packages/flutter_tools/lib/src/cache.dart - mirrors/flutter - Git at Google

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import 'dart:async';
 import 'dart:io';

 import 'package:flutter_tools/src/dart/pub.dart';
 import 'package:flutter_tools/src/dart/summary.dart';
 import 'package:path/path.dart' as path;

 import 'base/context.dart';
 import 'base/logger.dart';
 import 'base/net.dart';
 import 'base/os.dart';
 import 'globals.dart';

 /// A wrapper around the `bin/cache/` directory.
 class Cache {
   /// [rootOverride] is configurable for testing.
   Cache({ Directory rootOverride }) {
     this._rootOverride = rootOverride;
   }

   Directory _rootOverride;

   // Initialized by FlutterCommandRunner on startup.
   static String flutterRoot;

   // Whether to cache artifacts for all platforms. Defaults to only caching
   // artifacts for the current platform.
   bool includeAllPlatforms = false;

   static RandomAccessFile _lock;
   static bool _lockEnabled = true;

   /// Turn off the [lock]/[releaseLockEarly] mechanism.
   ///
   /// This is used by the tests since they run simultaneously and all in one
   /// process and so it would be a mess if they had to use the lock.
   static void disableLocking() {
     _lockEnabled = false;
   }

   /// Lock the cache directory.
   ///
   /// This happens automatically on startup (see [FlutterCommandRunner.runCommand]).
   ///
   /// Normally the lock will be held until the process exits (this uses normal
   /// POSIX flock semantics). Long-lived commands should release the lock by
   /// calling [Cache.releaseLockEarly] once they are no longer touching the cache.
   static Future<Null> lock() async {
     if (!_lockEnabled)
       return null;
     assert(_lock == null);
     _lock = new File(path.join(flutterRoot, 'bin', 'cache', 'lockfile')).openSync(mode: FileMode.WRITE);
     bool locked = false;
     bool printed = false;
     while (!locked) {
       try {
         await _lock.lock();
         locked = true;
       } on FileSystemException {
         if (!printed) {
           printTrace('Waiting to be able to obtain lock of Flutter binary artifacts directory: ${_lock.path}');
           printStatus('Waiting for another flutter command to release the startup lock...');
           printed = true;
         }
         await new Future<Null>.delayed(const Duration(milliseconds: 50));
       }
     }
   }

   /// Releases the lock. This is not necessary unless the process is long-lived.
   static void releaseLockEarly() {
     if (!_lockEnabled || _lock == null)
       return;
     _lock.closeSync();
     _lock = null;
   }

   static String _dartSdkVersion;

   static String get dartSdkVersion {
     if (_dartSdkVersion == null) {
       _dartSdkVersion = Platform.version;
     }
     return _dartSdkVersion;
   }

   static String _engineRevision;

   static String get engineRevision {
     if (_engineRevision == null) {
       File revisionFile = new File(path.join(flutterRoot, 'bin', 'internal', 'engine.version'));
       if (revisionFile.existsSync())
         _engineRevision = revisionFile.readAsStringSync().trim();
     }
     return _engineRevision;
   }

   static Cache get instance => context[Cache] ?? (context[Cache] = new Cache());

   /// Return the top-level directory in the cache; this is `bin/cache`.
   Directory getRoot() {
     if (_rootOverride != null)
       return new Directory(path.join(_rootOverride.path, 'bin', 'cache'));
     else
       return new Directory(path.join(flutterRoot, 'bin', 'cache'));
   }

   /// Return a directory in the cache dir. For `pkg`, this will return `bin/cache/pkg`.
   Directory getCacheDir(String name) {
     Directory dir = new Directory(path.join(getRoot().path, name));
     if (!dir.existsSync())
       dir.createSync(recursive: true);
     return dir;
   }

   /// Return the top-level mutable directory in the cache; this is `bin/cache/artifacts`.
   Directory getCacheArtifacts() => getCacheDir('artifacts');

