADJ)
         * to sync. Even straced one on the same qemu (very slow)
         * takes only 4 tries.
         */
#define TWEAK_USEC 256
        unsigned adj = TWEAK_USEC;
        struct tm tm_time;
        struct timeval tv;
        int rtc = rtc_xopen(pp_rtcname, O_WRONLY);

        /* Try to catch the moment when whole second is close */
        while (1) {
                unsigned rem_usec;
                time_t t;

                gettimeofday(&tv, NULL);

                t = tv.tv_sec;
                rem_usec = 1000000 - tv.tv_usec;
                if (rem_usec < adj) {
                        /* Close enough */
 small_rem:
                        t++;
                }

                /* Prepare tm_time from t */
                if (utc)
                        gmtime_r(&t, &tm_time); /* may read /etc/xxx (it takes time) */
                else
                        localtime_r(&t, &tm_time); /* same */

                if (adj >= 32*1024) {
                        break; /* 32 ms diff and still no luck?? give up trying to sync */
                }

                /* gmtime/localtime took some time, re-get cur time */
                gettimeofday(&tv, NULL);

                if (tv.tv_sec < t /* we are still in old second */
                 || (tv.tv_sec == t && tv.tv_usec < adj) /* not too far into next second */
                ) {
                        break; /* good, we are in sync! */
                }

                rem_usec = 1000000 - tv.tv_usec;
                if (rem_usec < adj) {
                        t = tv.tv_sec;
                        goto small_rem; /* already close to next sec, don't sleep */
                }

                /* Try to sync up by sleeping */
                usleep(rem_usec - adj);

                /* Jump to 1ms diff, then increase fast (x2): EVERY loop
                 * takes ~1 sec, people won't like slowly converging code here!
                 */
        //bb_error_msg("adj:%d tv.tv_usec:%d", adj, (int)tv.tv_usec);
                if (adj < 512)
                        adj = 512;
                /* ... and if last "overshoot" does not look insanely big,
                 * just use it as adj increment. This makes convergence faster.
                 */
                if (tv.tv_usec < adj * 8) {
                        adj += tv.tv_usec;
                        continue;
                }
                adj *= 2;
        }
        /* Debug aid to find "optimal" TWEAK_USEC with nearly exact sync.
         * Look for a value which makes tv_usec close to 999999 or 0.
         * For 2.20GHz Intel Core 2: optimal TWEAK_USEC ~= 200
         */
        //bb_error_msg("tv.tv_usec:%d", (int)tv.tv_usec);
#endif

        tm_time.tm_isdst = 0;
        xioctl(rtc, RTC_SET_TIME, &tm_time);

        if (ENABLE_FEATURE_CLEAN_UP)
                close(rtc);
}

/*
 * At system boot, kernel may set system time from RTC,
 * but it knows nothing about timezones. If RTC is in local time,
 * then system time is wrong - it is offset by timezone.
 * This option corrects system time if RTC is in local time,
 * and (always) sets in-kernel timezone.
 *
 * This is an alternate option to --hctosys that does not read the
 * hardware clock.
 */
static void set_system_clock_timezone(int utc)
{
        struct timeval tv;
        struct tm *broken;
        struct timezone tz;

        gettimeofday(&tv, NULL);
        broken = localtime(&tv.tv_sec);
        tz.tz_minuteswest = timezone / 60;
        if (broken->tm_isdst > 0)
                tz.tz_minuteswest -= 60;
        tz.tz_dsttime = 0;
        gettimeofday(&tv, NULL);
        if (!utc)
                tv.tv_sec += tz.tz_minuteswest * 60;
        if (settimeofday(&tv, &tz))
                bb_perror_msg_and_die("settimeofday");
}

//usage:#define hwclock_trivial_usage
//usage:        IF_FEATURE_HWCLOCK_LONG_OPTIONS(
//usage:       "[-r|--show] [-s|--hctosys] [-w|--systohc] [-t|--systz]"
//usage:       " [-l|--localtime] [-u|--utc]"
//usage:       " [-f|--rtc FILE]"
//usage:        )
//usage:        IF_NOT_FEATURE_HWCLOCK_LONG_OPTIONS(
//usage:       "[-r] [-s] [-w] [-t] [-l] [-u] [-f FILE]"
//usage:        )
//usage:#define hwclock_full_usage "\n\n"
//usage:       "Query and set hardware clock (RTC)\n"
//usage:     "\n        -r      Show hardware clock time"
//usage:     "\n        -s      Set system time from hardware clock"
//usage:     "\n        -w      Set hardware clock from system time"
//usage:     "\n        -t      Set in-kernel timezone, correct system time"
//usage:     "\n                if hardware clock is in local time"
//usage:     "\n        -u      Assume hardware clock is kept in UTC"
//usage:     "\n        -l      Assume hardware clock is kept in local time"
//usage:     "\n        -f FILE Use specified device (e.g. /dev/rtc2)"

#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_SYSTZ       0x20
#define HWCLOCK_OPT_RTCFILE     0x40

int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int hwclock_main(int argc UNUSED_PARAM, char **argv)
{
        const char *rtcname = NULL;
        unsigned opt;
        int utc;

#if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS
        static const char hwclock_longopts[] ALIGN1 =
                "localtime\0" No_argument "l" /* short opt is non-standard */
                "utc\0"       No_argument "u"
                "show\0"      No_argument "r"
                "hctosys\0"   No_argument "s"
                "systohc\0"   No_argument "w"
                "systz\0"     No_argument "t" /* short opt is non-standard */
                "rtc\0"       Required_argument "f"
                ;
        applet_long_options = hwclock_longopts;
#endif

        /* Initialize "timezone" (libc global variable) */
        tzset();

        opt_complementary = "r--wst:w--rst:s--wrt:t--rsw:l--u:u--l";
        opt = getopt32(argv, "lurswtf:", &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 = rtc_adjtime_is_utc();

        if (opt & HWCLOCK_OPT_HCTOSYS)
                to_sys_clock(&rtcname, utc);
        else if (opt & HWCLOCK_OPT_SYSTOHC)
                from_sys_clock(&rtcname, utc);
        else if (opt & HWCLOCK_OPT_SYSTZ)
                set_system_clock_timezone(utc);
        else
                /* default HWCLOCK_OPT_SHOW */
                show_clock(&rtcname, utc);

        return 0;
}