Improving and adding an in-memory MRU cache to DiskBasedCertCache.

net/http/disk_based_cert_cache.h

 // Copyright (c) 2014 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 NET_HTTP_DISK_BASED_CERT_CACHE_H
 #define NET_HTTP_DISK_BASED_CERT_CACHE_H
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/containers/hash_tables.h"
+#include "base/containers/mru_cache.h"
 #include "base/memory/weak_ptr.h"
 #include "net/base/net_export.h"
 #include "net/cert/x509_certificate.h"
 
 namespace disk_cache {
 class Backend;
 }  // namespace disk_cache
 
 namespace net {
 
@@ skipping 17 matching lines @@
   // a reference to the certificate need to use X509Certificate::DupOSCertHandle
   // inside |cb|.
   void Get(const std::string& key, const GetCallback& cb);
 
   // Stores |cert_handle| in the cache. If |cert_handle| is successfully stored,
   // |cb| will be called with the key. If |cb| is called with an empty
   // string, then |cert_handle| was not stored.
   void Set(const X509Certificate::OSCertHandle cert_handle,
            const SetCallback& cb);
 
+  // Returns the number of in-memory MRU cache hits that have occured
+  // on Set and Get operations. Intended for test purposes only.
+  size_t mem_cache_hits_for_testing() const { return mem_cache_hits_; }
+
+  // Returns the number of in-memory MRU cache misses that have occured
+  // on Set and Get operations. Intended for test purposes only.
+  size_t mem_cache_misses_for_testing() const { return mem_cache_misses_; }
+
  private:
   class ReadWorker;
   class WriteWorker;
 
+  // A functor used to free an OSCertHandle. Used by the MRUCertCache.
+  struct CertFree {
+    void operator()(X509Certificate::OSCertHandle cert_handle);
+  };
+
+  // An in-memory cache that is used to prevent redundant reads and writes
+  // to and from the disk cache.
+  typedef base::MRUCacheBase<std::string,
+                             X509Certificate::OSCertHandle,
+                             CertFree> MRUCertCache;
+
   // ReadWorkerMap and WriteWorkerMap map cache keys to their
   // corresponding Workers.
   typedef base::hash_map<std::string, ReadWorker*> ReadWorkerMap;
   typedef base::hash_map<std::string, WriteWorker*> WriteWorkerMap;
 
   // FinishedReadOperation and FinishedWriteOperation are used by callbacks
   // given to the workers to signal the DiskBasedCertCache they have completed
   // their work.
-  void FinishedReadOperation(const std::string& key);
-  void FinishedWriteOperation(const std::string& key);
+  void FinishedReadOperation(const std::string& key,
+                             X509Certificate::OSCertHandle cert_handle);
+  void FinishedWriteOperation(const std::string& key,
+                              X509Certificate::OSCertHandle cert_handle);
+
+  disk_cache::Backend* backend_;
 
   ReadWorkerMap read_worker_map_;
   WriteWorkerMap write_worker_map_;
+  MRUCertCache mru_cert_cache_;
 
-  disk_cache::Backend* backend_;
+  int mem_cache_hits_;
+  int mem_cache_misses_;
+
   base::WeakPtrFactory<DiskBasedCertCache> weak_factory_;
   DISALLOW_COPY_AND_ASSIGN(DiskBasedCertCache);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_DISK_BASED_CERT_CACHE_H