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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 | # Set up constants |
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10 | $SEC = 1; |
11 | $MIN = 60 * $SEC; |
12 | $HR = 60 * $MIN; |
13 | $DAY = 24 * $HR; |
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14 | # Determine breakpoint for rolling century |
15 | my $thisYear = (localtime())[5]; |
16 | $nextCentury = int($thisYear / 100) * 100; |
17 | $breakpoint = ($thisYear + 50) % 100; |
18 | $nextCentury += 100 if $breakpoint < 50; |
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19 | |
20 | sub timegm { |
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21 | my (@date) = @_; |
22 | if ($date[5] > 999) { |
23 | $date[5] -= 1900; |
24 | } |
25 | elsif ($date[5] >= 0 && $date[5] < 100) { |
26 | $date[5] -= 100 if $date[5] > $breakpoint; |
27 | $date[5] += $nextCentury; |
28 | } |
29 | $ym = pack(C2, @date[5,4]); |
30 | $cheat = $cheat{$ym} || &cheat(@date); |
31 | $cheat |
32 | + $date[0] * $SEC |
33 | + $date[1] * $MIN |
34 | + $date[2] * $HR |
35 | + ($date[3]-1) * $DAY; |
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36 | } |
37 | |
38 | sub timelocal { |
39 | my $t = &timegm; |
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40 | my $tt = $t; |
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41 | |
42 | my (@lt) = localtime($t); |
43 | my (@gt) = gmtime($t); |
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44 | if ($t < $DAY and ($lt[5] >= 70 or $gt[5] >= 70 )) { |
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45 | # Wrap error, too early a date |
46 | # Try a safer date |
47 | $tt = $DAY; |
48 | @lt = localtime($tt); |
49 | @gt = gmtime($tt); |
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50 | } |
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51 | |
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52 | my $tzsec = ($gt[1] - $lt[1]) * $MIN + ($gt[2] - $lt[2]) * $HR; |
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53 | |
54 | my($lday,$gday) = ($lt[7],$gt[7]); |
55 | if($lt[5] > $gt[5]) { |
56 | $tzsec -= $DAY; |
57 | } |
58 | elsif($gt[5] > $lt[5]) { |
59 | $tzsec += $DAY; |
60 | } |
61 | else { |
62 | $tzsec += ($gt[7] - $lt[7]) * $DAY; |
63 | } |
64 | |
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65 | $tzsec += $HR if($lt[8]); |
66 | |
67 | $time = $t + $tzsec; |
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68 | @test = localtime($time + ($tt - $t)); |
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69 | $time -= $HR if $test[2] != $_[2]; |
70 | $time; |
71 | } |
72 | |
73 | sub cheat { |
74 | $year = $_[5]; |
75 | $month = $_[4]; |
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76 | croak "Month '$month' out of range 0..11" if $month > 11 || $month < 0; |
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77 | # Allow "julian" conversions. --jhi 1999-09-09 |
78 | # croak "Day '$_[3]' out of range 1..31" if $_[3] > 31 || $_[3] < 1; |
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79 | croak "Hour '$_[2]' out of range 0..23" if $_[2] > 23 || $_[2] < 0; |
80 | croak "Minute '$_[1]' out of range 0..59" if $_[1] > 59 || $_[1] < 0; |
81 | croak "Second '$_[0]' out of range 0..59" if $_[0] > 59 || $_[0] < 0; |
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82 | $guess = $^T; |
83 | @g = gmtime($guess); |
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84 | $lastguess = ""; |
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85 | $counter = 0; |
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86 | while ($diff = $year - $g[5]) { |
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87 | croak "Can't handle date (".join(", ",@_).")" if ++$counter > 255; |
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88 | $guess += $diff * (363 * $DAY); |
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89 | @g = gmtime($guess); |
90 | if (($thisguess = "@g") eq $lastguess){ |
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91 | croak "Can't handle date (".join(", ",@_).")"; |
92 | #date beyond this machine's integer limit |
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93 | } |
94 | $lastguess = $thisguess; |
95 | } |
96 | while ($diff = $month - $g[4]) { |
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97 | croak "Can't handle date (".join(", ",@_).")" if ++$counter > 255; |
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98 | $guess += $diff * (27 * $DAY); |
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99 | @g = gmtime($guess); |
100 | if (($thisguess = "@g") eq $lastguess){ |
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101 | croak "Can't handle date (".join(", ",@_).")"; |
102 | #date beyond this machine's integer limit |
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103 | } |
104 | $lastguess = $thisguess; |
105 | } |
106 | @gfake = gmtime($guess-1); #still being sceptic |
107 | if ("@gfake" eq $lastguess){ |
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108 | croak "Can't handle date (".join(", ",@_).")"; |
