annotate core/lib/Drupal/Component/Utility/Number.php @ 19:fa3358dc1485 tip

Add ndrum files
author Chris Cannam
date Wed, 28 Aug 2019 13:14:47 +0100
parents 4c8ae668cc8c
children
rev   line source
Chris@0 1 <?php
Chris@0 2
Chris@0 3 namespace Drupal\Component\Utility;
Chris@0 4
Chris@0 5 /**
Chris@0 6 * Provides helper methods for manipulating numbers.
Chris@0 7 *
Chris@0 8 * @ingroup utility
Chris@0 9 */
Chris@0 10 class Number {
Chris@0 11
Chris@0 12 /**
Chris@0 13 * Verifies that a number is a multiple of a given step.
Chris@0 14 *
Chris@0 15 * The implementation assumes it is dealing with IEEE 754 double precision
Chris@0 16 * floating point numbers that are used by PHP on most systems.
Chris@0 17 *
Chris@0 18 * This is based on the number/range verification methods of webkit.
Chris@0 19 *
Chris@0 20 * @param float $value
Chris@0 21 * The value that needs to be checked.
Chris@0 22 * @param float $step
Chris@0 23 * The step scale factor. Must be positive.
Chris@0 24 * @param float $offset
Chris@0 25 * (optional) An offset, to which the difference must be a multiple of the
Chris@0 26 * given step.
Chris@0 27 *
Chris@0 28 * @return bool
Chris@0 29 * TRUE if no step mismatch has occurred, or FALSE otherwise.
Chris@0 30 *
Chris@0 31 * @see http://opensource.apple.com/source/WebCore/WebCore-1298/html/NumberInputType.cpp
Chris@0 32 */
Chris@0 33 public static function validStep($value, $step, $offset = 0.0) {
Chris@0 34 $double_value = (double) abs($value - $offset);
Chris@0 35
Chris@0 36 // The fractional part of a double has 53 bits. The greatest number that
Chris@0 37 // could be represented with that is 2^53. If the given value is even bigger
Chris@0 38 // than $step * 2^53, then dividing by $step will result in a very small
Chris@0 39 // remainder. Since that remainder can't even be represented with a single
Chris@0 40 // precision float the following computation of the remainder makes no sense
Chris@0 41 // and we can safely ignore it instead.
Chris@0 42 if ($double_value / pow(2.0, 53) > $step) {
Chris@0 43 return TRUE;
Chris@0 44 }
Chris@0 45
Chris@0 46 // Now compute that remainder of a division by $step.
Chris@0 47 $remainder = (double) abs($double_value - $step * round($double_value / $step));
Chris@0 48
Chris@0 49 // $remainder is a double precision floating point number. Remainders that
Chris@0 50 // can't be represented with single precision floats are acceptable. The
Chris@0 51 // fractional part of a float has 24 bits. That means remainders smaller than
Chris@0 52 // $step * 2^-24 are acceptable.
Chris@0 53 $computed_acceptable_error = (double) ($step / pow(2.0, 24));
Chris@0 54
Chris@0 55 return $computed_acceptable_error >= $remainder || $remainder >= ($step - $computed_acceptable_error);
Chris@0 56 }
Chris@0 57
Chris@0 58 /**
Chris@0 59 * Generates a sorting code from an integer.
Chris@0 60 *
Chris@0 61 * Consists of a leading character indicating length, followed by N digits
Chris@0 62 * with a numerical value in base 36 (alphadecimal). These codes can be sorted
Chris@0 63 * as strings without altering numerical order.
Chris@0 64 *
Chris@0 65 * It goes:
Chris@0 66 * 00, 01, 02, ..., 0y, 0z,
Chris@0 67 * 110, 111, ... , 1zy, 1zz,
Chris@0 68 * 2100, 2101, ..., 2zzy, 2zzz,
Chris@0 69 * 31000, 31001, ...
Chris@0 70 *
Chris@0 71 * @param int $i
Chris@0 72 * The integer value to convert.
Chris@0 73 *
Chris@0 74 * @return string
Chris@0 75 * The alpha decimal value.
Chris@0 76 *
Chris@0 77 * @see \Drupal\Component\Utility\Number::alphadecimalToInt
Chris@0 78 */
Chris@0 79 public static function intToAlphadecimal($i = 0) {
Chris@0 80 $num = base_convert((int) $i, 10, 36);
Chris@0 81 $length = strlen($num);
Chris@0 82
Chris@0 83 return chr($length + ord('0') - 1) . $num;
Chris@0 84 }
Chris@0 85
Chris@0 86 /**
Chris@0 87 * Decodes a sorting code back to an integer.
Chris@0 88 *
Chris@0 89 * @param string $string
Chris@0 90 * The alpha decimal value to convert
Chris@0 91 *
Chris@0 92 * @return int
Chris@0 93 * The integer value.
Chris@0 94 *
Chris@0 95 * @see \Drupal\Component\Utility\Number::intToAlphadecimal
Chris@0 96 */
Chris@0 97 public static function alphadecimalToInt($string = '00') {
Chris@0 98 return (int) base_convert(substr($string, 1), 36, 10);
Chris@0 99 }
Chris@0 100
Chris@0 101 }