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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 strict; |
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6 | use integer; |
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7 | |
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8 | our $VERSION = '1.03'; |
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9 | our @ISA = qw( Exporter ); |
10 | our @EXPORT = qw( timegm timelocal ); |
11 | our @EXPORT_OK = qw( timegm_nocheck timelocal_nocheck ); |
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12 | |
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13 | my @MonthDays = (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31); |
14 | |
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15 | # Determine breakpoint for rolling century |
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16 | my $ThisYear = (localtime())[5]; |
17 | my $Breakpoint = ($ThisYear + 50) % 100; |
18 | my $NextCentury = $ThisYear - $ThisYear % 100; |
19 | $NextCentury += 100 if $Breakpoint < 50; |
20 | my $Century = $NextCentury - 100; |
21 | |
22 | my (%Options, %Cheat); |
23 | |
24 | # Determine the EPOC day for this machine |
25 | my $Epoc = 0; $Epoc = _daygm(gmtime(0)); |
26 | %Cheat=(); # clear the cache as epoc has changed |
27 | |
28 | my $MaxDay = do { |
29 | no integer; |
30 | int((~0>>1-43200)/86400)-1; |
31 | }; |
32 | |
33 | |
34 | sub _daygm { |
35 | $_[3] + ($Cheat{pack("ss",@_[4,5])} ||= do { |
36 | my $month = ($_[4] + 10) % 12; |
37 | my $year = $_[5] + 1900 - $month/10; |
38 | 365*$year + $year/4 - $year/100 + $year/400 + ($month*306 + 5)/10 - $Epoc |
39 | }); |
40 | } |
41 | |
42 | |
43 | sub _timegm { |
44 | $_[0] + 60 * $_[1] + 3600 * $_[2] + 86400 * &_daygm; |
45 | } |
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46 | |
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47 | |
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48 | sub timegm { |
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49 | my ($sec,$min,$hour,$mday,$month,$year) = @_; |
50 | |
51 | if ($year >= 1000) { |
52 | $year -= 1900; |
53 | } |
54 | elsif ($year < 100 and $year >= 0) { |
55 | $year += ($year > $Breakpoint) ? $Century : $NextCentury; |
56 | } |
57 | |
58 | unless ($Options{no_range_check}) { |
59 | if (abs($year) >= 0x7fff) { |
60 | $year += 1900; |
61 | croak "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)"; |
62 | } |
63 | |
64 | croak "Month '$month' out of range 0..11" if $month > 11 or $month < 0; |
65 | |
66 | my $md = $MonthDays[$month]; |
67 | ++$md unless $month != 1 or $year % 4 or !($year % 400); |
68 | |
69 | croak "Day '$mday' out of range 1..$md" if $mday > $md or $mday < 1; |
70 | croak "Hour '$hour' out of range 0..23" if $hour > 23 or $hour < 0; |
71 | croak "Minute '$min' out of range 0..59" if $min > 59 or $min < 0; |
72 | croak "Second '$sec' out of range 0..59" if $sec > 59 or $sec < 0; |
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73 | } |
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74 | |
75 | my $days = _daygm(undef, undef, undef, $mday, $month, $year); |
76 | |
77 | unless ($Options{no_range_check} or abs($days) < $MaxDay) { |
78 | $year += 1900; |
79 | croak "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)"; |
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80 | } |
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81 | |
82 | $sec + 60*$min + 3600*$hour + 86400*$days; |
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83 | } |
84 | |
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85 | |
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86 | sub timegm_nocheck { |
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87 | local $Options{no_range_check} = 1; |
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88 | &timegm; |
89 | } |
90 | |
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91 | |
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92 | sub timelocal { |
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93 | my $ref_t = &timegm; |
94 | my $loc_t = _timegm(localtime($ref_t)); |
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95 | |
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96 | # Is there a timezone offset from GMT or are we done |
97 | my $zone_off = $ref_t - $loc_t |
98 | or return $loc_t; |
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99 | |
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100 | # Adjust for timezone |
101 | $loc_t = $ref_t + $zone_off; |
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102 | |
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103 | # Are we close to a DST change or are we done |
104 | my $dst_off = $ref_t - _timegm(localtime($loc_t)) |
105 | or return $loc_t; |
106 | |
107 | # Adjust for DST change |
108 | $loc_t + $dst_off; |
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109 | } |
110 | |
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111 | |
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112 | sub timelocal_nocheck { |
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113 | local $Options{no_range_check} = 1; |
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114 | &timelocal; |
115 | } |
116 | |
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117 | 1; |
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118 | |
119 | __END__ |
120 | |
121 | =head1 NAME |
122 | |
123 | Time::Local - efficiently compute time from local and GMT time |
124 | |
125 | =head1 SYNOPSIS |
126 | |
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127 | $time = timelocal($sec,$min,$hour,$mday,$mon,$year); |
128 | $time = timegm($sec,$min,$hour,$mday,$mon,$year); |
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129 | |
130 | =head1 DESCRIPTION |
131 | |
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132 | These routines are the inverse of built-in perl functions localtime() |
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133 | and gmtime(). They accept a date as a six-element array, and return |
