__phutil_library_init__.php
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Created: Thu, May 9, 08:13

__phutil_library_init__.php
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	<?php

	/*
	* Copyright 2012 Facebook, Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	define('__LIBPHUTIL__', true);

	/**
	* @group library
	*/
	function phutil_require_module($library, $module) {
	PhutilBootloader::getInstance()->loadModule($library, $module);
	}

	/**
	* @group library
	*/
	function phutil_require_source($source) {
	PhutilBootloader::getInstance()->loadSource($source);
	}

	/**
	* @group library
	*/
	function phutil_register_library($library, $path) {
	PhutilBootloader::getInstance()->registerLibrary($library, $path);
	}

	/**
	* @group library
	*/
	function phutil_register_library_map(array $map) {
	PhutilBootloader::getInstance()->registerLibraryMap($map);
	}

	/**
	* @group library
	*/
	function phutil_load_library($path) {
	PhutilBootloader::getInstance()->loadLibrary($path);
	}

	/**
	* @group library
	*/
	final class PhutilBootloader {

	private static $instance;

	private $registeredLibraries = array();
	private $libraryMaps = array();
	private $moduleStack = array();
	private $currentLibrary = null;

	public static function getInstance() {
	if (!self::$instance) {
	self::$instance = new PhutilBootloader();
	}
	return self::$instance;
	}

	private function __construct() {
	// This method intentionally left blank.
	}

	public function registerLibrary($name, $path) {
	if (basename($path) != '__phutil_library_init__.php') {
	throw new PhutilBootloaderException(
	'Only directories with a __phutil_library_init__.php file may be '.
	'registered as libphutil libraries.');
	}

	$path = dirname($path);

	// Detect attempts to load the same library multiple times from different
	// locations. This might mean you're doing something silly like trying to
	// include two different versions of something, or it might mean you're
	// doing something subtle like running a different version of 'arc' on a
	// working copy of Arcanist.
	if (isset($this->registeredLibraries[$name])) {
	$old_path = $this->registeredLibraries[$name];
	if ($old_path != $path) {
	throw new PhutilLibraryConflictException($name, $old_path, $path);
	}
	}

	$this->registeredLibraries[$name] = $path;
	return $this;
	}

	public function registerLibraryMap(array $map) {
	$this->libraryMaps[$this->currentLibrary] = $map;
	return $this;
	}

	public function getLibraryMap($name) {
	if (empty($this->libraryMaps[$name])) {
	$root = $this->getLibraryRoot($name);
	$this->currentLibrary = $name;
	$okay = include $root.'/__phutil_library_map__.php';
	if (!$okay) {
	throw new PhutilBootloaderException(
	"Include of '{$root}/__phutil_library_map__.php' failed!");
	}
	}
	return $this->libraryMaps[$name];
	}

	public function getLibraryRoot($name) {
	if (empty($this->registeredLibraries[$name])) {
	throw new PhutilBootloaderException(
	"The phutil library '{$name}' has not been loaded!");
	}
	return $this->registeredLibraries[$name];
	}

	public function getAllLibraries() {
	return array_keys($this->registeredLibraries);
	}

	private function pushModuleStack($library, $module) {
	array_push($this->moduleStack, $this->getLibraryRoot($library).'/'.$module);
	return $this;
	}

	private function popModuleStack() {
	array_pop($this->moduleStack);
	}

	private function peekModuleStack() {
	return end($this->moduleStack);
	}

	public function loadLibrary($path) {
	$root = null;
	if (!empty($_SERVER['PHUTIL_LIBRARY_ROOT'])) {
	if ($path[0] != '/') {
	$root = $_SERVER['PHUTIL_LIBRARY_ROOT'];
	}
	}
	$okay = $this->executeInclude($root.$path.'/__phutil_library_init__.php');
	if (!$okay) {
	throw new PhutilBootloaderException(
	"Include of '{$path}/__phutil_library_init__.php' failed!");
	}
	}

