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1 | package Time::Local; |
2 | require 5.000; |
3 | require Exporter; |
4 | use Carp; |
5 | |
6 | @ISA = qw(Exporter); |
7 | @EXPORT = qw(timegm timelocal); |
8 | |
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9 | =head1 NAME |
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10 | |
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11 | Time::Local - efficiently compute time from local and GMT time |
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12 | |
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13 | =head1 SYNOPSIS |
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14 | |
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15 | $time = timelocal($sec,$min,$hours,$mday,$mon,$year); |
16 | $time = timegm($sec,$min,$hours,$mday,$mon,$year); |
17 | |
18 | =head1 DESCRIPTION |
19 | |
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20 | These routines are quite efficient and yet are always guaranteed to |
21 | agree with localtime() and gmtime(), the most notable points being |
22 | that year is year-1900 and month is 0..11. We manage this by caching |
23 | the start times of any months we've seen before. If we know the start |
24 | time of the month, we can always calculate any time within the month. |
25 | The start times themselves are guessed by successive approximation |
26 | starting at the current time, since most dates seen in practice are |
27 | close to the current date. Unlike algorithms that do a binary search |
28 | (calling gmtime once for each bit of the time value, resulting in 32 |
29 | calls), this algorithm calls it at most 6 times, and usually only once |
30 | or twice. If you hit the month cache, of course, it doesn't call it |
31 | at all. |
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32 | |
33 | timelocal is implemented using the same cache. We just assume that we're |
34 | translating a GMT time, and then fudge it when we're done for the timezone |
35 | and daylight savings arguments. The timezone is determined by examining |
36 | the result of localtime(0) when the package is initialized. The daylight |
37 | savings offset is currently assumed to be one hour. |
38 | |
39 | Both routines return -1 if the integer limit is hit. I.e. for dates |
40 | after the 1st of January, 2038 on most machines. |
41 | |
42 | =cut |
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43 | |
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44 | BEGIN { |
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45 | $SEC = 1; |
46 | $MIN = 60 * $SEC; |
47 | $HR = 60 * $MIN; |
48 | $DAY = 24 * $HR; |
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49 | $epoch = (localtime(2*$DAY))[5]; # Allow for bugs near localtime == 0. |
50 | |
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51 | $YearFix = ((gmtime(946684800))[5] == 100) ? 100 : 0; |
52 | |
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53 | } |
54 | |
55 | sub timegm { |
56 | $ym = pack(C2, @_[5,4]); |
57 | $cheat = $cheat{$ym} || &cheat; |
58 | return -1 if $cheat<0 and $^O ne 'VMS'; |
59 | $cheat + $_[0] * $SEC + $_[1] * $MIN + $_[2] * $HR + ($_[3]-1) * $DAY; |
60 | } |
61 | |
62 | sub timelocal { |
63 | my $t = &timegm; |
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64 | my $tt = $t; |
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65 | |
66 | my (@lt) = localtime($t); |
67 | my (@gt) = gmtime($t); |
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68 | if ($t < $DAY and ($lt[5] >= 70 or $gt[5] >= 70 )) { |
69 | # Wrap error, too early a date |
70 | # Try a safer date |
71 | $tt = $DAY; |
72 | @lt = localtime($tt); |
73 | @gt = gmtime($tt); |
74 | } |
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75 | |
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76 | my $tzsec = ($gt[1] - $lt[1]) * $MIN + ($gt[2] - $lt[2]) * $HR; |
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77 | |
78 | my($lday,$gday) = ($lt[7],$gt[7]); |
79 | if($lt[5] > $gt[5]) { |
80 | $tzsec -= $DAY; |
81 | } |
82 | elsif($gt[5] > $lt[5]) { |
83 | $tzsec += $DAY; |
84 | } |
85 | else { |
86 | $tzsec += ($gt[7] - $lt[7]) * $DAY; |
87 | } |
88 | |
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89 | $tzsec += $HR if($lt[8]); |
90 | |
91 | $time = $t + $tzsec; |
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92 | return -1 if $cheat<0 and $^O ne 'VMS'; |
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93 | @test = localtime($time + ($tt - $t)); |
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94 | $time -= $HR if $test[2] != $_[2]; |
95 | $time; |
96 | } |
97 | |
98 | sub cheat { |
99 | $year = $_[5]; |
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100 | $year -= 1900 |
101 | if $year > 1900; |
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102 | $month = $_[4]; |
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103 | croak "Month '$month' out of range 0..11" if $month > 11 || $month < 0; |
104 | croak "Day '$_[3]' out of range 1..31" if $_[3] > 31 || $_[3] < 1; |
105 | croak "Hour '$_[2]' out of range 0..23" if $_[2] > 23 || $_[2] < 0; |
106 | croak "Minute '$_[1]' out of range 0..59" if $_[1] > 59 || $_[1] < 0; |
107 | croak "Second '$_[0]' out of range 0..59" if $_[0] > 59 || $_[0] < 0; |
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108 | $guess = $^T; |
109 | @g = gmtime($guess); |
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110 | $year += $YearFix if $year < $epoch; |
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111 | $lastguess = ""; |
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112 | $counter = 0; |
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113 | while ($diff = $year - $g[5]) { |
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114 | croak "Can't handle date (".join(", ",@_).")" if ++$counter > 255; |
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115 | $guess += $diff * (363 * $DAY); |
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116 | @g = gmtime($guess); |
117 | if (($thisguess = "@g") eq $lastguess){ |
118 | return -1; #date beyond this machine's integer limit |
119 | } |
120 | $lastguess = $thisguess; |
121 | } |
122 | while ($diff = $month - $g[4]) { |
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123 | croak "Can't handle date (".join(", ",@_).")" if ++$counter > 255; |
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124 | $guess += $diff * (27 * $DAY); |
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125 | @g = gmtime($guess); |
126 | if (($thisguess = "@g") eq $lastguess){ |
127 | return -1; #date beyond this machine's integer limit |
128 | } |
129 | $lastguess = $thisguess; |
130 | } |
131 | @gfake = gmtime($guess-1); #still being sceptic |
132 | if ("@gfake" eq $lastguess){ |
133 | return -1; #date beyond this machine's integer limit |
134 | } |
135 | $g[3]--; |
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136 | $guess -= $g[0] * $SEC + $g[1] * $MIN + $g[2] * $HR + $g[3] * $DAY; |
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137 | $cheat{$ym} = $guess; |
138 | } |
139 | |
140 | 1; |