Review fixes

lib/src/codepage.dart

@@ -277,19 +277,25 @@ CodePageDecoder _createDecoder(String characters) {
   return _NonBmpCodePageDecoder._(result);
 }
 
-/// An input Sink for decoders where each input byte can be be considered
-/// independantly.
-class _CodePageSink implements Sink<List<int>> {
+/// An input [ByteConversionSink] for decoders where each input byte can be be
+/// considered independantly.
+class _CodePageDecoderSink implements ByteConversionSink {
   final Sink<String> _output;
   final String Function(List<int> input) _convert;
 
-  _CodePageSink(this._output, this._convert);
+  _CodePageDecoderSink(this._output, this._convert);
 
   @override
   void add(List<int> chunk) {
     _output.add(_convert(chunk));
   }
 
+  @override
+  void addSlice(List<int> chunk, int start, int end, bool isLast) {
+    add(chunk.sublist(start, end));
+    if (isLast) close();
+  }
+
   @override
   void close() {
     _output.close();
@@ -348,7 +354,7 @@ class _NonBmpCodePageDecoder extends Converter<List<int>, String>
 
   @override
   Sink<List<int>> startChunkedConversion(Sink<String> sink) =>
-      _CodePageSink(sink, convert);
+      _CodePageDecoderSink(sink, convert);
 }
 
 class _BmpCodePageDecoder extends Converter<List<int>, String>
@@ -385,7 +391,7 @@ class _BmpCodePageDecoder extends Converter<List<int>, String>
 
   @override
   Sink<List<int>> startChunkedConversion(Sink<String> sink) =>
-      _CodePageSink(sink, convert);
+      _CodePageDecoderSink(sink, convert);
 
   String _convertAllowInvalid(List<int> bytes) {
     var count = bytes.length;

test/codepage_test.dart

@@ -127,13 +127,30 @@ void main() {
       final outputSink = StringConversionSink.withCallback(
           (accumulated) => decodedString = accumulated);
       final inputSink = cp.decoder.startChunkedConversion(outputSink);
+
       inputSink
         ..add([1])
         ..add([0])
-        ..add([3]);
-
-      inputSink.close();
+        ..add([3])
+        ..close();
       expect(decodedString, 'BAD');
     });
+
+    test('chunked conversion - byte conversion sink', () {
+      late final String decodedString;
+      final outputSink = StringConversionSink.withCallback(
+          (accumulated) => decodedString = accumulated);
+      final bytes = [1, 0, 3, 2, 0, 5, 4];
+
+      final inputSink = cp.decoder.startChunkedConversion(outputSink);
+      expect(inputSink, isA<ByteConversionSink>());
+
+      (inputSink as ByteConversionSink)
+        ..addSlice(bytes, 1, 3, false)
+        ..addSlice(bytes, 4, 5, false)
+        ..addSlice(bytes, 6, 6, true);
+
+      expect(decodedString, 'ADA');
+    });
   });
 }