* @license http://www.gnu.org/licenses/gpl.html GNU General Public
* License (GPL)
* @package PEL
*/
/**
* Class for holding a date and time.
*
* This class can hold a timestamp, and it will be used as
* in this example where the time is advanced by one week:
*
* $entry = $ifd->getEntry(PelTag::DATE_TIME_ORIGINAL);
* $time = $entry->getValue();
* print('The image was taken on the ' . date('jS', $time));
* $entry->setValue($time + 7 * 24 * 3600);
*
*
* The example used a standard UNIX timestamp, which is the default
* for this class.
*
* But the Exif format defines dates outside the range of a UNIX
* timestamp (about 1970 to 2038) and so you can also get access to
* the timestamp in two other formats: a simple string or a Julian Day
* Count. Please see the Calendar extension in the PHP Manual for more
* information about the Julian Day Count.
*
* @author Martin Geisler
* @package PEL
*/
class PelEntryTime extends PelEntryAscii
{
/**
* Constant denoting a UNIX timestamp.
*/
const UNIX_TIMESTAMP = 1;
/**
* Constant denoting a Exif string.
*/
const EXIF_STRING = 2;
/**
* Constant denoting a Julian Day Count.
*/
const JULIAN_DAY_COUNT = 3;
/**
* The Julian Day Count of the timestamp held by this entry.
*
* This is an integer counting the number of whole days since
* January 1st, 4713 B.C. The fractional part of the timestamp held
* by this entry is stored in {@link $seconds}.
*
* @var int
*/
private $day_count;
/**
* The number of seconds into the day of the timestamp held by this
* entry.
*
* The number of whole days is stored in {@link $day_count} and the
* number of seconds left-over is stored here.
*
* @var int
*/
private $seconds;
/**
* Make a new entry for holding a timestamp.
*
* @param integer $tag
* the Exif tag which this entry represents. There are
* only three standard tags which hold timestamp, so this should be
* one of the constants {@link PelTag::DATE_TIME}, {@link
* PelTag::DATE_TIME_ORIGINAL}, or {@link
* PelTag::DATE_TIME_DIGITIZED}.
*
* @param integer $timestamp
* the timestamp held by this entry in the correct form
* as indicated by the third argument. For {@link UNIX_TIMESTAMP}
* this is an integer counting the number of seconds since January
* 1st 1970, for {@link EXIF_STRING} this is a string of the form
* 'YYYY:MM:DD hh:mm:ss', and for {@link JULIAN_DAY_COUNT} this is a
* floating point number where the integer part denotes the day
* count and the fractional part denotes the time of day (0.25 means
* 6:00, 0.75 means 18:00).
*
* @param integer $type
* the type of the timestamp. This must be one of
* {@link UNIX_TIMESTAMP}, {@link EXIF_STRING}, or
* {@link JULIAN_DAY_COUNT}.
*/
public function __construct($tag, $timestamp, $type = self::UNIX_TIMESTAMP)
{
parent::__construct($tag);
$this->setValue($timestamp, $type);
}
/**
* Return the timestamp of the entry.
*
* The timestamp held by this entry is returned in one of three
* formats: as a standard UNIX timestamp (default), as a fractional
* Julian Day Count, or as a string.
*
* @param integer $type
* the type of the timestamp. This must be one of
* {@link UNIX_TIMESTAMP}, {@link EXIF_STRING}, or
* {@link JULIAN_DAY_COUNT}.
*
* @return integer the timestamp held by this entry in the correct form
* as indicated by the type argument. For {@link UNIX_TIMESTAMP}
* this is an integer counting the number of seconds since January
* 1st 1970, for {@link EXIF_STRING} this is a string of the form
* 'YYYY:MM:DD hh:mm:ss', and for {@link JULIAN_DAY_COUNT} this is a
* floating point number where the integer part denotes the day
* count and the fractional part denotes the time of day (0.25 means
* 6:00, 0.75 means 18:00).
*/
public function getValue($type = self::UNIX_TIMESTAMP)
{
switch ($type) {
case self::UNIX_TIMESTAMP:
$seconds = $this->convertJdToUnix($this->day_count);
if ($seconds === false) {
/*
* We get false if the Julian Day Count is outside the range
* of a UNIX timestamp.
*/
return false;
} else {
return $seconds + $this->seconds;
}
break;
case self::EXIF_STRING:
list ($year, $month, $day) = $this->convertJdToGregorian($this->day_count);
$hours = (int) ($this->seconds / 3600);
$minutes = (int) ($this->seconds % 3600 / 60);
$seconds = $this->seconds % 60;
return sprintf('%04d:%02d:%02d %02d:%02d:%02d', $year, $month, $day, $hours, $minutes, $seconds);
case self::JULIAN_DAY_COUNT:
return $this->day_count + $this->seconds / 86400;
default:
throw new PelInvalidArgumentException(
'Expected UNIX_TIMESTAMP (%d), ' . 'EXIF_STRING (%d), or ' . 'JULIAN_DAY_COUNT (%d) for $type, ' .
