| 1 | #------------------------------------------------------------------------------
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| 2 | # File: Shift.pl
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| 3 | #
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| 4 | # Description: ExifTool time shifting routines
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| 5 | #
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| 6 | # Revisions: 10/28/2005 - P. Harvey Created
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| 7 | #------------------------------------------------------------------------------
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| 8 |
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| 9 | package Image::ExifTool;
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| 10 |
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| 11 | use strict;
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| 12 |
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| 13 | sub ShiftTime($$$;$);
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| 14 |
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| 15 | #------------------------------------------------------------------------------
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| 16 | # apply shift to value in new value hash
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| 17 | # Inputs: 0) shift type, 1) shift string, 2) raw date/time value, 3) new value hash ref
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| 18 | # Returns: error string or undef on success and updates value in new value hash
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| 19 | sub ApplyShift($$$;$)
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| 20 | {
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| 21 | my ($func, $shift, $val, $nvHash) = @_;
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| 22 |
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| 23 | # get shift direction from first character in shift string
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| 24 | $shift =~ s/^(\+|-)// or return 'Bad shift string (no sign)';
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| 25 | my $pre = $1;
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| 26 | my $dir = ($pre eq '+') ? 1 : -1;
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| 27 | my $tagInfo = $$nvHash{TagInfo};
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| 28 | my $tag = $$tagInfo{Name};
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| 29 | my $self = $$nvHash{Self}; # (used in eval)
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| 30 | my $shiftOffset;
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| 31 | if ($$nvHash{ShiftOffset}) {
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| 32 | $shiftOffset = $$nvHash{ShiftOffset};
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| 33 | } else {
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| 34 | $shiftOffset = $$nvHash{ShiftOffset} = { };
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| 35 | }
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| 36 |
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| 37 | # initialize handler for eval warnings
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| 38 | local $SIG{'__WARN__'} = \&SetWarning;
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| 39 | SetWarning(undef);
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| 40 |
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| 41 | # shift is applied to ValueConv value, so we must ValueConv-Shift-ValueConvInv
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| 42 | my ($type, $err);
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| 43 | foreach $type ('ValueConv','Shift','ValueConvInv') {
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| 44 | if ($type eq 'Shift') {
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| 45 | #### eval ShiftXxx function
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| 46 | $err = eval "Shift$func(\$val, \$shift, \$dir, \$shiftOffset)";
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| 47 | } elsif ($$tagInfo{$type}) {
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| 48 | my $conv = $$tagInfo{$type};
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| 49 | if (ref $conv eq 'CODE') {
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| 50 | $val = &$conv($val, $self);
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| 51 | } else {
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| 52 | return "Can't handle $type for $tag in ApplyShift()" if ref $$tagInfo{$type};
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| 53 | #### eval ValueConv/ValueConvInv ($val, $self)
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| 54 | $val = eval $$tagInfo{$type};
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| 55 | }
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| 56 | } else {
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| 57 | next;
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| 58 | }
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| 59 | # handle errors
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| 60 | $err and return $err;
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| 61 | $@ and SetWarning($@);
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| 62 | GetWarning() and return CleanWarning();
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| 63 | }
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| 64 | # update value in new value hash
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| 65 | $nvHash->{Value} = [ $val ];
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| 66 | return undef; # success
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| 67 | }
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| 68 |
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| 69 | #------------------------------------------------------------------------------
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| 70 | # Check date/time shift
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| 71 | # Inputs: 0) shift type, 1) shift string (without sign)
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| 72 | # Returns: updated shift string, or undef on error (and may update shift)
