1 files changed, 75 insertions, 0 deletions
diff --git a/lib/timelocal.pl b/lib/timelocal.pl
new file mode 100644
index 0000000000..a228041637
--- /dev/null
+++ b/lib/timelocal.pl
@@ -0,0 +1,75 @@
+;# timelocal.pl
+;#
+;# Usage:
+;#	$time = timelocal($sec,$min,$hours,$mday,$mon,$year,$junk,$junk,$isdst);
+;#	$time = timegm($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.
+
+CONFIG: {
+    package timelocal;
+    
+    @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;
+}
+
+sub timegm {
+    package timelocal;
+
+    $ym = pack(C2, @_[5,4]);
+    $cheat = $cheat{$ym} || &cheat;
+    $cheat + $_[0] * $SEC + $_[1] * $MIN + $_[2] * $HR + ($_[3]-1) * $DAYS;
+}
+
+sub timelocal {
+    package timelocal;
+
+    $ym = pack(C2, @_[5,4]);
+    $cheat = $cheat{$ym} || &cheat;
+    $cheat + $_[0] * $SEC + $_[1] * $MIN + $_[2] * $HR + ($_[3]-1) * $DAYS
+	+ $tzmin * $MIN - 60 * 60 * ($_[8] != 0);
+}
+
+package timelocal;
+
+sub cheat {
+    $year = $_[5];
+    $month = $_[4];
+    $guess = $^T;
+    @g = gmtime($guess);
+    while ($diff = $year - $g[5]) {
+	$guess += $diff * (364 * $DAYS);
+	@g = gmtime($guess);
+    }
+    while ($diff = $month - $g[4]) {
+	$guess += $diff * (28 * $DAYS);
+	@g = gmtime($guess);
+    }
+    $g[3]--;
+    $guess -= $g[0] * $SEC + $g[1] * $MIN + $g[2] * $HR + $g[3] * $DAYS;
+    $cheat{$ym} = $guess;
+}