[cross_file] An abstraction to allow working with files across multiple platforms.

CODEOWNERS

@@ -9,6 +9,7 @@ packages/android_intent/**                     @mklim @matthew-carroll
 packages/battery/**                            @amirh @matthew-carroll
 packages/camera/**                             @bparrishMines
 packages/connectivity/**                       @cyanglaz @matthew-carroll
+packages/cross_file/**                         @ditman @mvanbeusekom
 packages/device_info/**                        @matthew-carroll
 packages/espresso/**                           @collinjackson @adazh
 packages/file_selector/**                      @ditman

packages/cross_file/CHANGELOG.md

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+## 0.1.0
+
+- Initial open-source release

packages/cross_file/LICENSE

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+Copyright 2020 The Flutter Authors. All rights reserved.
+
+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/README.md

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+# cross_file
+
+An abstraction to allow working with files across multiple platforms.
+
+# Usage
+
+Import `package:cross/cross_info.dart`, instantiate a `CrossFile` 
+using a path or byte array and use its methods and properties to 
+access the file and its metadata.
+
+Example:
+
+```dart
+import 'package:cross_file/cross_file.dart';
+
+final file = CrossFile('assets/hello.txt');
+
+print('File information:');
+print('- Path: ${file.path}');
+print('- Name: ${file.name}');
+print('- MIME type: ${file.mimeType}');
+
+final fileContent = await file.readAsString();
+print('Content of the file: ${fileContent}');  // e.g. "Moto G (4)"
+```
+
+You will find links to the API docs on the [pub page](https://pub.dartlang.org/packages/cross_file).
+
+## Getting Started
+
+For help getting started with Flutter, view our online
+[documentation](http://flutter.io/).
+
+For help on editing plugin code, view the [documentation](https://flutter.io/platform-plugins/#edit-code).

packages/cross_file/lib/cross_file.dart

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+// Copyright 2018 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.
+
+export 'src/x_file.dart';

packages/cross_file/lib/src/types/base.dart

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+// Copyright 2018 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:convert';
+import 'dart:typed_data';
+
+/// The interface for a CrossFile.
+///
+/// A CrossFile is a container that wraps the path of a selected
+/// file by the user and (in some platforms, like web) the bytes
+/// with the contents of the file.
+///
+/// This class is a very limited subset of dart:io [File], so all
+/// the methods should seem familiar.
+abstract class XFileBase {
+  /// Construct a CrossFile
+  XFileBase(String path);
+
+  /// Save the CrossFile at the indicated file path.
+  void saveTo(String path) async {
+    throw UnimplementedError('saveTo has not been implemented.');
+  }
+
+  /// Get the path of the picked file.
+  ///
+  /// This should only be used as a backwards-compatibility clutch
+  /// for mobile apps, or cosmetic reasons only (to show the user
+  /// the path they've picked).
+  ///
+  /// Accessing the data contained in the picked file by its path
+  /// is platform-dependant (and won't work on web), so use the
+  /// byte getters in the CrossFile instance instead.
+  String get path {
+    throw UnimplementedError('.path has not been implemented.');
+  }
+
+  /// The name of the file as it was selected by the user in their device.
+  ///
+  /// Use only for cosmetic reasons, do not try to use this as a path.
+  String get name {
+    throw UnimplementedError('.name has not been implemented.');
+  }
+
+  /// For web, it may be necessary for a file to know its MIME type.
+  String get mimeType {
+    throw UnimplementedError('.mimeType has not been implemented.');
+  }
+
+  /// Get the length of the file. Returns a `Future<int>` that completes with the length in bytes.
+  Future<int> length() {
+    throw UnimplementedError('.length() has not been implemented.');
+  }
+
+  /// Synchronously read the entire file contents as a string using the given [Encoding].
+  ///
+  /// By default, `encoding` is [utf8].
+  ///
+  /// Throws Exception if the operation fails.
+  Future<String> readAsString({Encoding encoding = utf8}) {
+    throw UnimplementedError('readAsString() has not been implemented.');
+  }
+
+  /// Synchronously read the entire file contents as a list of bytes.
+  ///
+  /// Throws Exception if the operation fails.
+  Future<Uint8List> readAsBytes() {
+    throw UnimplementedError('readAsBytes() has not been implemented.');
+  }
+
+  /// Create a new independent [Stream] for the contents of this file.
+  ///
+  /// If `start` is present, the file will be read from byte-offset `start`. Otherwise from the beginning (index 0).
+  ///
+  /// If `end` is present, only up to byte-index `end` will be read. Otherwise, until end of file.
+  ///
+  /// In order to make sure that system resources are freed, the stream must be read to completion or the subscription on the stream must be cancelled.
+  Stream<Uint8List> openRead([int start, int end]) {
+    throw UnimplementedError('openRead() has not been implemented.');
+  }
+
+  /// Get the last-modified time for the CrossFile
+  Future<DateTime> lastModified() {
+    throw UnimplementedError('openRead() has not been implemented.');
+  }
+}

