Add flush method to SweepstoreFileHandle for improved data synchronization

cpp/src/Private/sweepstore/utils/file_handle.cpp

@@ -55,6 +55,23 @@ void SweepstoreFileHandle::close() {
 #endif
 }
 
+// flush
+void SweepstoreFileHandle::flush() {
+#ifdef WITH_UNREAL
+    if (unrealHandle) {
+        unrealHandle->Flush();
+    }
+#else
+    if (stream) {
+        stream->flush();
+#ifdef _WIN32
+        // On Windows, also sync to ensure data hits disk
+        stream->sync();
+#endif
+    }
+#endif
+}
+
 #if defined(_WIN32) || defined(WITH_UNREAL)
 // readSeek
 void SweepstoreFileHandle::readSeek(std::streampos pos, std::ios::seekdir dir) {