Evict using size in bytes in MemoryCachingByteStore.

pkg/analyzer/lib/src/dart/analysis/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';
 
 /**
  * Store of bytes associated with string keys.
  *
  * Each key must be not longer than 100 characters and consist of only `[a-z]`,
@@ skipping 13 matching lines @@
   List<int> get(String key);
 
   /**
    * Associate the given [bytes] with the [key].
    */
   void put(String key, List<int> bytes);
 }
 
 /**
  * A wrapper around [ByteStore] which adds an in-memory LRU cache to it.
- *
- * TODO(scheglov) Consider implementing size and/or time eviction policies.
  */
 class MemoryCachingByteStore implements ByteStore {
-  final ByteStore store;
-  final int maxEntries;
+  final ByteStore _store;
+  final int _maxSizeBytes;
 
-  final _map = <String, List<int>>{};
-  final _keys = new LinkedHashSet<String>();
+  final HashMap<String, List<int>> _map = new HashMap<String, List<int>>();

[Paul Berry, 2016/11/09 20:17:36]

Why change this to a HashMap?  Don't we lose the "least recently used" behavior
we want?

[scheglov, 2016/11/09 20:21:33]

Ouch.
Thanks.
That's a mistake.
Fixed.

[Paul Berry, 2016/11/09 20:22:15]

Ok, with that fixed, lgtm.

+  int _currentSizeBytes = 0;
 
-  MemoryCachingByteStore(this.store, this.maxEntries);
+  MemoryCachingByteStore(this._store, this._maxSizeBytes);
 
   @override
   List<int> get(String key) {
-    _keys.remove(key);
-    _keys.add(key);
-    _evict();
-    return _map.putIfAbsent(key, () => store.get(key));
+    List<int> bytes = _map[key];
+    if (bytes == null) {
+      bytes = _store.get(key);
+      _map[key] = bytes;
+      _currentSizeBytes += bytes?.length ?? 0;
+      _evict();
+    }
+    return bytes;
   }
 
   @override
   void put(String key, List<int> bytes) {
-    store.put(key, bytes);
+    _store.put(key, bytes);
+    _currentSizeBytes -= _map[key]?.length ?? 0;
     _map[key] = bytes;
-    _keys.add(key);
+    _currentSizeBytes += bytes.length;
     _evict();
   }
 
   void _evict() {
-    if (_keys.length > maxEntries) {
-      String key = _keys.first;
-      _keys.remove(key);
-      _map.remove(key);
+    while (_currentSizeBytes > _maxSizeBytes) {
+      if (_map.isEmpty) {
+        break;
+      }
+      String key = _map.keys.first;
+      List<int> bytes = _map.remove(key);
+      _currentSizeBytes -= bytes.length;
     }
   }
 }