Add flush method to SweepstoreFileHandle for improved data synchronization

cpp/src/Private/sweepstore/header.cpp

@@ -88,7 +88,7 @@ void SweepstoreHeader::initialise() {
     writeAddressTablePointer(SweepstorePointer::NULL_PTR);
     writeFreeListCount(0);
     writeIsFreeListLifted(false);
-    file->flush();
+    file.flush();
 }
 
 uint64_t SweepstoreConcurrencyHeader::readMasterIdentifier() {
@@ -158,7 +158,7 @@ void SweepstoreConcurrencyHeader::initialise(int concurrentWorkers) {
         SweepstoreWorkerTicket ticketWriter = SweepstoreWorkerTicket(i, file);
         ticketWriter.write(ticket);
     }
-    file->flush();
+    file.flush();
 }
 
 void SweepstoreWorkerTicket::write(SweepstoreWorkerTicketSnapshot &snapshot) {
@@ -189,7 +189,7 @@ void SweepstoreWorkerTicket::write(SweepstoreWorkerTicketSnapshot &snapshot) {
     // Write to file
     file.writeSeek(getOffset());
     file.writeBytes(dataPtr, data.size());
-    file->flush();
+    file.flush();
 }
 
 bool SweepstoreWorkerTicket::writable() {

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) {

cpp/src/Public/sweepstore/utils/file_handle.h

@@ -37,6 +37,7 @@ public:
 
     bool isOpen() const;
     void close();
+    void flush();
 
     // Windows-compatible I/O wrappers
 #if defined(_WIN32) || defined(WITH_UNREAL)