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package HTTP::Date;

$VERSION = "6.02";

require Exporter;
@ISA = qw(Exporter);
@EXPORT = qw(time2str str2time);
@EXPORT_OK = qw(parse_date time2iso time2isoz);

use strict;
require Time::Local;

use vars qw(@DoW @MoY %MoY);
@DoW = qw(Sun Mon Tue Wed Thu Fri Sat);
@MoY = qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec);
@MoY{@MoY} = (1..12);

my %GMT_ZONE = (GMT => 1, UTC => 1, UT => 1, Z => 1);

sub time2str (;$)
{
    my $time = shift;
    $time = time unless defined $time;
    my ($sec, $min, $hour, $mday, $mon, $year, $wday) = gmtime($time);
    sprintf("%s, %02d %s %04d %02d:%02d:%02d GMT",
	    $DoW[$wday],
	    $mday, $MoY[$mon], $year+1900,
	    $hour, $min, $sec);
}

sub str2time ($;$)
{
    my $str = shift;
    return undef unless defined $str;

# fast exit for strictly conforming string
    if ($str =~ /^[SMTWF][a-z][a-z], (\d\d) ([JFMAJSOND][a-z][a-z]) (\d\d\d\d) (\d\d):(\d\d):(\d\d) GMT$/) {
	return eval {
	    my $t = Time::Local::timegm($6, $5, $4, $1, $MoY{$2}-1, $3);
	    $t < 0 ? undef : $t;
	};
    }

my @d = parse_date($str);
    return undef unless @d;
    $d[1]--;        # month

my $tz = pop(@d);
    unless (defined $tz) {
	unless (defined($tz = shift)) {
	    return eval { my $frac = $d[-1]; $frac -= ($d[-1] = int($frac));
			  my $t = Time::Local::timelocal(reverse @d) + $frac;
			  $t < 0 ? undef : $t;
		        };
	}
    }

my $offset = 0;
    if ($GMT_ZONE{uc $tz}) {
	# offset already zero
    }
    elsif ($tz =~ /^([-+])?(\d\d?):?(\d\d)?$/) {
	$offset = 3600 * $2;
	$offset += 60 * $3 if $3;
	$offset *= -1 if $1 && $1 eq '-';
    }
    else {
	eval { require Time::Zone } || return undef;
	$offset = Time::Zone::tz_offset($tz);
	return undef unless defined $offset;
    }

return eval { my $frac = $d[-1]; $frac -= ($d[-1] = int($frac));
		  my $t = Time::Local::timegm(reverse @d) + $frac;
		  $t < 0 ? undef : $t - $offset;
		};
}

sub parse_date ($)
{
    local($_) = shift;
    return unless defined;

# More lax parsing below
    s/^\s+//;  # kill leading space
    s/^(?:Sun|Mon|Tue|Wed|Thu|Fri|Sat)[a-z]*,?\s*//i; # Useless weekday

my($day, $mon, $yr, $hr, $min, $sec, $tz, $ampm);

# Then we are able to check for most of the formats with this regexp
    (($day,$mon,$yr,$hr,$min,$sec,$tz) =
        /^
	 (\d\d?)               # day
	    (?:\s+|[-\/])
	 (\w+)                 # month
	    (?:\s+|[-\/])
	 (\d+)                 # year
	 (?:
	       (?:\s+|:)       # separator before clock
	    (\d\d?):(\d\d)     # hour:min
	    (?::(\d\d))?       # optional seconds
	 )?                    # optional clock
	    \s*
	 ([-+]?\d{2,4}|(?![APap][Mm]\b)[A-Za-z]+)? # timezone
	    \s*
	 (?:$\w+$|\w{3,})?   # ASCII representation of timezone.
	    \s*$
	/x)

# Try the ctime and asctime format
    (($mon, $day, $hr, $min, $sec, $tz, $yr) =
	/^
	 (\w{1,3})             # month
	    \s+
	 (\d\d?)               # day
	    \s+
	 (\d\d?):(\d\d)        # hour:min
	 (?::(\d\d))?          # optional seconds
	    \s+
	 (?:([A-Za-z]+)\s+)?   # optional timezone
	 (\d+)                 # year
	    \s*$               # allow trailing whitespace
	/x)

