dist/ntp/scripts/monitoring/timelocal.pl

   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 }