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1 | package Time::Local; |
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2 | |
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3 | require Exporter; |
4 | use Carp; |
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5 | use Config; |
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6 | use strict; |
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7 | use integer; |
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8 | |
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9 | use vars qw( $VERSION @ISA @EXPORT @EXPORT_OK ); |
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10 | $VERSION = '1.07'; |
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11 | @ISA = qw( Exporter ); |
12 | @EXPORT = qw( timegm timelocal ); |
13 | @EXPORT_OK = qw( timegm_nocheck timelocal_nocheck ); |
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14 | |
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15 | my @MonthDays = (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31); |
16 | |
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17 | # Determine breakpoint for rolling century |
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18 | my $ThisYear = (localtime())[5]; |
19 | my $Breakpoint = ($ThisYear + 50) % 100; |
20 | my $NextCentury = $ThisYear - $ThisYear % 100; |
21 | $NextCentury += 100 if $Breakpoint < 50; |
22 | my $Century = $NextCentury - 100; |
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23 | my $SecOff = 0; |
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24 | |
25 | my (%Options, %Cheat); |
26 | |
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27 | my $MaxInt = ((1<<(8 * $Config{intsize} - 2))-1)*2 + 1; |
28 | my $MaxDay = int(($MaxInt-43200)/86400)-1; |
29 | |
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30 | # Determine the EPOC day for this machine |
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31 | my $Epoc = 0; |
32 | if ($^O eq 'vos') { |
33 | # work around posix-977 -- VOS doesn't handle dates in |
34 | # the range 1970-1980. |
35 | $Epoc = _daygm((0, 0, 0, 1, 0, 70, 4, 0)); |
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36 | } |
37 | elsif ($^O eq 'MacOS') { |
38 | no integer; |
39 | |
40 | $MaxDay *=2 if $^O eq 'MacOS'; # time_t unsigned ... quick hack? |
41 | # MacOS time() is seconds since 1 Jan 1904, localtime |
42 | # so we need to calculate an offset to apply later |
43 | $Epoc = 693901; |
44 | $SecOff = timelocal(localtime(0)) - timelocal(gmtime(0)); |
45 | $Epoc += _daygm(gmtime(0)); |
46 | } |
47 | else { |
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48 | $Epoc = _daygm(gmtime(0)); |
49 | } |
50 | |
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51 | %Cheat=(); # clear the cache as epoc has changed |
52 | |
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53 | sub _daygm { |
54 | $_[3] + ($Cheat{pack("ss",@_[4,5])} ||= do { |
55 | my $month = ($_[4] + 10) % 12; |
56 | my $year = $_[5] + 1900 - $month/10; |
57 | 365*$year + $year/4 - $year/100 + $year/400 + ($month*306 + 5)/10 - $Epoc |
58 | }); |
59 | } |
60 | |
61 | |
62 | sub _timegm { |
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63 | my $sec = $SecOff + $_[0] + 60 * $_[1] + 3600 * $_[2]; |
64 | |
65 | no integer; |
66 | |
67 | $sec + 86400 * &_daygm; |
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68 | } |
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69 | |
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70 | |
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71 | sub timegm { |
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72 | my ($sec,$min,$hour,$mday,$month,$year) = @_; |
73 | |
74 | if ($year >= 1000) { |
75 | $year -= 1900; |
76 | } |
77 | elsif ($year < 100 and $year >= 0) { |
78 | $year += ($year > $Breakpoint) ? $Century : $NextCentury; |
79 | } |
80 | |
81 | unless ($Options{no_range_check}) { |
82 | if (abs($year) >= 0x7fff) { |
83 | $year += 1900; |
84 | croak "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)"; |
85 | } |
86 | |
87 | croak "Month '$month' out of range 0..11" if $month > 11 or $month < 0; |
88 | |
89 | my $md = $MonthDays[$month]; |
90 | ++$md unless $month != 1 or $year % 4 or !($year % 400); |
91 | |
92 | croak "Day '$mday' out of range 1..$md" if $mday > $md or $mday < 1; |
93 | croak "Hour '$hour' out of range 0..23" if $hour > 23 or $hour < 0; |
94 | croak "Minute '$min' out of range 0..59" if $min > 59 or $min < 0; |
95 | croak "Second '$sec' out of range 0..59" if $sec > 59 or $sec < 0; |
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96 | } |
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97 | |
98 | my $days = _daygm(undef, undef, undef, $mday, $month, $year); |
99 | |
100 | unless ($Options{no_range_check} or abs($days) < $MaxDay) { |
101 | $year += 1900; |
102 | croak "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)"; |
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103 | } |
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104 | |
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105 | $sec += $SecOff + 60*$min + 3600*$hour; |
106 | |
107 | no integer; |
