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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,$year); |
6 | |
7 | ;# These routines are quite efficient and yet are always guaranteed to agree |
8 | ;# with localtime() and gmtime(). We manage this by caching the start times |
9 | ;# of any months we've seen before. If we know the start time of the month, |
10 | ;# we can always calculate any time within the month. The start times |
11 | ;# themselves are guessed by successive approximation starting at the |
12 | ;# current time, since most dates seen in practice are close to the |
13 | ;# current date. Unlike algorithms that do a binary search (calling gmtime |
14 | ;# once for each bit of the time value, resulting in 32 calls), this algorithm |
15 | ;# calls it at most 6 times, and usually only once or twice. If you hit |
16 | ;# the month cache, of course, it doesn't call it at all. |
17 | |
18 | ;# timelocal is implemented using the same cache. We just assume that we're |
19 | ;# translating a GMT time, and then fudge it when we're done for the timezone |
20 | ;# and daylight savings arguments. The timezone is determined by examining |
21 | ;# the result of localtime(0) when the package is initialized. The daylight |
22 | ;# savings offset is currently assumed to be one hour. |
23 | |
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24 | ;# Both routines return -1 if the integer limit is hit. I.e. for dates |
25 | ;# after the 1st of January, 2038 on most machines. |
26 | |
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27 | CONFIG: { |
28 | package timelocal; |
29 | |
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30 | local($[) = 0; |
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31 | @epoch = localtime(0); |
32 | $tzmin = $epoch[2] * 60 + $epoch[1]; # minutes east of GMT |
33 | if ($tzmin > 0) { |
34 | $tzmin = 24 * 60 - $tzmin; # minutes west of GMT |
35 | $tzmin -= 24 * 60 if $epoch[5] == 70; # account for the date line |
36 | } |
37 | |
38 | $SEC = 1; |
39 | $MIN = 60 * $SEC; |
40 | $HR = 60 * $MIN; |
41 | $DAYS = 24 * $HR; |
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42 | $YearFix = ((gmtime(946684800))[5] == 100) ? 100 : 0; |
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43 | 1; |
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44 | } |
45 | |
46 | sub timegm { |
47 | package timelocal; |
48 | |
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49 | local($[) = 0; |
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50 | $ym = pack(C2, @_[5,4]); |
51 | $cheat = $cheat{$ym} || &cheat; |
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52 | return -1 if $cheat<0; |
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53 | $cheat + $_[0] * $SEC + $_[1] * $MIN + $_[2] * $HR + ($_[3]-1) * $DAYS; |
54 | } |
55 | |
56 | sub timelocal { |
57 | package timelocal; |
58 | |
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59 | local($[) = 0; |
60 | $time = &main'timegm + $tzmin*$MIN; |
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61 | return -1 if $cheat<0; |
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62 | @test = localtime($time); |
63 | $time -= $HR if $test[2] != $_[2]; |
64 | $time; |
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65 | } |
66 | |
67 | package timelocal; |
68 | |
69 | sub cheat { |
70 | $year = $_[5]; |
71 | $month = $_[4]; |
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72 | die "Month out of range 0..11 in timelocal.pl\n" |
73 | if $month > 11 || $month < 0; |
74 | die "Day out of range 1..31 in timelocal.pl\n" |
75 | if $_[3] > 31 || $_[3] < 1; |
76 | die "Hour out of range 0..23 in timelocal.pl\n" |
77 | if $_[2] > 23 || $_[2] < 0; |
78 | die "Minute out of range 0..59 in timelocal.pl\n" |
79 | if $_[1] > 59 || $_[1] < 0; |
80 | die "Second out of range 0..59 in timelocal.pl\n" |
81 | if $_[0] > 59 || $_[0] < 0; |
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82 | $guess = $^T; |
83 | @g = gmtime($guess); |
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84 | $year += $YearFix if $year < $epoch[5]; |
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85 | $lastguess = ""; |
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86 | while ($diff = $year - $g[5]) { |
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87 | $guess += $diff * (363 * $DAYS); |
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88 | @g = gmtime($guess); |
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89 | if (($thisguess = "@g") eq $lastguess){ |
90 | return -1; #date beyond this machine's integer limit |
91 | } |
92 | $lastguess = $thisguess; |
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93 | } |
94 | while ($diff = $month - $g[4]) { |
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95 | $guess += $diff * (27 * $DAYS); |
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96 | @g = gmtime($guess); |
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97 | if (($thisguess = "@g") eq $lastguess){ |
98 | return -1; #date beyond this machine's integer limit |
99 | } |
100 | $lastguess = $thisguess; |
101 | } |
102 | @gfake = gmtime($guess-1); #still being sceptic |
103 | if ("@gfake" eq $lastguess){ |
104 | return -1; #date beyond this machine's integer limit |
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105 | } |
106 | $g[3]--; |
107 | $guess -= $g[0] * $SEC + $g[1] * $MIN + $g[2] * $HR + $g[3] * $DAYS; |
108 | $cheat{$ym} = $guess; |
109 | } |