summaryrefslogtreecommitdiff
path: root/Master/tlpkg/tlperl/lib/Time/Local.pm
blob: 65d7d5884585823c54c1c697afcf4c8005b3f4d9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
package Time::Local;

use strict;

use Carp ();
use Exporter;

our $VERSION = '1.25';

use parent 'Exporter';

our @EXPORT    = qw( timegm timelocal );
our @EXPORT_OK = qw( timegm_nocheck timelocal_nocheck );

my @MonthDays = ( 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 );

# Determine breakpoint for rolling century
my $ThisYear    = ( localtime() )[5];
my $Breakpoint  = ( $ThisYear + 50 ) % 100;
my $NextCentury = $ThisYear - $ThisYear % 100;
$NextCentury += 100 if $Breakpoint < 50;
my $Century = $NextCentury - 100;
my $SecOff  = 0;

my ( %Options, %Cheat );

use constant SECS_PER_MINUTE => 60;
use constant SECS_PER_HOUR   => 3600;
use constant SECS_PER_DAY    => 86400;

my $MaxDay;
if ( $] < 5.012000 ) {
    require Config;
    ## no critic (Variables::ProhibitPackageVars)

    my $MaxInt;
    if ( $^O eq 'MacOS' ) {

        # time_t is unsigned...
        $MaxInt = ( 1 << ( 8 * $Config::Config{ivsize} ) )
            - 1;    ## no critic qw(ProhibitPackageVars)
    }
    else {
        $MaxInt
            = ( ( 1 << ( 8 * $Config::Config{ivsize} - 2 ) ) - 1 ) * 2
            + 1;    ## no critic qw(ProhibitPackageVars)
    }

    $MaxDay = int( ( $MaxInt - ( SECS_PER_DAY / 2 ) ) / SECS_PER_DAY ) - 1;
}
else {
    # recent localtime()'s limit is the year 2**31
    $MaxDay = 365 * ( 2**31 );
}

# Determine the EPOC day for this machine
my $Epoc = 0;
if ( $^O eq 'vos' ) {

    # work around posix-977 -- VOS doesn't handle dates in the range
    # 1970-1980.
    $Epoc = _daygm( 0, 0, 0, 1, 0, 70, 4, 0 );
}
elsif ( $^O eq 'MacOS' ) {
    $MaxDay *= 2 if $^O eq 'MacOS';    # time_t unsigned ... quick hack?
          # MacOS time() is seconds since 1 Jan 1904, localtime
          # so we need to calculate an offset to apply later
    $Epoc   = 693901;
    $SecOff = timelocal( localtime(0) ) - timelocal( gmtime(0) );
    $Epoc += _daygm( gmtime(0) );
}
else {
    $Epoc = _daygm( gmtime(0) );
}

%Cheat = ();    # clear the cache as epoc has changed

sub _daygm {

    # This is written in such a byzantine way in order to avoid
    # lexical variables and sub calls, for speed
    return $_[3] + (
        $Cheat{ pack( 'ss', @_[ 4, 5 ] ) } ||= do {
            my $month = ( $_[4] + 10 ) % 12;
            my $year  = $_[5] + 1900 - int( $month / 10 );

            ( ( 365 * $year )
                + int( $year / 4 )
                    - int( $year / 100 )
                    + int( $year / 400 )
                    + int( ( ( $month * 306 ) + 5 ) / 10 ) ) - $Epoc;
            }
    );
}

sub _timegm {
    my $sec
        = $SecOff + $_[0]
        + ( SECS_PER_MINUTE * $_[1] )
        + ( SECS_PER_HOUR * $_[2] );

    return $sec + ( SECS_PER_DAY * &_daygm );
}

sub timegm {
    my ( $sec, $min, $hour, $mday, $month, $year ) = @_;

    if ( $year >= 1000 ) {
        $year -= 1900;
    }
    elsif ( $year < 100 and $year >= 0 ) {
        $year += ( $year > $Breakpoint ) ? $Century : $NextCentury;
    }

    unless ( $Options{no_range_check} ) {
        Carp::croak("Month '$month' out of range 0..11")
            if $month > 11
            or $month < 0;

        my $md = $MonthDays[$month];
        ++$md
            if $month == 1 && _is_leap_year( $year + 1900 );

