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 'package:meta/meta.dart';

 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.
   /// [artifacts] is configurable for testing.
   Cache({ Directory rootOverride, List<CachedArtifact> artifacts }) : _rootOverride = rootOverride {
     if (artifacts == null) {
       _artifacts.add(new MaterialFonts(this));
       _artifacts.add(new FlutterEngine(this));
       _artifacts.add(new GradleWrapper(this));
     } else {
       _artifacts.addAll(artifacts);
     }
   }

   final Directory _rootOverride;
   final List<CachedArtifact> _artifacts = <CachedArtifact>[];

   // 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.
   @visibleForTesting
   static void disableLocking() {
     _lockEnabled = false;
   }

   /// Turn on the [lock]/[releaseLockEarly] mechanism.
   ///
   /// This is used by the tests.
   @visibleForTesting
   static void enableLocking() {
     _lockEnabled = true;
   }

   /// 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 = await fs.file(fs.path.join(flutterRoot, 'bin', 'cache', 'lockfile')).open(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 && platform.environment['FLUTTER_ALREADY_LOCKED'] != 'true') {
       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() => _artifacts.every((CachedArtifact artifact) => artifact.isUpToDate());

   Future<String> getThirdPartyFile(String urlStr, String serviceName) 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 _downloadFile(url, cachedFile);
       } catch (e) {
         printError('Failed to fetch third-party artifact $url: $e');
         rethrow;
       }
     }

     return cachedFile.path;
   }

   Future<Null> updateAll() async {
     if (!_lockEnabled)
       return null;
     for (CachedArtifact artifact in _artifacts) {
       if (!artifact.isUpToDate())
         await artifact.update();
     }
   }
 }

 /// An artifact managed by the cache.
 abstract class CachedArtifact {
   CachedArtifact(this.name, this.cache);

   final String name;
   final Cache cache;

   Directory get location => cache.getArtifactDirectory(name);
   String get version => cache.getVersionFor(name);

   bool isUpToDate() {
     if (!location.existsSync())
       return false;
     if (version != cache.getStampFor(name))
       return false;
     return isUpToDateInner();
   }

   Future<Null> update() async {
     if (location.existsSync())
       location.deleteSync(recursive: true);
     location.createSync(recursive: true);
     return updateInner().then<Null>((_) {
       cache.setStampFor(name, version);
     });
   }

   /// Hook method for extra checks for being up-to-date.
   bool isUpToDateInner() => true;

   /// Template method to perform artifact update.
   Future<Null> updateInner();
 }

 /// A cached artifact containing fonts used for Material Design.
 class MaterialFonts extends CachedArtifact {
   MaterialFonts(Cache cache): super('material_fonts', cache);

   @override
   Future<Null> updateInner() {
     final Status status = logger.startProgress('Downloading Material fonts...', expectSlowOperation: true);
     return _downloadZipArchive(Uri.parse(version), location).then<Null>((_) {
       status.stop();
     }).whenComplete(status.cancel);
   }
 }

 /// A cached artifact containing the Flutter engine binaries.
 class FlutterEngine extends CachedArtifact {
   FlutterEngine(Cache cache): super('engine', cache);

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

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

     binaryDirs.add(<String>['common', 'flutter_patched_sdk.zip']);

     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>['darwin-x64', 'dart-sdk-darwin-x64.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>['linux-x64', 'dart-sdk-linux-x64.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>['windows-x64', 'dart-sdk-windows-x64.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'],
   ];

   @override
   bool isUpToDateInner() {
     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;
     }

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

   @override
   Future<Null> updateInner() async {
     final String url = 'https://storage.googleapis.com/flutter_infra/flutter/$version/';

     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);
     }

     for (List<String> toolsDir in _getBinaryDirs()) {
       final String cacheDir = toolsDir[0];
       final String urlPath = toolsDir[1];
       final Directory dir = fs.directory(fs.path.join(location.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);
       }
     }
   }

   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 _downloadZipArchive(Uri.parse(url), dest).then<Null>((_) {
       status.stop();
     }).whenComplete(status.cancel);
   }
 }

 /// A cached artifact containing Gradle Wrapper scripts and binaries.
 class GradleWrapper extends CachedArtifact {
   GradleWrapper(Cache cache): super('gradle_wrapper', cache);