   /// Get a named directory from with the cache's artifact directory; for example,
   /// `material_fonts` would return `bin/cache/artifacts/material_fonts`.
   Directory getArtifactDirectory(String name) {
     return new Directory(path.join(getCacheArtifacts().path, name));
   }

   String getVersionFor(String artifactName) {
     File versionFile = new File(path.join(_rootOverride?.path ?? flutterRoot, 'bin', 'internal', '$artifactName.version'));
     return versionFile.existsSync() ? versionFile.readAsStringSync().trim() : null;
   }

   String getStampFor(String artifactName) {
     File stampFile = getStampFileFor(artifactName);
     return stampFile.existsSync() ? stampFile.readAsStringSync().trim() : null;
   }

   void setStampFor(String artifactName, String version) {
     getStampFileFor(artifactName).writeAsStringSync(version);
   }

   File getStampFileFor(String artifactName) {
     return new File(path.join(getRoot().path, '$artifactName.stamp'));
   }

   bool isUpToDate() {
     MaterialFonts materialFonts = new MaterialFonts(cache);
     FlutterEngine engine = new FlutterEngine(cache);

     return materialFonts.isUpToDate() && engine.isUpToDate();
   }

   Future<String> getThirdPartyFile(String urlStr, String serviceName, {
     bool unzip: false
   }) async {
     Uri url = Uri.parse(urlStr);
     Directory thirdPartyDir = getArtifactDirectory('third_party');

     Directory serviceDir = new Directory(path.join(thirdPartyDir.path, serviceName));
     if (!serviceDir.existsSync())
       serviceDir.createSync(recursive: true);

     File cachedFile = new File(path.join(serviceDir.path, url.pathSegments.last));
     if (!cachedFile.existsSync()) {
       try {
         await _downloadFileToCache(url, cachedFile, unzip);
       } catch (e) {
         printError('Failed to fetch third-party artifact $url: $e');
         throw e;
       }
     }

     return cachedFile.path;
   }

   Future<Null> updateAll() async {
     if (!_lockEnabled)
       return null;
     MaterialFonts materialFonts = new MaterialFonts(cache);
     if (!materialFonts.isUpToDate())
       await materialFonts.download();

     FlutterEngine engine = new FlutterEngine(cache);
     if (!engine.isUpToDate())
       await engine.download();
   }

   /// Download a file from the given url and write it to the cache.
   /// If [unzip] is true, treat the url as a zip file, and unzip it to the
   /// directory given.
   static Future<Null> _downloadFileToCache(Uri url, FileSystemEntity location, bool unzip) async {
     if (!location.parent.existsSync())
       location.parent.createSync(recursive: true);

     List<int> fileBytes = await fetchUrl(url);
     if (unzip) {
       if (location is Directory && !location.existsSync())
         location.createSync(recursive: true);

       File tempFile = new File(path.join(Directory.systemTemp.path, '${url.toString().hashCode}.zip'));
       tempFile.writeAsBytesSync(fileBytes, flush: true);
       os.unzip(tempFile, location);
       tempFile.deleteSync();
     } else {
       File file = location;
       file.writeAsBytesSync(fileBytes, flush: true);
     }
   }
 }

 class MaterialFonts {
   MaterialFonts(this.cache);

   static const String kName = 'material_fonts';

   final Cache cache;

   bool isUpToDate() {
     if (!cache.getArtifactDirectory(kName).existsSync())
       return false;
     return cache.getVersionFor(kName) == cache.getStampFor(kName);
   }

   Future<Null> download() {
     Status status = logger.startProgress('Downloading Material fonts...');

