[cross_file_platform_interface] Platform interface implementation of cross_file

packages/cross_file/cross_file_platform_interface/AUTHORS

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+# Below is a list of people and organizations that have contributed
+# to the Flutter project. Names should be added to the list like so:
+#
+#   Name/Organization <email address>
+
+Google LLC

packages/cross_file/cross_file_platform_interface/CHANGELOG.md

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+## 0.1.0
+
+* Initial release.

packages/cross_file/cross_file_platform_interface/LICENSE

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+Copyright 2013 The Flutter Authors
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+    * Neither the name of Google Inc. nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

packages/cross_file/cross_file_platform_interface/README.md

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+# cross_file_platform_interface
+
+A common platform interface for the [`cross_file`](https://pub.dev/packages/cross_file) plugin.
+
+This interface allows platform implementations of the `cross_file` plugin, as well as the plugin
+itself, to ensure they are supporting the same interface.
+
+# Usage
+
+To implement a new platform implementation of `cross_file`, extend
+[`CrossFilePlatform`](lib/src/cross_file_platform.dart) with an implementation that performs the
+platform-specific behavior, and when you register your plugin, set the default
+`CrossFilePlatform` by calling `CrossFilePlatform.instance = CrossFileMyPlatform()`.
+
+# Note on breaking changes
+
+Strongly prefer non-breaking changes (such as adding a method to the interface)
+over breaking changes for this package.
+
+See https://flutter.dev/go/platform-interface-breaking-changes for a discussion on why a less-clean
+interface is preferable to a breaking change.

packages/cross_file/cross_file_platform_interface/lib/cross_file_platform_interface.dart

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+// Copyright 2013 The Flutter Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+export 'src/cross_file_platform.dart';
+export 'src/file_system/platform_file_system_cross_directory.dart';
+export 'src/file_system/platform_file_system_cross_file.dart';
+export 'src/platform_cross_directory.dart';
+export 'src/platform_cross_entity.dart';
+export 'src/platform_cross_file.dart';
+export 'src/scoped_storage/platform_scoped_storage_cross_directory.dart';
+export 'src/scoped_storage/platform_scoped_storage_cross_file.dart';

packages/cross_file/cross_file_platform_interface/lib/src/cross_file_platform.dart

