[Storage] Blob items are now shared between blobs. Ready for disk swap.

storage/browser/blob/blob_storage_context.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 STORAGE_BROWSER_BLOB_BLOB_STORAGE_CONTEXT_H_
 #define STORAGE_BROWSER_BLOB_BLOB_STORAGE_CONTEXT_H_
 
 #include <map>
 #include <string>
+#include <vector>
 
 #include "base/memory/ref_counted.h"
-#include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "storage/browser/blob/blob_data_handle.h"
+#include "storage/browser/blob/blob_data_item.h"
 #include "storage/browser/blob/blob_data_snapshot.h"
+#include "storage/browser/blob/internal_blob_data.h"
+#include "storage/browser/blob/shareable_blob_data_item.h"
 #include "storage/browser/storage_browser_export.h"
 #include "storage/common/data_element.h"
 
 class GURL;
 
 namespace base {
 class FilePath;
 class Time;
 }
 
 namespace content {
 class BlobStorageHost;
 }
 
 namespace storage {
 
-class BlobDataHandle;
 class BlobDataBuilder;
+class InternalBlobData;
 
 // This class handles the logistics of blob Storage within the browser process,
 // and maintains a mapping from blob uuid to the data. The class is single
 // threaded and should only be used on the IO thread.
 // In chromium, there is one instance per profile.
 class STORAGE_EXPORT BlobStorageContext
     : public base::SupportsWeakPtr<BlobStorageContext> {
  public:
   BlobStorageContext();
   ~BlobStorageContext();
 
   scoped_ptr<BlobDataHandle> GetBlobDataFromUUID(const std::string& uuid);
   scoped_ptr<BlobDataHandle> GetBlobDataFromPublicURL(const GURL& url);
 
   // Useful for coining blobs from within the browser process. If the
   // blob cannot be added due to memory consumption, returns NULL.
-  scoped_ptr<BlobDataHandle> AddFinishedBlob(const BlobDataBuilder& blob_data);
+  // A builder should not be used twice to create blobs, as the internal
+  // resources are refcounted instead of copied for memory efficiency.
+  // To cleanly use a builder multiple times, please call Clone() on the
+  // builder, or even better for memory savings, clear the builder and append
+  // the previously constructed blob.
+  scoped_ptr<BlobDataHandle> AddFinishedBlob(BlobDataBuilder* builder);
 
   // Useful for coining blob urls from within the browser process.
   bool RegisterPublicBlobURL(const GURL& url, const std::string& uuid);
   void RevokePublicBlobURL(const GURL& url);
 
+  size_t memory_usage() const { return memory_usage_; }
+
  private:
   friend class content::BlobStorageHost;
   friend class BlobDataHandle::BlobDataHandleShared;
   friend class ViewBlobInternalsJob;
 
   enum EntryFlags {
     EXCEEDED_MEMORY = 1 << 1,
   };
 
   struct BlobMapEntry {
     int refcount;
     int flags;
     // data and data_builder are mutually exclusive.
-    scoped_ptr<BlobDataSnapshot> data;
-    scoped_ptr<BlobDataBuilder> data_builder;
+    scoped_ptr<InternalBlobData> data;
+    scoped_ptr<InternalBlobData::Builder> data_builder;
 
     BlobMapEntry();
-    BlobMapEntry(int refcount, BlobDataBuilder* data);
+    BlobMapEntry(int refcount, InternalBlobData::Builder* data);
     ~BlobMapEntry();
 
     bool IsBeingBuilt();
   };
 
   typedef std::map<std::string, BlobMapEntry*> BlobMap;
   typedef std::map<GURL, std::string> BlobURLMap;
 
   // Called by BlobDataHandle.
   scoped_ptr<BlobDataSnapshot> CreateSnapshot(const std::string& uuid);
 
+  // ### Methods called by BlobStorageHost ###
   void StartBuildingBlob(const std::string& uuid);
   void AppendBlobDataItem(const std::string& uuid,
-                          const DataElement& data_item);
+                          const storage::DataElement& data_item);

[michaeln, 2015/02/05 20:02:09]

storage:: not needed here

[dmurph, 2015/02/06 01:32:30]

Done

   void FinishBuildingBlob(const std::string& uuid, const std::string& type);
   void CancelBuildingBlob(const std::string& uuid);
   void IncrementBlobRefCount(const std::string& uuid);
   void DecrementBlobRefCount(const std::string& uuid);
+  // #########################################
 
-  bool ExpandStorageItems(BlobDataBuilder* target_blob_data,
-                          const BlobDataSnapshot& src_blob_data,
-                          uint64 offset,
-                          uint64 length);
-  bool AppendBytesItem(BlobDataBuilder* target_blob_data,
-                       const char* data,
-                       int64 length);
-  void AppendFileItem(BlobDataBuilder* target_blob_data,
-                      const base::FilePath& file_path,
-                      uint64 offset,
-                      uint64 length,
-                      const base::Time& expected_modification_time);
-  void AppendFileSystemFileItem(BlobDataBuilder* target_blob_data,
-                                const GURL& url,
-                                uint64 offset,
-                                uint64 length,
-                                const base::Time& expected_modification_time);
+  // Returns if we can fit the given data element in memory.  This does not
+  // decompose blobs, that check happens in AppendBlobItem.
+  bool CanFitDataElement(const DataElement& item);
+
+  // Flags the entry for exceeding memory, and resets the builder.
+  void BlobEntryExceededMemory(BlobMapEntry* entry);
+
+  // Allocates memory to hold the given data element and copies the data over.
+  scoped_refptr<BlobDataItem> TransformDataElement(
+      const std::string& uuid,
+      const DataElement& data_item);
+
+  // Appends the given blob item to the blob builder.  The new blob
+  // retains ownership of data_item if applicable, and returns false if there
+  // wasn't enough memory to hold the item.
+  bool AppendAllocatedBlobItem(const std::string& target_blob_uuid,
+                               InternalBlobData::Builder* target_blob_data,
+                               scoped_refptr<BlobDataItem> data_item);
+
+  // Deconstructs the blob and appends it's contents to the target blob.  Items
+  // are shared if possible, and copied if the given offset and length
+  // have to split an item.
+  bool AppendBlob(const std::string& target_blob_uuid,
+                  InternalBlobData::Builder* target_blob_data,
+                  const InternalBlobData& blob,
+                  size_t offset,
+                  size_t length);
 
   bool IsInUse(const std::string& uuid);
   bool IsBeingBuilt(const std::string& uuid);
   bool IsUrlRegistered(const GURL& blob_url);
+  scoped_ptr<BlobDataSnapshot> CreateSnapshot(const std::string& uuid,

[michaeln, 2015/02/05 22:58:47]

just noticing this is a new CreateSnapshot overload, where is this used beside
the original CreateSnapshot method?

[dmurph, 2015/02/06 01:32:30]

Inlined.

+                                              const InternalBlobData& data);
 
   BlobMap blob_map_;
   BlobURLMap public_blob_urls_;
 
   // Used to keep track of how much memory is being utilized for blob data,
   // we count only the items of TYPE_DATA which are held in memory and not
   // items of TYPE_FILE.
-  int64 memory_usage_;
+  size_t memory_usage_;
 
   DISALLOW_COPY_AND_ASSIGN(BlobStorageContext);
 };
 
 }  // namespace storage
 
 #endif  // STORAGE_BROWSER_BLOB_BLOB_STORAGE_CONTEXT_H_