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

gpu/command_buffer/service/program_cache_lru_helper.cc

+// 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.
+
+#include "gpu/command_buffer/service/program_cache_lru_helper.h"
+
+namespace gpu {
+namespace gles2 {
+
+ProgramCacheLruHelper::ProgramCacheLruHelper() {}
+ProgramCacheLruHelper::~ProgramCacheLruHelper() {}
+
+void ProgramCacheLruHelper::Clear() {
+  location_map.clear();
+  queue.clear();
+}
+
+bool ProgramCacheLruHelper::IsEmpty() {
+  return queue.empty();
+}
+
+void ProgramCacheLruHelper::KeyUsed(const std::string& key) {
+  IteratorMap::iterator location_iterator = location_map.find(key);
+  if (location_iterator != location_map.end()) {
+    // already exists, erase it
+    queue.erase(location_iterator->second);
+  }
+  queue.push_front(key);
+  location_map[key] = queue.begin();
+}
+
+const std::string* ProgramCacheLruHelper::PeekKey() {
+  if (queue.empty()) {
+    return NULL;
+  }
+  return &queue.back();
+}
+
+void ProgramCacheLruHelper::PopKey() {
+  if (queue.empty()) {
+    return;
+  }
+  const std::string& last = queue.back();
+  location_map.erase(last);
+  queue.pop_back();
+}
+
+}  // namespace gpu
+}  // namespace gles2