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| 73 | sub CheckShift($$)
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| 74 | {
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| 75 | my ($type, $shift) = @_;
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| 76 | my $err;
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| 77 | if ($type eq 'Time') {
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| 78 | return "No shift direction" unless $shift =~ s/^(\+|-)//;
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| 79 | # do a test shift to validate the shift string
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| 80 | my $testTime = '2005:11:02 09:00:13.25-04:00';
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| 81 | $err = ShiftTime($testTime, $shift, $1 eq '+' ? 1 : -1);
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| 82 | } else {
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| 83 | $err = "Unknown shift type ($type)";
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| 84 | }
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| 85 | return $err;
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| 86 | }
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| 87 |
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| 88 | #------------------------------------------------------------------------------
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| 89 | # return the number of days in a month
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| 90 | # Inputs: 0) month number (Jan=1, may be outside range), 1) year
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| 91 | # Returns: number of days in month
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| 92 | sub DaysInMonth($$)
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| 93 | {
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| 94 | my ($mon, $year) = @_;
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| 95 | my @days = (31,28,31,30,31,30,31,31,30,31,30,31);
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| 96 | # adjust to the range [0,11]
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| 97 | while ($mon < 1) { $mon += 12; --$year; }
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| 98 | while ($mon > 12) { $mon -= 12; ++$year; }
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| 99 | # return standard number of days unless february on a leap year
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| 100 | return $days[$mon-1] unless $mon == 2 and not $year % 4;
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| 101 | # leap years don't occur on even centuries except every 400 years
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| 102 | return 29 if $year % 100 or not $year % 400;
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| 103 | return 28;
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| 104 | }
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| 105 |
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| 106 | #------------------------------------------------------------------------------
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| 107 | # split times into corresponding components: YYYY mm dd HH MM SS tzh tzm
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| 108 | # Inputs: 0) date/time or shift string 1) reference to list for returned components
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| 109 | # 2) optional reference to list of time components (if shift string)
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| 110 | # Returns: true on success
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| 111 | # Returned components are 0-Y, 1-M, 2-D, 3-hr, 4-min, 5-sec, 6-tzhr, 7-tzmin
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| 112 | sub SplitTime($$;$)
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| 113 | {
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| 114 | my ($val, $vals, $time) = @_;
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| 115 | # insert zeros if missing in shift string
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| 116 | if ($time) {
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| 117 | $val =~ s/(^|[-+:\s]):/${1}0:/g;
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| 118 | $val =~ s/:([:\s]|$)/:0$1/g;
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| 119 | }
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| 120 | # change dashes to colons in date (for XMP dates)
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| 121 | if ($val =~ s/^(\d{4})-(\d{2})-(\d{2})/$1:$2:$3/) {
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| 122 | $val =~ tr/T/ /; # change 'T' separator to ' '
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| 123 | }
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| 124 | # add space before timezone to split it into a separate word
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| 125 | $val =~ s/(\+|-)/ $1/;
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| 126 | my @words = split ' ', $val;
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| 127 | my $err = 1;
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| 128 | my @v;
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| 129 | for (;;) {
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| 130 | my $word = shift @words;
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| 131 | last unless defined $word;
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| 132 | # split word into separate numbers (allow decimal points but no signs)
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| 133 | my @vals = $word =~ /(?=\d|\.\d)\d*(?:\.\d*)?/g or last;
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| 134 | if ($word =~ /^(\+|-)/) {
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| 135 | # this is the timezone
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| 136 | (defined $v[6] or @vals > 2) and $err = 1, last;
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| 137 | my $sign = ($1 ne '-') ? 1 : -1;
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| 138 | # apply sign to both minutes and seconds
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| 139 | $v[6] = $sign * shift(@vals);
