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root |
1.1 |
package Time::Local; |
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require Exporter; |
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use Carp; |
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use Config; |
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use strict; |
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use integer; |
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use vars qw( $VERSION @ISA @EXPORT @EXPORT_OK ); |
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$VERSION = '1.11'; |
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$VERSION = eval $VERSION; |
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@ISA = qw( Exporter ); |
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@EXPORT = qw( timegm timelocal ); |
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@EXPORT_OK = qw( timegm_nocheck timelocal_nocheck ); |
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my @MonthDays = (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31); |
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# Determine breakpoint for rolling century |
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my $ThisYear = (localtime())[5]; |
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my $Breakpoint = ($ThisYear + 50) % 100; |
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my $NextCentury = $ThisYear - $ThisYear % 100; |
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$NextCentury += 100 if $Breakpoint < 50; |
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my $Century = $NextCentury - 100; |
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my $SecOff = 0; |
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my (%Options, %Cheat, %Min, %Max); |
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my ($MinInt, $MaxInt); |
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if ($^O eq 'MacOS') { |
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# time_t is unsigned... |
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$MaxInt = (1 << (8 * $Config{intsize})) - 1; |
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$MinInt = 0; |
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} else { |
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$MaxInt = ((1 << (8 * $Config{intsize} - 2))-1)*2 + 1; |
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$MinInt = -$MaxInt - 1; |
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# On Win32 (and others?) time_t appears to be signed, but negative |
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# epochs still don't work. - XXX - this is experimental |
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$MinInt = 0 |
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unless defined ((localtime(-1))[0]); |
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} |
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$Max{Day} = ($MaxInt >> 1) / 43200; |
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$Min{Day} = $MinInt ? -($Max{Day} + 1) : 0; |
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$Max{Sec} = $MaxInt - 86400 * $Max{Day}; |
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$Min{Sec} = $MinInt - 86400 * $Min{Day}; |
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# Determine the EPOC day for this machine |
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my $Epoc = 0; |
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if ($^O eq 'vos') { |
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# work around posix-977 -- VOS doesn't handle dates in |
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# the range 1970-1980. |
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$Epoc = _daygm((0, 0, 0, 1, 0, 70, 4, 0)); |
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} |
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elsif ($^O eq 'MacOS') { |
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no integer; |
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# MacOS time() is seconds since 1 Jan 1904, localtime |
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# so we need to calculate an offset to apply later |
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$Epoc = 693901; |
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$SecOff = timelocal(localtime(0)) - timelocal(gmtime(0)); |
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$Epoc += _daygm(gmtime(0)); |
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} |
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else { |
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$Epoc = _daygm(gmtime(0)); |
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} |
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%Cheat=(); # clear the cache as epoc has changed |
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sub _daygm { |
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$_[3] + ($Cheat{pack("ss",@_[4,5])} ||= do { |
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my $month = ($_[4] + 10) % 12; |
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my $year = $_[5] + 1900 - $month/10; |
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365*$year + $year/4 - $year/100 + $year/400 + ($month*306 + 5)/10 - $Epoc |
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}); |
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} |
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sub _timegm { |
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my $sec = $SecOff + $_[0] + 60 * $_[1] + 3600 * $_[2]; |
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no integer; |
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$sec + 86400 * &_daygm; |
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} |
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sub _zoneadjust { |
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my ($day, $sec, $time) = @_; |
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$sec = $sec + _timegm(localtime($time)) - $time; |
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if ($sec >= 86400) { $day++; $sec -= 86400; } |
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if ($sec < 0) { $day--; $sec += 86400; } |
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($day, $sec); |
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} |
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sub timegm { |
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my ($sec,$min,$hour,$mday,$month,$year) = @_; |
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if ($year >= 1000) { |
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$year -= 1900; |
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} |
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elsif ($year < 100 and $year >= 0) { |
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$year += ($year > $Breakpoint) ? $Century : $NextCentury; |
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} |
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unless ($Options{no_range_check}) { |
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if (abs($year) >= 0x7fff) { |
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$year += 1900; |
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croak "Cannot handle date ($sec, $min, $hour, $mday, $month, *$year*)"; |
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} |
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croak "Month '$month' out of range 0..11" if $month > 11 or $month < 0; |
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my $md = $MonthDays[$month]; |
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# ++$md if $month == 1 and $year % 4 == 0 and |
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# ($year % 100 != 0 or ($year + 1900) % 400 == 0); |
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++$md unless $month != 1 or $year % 4 or !($year % 400); |
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croak "Day '$mday' out of range 1..$md" if $mday > $md or $mday < 1; |
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croak "Hour '$hour' out of range 0..23" if $hour > 23 or $hour < 0; |
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croak "Minute '$min' out of range 0..59" if $min > 59 or $min < 0; |
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croak "Second '$sec' out of range 0..59" if $sec > 59 or $sec < 0; |
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} |
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my $days = _daygm(undef, undef, undef, $mday, $month, $year); |
