/*
 * tclUnixTime.c --
 *
 *	Contains Unix specific versions of Tcl functions that obtain time
 *	values from the operating system.
 *
 * Copyright (c) 1995 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 */

#include "tclInt.h"
#include "tclPort.h"
#include <locale.h>
#define TM_YEAR_BASE 1900
#define IsLeapYear(x)	(((x)%4 == 0) && ((x)%100 != 0 || (x)%400 == 0))

/*
 * TclpGetDate is coded to return a pointer to a 'struct tm'. For thread
 * safety, this structure must be in thread-specific data. The 'tmKey'
 * variable is the key to this buffer.
 */

static Tcl_ThreadDataKey tmKey;
typedef struct ThreadSpecificData {
    struct tm gmtime_buf;
    struct tm localtime_buf;
} ThreadSpecificData;

/*
 * If we fall back on the thread-unsafe versions of gmtime and localtime, use
 * this mutex to try to protect them.
 */

TCL_DECLARE_MUTEX(tmMutex)

static char *lastTZ = NULL;	/* Holds the last setting of the TZ
				 * environment variable, or an empty string if
				 * the variable was not set. */

/*
 * Static functions declared in this file.
 */

static void SetTZIfNecessary _ANSI_ARGS_((void));
static void CleanupMemory _ANSI_ARGS_((ClientData));

/*
 *----------------------------------------------------------------------
 *
 * TclpGetSeconds --
 *
 *	This procedure returns the number of seconds from the epoch. On most
 *	Unix systems the epoch is Midnight Jan 1, 1970 GMT.
 *
 * Results:
 *	Number of seconds from the epoch.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

unsigned long
TclpGetSeconds()
{
    return time((time_t *) NULL);
}

/*
 *----------------------------------------------------------------------
 *
 * TclpGetClicks --
 *
 *	This procedure returns a value that represents the highest resolution
 *	clock available on the system. There are no garantees on what the
 *	resolution will be. In Tcl we will call this value a "click". The
 *	start time is also system dependant.
 *
 * Results:
 *	Number of clicks from some start time.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

unsigned long
TclpGetClicks()
{
    unsigned long now;

#ifdef NO_GETTOD
    struct tms dummy;
#else
    struct timeval date;
#endif

#ifdef NO_GETTOD
    now = (unsigned long) times(&dummy);
#else
    gettimeofday(&date, NULL);
    now = date.tv_sec*1000000 + date.tv_usec;
#endif

    return now;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpGetTimeZone --
 *
 *	Determines the current timezone. The method varies wildly between
 *	different platform implementations, so its hidden in this function.
 *
 * Results:
 *	The return value is the local time zone, measured in minutes away from
 *	GMT (-ve for east, +ve for west).
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
TclpGetTimeZone(currentTime)
    Tcl_WideInt currentTime;
{
    int timeZone;

    /*
     * We prefer first to use the time zone in "struct tm" if the structure
     * contains such a member. Following that, we try to locate the external
     * 'timezone' variable and use its value. If both of those methods fail,
     * we attempt to convert a known time to local time and use the difference
     * from UTC as the local time zone. In all cases, we need to undo any
     * Daylight Saving Time adjustment.
     */

#if defined(HAVE_TM_TZADJ)
#define TCL_GOT_TIMEZONE
    /*
     * Struct tm contains tm_tzadj - that value may be used.
     */

    time_t curTime = (time_t) currentTime;
    struct tm *timeDataPtr = TclpLocaltime((TclpTime_t) &curTime);

    timeZone = timeDataPtr->tm_tzadj / 60;
    if (timeDataPtr->tm_isdst) {
	timeZone += 60;
    }
#endif

#if defined(HAVE_TM_GMTOFF) && !defined (TCL_GOT_TIMEZONE)
#define TCL_GOT_TIMEZONE
    /*
     * Struct tm contains tm_gmtoff - that value may be used.
     */

    time_t curTime = (time_t) currentTime;
    struct tm *timeDataPtr = TclpLocaltime((TclpTime_t) &curTime);

    timeZone = -(timeDataPtr->tm_gmtoff / 60);
    if (timeDataPtr->tm_isdst) {
	timeZone += 60;
    }
#endif

#if defined(HAVE_TIMEZONE_VAR) && !defined(TCL_GOT_TIMEZONE) && !defined(USE_DELTA_FOR_TZ)
#define TCL_GOT_TIMEZONE
    /*
     * The 'timezone' external var is present and may be used.
     */

    SetTZIfNecessary();

    /*
     * Note: this is not a typo in "timezone" below! See tzset documentation
     * for details.
     */

    timeZone = timezone / 60;
#endif

#if !defined(TCL_GOT_TIMEZONE)
#define TCL_GOT_TIMEZONE
    /*
     * Fallback - determine time zone with a known reference time.
     */

    time_t tt;
    struct tm *stm;

    tt = 849268800L;		/* 1996-11-29 12:00:00  GMT */
    stm = TclpLocaltime((TclpTime_t) &tt);	/* eg 1996-11-29  6:00:00  CST6CDT */

    /*
     * The calculation below assumes a max of +12 or -12 hours from GMT.
     */

    timeZone = (12 - stm->tm_hour)*60 + (0 - stm->tm_min);
    if (stm->tm_isdst) {
	timeZone += 60;
    }

    /*
     * Now have offset for our known reference time, eg +360 for CST6CDT.
     */
#endif

#ifndef TCL_GOT_TIMEZONE
    /*
     * Cause fatal compile error, we don't know how to get timezone.
     */

