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1 | package Time::Local; |
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2 | use 5.006; |
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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 | our $VERSION = '1.04'; |
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10 | our @ISA = qw( Exporter ); |
11 | our @EXPORT = qw( timegm timelocal ); |
12 | our @EXPORT_OK = qw( timegm_nocheck timelocal_nocheck ); |
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13 | |
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14 | my @MonthDays = (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31); |
15 | |
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16 | # Determine breakpoint for rolling century |
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17 | my $ThisYear = (localtime())[5]; |
18 | my $Breakpoint = ($ThisYear + 50) % 100; |
19 | my $NextCentury = $ThisYear - $ThisYear % 100; |
20 | $NextCentury += 100 if $Breakpoint < 50; |
21 | my $Century = $NextCentury - 100; |
22 | |
23 | my (%Options, %Cheat); |
24 | |
25 | # Determine the EPOC day for this machine |
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26 | my $Epoc = 0; |
27 | if ($^O eq 'vos') { |
28 | # work around posix-977 -- VOS doesn't handle dates in |
29 | # the range 1970-1980. |
30 | $Epoc = _daygm((0, 0, 0, 1, 0, 70, 4, 0)); |
31 | } else { |
32 | $Epoc = _daygm(gmtime(0)); |
33 | } |
34 | |
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35 | %Cheat=(); # clear the cache as epoc has changed |
36 | |
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37 | my $MaxInt = ((1<<(8 * $Config{intsize} - 2))-1)*2 + 1; |
38 | my $MaxDay = int(($MaxInt-43200)/86400)-1; |
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39 | |
40 | |
41 | sub _daygm { |
42 | $_[3] + ($Cheat{pack("ss",@_[4,5])} ||= do { |
43 | my $month = ($_[4] + 10) % 12; |
44 | my $year = $_[5] + 1900 - $month/10; |
45 | 365*$year + $year/4 - $year/100 + $year/400 + ($month*306 + 5)/10 - $Epoc |
46 | }); |
47 | } |
48 | |
49 | |
50 | sub _timegm { |
51 | $_[0] + 60 * $_[1] + 3600 * $_[2] + 86400 * &_daygm; |
52 | } |
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53 | |
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54 | |
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55 | sub timegm { |
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56 | my ($sec,$min,$hour,$mday,$month,$year) = @_; |
57 | |
58 | if ($year >= 1000) { |
59 | $year -= 1900; |
60 | } |
61 | elsif ($year < 100 and $year >= 0) { |
62 | $year += ($year > $Breakpoint) ? $Century : $NextCentury; |
63 | } |
64 | |
65 | unless ($Options{no_range_check}) { |
66 | if (abs($year) >= 0x7fff) { |
67 | $year += 1900; |
68 | croak "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)"; |
69 | } |
70 | |
71 | croak "Month '$month' out of range 0..11" if $month > 11 or $month < 0; |
72 | |
73 | my $md = $MonthDays[$month]; |
74 | ++$md unless $month != 1 or $year % 4 or !($year % 400); |
75 | |
76 | croak "Day '$mday' out of range 1..$md" if $mday > $md or $mday < 1; |
77 | croak "Hour '$hour' out of range 0..23" if $hour > 23 or $hour < 0; |
78 | croak "Minute '$min' out of range 0..59" if $min > 59 or $min < 0; |
79 | croak "Second '$sec' out of range 0..59" if $sec > 59 or $sec < 0; |
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80 | } |
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81 | |
82 | my $days = _daygm(undef, undef, undef, $mday, $month, $year); |
83 | |
84 | unless ($Options{no_range_check} or abs($days) < $MaxDay) { |
85 | $year += 1900; |
86 | croak "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)"; |
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87 | } |
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88 | |
89 | $sec + 60*$min + 3600*$hour + 86400*$days; |
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90 | } |
91 | |
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92 | |
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93 | sub timegm_nocheck { |
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94 | local $Options{no_range_check} = 1; |
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95 | &timegm; |
96 | } |
97 | |
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98 | |
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99 | sub timelocal { |
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100 | my $ref_t = &timegm; |
101 | my $loc_t = _timegm(localtime($ref_t)); |
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102 | |
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103 | # Is there a timezone offset from GMT or are we done |
104 | my $zone_off = $ref_t - $loc_t |
105 | or return $loc_t; |
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106 | |
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107 | # Adjust for timezone |
108 | $loc_t = $ref_t + $zone_off; |
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109 | |
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110 | # Are we close to a DST change or are we done |
111 | my $dst_off = $ref_t - _timegm(localtime($loc_t)) |
112 | or return $loc_t; |
113 | |
114 | # Adjust for DST change |
115 | $loc_t + $dst_off; |
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116 | } |
117 | |
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118 | |
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119 | sub timelocal_nocheck { |
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120 | local $Options{no_range_check} = 1; |
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121 | &timelocal; |
122 | } |
123 | |
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124 | 1; |
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125 | |
126 | __END__ |
127 | |
128 | =head1 NAME |
129 | |
130 | Time::Local - efficiently compute time from local and GMT time |
131 | |
132 | =head1 SYNOPSIS |
133 | |
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134 | $time = timelocal($sec,$min,$hour,$mday,$mon,$year); |
135 | $time = timegm($sec,$min,$hour,$mday,$mon,$year); |
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136 | |
137 | =head1 DESCRIPTION |
138 | |