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| 140 | $v[7] = $sign * (shift(@vals) || 0);
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| 141 | } elsif ((@words and $words[0] =~ /^\d+/) or # there is a time word to follow
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| 142 | (not $time and $vals[0] =~ /^\d{3}/) or # first value is year (3 or more digits)
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| 143 | ($time and not defined $$time[3] and not defined $v[0])) # we don't have a time
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| 144 | {
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| 145 | # this is a date (must come first)
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| 146 | (@v or @vals > 3) and $err = 1, last;
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| 147 | not $time and @vals != 3 and $err = 1, last;
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| 148 | $v[2] = pop(@vals); # take day first if only one specified
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| 149 | $v[1] = pop(@vals) || 0;
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| 150 | $v[0] = pop(@vals) || 0;
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| 151 | } else {
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| 152 | # this is a time (can't come after timezone)
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| 153 | (defined $v[3] or defined $v[6] or @vals > 3) and $err = 1, last;
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| 154 | not $time and @vals != 3 and @vals != 2 and $err = 1, last;
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| 155 | $v[3] = shift(@vals); # take hour first if only one specified
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| 156 | $v[4] = shift(@vals) || 0;
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| 157 | $v[5] = shift(@vals) || 0;
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| 158 | }
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| 159 | $err = 0;
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| 160 | }
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| 161 | return 0 if $err or not @v;
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| 162 | if ($time) {
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| 163 | # zero any required shift entries which aren't yet defined
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| 164 | $v[0] = $v[1] = $v[2] = 0 if defined $$time[0] and not defined $v[0];
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| 165 | $v[3] = $v[4] = $v[5] = 0 if defined $$time[3] and not defined $v[3];
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| 166 | $v[6] = $v[7] = 0 if defined $$time[6] and not defined $v[6];
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| 167 | }
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| 168 | @$vals = @v; # return split time components
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| 169 | return 1;
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| 170 | }
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| 171 |
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| 172 | #------------------------------------------------------------------------------
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| 173 | # shift date/time by components
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| 174 | # Inputs: 0) split date/time list ref, 1) split shift list ref,
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| 175 | # 2) shift direction, 3) reference to output list of shifted components
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| 176 | # 4) number of decimal points in seconds
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| 177 | # 5) reference to return time difference due to rounding
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| 178 | # Returns: error string or undef on success
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| 179 | sub ShiftComponents($$$$$;$)
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| 180 | {
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| 181 | my ($time, $shift, $dir, $toTime, $dec, $rndPt) = @_;
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| 182 | # min/max for Y, M, D, h, m, s
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| 183 | my @min = ( 0, 1, 1, 0, 0, 0);
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| 184 | my @max = (10000,12,28,24,60,60);
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| 185 | my $i;
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| 186 | #
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| 187 | # apply the shift
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| 188 | #
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| 189 | my $c = 0;
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| 190 | for ($i=0; $i<@$time; ++$i) {
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| 191 | my $v = ($$time[$i] || 0) + $dir * ($$shift[$i] || 0) + $c;
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| 192 | # handle fractional values by propagating remainders downwards
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| 193 | if ($v != int($v) and $i < 5) {
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| 194 | my $iv = int($v);
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| 195 | $c = ($v - $iv) * $max[$i+1];
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| 196 | $v = $iv;
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| 197 | } else {
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| 198 | $c = 0;
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| 199 | }
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| 200 | $$toTime[$i] = $v;
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| 201 | }
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| 202 | # round off seconds to the required number of decimal points
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| 203 | my $sec = $$toTime[5];
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| 204 | if (defined $sec and $sec != int($sec)) {
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| 205 | my $mult = 10 ** $dec;
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| 206 | my $rndSec = int($sec * $mult + 0.5 * ($sec <=> 0)) / $mult;
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| 207 | $rndPt and $$rndPt = $sec - $rndSec;