108 | |
109 | $sec + 86400*$days; |
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110 | } |
111 | |
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112 | |
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113 | sub timegm_nocheck { |
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114 | local $Options{no_range_check} = 1; |
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115 | &timegm; |
116 | } |
117 | |
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118 | |
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119 | sub timelocal { |
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120 | no integer; |
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121 | my $ref_t = &timegm; |
122 | my $loc_t = _timegm(localtime($ref_t)); |
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123 | |
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124 | # Is there a timezone offset from GMT or are we done |
125 | my $zone_off = $ref_t - $loc_t |
126 | or return $loc_t; |
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127 | |
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128 | # Adjust for timezone |
129 | $loc_t = $ref_t + $zone_off; |
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130 | |
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131 | # Are we close to a DST change or are we done |
132 | my $dst_off = $ref_t - _timegm(localtime($loc_t)) |
133 | or return $loc_t; |
134 | |
135 | # Adjust for DST change |
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136 | $loc_t += $dst_off; |
137 | |
138 | # for a negative offset from GMT, and if the original date |
139 | # was a non-extent gap in a forward DST jump, we should |
140 | # now have the wrong answer - undo the DST adjust; |
141 | |
142 | return $loc_t if $zone_off <= 0; |
143 | |
144 | my ($s,$m,$h) = localtime($loc_t); |
145 | $loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2]; |
146 | |
147 | $loc_t; |
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148 | } |
149 | |
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150 | |
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151 | sub timelocal_nocheck { |
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152 | local $Options{no_range_check} = 1; |
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153 | &timelocal; |
154 | } |
155 | |
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156 | 1; |
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157 | |
158 | __END__ |
159 | |
160 | =head1 NAME |
161 | |
162 | Time::Local - efficiently compute time from local and GMT time |
163 | |
164 | =head1 SYNOPSIS |
165 | |
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166 | $time = timelocal($sec,$min,$hour,$mday,$mon,$year); |
167 | $time = timegm($sec,$min,$hour,$mday,$mon,$year); |
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168 | |
169 | =head1 DESCRIPTION |
170 | |
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171 | These routines are the inverse of built-in perl functions localtime() |
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172 | and gmtime(). They accept a date as a six-element array, and return |
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173 | the corresponding time(2) value in seconds since the system epoch |
174 | (Midnight, January 1, 1970 UTC on Unix, for example). This value can |
175 | be positive or negative, though POSIX only requires support for |
176 | positive values, so dates before the system's epoch may not work on |
177 | all operating systems. |
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178 | |
179 | It is worth drawing particular attention to the expected ranges for |
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180 | the values provided. The value for the day of the month is the actual day |
181 | (ie 1..31), while the month is the number of months since January (0..11). |
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182 | This is consistent with the values returned from localtime() and gmtime(). |
183 | |
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184 | The timelocal() and timegm() functions perform range checking on the |
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185 | input $sec, $min, $hour, $mday, and $mon values by default. If you'd |
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186 | rather they didn't, you can explicitly import the timelocal_nocheck() |
187 | and timegm_nocheck() functions. |
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188 | |
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189 | use Time::Local 'timelocal_nocheck'; |
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190 | |
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191 | { |
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192 | # The 365th day of 1999 |
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193 | print scalar localtime timelocal_nocheck 0,0,0,365,0,99; |
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194 | |
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195 | # The twenty thousandth day since 1970 |