     Directory fontsDir = cache.getArtifactDirectory(kName);
     if (fontsDir.existsSync())
       fontsDir.deleteSync(recursive: true);

     return Cache._downloadFileToCache(
       Uri.parse(cache.getVersionFor(kName)), fontsDir, true
     ).then((_) {
       cache.setStampFor(kName, cache.getVersionFor(kName));
       status.stop(showElapsedTime: true);
     }).whenComplete(() {
       status.cancel();
     });
   }
 }

 class FlutterEngine {

   FlutterEngine(this.cache);

   static const String kName = 'engine';
   static const String kSkyEngine = 'sky_engine';
   static const String kSdkBundle = 'sdk.ds';

   final Cache cache;

   List<String> _getPackageDirs() => const <String>[kSkyEngine];

   List<String> _getEngineDirs() {
     List<String> dirs = <String>[
       'android-arm',
       'android-arm-profile',
       'android-arm-release',
       'android-x64',
       'android-x86',
     ];

     if (cache.includeAllPlatforms)
       dirs.addAll(<String>['ios', 'ios-profile', 'ios-release', 'linux-x64']);
     else if (Platform.isMacOS)
       dirs.addAll(<String>['ios', 'ios-profile', 'ios-release']);
     else if (Platform.isLinux)
       dirs.add('linux-x64');

     return dirs;
   }

   // Return a list of (cache directory path, download URL path) tuples.
   List<List<String>> _getToolsDirs() {
     if (cache.includeAllPlatforms)
       return <List<String>>[]
         ..addAll(_osxToolsDirs)
         ..addAll(_linuxToolsDirs);
     else if (Platform.isMacOS)
       return _osxToolsDirs;
     else if (Platform.isLinux)
       return _linuxToolsDirs;
     else
       return <List<String>>[];
   }

   List<List<String>> get _osxToolsDirs => <List<String>>[
     <String>['darwin-x64', 'darwin-x64/artifacts.zip'],
     <String>['android-arm-profile/darwin-x64', 'android-arm-profile/darwin-x64.zip'],
     <String>['android-arm-release/darwin-x64', 'android-arm-release/darwin-x64.zip'],
   ];

   List<List<String>> get _linuxToolsDirs => <List<String>>[
     <String>['linux-x64', 'linux-x64/artifacts.zip'],
     <String>['android-arm-profile/linux-x64', 'android-arm-profile/linux-x64.zip'],
     <String>['android-arm-release/linux-x64', 'android-arm-release/linux-x64.zip'],
   ];

   bool isUpToDate() {
     Directory pkgDir = cache.getCacheDir('pkg');
     for (String pkgName in _getPackageDirs()) {
       String pkgPath = path.join(pkgDir.path, pkgName);
       String dotPackagesPath = path.join(pkgPath, '.packages');
       if (!new Directory(pkgPath).existsSync())
         return false;
       if (!new File(dotPackagesPath).existsSync())
         return false;
     }

     if (!new File(path.join(pkgDir.path, kSkyEngine, kSdkBundle)).existsSync())
       return false;

     Directory engineDir = cache.getArtifactDirectory(kName);
     for (String dirName in _getEngineDirs()) {
       Directory dir = new Directory(path.join(engineDir.path, dirName));
       if (!dir.existsSync())
         return false;
     }

     for (List<String> toolsDir in _getToolsDirs()) {
       Directory dir = new Directory(path.join(engineDir.path, toolsDir[0]));
       if (!dir.existsSync())
         return false;
     }

     return cache.getVersionFor(kName) == cache.getStampFor(kName);
   }

   Future<Null> download() async {
     String engineVersion = cache.getVersionFor(kName);
     String url = 'https://storage.googleapis.com/flutter_infra/flutter/$engineVersion/';

     Directory pkgDir = cache.getCacheDir('pkg');
     for (String pkgName in _getPackageDirs()) {
       String pkgPath = path.join(pkgDir.path, pkgName);
       Directory dir = new Directory(pkgPath);
       if (dir.existsSync())
         dir.deleteSync(recursive: true);
       await _downloadItem('Downloading package $pkgName...', url + pkgName + '.zip', pkgDir);
       await pubGet(directory: pkgPath);
     }