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139 | These routines are the inverse of built-in perl functions localtime() |
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140 | and gmtime(). They accept a date as a six-element array, and return |
141 | the corresponding time(2) value in seconds since the Epoch (Midnight, |
142 | January 1, 1970). This value can be positive or negative. |
143 | |
144 | It is worth drawing particular attention to the expected ranges for |
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145 | the values provided. The value for the day of the month is the actual day |
146 | (ie 1..31), while the month is the number of months since January (0..11). |
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147 | This is consistent with the values returned from localtime() and gmtime(). |
148 | |
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149 | The timelocal() and timegm() functions perform range checking on the |
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150 | input $sec, $min, $hour, $mday, and $mon values by default. If you'd |
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151 | rather they didn't, you can explicitly import the timelocal_nocheck() |
152 | and timegm_nocheck() functions. |
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153 | |
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154 | use Time::Local 'timelocal_nocheck'; |
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155 | |
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156 | { |
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157 | # The 365th day of 1999 |
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158 | print scalar localtime timelocal_nocheck 0,0,0,365,0,99; |
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159 | |
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160 | # The twenty thousandth day since 1970 |
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161 | print scalar localtime timelocal_nocheck 0,0,0,20000,0,70; |
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162 | |
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163 | # And even the 10,000,000th second since 1999! |
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164 | print scalar localtime timelocal_nocheck 10000000,0,0,1,0,99; |
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165 | } |
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166 | |
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167 | Your mileage may vary when trying these with minutes and hours, |
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168 | and it doesn't work at all for months. |
169 | |
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170 | Strictly speaking, the year should also be specified in a form consistent |
171 | with localtime(), i.e. the offset from 1900. |
172 | In order to make the interpretation of the year easier for humans, |
173 | however, who are more accustomed to seeing years as two-digit or four-digit |
174 | values, the following conventions are followed: |
175 | |
176 | =over 4 |
177 | |
178 | =item * |
179 | |
180 | Years greater than 999 are interpreted as being the actual year, |
181 | rather than the offset from 1900. Thus, 1963 would indicate the year |
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182 | Martin Luther King won the Nobel prize, not the year 2863. |
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183 | |
184 | =item * |
185 | |
186 | Years in the range 100..999 are interpreted as offset from 1900, |
187 | so that 112 indicates 2012. This rule also applies to years less than zero |
188 | (but see note below regarding date range). |
189 | |
190 | =item * |
191 | |
192 | Years in the range 0..99 are interpreted as shorthand for years in the |
193 | rolling "current century," defined as 50 years on either side of the current |
194 | year. Thus, today, in 1999, 0 would refer to 2000, and 45 to 2045, |
195 | but 55 would refer to 1955. Twenty years from now, 55 would instead refer |
196 | to 2055. This is messy, but matches the way people currently think about |
197 | two digit dates. Whenever possible, use an absolute four digit year instead. |
198 | |
199 | =back |
200 | |
201 | The scheme above allows interpretation of a wide range of dates, particularly |
202 | if 4-digit years are used. |
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203 | |
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204 | Please note, however, that the range of dates that can be actually be handled |
205 | depends on the size of an integer (time_t) on a given platform. |
206 | Currently, this is 32 bits for most systems, yielding an approximate range |
207 | from Dec 1901 to Jan 2038. |
208 | |
209 | Both timelocal() and timegm() croak if given dates outside the supported |
210 | range. |
211 | |
212 | =head1 IMPLEMENTATION |
213 | |
214 | These routines are quite efficient and yet are always guaranteed to agree |
215 | with localtime() and gmtime(). We manage this by caching the start times |
216 | of any months we've seen before. If we know the start time of the month, |
217 | we can always calculate any time within the month. The start times |
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218 | are calculated using a mathematical formula. Unlike other algorithms |
219 | that do multiple calls to gmtime(). |
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220 | |
221 | timelocal() is implemented using the same cache. We just assume that we're |
222 | translating a GMT time, and then fudge it when we're done for the timezone |
223 | and daylight savings arguments. Note that the timezone is evaluated for |
224 | each date because countries occasionally change their official timezones. |
225 | Assuming that localtime() corrects for these changes, this routine will |
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226 | also be correct. |
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227 | |
228 | =head1 BUGS |
229 | |
230 | The whole scheme for interpreting two-digit years can be considered a bug. |
231 | |
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232 | The proclivity to croak() is probably a bug. |
233 | |
234 | =cut |
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235 | |