AppCacheHost cache selection algorithm

webkit/appcache/appcache_service.h

 // Copyright (c) 2009 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 WEBKIT_APPCACHE_APPCACHE_SERVICE_H_
 #define WEBKIT_APPCACHE_APPCACHE_SERVICE_H_
 
 #include <map>
 #include <set>
 #include <vector>
 
 #include "base/hash_tables.h"
 #include "base/file_path.h"
 #include "base/ref_counted.h"
+#include "base/task.h"
 #include "net/url_request/url_request_context.h"
 #include "googleurl/src/gurl.h"
 
 namespace appcache {
 
 class AppCache;
 class AppCacheBackendImpl;
 class AppCacheGroup;
 
 // Class that manages the application cache service. Sends notifications
 // to many frontends.  One instance per user-profile. Each instance has
 // exclusive access to it's cache_directory on disk.
 class AppCacheService {
  public:
+
+  class LoadClient {
+   public:
+    virtual ~LoadClient() {}
+
+    // If a load fails the object pointer will be NULL.
+    virtual void CacheLoadedCallback(AppCache* cache, int64 cache_id) = 0;
+    virtual void GroupLoadedCallback(AppCacheGroup* cache,
+                                     const GURL& manifest_url) = 0;
+  };
+
   AppCacheService();
   virtual ~AppCacheService();
 
   void Initialize(const FilePath& cache_directory);
 
   // Context for use during cache updates, should only be accessed
   // on the IO thread.
   URLRequestContext* request_context() { return request_context_.get(); }
   void set_request_context(URLRequestContext* context) {
     // TODO(michaeln): need to look into test failures that occur
     // when we take this reference? Stubbing out for now.
     // request_context_ = context;
   }
 
   // TODO(jennb): API to set service settings, like file paths for storage
 
-  // track which processes are using this appcache service
+  // Track which processes are using this appcache service.
   void RegisterBackend(AppCacheBackendImpl* backend_impl);
   void UnregisterBackend(AppCacheBackendImpl* backend_impl);
-
-  void AddCache(AppCache* cache);
-  void RemoveCache(AppCache* cache);
-  void AddGroup(AppCacheGroup* group);
-  void RemoveGroup(AppCacheGroup* group);
-
   AppCacheBackendImpl* GetBackend(int id) {
     BackendMap::iterator it = backends_.find(id);
     return (it != backends_.end()) ? it->second : NULL;
   }
 
+  // Track what we have in or in-memory cache.
+  void AddCache(AppCache* cache);
+  void RemoveCache(AppCache* cache);
+  void AddGroup(AppCacheGroup* group);
+  void RemoveGroup(AppCacheGroup* group);
   AppCache* GetCache(int64 id) {
     CacheMap::iterator it = caches_.find(id);
     return (it != caches_.end()) ? it->second : NULL;
   }
-
   AppCacheGroup* GetGroup(const GURL& manifest_url) {
     GroupMap::iterator it = groups_.find(manifest_url);
     return (it != groups_.end()) ? it->second : NULL;
   }
 
+  // Load caches and groups from storage. If the request object
+  // is already in memory, the client is called immediately
+  // without returning to the message loop.
+  void LoadCache(int64 id, LoadClient* client);
+  void LoadOrCreateGroup(const GURL& manifest_url,
+                         LoadClient* client);
+
+  // Cancels pending callbacks for this client.
+  void CancelLoads(LoadClient* client);
+
+  // Updates in memory and persistent storage.
+  void MarkAsForeignEntry(const GURL& entry_url, int64 cache_id);
+
   // The service generates unique storage ids for different object types.
   int64 NewCacheId() { return ++last_cache_id_; }
   int64 NewGroupId() { return ++last_group_id_; }
   int64 NewEntryId() { return ++last_entry_id_; }
   int64 NewResponseId() { return ++last_response_id_; }
 
  private:
   // In-memory representation of stored appcache data. Represents a subset
   // of the appcache database currently in use.
   typedef base::hash_map<int64, AppCache*> CacheMap;
   typedef std::map<GURL, AppCacheGroup*> GroupMap;
   CacheMap caches_;
   GroupMap groups_;
 
   // The last storage id used for different object types.
   int64 last_cache_id_;
   int64 last_group_id_;
   int64 last_entry_id_;
   int64 last_response_id_;
 
   // Track current processes.  One 'backend' per child process.
   typedef std::map<int, AppCacheBackendImpl*> BackendMap;
   BackendMap backends_;
 
+  // Where we save our data.
   FilePath cache_directory_;
 
   // Context for use during cache updates.
   scoped_refptr<URLRequestContext> request_context_;
 
-  // TODO(jennb): info about appcache storage
-  // AppCacheDatabase db_;
-  // DiskCache response_storage_;
-
+  // TODO(michaeln): cache and group loading book keeping.
+  // TODO(michaeln): database and response storage
   // TODO(jennb): service state: e.g. reached quota?
 };
 
 }  // namespace appcache
 
 #endif  // WEBKIT_APPCACHE_APPCACHE_SERVICE_H_