Annotation of embedaddon/ntp/scripts/monitoring/timelocal.pl, revision 1.1.1.1
1.1 misho 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: }
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