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ntp 4.2.6p5

    1: ;# timelocal.pl
    2: ;#
    3: ;# Usage:
    4: ;#	$time = timelocal($sec,$min,$hours,$mday,$mon,$year,$junk,$junk,$isdst);
    5: ;#	$time = timegm($sec,$min,$hours,$mday,$mon,$year);
    6: 
    7: ;# These routines are quite efficient and yet are always guaranteed to agree
    8: ;# with localtime() and gmtime().  We manage this by caching the start times
    9: ;# of any months we've seen before.  If we know the start time of the month,
   10: ;# we can always calculate any time within the month.  The start times
   11: ;# themselves are guessed by successive approximation starting at the
   12: ;# current time, since most dates seen in practice are close to the
   13: ;# current date.  Unlike algorithms that do a binary search (calling gmtime
   14: ;# once for each bit of the time value, resulting in 32 calls), this algorithm
   15: ;# calls it at most 6 times, and usually only once or twice.  If you hit
   16: ;# the month cache, of course, it doesn't call it at all.
   17: 
   18: ;# timelocal is implemented using the same cache.  We just assume that we're
   19: ;# translating a GMT time, and then fudge it when we're done for the timezone
   20: ;# and daylight savings arguments.  The timezone is determined by examining
   21: ;# the result of localtime(0) when the package is initialized.  The daylight
   22: ;# savings offset is currently assumed to be one hour.
   23: 
   24: CONFIG: {
   25:     package timelocal;
   26:     
   27:     @epoch = localtime(0);
   28:     $tzmin = $epoch[2] * 60 + $epoch[1];	# minutes east of GMT
   29:     if ($tzmin > 0) {
   30: 	$tzmin = 24 * 60 - $tzmin;		# minutes west of GMT
   31: 	$tzmin -= 24 * 60 if $epoch[5] == 70;	# account for the date line
   32:     }
   33: 
   34:     $SEC = 1;
   35:     $MIN = 60 * $SEC;
   36:     $HR = 60 * $MIN;
   37:     $DAYS = 24 * $HR;
   38:     $YearFix = ((gmtime(946684800))[5] == 100) ? 100 : 0;
   39: }
   40: 
   41: sub timegm {
   42:     package timelocal;
   43: 
   44:     $ym = pack(C2, @_[5,4]);
   45:     $cheat = $cheat{$ym} || &cheat;
   46:     $cheat + $_[0] * $SEC + $_[1] * $MIN + $_[2] * $HR + ($_[3]-1) * $DAYS;
   47: }
   48: 
   49: sub timelocal {
   50:     package timelocal;
   51: 
   52:     $ym = pack(C2, @_[5,4]);
   53:     $cheat = $cheat{$ym} || &cheat;
   54:     $cheat + $_[0] * $SEC + $_[1] * $MIN + $_[2] * $HR + ($_[3]-1) * $DAYS
   55: 	+ $tzmin * $MIN - 60 * 60 * ($_[8] != 0);
   56: }
   57: 
   58: package timelocal;
   59: 
   60: sub cheat {
   61:     $year = $_[5];
   62:     $month = $_[4];
   63:     $guess = $^T;
   64:     @g = gmtime($guess);
   65:     $year += $YearFix if $year < $epoch[5];
   66:     while ($diff = $year - $g[5]) {
   67: 	$guess += $diff * (364 * $DAYS);
   68: 	@g = gmtime($guess);
   69:     }
   70:     while ($diff = $month - $g[4]) {
   71: 	$guess += $diff * (28 * $DAYS);
   72: 	@g = gmtime($guess);
   73:     }
   74:     $g[3]--;
   75:     $guess -= $g[0] * $SEC + $g[1] * $MIN + $g[2] * $HR + $g[3] * $DAYS;
   76:     $cheat{$ym} = $guess;
   77: }