public static Number::validStep($value, $step, $offset = 0.0)
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 $offset: (optional) An offset, to which the difference must be a multiple of the given step.
Return value
bool TRUE if no step mismatch has occurred, or FALSE otherwise.
See also
http://opensource.apple.com/source/WebCore/WebCore-1298/html/NumberInput...
File
- core/lib/Drupal/Component/Utility/Number.php, line 33
Class
- Number
- Provides helper methods for manipulating numbers.
Namespace
Drupal\Component\Utility
Code
public static function validStep($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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