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| 208 | $$toTime[5] = $rndSec;
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| 209 | }
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| 210 | #
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| 211 | # handle overflows, starting with least significant number first (seconds)
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| 212 | #
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| 213 | $c = 0;
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| 214 | for ($i=5; $i>=0; $i--) {
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| 215 | defined $$time[$i] or $c = 0, next;
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| 216 | # apply shift and adjust for previous overflow
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| 217 | my $v = $$toTime[$i] + $c;
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| 218 | $c = 0; # set carry to zero
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| 219 | # adjust for over/underflow
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| 220 | my ($min, $max) = ($min[$i], $max[$i]);
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| 221 | if ($v < $min) {
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| 222 | if ($i == 2) { # 2 = day of month
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| 223 | do {
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| 224 | # add number of days in previous month
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| 225 | --$c;
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| 226 | my $mon = $$toTime[$i-1] + $c;
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| 227 | $v += DaysInMonth($mon, $$toTime[$i-2]);
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| 228 | } while ($v < 1);
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| 229 | } else {
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| 230 | my $fc = ($v - $min) / $max;
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| 231 | # carry ($c) must be largest integer equal to or less than $fc
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| 232 | $c = int($fc);
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| 233 | --$c if $c > $fc;
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| 234 | $v -= $c * $max;
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| 235 | }
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| 236 | } elsif ($v >= $max + $min) {
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| 237 | if ($i == 2) {
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| 238 | for (;;) {
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| 239 | # test against number of days in current month
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| 240 | my $mon = $$toTime[$i-1] + $c;
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| 241 | my $days = DaysInMonth($mon, $$toTime[$i-2]);
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| 242 | last if $v <= $days;
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| 243 | $v -= $days;
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| 244 | ++$c;
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| 245 | last if $v <= 28;
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| 246 | }
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| 247 | } else {
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| 248 | my $fc = ($v - $max - $min) / $max;
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| 249 | # carry ($c) must be smallest integer greater than $fc
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| 250 | $c = int($fc);
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| 251 | ++$c if $c <= $fc;
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| 252 | $v -= $c * $max;
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| 253 | }
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| 254 | }
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| 255 | $$toTime[$i] = $v; # save the new value
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| 256 | }
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| 257 | # handle overflows in timezone
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| 258 | if (defined $$toTime[6]) {
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| 259 | my $m = $$toTime[6] * 60 + $$toTime[7];
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| 260 | $m += 0.5 * ($m <=> 0); # avoid round-off errors
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| 261 | $$toTime[6] = int($m / 60);
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| 262 | $$toTime[7] = int($m - $$toTime[6] * 60);
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| 263 | }
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| 264 | return undef; # success
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| 265 | }
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| 266 |
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| 267 | #------------------------------------------------------------------------------
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| 268 | # Shift date/time string
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| 269 | # Inputs: 0) date/time string, 1) shift string, 2) shift direction (+1 or -1)
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| 270 | # 3) reference to ShiftOffset hash (with Date, DateTime, Time, Timezone keys)
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| 271 | # Returns: error string or undef on success and date/time string is updated
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| 272 | sub ShiftTime($$$;$)
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| 273 | {
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| 274 | local $_;
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| 275 | my ($val, $shift, $dir, $shiftOffset) = @_;
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| 276 | my (@time, @shift, @toTime, $mode, $needShiftOffset, $dec);
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| 277 | #
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| 278 | # figure out what we are dealing with (time, date or date/time)
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| 279 | #