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+// Copyright 2013 The Flutter Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:convert';
+import 'dart:typed_data';
+
+import 'file_system/platform_file_system_cross_directory.dart';
+import 'file_system/platform_file_system_cross_file.dart';
+import 'platform_cross_directory.dart';
+import 'platform_cross_entity.dart';
+import 'scoped_storage/platform_scoped_storage_cross_directory.dart';
+import 'scoped_storage/platform_scoped_storage_cross_file.dart';
+
+/// Interface for a platform implementation of `cross_file`.
+abstract base class CrossFilePlatform {
+  /// The instance of [CrossFilePlatform] to be used.
+  ///
+  /// Platform implementations packages should set this with their own
+  /// implementation of [CrossFilePlatform] when they register themselves.
+  static CrossFilePlatform? instance;
+
+  /// Creates a new [PlatformFileSystemXFile].
+  PlatformFileSystemXFile createPlatformFileSystemXFile(
+    PlatformFileSystemXFileCreationParams params,
+  ) {
+    return _DefaultFileSystemXFile(params);
+  }
+
+  /// Creates a new [PlatformFileSystemXDirectory].
+  PlatformFileSystemXDirectory createPlatformFileSystemXDirectory(
+    PlatformFileSystemXDirectoryCreationParams params,
+  ) {
+    return _DefaultFileSystemXDirectory(params);
+  }
+
+  /// Creates a new [PlatformScopedStorageXFile].
+  PlatformScopedStorageXFile createPlatformScopedStorageXFile(
+    PlatformScopedStorageXFileCreationParams params,
+  ) {
+    return _DefaultScopedStorageXFile(params);
+  }
+
+  /// Creates a new [PlatformScopedStorageXDirectory].
+  PlatformScopedStorageXDirectory createPlatformScopedStorageXDirectory(
+    PlatformScopedStorageXDirectoryCreationParams params,
+  ) {
+    return _DefaultScopedStorageXDirectory(params);
+  }
+}
+
+/// Implementation of [PlatformFileSystemXFile] that represents a resource that
+/// does not exist.
+final class _DefaultFileSystemXFile extends PlatformFileSystemXFile {
+  _DefaultFileSystemXFile(super.params) : super.implementation();
+
+  @override
+  Future<bool> exists() async => false;
+
+  @override
+  Future<DateTime?> lastModified() async => null;
+
+  @override
+  Future<int?> length() async => null;
+
+  @override
+  Future<String?> name() async => null;
+
+  @override
+  Stream<Uint8List> openRead([int? start, int? end]) async* {
+    throw UnsupportedError('This instance does not represent any resource.');
+  }
+
+  @override
+  Future<Uint8List> readAsBytes() {
+    throw UnsupportedError('This instance does not represent any resource.');
+  }
+
+  @override
+  Future<String> readAsString({Encoding encoding = utf8}) {
+    throw UnsupportedError('This instance does not represent any resource.');
+  }
+
+  @override
+  Future<PlatformFileSystemXFile> writeAsBytes(PlatformWriteAsBytesParams params) {
+    throw UnsupportedError('This instance does not represent any resource.');
+  }
+}
+
+/// Implementation of [PlatformFileSystemXDirectory] that represents a directory
+/// that does not exist.
+final class _DefaultFileSystemXDirectory extends PlatformFileSystemXDirectory {
+  _DefaultFileSystemXDirectory(super.params) : super.implementation();
+
+  @override
+  Future<bool> exists() async => false;
+
+  @override
+  Stream<PlatformXEntity> list(PlatformListParams params) async* {
+    throw UnsupportedError('This instance does not represent any directory.');
+  }
+}
+
+/// Implementation of [PlatformScopedStorageXFile] that represents a resource
+/// that does not exist.
+final class _DefaultScopedStorageXFile extends PlatformScopedStorageXFile {
+  _DefaultScopedStorageXFile(super.params) : super.implementation();
+
+  @override
+  Future<bool> canRead() async => false;
+
+  @override
+  Future<bool> exists() async => false;
+
+  @override
+  Future<DateTime?> lastModified() async => null;
+
+  @override
+  Future<int?> length() async => null;
+
+  @override
+  Future<String?> name() async => null;
+
+  @override
+  Stream<Uint8List> openRead([int? start, int? end]) async* {
+    throw UnsupportedError('This instance does not represent any resource.');
+  }
+
+  @override
+  Future<Uint8List> readAsBytes() {
+    throw UnsupportedError('This instance does not represent any resource.');
+  }
+
+  @override
+  Future<String> readAsString({Encoding encoding = utf8}) {
+    throw UnsupportedError('This instance does not represent any resource.');
+  }
+
+  @override
+  Future<void> dispose() async {}
+}
+
+/// Implementation of [PlatformScopedStorageXDirectory] that represents a
+/// directory that does not exist.
+final class _DefaultScopedStorageXDirectory extends PlatformScopedStorageXDirectory {
+  _DefaultScopedStorageXDirectory(super.params) : super.implementation();
+
+  @override
+  Future<bool> exists() async => false;
+
+  @override
+  Future<bool> canRead() async => false;
+
+  @override
+  Stream<PlatformXEntity> list(PlatformListParams params) async* {
+    throw UnsupportedError('This instance does not represent any directory.');
+  }
+
+  @override
+  Future<void> dispose() async {}
+}

packages/cross_file/cross_file_platform_interface/lib/src/file_system/platform_file_system_cross_directory.dart

