Commit | Line | Data |
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9f9a456c C |
1 | ;# timelocal.pl |
2 | ;# | |
3 | ;# Usage: | |
4 | ;# $time = timelocal($sec,$min,$hours,$mday,$mon,$year); | |
5 | ;# $time = timegm($sec,$min,$hours,$mday,$mon,$year); | |
6 | ||
7 | ;# These routines are quite efficient and yet are always guaranteed to agree | |
8 | ;# with localtime() and gmtime(). We manage this by caching the start times | |
9 | ;# of any months we've seen before. If we know the start time of the month, | |
10 | ;# we can always calculate any time within the month. The start times | |
11 | ;# themselves are guessed by successive approximation starting at the | |
12 | ;# current time, since most dates seen in practice are close to the | |
13 | ;# current date. Unlike algorithms that do a binary search (calling gmtime | |
14 | ;# once for each bit of the time value, resulting in 32 calls), this algorithm | |
15 | ;# calls it at most 6 times, and usually only once or twice. If you hit | |
16 | ;# the month cache, of course, it doesn't call it at all. | |
17 | ||
18 | ;# timelocal is implemented using the same cache. We just assume that we're | |
19 | ;# translating a GMT time, and then fudge it when we're done for the timezone | |
20 | ;# and daylight savings arguments. The timezone is determined by examining | |
21 | ;# the result of localtime(0) when the package is initialized. The daylight | |
22 | ;# savings offset is currently assumed to be one hour. | |
23 | ||
24 | CONFIG: { | |
25 | package timelocal; | |
26 | ||
27 | local($[) = 0; | |
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 | $YearFix = ((gmtime(946684800))[5] == 100) ? 100 : 0; | |
40 | } | |
41 | ||
42 | sub timegm { | |
43 | package timelocal; | |
44 | ||
45 | local($[) = 0; | |
46 | $ym = pack(C2, @_[5,4]); | |
47 | $cheat = $cheat{$ym} || &cheat; | |
48 | $cheat + $_[0] * $SEC + $_[1] * $MIN + $_[2] * $HR + ($_[3]-1) * $DAYS; | |
49 | } | |
50 | ||
51 | sub timelocal { | |
52 | package timelocal; | |
53 | ||
54 | local($[) = 0; | |
55 | $time = &main'timegm + $tzmin*$MIN; | |
56 | @test = localtime($time); | |
57 | $time -= $HR if $test[2] != $_[2]; | |
58 | $time; | |
59 | } | |
60 | ||
61 | package timelocal; | |
62 | ||
63 | sub cheat { | |
64 | $year = $_[5]; | |
65 | $month = $_[4]; | |
66 | die "Month out of range 0..11 in ctime.pl\n" if $month > 11; | |
67 | $guess = $^T; | |
68 | @g = gmtime($guess); | |
69 | $year += $YearFix if $year < $epoch[5]; | |
70 | while ($diff = $year - $g[5]) { | |
71 | $guess += $diff * (363 * $DAYS); | |
72 | @g = gmtime($guess); | |
73 | } | |
74 | while ($diff = $month - $g[4]) { | |
75 | $guess += $diff * (27 * $DAYS); | |
76 | @g = gmtime($guess); | |
77 | } | |
78 | $g[3]--; | |
79 | $guess -= $g[0] * $SEC + $g[1] * $MIN + $g[2] * $HR + $g[3] * $DAYS; | |
80 | $cheat{$ym} = $guess; | |
81 | } |