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my $xsec = $sec + $SecOff + 60*$min + 3600*$hour; |
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unless ($Options{no_range_check} |
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or ($days > $Min{Day} or $days == $Min{Day} and $xsec >= $Min{Sec}) |
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and ($days < $Max{Day} or $days == $Max{Day} and $xsec <= $Max{Sec})) |
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{ |
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warn "Day too small - $days > $Min{Day}\n" if $days < $Min{Day}; |
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warn "Day too big - $days > $Max{Day}\n" if $days > $Max{Day}; |
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warn "Sec too small - $days < $Min{Sec}\n" if $days < $Min{Sec}; |
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warn "Sec too big - $days > $Max{Sec}\n" if $days > $Max{Sec}; |
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$year += 1900; |
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croak "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)"; |
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} |
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no integer; |
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$xsec + 86400 * $days; |
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} |
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sub timegm_nocheck { |
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local $Options{no_range_check} = 1; |
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&timegm; |
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} |
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sub timelocal { |
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# Adjust Max/Min allowed times to fit local time zone and call timegm |
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local ($Max{Day}, $Max{Sec}) = _zoneadjust($Max{Day}, $Max{Sec}, $MaxInt); |
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local ($Min{Day}, $Min{Sec}) = _zoneadjust($Min{Day}, $Min{Sec}, $MinInt); |
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my $ref_t = &timegm; |
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# Calculate first guess with a one-day delta to avoid localtime overflow |
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my $delta = ($_[5] < 100)? 86400 : -86400; |
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my $loc_t = _timegm(localtime( $ref_t + $delta )) - $delta; |
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# Is there a timezone offset from GMT or are we done |
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my $zone_off = $ref_t - $loc_t |
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or return $loc_t; |
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# This hack is needed to always pick the first matching time |
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# during a DST change when time would otherwise be ambiguous |
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$zone_off -= 3600 if ($delta > 0 && $ref_t >= 3600); |
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# Adjust for timezone |
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$loc_t = $ref_t + $zone_off; |
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# Are we close to a DST change or are we done |
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my $dst_off = $ref_t - _timegm(localtime($loc_t)) |
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or return $loc_t; |
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# Adjust for DST change |
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$loc_t += $dst_off; |
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return $loc_t if $dst_off >= 0; |
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# for a negative offset from GMT, and if the original date |
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# was a non-extent gap in a forward DST jump, we should |
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# now have the wrong answer - undo the DST adjust; |
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my ($s,$m,$h) = localtime($loc_t); |
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$loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2]; |
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$loc_t; |
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} |
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sub timelocal_nocheck { |
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local $Options{no_range_check} = 1; |
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&timelocal; |
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} |
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1; |
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__END__ |
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=head1 NAME |
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Time::Local - efficiently compute time from local and GMT time |
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=head1 SYNOPSIS |
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$time = timelocal($sec,$min,$hour,$mday,$mon,$year); |
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$time = timegm($sec,$min,$hour,$mday,$mon,$year); |
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=head1 DESCRIPTION |
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These routines are the inverse of built-in perl functions localtime() |
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and gmtime(). They accept a date as a six-element array, and return |
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the corresponding time(2) value in seconds since the system epoch |
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(Midnight, January 1, 1970 GMT on Unix, for example). This value can |
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be positive or negative, though POSIX only requires support for |
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positive values, so dates before the system's epoch may not work on |
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all operating systems. |
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It is worth drawing particular attention to the expected ranges for |
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the values provided. The value for the day of the month is the actual day |
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(ie 1..31), while the month is the number of months since January (0..11). |
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This is consistent with the values returned from localtime() and gmtime(). |
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The timelocal() and timegm() functions perform range checking on the |
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input $sec, $min, $hour, $mday, and $mon values by default. If you'd |
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rather they didn't, you can explicitly import the timelocal_nocheck() |
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and timegm_nocheck() functions. |
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use Time::Local 'timelocal_nocheck'; |
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{ |
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# The 365th day of 1999 |
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print scalar localtime timelocal_nocheck 0,0,0,365,0,99; |
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# The twenty thousandth day since 1970 |
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print scalar localtime timelocal_nocheck 0,0,0,20000,0,70; |
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# And even the 10,000,000th second since 1999! |
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print scalar localtime timelocal_nocheck 10000000,0,0,1,0,99; |
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} |
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Your mileage may vary when trying these with minutes and hours, |
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and it doesn't work at all for months. |
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Strictly speaking, the year should also be specified in a form consistent |
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with localtime(), i.e. the offset from 1900. |
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In order to make the interpretation of the year easier for humans, |
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however, who are more accustomed to seeing years as two-digit or four-digit |