     Status summaryStatus = logger.startProgress('Building Dart SDK summary...');
     try {
       String skyEnginePath = path.join(pkgDir.path, kSkyEngine);
       buildSkyEngineSdkSummary(skyEnginePath, kSdkBundle);
     } finally {
       summaryStatus.stop(showElapsedTime: true);
     }

     Directory engineDir = cache.getArtifactDirectory(kName);
     if (engineDir.existsSync())
       engineDir.deleteSync(recursive: true);

     for (String dirName in _getEngineDirs()) {
       Directory dir = new Directory(path.join(engineDir.path, dirName));
       await _downloadItem('Downloading engine artifacts $dirName...',
         url + dirName + '/artifacts.zip', dir);
       File frameworkZip = new File(path.join(dir.path, 'Flutter.framework.zip'));
       if (frameworkZip.existsSync()) {
         Directory framework = new Directory(path.join(dir.path, 'Flutter.framework'));
         framework.createSync();
         os.unzip(frameworkZip, framework);
       }
     }

     for (List<String> toolsDir in _getToolsDirs()) {
       String cacheDir = toolsDir[0];
       String urlPath = toolsDir[1];
       Directory dir = new Directory(path.join(engineDir.path, cacheDir));
       await _downloadItem('Downloading $cacheDir tools...', url + urlPath, dir);
       _makeFilesExecutable(dir);
     }

     cache.setStampFor(kName, cache.getVersionFor(kName));
   }

   void _makeFilesExecutable(Directory dir) {
     for (FileSystemEntity entity in dir.listSync()) {
       if (entity is File) {
         String name = path.basename(entity.path);
         if (name == 'sky_snapshot' || name == 'sky_shell')
           os.makeExecutable(entity);
       }
     }
   }

   Future<Null> _downloadItem(String message, String url, Directory dest) {
     Status status = logger.startProgress(message);
     return Cache._downloadFileToCache(Uri.parse(url), dest, true).then((_) {
       status.stop(showElapsedTime: true);
     }).whenComplete(() {
       status.cancel();
     });
   }
 }
	// Copyright 2016 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import 'dart:async';
	import 'dart:io';

	import 'package:flutter_tools/src/dart/pub.dart';
	import 'package:flutter_tools/src/dart/summary.dart';
	import 'package:path/path.dart' as path;

	import 'base/context.dart';
	import 'base/logger.dart';
	import 'base/net.dart';
	import 'base/os.dart';
	import 'globals.dart';

	/// A wrapper around the `bin/cache/` directory.
	class Cache {
	/// [rootOverride] is configurable for testing.
	Cache({ Directory rootOverride }) {
	this._rootOverride = rootOverride;
	}

	Directory _rootOverride;

	// Initialized by FlutterCommandRunner on startup.
	static String flutterRoot;

	// Whether to cache artifacts for all platforms. Defaults to only caching
	// artifacts for the current platform.
	bool includeAllPlatforms = false;

	static RandomAccessFile _lock;
	static bool _lockEnabled = true;

	/// Turn off the [lock]/[releaseLockEarly] mechanism.
	///
	/// This is used by the tests since they run simultaneously and all in one
	/// process and so it would be a mess if they had to use the lock.
	static void disableLocking() {
	_lockEnabled = false;
	}

	/// Lock the cache directory.
	///
	/// This happens automatically on startup (see [FlutterCommandRunner.runCommand]).
	///
	/// Normally the lock will be held until the process exits (this uses normal
	/// POSIX flock semantics). Long-lived commands should release the lock by
	/// calling [Cache.releaseLockEarly] once they are no longer touching the cache.
	static Future<Null> lock() async {
	if (!_lockEnabled)
	return null;
	assert(_lock == null);
	_lock = new File(path.join(flutterRoot, 'bin', 'cache', 'lockfile')).openSync(mode: FileMode.WRITE);
	bool locked = false;
	bool printed = false;
	while (!locked) {
	try {
	await _lock.lock();
	locked = true;
	} on FileSystemException {
	if (!printed) {
	printTrace('Waiting to be able to obtain lock of Flutter binary artifacts directory: ${_lock.path}');
	printStatus('Waiting for another flutter command to release the startup lock...');
	printed = true;
	}
	await new Future<Null>.delayed(const Duration(milliseconds: 50));
	}
	}
	}

