Reland of "Remove void** from disk_cache interface" w/ blockfile iter fix.

net/disk_cache/blockfile/backend_impl.h

 // 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.
 
 // See net/disk_cache/disk_cache.h for the public interface of the cache.
 
 #ifndef NET_DISK_CACHE_BLOCKFILE_BACKEND_IMPL_H_
 #define NET_DISK_CACHE_BLOCKFILE_BACKEND_IMPL_H_
 
 #include "base/containers/hash_tables.h"
@@ skipping 56 matching lines @@
   void CleanupCache();
 
   // Synchronous implementation of the asynchronous interface.
   int SyncOpenEntry(const std::string& key, Entry** entry);
   int SyncCreateEntry(const std::string& key, Entry** entry);
   int SyncDoomEntry(const std::string& key);
   int SyncDoomAllEntries();
   int SyncDoomEntriesBetween(base::Time initial_time,
                              base::Time end_time);
   int SyncDoomEntriesSince(base::Time initial_time);
-  int SyncOpenNextEntry(void** iter, Entry** next_entry);
-  void SyncEndEnumeration(void* iter);
+  int SyncOpenNextEntry(Rankings::Iterator* iterator, Entry** next_entry);
+  void SyncEndEnumeration(scoped_ptr<Rankings::Iterator> iterator);
   void SyncOnExternalCacheHit(const std::string& key);
 
   // Open or create an entry for the given |key| or |iter|.
   EntryImpl* OpenEntryImpl(const std::string& key);
   EntryImpl* CreateEntryImpl(const std::string& key);
-  EntryImpl* OpenNextEntryImpl(void** iter);
+  EntryImpl* OpenNextEntryImpl(Rankings::Iterator* iter);
 
   // Sets the maximum size for the total amount of data stored by this instance.
   bool SetMaxSize(int max_bytes);
 
   // Sets the cache type for this backend.
   void SetType(net::CacheType type);
 
   // Returns the full name for an external storage file.
   base::FilePath GetFileName(Addr address) const;
 
@@ skipping 171 matching lines @@
   virtual int CreateEntry(const std::string& key, Entry** entry,
                           const CompletionCallback& callback) OVERRIDE;
   virtual int DoomEntry(const std::string& key,
                         const CompletionCallback& callback) OVERRIDE;
   virtual int DoomAllEntries(const CompletionCallback& callback) OVERRIDE;
   virtual int DoomEntriesBetween(base::Time initial_time,
                                  base::Time end_time,
                                  const CompletionCallback& callback) OVERRIDE;
   virtual int DoomEntriesSince(base::Time initial_time,
                                const CompletionCallback& callback) OVERRIDE;
-  virtual int OpenNextEntry(void** iter, Entry** next_entry,
-                            const CompletionCallback& callback) OVERRIDE;
-  virtual void EndEnumeration(void** iter) OVERRIDE;
+  // NOTE: The blockfile Backend::Iterator::OpenNextEntry method does not modify
+  // the last_used field of the entry, and therefore it does not impact the
+  // eviction ranking of the entry. However, an enumeration will go through all
+  // entries on the cache only if the cache is not modified while the
+  // enumeration is taking place. Significantly altering the entry pointed by
+  // the iterator (for example, deleting the entry) will invalidate the
+  // iterator. Performing operations on an entry that modify the entry may
+  // result in loops in the iteration, skipped entries or similar.
+  virtual scoped_ptr<Iterator> CreateIterator() OVERRIDE;
   virtual void GetStats(StatsItems* stats) OVERRIDE;
   virtual void OnExternalCacheHit(const std::string& key) OVERRIDE;
 
  private:
   typedef base::hash_map<CacheAddr, EntryImpl*> EntriesMap;
+  class IteratorImpl;
 
   // Creates a new backing file for the cache index.
   bool CreateBackingStore(disk_cache::File* file);
   bool InitBackingStore(bool* file_created);
   void AdjustMaxCacheSize(int table_len);
 
   bool InitStats();
   void StoreStats();
 
   // Deletes the cache and starts again.
@@ skipping 96 matching lines @@
   base::WaitableEvent done_;  // Signals the end of background work.
   scoped_refptr<TraceObject> trace_object_;  // Initializes internal tracing.
   base::WeakPtrFactory<BackendImpl> ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BackendImpl);
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_BLOCKFILE_BACKEND_IMPL_H_