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| 280 | SplitTime($val, \@time) or return "Invalid time string ($val)";
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| 281 | if (defined $time[0]) {
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| 282 | $mode = defined $time[3] ? 'DateTime' : 'Date';
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| 283 | } elsif (defined $time[3]) {
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| 284 | $mode = 'Time';
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| 285 | }
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| 286 | # get number of digits after the seconds decimal point
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| 287 | if (defined $time[5] and $time[5] =~ /\.(\d+)/) {
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| 288 | $dec = length($1);
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| 289 | } else {
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| 290 | $dec = 0;
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| 291 | }
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| 292 | if ($shiftOffset) {
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| 293 | $needShiftOffset = 1 unless defined $$shiftOffset{$mode};
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| 294 | $needShiftOffset = 1 if defined $time[6] and not defined $$shiftOffset{Timezone};
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| 295 | } else {
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| 296 | $needShiftOffset = 1;
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| 297 | }
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| 298 | if ($needShiftOffset) {
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| 299 | #
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| 300 | # apply date/time shift the hard way
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| 301 | #
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| 302 | SplitTime($shift, \@shift, \@time) or return "Invalid shift string ($shift)";
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| 303 |
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| 304 | # change 'Z' timezone to '+00:00' only if necessary
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| 305 | if (@shift > 6 and @time <= 6) {
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| 306 | $time[6] = $time[7] = 0 if $val =~ s/Z$/\+00:00/;
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| 307 | }
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| 308 | my $rndDiff;
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| 309 | my $err = ShiftComponents(\@time, \@shift, $dir, \@toTime, $dec, \$rndDiff);
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| 310 | $err and return $err;
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| 311 | #
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| 312 | # calculate and save the shift offsets for next time
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| 313 | #
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| 314 | if ($shiftOffset) {
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| 315 | if (defined $time[0] or defined $time[3]) {
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| 316 | my @tm1 = (0, 0, 0, 1, 0, 2000);
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| 317 | my @tm2 = (0, 0, 0, 1, 0, 2000);
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| 318 | if (defined $time[0]) {
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| 319 | @tm1[3..5] = reverse @time[0..2];
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| 320 | @tm2[3..5] = reverse @toTime[0..2];
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| 321 | --$tm1[4]; # month should start from 0
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| 322 | --$tm2[4];
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| 323 | }
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| 324 | my $diff = 0;
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| 325 | if (defined $time[3]) {
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| 326 | @tm1[0..2] = reverse @time[3..5];
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| 327 | @tm2[0..2] = reverse @toTime[3..5];
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| 328 | # handle fractional seconds separately
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| 329 | $diff = $tm2[0] - int($tm2[0]) - ($tm1[0] - int($tm1[0]));
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| 330 | $diff += $rndDiff if defined $rndDiff; # un-do rounding
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| 331 | $tm1[0] = int($tm1[0]);
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| 332 | $tm2[0] = int($tm2[0]);
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| 333 | }
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| 334 | eval q{
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| 335 | require Time::Local;
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| 336 | $diff += Time::Local::timegm(@tm2) - Time::Local::timegm(@tm1);
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| 337 | };
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| 338 | # not a problem if we failed here since we'll just try again next time,
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| 339 | # so don't return error message
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| 340 | unless (@$) {
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| 341 | my $mode;
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| 342 | if (defined $time[0]) {
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| 343 | $mode = defined $time[3] ? 'DateTime' : 'Date';
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| 344 | } else {
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| 345 | $mode = 'Time';
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| 346 | }
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| 347 | $$shiftOffset{$mode} = $diff;
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| 348 | }
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| 349 | }
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| 350 | if (defined $time[6]) {
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| 351 | $$shiftOffset{Timezone} = ($toTime[6] - $time[6]) * 60 +
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| 352 | $toTime[7] - $time[7];