   @override
   Future<Null> updateInner() async {
     final Status status = logger.startProgress('Downloading Gradle Wrapper...', expectSlowOperation: true);

     final String url = 'https://android.googlesource.com'
         '/platform/tools/base/+archive/$version/templates/gradle/wrapper.tgz';
     await _downloadZippedTarball(Uri.parse(url), location).then<Null>((_) {
       // Delete property file, allowing templates to provide it.
       fs.file(fs.path.join(location.path, 'gradle', 'wrapper', 'gradle-wrapper.properties')).deleteSync();
       status.stop();
     }).whenComplete(status.cancel);
   }
 }

 /// Download a file from the given [url] and write it to [location].
 Future<Null> _downloadFile(Uri url, File location) async {
   _ensureExists(location.parent);
   final List<int> fileBytes = await fetchUrl(url);
   location.writeAsBytesSync(fileBytes, flush: true);
 }

 /// Download a zip archive from the given [url] and unzip it to [location].
 Future<Null> _downloadZipArchive(Uri url, Directory location) {
   return _withTemporaryFile('download.zip', (File tempFile) async {
     await _downloadFile(url, tempFile);
     _ensureExists(location);
     os.unzip(tempFile, location);
   });
 }

 /// Download a gzipped tarball from the given [url] and unpack it to [location].
 Future<Null> _downloadZippedTarball(Uri url, Directory location) {
   return _withTemporaryFile('download.tgz', (File tempFile) async {
     await _downloadFile(url, tempFile);
     _ensureExists(location);
     os.unpack(tempFile, location);
   });
 }

 /// Create a file with the given name in a new temporary directory, invoke
 /// [onTemporaryFile] with the file as argument, then delete the temporary
 /// directory.
 Future<Null> _withTemporaryFile(String name, Future<Null> onTemporaryFile(File file)) async {
   final Directory tempDir = fs.systemTempDirectory.createTempSync();
   final File tempFile = fs.file(fs.path.join(tempDir.path, name));
   await onTemporaryFile(tempFile).whenComplete(() {
     tempDir.delete(recursive: true);
   });
 }

 /// Create the given [directory] and parents, as necessary.
 void _ensureExists(Directory directory) {
   if (!directory.existsSync())
     directory.createSync(recursive: true);
 }
	// 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 'package:meta/meta.dart';

	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.
	/// [artifacts] is configurable for testing.
	Cache({ Directory rootOverride, List<CachedArtifact> artifacts }) : _rootOverride = rootOverride {
	if (artifacts == null) {
	_artifacts.add(new MaterialFonts(this));
	_artifacts.add(new FlutterEngine(this));
	_artifacts.add(new GradleWrapper(this));
	} else {
	_artifacts.addAll(artifacts);
	}
	}

	final Directory _rootOverride;
	final List<CachedArtifact> _artifacts = <CachedArtifact>[];

	// 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.
	@visibleForTesting
	static void disableLocking() {
	_lockEnabled = false;
	}

	/// Turn on the [lock]/[releaseLockEarly] mechanism.
	///
	/// This is used by the tests.
	@visibleForTesting
	static void enableLocking() {
	_lockEnabled = true;
	}

	/// 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 = await fs.file(fs.path.join(flutterRoot, 'bin', 'cache', 'lockfile')).open(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 && platform.environment['FLUTTER_ALREADY_LOCKED'] != 'true') {
	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() => _artifacts.every((CachedArtifact artifact) => artifact.isUpToDate());

	Future<String> getThirdPartyFile(String urlStr, String serviceName) 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 _downloadFile(url, cachedFile);
	} catch (e) {
	printError('Failed to fetch third-party artifact $url: $e');
	rethrow;
	}
	}

	return cachedFile.path;
	}

	Future<Null> updateAll() async {
	if (!_lockEnabled)
	return null;
	for (CachedArtifact artifact in _artifacts) {
	if (!artifact.isUpToDate())
	await artifact.update();
	}
	}
	}

	/// An artifact managed by the cache.
	abstract class CachedArtifact {
	CachedArtifact(this.name, this.cache);

	final String name;
	final Cache cache;

	Directory get location => cache.getArtifactDirectory(name);
	String get version => cache.getVersionFor(name);

	bool isUpToDate() {
	if (!location.existsSync())
	return false;
	if (version != cache.getStampFor(name))
	return false;
	return isUpToDateInner();
	}

