File indexing completed on 2024-12-22 05:36:22

 <?php
 
 /**
  * Class for converting between different unit-lengths as specified by
  * CSS.
  */
 class HTMLPurifier_UnitConverter
 {
 
     const ENGLISH = 1;
     const METRIC = 2;
     const DIGITAL = 3;
 
     /**
      * Units information array. Units are grouped into measuring systems
      * (English, Metric), and are assigned an integer representing
      * the conversion factor between that unit and the smallest unit in
      * the system. Numeric indexes are actually magical constants that
      * encode conversion data from one system to the next, with a O(n^2)
      * constraint on memory (this is generally not a problem, since
      * the number of measuring systems is small.)
      */
     protected static $units = array(
         self::ENGLISH => array(
             'px' => 3, // This is as per CSS 2.1 and Firefox. Your mileage may vary
             'pt' => 4,
             'pc' => 48,
             'in' => 288,
             self::METRIC => array('pt', '0.352777778', 'mm'),
         ),
         self::METRIC => array(
             'mm' => 1,
             'cm' => 10,
             self::ENGLISH => array('mm', '2.83464567', 'pt'),
         ),
     );
 
     /**
      * Minimum bcmath precision for output.
      * @type int
      */
     protected $outputPrecision;
 
     /**
      * Bcmath precision for internal calculations.
      * @type int
      */
     protected $internalPrecision;
 
     /**
      * Whether or not BCMath is available.
      * @type bool
      */
     private $bcmath;
 
     public function __construct($output_precision = 4, $internal_precision = 10, $force_no_bcmath = false)
     {
         $this->outputPrecision = $output_precision;
         $this->internalPrecision = $internal_precision;
         $this->bcmath = !$force_no_bcmath && function_exists('bcmul');
     }
 
     /**
      * Converts a length object of one unit into another unit.
      * @param HTMLPurifier_Length $length
      *      Instance of HTMLPurifier_Length to convert. You must validate()
      *      it before passing it here!
      * @param string $to_unit
      *      Unit to convert to.
      * @return HTMLPurifier_Length|bool
      * @note
      *      About precision: This conversion function pays very special
      *      attention to the incoming precision of values and attempts
      *      to maintain a number of significant figure. Results are
      *      fairly accurate up to nine digits. Some caveats:
      *          - If a number is zero-padded as a result of this significant
      *            figure tracking, the zeroes will be eliminated.
      *          - If a number contains less than four sigfigs ($outputPrecision)
      *            and this causes some decimals to be excluded, those
      *            decimals will be added on.
      */
     public function convert($length, $to_unit)
     {
         if (!$length->isValid()) {
             return false;
         }
 
         $n = $length->getN();
         $unit = $length->getUnit();
 
         if ($n === '0' || $unit === false) {
             return new HTMLPurifier_Length('0', false);
         }
 
         $state = $dest_state = false;
         foreach (self::$units as $k => $x) {
             if (isset($x[$unit])) {
                 $state = $k;
             }
             if (isset($x[$to_unit])) {
                 $dest_state = $k;
             }
         }
         if (!$state || !$dest_state) {
             return false;
         }
 
         // Some calculations about the initial precision of the number;
         // this will be useful when we need to do final rounding.
         $sigfigs = $this->getSigFigs($n);
         if ($sigfigs < $this->outputPrecision) {
             $sigfigs = $this->outputPrecision;
         }
 
         // BCMath's internal precision deals only with decimals. Use
         // our default if the initial number has no decimals, or increase
         // it by how ever many decimals, thus, the number of guard digits
         // will always be greater than or equal to internalPrecision.
         $log = (int)floor(log(abs($n), 10));
         $cp = ($log < 0) ? $this->internalPrecision - $log : $this->internalPrecision; // internal precision
 
         for ($i = 0; $i < 2; $i++) {
 
             // Determine what unit IN THIS SYSTEM we need to convert to
             if ($dest_state === $state) {
                 // Simple conversion
                 $dest_unit = $to_unit;
             } else {
                 // Convert to the smallest unit, pending a system shift
                 $dest_unit = self::$units[$state][$dest_state][0];
             }
 
             // Do the conversion if necessary
             if ($dest_unit !== $unit) {
                 $factor = $this->div(self::$units[$state][$unit], self::$units[$state][$dest_unit], $cp);
                 $n = $this->mul($n, $factor, $cp);
                 $unit = $dest_unit;
             }
 
             // Output was zero, so bail out early. Shouldn't ever happen.
             if ($n === '') {
                 $n = '0';
                 $unit = $to_unit;
                 break;
             }
 
             // It was a simple conversion, so bail out
             if ($dest_state === $state) {
                 break;
             }
 
             if ($i !== 0) {
                 // Conversion failed! Apparently, the system we forwarded
                 // to didn't have this unit. This should never happen!
                 return false;
             }
 
             // Pre-condition: $i == 0
 
             // Perform conversion to next system of units
             $n = $this->mul($n, self::$units[$state][$dest_state][1], $cp);
             $unit = self::$units[$state][$dest_state][2];
             $state = $dest_state;
 
             // One more loop around to convert the unit in the new system.
 
