source: MondoRescue/branches/stable/mindi-busybox/util-linux/hwclock.c

/* 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);
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;
}