# Then the Unix 'ls -l' date format
    (($mon, $day, $yr, $hr, $min, $sec) =
	/^
	 (\w{3})               # month
	    \s+
	 (\d\d?)               # day
	    \s+
	 (?:
	    (\d\d\d\d) |       # year
	    (\d{1,2}):(\d{2})  # hour:min
            (?::(\d\d))?       # optional seconds
	 )
	 \s*$
       /x)

# ISO 8601 format '1996-02-29 12:00:00 -0100' and variants
    (($yr, $mon, $day, $hr, $min, $sec, $tz) =
	/^
	  (\d{4})              # year
	     [-\/]?
	  (\d\d?)              # numerical month
	     [-\/]?
	  (\d\d?)              # day
	 (?:
	       (?:\s+|[-:Tt])  # separator before clock
	    (\d\d?):?(\d\d)    # hour:min
	    (?::?(\d\d(?:\.\d*)?))?  # optional seconds (and fractional)
	 )?                    # optional clock
	    \s*
	 ([-+]?\d\d?:?(:?\d\d)?
	  |Z|z)?               # timezone  (Z is "zero meridian", i.e. GMT)
	    \s*$
	/x)

# Windows 'dir' 11-12-96  03:52PM
    (($mon, $day, $yr, $hr, $min, $ampm) =
        /^
          (\d{2})                # numerical month
             -
          (\d{2})                # day
             -
          (\d{2})                # year
             \s+
          (\d\d?):(\d\d)([APap][Mm])  # hour:min AM or PM
             \s*$
        /x)

||
    return;  # unrecognized format

# Translate month name to number
    $mon = $MoY{$mon} ||
           $MoY{"\u\L$mon"} ||
	   ($mon =~ /^\d\d?$/ && $mon >= 1 && $mon <= 12 && int($mon)) ||
           return;

# If the year is missing, we assume first date before the current,
    # because of the formats we support such dates are mostly present
    # on "ls -l" listings.
    unless (defined $yr) {
	my $cur_mon;
	($cur_mon, $yr) = (localtime)[4, 5];
	$yr += 1900;
	$cur_mon++;
	$yr-- if $mon > $cur_mon;
    }
    elsif (length($yr) < 3) {
	# Find "obvious" year
	my $cur_yr = (localtime)[5] + 1900;
	my $m = $cur_yr % 100;
	my $tmp = $yr;
	$yr += $cur_yr - $m;
	$m -= $tmp;
	$yr += ($m > 0) ? 100 : -100
	    if abs($m) > 50;
    }

# Make sure clock elements are defined
    $hr  = 0 unless defined($hr);
    $min = 0 unless defined($min);
    $sec = 0 unless defined($sec);

# Compensate for AM/PM
    if ($ampm) {
	$ampm = uc $ampm;
	$hr = 0 if $hr == 12 && $ampm eq 'AM';
	$hr += 12 if $ampm eq 'PM' && $hr != 12;
    }

return($yr, $mon, $day, $hr, $min, $sec, $tz)
	if wantarray;

if (defined $tz) {
	$tz = "Z" if $tz =~ /^(GMT|UTC?|[-+]?0+)$/;
    }
    else {
	$tz = "";
    }
    return sprintf("%04d-%02d-%02d %02d:%02d:%02d%s",
		   $yr, $mon, $day, $hr, $min, $sec, $tz);
}

sub time2iso (;$)
{
    my $time = shift;
    $time = time unless defined $time;
    my($sec,$min,$hour,$mday,$mon,$year) = localtime($time);
    sprintf("%04d-%02d-%02d %02d:%02d:%02d",
	    $year+1900, $mon+1, $mday, $hour, $min, $sec);
}

sub time2isoz (;$)
{
    my $time = shift;
    $time = time unless defined $time;
    my($sec,$min,$hour,$mday,$mon,$year) = gmtime($time);
    sprintf("%04d-%02d-%02d %02d:%02d:%02dZ",
            $year+1900, $mon+1, $mday, $hour, $min, $sec);
}

__END__

=head1 NAME

HTTP::Date - date conversion routines

=head1 SYNOPSIS

use HTTP::Date;

$string = time2str($time);    # Format as GMT ASCII time
 $time = str2time($string);    # convert ASCII date to machine time

=head1 DESCRIPTION

This module provides functions that deal the date formats used by the
HTTP protocol (and then some more).  Only the first two functions,
time2str() and str2time(), are exported by default.