109 | #date beyond this machine's integer limit |
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110 | } |
111 | $g[3]--; |
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112 | $guess -= $g[0] * $SEC + $g[1] * $MIN + $g[2] * $HR + $g[3] * $DAY; |
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113 | $cheat{$ym} = $guess; |
114 | } |
115 | |
116 | 1; |
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117 | |
118 | __END__ |
119 | |
120 | =head1 NAME |
121 | |
122 | Time::Local - efficiently compute time from local and GMT time |
123 | |
124 | =head1 SYNOPSIS |
125 | |
126 | $time = timelocal($sec,$min,$hours,$mday,$mon,$year); |
127 | $time = timegm($sec,$min,$hours,$mday,$mon,$year); |
128 | |
129 | =head1 DESCRIPTION |
130 | |
131 | These routines are the inverse of built-in perl fuctions localtime() |
132 | and gmtime(). They accept a date as a six-element array, and return |
133 | the corresponding time(2) value in seconds since the Epoch (Midnight, |
134 | January 1, 1970). This value can be positive or negative. |
135 | |
136 | It is worth drawing particular attention to the expected ranges for |
137 | the values provided. While the day of the month is expected to be in |
138 | the range 1..31, the month should be in the range 0..11. |
139 | This is consistent with the values returned from localtime() and gmtime(). |
140 | |
141 | Strictly speaking, the year should also be specified in a form consistent |
142 | with localtime(), i.e. the offset from 1900. |
143 | In order to make the interpretation of the year easier for humans, |
144 | however, who are more accustomed to seeing years as two-digit or four-digit |
145 | values, the following conventions are followed: |
146 | |
147 | =over 4 |
148 | |
149 | =item * |
150 | |
151 | Years greater than 999 are interpreted as being the actual year, |
152 | rather than the offset from 1900. Thus, 1963 would indicate the year |
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153 | Martin Luther King won the Nobel prize, not the year 2863. |
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154 | |
155 | =item * |
156 | |
157 | Years in the range 100..999 are interpreted as offset from 1900, |
158 | so that 112 indicates 2012. This rule also applies to years less than zero |
159 | (but see note below regarding date range). |
160 | |
161 | =item * |
162 | |
163 | Years in the range 0..99 are interpreted as shorthand for years in the |
164 | rolling "current century," defined as 50 years on either side of the current |
165 | year. Thus, today, in 1999, 0 would refer to 2000, and 45 to 2045, |
166 | but 55 would refer to 1955. Twenty years from now, 55 would instead refer |
167 | to 2055. This is messy, but matches the way people currently think about |
168 | two digit dates. Whenever possible, use an absolute four digit year instead. |
169 | |
170 | =back |
171 | |
172 | The scheme above allows interpretation of a wide range of dates, particularly |
173 | if 4-digit years are used. |
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174 | |
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175 | Please note, however, that the range of dates that can be actually be handled |
176 | depends on the size of an integer (time_t) on a given platform. |
177 | Currently, this is 32 bits for most systems, yielding an approximate range |
178 | from Dec 1901 to Jan 2038. |
179 | |
180 | Both timelocal() and timegm() croak if given dates outside the supported |
181 | range. |
182 | |
183 | =head1 IMPLEMENTATION |
184 | |
185 | These routines are quite efficient and yet are always guaranteed to agree |
186 | with localtime() and gmtime(). We manage this by caching the start times |
187 | of any months we've seen before. If we know the start time of the month, |
188 | we can always calculate any time within the month. The start times |
189 | themselves are guessed by successive approximation starting at the |
190 | current time, since most dates seen in practice are close to the |
191 | current date. Unlike algorithms that do a binary search (calling gmtime |
192 | once for each bit of the time value, resulting in 32 calls), this algorithm |
193 | calls it at most 6 times, and usually only once or twice. If you hit |
194 | the month cache, of course, it doesn't call it at all. |
195 | |
196 | timelocal() is implemented using the same cache. We just assume that we're |
197 | translating a GMT time, and then fudge it when we're done for the timezone |
198 | and daylight savings arguments. Note that the timezone is evaluated for |
199 | each date because countries occasionally change their official timezones. |
200 | Assuming that localtime() corrects for these changes, this routine will |
201 | also be correct. The daylight savings offset is currently assumed |
202 | to be one hour. |
203 | |
204 | =head1 BUGS |
205 | |
206 | The whole scheme for interpreting two-digit years can be considered a bug. |
207 | |
208 | Note that the cache currently handles only years from 1900 through 2155. |
209 | |
210 | The proclivity to croak() is probably a bug. |
211 | |
212 | =cut |