zend_loader 源码 分析

<?php
//本类的功能是为zend提供一个autoload类, 本类可算做一个示例,用户可自定义自己的autoload类,,从而替换这个类
class Zend_Loader
{
//这是autoload中用来加载一个类文件的方法,参数分别是: 类名(支持命名空间), 目录(数组或字串),先检查类是否存在,再用类名生成真正的类名和目录,再从所有目录中加载类,再
//判断本类是否加载
    public static function loadClass($class, $dirs = null)
    {
        if (class_exists($class, false) || interface_exists($class, false)) {
            return;
        }
        if ((null !== $dirs) && !is_string($dirs) && !is_array($dirs)) {
            require_once 'Zend/Exception.php';
            throw new Zend_Exception('Directory argument must be a string or an array');
        }

        $className = ltrim($class, '\\');
        $file      = '';
        $namespace = '';
        if ($lastNsPos = strripos($className, '\\')) {
            $namespace = substr($className, 0, $lastNsPos);
            $className = substr($className, $lastNsPos + 1);
            $file      = str_replace('\\', DIRECTORY_SEPARATOR, $namespace) . DIRECTORY_SEPARATOR;
        }
        $file .= str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';
        if (!empty($dirs)) {
            $dirPath = dirname($file);
            if (is_string($dirs)) {
                $dirs = explode(PATH_SEPARATOR, $dirs);
            }
            foreach ($dirs as $key => $dir) {
                if ($dir == '.') {
                    $dirs[$key] = $dirPath;
                } else {
                    $dir = rtrim($dir, '\\/');
                    $dirs[$key] = $dir . DIRECTORY_SEPARATOR . $dirPath;
                }
            }
            $file = basename($file);
            self::loadFile($file, $dirs, true);
        } else {
            self::loadFile($file, null, true);
        }
        if (!class_exists($class, false) && !interface_exists($class, false)) {
            require_once 'Zend/Exception.php';
            throw new Zend_Exception("File \"$file\" does not exist or class \"$class\" was not found in the file");
        }
    }
//加载类文件, 参数是:名字, 目录 , 是否只加载一次  原理:先把dir全部写入include_path, 然后直接 加载文件 ,最后再还原include_path
    public static function loadFile($filename, $dirs = null, $once = false)
    {
        self::_securityCheck($filename);
        /**
         * Search in provided directories, as well as include_path
         */
        $incPath = false;
        if (!empty($dirs) && (is_array($dirs) || is_string($dirs))) {
            if (is_array($dirs)) {
                $dirs = implode(PATH_SEPARATOR, $dirs);
            }
            $incPath = get_include_path();
            set_include_path($dirs . PATH_SEPARATOR . $incPath);
        }
        /**
         * Try finding for the plain filename in the include_path.
         */
        if ($once) {
            include_once $filename;
        } else {
            include $filename;
        }
        /**
         * If searching in directories, reset include_path
         */
        if ($incPath) {
            set_include_path($incPath);
        }
        return true;
    }
//判断文件是否可读,先用系统函数判断,再用
    public static function isReadable($filename)
    {
        if (is_readable($filename)) {
            // Return early if the filename is readable without needing the
            // include_path
            return true;
        }
        if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN'
            && preg_match('/^[a-z]:/i', $filename)
        ) {
            //如果文件名是一个绝对路径,并且是在windows下,按下文逻辑来看,现在就可以咔嚓了
            return false;
        }
        foreach (self::explodeIncludePath() as $path) {//用所有include_path来与类名组合,判断可读性,只要有一个可读就返回真,否则一直判断
            if ($path == '.') {
                if (is_readable($filename)) {
                    return true;
                }
                continue;
            }
            $file = $path . '/' . $filename;
            if (is_readable($file)) {
                return true;
            }
        }
        return false;
    }
//分解include_path为数组,也可以分解指定的path
    public static function explodeIncludePath($path = null)
    {
        if (null === $path) {
            $path = get_include_path();
        }
        if (PATH_SEPARATOR == ':') {
            // On *nix systems, include_paths which include paths with a stream
            // schema cannot be safely explode'd, so we have to be a bit more
            // intelligent in the approach.
            $paths = preg_split('#:(?!//)#', $path);
        } else {
            $paths = explode(PATH_SEPARATOR, $path);
        }
        return $paths;
    }
   //本方法直接调 用loadclass方法
    public static function autoload($class)
    {
        trigger_error(__CLASS__ . '::' . __METHOD__ . ' is deprecated as of 1.8.0 and will be removed with 2.0.0; use Zend_Loader_Autoloader instead', E_USER_NOTICE);
        try {
            @self::loadClass($class);
            return $class;
        } catch (Exception $e) {
            return false;
        }
    }
   //注册或取消新的autoload方法,第二个参数是注册或取消,
    public static function registerAutoload($class = 'Zend_Loader', $enabled = true)
    {
        trigger_error(__CLASS__ . '::' . __METHOD__ . ' is deprecated as of 1.8.0 and will be removed with 2.0.0; use Zend_Loader_Autoloader instead', E_USER_NOTICE);
        require_once 'Zend/Loader/Autoloader.php';
        $autoloader = Zend_Loader_Autoloader::getInstance();
        $autoloader->setFallbackAutoloader(true);
        if ('Zend_Loader' != $class) {
            self::loadClass($class);
            $methods = get_class_methods($class);
            if (!in_array('autoload', (array) $methods)) {
                require_once 'Zend/Exception.php';
                throw new Zend_Exception("The class \"$class\" does not have an autoload() method");
            }
            $callback = array($class, 'autoload');
            if ($enabled) {
                $autoloader->pushAutoloader($callback);
            } else {
                $autoloader->removeAutoloader($callback);
            }
        }
    }
   //对一个文件名的安全性检查
    protected static function _securityCheck($filename)
    {
        /**
         * Security check
         */
        if (preg_match('/[^a-z0-9\\/\\\\_.:-]/i', $filename)) {
            require_once 'Zend/Exception.php';
            throw new Zend_Exception('Security check: Illegal character in filename');
        }
    }
   //加载一个文件 , 一次或不限
    protected static function _includeFile($filespec, $once = false)
    {
        if ($once) {
            return include_once $filespec;
        } else {
            return include $filespec ;
        }
    }
}