diff -r 000000000000 -r 6474c204b198 storage/src/mozStoragePrivateHelpers.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/storage/src/mozStoragePrivateHelpers.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,85 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozStoragePrivateHelpers_h
+#define mozStoragePrivateHelpers_h
+
+/**
+ * This file contains convenience methods for mozStorage.
+ */
+
+#include "sqlite3.h"
+#include "nsIVariant.h"
+#include "nsError.h"
+#include "nsAutoPtr.h"
+#include "js/TypeDecls.h"
+
+class mozIStorageCompletionCallback;
+class mozIStorageBaseStatement;
+class mozIStorageBindingParams;
+class nsIRunnable;
+
+namespace mozilla {
+namespace storage {
+
+////////////////////////////////////////////////////////////////////////////////
+//// Macros
+
+#define ENSURE_INDEX_VALUE(aIndex, aCount) \
+  NS_ENSURE_TRUE(aIndex < aCount, NS_ERROR_INVALID_ARG)
+
+////////////////////////////////////////////////////////////////////////////////
+//// Functions
+
+/**
+ * Converts a SQLite return code to an nsresult return code.
+ *
+ * @param aSQLiteResultCode
+ *        The SQLite return code to convert.
+ * @returns the corresponding nsresult code for aSQLiteResultCode.
+ */
+nsresult convertResultCode(int aSQLiteResultCode);
+
+/**
+ * Checks the performance of a SQLite statement and logs a warning with
+ * NS_WARNING.  Currently this only checks the number of sort operations done
+ * on a statement, and if more than zero have been done, the statement can be
+ * made faster with the careful use of an index.
+ *
+ * @param aStatement
+ *        The sqlite3_stmt object to check.
+ */
+void checkAndLogStatementPerformance(sqlite3_stmt *aStatement);
+
+/**
+ * Convert the provided JS::Value into a variant representation if possible.
+ *
+ * @param aCtx
+ *        The JSContext the value is from.
+ * @param aValue
+ *        The JavaScript value to convert.  All primitive types are supported,
+ *        but only Date objects are supported from the Date family.  Date
+ *        objects are coerced to PRTime (nanoseconds since epoch) values.
+ * @return the variant if conversion was successful, nullptr if conversion
+ *         failed.  The caller is responsible for addref'ing if non-null.
+ */
+nsIVariant *convertJSValToVariant(JSContext *aCtx, JS::Value aValue);
+
+/**
+ * Obtains an event that will notify a completion callback about completion.
+ *
+ * @param aCallback
+ *        The callback to be notified.
+ * @return an nsIRunnable that can be dispatched to the calling thread.
+ */
+already_AddRefed<nsIRunnable> newCompletionEvent(
+  mozIStorageCompletionCallback *aCallback
+);
+
+} // namespace storage
+} // namespace mozilla
+
+#endif // mozStoragePrivateHelpers_h