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1 | ;# timelocal.pl |
2 | ;# |
3 | ;# Usage: |
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4 | ;# $time = timelocal($sec,$min,$hours,$mday,$mon,$year); |
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5 | ;# $time = timegm($sec,$min,$hours,$mday,$mon,$year); |
6 | |
7 | ;# These routines are quite efficient and yet are always guaranteed to agree |
8 | ;# with localtime() and gmtime(). We manage this by caching the start times |
9 | ;# of any months we've seen before. If we know the start time of the month, |
10 | ;# we can always calculate any time within the month. The start times |
11 | ;# themselves are guessed by successive approximation starting at the |
12 | ;# current time, since most dates seen in practice are close to the |
13 | ;# current date. Unlike algorithms that do a binary search (calling gmtime |
14 | ;# once for each bit of the time value, resulting in 32 calls), this algorithm |
15 | ;# calls it at most 6 times, and usually only once or twice. If you hit |
16 | ;# the month cache, of course, it doesn't call it at all. |
17 | |
18 | ;# timelocal is implemented using the same cache. We just assume that we're |
19 | ;# translating a GMT time, and then fudge it when we're done for the timezone |
20 | ;# and daylight savings arguments. The timezone is determined by examining |
21 | ;# the result of localtime(0) when the package is initialized. The daylight |
22 | ;# savings offset is currently assumed to be one hour. |
23 | |
24 | CONFIG: { |
25 | package timelocal; |
26 | |
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27 | local($[) = 0; |
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28 | @epoch = localtime(0); |
29 | $tzmin = $epoch[2] * 60 + $epoch[1]; # minutes east of GMT |
30 | if ($tzmin > 0) { |
31 | $tzmin = 24 * 60 - $tzmin; # minutes west of GMT |
32 | $tzmin -= 24 * 60 if $epoch[5] == 70; # account for the date line |
33 | } |
34 | |
35 | $SEC = 1; |
36 | $MIN = 60 * $SEC; |
37 | $HR = 60 * $MIN; |
38 | $DAYS = 24 * $HR; |
39 | } |
40 | |
41 | sub timegm { |
42 | package timelocal; |
43 | |
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44 | local($[) = 0; |
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45 | $ym = pack(C2, @_[5,4]); |
46 | $cheat = $cheat{$ym} || &cheat; |
47 | $cheat + $_[0] * $SEC + $_[1] * $MIN + $_[2] * $HR + ($_[3]-1) * $DAYS; |
48 | } |
49 | |
50 | sub timelocal { |
51 | package timelocal; |
52 | |
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53 | local($[) = 0; |
54 | $time = &main'timegm + $tzmin*$MIN; |
55 | @test = localtime($time); |
56 | $time -= $HR if $test[2] != $_[2]; |
57 | $time; |
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58 | } |
59 | |
60 | package timelocal; |
61 | |
62 | sub cheat { |
63 | $year = $_[5]; |
64 | $month = $_[4]; |
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65 | die "Month out of range 0..11 in ctime.pl\n" if $month > 11; |
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66 | $guess = $^T; |
67 | @g = gmtime($guess); |
68 | while ($diff = $year - $g[5]) { |
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69 | $guess += $diff * (363 * $DAYS); |
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70 | @g = gmtime($guess); |
71 | } |
72 | while ($diff = $month - $g[4]) { |
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73 | $guess += $diff * (27 * $DAYS); |
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74 | @g = gmtime($guess); |
75 | } |
76 | $g[3]--; |
77 | $guess -= $g[0] * $SEC + $g[1] * $MIN + $g[2] * $HR + $g[3] * $DAYS; |
78 | $cheat{$ym} = $guess; |
79 | } |