#error autoconf did not figure out how to determine the timezone.
#endif

    return timeZone;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetTime --
 *
 *	Gets the current system time in seconds and microseconds since the
 *	beginning of the epoch: 00:00 UCT, January 1, 1970.
 *
 * Results:
 *	Returns the current time in timePtr.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_GetTime(timePtr)
    Tcl_Time *timePtr;		/* Location to store time information. */
{
    struct timeval tv;
    
    (void) gettimeofday(&tv, NULL);
    timePtr->sec = tv.tv_sec;
    timePtr->usec = tv.tv_usec;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpGetDate --
 *
 *	This function converts between seconds and struct tm. If useGMT is
 *	true, then the returned date will be in Greenwich Mean Time (GMT).
 *	Otherwise, it will be in the local time zone.
 *
 * Results:
 *	Returns a static tm structure.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

struct tm *
TclpGetDate(time, useGMT)
    TclpTime_t time;
    int useGMT;
{
    if (useGMT) {
	return TclpGmtime(time);
    } else {
	return TclpLocaltime(time);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclpStrftime --
 *
 *	On Unix, we can safely call the native strftime implementation,
 *	and also ignore the useGMT parameter.
 *
 * Results:
 *	The normal strftime result.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

size_t
TclpStrftime(s, maxsize, format, t, useGMT)
    char *s;
    size_t maxsize;
    CONST char *format;
    CONST struct tm *t;
    int useGMT;
{
    if (format[0] == '%' && format[1] == 'Q') {
	/* Format as a stardate */
	sprintf(s, "Stardate %2d%03d.%01d",
		(((t->tm_year + TM_YEAR_BASE) + 377) - 2323),
		(((t->tm_yday + 1) * 1000) /
			(365 + IsLeapYear((t->tm_year + TM_YEAR_BASE)))),
		(((t->tm_hour * 60) + t->tm_min)/144));
	return(strlen(s));
    }
    setlocale(LC_TIME, "");
    return strftime(s, maxsize, format, t);
}

/*
 *----------------------------------------------------------------------
 *
 * TclpGmtime --
 *
 *	Wrapper around the 'gmtime' library function to make it thread
 *	safe.
 *
 * Results:
 *	Returns a pointer to a 'struct tm' in thread-specific data.
 *
 * Side effects:
 *	Invokes gmtime or gmtime_r as appropriate.
 *
 *----------------------------------------------------------------------
 */

struct tm *
TclpGmtime(tt)
    TclpTime_t_CONST tt;
{
    CONST time_t *timePtr = (CONST time_t *) tt;
				/* Pointer to the number of seconds
				 * since the local system's epoch */

    /*
     * Get a thread-local buffer to hold the returned time.
     */

    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&tmKey);
#ifdef HAVE_GMTIME_R
    gmtime_r(timePtr, &(tsdPtr->gmtime_buf));
#else
    Tcl_MutexLock(&tmMutex);
    memcpy((VOID *) &(tsdPtr->gmtime_buf),
	    (VOID *) gmtime(timePtr),
	    sizeof(struct tm));
    Tcl_MutexUnlock(&tmMutex);
#endif
    return &(tsdPtr->gmtime_buf);
}

/*
 *----------------------------------------------------------------------
 *
 * TclpLocaltime --
 *
 *	Wrapper around the 'localtime' library function to make it thread
 *	safe.
 *
 * Results:
 *	Returns a pointer to a 'struct tm' in thread-specific data.
 *
 * Side effects:
 *	Invokes localtime or localtime_r as appropriate.
 *
 *----------------------------------------------------------------------
 */

struct tm *
TclpLocaltime(tt)
    TclpTime_t_CONST tt;
{
    CONST time_t *timePtr = (CONST time_t *) tt;
				/* Pointer to the number of seconds
				 * since the local system's epoch */
    /*
     * Get a thread-local buffer to hold the returned time.
     */

    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&tmKey);
    SetTZIfNecessary();
#ifdef HAVE_LOCALTIME_R
    localtime_r(timePtr, &(tsdPtr->localtime_buf));
#else
    Tcl_MutexLock(&tmMutex);
    memcpy((VOID *) &(tsdPtr -> localtime_buf),
	    (VOID *) localtime(timePtr),
	    sizeof(struct tm));
    Tcl_MutexUnlock(&tmMutex);
#endif
    return &(tsdPtr->localtime_buf);
}

/*
 *----------------------------------------------------------------------
 *
 * SetTZIfNecessary --
 *
 *	Determines whether a call to 'tzset' is needed prior to the next call
 *	to 'localtime' or examination of the 'timezone' variable.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If 'tzset' has never been called in the current process, or if the
 *	value of the environment variable TZ has changed since the last call
 *	to 'tzset', then 'tzset' is called again.
 *
 *----------------------------------------------------------------------
 */

static void
SetTZIfNecessary()
{
    CONST char *newTZ = getenv("TZ");

    Tcl_MutexLock(&tmMutex);
    if (newTZ == NULL) {
	newTZ = "";
    }
    if (lastTZ == NULL || strcmp(lastTZ, newTZ)) {
	tzset();
	if (lastTZ == NULL) {
	    Tcl_CreateExitHandler(CleanupMemory, (ClientData) NULL);
	} else {
	    Tcl_Free(lastTZ);
	}
	lastTZ = ckalloc(strlen(newTZ) + 1);
	strcpy(lastTZ, newTZ);
    }
    Tcl_MutexUnlock(&tmMutex);
}

/*
 *----------------------------------------------------------------------
 *
 * CleanupMemory --
 *
 *	Releases the private copy of the TZ environment variable upon exit
 *	from Tcl.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Frees allocated memory.
 *
 *----------------------------------------------------------------------
 */

static void
CleanupMemory(ignored)
    ClientData ignored;
{
    ckfree(lastTZ);
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */
