function Number::validStep
Same name in other branches
 8.9.x core/lib/Drupal/Component/Utility/Number.php \Drupal\Component\Utility\Number::validStep()
 10 core/lib/Drupal/Component/Utility/Number.php \Drupal\Component\Utility\Number::validStep()
 11.x core/lib/Drupal/Component/Utility/Number.php \Drupal\Component\Utility\Number::validStep()
Verifies that a number is a multiple of a given step.
The implementation assumes it is dealing with IEEE 754 double precision floating point numbers that are used by PHP on most systems.
This is based on the number/range verification methods of webkit.
Parameters
float $value: The value that needs to be checked.
float $step: The step scale factor. Must be positive.
float $offset: (optional) An offset, to which the difference must be a multiple of the given step.
Return value
bool TRUE if no step mismatch has occurred, or FALSE otherwise.
See also
http://opensource.apple.com/source/WebCore/WebCore1298/html/NumberInpuâ€¦
3 calls to Number::validStep()
 Number::validateNumber in core/
lib/ Drupal/ Core/ Render/ Element/ Number.php  Form element validation handler for #type 'number'.
 NumberTest::testValidStep in core/
tests/ Drupal/ Tests/ Component/ Utility/ NumberTest.php  Tests Number::validStep() without offset.
 NumberTest::testValidStepOffset in core/
tests/ Drupal/ Tests/ Component/ Utility/ NumberTest.php  Tests Number::validStep() with offset.
File

core/
lib/ Drupal/ Component/ Utility/ Number.php, line 33
Class
 Number
 Provides helper methods for manipulating numbers.
Namespace
Drupal\Component\UtilityCode
public static function validStep($value, $step, $offset = 0.0) {
$double_value = (double) abs($value  $offset);
// The fractional part of a double has 53 bits. The greatest number that
// could be represented with that is 2^53. If the given value is even bigger
// than $step * 2^53, then dividing by $step will result in a very small
// remainder. Since that remainder can't even be represented with a single
// precision float the following computation of the remainder makes no sense
// and we can safely ignore it instead.
if ($double_value / pow(2.0, 53) > $step) {
return TRUE;
}
// Now compute that remainder of a division by $step.
$remainder = (double) abs($double_value  $step * round($double_value / $step));
// $remainder is a double precision floating point number. Remainders that
// can't be represented with single precision floats are acceptable. The
// fractional part of a float has 24 bits. That means remainders smaller than
// $step * 2^24 are acceptable.
$computed_acceptable_error = (double) ($step / pow(2.0, 24));
return $computed_acceptable_error >= $remainder  $remainder >= $step  $computed_acceptable_error;
}
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