class IsbnValidator

IsbnValidatorTest.php in drupal/core/vendor/symfony/validator/Symfony/Component/Validator/Tests/Constraints/IsbnValidatorTest.php

class IsbnValidator extends ConstraintValidator {

  /**
   * {@inheritDoc}
   */
  public function validate($value, Constraint $constraint) {
    if (null === $value || '' === $value) {
      return;
    }
    if (!is_scalar($value) && !(is_object($value) && method_exists($value, '__toString'))) {
      throw new UnexpectedTypeException($value, 'string');
    }
    if (!is_numeric($value)) {
      $value = str_replace('-', '', $value);
    }
    $validation = 0;
    $value = strtoupper($value);
    $valueLength = strlen($value);
    if (10 === $valueLength && null !== $constraint->isbn10) {
      for ($i = 0; $i < 10; $i++) {
        if ($value[$i] == 'X') {
          $validation += 10 * intval(10 - $i);
        }
        else {
          $validation += intval($value[$i]) * intval(10 - $i);
        }
      }
      if ($validation % 11 != 0) {
        if (null !== $constraint->isbn13) {
          $this->context
            ->addViolation($constraint->bothIsbnMessage);
        }
        else {
          $this->context
            ->addViolation($constraint->isbn10Message);
        }
      }
    }
    elseif (13 === $valueLength && null !== $constraint->isbn13) {
      for ($i = 0; $i < 13; $i += 2) {
        $validation += intval($value[$i]);
      }
      for ($i = 1; $i < 12; $i += 2) {
        $validation += intval($value[$i]) * 3;
      }
      if ($validation % 10 != 0) {
        if (null !== $constraint->isbn10) {
          $this->context
            ->addViolation($constraint->bothIsbnMessage);
        }
        else {
          $this->context
            ->addViolation($constraint->isbn13Message);
        }
      }
    }
    else {
      if (null !== $constraint->isbn10 && null !== $constraint->isbn13) {
        $this->context
          ->addViolation($constraint->bothIsbnMessage);
      }
      elseif (null !== $constraint->isbn10) {
        $this->context
          ->addViolation($constraint->isbn10Message);
      }
      else {
        $this->context
          ->addViolation($constraint->isbn13Message);
      }
    }
  }

}