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

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

   final 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 = fs.file(fs.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;
   }

   /// Checks if the current process owns the lock for the cache directory at
   /// this very moment; throws a [StateError] if it doesn't.
   static void checkLockAcquired() {
     if (_lockEnabled && _lock == null) {
       throw new StateError(
         'The current process does not own the lock for the cache directory. This is a bug in Flutter CLI tools.',
       );
     }
   }

   static String _dartSdkVersion;

   static String get dartSdkVersion => _dartSdkVersion ??= platform.version;

   static String _engineRevision;

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

   static Cache get instance => context[Cache];

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

   /// Return a directory in the cache dir. For `pkg`, this will return `bin/cache/pkg`.
   Directory getCacheDir(String name) {
     final Directory dir = fs.directory(fs.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 fs.directory(fs.path.join(getCacheArtifacts().path, name));
   }

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

   String getStampFor(String artifactName) {
     final 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 fs.file(fs.path.join(getRoot().path, '$artifactName.stamp'));
   }

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

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

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

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

     final File cachedFile = fs.file(fs.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');
         rethrow;
       }
     }

     return cachedFile.path;
   }

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

     final 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);

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

       final File tempFile = fs.file(fs.path.join(fs.systemTempDirectory.path, '${url.toString().hashCode}.zip'));
       tempFile.writeAsBytesSync(fileBytes, flush: true);
       os.unzip(tempFile, location);
       tempFile.deleteSync();
     } else {
       final 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() {
     final Status status = logger.startProgress('Downloading Material fonts...', expectSlowOperation: true);

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

     return Cache._downloadFileToCache(
       Uri.parse(cache.getVersionFor(kName)), fontsDir, true
     ).then<Null>((Null value) {
       cache.setStampFor(kName, cache.getVersionFor(kName));
       status.stop();
     }).whenComplete(status.cancel);
   }
 }

 class FlutterEngine {

   FlutterEngine(this.cache);

   static const String kName = 'engine';
   static const String kSkyEngine = 'sky_engine';

   final Cache cache;

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

   // Return a list of (cache directory path, download URL path) tuples.
   List<List<String>> _getBinaryDirs() {
     final List<List<String>> binaryDirs = <List<String>>[];

     if (cache.includeAllPlatforms)
       binaryDirs
         ..addAll(_osxBinaryDirs)
         ..addAll(_linuxBinaryDirs)
         ..addAll(_windowsBinaryDirs)
         ..addAll(_androidBinaryDirs)
         ..addAll(_iosBinaryDirs);
     else if (platform.isLinux)
       binaryDirs
         ..addAll(_linuxBinaryDirs)
         ..addAll(_androidBinaryDirs);
     else if (platform.isMacOS)
       binaryDirs
         ..addAll(_osxBinaryDirs)
         ..addAll(_androidBinaryDirs)
         ..addAll(_iosBinaryDirs);
     else if (platform.isWindows)
       binaryDirs
         ..addAll(_windowsBinaryDirs)
         ..addAll(_androidBinaryDirs);

     return binaryDirs;
   }

   List<List<String>> get _osxBinaryDirs => <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 _linuxBinaryDirs => <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'],
   ];

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

   List<List<String>> get _androidBinaryDirs => <List<String>>[
     <String>['android-x86', 'android-x86/artifacts.zip'],
     <String>['android-x64', 'android-x64/artifacts.zip'],
     <String>['android-arm', 'android-arm/artifacts.zip'],
     <String>['android-arm-profile', 'android-arm-profile/artifacts.zip'],
     <String>['android-arm-release', 'android-arm-release/artifacts.zip'],
   ];

   List<List<String>> get _iosBinaryDirs => <List<String>>[
     <String>['ios', 'ios/artifacts.zip'],
     <String>['ios-profile', 'ios-profile/artifacts.zip'],
     <String>['ios-release', 'ios-release/artifacts.zip'],
   ];

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

     final Directory engineDir = cache.getArtifactDirectory(kName);
     for (List<String> toolsDir in _getBinaryDirs()) {
       final Directory dir = fs.directory(fs.path.join(engineDir.path, toolsDir[0]));
       if (!dir.existsSync())
         return false;
     }

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

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

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

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

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

       _makeFilesExecutable(dir);

       final File frameworkZip = fs.file(fs.path.join(dir.path, 'Flutter.framework.zip'));
       if (frameworkZip.existsSync()) {
         final Directory framework = fs.directory(fs.path.join(dir.path, 'Flutter.framework'));
         framework.createSync();
         os.unzip(frameworkZip, framework);
       }
     }