	/// Releases the lock. This is not necessary unless the process is long-lived.
	static void releaseLockEarly() {
	if (!_lockEnabled \|\| _lock == null)
	return;
	_lock.closeSync();
	_lock = null;
	}

	static String _dartSdkVersion;

	static String get dartSdkVersion {
	if (_dartSdkVersion == null) {
	_dartSdkVersion = Platform.version;
	}
	return _dartSdkVersion;
	}

	static String _engineRevision;

	static String get engineRevision {
	if (_engineRevision == null) {
	File revisionFile = new File(path.join(flutterRoot, 'bin', 'internal', 'engine.version'));
	if (revisionFile.existsSync())
	_engineRevision = revisionFile.readAsStringSync().trim();
	}
	return _engineRevision;
	}

	static Cache get instance => context[Cache] ?? (context[Cache] = new Cache());

	/// Return the top-level directory in the cache; this is `bin/cache`.
	Directory getRoot() {
	if (_rootOverride != null)
	return new Directory(path.join(_rootOverride.path, 'bin', 'cache'));
	else
	return new Directory(path.join(flutterRoot, 'bin', 'cache'));
	}

	/// Return a directory in the cache dir. For `pkg`, this will return `bin/cache/pkg`.
	Directory getCacheDir(String name) {
	Directory dir = new Directory(path.join(getRoot().path, name));
	if (!dir.existsSync())
	dir.createSync(recursive: true);
	return dir;
	}

	/// Return the top-level mutable directory in the cache; this is `bin/cache/artifacts`.
	Directory getCacheArtifacts() => getCacheDir('artifacts');

	/// Get a named directory from with the cache's artifact directory; for example,
	/// `material_fonts` would return `bin/cache/artifacts/material_fonts`.
	Directory getArtifactDirectory(String name) {
	return new Directory(path.join(getCacheArtifacts().path, name));
	}

	String getVersionFor(String artifactName) {
	File versionFile = new File(path.join(_rootOverride?.path ?? flutterRoot, 'bin', 'internal', '$artifactName.version'));
	return versionFile.existsSync() ? versionFile.readAsStringSync().trim() : null;
	}

	String getStampFor(String artifactName) {
	File stampFile = getStampFileFor(artifactName);
	return stampFile.existsSync() ? stampFile.readAsStringSync().trim() : null;
	}

	void setStampFor(String artifactName, String version) {
	getStampFileFor(artifactName).writeAsStringSync(version);
	}

	File getStampFileFor(String artifactName) {
	return new File(path.join(getRoot().path, '$artifactName.stamp'));
	}

	bool isUpToDate() {
	MaterialFonts materialFonts = new MaterialFonts(cache);
	FlutterEngine engine = new FlutterEngine(cache);

	return materialFonts.isUpToDate() && engine.isUpToDate();
	}

	Future<String> getThirdPartyFile(String urlStr, String serviceName, {
	bool unzip: false
	}) async {
	Uri url = Uri.parse(urlStr);
	Directory thirdPartyDir = getArtifactDirectory('third_party');

	Directory serviceDir = new Directory(path.join(thirdPartyDir.path, serviceName));
	if (!serviceDir.existsSync())
	serviceDir.createSync(recursive: true);

	File cachedFile = new File(path.join(serviceDir.path, url.pathSegments.last));
	if (!cachedFile.existsSync()) {
	try {
	await _downloadFileToCache(url, cachedFile, unzip);
	} catch (e) {
	printError('Failed to fetch third-party artifact $url: $e');
	throw e;
	}
	}

	return cachedFile.path;
	}

	Future<Null> updateAll() async {
	if (!_lockEnabled)
	return null;
	MaterialFonts materialFonts = new MaterialFonts(cache);
	if (!materialFonts.isUpToDate())
	await materialFonts.download();

