Remove dependency on `package:charcode`. (#43)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3c942aa..2bb3d55 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 4.0.1
+
+* Remove dependency on `package:charcode`.
+
 ## 4.0.0
 
 * Stable null safety stable release.

diff --git a/lib/src/chunked_coding/charcodes.dart b/lib/src/chunked_coding/charcodes.dart
new file mode 100644
index 0000000..a7a8519
--- /dev/null
+++ b/lib/src/chunked_coding/charcodes.dart

@@ -0,0 +1,21 @@
+// Copyright (c) 2021, 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.
+
+/// "Line feed" control character.
+const int $lf = 0x0a;
+
+/// "Carriage return" control character.
+const int $cr = 0x0d;
+
+/// Character `0`.
+const int $0 = 0x30;
+
+/// Character `9`.
+const int $9 = 0x39;
+
+/// Character `a`.
+const int $a = 0x61;
+
+/// Character `f`.
+const int $f = 0x66;

diff --git a/lib/src/chunked_coding/decoder.dart b/lib/src/chunked_coding/decoder.dart
index a916870..ac22c1b 100644
--- a/lib/src/chunked_coding/decoder.dart
+++ b/lib/src/chunked_coding/decoder.dart

@@ -7,9 +7,10 @@
 import 'dart:math' as math;
 import 'dart:typed_data';
 
-import 'package:charcode/ascii.dart';
 import 'package:typed_data/typed_data.dart';
 
+import 'charcodes.dart';
+
 /// The canonical instance of [ChunkedCodingDecoder].
 const chunkedCodingDecoder = ChunkedCodingDecoder._();
 

diff --git a/lib/src/chunked_coding/encoder.dart b/lib/src/chunked_coding/encoder.dart
index 81e4dc8..deb4906 100644
--- a/lib/src/chunked_coding/encoder.dart
+++ b/lib/src/chunked_coding/encoder.dart

@@ -5,7 +5,7 @@
 import 'dart:convert';
 import 'dart:typed_data';
 
-import 'package:charcode/ascii.dart';
+import 'charcodes.dart';
 
 /// The canonical instance of [ChunkedCodingEncoder].
 const chunkedCodingEncoder = ChunkedCodingEncoder._();

diff --git a/pubspec.yaml b/pubspec.yaml
index b2939aa..2ca441b 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml

@@ -1,5 +1,5 @@
 name: http_parser
-version: 4.0.0
+version: 4.0.1
 description: >-
   A platform-independent package for parsing and serializing HTTP formats.
 homepage: https://github.com/dart-lang/http_parser
@@ -8,12 +8,12 @@
   sdk: '>=2.12.0-0 <3.0.0'
 
 dependencies:
-  charcode: ^1.2.0
   collection: ^1.15.0
   source_span: ^1.8.0
   string_scanner: ^1.1.0
   typed_data: ^1.3.0
 
 dev_dependencies:
+  charcode: ^1.2.0
   pedantic: ^1.10.0
   test: ^1.16.0-nullsafety.4