Add a new wrapper for sqlite. This is mostly a large cleanup of the existing

one, combined with the statement cache in a nice way. It is designed to
entirely wrap sqlite so that we can catch corrupt errors in the future and
"do something" when we get them without having to change all the calling code.

There is also a new meta_table file which is almost exactly like the old one
but which uses the new sql interface.

This patch changes Chrome's history TextDatabase to use this new wrapper as a
proof of concept, because this usage is relatively well-confined.
Review URL: http://codereview.chromium.org/199047

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@26022 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 56 insertions, 0 deletions

diff --git a/app/sql/transaction.h b/app/sql/transaction.h
new file mode 100644
index 0000000..1e00c6f
--- /dev/null
+++ b/app/sql/transaction.h
@@ -0,0 +1,56 @@
+// Copyright (c) 2009 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 APP_SQL_TRANSACTION_H_
+#define APP_SQL_TRANSACTION_H_
+
+#include "base/basictypes.h"
+
+namespace sql {
+
+class Connection;
+
+class Transaction {
+ public:
+  // Creates the scoped transaction object. You MUST call Begin() to begin the
+  // transaction. If you have begun a transaction and not committed it, the
+  // constructor will roll back the transaction. If you want to commit, you
+  // need to manually call Commit before this goes out of scope.
+  Transaction(Connection* connection);
+  ~Transaction();
+
+  // Returns true when there is a transaction that has been successfully begun.
+  bool is_open() const { return is_open_; }
+
+  // Begins the transaction. This uses the default sqlite "deferred" transaction
+  // type, which means that the DB lock is lazily acquired the next time the
+  // database is accessed, not in the begin transaction command.
+  //
+  // Returns false on failure. Note that if this fails, you shouldn't do
+  // anything you expect to be actually transactional, because it won't be!
+  bool Begin();
+
+  // Rolls back the transaction. This will happen automatically if you do
+  // nothing when the transaction goes out of scope.
+  void Rollback();
+
+  // Commits the transaction, returning true on success. This will return
+  // false if sqlite could not commit it, or if another transaction in the
+  // same outermost transaction has been rolled back (which necessitates a
+  // rollback of all transactions in that outermost one).
+  bool Commit();
+
+ private:
+  Connection* connection_;
+
+  // True when the transaction is open, false when it's already been committed
+  // or rolled back.
+  bool is_open_;
+
+  DISALLOW_COPY_AND_ASSIGN(Transaction);
+};
+
+}  // namespace sql
+
+#endif  // APP_SQL_TRANSACTION_H_