Create a class to represent a DOM Storage Database.

webkit/dom_storage/dom_storage_database.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.
+
+#ifndef WEBKIT_DOM_STORAGE_DOM_STORAGE_DATABASE_H_
+#define WEBKIT_DOM_STORAGE_DOM_STORAGE_DATABASE_H_
+
+#include <map>
+#include <set>
+
+#include "base/file_path.h"
+#include "base/gtest_prod_util.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/string16.h"
+#include "sql/connection.h"
+
+namespace dom_storage {
+
+// Represents a SQLite based backing for DOM storage data. This
+// class is designed to be used on a single thread.
+class DomStorageDatabase {
+ public:
+  explicit DomStorageDatabase(const FilePath& file_path);
+  virtual ~DomStorageDatabase();
+
+  typedef std::map<string16, string16> ValuesMap;
+  typedef std::set<string16> ValuesSet;
+
+  // Open the database at file_path_, creating it if it does not exist.
+  // Returns false on failure.
+  virtual bool Open();
+
+  // Initiate the Dom Storage database and create tables as necessary.
+  // Also performs database upgrades if necessary. Returns true if the
+  // tables were created or upgraded successfully.
+  virtual bool Init();

[michaeln, 2012/01/31 03:11:16]

In other 'db' classes we create and open underlying database files very lazily
to avoid creating files unless we really need to. In those classes, there
usually isn't a public Open() method at all, and instead a private a
LazyOpen(bool create_if_needed) method gets called internally as needed. I'd
vote to follow that pattern here too. Take a look at quota_database.cc &|
appcache_database.cc for examples of this pattern.

[benm (inactive), 2012/01/31 15:10:53]

sgtm.

+
+  // Reads all the key, value pairs stored in the database and returns
+  // them.
+  virtual ValuesMap ReadAllValues() const;

[michaeln, 2012/01/31 03:11:16]

do you know if all of our compilers are smart enough to not copy the collection
upon return? the old-schooler in me likes to see ptr args to non-const data for
methods that compute large amount values

[benm (inactive), 2012/01/31 15:10:53]

I would've thought so, but don't know for certain. Happy to change to output ptr
param.

+
+  // Write all |values| into the database, overwriting previously set
+  // keys and values.
+  virtual bool WriteValues(const ValuesMap& values);

[michaeln, 2012/01/31 03:11:16]

do the methods of this class need to be virtual?

[benm (inactive), 2012/01/31 15:10:53]

I think the virtuals are left over from an older iteration where I had this
class deriving from an interface, so I don't think they are necessary any more.

+
+  // Removes the |keys| and their mappings from the database.
+  virtual bool RemoveValues(const ValuesSet& keys);
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(DomStorageDatabaseTest, SimpleOpenInitAndClose);
+  FRIEND_TEST_ALL_PREFIXES(DomStorageDatabaseTest,
+                           TestInitUpgradesV1TableToV2);
+  FRIEND_TEST_ALL_PREFIXES(DomStorageDatabaseTest, TestIsOpen);
+  FRIEND_TEST_ALL_PREFIXES(DomStorageDatabaseTest, SimpleRead);
+  FRIEND_TEST_ALL_PREFIXES(DomStorageDatabaseTest, SimpleWrite);
+  FRIEND_TEST_ALL_PREFIXES(DomStorageDatabaseTest, UpgradeFromV1ToV2NoData);
+  FRIEND_TEST_ALL_PREFIXES(DomStorageDatabaseTest,
+                           UpgradeFromV1ToV2WithData);
+  FRIEND_TEST_ALL_PREFIXES(DomStorageDatabaseTest,
+                           TestOpenCloseDataPreserved);
+  FRIEND_TEST_ALL_PREFIXES(DomStorageDatabaseTest, TestSimpleRemoveOneValue);
+
+  // Creates the ItemTable at the current version of the database.
+  bool CreateTable();
+  bool CreateTableV2();
+
+  // Version 1 -> 2 migrated the value column in the ItemTable from a TEXT
+  // to a BLOB. Exisitng data is preserved.
+  bool UpgradeVersion1To2IfNeeded();
+
+  void Close();
+  bool IsOpen() const { return db_.get() ? db_->is_open() : false; }
+
+  // Path to the database on disk.
+  FilePath file_path_;
+  scoped_ptr<sql::Connection> db_;
+};
+
+}  // namespace dom_storage
+
+#endif  // WEBKIT_DOM_STORAGE_DOM_STORAGE_DATABASE_H_