=over 4

=item time2str( [$time] )

The time2str() function converts a machine time (seconds since epoch)
to a string.  If the function is called without an argument or with an
undefined argument, it will use the current time.

The string returned is in the format preferred for the HTTP protocol.
This is a fixed length subset of the format defined by RFC 1123,
represented in Universal Time (GMT).  An example of a time stamp
in this format is:

Sun, 06 Nov 1994 08:49:37 GMT

=item str2time( $str [, $zone] )

The str2time() function converts a string to machine time.  It returns
C<undef> if the format of $str is unrecognized, otherwise whatever the
C<Time::Local> functions can make out of the parsed time.  Dates
before the system's epoch may not work on all operating systems.  The
time formats recognized are the same as for parse_date().

The function also takes an optional second argument that specifies the
default time zone to use when converting the date.  This parameter is
ignored if the zone is found in the date string itself.  If this
parameter is missing, and the date string format does not contain any
zone specification, then the local time zone is assumed.

If the zone is not "C<GMT>" or numerical (like "C<-0800>" or
"C<+0100>"), then the C<Time::Zone> module must be installed in order
to get the date recognized.

=item parse_date( $str )

This function will try to parse a date string, and then return it as a
list of numerical values followed by a (possible undefined) time zone
specifier; ($year, $month, $day, $hour, $min, $sec, $tz).  The $year
will be the full 4-digit year, and $month numbers start with 1 (for January).

In scalar context the numbers are interpolated in a string of the
"YYYY-MM-DD hh:mm:ss TZ"-format and returned.

If the date is unrecognized, then the empty list is returned (C<undef> in
scalar context).

The function is able to parse the following formats:

"Wed, 09 Feb 1994 22:23:32 GMT"       -- HTTP format
 "Thu Feb  3 17:03:55 GMT 1994"        -- ctime(3) format
 "Thu Feb  3 00:00:00 1994",           -- ANSI C asctime() format
 "Tuesday, 08-Feb-94 14:15:29 GMT"     -- old rfc850 HTTP format
 "Tuesday, 08-Feb-1994 14:15:29 GMT"   -- broken rfc850 HTTP format

"03/Feb/1994:17:03:55 -0700"   -- common logfile format
 "09 Feb 1994 22:23:32 GMT"     -- HTTP format (no weekday)
 "08-Feb-94 14:15:29 GMT"       -- rfc850 format (no weekday)
 "08-Feb-1994 14:15:29 GMT"     -- broken rfc850 format (no weekday)

"1994-02-03 14:15:29 -0100"    -- ISO 8601 format
 "1994-02-03 14:15:29"          -- zone is optional
 "1994-02-03"                   -- only date
 "1994-02-03T14:15:29"          -- Use T as separator
 "19940203T141529Z"             -- ISO 8601 compact format
 "19940203"                     -- only date

"08-Feb-94"         -- old rfc850 HTTP format    (no weekday, no time)
 "08-Feb-1994"       -- broken rfc850 HTTP format (no weekday, no time)
 "09 Feb 1994"       -- proposed new HTTP format  (no weekday, no time)
 "03/Feb/1994"       -- common logfile format     (no time, no offset)

"Feb  3  1994"      -- Unix 'ls -l' format
 "Feb  3 17:03"      -- Unix 'ls -l' format

"11-15-96  03:52PM" -- Windows 'dir' format

The parser ignores leading and trailing whitespace.  It also allow the
seconds to be missing and the month to be numerical in most formats.

If the year is missing, then we assume that the date is the first
matching date I<before> current month.  If the year is given with only
2 digits, then parse_date() will select the century that makes the
year closest to the current date.

=item time2iso( [$time] )

Same as time2str(), but returns a "YYYY-MM-DD hh:mm:ss"-formatted
string representing time in the local time zone.

=item time2isoz( [$time] )

Same as time2str(), but returns a "YYYY-MM-DD hh:mm:ssZ"-formatted
string representing Universal Time.

=back

=head1 SEE ALSO

L<perlfunc/time>, L<Time::Zone>

=head1 COPYRIGHT

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

=cut

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