Chris@0: <?php
Chris@0: 
Chris@0: namespace Drupal\Component\Utility;
Chris@0: 
Chris@0: /**
Chris@0:  * Provides helper methods for manipulating numbers.
Chris@0:  *
Chris@0:  * @ingroup utility
Chris@0:  */
Chris@0: class Number {
Chris@0: 
Chris@0:   /**
Chris@0:    * Verifies that a number is a multiple of a given step.
Chris@0:    *
Chris@0:    * The implementation assumes it is dealing with IEEE 754 double precision
Chris@0:    * floating point numbers that are used by PHP on most systems.
Chris@0:    *
Chris@0:    * This is based on the number/range verification methods of webkit.
Chris@0:    *
Chris@0:    * @param float $value
Chris@0:    *   The value that needs to be checked.
Chris@0:    * @param float $step
Chris@0:    *   The step scale factor. Must be positive.
Chris@0:    * @param float $offset
Chris@0:    *   (optional) An offset, to which the difference must be a multiple of the
Chris@0:    *   given step.
Chris@0:    *
Chris@0:    * @return bool
Chris@0:    *   TRUE if no step mismatch has occurred, or FALSE otherwise.
Chris@0:    *
Chris@0:    * @see http://opensource.apple.com/source/WebCore/WebCore-1298/html/NumberInputType.cpp
Chris@0:    */
Chris@0:   public static function validStep($value, $step, $offset = 0.0) {
Chris@0:     $double_value = (double) abs($value - $offset);
Chris@0: 
Chris@0:     // The fractional part of a double has 53 bits. The greatest number that
Chris@0:     // could be represented with that is 2^53. If the given value is even bigger
Chris@0:     // than $step * 2^53, then dividing by $step will result in a very small
Chris@0:     // remainder. Since that remainder can't even be represented with a single
Chris@0:     // precision float the following computation of the remainder makes no sense
Chris@0:     // and we can safely ignore it instead.
Chris@0:     if ($double_value / pow(2.0, 53) > $step) {
Chris@0:       return TRUE;
Chris@0:     }
Chris@0: 
Chris@0:     // Now compute that remainder of a division by $step.
Chris@0:     $remainder = (double) abs($double_value - $step * round($double_value / $step));
Chris@0: 
Chris@0:     // $remainder is a double precision floating point number. Remainders that
Chris@0:     // can't be represented with single precision floats are acceptable. The
Chris@0:     // fractional part of a float has 24 bits. That means remainders smaller than
Chris@0:     // $step * 2^-24 are acceptable.
Chris@0:     $computed_acceptable_error = (double) ($step / pow(2.0, 24));
Chris@0: 
Chris@0:     return $computed_acceptable_error >= $remainder || $remainder >= ($step - $computed_acceptable_error);
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Generates a sorting code from an integer.
Chris@0:    *
Chris@0:    * Consists of a leading character indicating length, followed by N digits
Chris@0:    * with a numerical value in base 36 (alphadecimal). These codes can be sorted
Chris@0:    * as strings without altering numerical order.
Chris@0:    *
Chris@0:    * It goes:
Chris@0:    * 00, 01, 02, ..., 0y, 0z,
Chris@0:    * 110, 111, ... , 1zy, 1zz,
Chris@0:    * 2100, 2101, ..., 2zzy, 2zzz,
Chris@0:    * 31000, 31001, ...
Chris@0:    *
Chris@0:    * @param int $i
Chris@0:    *   The integer value to convert.
Chris@0:    *
Chris@0:    * @return string
Chris@0:    *   The alpha decimal value.
Chris@0:    *
Chris@0:    * @see \Drupal\Component\Utility\Number::alphadecimalToInt
Chris@0:    */
Chris@0:   public static function intToAlphadecimal($i = 0) {
Chris@0:     $num = base_convert((int) $i, 10, 36);
Chris@0:     $length = strlen($num);
Chris@0: 
Chris@0:     return chr($length + ord('0') - 1) . $num;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Decodes a sorting code back to an integer.
Chris@0:    *
Chris@0:    * @param string $string
Chris@0:    *   The alpha decimal value to convert
Chris@0:    *
Chris@0:    * @return int
Chris@0:    *   The integer value.
Chris@0:    *
Chris@0:    * @see \Drupal\Component\Utility\Number::intToAlphadecimal
Chris@0:    */
Chris@0:   public static function alphadecimalToInt($string = '00') {
Chris@0:     return (int) base_convert(substr($string, 1), 36, 10);
Chris@0:   }
Chris@0: 
Chris@0: }