         }
 
         // Post-condition: $unit == $to_unit
         if ($unit !== $to_unit) {
             return false;
         }
 
         // Useful for debugging:
         //echo "<pre>n";
         //echo "$n\nsigfigs = $sigfigs\nnew_log = $new_log\nlog = $log\nrp = $rp\n</pre>\n";
 
         $n = $this->round($n, $sigfigs);
         if (strpos($n, '.') !== false) {
             $n = rtrim($n, '0');
         }
         $n = rtrim($n, '.');
 
         return new HTMLPurifier_Length($n, $unit);
     }
 
     /**
      * Returns the number of significant figures in a string number.
      * @param string $n Decimal number
      * @return int number of sigfigs
      */
     public function getSigFigs($n)
     {
         $n = ltrim($n, '0+-');
         $dp = strpos($n, '.'); // decimal position
         if ($dp === false) {
             $sigfigs = strlen(rtrim($n, '0'));
         } else {
             $sigfigs = strlen(ltrim($n, '0.')); // eliminate extra decimal character
             if ($dp !== 0) {
                 $sigfigs--;
             }
         }
         return $sigfigs;
     }
 
     /**
      * Adds two numbers, using arbitrary precision when available.
      * @param string $s1
      * @param string $s2
      * @param int $scale
      * @return string
      */
     private function add($s1, $s2, $scale)
     {
         if ($this->bcmath) {
             return bcadd($s1, $s2, $scale);
         } else {
             return $this->scale((float)$s1 + (float)$s2, $scale);
         }
     }
 
     /**
      * Multiples two numbers, using arbitrary precision when available.
      * @param string $s1
      * @param string $s2
      * @param int $scale
      * @return string
      */
     private function mul($s1, $s2, $scale)
     {
         if ($this->bcmath) {
             return bcmul($s1, $s2, $scale);
         } else {
             return $this->scale((float)$s1 * (float)$s2, $scale);
         }
     }
 
     /**
      * Divides two numbers, using arbitrary precision when available.
      * @param string $s1
      * @param string $s2
      * @param int $scale
      * @return string
      */
     private function div($s1, $s2, $scale)
     {
         if ($this->bcmath) {
             return bcdiv($s1, $s2, $scale);
         } else {
             return $this->scale((float)$s1 / (float)$s2, $scale);
         }
     }
 
     /**
      * Rounds a number according to the number of sigfigs it should have,
      * using arbitrary precision when available.
      * @param float $n
      * @param int $sigfigs
      * @return string
      */
     private function round($n, $sigfigs)
     {
         $new_log = (int)floor(log(abs($n), 10)); // Number of digits left of decimal - 1
         $rp = $sigfigs - $new_log - 1; // Number of decimal places needed
         $neg = $n < 0 ? '-' : ''; // Negative sign
         if ($this->bcmath) {
             if ($rp >= 0) {
                 $n = bcadd($n, $neg . '0.' . str_repeat('0', $rp) . '5', $rp + 1);
                 $n = bcdiv($n, '1', $rp);
             } else {
                 // This algorithm partially depends on the standardized
                 // form of numbers that comes out of bcmath.
                 $n = bcadd($n, $neg . '5' . str_repeat('0', $new_log - $sigfigs), 0);
                 $n = substr($n, 0, $sigfigs + strlen($neg)) . str_repeat('0', $new_log - $sigfigs + 1);
             }
             return $n;
         } else {
             return $this->scale(round($n, $sigfigs - $new_log - 1), $rp + 1);
         }
     }
 
     /**
      * Scales a float to $scale digits right of decimal point, like BCMath.
      * @param float $r
      * @param int $scale
      * @return string
      */
     private function scale($r, $scale)
     {
         if ($scale < 0) {
             // The f sprintf type doesn't support negative numbers, so we
             // need to cludge things manually. First get the string.
             $r = sprintf('%.0f', (float)$r);
             // Due to floating point precision loss, $r will more than likely
             // look something like 4652999999999.9234. We grab one more digit
             // than we need to precise from $r and then use that to round
             // appropriately.
             $precise = (string)round(substr($r, 0, strlen($r) + $scale), -1);
             // Now we return it, truncating the zero that was rounded off.
             return substr($precise, 0, -1) . str_repeat('0', -$scale + 1);
         }
         return sprintf('%.' . $scale . 'f', (float)$r);
     }
 }
 
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