        Carp::croak("Day '$mday' out of range 1..$md")
            if $mday > $md or $mday < 1;
        Carp::croak("Hour '$hour' out of range 0..23")
            if $hour > 23 or $hour < 0;
        Carp::croak("Minute '$min' out of range 0..59")
            if $min > 59 or $min < 0;
        Carp::croak("Second '$sec' out of range 0..59")
            if $sec >= 60 or $sec < 0;
    }

    my $days = _daygm( undef, undef, undef, $mday, $month, $year );

    unless ( $Options{no_range_check} or abs($days) < $MaxDay ) {
        my $msg = q{};
        $msg .= "Day too big - $days > $MaxDay\n" if $days > $MaxDay;

        $year += 1900;
        $msg
            .= "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)";

        Carp::croak($msg);
    }

    return
          $sec + $SecOff
        + ( SECS_PER_MINUTE * $min )
        + ( SECS_PER_HOUR * $hour )
        + ( SECS_PER_DAY * $days );
}

sub _is_leap_year {
    return 0 if $_[0] % 4;
    return 1 if $_[0] % 100;
    return 0 if $_[0] % 400;

    return 1;
}

sub timegm_nocheck {
    local $Options{no_range_check} = 1;
    return &timegm;
}

sub timelocal {
    my $ref_t         = &timegm;
    my $loc_for_ref_t = _timegm( localtime($ref_t) );

    my $zone_off = $loc_for_ref_t - $ref_t
        or return $loc_for_ref_t;

    # Adjust for timezone
    my $loc_t = $ref_t - $zone_off;

    # Are we close to a DST change or are we done
    my $dst_off = $ref_t - _timegm( localtime($loc_t) );

    # If this evaluates to true, it means that the value in $loc_t is
    # the _second_ hour after a DST change where the local time moves
    # backward.
    if (
        !$dst_off
        && ( ( $ref_t - SECS_PER_HOUR )
            - _timegm( localtime( $loc_t - SECS_PER_HOUR ) ) < 0 )
        ) {
        return $loc_t - SECS_PER_HOUR;
    }

    # Adjust for DST change
    $loc_t += $dst_off;

    return $loc_t if $dst_off > 0;

    # If the original date was a non-extent gap in a forward DST jump,
    # we should now have the wrong answer - undo the DST adjustment
    my ( $s, $m, $h ) = localtime($loc_t);
    $loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2];

    return $loc_t;
}

sub timelocal_nocheck {
    local $Options{no_range_check} = 1;
    return &timelocal;
}

1;

# ABSTRACT: Efficiently compute time from local and GMT time

__END__

=pod

=encoding UTF-8

=head1 NAME

Time::Local - Efficiently compute time from local and GMT time

=head1 VERSION

version 1.25

=head1 SYNOPSIS

    use Time::Local;

    my $time = timelocal( $sec, $min, $hour, $mday, $mon, $year );
    my $time = timegm( $sec, $min, $hour, $mday, $mon, $year );

=head1 DESCRIPTION

This module provides functions that are the inverse of built-in perl functions
C<localtime()> and C<gmtime()>. They accept a date as a six-element array, and
return the corresponding C<time(2)> value in seconds since the system epoch
(Midnight, January 1, 1970 GMT on Unix, for example). This value can be
positive or negative, though POSIX only requires support for positive values,
so dates before the system's epoch may not work on all operating systems.

It is worth drawing particular attention to the expected ranges for the values
provided. The value for the day of the month is the actual day (i.e. 1..31),
while the month is the number of months since January (0..11). This is
consistent with the values returned from C<localtime()> and C<gmtime()>.

=head1 FUNCTIONS

=head2 C<timelocal()> and C<timegm()>

This module exports two functions by default, C<timelocal()> and C<timegm()>.

The C<timelocal()> and C<timegm()> functions perform range checking on the
input $sec, $min, $hour, $mday, and $mon values by default.

=head2 C<timelocal_nocheck()> and C<timegm_nocheck()>

If you are working with data you know to be valid, you can speed your code up
by using the "nocheck" variants, C<timelocal_nocheck()> and
C<timegm_nocheck()>. These variants must be explicitly imported.

    use Time::Local 'timelocal_nocheck';

    # The 365th day of 1999
    print scalar localtime timelocal_nocheck( 0, 0, 0, 365, 0, 99 );

If you supply data which is not valid (month 27, second 1,000) the results
will be unpredictable (so don't do that).

