Add content type library (#124)

Author: donny-dont

lib/src/content_type.dart

@@ -0,0 +1,25 @@
+// Copyright (c) 2017, 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.
+
+import 'dart:convert';
+
+import 'package:http_parser/http_parser.dart';
+
+/// Returns the [Encoding] that corresponds to [charset].
+///
+/// Returns `null` if [charset] is `null` or if no [Encoding] was found that
+/// corresponds to [charset].
+Encoding encodingForCharset(String charset) {
+  if (charset == null) return null;
+  return Encoding.getByName(charset);
+}
+
+/// Determines the encoding from the media [type].
+///
+/// Returns `null` if the charset is not specified in the [type] or if no
+/// [Encoding] was found that corresponds to the `charset`.
+Encoding encodingForMediaType(MediaType type) {
+  if (type == null) return null;
+  return encodingForCharset(type.parameters['charset']);
+}

lib/src/message.dart

@@ -9,6 +9,7 @@ import 'package:collection/collection.dart';
 import 'package:http_parser/http_parser.dart';
 
 import 'body.dart';
+import 'content_type.dart';
 import 'http_unmodifiable_map.dart';
 import 'utils.dart';
 
@@ -80,10 +81,12 @@ abstract class Message {
   /// 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']);
+    var contentLengthHeader = getHeader(headers, 'content-length');
+    if (contentLengthHeader == null) return null;
+    _contentLengthCache = int.parse(contentLengthHeader);
     return _contentLengthCache;
   }
+
   int _contentLengthCache;
 
   /// The MIME type declared in [headers].
@@ -92,11 +95,7 @@ abstract class Message {
   /// 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;
-  }
+  String get mimeType => _contentType?.mimeType;
 
   /// The encoding of the body returned by [read].
   ///
@@ -105,22 +104,19 @@ abstract class Message {
   ///
   /// 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']);
-  }
+  Encoding get encoding => encodingForMediaType(_contentType);
 
   /// 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']);
+    var contentLengthHeader = getHeader(headers, 'content-type');
+    if (contentLengthHeader == null) return null;
+    _contentTypeCache = new MediaType.parse(contentLengthHeader);
     return _contentTypeCache;
   }
+
   MediaType _contentTypeCache;
 
   /// Returns the message body as byte chunks.

lib/src/utils.dart

@@ -52,24 +52,6 @@ List<String> split1(String toSplit, String pattern) {
   ];
 }
 
-/// Returns the [Encoding] that corresponds to [charset]. Returns [fallback] if
-/// [charset] is null or if no [Encoding] was found that corresponds to
-/// [charset].
-Encoding encodingForCharset(String charset, [Encoding fallback = LATIN1]) {
-  if (charset == null) return fallback;
-  var encoding = Encoding.getByName(charset);
-  return encoding == null ? fallback : encoding;
-}
-
-
-/// Returns the [Encoding] that corresponds to [charset]. Throws a
-/// [FormatException] if no [Encoding] was found that corresponds to [charset].
-/// [charset] may not be null.
-Encoding requiredEncodingForCharset(String charset) {
-  var encoding = Encoding.getByName(charset);
-  if (encoding != null) return encoding;
-  throw new FormatException('Unsupported encoding "$charset".');
-}
 
 /// A regular expression that matches strings that are composed entirely of
 /// ASCII-compatible characters.