sqlite: add ability to interrupt statements

By encapsulating sqlite3_exec into its own standalone method
and introducing the 'SQliteExecHandler' class, we enable the
ability to test db statements execution failures within the
unit test framework.

This is used in the following-up commit to exercise a deadlock
and improve our wallet db error handling code.

Moreover, the future encapsulation of other sqlite functions
within this class will contribute to minimize the impact of
any future API changes.

1 files changed, 12 insertions, 0 deletions

diff --git a/src/wallet/sqlite.h b/src/wallet/sqlite.h
index f1ce0567e1..de9ba8fd99 100644
--- a/src/wallet/sqlite.h
+++ b/src/wallet/sqlite.h
@@ -36,11 +36,21 @@ public:
     Status Next(DataStream& key, DataStream& value) override;
 };
 
+/** Class responsible for executing SQL statements in SQLite databases.
+ *  Methods are virtual so they can be overridden by unit tests testing unusual database conditions. */
+class SQliteExecHandler
+{
+public:
+    virtual ~SQliteExecHandler() {}
+    virtual int Exec(SQLiteDatabase& database, const std::string& statement);
+};
+
 /** RAII class that provides access to a WalletDatabase */
 class SQLiteBatch : public DatabaseBatch
 {
 private:
     SQLiteDatabase& m_database;
+    std::unique_ptr<SQliteExecHandler> m_exec_handler{std::make_unique<SQliteExecHandler>()};
 
     sqlite3_stmt* m_read_stmt{nullptr};
     sqlite3_stmt* m_insert_stmt{nullptr};
@@ -61,6 +71,8 @@ public:
     explicit SQLiteBatch(SQLiteDatabase& database);
     ~SQLiteBatch() override { Close(); }
 
+    void SetExecHandler(std::unique_ptr<SQliteExecHandler>&& handler) { m_exec_handler = std::move(handler); }
+
     /* No-op. See comment on SQLiteDatabase::Flush */
     void Flush() override {}