	Future<Null> update() async {
	if (location.existsSync())
	location.deleteSync(recursive: true);
	location.createSync(recursive: true);
	return updateInner().then<Null>((_) {
	cache.setStampFor(name, version);
	});
	}

	/// Hook method for extra checks for being up-to-date.
	bool isUpToDateInner() => true;

	/// Template method to perform artifact update.
	Future<Null> updateInner();
	}

	/// A cached artifact containing fonts used for Material Design.
	class MaterialFonts extends CachedArtifact {
	MaterialFonts(Cache cache): super('material_fonts', cache);

	@override
	Future<Null> updateInner() {
	final Status status = logger.startProgress('Downloading Material fonts...', expectSlowOperation: true);
	return _downloadZipArchive(Uri.parse(version), location).then<Null>((_) {
	status.stop();
	}).whenComplete(status.cancel);
	}
	}

	/// A cached artifact containing the Flutter engine binaries.
	class FlutterEngine extends CachedArtifact {
	FlutterEngine(Cache cache): super('engine', cache);

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

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

	binaryDirs.add(<String>['common', 'flutter_patched_sdk.zip']);

	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>['darwin-x64', 'dart-sdk-darwin-x64.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>['linux-x64', 'dart-sdk-linux-x64.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>['windows-x64', 'dart-sdk-windows-x64.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'],
	];

	@override
	bool isUpToDateInner() {
	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;
	}

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

	@override
	Future<Null> updateInner() async {
	final String url = 'https://storage.googleapis.com/flutter_infra/flutter/$version/';

	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);
	}

	for (List<String> toolsDir in _getBinaryDirs()) {
	final String cacheDir = toolsDir[0];
	final String urlPath = toolsDir[1];
	final Directory dir = fs.directory(fs.path.join(location.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);
	}
	}
	}

	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 _downloadZipArchive(Uri.parse(url), dest).then<Null>((_) {
	status.stop();
	}).whenComplete(status.cancel);
	}
	}

	/// A cached artifact containing Gradle Wrapper scripts and binaries.
	class GradleWrapper extends CachedArtifact {
	GradleWrapper(Cache cache): super('gradle_wrapper', cache);

	@override
	Future<Null> updateInner() async {
	final Status status = logger.startProgress('Downloading Gradle Wrapper...', expectSlowOperation: true);

	final String url = 'https://android.googlesource.com'
	'/platform/tools/base/+archive/$version/templates/gradle/wrapper.tgz';
	await _downloadZippedTarball(Uri.parse(url), location).then<Null>((_) {
	// Delete property file, allowing templates to provide it.
	fs.file(fs.path.join(location.path, 'gradle', 'wrapper', 'gradle-wrapper.properties')).deleteSync();
	status.stop();
	}).whenComplete(status.cancel);
	}
	}

	/// Download a file from the given [url] and write it to [location].
	Future<Null> _downloadFile(Uri url, File location) async {
	_ensureExists(location.parent);
	final List<int> fileBytes = await fetchUrl(url);
	location.writeAsBytesSync(fileBytes, flush: true);
	}

	/// Download a zip archive from the given [url] and unzip it to [location].
	Future<Null> _downloadZipArchive(Uri url, Directory location) {
	return _withTemporaryFile('download.zip', (File tempFile) async {
	await _downloadFile(url, tempFile);
	_ensureExists(location);
	os.unzip(tempFile, location);
	});
	}

	/// Download a gzipped tarball from the given [url] and unpack it to [location].
	Future<Null> _downloadZippedTarball(Uri url, Directory location) {
	return _withTemporaryFile('download.tgz', (File tempFile) async {
	await _downloadFile(url, tempFile);
	_ensureExists(location);
	os.unpack(tempFile, location);
	});
	}

	/// Create a file with the given name in a new temporary directory, invoke
	/// [onTemporaryFile] with the file as argument, then delete the temporary
	/// directory.
	Future<Null> _withTemporaryFile(String name, Future<Null> onTemporaryFile(File file)) async {
	final Directory tempDir = fs.systemTempDirectory.createTempSync();
	final File tempFile = fs.file(fs.path.join(tempDir.path, name));
	await onTemporaryFile(tempFile).whenComplete(() {
	tempDir.delete(recursive: true);
	});
	}

	/// Create the given [directory] and parents, as necessary.
	void _ensureExists(Directory directory) {
	if (!directory.existsSync())
	directory.createSync(recursive: true);
	}