;# timelocal.pl ;# ;# Usage: ;# $time = timelocal($sec,$min,$hours,$mday,$mon,$year); ;# $time = timegm($sec,$min,$hours,$mday,$mon,$year); ;# These routines are quite efficient and yet are always guaranteed to agree ;# with localtime() and gmtime(). We manage this by caching the start times ;# of any months we've seen before. If we know the start time of the month, ;# we can always calculate any time within the month. The start times ;# themselves are guessed by successive approximation starting at the ;# current time, since most dates seen in practice are close to the ;# current date. Unlike algorithms that do a binary search (calling gmtime ;# once for each bit of the time value, resulting in 32 calls), this algorithm ;# calls it at most 6 times, and usually only once or twice. If you hit ;# the month cache, of course, it doesn't call it at all. ;# timelocal is implemented using the same cache. We just assume that we're ;# translating a GMT time, and then fudge it when we're done for the timezone ;# and daylight savings arguments. The timezone is determined by examining ;# the result of localtime(0) when the package is initialized. The daylight ;# savings offset is currently assumed to be one hour. ;# Both routines return -1 if the integer limit is hit. I.e. for dates ;# after the 1st of January, 2038 on most machines. CONFIG: { package timelocal; local($[) = 0; @epoch = localtime(0); $tzmin = $epoch[2] * 60 + $epoch[1]; # minutes east of GMT if ($tzmin > 0) { $tzmin = 24 * 60 - $tzmin; # minutes west of GMT $tzmin -= 24 * 60 if $epoch[5] == 70; # account for the date line } $SEC = 1; $MIN = 60 * $SEC; $HR = 60 * $MIN; $DAYS = 24 * $HR; $YearFix = ((gmtime(946684800))[5] == 100) ? 100 : 0; 1; } sub timegm { package timelocal; local($[) = 0; $ym = pack(C2, @_[5,4]); $cheat = $cheat{$ym} || &cheat; return -1 if $cheat<0; $cheat + $_[0] * $SEC + $_[1] * $MIN + $_[2] * $HR + ($_[3]-1) * $DAYS; } sub timelocal { package timelocal; local($[) = 0; $time = &main'timegm + $tzmin*$MIN; return -1 if $cheat<0; @test = localtime($time); $time -= $HR if $test[2] != $_[2]; $time; } package timelocal; sub cheat { $year = $_[5]; $month = $_[4]; die "Month out of range 0..11 in timelocal.pl\n" if $month > 11 || $month < 0; die "Day out of range 1..31 in timelocal.pl\n" if $_[3] > 31 || $_[3] < 1; die "Hour out of range 0..23 in timelocal.pl\n" if $_[2] > 23 || $_[2] < 0; die "Minute out of range 0..59 in timelocal.pl\n" if $_[1] > 59 || $_[1] < 0; die "Second out of range 0..59 in timelocal.pl\n" if $_[0] > 59 || $_[0] < 0; $guess = $^T; @g = gmtime($guess); $year += $YearFix if $year < $epoch[5]; $lastguess = ""; while ($diff = $year - $g[5]) { $guess += $diff * (363 * $DAYS); @g = gmtime($guess); if (($thisguess = "@g") eq $lastguess){ return -1; #date beyond this machine's integer limit } $lastguess = $thisguess; } while ($diff = $month - $g[4]) { $guess += $diff * (27 * $DAYS); @g = gmtime($guess); if (($thisguess = "@g") eq $lastguess){ return -1; #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 } $g[3]--; $guess -= $g[0] * $SEC + $g[1] * $MIN + $g[2] * $HR + $g[3] * $DAYS; $cheat{$ym} = $guess; }