pkg/front_end/lib/memory_file_system.dart

// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

library front_end.memory_file_system;

import 'dart:async';
import 'dart:convert';
import 'dart:typed_data';

import 'package:path/path.dart' as p;

import 'file_system.dart';

/// Concrete implementation of [FileSystem] which performs its operations on an
/// in-memory virtual file system.
///
/// Not intended to be implemented or extended by clients.
class MemoryFileSystem implements FileSystem {
  @override
  final p.Context context;

  final Map<String, Uint8List> _files = {};

  /// The "current directory" in the in-memory virtual file system.
  ///
  /// This is used to convert relative paths to absolute paths.
  String currentDirectory;

  MemoryFileSystem(this.context, this.currentDirectory);

  @override
  MemoryFileSystemEntity entityForPath(String path) =>
      new MemoryFileSystemEntity._(
          this, context.normalize(context.join(currentDirectory, path)));

  @override
  MemoryFileSystemEntity entityForUri(Uri uri) {
    if (uri.scheme != 'file') throw new ArgumentError('File URI expected');
    // Note: we don't have to verify that the URI's path is absolute, because
    // URIs with non-empty schemes always have absolute paths.
    return entityForPath(context.fromUri(uri));
  }
}

/// Concrete implementation of [FileSystemEntity] for use by
/// [MemoryFileSystem].
class MemoryFileSystemEntity implements FileSystemEntity {
  final MemoryFileSystem _fileSystem;

  @override
  final String path;

  MemoryFileSystemEntity._(this._fileSystem, this.path);

  @override
  int get hashCode => path.hashCode;

  @override
  bool operator ==(Object other) =>
      other is MemoryFileSystemEntity &&
      other.path == path &&
      identical(other._fileSystem, _fileSystem);

  @override
  Future<List<int>> readAsBytes() async {
    List<int> contents = _fileSystem._files[path];
    if (contents != null) {
      return contents.toList();
    }
    throw new Exception('File does not exist');
  }

  @override
  Future<String> readAsString() async {
    List<int> contents = await readAsBytes();
    return UTF8.decode(contents);
  }

  /// Writes the given raw bytes to this file system entity.
  ///
  /// If no file exists, one is created.  If a file exists already, it is
  /// overwritten.
  void writeAsBytesSync(List<int> bytes) {
    _fileSystem._files[path] = new Uint8List.fromList(bytes);
  }

  /// Writes the given string to this file system entity.
  ///
  /// The string is encoded as UTF-8.
  ///
  /// If no file exists, one is created.  If a file exists already, it is
  /// overwritten.
  void writeAsStringSync(String s) {
    // Note: the return type of UTF8.encode is List<int>, but in practice it
    // always returns Uint8List.  We rely on that for efficiency, so that we
    // don't have to make an extra copy.
    _fileSystem._files[path] = UTF8.encode(s) as Uint8List;
  }
}