@ISA = qw(Exporter);
@EXPORT = qw(timegm timelocal);
-=head1 NAME
-
-Time::Local - efficiently compute time from local and GMT time
-
-=head1 SYNOPSIS
-
- $time = timelocal($sec,$min,$hours,$mday,$mon,$year);
- $time = timegm($sec,$min,$hours,$mday,$mon,$year);
-
-=head1 DESCRIPTION
-
-These routines are quite efficient and yet are always guaranteed to
-agree with localtime() and gmtime(), the most notable points being
-that year is year-1900 and month is 0..11. 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 themselves are guessed by successive approximation
-starting at the current time, since most dates seen in practice are
-close to the current date. Unlike algorithms that do a binary search
-(calling gmtime once for each bit of the time value, resulting in 32
-calls), this algorithm calls it at most 6 times, and usually only once
-or twice. If you hit the month cache, of course, it doesn't call it
-at all.
-
-timelocal 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. The timezone is determined by examining
-the result of localtime(0) when the package is initialized. The daylight
-savings offset is currently assumed to be one hour.
-
-Both routines return -1 if the integer limit is hit. I.e. for dates
-after the 1st of January, 2038 on most machines.
-
-=cut
-
-BEGIN {
+# Set up constants
$SEC = 1;
$MIN = 60 * $SEC;
$HR = 60 * $MIN;
$DAY = 24 * $HR;
- $epoch = (localtime(2*$DAY))[5]; # Allow for bugs near localtime == 0.
-
- $YearFix = ((gmtime(946684800))[5] == 100) ? 100 : 0;
-
-}
+# Determine breakpoint for rolling century
+ my $thisYear = (localtime())[5];
+ $nextCentury = int($thisYear / 100) * 100;
+ $breakpoint = ($thisYear + 50) % 100;
+ $nextCentury += 100 if $breakpoint < 50;
sub timegm {
- $ym = pack(C2, @_[5,4]);
- $cheat = $cheat{$ym} || &cheat;
- return -1 if $cheat<0 and $^O ne 'VMS';
- $cheat + $_[0] * $SEC + $_[1] * $MIN + $_[2] * $HR + ($_[3]-1) * $DAY;
+ my (@date) = @_;
+ if ($date[5] > 999) {
+ $date[5] -= 1900;
+ }
+ elsif ($date[5] >= 0 && $date[5] < 100) {
+ $date[5] -= 100 if $date[5] > $breakpoint;
+ $date[5] += $nextCentury;
+ }
+ $ym = pack(C2, @date[5,4]);
+ $cheat = $cheat{$ym} || &cheat(@date);
+ $cheat
+ + $date[0] * $SEC
+ + $date[1] * $MIN
+ + $date[2] * $HR
+ + ($date[3]-1) * $DAY;
}
sub timelocal {
my (@lt) = localtime($t);
my (@gt) = gmtime($t);
if ($t < $DAY and ($lt[5] >= 70 or $gt[5] >= 70 )) {
- # Wrap error, too early a date
- # Try a safer date
- $tt = $DAY;
- @lt = localtime($tt);
- @gt = gmtime($tt);
+ # Wrap error, too early a date
+ # Try a safer date
+ $tt = $DAY;
+ @lt = localtime($tt);
+ @gt = gmtime($tt);
}
my $tzsec = ($gt[1] - $lt[1]) * $MIN + ($gt[2] - $lt[2]) * $HR;
$tzsec += $HR if($lt[8]);
$time = $t + $tzsec;
- return -1 if $cheat<0 and $^O ne 'VMS';
@test = localtime($time + ($tt - $t));
$time -= $HR if $test[2] != $_[2];
$time;
sub cheat {
$year = $_[5];
- $year -= 1900
- if $year > 1900;
$month = $_[4];
croak "Month '$month' out of range 0..11" if $month > 11 || $month < 0;
croak "Day '$_[3]' out of range 1..31" if $_[3] > 31 || $_[3] < 1;
croak "Second '$_[0]' out of range 0..59" if $_[0] > 59 || $_[0] < 0;
$guess = $^T;
@g = gmtime($guess);
- $year += $YearFix if $year < $epoch;
$lastguess = "";
$counter = 0;
while ($diff = $year - $g[5]) {
$guess += $diff * (363 * $DAY);
@g = gmtime($guess);
if (($thisguess = "@g") eq $lastguess){
- return -1; #date beyond this machine's integer limit
+ croak "Can't handle date (".join(", ",@_).")";
+ #date beyond this machine's integer limit
}
$lastguess = $thisguess;
}
$guess += $diff * (27 * $DAY);
@g = gmtime($guess);
if (($thisguess = "@g") eq $lastguess){
- return -1; #date beyond this machine's integer limit
+ croak "Can't handle date (".join(", ",@_).")";
+ #date beyond this machine's integer limit
}
$lastguess = $thisguess;
}
@gfake = gmtime($guess-1); #still being sceptic
if ("@gfake" eq $lastguess){
- return -1; #date beyond this machine's integer limit
+ croak "Can't handle date (".join(", ",@_).")";
+ #date beyond this machine's integer limit
}
$g[3]--;
$guess -= $g[0] * $SEC + $g[1] * $MIN + $g[2] * $HR + $g[3] * $DAY;
}
1;
+
+__END__
+
+=head1 NAME
+
+Time::Local - efficiently compute time from local and GMT time
+
+=head1 SYNOPSIS
+
+ $time = timelocal($sec,$min,$hours,$mday,$mon,$year);
+ $time = timegm($sec,$min,$hours,$mday,$mon,$year);
+
+=head1 DESCRIPTION
+
+These routines are the inverse of built-in perl fuctions localtime()
+and gmtime(). They accept a date as a six-element array, and return
+the corresponding time(2) value in seconds since the Epoch (Midnight,
+January 1, 1970). This value can be positive or negative.
+
+It is worth drawing particular attention to the expected ranges for
+the values provided. While the day of the month is expected to be in
+the range 1..31, the month should be in the range 0..11.
+This is consistent with the values returned from localtime() and gmtime().
+
+Strictly speaking, the year should also be specified in a form consistent
+with 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, 1963 would indicate the year
+of Martin Luther King's assassination, not the year 2863.
+
+=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.
+Please note, however, that the range of dates that can be actually be handled
+depends on the size of an integer (time_t) on a given platform.
+Currently, this is 32 bits for most systems, yielding an approximate range
+from Dec 1901 to Jan 2038.
+
+Both timelocal() and timegm() croak if given dates outside the supported
+range.
+
+=head1 IMPLEMENTATION
+
+These routines are quite efficient and yet are always guaranteed to agree
+with localtime() and 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
+themselves are guessed by successive approximation starting at the
+current time, since most dates seen in practice are close to the
+current date. Unlike algorithms that do a binary search (calling gmtime
+once for each bit of the time value, resulting in 32 calls), this algorithm
+calls it at most 6 times, and usually only once or twice. If you hit
+the month cache, of course, it doesn't call it at all.
+
+timelocal() 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 localtime() corrects for these changes, this routine will
+also be correct. The daylight savings offset is currently assumed
+to be one hour.
+
+=head1 BUGS
+
+The whole scheme for interpreting two-digit years can be considered a bug.
+
+Note that the cache currently handles only years from 1900 through 2155.
+
+The proclivity to croak() is probably a bug.
+
+=cut
projects / p5sagit/p5-mst-13.2.git / commitdiff