/* 
   Unix SMB/Netbios implementation.
   Version 1.9.
   time handling functions
   Copyright (C) Andrew Tridgell 1992-1997
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"

/*
  This stuff was largely rewritten by Paul Eggert <eggert@twinsun.com>
  in May 1996 
  */


int serverzone=0;
int extra_time_offset = 0;

extern int DEBUGLEVEL;

#ifndef CHAR_BIT
#define CHAR_BIT 8
#endif

#ifndef TIME_T_MIN
#define TIME_T_MIN ((time_t)0 < (time_t) -1 ? (time_t) 0 \
		    : ~ (time_t) 0 << (sizeof (time_t) * CHAR_BIT - 1))
#endif
#ifndef TIME_T_MAX
#define TIME_T_MAX (~ (time_t) 0 - TIME_T_MIN)
#endif



/*******************************************************************
a gettimeofday wrapper
********************************************************************/
void GetTimeOfDay(struct timeval *tval)
{
#ifdef GETTIMEOFDAY1
  gettimeofday(tval);
#else
  gettimeofday(tval,NULL);
#endif
}

#define TM_YEAR_BASE 1900

/*******************************************************************
yield the difference between *A and *B, in seconds, ignoring leap seconds
********************************************************************/
static int tm_diff(struct tm *a, struct tm *b)
{
  int ay = a->tm_year + (TM_YEAR_BASE - 1);
  int by = b->tm_year + (TM_YEAR_BASE - 1);
  int intervening_leap_days =
    (ay/4 - by/4) - (ay/100 - by/100) + (ay/400 - by/400);
  int years = ay - by;
  int days = 365*years + intervening_leap_days + (a->tm_yday - b->tm_yday);
  int hours = 24*days + (a->tm_hour - b->tm_hour);
  int minutes = 60*hours + (a->tm_min - b->tm_min);
  int seconds = 60*minutes + (a->tm_sec - b->tm_sec);
  return seconds;
}

/*******************************************************************
  return the UTC offset in seconds west of UTC
  ******************************************************************/
static int TimeZone(time_t t)
{
  struct tm tm_utc = *(gmtime(&t));
  return tm_diff(&tm_utc,localtime(&t));
}


/*******************************************************************
init the time differences
********************************************************************/
void TimeInit(void)
{
  serverzone = TimeZone(time(NULL));
  DEBUG(4,("Serverzone is %d\n",serverzone));
}


/*******************************************************************
return the same value as TimeZone, but it should be more efficient.

We keep a table of DST offsets to prevent calling localtime() on each 
call of this function. This saves a LOT of time on many unixes.

Updated by Paul Eggert <eggert@twinsun.com>
********************************************************************/
static int TimeZoneFaster(time_t t)
{
  static struct dst_table {time_t start,end; int zone;} *dst_table = NULL;
  static int table_size = 0;
  int i;
  int zone = 0;

  if (t == 0) t = time(NULL);

  /* Tunis has a 8 day DST region, we need to be careful ... */
#define MAX_DST_WIDTH (365*24*60*60)
#define MAX_DST_SKIP (7*24*60*60)

  for (i=0;i<table_size;i++)
    if (t >= dst_table[i].start && t <= dst_table[i].end) break;

  if (i<table_size) {
    zone = dst_table[i].zone;
  } else {
    time_t low,high;

    zone = TimeZone(t);
    dst_table = (struct dst_table *)Realloc(dst_table,
					      sizeof(dst_table[0])*(i+1));
    if (!dst_table) {
      table_size = 0;
    } else {
      table_size++;

      dst_table[i].zone = zone; 
      dst_table[i].start = dst_table[i].end = t;
    
      /* no entry will cover more than 6 months */
      low = t - MAX_DST_WIDTH/2;
      if (t < low)
	low = TIME_T_MIN;
      
      high = t + MAX_DST_WIDTH/2;
      if (high < t)
	high = TIME_T_MAX;
      
      /* widen the new entry using two bisection searches */
      while (low+60*60 < dst_table[i].start) {
	if (dst_table[i].start - low > MAX_DST_SKIP*2)
	  t = dst_table[i].start - MAX_DST_SKIP;
	else
	  t = low + (dst_table[i].start-low)/2;
	if (TimeZone(t) == zone)
	  dst_table[i].start = t;
	else
	  low = t;
      }

      while (high-60*60 > dst_table[i].end) {
	if (high - dst_table[i].end > MAX_DST_SKIP*2)
	  t = dst_table[i].end + MAX_DST_SKIP;
	else
	  t = high - (high-dst_table[i].end)/2;
	if (TimeZone(t) == zone)
	  dst_table[i].end = t;
	else
	  high = t;
      }
#if 0
      DEBUG(1,("Added DST entry from %s ",
	       asctime(localtime(&dst_table[i].start))));
      DEBUG(1,("to %s (%d)\n",asctime(localtime(&dst_table[i].end)),
	       dst_table[i].zone));
#endif
    }
  }
  return zone;
}

