[BlobAsync] Patch 1: BlobStorageRegistry

storage/browser/blob/blob_storage_registry.h

+// Copyright 2015 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_REGISTRY_H_
+#define STORAGE_BROWSER_BLOB_BLOB_STORAGE_REGISTRY_H_
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include "base/callback_forward.h"
+#include "base/containers/scoped_ptr_hash_map.h"
+#include "base/macros.h"
+#include "storage/browser/blob/internal_blob_data.h"
+#include "storage/browser/storage_browser_export.h"
+
+class GURL;
+
+namespace storage {
+
+// This class stores the blob data in the various states of construction, as
+// well as URL mappings to blob uuids.
+// Implementation notes:
+// * There is no implicit refcounting in this class, except for setting the
+//   refcount to 1 on registration.
+// * When removing a uuid registration, we do not check for URL mappings to that
+//   uuid. The user must keep track of these.
+class STORAGE_EXPORT BlobStorageRegistry {
+ public:
+  enum class BlobState {
+    // First the renderer reserves the uuid.
+    RESERVED = 1,
+    // Second, we are asynchronously transporting data to the browser.
+    ASYNC_TRANSPORTATION,
+    // Third, we construct the blob when we have all of the data.
+    CONSTRUCTION,
+    // Finally, the blob is built.
+    ACTIVE
+  };
+
+  struct STORAGE_EXPORT Entry {
+    size_t refcount;
+    BlobState state;
+    std::vector<base::Callback<void(bool)>> construction_complete_callbacks;
+
+    // Flags
+    bool exceeded_memory;
+
+    // data and data_builder are mutually exclusive.
+    scoped_ptr<InternalBlobData> data;
+    scoped_ptr<InternalBlobData::Builder> data_builder;
+
+    Entry() = delete;
+    Entry(int refcount, BlobState state);
+    ~Entry();
+
+    // Performs a test-and-set on the state of the given blob. If the state
+    // isn't as expected, we return false. Otherwise we set the new state and
+    // return true.
+    bool TestAndSetState(BlobState expected, BlobState set);
+  };
+
+  BlobStorageRegistry();
+  ~BlobStorageRegistry();
+
+  // Creates the blob entry with a refcount of 1 and a state of RESERVED. If
+  // the blob is already in use, we return null.
+  Entry* CreateEntry(const std::string& uuid);
+
+  // Removes the blob entry with the given uuid. This does not unmap any
+  // URLs that are pointing to this uuid. Returns if the entry existed.
+  bool DeleteEntry(const std::string& uuid);
+
+  // Gets the blob entry for the given uuid. Returns nullptr if the entry
+  // does not exist.
+  Entry* GetEntry(const std::string& uuid);
+
+  // Creates a url mapping from blob uuid to the given url. Returns false if
+  // the uuid isn't mapped to an entry or if there already is a map for the URL.
+  bool CreateUrlMapping(const GURL& url, const std::string& uuid);
+
+  // Removes the given URL mapping. Optionally populates a uuid string of the
+  // removed entry uuid. Returns false if the url isn't mapped.
+  bool DeleteURLMapping(const GURL& url, std::string* uuid);
+
+  // Returns if the url is mapped to a blob uuid.
+  bool IsURLMapped(const GURL& blob_url) const;
+
+  // Returns the entry from the given url, and optionally populates the uuid for
+  // that entry. Returns a nullptr if the mapping or entry doesn't exist.
+  Entry* GetEntryFromURL(const GURL& url, std::string* uuid);
+
+  size_t blob_count() const { return blob_map_.size(); }
+  size_t url_count() const { return url_to_uuid_.size(); }
+
+ private:
+  using BlobMap = base::ScopedPtrHashMap<std::string, scoped_ptr<Entry>>;
+  using URLMap = std::map<GURL, std::string>;
+
+  BlobMap blob_map_;
+  URLMap url_to_uuid_;
+
+  DISALLOW_COPY_AND_ASSIGN(BlobStorageRegistry);
+};
+
+}  // namespace storage
+#endif  // STORAGE_BROWSER_BLOB_BLOB_STORAGE_REGISTRY_H_