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| 353 | }
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| 354 | }
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| 355 |
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| 356 | } else {
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| 357 | #
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| 358 | # apply shift from previously calculated offsets
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| 359 | #
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| 360 | if ($$shiftOffset{Timezone} and @time <= 6) {
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| 361 | # change 'Z' timezone to '+00:00' only if necessary
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| 362 | $time[6] = $time[7] = 0 if $val =~ s/Z$/\+00:00/;
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| 363 | }
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| 364 | # apply the previous date/time shift if necessary
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| 365 | if ($mode) {
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| 366 | my @tm = (0, 0, 0, 1, 0, 2000);
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| 367 | if (defined $time[0]) {
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| 368 | @tm[3..5] = reverse @time[0..2];
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| 369 | --$tm[4]; # month should start from 0
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| 370 | }
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| 371 | @tm[0..2] = reverse @time[3..5] if defined $time[3];
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| 372 | # save fractional seconds
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| 373 | my $frac = $tm[0] - int($tm[0]);
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| 374 | $tm[0] = int($tm[0]);
|
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| 375 | my $tm;
|
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| 376 | eval q{
|
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| 377 | require Time::Local;
|
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| 378 | $tm = Time::Local::timegm(@tm) + $frac;
|
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| 379 | };
|
|---|
| 380 | $@ and return CleanWarning($@);
|
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| 381 | $tm += $$shiftOffset{$mode}; # apply the shift
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| 382 | $tm < 0 and return 'Shift results in negative time';
|
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| 383 | # save fractional seconds in shifted time
|
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| 384 | $frac = $tm - int($tm);
|
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| 385 | if ($frac) {
|
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| 386 | $tm = int($tm);
|
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| 387 | # must account for any rounding that could occur
|
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| 388 | $frac + 0.5 * 10 ** (-$dec) >= 1 and ++$tm, $frac = 0;
|
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| 389 | }
|
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| 390 | @tm = gmtime($tm);
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| 391 | @toTime = reverse @tm[0..5];
|
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| 392 | $toTime[0] += 1900;
|
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| 393 | ++$toTime[1];
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| 394 | $toTime[5] += $frac; # add the fractional seconds back in
|
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| 395 | }
|
|---|
| 396 | # apply the previous timezone shift if necessary
|
|---|
| 397 | if (defined $time[6]) {
|
|---|
| 398 | my $m = $time[6] * 60 + $time[7];
|
|---|
| 399 | $m += $$shiftOffset{Timezone};
|
|---|
| 400 | $m += 0.5 * ($m <=> 0); # avoid round-off errors
|
|---|
| 401 | $toTime[6] = int($m / 60);
|
|---|
| 402 | $toTime[7] = int($m - $toTime[6] * 60);
|
|---|
| 403 | }
|
|---|
| 404 | }
|
|---|
| 405 | #
|
|---|
| 406 | # insert shifted time components back into original string
|
|---|
| 407 | #
|
|---|
| 408 | my ($i, $err);
|
|---|
| 409 | for ($i=0; $i<@toTime; ++$i) {
|
|---|
| 410 | next unless defined $time[$i] and defined $toTime[$i];
|
|---|
| 411 | my ($v, $d, $s);
|
|---|
| 412 | if ($i != 6) { # not timezone hours
|
|---|
| 413 | last unless $val =~ /((?=\d|\.\d)\d*(\.\d*)?)/g;
|
|---|
| 414 | next if $toTime[$i] == $time[$i];
|
|---|
| 415 | $v = $1; # value
|
|---|
| 416 | $d = $2; # decimal part of value
|
|---|
| 417 | $s = ''; # no sign
|
|---|
| 418 | } else {
|
|---|
| 419 | last if $time[$i] == $toTime[$i] and $time[$i+1] == $toTime[$i+1];
|
|---|
| 420 | last unless $val =~ /((?:\+|-)(?=\d|\.\d)\d*(\.\d*)?)/g;
|
|---|
| 421 | $v = $1;
|
|---|
| 422 | $d = $2;
|
|---|
| 423 | if ($toTime[6] >= 0 and $toTime[7] >= 0) {
|
|---|
| 424 | $s = '+';
|
|---|
| 425 | } else {
|
|---|
| 426 | $s = '-';
|
|---|
| 427 | $toTime[6] = -$toTime[6];
|
|---|
| 428 | $toTime[7] = -$toTime[7];
|
|---|
| 429 | }
|
|---|
| 430 | }
|
|---|
| 431 | my $nv = $toTime[$i];
|
|---|
| 432 | my $pos = pos $val;
|
|---|
| 433 | my $len = length $v;
|
|---|
| 434 | my $sig = $len - length $s;
|
|---|
| 435 | my $dec = $d ? length($d) - 1 : 0;
|
|---|
| 436 | my $newNum = sprintf($dec ? "$s%0$sig.${dec}f" : "$s%0${sig}d", $nv);
|
|---|
| 437 | length($newNum) != $len and $err = 1;
|
|---|
| 438 | substr($val, $pos - $len, $len) = $newNum;
|
|---|
| 439 | pos($val) = $pos;
|
|---|
| 440 | }
|
|---|
| 441 | $err and return "Error packing shifted time ($val)";
|
|---|
| 442 | $_[0] = $val; # return shifted value
|
|---|
| 443 | return undef; # success!
|
|---|
| 444 | }
|
|---|
| 445 |
|
|---|
| 446 |
|
|---|
| 447 | 1; # end
|
|---|
| 448 |
|
|---|
| 449 | __END__
|
|---|
| 450 |
|
|---|
| 451 | =head1 NAME
|
|---|
| 452 |
|
|---|
| 453 | Image::ExifTool::Shift.pl - ExifTool time shifting routines
|
|---|
| 454 |
|
|---|
| 455 | =head1 DESCRIPTION
|
|---|
| 456 |
|
|---|
| 457 | This module contains routines used by ExifTool to shift date and time
|
|---|
| 458 | values.
|
|---|
| 459 |
|
|---|
| 460 | =head1 DETAILS
|
|---|
| 461 |
|
|---|
| 462 | Time shifts are applied to standard EXIF-formatted date/time values (ie.