/****************************************************************************
  return the UTC offset in seconds west of UTC, adjusted for extra time offset
  **************************************************************************/
int TimeDiff(time_t t)
{
  return TimeZoneFaster(t) + 60*extra_time_offset;
}


/****************************************************************************
  return the UTC offset in seconds west of UTC, adjusted for extra time
  offset, for a local time value.  If ut = lt + LocTimeDiff(lt), then
  lt = ut - TimeDiff(ut), but the converse does not necessarily hold near
  daylight savings transitions because some local times are ambiguous.
  LocTimeDiff(t) equals TimeDiff(t) except near daylight savings transitions.
  +**************************************************************************/
static int LocTimeDiff(time_t lte)
{
  time_t lt = lte - 60*extra_time_offset;
  int d = TimeZoneFaster(lt);
  time_t t = lt + d;

  /* if overflow occurred, ignore all the adjustments so far */
  if (((lte < lt) ^ (extra_time_offset < 0))  |  ((t < lt) ^ (d < 0)))
    t = lte;

  /* now t should be close enough to the true UTC to yield the right answer */
  return TimeDiff(t);
}


/****************************************************************************
try to optimise the localtime call, it can be quite expenive on some machines
****************************************************************************/
struct tm *LocalTime(time_t *t)
{
  time_t t2 = *t;

  t2 -= TimeDiff(t2);

  return(gmtime(&t2));
}


#define TIME_FIXUP_CONSTANT (369.0*365.25*24*60*60-(3.0*24*60*60+6.0*60*60))

/****************************************************************************
interpret an 8 byte "filetime" structure to a time_t
It's originally in "100ns units since jan 1st 1601"

It appears to be kludge-GMT (at least for file listings). This means
its the GMT you get by taking a localtime and adding the
serverzone. This is NOT the same as GMT in some cases. This routine
converts this to real GMT.
****************************************************************************/
time_t interpret_long_date(char *p)
{
  double d;
  time_t ret;
  uint32 tlow,thigh;
  tlow = IVAL(p,0);
  thigh = IVAL(p,4);

  if (thigh == 0) return(0);

  d = ((double)thigh)*4.0*(double)(1<<30);
  d += (tlow&0xFFF00000);
  d *= 1.0e-7;
 
  /* now adjust by 369 years to make the secs since 1970 */
  d -= TIME_FIXUP_CONSTANT;

  if (!(TIME_T_MIN <= d && d <= TIME_T_MAX))
    return(0);

  ret = (time_t)(d+0.5);

  /* this takes us from kludge-GMT to real GMT */
  ret -= serverzone;
  ret += LocTimeDiff(ret);

  return(ret);
}


/****************************************************************************
put a 8 byte filetime from a time_t
This takes real GMT as input and converts to kludge-GMT
****************************************************************************/
void put_long_date(char *p,time_t t)
{
  uint32 tlow,thigh;
  double d;

  if (t==0) {
    SIVAL(p,0,0); SIVAL(p,4,0);
    return;
  }

  /* this converts GMT to kludge-GMT */
  t -= TimeDiff(t) - serverzone; 

  d = (double) (t);

  d += TIME_FIXUP_CONSTANT;

  d *= 1.0e7;

  thigh = (uint32)(d * (1.0/(4.0*(double)(1<<30))));
  tlow = (uint32)(d - ((double)thigh)*4.0*(double)(1<<30));

  SIVAL(p,0,tlow);
  SIVAL(p,4,thigh);
}


/****************************************************************************
check if it's a null mtime
****************************************************************************/
BOOL null_mtime(time_t mtime)
{
  if (mtime == 0 || mtime == 0xFFFFFFFF || mtime == (time_t)-1)
    return(True);
  return(False);
}

/*******************************************************************
  create a 16 bit dos packed date
********************************************************************/
static uint16 make_dos_date1(time_t unixdate,struct tm *t)
{
  uint16 ret=0;
  ret = (((unsigned)(t->tm_mon+1)) >> 3) | ((t->tm_year-80) << 1);
  ret = ((ret&0xFF)<<8) | (t->tm_mday | (((t->tm_mon+1) & 0x7) << 5));
  return(ret);
}

/*******************************************************************
  create a 16 bit dos packed time
********************************************************************/
static uint16 make_dos_time1(time_t unixdate,struct tm *t)
{
  uint16 ret=0;
  ret = ((((unsigned)t->tm_min >> 3)&0x7) | (((unsigned)t->tm_hour) << 3));
  ret = ((ret&0xFF)<<8) | ((t->tm_sec/2) | ((t->tm_min & 0x7) << 5));
  return(ret);
}

