class ClassLoader

1. 8.x drupal/core/vendor/composer/ClassLoader.php \Composer\Autoload\ClassLoader
2. 8.x drupal/core/vendor/doctrine/common/lib/Doctrine/Common/ClassLoader.php \Doctrine\Common\ClassLoader
3. 8.x drupal/core/vendor/symfony/class-loader/Symfony/Component/ClassLoader/ClassLoader.php \Symfony\Component\ClassLoader\ClassLoader

ClassLoaderTest.php in drupal/core/vendor/doctrine/common/tests/Doctrine/Tests/Common/ClassLoaderTest.php

class ClassLoader {

  /**
   * @var string PHP file extension
   */
  protected $fileExtension = '.php';

  /**
   * @var string Current namespace
   */
  protected $namespace;

  /**
   * @var string Current include path
   */
  protected $includePath;

  /**
   * @var string PHP namespace separator
   */
  protected $namespaceSeparator = '\\';

  /**
   * Creates a new <tt>ClassLoader</tt> that loads classes of the
   * specified namespace from the specified include path.
   *
   * If no include path is given, the ClassLoader relies on the PHP include_path.
   * If neither a namespace nor an include path is given, the ClassLoader will
   * be responsible for loading all classes, thereby relying on the PHP include_path.
   *
   * @param string $ns The namespace of the classes to load.
   * @param string $includePath The base include path to use.
   */
  public function __construct($ns = null, $includePath = null) {
    $this->namespace = $ns;
    $this->includePath = $includePath;
  }

  /**
   * Sets the namespace separator used by classes in the namespace of this ClassLoader.
   *
   * @param string $sep The separator to use.
   */
  public function setNamespaceSeparator($sep) {
    $this->namespaceSeparator = $sep;
  }

  /**
   * Gets the namespace separator used by classes in the namespace of this ClassLoader.
   *
   * @return string
   */
  public function getNamespaceSeparator() {
    return $this->namespaceSeparator;
  }

  /**
   * Sets the base include path for all class files in the namespace of this ClassLoader.
   *
   * @param string $includePath
   */
  public function setIncludePath($includePath) {
    $this->includePath = $includePath;
  }

  /**
   * Gets the base include path for all class files in the namespace of this ClassLoader.
   *
   * @return string
   */
  public function getIncludePath() {
    return $this->includePath;
  }

  /**
   * Sets the file extension of class files in the namespace of this ClassLoader.
   *
   * @param string $fileExtension
   */
  public function setFileExtension($fileExtension) {
    $this->fileExtension = $fileExtension;
  }

  /**
   * Gets the file extension of class files in the namespace of this ClassLoader.
   *
   * @return string
   */
  public function getFileExtension() {
    return $this->fileExtension;
  }

  /**
   * Registers this ClassLoader on the SPL autoload stack.
   */
  public function register() {
    spl_autoload_register(array(
      $this,
      'loadClass',
    ));
  }

  /**
   * Removes this ClassLoader from the SPL autoload stack.
   */
  public function unregister() {
    spl_autoload_unregister(array(
      $this,
      'loadClass',
    ));
  }

  /**
   * Loads the given class or interface.
   *
   * @param string $className The name of the class to load.
   * @return boolean TRUE if the class has been successfully loaded, FALSE otherwise.
   */
  public function loadClass($className) {
    if ($this->namespace !== null && strpos($className, $this->namespace . $this->namespaceSeparator) !== 0) {
      return false;
    }
    require ($this->includePath !== null ? $this->includePath . DIRECTORY_SEPARATOR : '') . str_replace($this->namespaceSeparator, DIRECTORY_SEPARATOR, $className) . $this->fileExtension;
    return true;
  }

  /**
   * Asks this ClassLoader whether it can potentially load the class (file) with
   * the given name.
   *
   * @param string $className The fully-qualified name of the class.
   * @return boolean TRUE if this ClassLoader can load the class, FALSE otherwise.
   */
  public function canLoadClass($className) {
    if ($this->namespace !== null && strpos($className, $this->namespace . $this->namespaceSeparator) !== 0) {
      return false;
    }
    $file = str_replace($this->namespaceSeparator, DIRECTORY_SEPARATOR, $className) . $this->fileExtension;
    if ($this->includePath !== null) {
      return file_exists($this->includePath . DIRECTORY_SEPARATOR . $file);
    }
    return false !== stream_resolve_include_path($file);
  }

  /**
   * Checks whether a class with a given name exists. A class "exists" if it is either
   * already defined in the current request or if there is an autoloader on the SPL
   * autoload stack that is a) responsible for the class in question and b) is able to
   * load a class file in which the class definition resides.
   *
   * If the class is not already defined, each autoloader in the SPL autoload stack
   * is asked whether it is able to tell if the class exists. If the autoloader is
   * a <tt>ClassLoader</tt>, {@link canLoadClass} is used, otherwise the autoload
   * function of the autoloader is invoked and expected to return a value that
   * evaluates to TRUE if the class (file) exists. As soon as one autoloader reports
   * that the class exists, TRUE is returned.
   *
   * Note that, depending on what kinds of autoloaders are installed on the SPL
   * autoload stack, the class (file) might already be loaded as a result of checking
   * for its existence. This is not the case with a <tt>ClassLoader</tt>, who separates
   * these responsibilities.
   *
   * @param string $className The fully-qualified name of the class.
   * @return boolean TRUE if the class exists as per the definition given above, FALSE otherwise.
   */
  public static function classExists($className) {
    if (class_exists($className, false) || interface_exists($className, false)) {
      return true;
    }
    foreach (spl_autoload_functions() as $loader) {
      if (is_array($loader)) {

        // array(???, ???)
        if (is_object($loader[0])) {
          if ($loader[0] instanceof ClassLoader) {

            // array($obj, 'methodName')
            if ($loader[0]
              ->canLoadClass($className)) {
              return true;
            }
          }
          else {
            if ($loader[0]
              ->{$loader[1]}($className)) {
              return true;
            }
          }
        }
        else {
          if ($loader[0]::$loader[1]($className)) {

            // array('ClassName', 'methodName')
            return true;
          }
        }
      }
      else {
        if ($loader instanceof \Closure) {

          // function($className) {..}
          if ($loader($className)) {
            return true;
          }
        }
        else {
          if (is_string($loader) && $loader($className)) {

            // "MyClass::loadClass"
            return true;
          }
        }
      }
    }
    return class_exists($className, false) || interface_exists($className, false);
  }

  /**
   * Gets the <tt>ClassLoader</tt> from the SPL autoload stack that is responsible
   * for (and is able to load) the class with the given name.
   *
   * @param string $className The name of the class.
   * @return ClassLoader The <tt>ClassLoader</tt> for the class or NULL if no such <tt>ClassLoader</tt> exists.
   */
  public static function getClassLoader($className) {
    foreach (spl_autoload_functions() as $loader) {
      if (is_array($loader) && $loader[0] instanceof ClassLoader && $loader[0]
        ->canLoadClass($className)) {
        return $loader[0];
      }
    }
    return null;
  }

}