Revert of Remove void** from disk_cache interface.

net/disk_cache/simple/simple_backend_impl.h

 // Copyright (c) 2013 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_DISK_CACHE_SIMPLE_SIMPLE_BACKEND_IMPL_H_
 #define NET_DISK_CACHE_SIMPLE_SIMPLE_BACKEND_IMPL_H_
 
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/callback_forward.h"
 #include "base/compiler_specific.h"
 #include "base/containers/hash_tables.h"
 #include "base/files/file_path.h"
+#include "base/id_map.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/task_runner.h"
 #include "base/time/time.h"
 #include "net/base/cache_type.h"
 #include "net/disk_cache/disk_cache.h"
 #include "net/disk_cache/simple/simple_entry_impl.h"
 #include "net/disk_cache/simple/simple_index_delegate.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 class TaskRunner;
 }
 
 namespace disk_cache {
 
 // SimpleBackendImpl is a new cache backend that stores entries in individual
 // files.
 // See http://www.chromium.org/developers/design-documents/network-stack/disk-cache/very-simple-backend
 //
-// The SimpleBackendImpl provides safe iteration; mutating entries during
-// iteration cannot cause a crash. It is undefined whether entries created or
-// destroyed during the iteration will be included in any pre-existing
-// iterations.
-//
 // The non-static functions below must be called on the IO thread unless
 // otherwise stated.
 
 class SimpleEntryImpl;
 class SimpleIndex;
 
 class NET_EXPORT_PRIVATE SimpleBackendImpl : public Backend,
     public SimpleIndexDelegate,
     public base::SupportsWeakPtr<SimpleBackendImpl> {
  public:
@@ skipping 43 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 scoped_ptr<Iterator> CreateIterator() OVERRIDE;
+  virtual int OpenNextEntry(void** iter, Entry** next_entry,
+                            const CompletionCallback& callback) OVERRIDE;
+  virtual void EndEnumeration(void** iter) OVERRIDE;
   virtual void GetStats(
       std::vector<std::pair<std::string, std::string> >* stats) OVERRIDE;
   virtual void OnExternalCacheHit(const std::string& key) OVERRIDE;
 
  private:
-  class SimpleIterator;
-  friend class SimpleIterator;
+  typedef base::hash_map<uint64, SimpleEntryImpl*> EntryMap;
 
-  typedef base::hash_map<uint64, SimpleEntryImpl*> EntryMap;
+  typedef IDMap<std::vector<uint64>, IDMapOwnPointer> ActiveEnumerationMap;
 
   typedef base::Callback<void(base::Time mtime, uint64 max_size, int result)>
       InitializeIndexCallback;
 
   class ActiveEntryProxy;
   friend class ActiveEntryProxy;
 
   // Return value of InitCacheStructureOnDisk().
   struct DiskStatResult {
     base::Time cache_dir_mtime;
     uint64 max_size;
     bool detected_magic_number_mismatch;
     int net_error;
   };
 
+  // Convert an iterator from OpenNextEntry() to the key type for
+  // ActiveEnumerationMap. Note it takes a void** argument; this is for safety;
+  // if it took a void*, that would be type compatible with a void** permitting
+  // easy calls missing the dereference.
+  static ActiveEnumerationMap::KeyType IteratorToEnumerationId(void** iter);
+
+  // Convert a key from ActiveEnumerationMap back to a void*, suitable for
+  // storing in the iterator argument to OpenNextEntry().
+  static void* EnumerationIdToIterator(
+      ActiveEnumerationMap::KeyType enumeration_id);
+
   void InitializeIndex(const CompletionCallback& callback,
                        const DiskStatResult& result);
 
   // Dooms all entries previously accessed between |initial_time| and
   // |end_time|. Invoked when the index is ready.
   void IndexReadyForDoom(base::Time initial_time,
                          base::Time end_time,
                          const CompletionCallback& callback,
                          int result);
 
@@ skipping 14 matching lines @@
   // the disk.
   int OpenEntryFromHash(uint64 entry_hash,
                         Entry** entry,
                         const CompletionCallback& callback);
 
   // Doom the entry corresponding to |entry_hash|, if it's active or currently
   // pending doom. This function does not block if there is an active entry,
   // which is very important to prevent races in DoomEntries() above.
   int DoomEntryFromHash(uint64 entry_hash, const CompletionCallback & callback);
 
+  // Called when the index is initilized to find the next entry in the iterator
+  // |iter|. If there are no more hashes in the iterator list, net::ERR_FAILED
+  // is returned. Otherwise, calls OpenEntryFromHash.
+  void GetNextEntryInIterator(void** iter,
+                              Entry** next_entry,
+                              const CompletionCallback& callback,
+                              int error_code);
+
   // Called when we tried to open an entry with hash alone. When a blank entry
   // has been created and filled in with information from the disk - based on a
   // hash alone - this checks that a duplicate active entry was not created
   // using a key in the meantime.
   void OnEntryOpenedFromHash(uint64 hash,
                              Entry** entry,
                              const scoped_refptr<SimpleEntryImpl>& simple_entry,
                              const CompletionCallback& callback,
                              int error_code);
 
   // Called when we tried to open an entry from key. When the entry has been
   // opened, a check for key mismatch is performed.
   void OnEntryOpenedFromKey(const std::string key,
                             Entry** entry,
                             const scoped_refptr<SimpleEntryImpl>& simple_entry,
                             const CompletionCallback& callback,
                             int error_code);
 
+  // Called at the end of the asynchronous operation triggered by
+  // OpenEntryFromHash. Makes sure to continue iterating if the open entry was
+  // not a success.
+  void CheckIterationReturnValue(void** iter,
+                                 Entry** entry,
+                                 const CompletionCallback& callback,
+                                 int error_code);
+
   // A callback thunk used by DoomEntries to clear the |entries_pending_doom_|
   // after a mass doom.
   void DoomEntriesComplete(scoped_ptr<std::vector<uint64> > entry_hashes,
                            const CompletionCallback& callback,
                            int result);
 
   const base::FilePath path_;
   const net::CacheType cache_type_;
   scoped_ptr<SimpleIndex> index_;
   const scoped_refptr<base::SingleThreadTaskRunner> cache_thread_;
   scoped_refptr<base::TaskRunner> worker_pool_;
 
   int orig_max_size_;
   const SimpleEntryImpl::OperationsMode entry_operations_mode_;
 
   EntryMap active_entries_;
 
+  // One entry for every enumeration in progress.
+  ActiveEnumerationMap active_enumerations_;
+
   // The set of all entries which are currently being doomed. To avoid races,
   // these entries cannot have Doom/Create/Open operations run until the doom
   // is complete. The base::Closure map target is used to store deferred
   // operations to be run at the completion of the Doom.
   base::hash_map<uint64, std::vector<base::Closure> > entries_pending_doom_;
 
   net::NetLog* const net_log_;
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_BACKEND_IMPL_H_