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196 | print scalar localtime timelocal_nocheck 0,0,0,20000,0,70; |
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197 | |
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198 | # And even the 10,000,000th second since 1999! |
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199 | print scalar localtime timelocal_nocheck 10000000,0,0,1,0,99; |
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200 | } |
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201 | |
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202 | Your mileage may vary when trying these with minutes and hours, |
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203 | and it doesn't work at all for months. |
204 | |
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205 | Strictly speaking, the year should also be specified in a form consistent |
206 | with localtime(), i.e. the offset from 1900. |
207 | In order to make the interpretation of the year easier for humans, |
208 | however, who are more accustomed to seeing years as two-digit or four-digit |
209 | values, the following conventions are followed: |
210 | |
211 | =over 4 |
212 | |
213 | =item * |
214 | |
215 | Years greater than 999 are interpreted as being the actual year, |
216 | rather than the offset from 1900. Thus, 1963 would indicate the year |
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217 | Martin Luther King won the Nobel prize, not the year 2863. |
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218 | |
219 | =item * |
220 | |
221 | Years in the range 100..999 are interpreted as offset from 1900, |
222 | so that 112 indicates 2012. This rule also applies to years less than zero |
223 | (but see note below regarding date range). |
224 | |
225 | =item * |
226 | |
227 | Years in the range 0..99 are interpreted as shorthand for years in the |
228 | rolling "current century," defined as 50 years on either side of the current |
229 | year. Thus, today, in 1999, 0 would refer to 2000, and 45 to 2045, |
230 | but 55 would refer to 1955. Twenty years from now, 55 would instead refer |
231 | to 2055. This is messy, but matches the way people currently think about |
232 | two digit dates. Whenever possible, use an absolute four digit year instead. |
233 | |
234 | =back |
235 | |
236 | The scheme above allows interpretation of a wide range of dates, particularly |
237 | if 4-digit years are used. |
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238 | |
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239 | Please note, however, that the range of dates that can be actually be handled |
240 | depends on the size of an integer (time_t) on a given platform. |
241 | Currently, this is 32 bits for most systems, yielding an approximate range |
242 | from Dec 1901 to Jan 2038. |
243 | |
244 | Both timelocal() and timegm() croak if given dates outside the supported |
245 | range. |
246 | |
247 | =head1 IMPLEMENTATION |
248 | |
249 | These routines are quite efficient and yet are always guaranteed to agree |
250 | with localtime() and gmtime(). We manage this by caching the start times |
251 | of any months we've seen before. If we know the start time of the month, |
252 | we can always calculate any time within the month. The start times |
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253 | are calculated using a mathematical formula. Unlike other algorithms |
254 | that do multiple calls to gmtime(). |
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255 | |
256 | timelocal() is implemented using the same cache. We just assume that we're |
257 | translating a GMT time, and then fudge it when we're done for the timezone |
258 | and daylight savings arguments. Note that the timezone is evaluated for |
259 | each date because countries occasionally change their official timezones. |
260 | Assuming that localtime() corrects for these changes, this routine will |
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261 | also be correct. |
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262 | |
263 | =head1 BUGS |
264 | |
265 | The whole scheme for interpreting two-digit years can be considered a bug. |
266 | |
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267 | The proclivity to croak() is probably a bug. |
268 | |
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269 | =head1 SUPPORT |
270 | |
271 | Support for this module is provided via the perl5-porters@perl.org |
272 | email list. See http://lists.perl.org/ for more details. |
273 | |
274 | Please submit bugs using the RT system at bugs.perl.org, the perlbug |
275 | script, or as a last resort, to the perl5-porters@perl.org list. |
276 | |
277 | =head1 AUTHOR |
278 | |
279 | This module is based on a Perl 4 library, timelocal.pl, that was |
280 | included with Perl 4.036, and was most likely written by Tom |
281 | Christiansen. |
282 | |
283 | The current version was written by Graham Barr. |
284 | |
285 | It is now being maintained separately from the Perl core by Dave |
286 | Rolsky, <autarch@urth.org>. |
287 | |
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288 | =cut |
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289 | |