Update source file structure

Author: mgenware

lib/random_access_source.dart

@@ -1,5 +1,7 @@
 /// Shared interfaces for random access data.
 library;
 
-export 'src/random_access_source_base.dart';
+export 'src/random_access_source.dart';
+export 'src/bytes_ra_source.dart';
+export 'src/random_access_file_ra_source.dart';
 export 'src/random_access_binary_reader.dart';

lib/src/bytes_ra_source.dart

@@ -0,0 +1,54 @@
+import 'dart:typed_data';
+
+import '../random_access_source.dart';
+
+class BytesRASource extends RandomAccessSource {
+  final Uint8List _bytes;
+  int _position = 0;
+
+  BytesRASource(this._bytes);
+
+  @override
+  Future<int> length() async {
+    return _bytes.length;
+  }
+
+  @override
+  Future<int> readByte() async {
+    if (_position >= _bytes.length) {
+      return -1;
+    }
+    return _bytes[_position++];
+  }
+
+  @override
+  Future<Uint8List> read(int length) async {
+    if (_position >= _bytes.length) {
+      return Uint8List(0);
+    }
+    final end = (_position + length).clamp(0, _bytes.length);
+    final result = Uint8List.sublistView(_bytes, _position, end);
+    _position = end;
+    return result;
+  }
+
+  @override
+  Future<int> position() async {
+    return _position;
+  }
+
+  @override
+  Future<void> setPosition(int position) async {
+    _position = position;
+  }
+
+  @override
+  Future<Uint8List> readToEnd() async {
+    final result = Uint8List.sublistView(_bytes, _position);
+    _position = _bytes.length;
+    return result;
+  }
+
+  @override
+  Future<void> close() async {}
+}

lib/src/random_access_file_ra_source.dart

@@ -0,0 +1,50 @@
+import 'dart:io';
+import 'dart:typed_data';
+
+import '../random_access_source.dart';
+
+class RandomAccessFileRASource extends RandomAccessSource {
+  final RandomAccessFile _file;
+
+  RandomAccessFileRASource(this._file);
+
+  static Future<RandomAccessFileRASource> open(String path) async {
+    final file = await File(path).open();
+    return RandomAccessFileRASource(file);
+  }
+
+  @override
+  Future<int> length() async {
+    return _file.length();
+  }
+
+  @override
+  Future<int> readByte() async {
+    return _file.readByte();
+  }
+
+  @override
+  Future<Uint8List> read(int length) async {
+    return _file.read(length);
+  }
+
+  @override
+  Future<int> position() async {
+    return _file.position();
+  }
+
+  @override
+  Future<void> setPosition(int position) async {
+    await _file.setPosition(position);
+  }
+
+  @override
+  Future<Uint8List> readToEnd() async {
+    return _file.read(await _file.length());
+  }
+
+  @override
+  Future<void> close() async {
+    await _file.close();
+  }
+}

lib/src/random_access_source.dart

@@ -0,0 +1,25 @@
+import 'dart:typed_data';
+
+/// Base class for random access sources.
+abstract class RandomAccessSource {
+  /// Gets the length of the source.
+  Future<int> length();
+
+  /// Reads a byte from the source.
+  Future<int> readByte();
+
+  /// Reads an array of bytes from the source.
+  Future<Uint8List> read(int length);
+
+  /// Gets the current position in the source.
+  Future<int> position();
+
+  /// Sets the current position in the source.
+  Future<void> setPosition(int position);
+
+  /// Reads all the remaining bytes from the source.
+  Future<Uint8List> readToEnd();
+
+  /// Closes the source.
+  Future<void> close();
+}