packages/cross_file/lib/src/types/html.dart

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+// Copyright 2018 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:convert';
+import 'dart:typed_data';
+
+import 'package:http/http.dart' as http show readBytes;
+import 'package:meta/meta.dart';
+import 'dart:html';
+
+import '../web_helpers/web_helpers.dart';
+import './base.dart';
+
+/// A CrossFile that works on web.
+///
+/// It wraps the bytes of a selected file.
+class XFile extends XFileBase {
+  String path;
+
+  final String mimeType;
+  final Uint8List _data;
+  final int _length;
+  final String name;
+  final DateTime _lastModified;
+  Element _target;
+
+  final CrossFileTestOverrides _overrides;
+
+  bool get _hasTestOverrides => _overrides != null;
+
+  /// Construct a CrossFile object from its ObjectUrl.
+  ///
+  /// Optionally, this can be initialized with `bytes` and `length`
+  /// so no http requests are performed to retrieve files later.
+  ///
+  /// `name` needs to be passed from the outside, since we only have
+  /// access to it while we create the ObjectUrl.
+  XFile(
+    this.path, {
+    this.mimeType,
+    this.name,
+    int length,
+    Uint8List bytes,
+    DateTime lastModified,
+    @visibleForTesting CrossFileTestOverrides overrides,
+  })  : _data = bytes,
+        _length = length,
+        _overrides = overrides,
+        _lastModified = lastModified,
+        super(path);
+
+  /// Construct an CrossFile from its data
+  XFile.fromData(
+    Uint8List bytes, {
+    this.mimeType,
+    this.name,
+    int length,
+    DateTime lastModified,
+    this.path,
+    @visibleForTesting CrossFileTestOverrides overrides,
+  })  : _data = bytes,
+        _length = length,
+        _overrides = overrides,
+        _lastModified = lastModified,
+        super(path) {
+    if (path == null) {
+      final blob = (mimeType == null) ? Blob([bytes]) : Blob([bytes], mimeType);
+      this.path = Url.createObjectUrl(blob);
+    }
+  }
+
+  @override
+  Future<DateTime> lastModified() async {
+    if (_lastModified != null) {
+      return Future.value(_lastModified);
+    }
+    return null;
+  }
+
+  Future<Uint8List> get _bytes async {
+    if (_data != null) {
+      return Future.value(UnmodifiableUint8ListView(_data));
+    }
+    return http.readBytes(path);
+  }
+
+  @override
+  Future<int> length() async {
+    return _length ?? (await _bytes).length;
+  }
+
+  @override
+  Future<String> readAsString({Encoding encoding = utf8}) async {
+    return encoding.decode(await _bytes);
+  }
+
+  @override
+  Future<Uint8List> readAsBytes() async {
+    return Future.value(await _bytes);
+  }
+
+  @override
+  Stream<Uint8List> openRead([int start, int end]) async* {
+    final bytes = await _bytes;
+    yield bytes.sublist(start ?? 0, end ?? bytes.length);
+  }
+
+  /// Saves the data of this CrossFile at the location indicated by path.
+  /// For the web implementation, the path variable is ignored.
+  void saveTo(String path) async {
+    // Create a DOM container where we can host the anchor.
+    _target = ensureInitialized('__x_file_dom_element');
+
+    // Create an <a> tag with the appropriate download attributes and click it
+    // May be overridden with CrossFileTestOverrides
+    final AnchorElement element =
+        (_hasTestOverrides && _overrides.createAnchorElement != null)
+            ? _overrides.createAnchorElement(this.path, this.name)
+            : createAnchorElement(this.path, this.name);
+
+    // Clear the children in our container so we can add an element to click
+    _target.children.clear();
+    addElementToContainerAndClick(_target, element);
+  }
+}
+
+/// Overrides some functions to allow testing
+@visibleForTesting
+class CrossFileTestOverrides {
+  /// For overriding the creation of the file input element.
+  Element Function(String href, String suggestedName) createAnchorElement;
+
+  /// Default constructor for overrides
+  CrossFileTestOverrides({this.createAnchorElement});
+}

packages/cross_file/lib/src/types/interface.dart

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+// Copyright 2018 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:typed_data';
+import 'package:meta/meta.dart';
+
+import './base.dart';
+
+/// A CrossFile is a cross-platform, simplified File abstraction.
+///
+/// It wraps the bytes of a selected file, and its (platform-dependant) path.
+class XFile extends XFileBase {
+  /// Construct a CrossFile object from its path.
+  ///
+  /// Optionally, this can be initialized with `bytes` and `length`
+  /// so no http requests are performed to retrieve data later.
+  ///
+  /// `name` may be passed from the outside, for those cases where the effective
+  /// `path` of the file doesn't match what the user sees when selecting it
+  /// (like in web)
+  XFile(
+    String path, {
+    String mimeType,
+    String name,
+    int length,
+    Uint8List bytes,
+    DateTime lastModified,
+    @visibleForTesting CrossFileTestOverrides overrides,
+  }) : super(path) {
+    throw UnimplementedError(
+        'CrossFile is not available in your current platform.');
+  }
+
+  /// Construct a CrossFile object from its data
+  XFile.fromData(
+    Uint8List bytes, {
+    String mimeType,
+    String name,
+    int length,
+    DateTime lastModified,
+    String path,
+    @visibleForTesting CrossFileTestOverrides overrides,
+  }) : super(path) {
+    throw UnimplementedError(
+        'CrossFile is not available in your current platform.');
+  }
+}
+
+/// Overrides some functions of CrossFile for testing purposes
+@visibleForTesting
+class CrossFileTestOverrides {
+  /// For overriding the creation of the file input element.
+  dynamic Function(String href, String suggestedName) createAnchorElement;
+
+  /// Default constructor for overrides
+  CrossFileTestOverrides({this.createAnchorElement});
+}