=head2 Year Value Interpretation

Strictly speaking, the year should be specified in a form consistent with
C<localtime()>, i.e. the offset from 1900. In order to make the interpretation
of the year easier for humans, however, who are more accustomed to seeing
years as two-digit or four-digit values, the following conventions are
followed:

=over 4

=item *

Years greater than 999 are interpreted as being the actual year, rather than
the offset from 1900. Thus, 1964 would indicate the year Martin Luther King
won the Nobel prize, not the year 3864.

=item *

Years in the range 100..999 are interpreted as offset from 1900, so that 112
indicates 2012. This rule also applies to years less than zero (but see note
below regarding date range).

=item *

Years in the range 0..99 are interpreted as shorthand for years in the rolling
"current century," defined as 50 years on either side of the current
year. Thus, today, in 1999, 0 would refer to 2000, and 45 to 2045, but 55
would refer to 1955. Twenty years from now, 55 would instead refer to
2055. This is messy, but matches the way people currently think about two
digit dates. Whenever possible, use an absolute four digit year instead.

=back

The scheme above allows interpretation of a wide range of dates, particularly
if 4-digit years are used.

=head2 Limits of time_t

On perl versions older than 5.12.0, the range of dates that can be actually be
handled depends on the size of C<time_t> (usually a signed integer) on the
given platform. Currently, this is 32 bits for most systems, yielding an
approximate range from Dec 1901 to Jan 2038.

Both C<timelocal()> and C<timegm()> croak if given dates outside the supported
range.

As of version 5.12.0, perl has stopped using the underlying time library of
the operating system it's running on and has its own implementation of those
routines with a safe range of at least +/ 2**52 (about 142 million years).

=head2 Ambiguous Local Times (DST)

Because of DST changes, there are many time zones where the same local time
occurs for two different GMT times on the same day. For example, in the
"Europe/Paris" time zone, the local time of 2001-10-28 02:30:00 can represent
either 2001-10-28 00:30:00 GMT, B<or> 2001-10-28 01:30:00 GMT.

When given an ambiguous local time, the timelocal() function should always
return the epoch for the I<earlier> of the two possible GMT times.

=head2 Non-Existent Local Times (DST)

When a DST change causes a locale clock to skip one hour forward, there will
be an hour's worth of local times that don't exist. Again, for the
"Europe/Paris" time zone, the local clock jumped from 2001-03-25 01:59:59 to
2001-03-25 03:00:00.

If the C<timelocal()> function is given a non-existent local time, it will
simply return an epoch value for the time one hour later.

=head2 Negative Epoch Values

On perl version 5.12.0 and newer, negative epoch values are fully supported.

On older versions of perl, negative epoch (C<time_t>) values, which are not
officially supported by the POSIX standards, are known not to work on some
systems. These include MacOS (pre-OSX) and Win32.

On systems which do support negative epoch values, this module should be able
to cope with dates before the start of the epoch, down the minimum value of
time_t for the system.

=head1 IMPLEMENTATION

These routines are quite efficient and yet are always guaranteed to agree with
C<localtime()> and C<gmtime()>. We manage this by caching the start times of
any months we've seen before. If we know the start time of the month, we can
always calculate any time within the month.  The start times are calculated
using a mathematical formula. Unlike other algorithms that do multiple calls
to C<gmtime()>.

The C<timelocal()> function is implemented using the same cache. We just
assume that we're translating a GMT time, and then fudge it when we're done
for the timezone and daylight savings arguments. Note that the timezone is
evaluated for each date because countries occasionally change their official
timezones. Assuming that C<localtime()> corrects for these changes, this
routine will also be correct.

=head1 AUTHORS EMERITUS

This module is based on a Perl 4 library, timelocal.pl, that was
included with Perl 4.036, and was most likely written by Tom
Christiansen.

The current version was written by Graham Barr.

=head1 BUGS

The whole scheme for interpreting two-digit years can be considered a bug.

Bugs may be submitted through L<https://github.com/houseabsolute/Time-Local/issues>.

There is a mailing list available for users of this distribution,
L<mailto:datetime@perl.org>.

I am also usually active on IRC as 'autarch' on C<irc://irc.perl.org>.

=head1 AUTHOR

Dave Rolsky <autarch@urth.org>

=head1 CONTRIBUTORS

=for stopwords Florian Ragwitz J. Nick Koston Unknown

=over 4

=item *

Florian Ragwitz <rafl@debian.org>

=item *

J. Nick Koston <nick@cpanel.net>

=item *

Unknown <unknown@example.com>

=back

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 1997 - 2016 by Graham Barr & Dave Rolsky.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut