[ServiceWorkerCache] Reland backend state CL

content/browser/service_worker/service_worker_cache.h

 // Copyright 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 CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_CACHE_H_
 #define CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_CACHE_H_
 
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
@@ skipping 68 matching lines @@
 
   // Returns ErrorNotFound if not found. Otherwise deletes and returns
   // ErrorTypeOK.
   void Delete(scoped_ptr<ServiceWorkerFetchRequest> request,
               const ErrorCallback& callback);
 
   // TODO(jkarlin): Have keys take an optional ServiceWorkerFetchRequest.
   // Returns ErrorTypeOK and a vector of requests if there are no errors.
   void Keys(const RequestsCallback& callback);
 
-  // Prevents further operations from starting on this object, waits for
-  // existing operations to finish, and then deletes the backend.  Close should
-  // only be called once per ServiceWorkerCache.
+  // Closes the backend. Pending and future operations that require the backend
+  // will exit early. Close should only be called once per ServiceWorkerCache.
   void Close(const base::Closure& callback);
 
   // The size of the cache contents in memory. Returns 0 if the cache backend is
   // not a memory cache backend.
   int64 MemoryBackedSize() const;
 
   void set_backend(scoped_ptr<disk_cache::Backend> backend) {
     backend_ = backend.Pass();
   }
 
   base::WeakPtr<ServiceWorkerCache> AsWeakPtr();
 
  private:
   friend class base::RefCounted<ServiceWorkerCache>;
   friend class TestServiceWorkerCache;
 
   class BlobReader;
   struct KeysContext;
   struct PutContext;
+
+  // The backend progresses from uninitialized, to open, to closed, and cannot
+  // reverse direction.  The open step may be skipped.
+  enum BackendState {
+    BACKEND_UNINITIALIZED,  // No backend, create backend on first operation.
+    BACKEND_OPEN,           // Backend can be used.
+    BACKEND_CLOSED          // Backend cannot be used.  All ops should fail.
+  };
+
   typedef std::vector<disk_cache::Entry*> Entries;
 
   ServiceWorkerCache(
       const GURL& origin,
       const base::FilePath& path,
       net::URLRequestContext* request_context,
       const scoped_refptr<storage::QuotaManagerProxy>& quota_manager_proxy,
       base::WeakPtr<storage::BlobStorageContext> blob_context);
 
   // Operations in progress will complete after the cache is deleted but pending
@@ skipping 16 matching lines @@
   // Static callbacks for the Keys function.
   static void KeysDidOpenNextEntry(scoped_ptr<KeysContext> keys_context,
                                    int rv);
   static void KeysProcessNextEntry(scoped_ptr<KeysContext> keys_context,
                                    const Entries::iterator& iter);
   static void KeysDidReadMetadata(
       scoped_ptr<KeysContext> keys_context,
       const Entries::iterator& iter,
       scoped_ptr<ServiceWorkerCacheMetadata> metadata);
 
+  void CloseImpl(const base::Closure& callback);
+
   // Loads the backend and calls the callback with the result (true for
   // success). The callback will always be called. Virtual for tests.
   virtual void CreateBackend(const ErrorCallback& callback);
 
-  void Init(const base::Closure& callback);
+  void InitBackend(const base::Closure& callback);
   void InitDone(ErrorType error);
 
   void IncPendingOps() { pending_ops_++; }
   void DecPendingOps();
   void PendingErrorCallback(const ErrorCallback& callback, ErrorType error);
   void PendingResponseCallback(
       const ResponseCallback& callback,
       ErrorType error,
       scoped_ptr<ServiceWorkerResponse> response,
       scoped_ptr<storage::BlobDataHandle> blob_data_handle);
   void PendingRequestsCallback(const RequestsCallback& callback,
                                ErrorType error,
                                scoped_ptr<Requests> requests);
 
   // The backend can be deleted via the Close function at any time so always
   // check for its existence before use.
   scoped_ptr<disk_cache::Backend> backend_;
   GURL origin_;
   base::FilePath path_;
   net::URLRequestContext* request_context_;
   scoped_refptr<storage::QuotaManagerProxy> quota_manager_proxy_;
   base::WeakPtr<storage::BlobStorageContext> blob_storage_context_;
-  bool initialized_;
+  BackendState backend_state_;
   std::vector<base::Closure> init_callbacks_;
 
   // Whether or not to store data in disk or memory.
   bool memory_only_;
 
   // The number of started operations that have yet to complete.
   // TODO(jkarlin): pending_ops_ gets double counted on lazy initialization (say
   // in ::Put). The counting still works but pending_ops_ doesn't accurately
   // represent the number of operations in flight. Fix this by having the lazy
   // init callback call a different function than the original caller (::Put).
   size_t pending_ops_;
   base::Closure ops_complete_callback_;
 
   base::WeakPtrFactory<ServiceWorkerCache> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ServiceWorkerCache);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_CACHE_H_