Fixed windows deadlocks, performance is shit tho

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

@@ -86,10 +86,27 @@ void SweepstoreFileHandle::flush() {
         unrealHandle->Flush();
     }
 #else
+    // Windows-specific implementation for guaranteed flush to disk
     auto& stream = getThreadStream();
     stream.flush();
-    // On Windows, also sync to ensure data hits disk
-    stream.sync();
+
+    // On Windows, also call sync to push to OS buffers
+    // Then open a Windows HANDLE to the same file and call FlushFileBuffers
+    // This is more reliable than trying to extract the HANDLE from fstream
+    HANDLE h = CreateFileA(
+        path.c_str(),
+        GENERIC_WRITE,
+        FILE_SHARE_READ | FILE_SHARE_WRITE,
+        NULL,
+        OPEN_EXISTING,
+        FILE_ATTRIBUTE_NORMAL,
+        NULL
+    );
+
+    if (h != INVALID_HANDLE_VALUE) {
+        FlushFileBuffers(h);
+        CloseHandle(h);
+    }
 #endif
 }
 
@@ -106,15 +123,12 @@ void SweepstoreFileHandle::readSeek(std::streampos pos, std::ios::seekdir dir) {
         unrealHandle->SeekFromEnd(unrealPos);
     }
 #else
-    // Windows
+    // Windows - simplified to only seek read pointer
     auto& stream = getThreadStream();
-    // On Windows, flush and sync to disk, then invalidate buffers
-    stream.flush();
-    stream.sync();
-    stream.clear();
-    // Sync both pointers to same position
-    stream.seekp(pos, dir);
     stream.seekg(pos, dir);
+    if (stream.fail()) {
+        stream.clear();
+    }
 #endif
 }
 
@@ -124,11 +138,12 @@ void SweepstoreFileHandle::writeSeek(std::streampos pos, std::ios::seekdir dir)
     // Same as readSeek for Unreal
     readSeek(pos, dir);
 #else
-    // Windows
+    // Windows - simplified to only seek write pointer
     auto& stream = getThreadStream();
-    stream.flush();
-    stream.sync();
     stream.seekp(pos, dir);
+    if (stream.fail()) {
+        stream.clear();
+    }
 #endif
 }
 
@@ -140,10 +155,6 @@ void SweepstoreFileHandle::readBytes(char* buffer, std::streamsize size) {
     // Windows
     auto& stream = getThreadStream();
     stream.read(buffer, size);
-    // Check for read errors on Windows
-    if (stream.fail() && !stream.eof()) {
-        stream.clear();
-    }
 #endif
 }
 
@@ -156,10 +167,6 @@ void SweepstoreFileHandle::writeBytes(const char* buffer, std::streamsize size)
     // Windows
     auto& stream = getThreadStream();
     stream.write(buffer, size);
-    // Check for write errors on Windows
-    if (stream.fail()) {
-        stream.clear();
-    }
 #endif
 }
 #endif // _WIN32 || WITH_UNREAL