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+// Copyright 2013 The Flutter Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/foundation.dart';
+
+import '../cross_file_platform.dart';
+import '../platform_cross_directory.dart';
+
+/// Object specifying creation parameters for creating a [PlatformFileSystemXDirectory].
+///
+/// Platform-specific implementations can add additional fields by extending
+/// this class.
+///
+/// This example demonstrates how to extend the [PlatformFileSystemXDirectoryCreationParams] to
+/// provide additional platform-specific parameters.
+///
+/// When extending [PlatformFileSystemXDirectoryCreationParams] additional parameters
+/// should always accept `null` or have a default value to prevent breaking
+/// changes.
+///
+/// ```dart
+/// base class AndroidFileSystemXDirectoryCreationParams
+///     extends PlatformFileSystemXDirectoryCreationParams {
+///   AndroidFileSystemXDirectoryCreationParams({required super.uri, this.platformValue});
+///
+///   factory AndroidFileSystemXDirectoryCreationParams.fromCreationParams(
+///     PlatformFileSystemXDirectoryCreationParams params, {
+///     Object? platformValue,
+///   }) {
+///     return AndroidFileSystemXDirectoryCreationParams(
+///       uri: params.uri,
+///       platformValue: platformValue,
+///     );
+///   }
+///
+///   final Object? platformValue;
+/// }
+/// ```
+@immutable
+base class PlatformFileSystemXDirectoryCreationParams extends PlatformXDirectoryCreationParams {
+  /// Constructs a [PlatformFileSystemXDirectoryCreationParams].
+  PlatformFileSystemXDirectoryCreationParams(this.path)
+    : super(
+        uri: Uri.directory(
+          path,
+          windows: defaultTargetPlatform == TargetPlatform.windows,
+        ).toString(),
+      );
+
+  /// The path of the directory.
+  final String path;
+}
+
+/// Base mixin used to provide platform-specific features for implementations of
+/// [PlatformFileSystemXDirectory].
+///
+/// When providing platform specific features, platform implementations are
+/// expected to declare a mixin that implements this mixin and return an
+/// instance with [PlatformFileSystemXDirectory.extension].
+///
+/// ```dart
+/// base class AndroidFileSystemXDirectory extends PlatformFileSystemXDirectory with AndroidFileSystemXDirectoryExtension {
+///   // ...
+///   @override
+///   PlatformFileSystemXDirectoryExtension? get extension => this;
+///
+///   Future<void> platformMethod() {
+///     // ...
+///   }
+/// }
+///
+/// mixin AndroidFileSystemXDirectoryExtension implements PlatformFileSystemXDirectoryExtension {
+///   Future<void> platformMethod();
+/// }
+/// ```
+mixin PlatformFileSystemXDirectoryExtension implements PlatformXDirectoryExtension {}
+
+/// Interface for a reference to a directory (or folder) on the file system.
+abstract base class PlatformFileSystemXDirectory extends PlatformXDirectory {
+  /// Creates a new [PlatformFileSystemXDirectory]
+  factory PlatformFileSystemXDirectory(PlatformFileSystemXDirectoryCreationParams params) {
+    assert(
+      CrossFilePlatform.instance != null,
+      'A platform implementation for `cross_file` has not been set. Please '
+      'ensure that an implementation of `CrossFilePlatform` has been set to '
+      '`CrossFilePlatform.instance` before use. For unit testing, '
+      '`CrossFilePlatform.instance` can be set with your own test implementation.',
+    );
+    return CrossFilePlatform.instance!.createPlatformFileSystemXDirectory(params);
+  }
+
+  /// Used by the platform implementation to create a new
+  /// [PlatformFileSystemXDirectory].
+  ///
+  /// Should only be used by platform implementations because they can't extend
+  /// a class that only contains a factory constructor.
+  @protected
+  PlatformFileSystemXDirectory.implementation(
+    PlatformFileSystemXDirectoryCreationParams super.params,
+  );
+
+  @override
+  PlatformFileSystemXDirectoryCreationParams get params =>
+      super.params as PlatformFileSystemXDirectoryCreationParams;
+
+  /// Extension for providing platform-specific features.
+  @override
+  PlatformFileSystemXDirectoryExtension? get extension => null;
+}