/*******************************************************************
  create a 32 bit dos packed date/time from some parameters
  This takes a GMT time and returns a packed localtime structure
********************************************************************/
static uint32 make_dos_date(time_t unixdate)
{
  struct tm *t;
  uint32 ret=0;

  t = LocalTime(&unixdate);

  ret = make_dos_date1(unixdate,t);
  ret = ((ret&0xFFFF)<<16) | make_dos_time1(unixdate,t);

  return(ret);
}

/*******************************************************************
put a dos date into a buffer (time/date format)
This takes GMT time and puts local time in the buffer
********************************************************************/
void put_dos_date(char *buf,int offset,time_t unixdate)
{
  uint32 x = make_dos_date(unixdate);
  SIVAL(buf,offset,x);
}

/*******************************************************************
put a dos date into a buffer (date/time format)
This takes GMT time and puts local time in the buffer
********************************************************************/
void put_dos_date2(char *buf,int offset,time_t unixdate)
{
  uint32 x = make_dos_date(unixdate);
  x = ((x&0xFFFF)<<16) | ((x&0xFFFF0000)>>16);
  SIVAL(buf,offset,x);
}

/*******************************************************************
put a dos 32 bit "unix like" date into a buffer. This routine takes
GMT and converts it to LOCAL time before putting it (most SMBs assume
localtime for this sort of date)
********************************************************************/
void put_dos_date3(char *buf,int offset,time_t unixdate)
{
  if (!null_mtime(unixdate))
    unixdate -= TimeDiff(unixdate);
  SIVAL(buf,offset,unixdate);
}

/*******************************************************************
  interpret a 32 bit dos packed date/time to some parameters
********************************************************************/
static void interpret_dos_date(uint32 date,int *year,int *month,int *day,int *hour,int *minute,int *second)
{
  uint32 p0,p1,p2,p3;

  p0=date&0xFF; p1=((date&0xFF00)>>8)&0xFF; 
  p2=((date&0xFF0000)>>16)&0xFF; p3=((date&0xFF000000)>>24)&0xFF;

  *second = 2*(p0 & 0x1F);
  *minute = ((p0>>5)&0xFF) + ((p1&0x7)<<3);
  *hour = (p1>>3)&0xFF;
  *day = (p2&0x1F);
  *month = ((p2>>5)&0xFF) + ((p3&0x1)<<3) - 1;
  *year = ((p3>>1)&0xFF) + 80;
}

/*******************************************************************
  create a unix date (int GMT) from a dos date (which is actually in
  localtime)
********************************************************************/
time_t make_unix_date(void *date_ptr)
{
  uint32 dos_date=0;
  struct tm t;
  time_t ret;

  dos_date = IVAL(date_ptr,0);

  if (dos_date == 0) return(0);
  
  interpret_dos_date(dos_date,&t.tm_year,&t.tm_mon,
		     &t.tm_mday,&t.tm_hour,&t.tm_min,&t.tm_sec);
  t.tm_isdst = -1;
  
  /* mktime() also does the local to GMT time conversion for us */
  ret = mktime(&t);

  return(ret);
}

/*******************************************************************
like make_unix_date() but the words are reversed
********************************************************************/
time_t make_unix_date2(void *date_ptr)
{
  uint32 x,x2;

  x = IVAL(date_ptr,0);
  x2 = ((x&0xFFFF)<<16) | ((x&0xFFFF0000)>>16);
  SIVAL(&x,0,x2);

  return(make_unix_date((void *)&x));
}

/*******************************************************************
  create a unix GMT date from a dos date in 32 bit "unix like" format
  these generally arrive as localtimes, with corresponding DST
  ******************************************************************/
time_t make_unix_date3(void *date_ptr)
{
  time_t t = IVAL(date_ptr,0);
  if (!null_mtime(t))
    t += LocTimeDiff(t);
  return(t);
}

/****************************************************************************
  return the date and time as a string
****************************************************************************/
char *timestring(void )
{
  static fstring TimeBuf;
  time_t t = time(NULL);
  struct tm *tm = LocalTime(&t);

#ifdef NO_STRFTIME
  fstrcpy(TimeBuf, asctime(tm));
#elif defined(CLIX) || defined(CONVEX)
  strftime(TimeBuf,100,"%m/%d/%y %I:%M:%S %p",tm);
#elif defined(AMPM)
  strftime(TimeBuf,100,"%D %r",tm);
#elif defined(TZ_TIME)
  {
    int zone = TimeDiff(t);
    int absZoneMinutes = (zone<0 ? -zone : zone) / 60;
    size_t len = strftime(TimeBuf,sizeof(TimeBuf)-6,"%D %T",tm);
    sprintf(TimeBuf+len," %c%02d%02d",
	    zone<0?'+':'-',absZoneMinutes/60,absZoneMinutes%60);
  }
#else
  strftime(TimeBuf,100,"%D %T",tm);
#endif
  return(TimeBuf);
}