Fixed windows deadlocks, performance is shit tho

cpp/src/Private/sweepstore/header.cpp

@@ -165,7 +165,8 @@ void SweepstoreConcurrencyHeader::initialise(int concurrentWorkers) {
 void SweepstoreWorkerTicket::write(SweepstoreWorkerTicketSnapshot &snapshot) {
     RandomAccessMemory buffer;
 
-    uint64_t offset = getOffset();
+    SweepstoreFileLock lock(file.getPath(), 0, 0, SweepstoreFileLock::Mode::Exclusive);
+    SweepstoreFileLock::Scoped scopedLock(lock);
 
     buffer.setPositionSync(0);
     buffer.writeIntSync(snapshot.identifier, 4);
@@ -187,20 +188,23 @@ void SweepstoreWorkerTicket::write(SweepstoreWorkerTicketSnapshot &snapshot) {
     char* dataPtr = reinterpret_cast<char*>(data.data());
 
     // Write to file
-    file.writeSeek(offset);
+    file.writeSeek(getOffset());
     file.writeBytes(dataPtr, data.size());
     file.flush();
 }
 
 bool SweepstoreWorkerTicket::writable() {
-    return true;
+    SweepstoreFileLock lock(file.getPath(), 0, 0, SweepstoreFileLock::Mode::Exclusive);
+    return lock.isLocked() == false;
 }
 
 SweepstoreWorkerTicketSnapshot SweepstoreWorkerTicket::snapshot() {
-    uint64_t offset = getOffset();
-    file.readSeek(offset);
+    SweepstoreFileLock lock(file.getPath(), 0, 0, SweepstoreFileLock::Mode::Shared);
+    lock.lock();
+    file.readSeek(getOffset());
     std::unique_ptr<char[]> buffer(new char[TICKET_SIZE]);
     file.readBytes(buffer.get(), TICKET_SIZE);
+    lock.unlock();
     RandomAccessMemory ram(reinterpret_cast<uint8_t*>(buffer.get()), TICKET_SIZE);
 
     SweepstoreWorkerTicketSnapshot snapshot;

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