|
|---|
| 463 | C<2005:03:14 18:55:00>). Date-only and time-only values may also be
|
|---|
| 464 | shifted, and an optional timezone (ie. C<-05:00>) is also supported. Here
|
|---|
| 465 | are some general rules and examples to explain how shift strings are
|
|---|
| 466 | interpreted:
|
|---|
| 467 |
|
|---|
| 468 | Date-only values are shifted using the following formats:
|
|---|
| 469 |
|
|---|
| 470 | 'Y:M:D' - shift date by 'Y' years, 'M' months and 'D' days
|
|---|
| 471 | 'M:D' - shift months and days only
|
|---|
| 472 | 'D' - shift specified number of days
|
|---|
| 473 |
|
|---|
| 474 | Time-only values are shifted using the following formats:
|
|---|
| 475 |
|
|---|
| 476 | 'h:m:s' - shift time by 'h' hours, 'm' minutes and 's' seconds
|
|---|
| 477 | 'h:m' - shift hours and minutes only
|
|---|
| 478 | 'h' - shift specified number of hours
|
|---|
| 479 |
|
|---|
| 480 | Timezone shifts are specified in the following formats:
|
|---|
| 481 |
|
|---|
| 482 | '+h:m' - shift timezone by 'h' hours and 'm' minutes
|
|---|
| 483 | '-h:m' - negative shift of timezone hours and minutes
|
|---|
| 484 | '+h' - shift timezone hours only
|
|---|
| 485 | '-h' - negative shift of timezone hours only
|
|---|
| 486 |
|
|---|
| 487 | A valid shift value consists of one or two arguments, separated by a space.
|
|---|
| 488 | If only one is provided, it is assumed to be a time shift when applied to a
|
|---|
| 489 | time-only or a date/time value, or a date shift when applied to a date-only
|
|---|
| 490 | value. For example:
|
|---|
| 491 |
|
|---|
| 492 | '7' - shift by 1 hour if applied to a time or date/time
|
|---|
| 493 | value, or by one day if applied to a date value
|
|---|
| 494 | '2:0' - shift 2 hours (time, date/time), or 2 months (date)
|
|---|
| 495 | '5:0:0' - shift 5 hours (time, date/time), or 5 years (date)
|
|---|
| 496 | '0:0:1' - shift 1 s (time, date/time), or 1 day (date)
|
|---|
| 497 |
|
|---|
| 498 | If two arguments are given, the date shift is first, followed by the time
|
|---|
| 499 | shift:
|
|---|
| 500 |
|
|---|
| 501 | '3:0:0 0' - shift date by 3 years
|
|---|
| 502 | '0 15:30' - shift time by 15 hours and 30 minutes
|
|---|
| 503 | '1:0:0 0:0:0+5:0' - shift date by 1 year and timezone by 5 hours
|
|---|
| 504 |
|
|---|
| 505 | A date shift is simply ignored if applied to a time value or visa versa.
