RAII wrapper for sqlite transactions, better transaction handling in key value repo.

src/common/repository/sqlite/KeyValueRepositorySqlite.cxx

@@ -18,6 +18,7 @@
 #include "KeyValueRepositorySqlite.hxx"
 #include "Logger.hxx"
 #include "SqliteError.hxx"
+#include "SqliteTransaction.hxx"
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 KeyValueRepositorySqlite::KeyValueRepositorySqlite(
@@ -51,9 +52,9 @@ std::map<string, Variant> KeyValueRepositorySqlite::load()
 void KeyValueRepositorySqlite::save(const std::map<string, Variant>& values)
 {
   try {
-    myStmtInsert->reset();
+    SqliteTransaction tx(myDb);
 
-    myDb.exec("BEGIN TRANSACTION");
+    myStmtInsert->reset();
 
     for (const auto& pair: values) {
       (*myStmtInsert)
@@ -64,7 +65,7 @@ void KeyValueRepositorySqlite::save(const std::map<string, Variant>& values)
       myStmtInsert->reset();
     }
 
-    myDb.exec("COMMIT");
+    tx.commit();
   }
   catch (SqliteError err) {
     Logger::log(err.message, 1);

src/common/repository/sqlite/SqliteTransaction.cxx

@@ -0,0 +1,51 @@
+//============================================================================
+//
+//   SSSS    tt          lll  lll
+//  SS  SS   tt           ll   ll
+//  SS     tttttt  eeee   ll   ll   aaaa
+//   SSSS    tt   ee  ee  ll   ll      aa
+//      SS   tt   eeeeee  ll   ll   aaaaa  --  "An Atari 2600 VCS Emulator"
+//  SS  SS   tt   ee      ll   ll  aa  aa
+//   SSSS     ttt  eeeee llll llll  aaaaa
+//
+// Copyright (c) 1995-2019 by Bradford W. Mott, Stephen Anthony
+// and the Stella Team
+//
+// See the file "License.txt" for information on usage and redistribution of
+// this file, and for a DISCLAIMER OF ALL WARRANTIES.
+//============================================================================
+
+#include "SqliteTransaction.hxx"
+#include "SqliteDatabase.hxx"
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+SqliteTransaction::SqliteTransaction(SqliteDatabase& db)
+  : myDb(db),
+    myTransactionClosed(false)
+{
+  myDb.exec("BEGIN TRANSACTION");
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+SqliteTransaction::~SqliteTransaction()
+{
+  if (!myTransactionClosed) rollback();
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void SqliteTransaction::commit()
+{
+  if (myTransactionClosed) return;
+
+  myTransactionClosed = true;
+  myDb.exec("COMMIT TRANSACTION");
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void SqliteTransaction::rollback()
+{
+  if (myTransactionClosed) return;
+
+  myTransactionClosed = true;
+  myDb.exec("ROLLBACK TRANSACTION");
+}

src/common/repository/sqlite/SqliteTransaction.hxx

@@ -0,0 +1,48 @@
+//============================================================================
+//
+//   SSSS    tt          lll  lll
+//  SS  SS   tt           ll   ll
+//  SS     tttttt  eeee   ll   ll   aaaa
+//   SSSS    tt   ee  ee  ll   ll      aa
+//      SS   tt   eeeeee  ll   ll   aaaaa  --  "An Atari 2600 VCS Emulator"
+//  SS  SS   tt   ee      ll   ll  aa  aa
+//   SSSS     ttt  eeeee llll llll  aaaaa
+//
+// Copyright (c) 1995-2019 by Bradford W. Mott, Stephen Anthony
+// and the Stella Team
+//
+// See the file "License.txt" for information on usage and redistribution of
+// this file, and for a DISCLAIMER OF ALL WARRANTIES.
+//============================================================================
+
+#ifndef SQLITE_TRANSACTION_HXX
+#define SQLITE_TRANSACTION_HXX
+
+class SqliteDatabase;
+
+class SqliteTransaction {
+  public:
+
+    SqliteTransaction(SqliteDatabase& db);
+
+    ~SqliteTransaction();
+
+    void commit();
+
+    void rollback();
+
+  private:
+
+    SqliteDatabase& myDb;
+
+    bool myTransactionClosed;
+
+  private:
+
+    SqliteTransaction(const SqliteTransaction&) = delete;
+    SqliteTransaction(SqliteTransaction&&) = delete;
+    SqliteTransaction& operator=(const SqliteTransaction&) = delete;
+    SqliteTransaction& operator=(SqliteTransaction&&) = delete;
+};
+
+#endif // SQLITE_TRANSACTION_HXX

src/common/repository/sqlite/module.mk

@@ -4,7 +4,8 @@ MODULE_OBJS := \
 	src/common/repository/sqlite/KeyValueRepositorySqlite.o \
 	src/common/repository/sqlite/SettingsDb.o \
 	src/common/repository/sqlite/SqliteDatabase.o \
-	src/common/repository/sqlite/SqliteStatement.o
+	src/common/repository/sqlite/SqliteStatement.o \
+	src/common/repository/sqlite/SqliteTransaction.o
 
 MODULE_DIRS += \
 	src/common/repository/sqlite