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values, the following conventions are followed: |
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=over 4 |
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=item * |
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Years greater than 999 are interpreted as being the actual year, |
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rather than the offset from 1900. Thus, 1964 would indicate the year |
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Martin Luther King won the Nobel prize, not the year 3864. |
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=item * |
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Years in the range 100..999 are interpreted as offset from 1900, |
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so that 112 indicates 2012. This rule also applies to years less than zero |
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(but see note below regarding date range). |
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=item * |
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Years in the range 0..99 are interpreted as shorthand for years in the |
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rolling "current century," defined as 50 years on either side of the current |
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year. Thus, today, in 1999, 0 would refer to 2000, and 45 to 2045, |
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but 55 would refer to 1955. Twenty years from now, 55 would instead refer |
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to 2055. This is messy, but matches the way people currently think about |
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two digit dates. Whenever possible, use an absolute four digit year instead. |
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=back |
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The scheme above allows interpretation of a wide range of dates, particularly |
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if 4-digit years are used. |
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Please note, however, that the range of dates that can be actually be handled |
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depends on the size of an integer (time_t) on a given platform. |
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Currently, this is 32 bits for most systems, yielding an approximate range |
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from Dec 1901 to Jan 2038. |
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Both timelocal() and timegm() croak if given dates outside the supported |
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range. |
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=head2 Ambiguous Local Times (DST) |
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Because of DST changes, there are many time zones where the same local |
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time occurs for two different GMT times on the same day. For example, |
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in the "Europe/Paris" time zone, the local time of 2001-10-28 02:30:00 |
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can represent either 2001-10-28 00:30:00 GMT, B<or> 2001-10-28 |
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01:30:00 GMT. |
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When given an ambiguous local time, the timelocal() function should |
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always return the epoch for the I<earlier> of the two possible GMT |
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times. |
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=head2 Non-Existent Local Times (DST) |
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When a DST change causes a locale clock to skip one hour forward, |
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there will be an hour's worth of local times that don't exist. Again, |
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for the "Europe/Paris" time zone, the local clock jumped from |
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2001-03-25 01:59:59 to 2001-03-25 03:00:00. |
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If the timelocal() function is given a non-existent local time, it |
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will simply return an epoch value for the time one hour later. |
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=head2 Negative Epoch Values |
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Negative epoch (time_t) values are not officially supported by the |
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POSIX standards, so this module's tests do not test them. On some |
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systems, they are known not to work. These include MacOS (pre-OSX) |
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and Win32. |
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On systems which do support negative epoch values, this module should |
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be able to cope with dates before the start of the epoch, down the |
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minimum value of time_t for the system. |
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=head1 IMPLEMENTATION |
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These routines are quite efficient and yet are always guaranteed to agree |
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with localtime() and gmtime(). We manage this by caching the start times |
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of any months we've seen before. If we know the start time of the month, |
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we can always calculate any time within the month. The start times |
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are calculated using a mathematical formula. Unlike other algorithms |
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that do multiple calls to gmtime(). |
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timelocal() is implemented using the same cache. We just assume that we're |
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translating a GMT time, and then fudge it when we're done for the timezone |
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and daylight savings arguments. Note that the timezone is evaluated for |
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each date because countries occasionally change their official timezones. |
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Assuming that localtime() corrects for these changes, this routine will |
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also be correct. |
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=head1 BUGS |
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The whole scheme for interpreting two-digit years can be considered a bug. |
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=head1 SUPPORT |
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Support for this module is provided via the datetime@perl.org |
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email list. See http://lists.perl.org/ for more details. |
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Please submit bugs using the RT system at rt.cpan.org, or as a last |
| 352 |
|
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resort, to the datetime@perl.org list. |
| 353 |
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|
| 354 |
|
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=head1 AUTHOR |
| 355 |
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|
| 356 |
|
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This module is based on a Perl 4 library, timelocal.pl, that was |
| 357 |
|
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included with Perl 4.036, and was most likely written by Tom |
| 358 |
|
|
Christiansen. |
| 359 |
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|
| 360 |
|
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The current version was written by Graham Barr. |
| 361 |
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|
| 362 |
|
|
It is now being maintained separately from the Perl core by Dave |
| 363 |
|
|
Rolsky, <autarch@urth.org>. |
| 364 |
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|
| 365 |
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=cut |
| 366 |
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