|
|---|
| 506 |
|
|---|
| 507 | Numbers specified in shift fields may contain a decimal point:
|
|---|
| 508 |
|
|---|
| 509 | '1.5' - 1 hour 30 minutes (time, date/time), or 1 day (date)
|
|---|
| 510 | '2.5 0' - 2 days 12 hours (date/time), 12 hours (time) or
|
|---|
| 511 | 2 days (date)
|
|---|
| 512 |
|
|---|
| 513 | And to save typing, a zero is assumed for any missing numbers:
|
|---|
| 514 |
|
|---|
| 515 | '1::' - shift by 1 hour (time, date/time) or 1 year (date)
|
|---|
| 516 | '26:: 0' - shift date by 26 years
|
|---|
| 517 | '+:30 - shift timezone by 30 minutes
|
|---|
| 518 |
|
|---|
| 519 | Below are some specific examples applied to real date and/or time values
|
|---|
| 520 | ('Dir' is the applied shift direction: '+' is positive, '-' is negative):
|
|---|
| 521 |
|
|---|
| 522 | Original Value Shift Dir Shifted Value
|
|---|
| 523 | --------------------- ------- --- ---------------------
|
|---|
| 524 | '20:30:00' '5' + '01:30:00'
|
|---|
| 525 | '2005:01:27' '5' + '2005:02:01'
|
|---|
| 526 | '11:54:00' '2.5 0' - '23:54:00'
|
|---|
| 527 | '2005:11:02' '2.5 0' - '2005:10:31'
|
|---|
| 528 | '2005:11:02 11:54:00' '2.5 0' - '2005:10:30 23:54:00'
|
|---|
| 529 | '2004:02:28 08:00:00' '1 1.3' + '2004:02:29 09:18:00'
|
|---|
| 530 | '07:00:00' '-5' + '07:00:00'
|
|---|
| 531 | '07:00:00+01:00' '-5' + '07:00:00-04:00'
|
|---|
| 532 | '07:00:00Z' '+2:30' - '07:00:00-02:30'
|
|---|
| 533 | '1970:01:01' '35::' + '2005:01:01'
|
|---|
| 534 | '2005:01:01' '400' + '2006:02:05'
|
|---|
| 535 | '10:00:00.00' '::1.33' + '09:59:58.67'
|
|---|
| 536 |
|
|---|
| 537 | =head1 NOTES
|
|---|
| 538 |
|
|---|
| 539 | The format of the original date/time value is not changed when the time
|
|---|
| 540 | shift is applied. This means that the length of the date/time string will
|
|---|
| 541 | not change, and only the numbers in the string will be modified. The only
|
|---|
| 542 | exception to this rule is that a 'Z' timezone is changed to '+00:00'
|
|---|
| 543 | notation if a timezone shift is applied. A timezone will not be added to
|
|---|
| 544 | the date/time string.
|
|---|
| 545 |
|
|---|
| 546 | =head1 TRICKY
|
|---|
| 547 |
|
|---|
| 548 | This module is perhaps more complicated than it needs to be because it is
|
|---|
| 549 | designed to be very flexible in the way time shifts are specified and
|
|---|
| 550 | applied...
|
|---|
| 551 |
|
|---|
| 552 | The ability to shift dates by Y years, M months, etc, is somewhat
|
|---|
| 553 | contradictory to the goal of maintaining a constant shift for all time
|
|---|
| 554 | values when applying a batch shift. This is because shifting by 1 month can
|
|---|
| 555 | be equivalent to anything from 28 to 31 days, and 1 year can be 365 or 366
|
|---|
| 556 | days, depending on the starting date.
|
|---|
| 557 |
|
|---|
| 558 | The inconsistency is handled by shifting the first tag found with the actual
|
|---|
| 559 | specified shift, then calculating the equivalent time difference in seconds
|
|---|
| 560 | for this shift and applying this difference to subsequent tags in a batch
|
|---|
| 561 | conversion. So if it works as designed, the behaviour should be both
|
|---|
| 562 | intuitive and mathematically correct, and the user shouldn't have to worry
|
|---|
| 563 | about details such as this (in keeping with Perl's "do the right thing"
|
|---|
| 564 | philosophy).
|
|---|
| 565 |
|
|---|
| 566 | =head1 BUGS
|
|---|
| 567 |
|
|---|
| 568 | This feature uses the standard time library functions, which typically are
|
|---|
| 569 | limited to dates in the range 1970 to 2038.
|
|---|
| 570 |
|
|---|
| 571 | =head1 AUTHOR
|
|---|
| 572 |
|
|---|
| 573 | Copyright 2003-2011, Phil Harvey (phil at owl.phy.queensu.ca)
|
|---|
| 574 |
|
|---|
| 575 | This library is free software; you can redistribute it and/or modify it
|
|---|
| 576 | under the same terms as Perl itself.
|
|---|
| 577 |
|
|---|
| 578 | =head1 SEE ALSO
|
|---|
| 579 |
|
|---|
| 580 | L<Image::ExifTool(3pm)|Image::ExifTool>
|
|---|
| 581 |
|
|---|
| 582 | =cut
|
|---|
