gpu in-memory program cache implementation with a memory limit + lru eviction.

gpu/command_buffer/service/program_cache_lru_helper.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef GPU_COMMAND_BUFFER_SERVICE_PROGRAM_CACHE_LRU_HELPER_H_
+#define GPU_COMMAND_BUFFER_SERVICE_PROGRAM_CACHE_LRU_HELPER_H_
+
+#include <list>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/hash_tables.h"
+#include "gpu/gpu_export.h"
+
+namespace gpu {
+namespace gles2 {
+
+// LRU helper for the program cache, operates in O(1) time.
+// This class uses a linked list with a hash map.  Both copy their string keys,
+// so be mindful that keys you insert will be stored again twice in memory.
+class GPU_EXPORT ProgramCacheLruHelper {
+ public:
+  ProgramCacheLruHelper();
+  ~ProgramCacheLruHelper();
+
+  // clears the lru queue
+  void Clear();
+  // returns true if the lru queue is empty
+  bool IsEmpty();
+  // inserts or refreshes a key in the queue
+  void KeyUsed(const std::string& key);
+  // Peeks at the next key.  Use IsEmpty() first (if the queue is empty then
+  // null is returned).
+  const std::string* PeekKey();
+  // evicts the next key from the queue.
+  void PopKey();
+
+ private:
+  typedef std::list<std::string> StringList;
+  typedef base::hash_map<std::string,
+                         StringList::iterator> IteratorMap;
+  StringList queue;
+  IteratorMap location_map;
+
+  DISALLOW_COPY_AND_ASSIGN(ProgramCacheLruHelper);
+};
+
+}  // namespace gles2
+}  // namespace gpu
+
+#endif  // GPU_COMMAND_BUFFER_SERVICE_PROGRAM_CACHE_LRU_HELPER_H_