134 | the corresponding time(2) value in seconds since the Epoch (Midnight, |
135 | January 1, 1970). This value can be positive or negative. |
136 | |
137 | It is worth drawing particular attention to the expected ranges for |
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138 | the values provided. The value for the day of the month is the actual day |
139 | (ie 1..31), while the month is the number of months since January (0..11). |
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140 | This is consistent with the values returned from localtime() and gmtime(). |
141 | |
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142 | The timelocal() and timegm() functions perform range checking on the |
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143 | input $sec, $min, $hour, $mday, and $mon values by default. If you'd |
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144 | rather they didn't, you can explicitly import the timelocal_nocheck() |
145 | and timegm_nocheck() functions. |
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146 | |
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147 | use Time::Local 'timelocal_nocheck'; |
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148 | |
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149 | { |
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150 | # The 365th day of 1999 |
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151 | print scalar localtime timelocal_nocheck 0,0,0,365,0,99; |
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152 | |
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153 | # The twenty thousandth day since 1970 |
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154 | print scalar localtime timelocal_nocheck 0,0,0,20000,0,70; |
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155 | |
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156 | # And even the 10,000,000th second since 1999! |
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157 | print scalar localtime timelocal_nocheck 10000000,0,0,1,0,99; |
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158 | } |
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159 | |
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160 | Your mileage may vary when trying these with minutes and hours, |
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161 | and it doesn't work at all for months. |
162 | |
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163 | Strictly speaking, the year should also be specified in a form consistent |
164 | with localtime(), i.e. the offset from 1900. |
165 | In order to make the interpretation of the year easier for humans, |
166 | however, who are more accustomed to seeing years as two-digit or four-digit |
167 | values, the following conventions are followed: |
168 | |
169 | =over 4 |
170 | |
171 | =item * |
172 | |
173 | Years greater than 999 are interpreted as being the actual year, |
174 | rather than the offset from 1900. Thus, 1963 would indicate the year |
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175 | Martin Luther King won the Nobel prize, not the year 2863. |
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176 | |
177 | =item * |
178 | |
179 | Years in the range 100..999 are interpreted as offset from 1900, |
180 | so that 112 indicates 2012. This rule also applies to years less than zero |
181 | (but see note below regarding date range). |
182 | |
183 | =item * |
184 | |
185 | Years in the range 0..99 are interpreted as shorthand for years in the |
186 | rolling "current century," defined as 50 years on either side of the current |
187 | year. Thus, today, in 1999, 0 would refer to 2000, and 45 to 2045, |
188 | but 55 would refer to 1955. Twenty years from now, 55 would instead refer |
189 | to 2055. This is messy, but matches the way people currently think about |
190 | two digit dates. Whenever possible, use an absolute four digit year instead. |
191 | |
192 | =back |
193 | |
194 | The scheme above allows interpretation of a wide range of dates, particularly |
195 | if 4-digit years are used. |
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196 | |
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197 | Please note, however, that the range of dates that can be actually be handled |
198 | depends on the size of an integer (time_t) on a given platform. |
199 | Currently, this is 32 bits for most systems, yielding an approximate range |
200 | from Dec 1901 to Jan 2038. |
201 | |
202 | Both timelocal() and timegm() croak if given dates outside the supported |
203 | range. |
204 | |
205 | =head1 IMPLEMENTATION |
206 | |
207 | These routines are quite efficient and yet are always guaranteed to agree |
208 | with localtime() and gmtime(). We manage this by caching the start times |
209 | of any months we've seen before. If we know the start time of the month, |
210 | we can always calculate any time within the month. The start times |
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211 | are calculated using a mathematical formula. Unlike other algorithms |
212 | that do multiple calls to gmtime(). |
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213 | |
214 | timelocal() is implemented using the same cache. We just assume that we're |
215 | translating a GMT time, and then fudge it when we're done for the timezone |
216 | and daylight savings arguments. Note that the timezone is evaluated for |
217 | each date because countries occasionally change their official timezones. |
218 | Assuming that localtime() corrects for these changes, this routine will |
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219 | also be correct. |
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220 | |
221 | =head1 BUGS |
222 | |
223 | The whole scheme for interpreting two-digit years can be considered a bug. |
224 | |
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225 | The proclivity to croak() is probably a bug. |
226 | |
227 | =cut |
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228 | |