FilePageManager - disk based PageManager.

pkg/analysis_server/lib/src/index/file_page_manager.dart

Index: pkg/analysis_server/lib/src/index/file_page_manager.dart
diff --git a/pkg/analysis_server/lib/src/index/file_page_manager.dart b/pkg/analysis_server/lib/src/index/file_page_manager.dart
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index 0000000000000000000000000000000000000000..55c2c7563f0664fc8470dba76f4b81234860f009
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+++ b/pkg/analysis_server/lib/src/index/file_page_manager.dart
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+// Copyright (c) 2014, 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.
+
+library index.file_page_manager;
+
+import 'dart:io';
+import 'dart:typed_data';
+
+import 'package:analysis_server/src/index/page_node_manager.dart';
+
+
+/**
+ * A [PageManager] that stores pages on disk.
+ */
+class FilePageManager implements PageManager {
+  final int pageSizeInBytes;
+
+  RandomAccessFile _file;
+  File _fileRef;
+  List<int> _freePagesList = new List<int>();
+  Set<int> _freePagesSet = new Set<int>();
+  int _nextPage = 0;
+
+  FilePageManager(this.pageSizeInBytes, String path) {
+    _fileRef = new File(path);
+    _file = _fileRef.openSync(mode: FileMode.WRITE);
+  }
+
+  @override
+  int alloc() {
+    if (_freePagesList.isNotEmpty) {
+      int id = _freePagesList.removeLast();
+      _freePagesSet.remove(id);
+      return id;
+    }
+    int id = _nextPage++;
+    Uint8List page = new Uint8List(pageSizeInBytes);
+    _file.setPositionSync(id * pageSizeInBytes);
+    _file.writeFromSync(page);
+    return id;
+  }
+
+  /**
+   * Closes this [FilePageManager].
+   */
+  void close() {
+    _file.closeSync();
+  }
+
+  /**
+   * Deletes the underlaying file.
+   */
+  void delete() {
+    if (_fileRef.existsSync()) {
+      _fileRef.deleteSync();
+    }
+  }
+
+  @override
+  void free(int id) {
+    if (!_freePagesSet.add(id)) {
+      throw new StateError('Page $id has been already freed.');
+    }
+    _freePagesList.add(id);
+  }
+
+  @override
+  Uint8List read(int id) {
+    Uint8List page = new Uint8List(pageSizeInBytes);
+    _file.setPositionSync(id * pageSizeInBytes);
+    int actual = 0;
+    while (actual != page.length) {
+      actual += _file.readIntoSync(page, actual);
+    }
+    return page;
+  }
+
+  @override
+  void write(int id, Uint8List page) {
+    _file.setPositionSync(id * pageSizeInBytes);
+    _file.writeFromSync(page);
+  }
+}