	public function loadModule($library, $module) {
	$this->pushModuleStack($library, $module);
	phutil_require_source('__init__.php');
	$this->popModuleStack();
	}

	public function loadSource($source) {
	$base = $this->peekModuleStack();
	$okay = $this->executeInclude($base.'/'.$source);
	if (!$okay) {
	throw new PhutilBootloaderException(
	"Include of '{$base}/{$source}' failed!");
	}
	}

	public function moduleExists($library, $module) {
	$path = $this->getLibraryRoot($library);
	return @file_exists($path.'/'.$module.'/__init__.php');
	}

	private function executeInclude($path) {
	// Suppress warning spew if the file does not exist; we'll throw an
	// exception instead. We still emit error text in the case of syntax errors.
	$old = error_reporting(E_ALL & ~E_WARNING);
	$okay = include_once $path;
	error_reporting($old);

	return $okay;
	}

	}

	/**
	* @group library
	*/
	final class PhutilBootloaderException extends Exception { }


	/**
	* Thrown when you attempt to load two different copies of a library with the
	* same name. Trying to load the second copy of the library will trigger this,
	* and the library will not be loaded.
	*
	* This means you've either done something silly (like tried to explicitly load
	* two different versions of the same library into the same program -- this
	* won't work because they'll have namespace conflicts), or your configuration
	* might have some problems which caused two parts of your program to try to
	* load the same library but end up loading different copies of it, or there
	* may be some subtle issue like running 'arc' in a different Arcanist working
	* directory. (Some bootstrapping workflows like that which run low-level
	* library components on other copies of themselves are expected to fail.)
	*
	* To resolve this, you need to make sure your program loads no more than one
	* copy of each libphutil library, but exactly how you approach this depends on
	* why it's happening in the first place.
	*
	* @task info Getting Exception Information
	* @task construct Creating Library Conflict Exceptions
	* @group library
	*/
	final class PhutilLibraryConflictException extends Exception {

	private $library;
	private $oldPath;
	private $newPath;

	/**
	* Create a new library conflict exception.
	*
	* @param string The name of the library which conflicts with an existing
	* library.
	* @param string The path of the already-loaded library.
	* @param string The path of the attempting-to-load library.
	*
	* @task construct
	*/
	public function __construct($library, $old_path, $new_path) {
	$this->library = $library;
	$this->oldPath = $old_path;
	$this->newPath = $new_path;

	$message = "Library conflict! The library '{$library}' has already been ".
	"loaded (from '{$old_path}') but is now being loaded again ".
	"from a new location ('{$new_path}'). You can not load ".
	"multiple copies of the same library into a program.";

	parent::__construct($message);
	}

	/**
	* Retrieve the name of the library in conflict.
	*
	* @return string The name of the library which conflicts with an existing
	* library.
	* @task info
	*/
	public function getLibrary() {
	return $this->library;
	}


	/**
	* Get the path to the library which has already been loaded earlier in the
	* program's execution.
	*
	* @return string The path of the already-loaded library.
	* @task info
	*/
	public function getOldPath() {
	return $this->oldPath;
	}

	/**
	* Get the path to the library which is causing this conflict.
	*
	* @return string The path of the attempting-to-load library.
	* @task info
	*/
	public function getNewPath() {
	return $this->newPath;
	}
	}

	phutil_register_library('phutil', __FILE__);

	phutil_require_module('phutil', 'symbols');

	/**
	* @group library
	*/
	function __phutil_autoload($class) {
	try {
	PhutilSymbolLoader::loadClass($class);
	} catch (PhutilMissingSymbolException $ex) {
	// If there are other SPL autoloaders installed, we need to give them a
	// chance to load the class. Throw the exception if we're the last
	// autoloader; if not, swallow it and let them take a shot.
	$autoloaders = spl_autoload_functions();
	$last = end($autoloaders);
	if ($last == '__phutil_autoload') {
	throw $ex;
	}
	}
	}

	spl_autoload_register('__phutil_autoload', $throw = true);

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