Evict from FileByteStore by the total cache size in bytes.

pkg/analyzer/lib/src/dart/analysis/file_byte_store.dart

 // Copyright (c) 2015, 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.
 
+import 'dart:collection';
+
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/dart/analysis/byte_store.dart';
 
 /**
  * [ByteStore] that stores values as [File]s.
- *
- * TODO(scheglov) Add some eviction policies.
  */
 class FileByteStore implements ByteStore {
-  final Folder folder;
+  final Folder _folder;
+  final String _tempName;
+  final int _maxSizeBytes;
 
-  FileByteStore(this.folder);
+  final LinkedHashMap<File, int> _files = new LinkedHashMap<File, int>();
+  int _currentSizeBytes = 0;
+
+  FileByteStore(this._folder, this._tempName, this._maxSizeBytes) {
+    for (Resource file in _folder.getChildren()) {
+      if (file is File) {
+        int length = file.lengthSync;
+        _files[file] = length;
+        _currentSizeBytes += length;
+      }
+    }
+  }
 
   @override
   List<int> get(String key) {
     try {
-      File file = folder.getChildAssumingFile(key);
-      return file.readAsBytesSync();
+      File file = _folder.getChildAssumingFile(key);
+      List<int> bytes = file.readAsBytesSync();
+      // Update the file position.
+      _files.remove(file);
+      _files[file] = bytes.length;
+      return bytes;
     } catch (_) {
       return null;
     }
   }
 
   @override
   void put(String key, List<int> bytes) {
     try {
-      File file = folder.getChildAssumingFile(key);
-      file.writeAsBytesSync(bytes);
+      File tempFile = _folder.getChildAssumingFile(_tempName);
+      tempFile.writeAsBytesSync(bytes);
+      File file = _folder.getChildAssumingFile(key);
+      tempFile.renameSync(file.path);
+      // Update the size.
+      _currentSizeBytes -= _files[key] ?? 0;
+      _files[file] = bytes.length;
+      _currentSizeBytes += bytes.length;
+      _evict();
     } catch (_) {}
   }
+
+  void _evict() {
+    while (_currentSizeBytes > _maxSizeBytes) {
+      if (_files.isEmpty) {
+        break;
+      }
+      File file = _files.keys.first;
+      // Update the size.
+      int size = _files.remove(file);
+      _currentSizeBytes -= size;
+      // Delete the file.
+      try {
+        file.delete();

[Brian Wilkerson, 2016/11/10 22:12:04]

Do we want to decrease the size if we can't actually delete the file?

+      } on FileSystemException {}
+    }
+  }
 }