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

net/http/disk_based_cert_cache.h

Index: net/http/disk_based_cert_cache.h
diff --git a/net/http/disk_based_cert_cache.h b/net/http/disk_based_cert_cache.h
index 302ac5cf7fe7a8d7aa259a4d36aac1b7ced5abd2..6868cdbc4f87f371b262de48648bd0f7a6adcde2 100644
--- a/net/http/disk_based_cert_cache.h
+++ b/net/http/disk_based_cert_cache.h
@@ -9,6 +9,7 @@
 
 #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"
@@ -50,6 +51,34 @@ class NET_EXPORT_PRIVATE DiskBasedCertCache {
   class ReadWorker;
   class WriteWorker;
 
+  // A functor used to free an OSCertHandle. Used by the MRUCertCache.
+  class CertFree {
+   public:
+    void operator()(X509Certificate::OSCertHandle cert_handle) {
+      X509Certificate::FreeOSCertHandle(cert_handle);
+    }
+  };
+
+  // An in-memory cache that is used to prevent redundant reads and writes
+  // to and from the disk cache.
+  class MRUCertCache : public base::MRUCacheBase<std::string,

[wtc, 2014/07/01 02:11:31]

Since MRUCertCache doesn't have any new method or constructor, I think it can be
just a typedef:

  typedef base::MRUCacheBase<std::string,
                             X509Certificate::OSCertHandle,
                             CertFree> MRUCertCache;

Does this work?

+                                                 X509Certificate::OSCertHandle,
+                                                 CertFree> {
+   private:
+    typedef base::MRUCacheBase<std::string,
+                               X509Certificate::OSCertHandle,
+                               CertFree> ParentType;
+
+   public:
+    // |max_size| is the maximum number of OSCertHandles to be stored
+    // at one time.
+    explicit MRUCertCache(typename ParentType::size_type max_size)
+        : ParentType(max_size) {}
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(MRUCertCache);
+  };
+
   // ReadWorkerMap and WriteWorkerMap map cache keys to their
   // corresponding Workers.
   typedef base::hash_map<std::string, ReadWorker*> ReadWorkerMap;
@@ -57,14 +86,18 @@ class NET_EXPORT_PRIVATE DiskBasedCertCache {
 
   // 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);
+  // their work. FinishedReadOperation also stores the retrieved OSCertHandle
+  // in |mru_cert_cache_|.
+  void FinishedReadOperation(const std::string& key,
+                             X509Certificate::OSCertHandle cert_handle);
   void FinishedWriteOperation(const std::string& key);
 
+  disk_cache::Backend* backend_;
+
   ReadWorkerMap read_worker_map_;
   WriteWorkerMap write_worker_map_;
+  MRUCertCache mru_cert_cache_;
 
-  disk_cache::Backend* backend_;
   base::WeakPtrFactory<DiskBasedCertCache> weak_factory_;
   DISALLOW_COPY_AND_ASSIGN(DiskBasedCertCache);
 };