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

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

   Future<Null> _downloadItem(String message, String url, Directory dest) {
     final Status status = logger.startProgress(message, expectSlowOperation: true);
     return Cache._downloadFileToCache(Uri.parse(url), dest, true).then<Null>((Null value) {
       status.stop();
     }).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 'base/context.dart';
	import 'base/file_system.dart';
	import 'base/logger.dart';
	import 'base/net.dart';
	import 'base/os.dart';
	import 'base/platform.dart';
	import 'globals.dart';

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

	final 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 = fs.file(fs.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;
	}

	/// Checks if the current process owns the lock for the cache directory at
	/// this very moment; throws a [StateError] if it doesn't.
	static void checkLockAcquired() {
	if (_lockEnabled && _lock == null) {
	throw new StateError(
	'The current process does not own the lock for the cache directory. This is a bug in Flutter CLI tools.',
	);
	}
	}

	static String _dartSdkVersion;

	static String get dartSdkVersion => _dartSdkVersion ??= platform.version;

	static String _engineRevision;

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

	static Cache get instance => context[Cache];

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

	/// Return a directory in the cache dir. For `pkg`, this will return `bin/cache/pkg`.
	Directory getCacheDir(String name) {
	final Directory dir = fs.directory(fs.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 fs.directory(fs.path.join(getCacheArtifacts().path, name));
	}

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

	String getStampFor(String artifactName) {
	final 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 fs.file(fs.path.join(getRoot().path, '$artifactName.stamp'));
	}

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

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

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

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

	final File cachedFile = fs.file(fs.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');
	rethrow;
	}
	}

	return cachedFile.path;
	}

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

	final 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);

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

	final File tempFile = fs.file(fs.path.join(fs.systemTempDirectory.path, '${url.toString().hashCode}.zip'));
	tempFile.writeAsBytesSync(fileBytes, flush: true);
	os.unzip(tempFile, location);
	tempFile.deleteSync();
	} else {
	final 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() {
	final Status status = logger.startProgress('Downloading Material fonts...', expectSlowOperation: true);

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

	return Cache._downloadFileToCache(
	Uri.parse(cache.getVersionFor(kName)), fontsDir, true
	).then<Null>((Null value) {
	cache.setStampFor(kName, cache.getVersionFor(kName));
	status.stop();
	}).whenComplete(status.cancel);
	}
	}

	class FlutterEngine {

	FlutterEngine(this.cache);

	static const String kName = 'engine';
	static const String kSkyEngine = 'sky_engine';

	final Cache cache;

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

	// Return a list of (cache directory path, download URL path) tuples.
	List<List<String>> _getBinaryDirs() {
	final List<List<String>> binaryDirs = <List<String>>[];

	if (cache.includeAllPlatforms)
	binaryDirs
	..addAll(_osxBinaryDirs)
	..addAll(_linuxBinaryDirs)
	..addAll(_windowsBinaryDirs)
	..addAll(_androidBinaryDirs)
	..addAll(_iosBinaryDirs);
	else if (platform.isLinux)
	binaryDirs
	..addAll(_linuxBinaryDirs)
	..addAll(_androidBinaryDirs);
	else if (platform.isMacOS)
	binaryDirs
	..addAll(_osxBinaryDirs)
	..addAll(_androidBinaryDirs)
	..addAll(_iosBinaryDirs);
	else if (platform.isWindows)
	binaryDirs
	..addAll(_windowsBinaryDirs)
	..addAll(_androidBinaryDirs);

	return binaryDirs;
	}

	List<List<String>> get _osxBinaryDirs => <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 _linuxBinaryDirs => <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'],
	];

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

	List<List<String>> get _androidBinaryDirs => <List<String>>[
	<String>['android-x86', 'android-x86/artifacts.zip'],
	<String>['android-x64', 'android-x64/artifacts.zip'],
	<String>['android-arm', 'android-arm/artifacts.zip'],
	<String>['android-arm-profile', 'android-arm-profile/artifacts.zip'],
	<String>['android-arm-release', 'android-arm-release/artifacts.zip'],
	];

	List<List<String>> get _iosBinaryDirs => <List<String>>[
	<String>['ios', 'ios/artifacts.zip'],
	<String>['ios-profile', 'ios-profile/artifacts.zip'],
	<String>['ios-release', 'ios-release/artifacts.zip'],
	];

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

	final Directory engineDir = cache.getArtifactDirectory(kName);
	for (List<String> toolsDir in _getBinaryDirs()) {
	final Directory dir = fs.directory(fs.path.join(engineDir.path, toolsDir[0]));
	if (!dir.existsSync())
	return false;
	}

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

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

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

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

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

	_makeFilesExecutable(dir);

	final File frameworkZip = fs.file(fs.path.join(dir.path, 'Flutter.framework.zip'));
	if (frameworkZip.existsSync()) {
	final Directory framework = fs.directory(fs.path.join(dir.path, 'Flutter.framework'));
	framework.createSync();
	os.unzip(frameworkZip, framework);
	}
	}

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

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

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