	FlutterEngine engine = new FlutterEngine(cache);
	if (!engine.isUpToDate())
	await engine.download();
	}

	/// Download a file from the given url and write it to the cache.
	/// If [unzip] is true, treat the url as a zip file, and unzip it to the
	/// directory given.
	static Future<Null> _downloadFileToCache(Uri url, FileSystemEntity location, bool unzip) async {
	if (!location.parent.existsSync())
	location.parent.createSync(recursive: true);

	List<int> fileBytes = await fetchUrl(url);
	if (unzip) {
	if (location is Directory && !location.existsSync())
	location.createSync(recursive: true);

	File tempFile = new File(path.join(Directory.systemTemp.path, '${url.toString().hashCode}.zip'));
	tempFile.writeAsBytesSync(fileBytes, flush: true);
	os.unzip(tempFile, location);
	tempFile.deleteSync();
	} else {
	File file = location;
	file.writeAsBytesSync(fileBytes, flush: true);
	}
	}
	}

	class MaterialFonts {
	MaterialFonts(this.cache);

	static const String kName = 'material_fonts';

	final Cache cache;

	bool isUpToDate() {
	if (!cache.getArtifactDirectory(kName).existsSync())
	return false;
	return cache.getVersionFor(kName) == cache.getStampFor(kName);
	}

	Future<Null> download() {
	Status status = logger.startProgress('Downloading Material fonts...');

	Directory fontsDir = cache.getArtifactDirectory(kName);
	if (fontsDir.existsSync())
	fontsDir.deleteSync(recursive: true);

	return Cache._downloadFileToCache(
	Uri.parse(cache.getVersionFor(kName)), fontsDir, true
	).then((_) {
	cache.setStampFor(kName, cache.getVersionFor(kName));
	status.stop(showElapsedTime: true);
	}).whenComplete(() {
	status.cancel();
	});
	}
	}

	class FlutterEngine {

	FlutterEngine(this.cache);

	static const String kName = 'engine';
	static const String kSkyEngine = 'sky_engine';
	static const String kSdkBundle = 'sdk.ds';

	final Cache cache;

	List<String> _getPackageDirs() => const <String>[kSkyEngine];

	List<String> _getEngineDirs() {
	List<String> dirs = <String>[
	'android-arm',
	'android-arm-profile',
	'android-arm-release',
	'android-x64',
	'android-x86',
	];

	if (cache.includeAllPlatforms)
	dirs.addAll(<String>['ios', 'ios-profile', 'ios-release', 'linux-x64']);
	else if (Platform.isMacOS)
	dirs.addAll(<String>['ios', 'ios-profile', 'ios-release']);
	else if (Platform.isLinux)
	dirs.add('linux-x64');

	return dirs;
	}

	// Return a list of (cache directory path, download URL path) tuples.
	List<List<String>> _getToolsDirs() {
	if (cache.includeAllPlatforms)
	return <List<String>>[]
	..addAll(_osxToolsDirs)
	..addAll(_linuxToolsDirs);
	else if (Platform.isMacOS)
	return _osxToolsDirs;
	else if (Platform.isLinux)
	return _linuxToolsDirs;
	else
	return <List<String>>[];
	}

	List<List<String>> get _osxToolsDirs => <List<String>>[
	<String>['darwin-x64', 'darwin-x64/artifacts.zip'],
	<String>['android-arm-profile/darwin-x64', 'android-arm-profile/darwin-x64.zip'],
	<String>['android-arm-release/darwin-x64', 'android-arm-release/darwin-x64.zip'],
	];

