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

class ClassLoader {
  private $prefixes = array();
  private $fallbackDirs = array();
  private $useIncludePath = false;
  private $classMap = array();
  public function getPrefixes() {
    return call_user_func_array('array_merge', $this->prefixes);
  }
  public function getFallbackDirs() {
    return $this->fallbackDirs;
  }
  public function getClassMap() {
    return $this->classMap;
  }

  /**
   * @param array $classMap Class to filename map
   */
  public function addClassMap(array $classMap) {
    if ($this->classMap) {
      $this->classMap = array_merge($this->classMap, $classMap);
    }
    else {
      $this->classMap = $classMap;
    }
  }

  /**
   * Registers a set of classes, merging with any others previously set.
   *
   * @param string       $prefix  The classes prefix
   * @param array|string $paths   The location(s) of the classes
   * @param bool         $prepend Prepend the location(s)
   */
  public function add($prefix, $paths, $prepend = false) {
    if (!$prefix) {
      if ($prepend) {
        $this->fallbackDirs = array_merge((array) $paths, $this->fallbackDirs);
      }
      else {
        $this->fallbackDirs = array_merge($this->fallbackDirs, (array) $paths);
      }
      return;
    }
    $first = $prefix[0];
    if (!isset($this->prefixes[$first][$prefix])) {
      $this->prefixes[$first][$prefix] = (array) $paths;
      return;
    }
    if ($prepend) {
      $this->prefixes[$first][$prefix] = array_merge((array) $paths, $this->prefixes[$first][$prefix]);
    }
    else {
      $this->prefixes[$first][$prefix] = array_merge($this->prefixes[$first][$prefix], (array) $paths);
    }
  }

  /**
   * Registers a set of classes, replacing any others previously set.
   *
   * @param string       $prefix  The classes prefix
   * @param array|string $paths   The location(s) of the classes
   */
  public function set($prefix, $paths) {
    if (!$prefix) {
      $this->fallbackDirs = (array) $paths;
      return;
    }
    $this->prefixes[substr($prefix, 0, 1)][$prefix] = (array) $paths;
  }

  /**
   * Turns on searching the include path for class files.
   *
   * @param bool $useIncludePath
   */
  public function setUseIncludePath($useIncludePath) {
    $this->useIncludePath = $useIncludePath;
  }

  /**
   * Can be used to check if the autoloader uses the include path to check
   * for classes.
   *
   * @return bool
   */
  public function getUseIncludePath() {
    return $this->useIncludePath;
  }

  /**
   * Registers this instance as an autoloader.
   *
   * @param bool $prepend Whether to prepend the autoloader or not
   */
  public function register($prepend = false) {
    spl_autoload_register(array(
      $this,
      'loadClass',
    ), true, $prepend);
  }

  /**
   * Unregisters this instance as an autoloader.
   */
  public function unregister() {
    spl_autoload_unregister(array(
      $this,
      'loadClass',
    ));
  }

  /**
   * Loads the given class or interface.
   *
   * @param  string    $class The name of the class
   * @return bool|null True if loaded, null otherwise
   */
  public function loadClass($class) {
    if ($file = $this
      ->findFile($class)) {
      include $file;
      return true;
    }
  }

  /**
   * Finds the path to the file where the class is defined.
   *
   * @param string $class The name of the class
   *
   * @return string|false The path if found, false otherwise
   */
  public function findFile($class) {

    // work around for PHP 5.3.0 - 5.3.2 https://bugs.php.net/50731
    if ('\\' == $class[0]) {
      $class = substr($class, 1);
    }
    if (isset($this->classMap[$class])) {
      return $this->classMap[$class];
    }
    if (false !== ($pos = strrpos($class, '\\'))) {

      // namespaced class name
      $classPath = strtr(substr($class, 0, $pos), '\\', DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR;
      $className = substr($class, $pos + 1);
    }
    else {

      // PEAR-like class name
      $classPath = null;
      $className = $class;
    }
    $classPath .= strtr($className, '_', DIRECTORY_SEPARATOR) . '.php';
    $first = $class[0];
    if (isset($this->prefixes[$first])) {
      foreach ($this->prefixes[$first] as $prefix => $dirs) {
        if (0 === strpos($class, $prefix)) {
          foreach ($dirs as $dir) {
            if (file_exists($dir . DIRECTORY_SEPARATOR . $classPath)) {
              return $dir . DIRECTORY_SEPARATOR . $classPath;
            }
          }
        }
      }
    }
    foreach ($this->fallbackDirs as $dir) {
      if (file_exists($dir . DIRECTORY_SEPARATOR . $classPath)) {
        return $dir . DIRECTORY_SEPARATOR . $classPath;
      }
    }
    if ($this->useIncludePath && ($file = stream_resolve_include_path($classPath))) {
      return $file;
    }
    return $this->classMap[$class] = false;
  }

}