Added a basic PSR4 and classmap autoloader.

Author: lonnieezell

system/Autoloader/Autoloader.php

@@ -0,0 +1,225 @@
+<?php namespace CodeIgniter\Autoloader;
+
+/**
+ * Class Autoloader
+ *
+ * An autoloader that uses both PSR4 autoloading, and traditional classmaps.
+ *
+ * Given a foo-bar package of classes in the file system at the following paths:
+ *
+ *      /path/to/packages/foo-bar/
+ *          /src
+ *              Baz.php         # Foo\Bar\Baz
+ *              Qux/
+ *                  Quux.php    # Foo\Bar\Qux\Quux
+ *
+ * you can add the path to the configuration array that is passed in the constructor.
+ * The config array consists of 2 primary keys, both of which are associative arrays:
+ * 'psr4', and 'classmap'.
+ *
+ *      $config = [
+ *          'psr4' => [
+ *              'Foo\Bar'   => '/path/to/packages/foo-bar'
+ *          ],
+ *          'classmap' => [
+ *              'MyClass'   => '/path/to/class/file.php'
+ *          ]
+ *      ];
+ *
+ * Example:
+ *
+ *      <?php
+ *      // our configuration array
+ *      $config = [ ... ];
+ *      $loader = new \CodeIgniter\Autoloader\Autoloader($config);
+ *
+ *      // register the autoloader
+ *      $loader->register();
+ *
+ * @package CodeIgniter\Autoloader
+ */
+class Autoloader
+{
+
+	/**
+	 * Stores namespaces as key, and path as values.
+	 *
+	 * @var array
+	 */
+	protected $prefixes = [];
+
+	/**
+	 * Stores class name as key, and path as values.
+	 *
+	 * @var array
+	 */
+	protected $classmap = [];
+
+	//--------------------------------------------------------------------
+
+	/**
+	 * Reads in the configuration array (described above) and stores
+	 * the valid parts that we'll need.
+	 *
+	 * @param $config
+	 */
+	public function __construct($config)
+	{
+		// We have to have one or the other, though we don't enforce the need
+		// to have both present in order to work.
+		if (empty($config['psr4']) && empty($config['classmap']))
+		{
+			throw new \InvalidArgumentException('Config array must contain either the \'psr4\' key or the \'classmap\' key.');
+		}
+
+		if (isset($config['psr4']))
+		{
+			$this->prefixes = $config['psr4'];
+		}
+
+		if (isset($config['classmap']))
+		{
+			$this->classmap = $config['classmap'];
+		}
+
+		unset($config);
+	}
+
+	//--------------------------------------------------------------------
+
+	/**
+	 * Register the loader with the SPL autoloader stack.
+	 */
+	public function register()
+	{
+		spl_autoload_register([$this, 'loadClass']);
+	}
+
+	//--------------------------------------------------------------------
+
+	/**
+	 * Loads the class file for a given class name.
+	 *
+	 * @param string $class The fully qualified class name.
+	 *
+	 * @return mixed            The mapped file on success, or boolean false
+	 *                          on failure.
+	 */
+	public function loadClass($class)
+	{
+		// Try loading through class map
+		$mapped_file = $this->loadFromClassmap($class);
+
+		// Nothing? Then try PSR4.
+		if ( ! $mapped_file)
+		{
+			$mapped_file = $this->loadInNamespace($class);
+		}
+
+		return $mapped_file;
+	}
+
+	//--------------------------------------------------------------------
+
+	/**
+	 * Attempts to locate the file as one in our classmap and loads it
+	 * if possible.
+	 *
+	 * @param string $class The fully-qualified class name
+	 *
+	 * @return mixed        The mapped file name on success, or boolean false on failure
+	 */
+	protected function loadFromClassmap($class)
+	{
+		if ( ! array_key_exists($class, $this->classmap))
+		{
+			return false;
+		}
+
+		if ( ! file_exists($this->classmap[$class]))
+		{
+			return false;
+		}
+
+		require $this->classmap[$class];
+
+		return $this->classmap[$class];
+	}
+
+	//--------------------------------------------------------------------
+
+	/**
+	 * Loads the class file for a given class name.
+	 *
+	 * @param string $class The fully-qualified class name
+	 *
+	 * @return mixed            The mapped file name on success, or boolean false on fail
+	 */
+	protected function loadInNamespace($class)
+	{
+		// the current namespace prefix
+		$prefix = $class;
+
+		// work backwards through the namespace names of the fully-qualified
+		// class name to find a mapped file name.
+		while (false !== $pos = strrpos($prefix, '\\'))
+		{
+			// retain trailing namespace separator in the prefix
+			$prefix = substr($class, 0, $pos + 1);
+
+			// the rest is the relative class name
+			$relative_class = substr($class, $pos + 1);
+
+			// try to load the mapped file for prefix and relative class
+			$mapped_file = $this->loadMappedFile($prefix, $relative_class);
+
+			if ($mapped_file)
+			{
+				return $mapped_file;
+			}
+
+			// remove the trailing namespace separator for the next iteration
+			// of strpos()
+			$prefix = rtrim($prefix, '\\');
+		}
+
+		// never found a mapped file
+		return false;
+	}
+
+	//--------------------------------------------------------------------
+
+	/**
+	 * Loads the mapped file for a namespace prefix and relative class.
+	 *
+	 * @param string $prefix         The namespace prefix
+	 * @param string $relative_class The relative class name
+	 *
+	 * @return mixed                    Boolean false if no mapped file can be loaded,
+	 *                                  or the name of the mapped file that was loaded.
+	 */
+	protected function loadMappedFile($prefix, $relative_class)
+	{
+		// are there any base directories for this namespace prefix?
+		if ( ! isset($this->prefixes[$prefix]))
+		{
+			return false;
+		}
+
+		// look through base directories for this namespace prefix
+		$file = $this->prefixes[$prefix].str_replace('\\', '/', $relative_class).'.php';
+
+		// if the mapped file exists, grab it
+		if (file_exists($file))
+		{
+			require $file;
+
+			return $file;
+		}
+
+		return false;
+	}
+
+	//--------------------------------------------------------------------
+
+}