'got %d.',
self::UNIX_TIMESTAMP,
self::EXIF_STRING,
self::JULIAN_DAY_COUNT,
$type);
}
}
/**
* Update the timestamp held by this entry.
*
* @param integer $timestamp
* the timestamp held by this entry in the correct form
* as indicated by the third argument. For {@link UNIX_TIMESTAMP}
* this is an integer counting the number of seconds since January
* 1st 1970, for {@link EXIF_STRING} this is a string of the form
* 'YYYY:MM:DD hh:mm:ss', and for {@link JULIAN_DAY_COUNT} this is a
* floating point number where the integer part denotes the day
* count and the fractional part denotes the time of day (0.25 means
* 6:00, 0.75 means 18:00).
*
* @param integer $type
* the type of the timestamp. This must be one of
* {@link UNIX_TIMESTAMP}, {@link EXIF_STRING}, or
* {@link JULIAN_DAY_COUNT}.
*/
public function setValue($timestamp, $type = self::UNIX_TIMESTAMP)
{
switch ($type) {
case self::UNIX_TIMESTAMP:
$this->day_count = $this->convertUnixToJd($timestamp);
$this->seconds = $timestamp % 86400;
break;
case self::EXIF_STRING:
/* Clean the timestamp: some timestamps are broken other
* separators than ':' and ' '. */
$d = preg_split('/[^0-9]+/', $timestamp);
for ($i = 0; $i < 6; $i ++) {
if (empty($d[$i])) {
$d[$i] = 0;
}
}
$this->day_count = $this->convertGregorianToJd($d[0], $d[1], $d[2]);
$this->seconds = $d[3] * 3600 + $d[4] * 60 + $d[5];
break;
case self::JULIAN_DAY_COUNT:
$this->day_count = (int) floor($timestamp);
$this->seconds = (int) (86400 * ($timestamp - floor($timestamp)));
break;
default:
throw new PelInvalidArgumentException(
'Expected UNIX_TIMESTAMP (%d), ' . 'EXIF_STRING (%d), or ' . 'JULIAN_DAY_COUNT (%d) for $type, ' .
'got %d.',
self::UNIX_TIMESTAMP,
self::EXIF_STRING,
self::JULIAN_DAY_COUNT,
$type);
}
/*
* Now finally update the string which will be used when this is
* turned into bytes.
*/
parent::setValue($this->getValue(self::EXIF_STRING));
}
// The following four functions are used for converting back and
// forth between the date formats. They are used in preference to
// the ones from the PHP calendar extension to avoid having to
// fiddle with timezones and to avoid depending on the extension.
//
// See http://www.hermetic.ch/cal_stud/jdn.htm#comp for a reference.
/**
* Converts a date in year/month/day format to a Julian Day count.
*
* @param integer $year
* the year.
* @param integer $month
* the month, 1 to 12.
* @param integer $day
* the day in the month.
* @return integer the Julian Day count.
*/
public function convertGregorianToJd($year, $month, $day)
{
// Special case mapping 0/0/0 -> 0
if ($year == 0 || $month == 0 || $day == 0) {
return 0;
}
$m1412 = ($month <= 2) ? - 1 : 0;
return floor((1461 * ($year + 4800 + $m1412)) / 4) + floor((367 * ($month - 2 - 12 * $m1412)) / 12) -
floor((3 * floor(($year + 4900 + $m1412) / 100)) / 4) + $day - 32075;
}
/**
* Converts a Julian Day count to a year/month/day triple.
*
* @param
* int the Julian Day count.
* @return array an array with three entries: year, month, day.
*/
public function convertJdToGregorian($jd)
{
// Special case mapping 0 -> 0/0/0
if ($jd == 0) {
return array(
0,
0,
0
);
}
$l = $jd + 68569;
$n = floor((4 * $l) / 146097);
$l = $l - floor((146097 * $n + 3) / 4);
$i = floor((4000 * ($l + 1)) / 1461001);
$l = $l - floor((1461 * $i) / 4) + 31;
$j = floor((80 * $l) / 2447);
$d = $l - floor((2447 * $j) / 80);
$l = floor($j / 11);
$m = $j + 2 - (12 * $l);
$y = 100 * ($n - 49) + $i + $l;
return array(
$y,
$m,
$d
);
}
/**
* Converts a UNIX timestamp to a Julian Day count.
*
* @param integer $timestamp
* the timestamp.
* @return integer the Julian Day count.
*/
public function convertUnixToJd($timestamp)
{
return (int) (floor($timestamp / 86400) + 2440588);
}
/**
* Converts a Julian Day count to a UNIX timestamp.
*
* @param integer $jd
* the Julian Day count.
*
* @return mixed $timestamp the integer timestamp or false if the
* day count cannot be represented as a UNIX timestamp.
*/
public function convertJdToUnix($jd)
{
if ($jd > 0) {
$timestamp = ($jd - 2440588) * 86400;
if ($timestamp >= 0) {
return $timestamp;
}
}
return false;
}
}