	List<List<String>> get _linuxToolsDirs => <List<String>>[
	<String>['linux-x64', 'linux-x64/artifacts.zip'],
	<String>['android-arm-profile/linux-x64', 'android-arm-profile/linux-x64.zip'],
	<String>['android-arm-release/linux-x64', 'android-arm-release/linux-x64.zip'],
	];

	bool isUpToDate() {
	Directory pkgDir = cache.getCacheDir('pkg');
	for (String pkgName in _getPackageDirs()) {
	String pkgPath = path.join(pkgDir.path, pkgName);
	String dotPackagesPath = path.join(pkgPath, '.packages');
	if (!new Directory(pkgPath).existsSync())
	return false;
	if (!new File(dotPackagesPath).existsSync())
	return false;
	}

	if (!new File(path.join(pkgDir.path, kSkyEngine, kSdkBundle)).existsSync())
	return false;

	Directory engineDir = cache.getArtifactDirectory(kName);
	for (String dirName in _getEngineDirs()) {
	Directory dir = new Directory(path.join(engineDir.path, dirName));
	if (!dir.existsSync())
	return false;
	}

	for (List<String> toolsDir in _getToolsDirs()) {
	Directory dir = new Directory(path.join(engineDir.path, toolsDir[0]));
	if (!dir.existsSync())
	return false;
	}

	return cache.getVersionFor(kName) == cache.getStampFor(kName);
	}

	Future<Null> download() async {
	String engineVersion = cache.getVersionFor(kName);
	String url = 'https://storage.googleapis.com/flutter_infra/flutter/$engineVersion/';

	Directory pkgDir = cache.getCacheDir('pkg');
	for (String pkgName in _getPackageDirs()) {
	String pkgPath = path.join(pkgDir.path, pkgName);
	Directory dir = new Directory(pkgPath);
	if (dir.existsSync())
	dir.deleteSync(recursive: true);
	await _downloadItem('Downloading package $pkgName...', url + pkgName + '.zip', pkgDir);
	await pubGet(directory: pkgPath);
	}

	Status summaryStatus = logger.startProgress('Building Dart SDK summary...');
	try {
	String skyEnginePath = path.join(pkgDir.path, kSkyEngine);
	buildSkyEngineSdkSummary(skyEnginePath, kSdkBundle);
	} finally {
	summaryStatus.stop(showElapsedTime: true);
	}

	Directory engineDir = cache.getArtifactDirectory(kName);
	if (engineDir.existsSync())
	engineDir.deleteSync(recursive: true);

	for (String dirName in _getEngineDirs()) {
	Directory dir = new Directory(path.join(engineDir.path, dirName));
	await _downloadItem('Downloading engine artifacts $dirName...',
	url + dirName + '/artifacts.zip', dir);
	File frameworkZip = new File(path.join(dir.path, 'Flutter.framework.zip'));
	if (frameworkZip.existsSync()) {
	Directory framework = new Directory(path.join(dir.path, 'Flutter.framework'));
	framework.createSync();
	os.unzip(frameworkZip, framework);
	}
	}

	for (List<String> toolsDir in _getToolsDirs()) {
	String cacheDir = toolsDir[0];
	String urlPath = toolsDir[1];
	Directory dir = new Directory(path.join(engineDir.path, cacheDir));
	await _downloadItem('Downloading $cacheDir tools...', url + urlPath, dir);
	_makeFilesExecutable(dir);
	}

	cache.setStampFor(kName, cache.getVersionFor(kName));
	}

	void _makeFilesExecutable(Directory dir) {
	for (FileSystemEntity entity in dir.listSync()) {
	if (entity is File) {
	String name = path.basename(entity.path);
	if (name == 'sky_snapshot' \|\| name == 'sky_shell')
	os.makeExecutable(entity);
	}
	}
	}

	Future<Null> _downloadItem(String message, String url, Directory dest) {
	Status status = logger.startProgress(message);
	return Cache._downloadFileToCache(Uri.parse(url), dest, true).then((_) {
	status.stop(showElapsedTime: true);
	}).whenComplete(() {
	status.cancel();
	});
	}
	}