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package Time::Local;
require 5.000;
require Exporter;
use Carp;
@ISA = qw(Exporter);
@EXPORT = qw(timegm timelocal);
# timelocal.pl
#
# Usage:
# $time = timelocal($sec,$min,$hours,$mday,$mon,$year);
# $time = timegm($sec,$min,$hours,$mday,$mon,$year);
# These routines are quite efficient and yet are always guaranteed to agree
# with localtime() and gmtime(). We manage this by caching the start times
# of any months we've seen before. If we know the start time of the month,
# we can always calculate any time within the month. The start times
# themselves are guessed by successive approximation starting at the
# current time, since most dates seen in practice are close to the
# current date. Unlike algorithms that do a binary search (calling gmtime
# once for each bit of the time value, resulting in 32 calls), this algorithm
# calls it at most 6 times, and usually only once or twice. If you hit
# the month cache, of course, it doesn't call it at all.
# timelocal is implemented using the same cache. We just assume that we're
# translating a GMT time, and then fudge it when we're done for the timezone
# and daylight savings arguments. The timezone is determined by examining
# the result of localtime(0) when the package is initialized. The daylight
# savings offset is currently assumed to be one hour.
# Both routines return -1 if the integer limit is hit. I.e. for dates
# after the 1st of January, 2038 on most machines.
@epoch = localtime(0);
$tzmin = $epoch[2] * 60 + $epoch[1]; # minutes east of GMT
if ($tzmin > 0) {
$tzmin = 24 * 60 - $tzmin; # minutes west of GMT
$tzmin -= 24 * 60 if $epoch[5] == 70; # account for the date line
}
$SEC = 1;
$MIN = 60 * $SEC;
$HR = 60 * $MIN;
$DAYS = 24 * $HR;
$YearFix = ((gmtime(946684800))[5] == 100) ? 100 : 0;
sub timegm {
$ym = pack(C2, @_[5,4]);
$cheat = $cheat{$ym} || &cheat;
return -1 if $cheat<0;
$cheat + $_[0] * $SEC + $_[1] * $MIN + $_[2] * $HR + ($_[3]-1) * $DAYS;
}
sub timelocal {
$time = &timegm + $tzmin*$MIN;
return -1 if $cheat<0;
@test = localtime($time);
$time -= $HR if $test[2] != $_[2];
$time;
}
sub cheat {
$year = $_[5];
$month = $_[4];
croak "Month out of range 0..11 in timelocal.pl"
if $month > 11 || $month < 0;
croak "Day out of range 1..31 in timelocal.pl"
if $_[3] > 31 || $_[3] < 1;
croak "Hour out of range 0..23 in timelocal.pl"
if $_[2] > 23 || $_[2] < 0;
croak "Minute out of range 0..59 in timelocal.pl"
if $_[1] > 59 || $_[1] < 0;
croak "Second out of range 0..59 in timelocal.pl"
if $_[0] > 59 || $_[0] < 0;
$guess = $^T;
@g = gmtime($guess);
$year += $YearFix if $year < $epoch[5];
$lastguess = "";
while ($diff = $year - $g[5]) {
$guess += $diff * (363 * $DAYS);
@g = gmtime($guess);
if (($thisguess = "@g") eq $lastguess){
return -1; #date beyond this machine's integer limit
}
$lastguess = $thisguess;
}
while ($diff = $month - $g[4]) {
$guess += $diff * (27 * $DAYS);
@g = gmtime($guess);
if (($thisguess = "@g") eq $lastguess){
return -1; #date beyond this machine's integer limit
}
$lastguess = $thisguess;
}
@gfake = gmtime($guess-1); #still being sceptic
if ("@gfake" eq $lastguess){
return -1; #date beyond this machine's integer limit
}
$g[3]--;
$guess -= $g[0] * $SEC + $g[1] * $MIN + $g[2] * $HR + $g[3] * $DAYS;
$cheat{$ym} = $guess;
}
1;
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