Add readInto

Author: mgenware

lib/src/bytes_ra_source.dart

@@ -21,6 +21,10 @@ class BytesRASource extends RandomAccessSource {
   @override
   Future<Uint8List> read(int count) async => _syncSource.read(count);
 
+  @override
+  Future<int> readInto(List<int> buffer, int offset, int count) async =>
+      _syncSource.readInto(buffer, offset, count);
+
   @override
   Future<int> position() async => _syncSource.position();
 
@@ -61,6 +65,17 @@ class SyncBytesRASource {
     return result;
   }
 
+  int readInto(List<int> buffer, int offset, int count) {
+    if (_position >= _bytes.length) {
+      return 0;
+    }
+    final end = (_position + count).clamp(0, _bytes.length);
+    final bytesToRead = end - _position;
+    buffer.setRange(offset, offset + bytesToRead, _bytes, _position);
+    _position = end;
+    return bytesToRead;
+  }
+
   int position() {
     return _position;
   }

lib/src/file_ra_source_vm.dart

@@ -25,6 +25,10 @@ class FileRASource extends base.FileRASource {
   @override
   Future<Uint8List> read(int count) => _file.read(count);
 
+  @override
+  Future<int> readInto(List<int> buffer, int offset, int count) =>
+      _file.readInto(buffer, offset, offset + count);
+
   @override
   Future<int> position() => _file.position();
 

lib/src/file_ra_source_web.dart

@@ -36,6 +36,10 @@ class FileRASource extends base.FileRASource {
   @override
   Future<Uint8List> read(int count) => _bytes.read(count);
 
+  @override
+  Future<int> readInto(List<int> buffer, int offset, int count) =>
+      _bytes.readInto(buffer, offset, count);
+
   @override
   Future<int> position() => _bytes.position();
 

lib/src/random_access_source.dart

@@ -11,6 +11,9 @@ abstract class RandomAccessSource {
   /// Reads an array of bytes from the source.
   Future<Uint8List> read(int count);
 
+  /// Reads bytes into the provided buffer.
+  Future<int> readInto(List<int> buffer, int offset, int count);
+
   /// Gets the current position in the source.
   Future<int> position();
 

test/bytes_sync_test.dart

@@ -49,6 +49,30 @@ void main() {
     expect(src.position(), 5);
   });
 
+  test('ReadInto', () async {
+    final src = _bytesSource();
+    final buffer = Uint8List(4);
+
+    var bytesRead = src.readInto(buffer, 0, 2);
+    expect(bytesRead, 2);
+    expect(buffer.sublist(0, 2), Uint8List.fromList([1, 2]));
+    expect(src.position(), 2);
+
+    bytesRead = src.readInto(buffer, 2, 2);
+    expect(bytesRead, 2);
+    expect(buffer.sublist(2, 4), Uint8List.fromList([3, 4]));
+    expect(src.position(), 4);
+
+    bytesRead = src.readInto(buffer, 0, 4);
+    expect(bytesRead, 1);
+    expect(buffer.sublist(0, 1), Uint8List.fromList([5]));
+    expect(src.position(), 5);
+
+    bytesRead = src.readInto(buffer, 0, 4);
+    expect(bytesRead, 0);
+    expect(src.position(), 5);
+  });
+
   test('Position', () async {
     final src = _bytesSource();
     expect(src.position(), 0);

test/bytes_test.dart

@@ -52,6 +52,31 @@ void main() {
     await src.close();
   });
 
+  test('ReadInto', () async {
+    final src = await _bytesSource();
+    final buffer = Uint8List(4);
+
+    var bytesRead = await src.readInto(buffer, 0, 2);
+    expect(bytesRead, 2);
+    expect(buffer.sublist(0, 2), Uint8List.fromList([1, 2]));
+    expect(await src.position(), 2);
+
+    bytesRead = await src.readInto(buffer, 2, 2);
+    expect(bytesRead, 2);
+    expect(buffer.sublist(2, 4), Uint8List.fromList([3, 4]));
+    expect(await src.position(), 4);
+
+    bytesRead = await src.readInto(buffer, 0, 4);
+    expect(bytesRead, 1);
+    expect(buffer.sublist(0, 1), Uint8List.fromList([5]));
+    expect(await src.position(), 5);
+
+    bytesRead = await src.readInto(buffer, 0, 4);
+    expect(bytesRead, 0);
+    expect(await src.position(), 5);
+    await src.close();
+  });
+
   test('Position', () async {
     final src = await _bytesSource();
     expect(await src.position(), 0);

test/raf_test.dart

@@ -1,3 +1,5 @@
+import 'dart:typed_data';
+
 import 'package:test/test.dart';
 
 import 'assets/flutter_icon_96x96.dart';
@@ -43,6 +45,23 @@ void main() {
     await src.close();
   });
 
+  test('ReadInto', () async {
+    final src = await rafSource();
+    final buffer = Uint8List(4);
+
+    var bytesRead = await src.readInto(buffer, 0, 2);
+    expect(bytesRead, 2);
+    expect(buffer.sublist(0, 2), flutterIcon.sublist(0, 2));
+    expect(await src.position(), 2);
+
+    bytesRead = await src.readInto(buffer, 2, 2);
+    expect(bytesRead, 2);
+    expect(buffer.sublist(2, 4), flutterIcon.sublist(2, 4));
+    expect(await src.position(), 4);
+
+    await src.close();
+  });
+
   test('Position', () async {
     final src = await rafSource();
     expect(await src.position(), 0);