pkg/shelf

pkg/shelf/lib/src/message.dart

+// Copyright (c) 2014, 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 shelf.message;
+
+import 'dart:async';
+import 'dart:convert';
+
+import 'package:collection/wrappers.dart';
+import 'package:stack_trace/stack_trace.dart';
+
+import 'media_type.dart';
+
+/// Represents logic shared between [Request] and [Response].
+abstract class Message {
+  /// The HTTP headers.
+  ///
+  /// The value is immutable.
+  final Map<String, String> headers;
+
+  /// The streaming body of the message.
+  ///
+  /// This can be read via [read] or [readAsString].
+  final Stream<List<int>> _body;
+
+  Message(UnmodifiableMapView<String, String> headers, this._body)
+      : this.headers = headers;
+
+  /// The contents of the content-length field in [headers].
+  ///
+  /// If not set, `null`.
+  int get contentLength {
+    if (_contentLengthCache != null) return _contentLengthCache;
+    if (!headers.containsKey('content-length')) return null;
+    _contentLengthCache = int.parse(headers['content-length']);
+    return _contentLengthCache;
+  }
+  int _contentLengthCache;
+
+  /// The MIME type of the message.
+  ///
+  /// This is parsed from the Content-Type header in [headers]. It contains only
+  /// the MIME type, without any Content-Type parameters.
+  ///
+  /// If [headers] doesn't have a Content-Type header, this will be `null`.
+  String get mimeType {
+    var contentType = _contentType;
+    if (contentType == null) return null;
+    return contentType.mimeType;
+  }
+
+  /// The encoding of the message body.
+  ///
+  /// This is parsed from the "charset" paramater of the Content-Type header in
+  /// [headers].
+  ///
+  /// If [headers] doesn't have a Content-Type header or it specifies an
+  /// encoding that [dart:convert] doesn't support, this will be `null`.
+  Encoding get encoding {
+    var contentType = _contentType;
+    if (contentType == null) return null;
+    if (!contentType.parameters.containsKey('charset')) return null;
+    return Encoding.getByName(contentType.parameters['charset']);
+  }
+
+  /// The parsed version of the Content-Type header in [headers].
+  ///
+  /// This is cached for efficient access.
+  MediaType get _contentType {
+    if (_contentTypeCache != null) return _contentTypeCache;
+    if (!headers.containsKey('content-type')) return null;
+    _contentTypeCache = new MediaType.parse(headers['content-type']);
+    return _contentTypeCache;
+  }
+  MediaType _contentTypeCache;
+
+  /// Returns a [Stream] representing the body.
+  ///
+  /// Can only be called once.
+  Stream<List<int>> read() => _body;
+
+  /// Returns a [Future] containing the body as a String.
+  ///
+  /// If [encoding] is passed, that's used to decode the body.
+  /// Otherwise the encoding is taken from the Content-Type header. If that
+  /// doesn't exist or doesn't have a "charset" parameter, UTF-8 is used.
+  ///
+  /// This calls [read] internally, which can only be called once.
+  Future<String> readAsString([Encoding encoding]) {
+    if (encoding == null) encoding = this.encoding;
+    if (encoding == null) encoding = UTF8;
+    return Chain.track(encoding.decodeStream(read()));
+  }
+}