Refactor concurrency handling and file operations for improved performance and thread safety

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

@@ -1,8 +1,9 @@
 #include "sweepstore/utils/file_handle.h"
 
-// Constructor
+// Constructor - just stores path and mode, actual stream is created per-thread
 SweepstoreFileHandle::SweepstoreFileHandle(const std::string& p, std::ios::openmode mode)
     : path(p)
+    , openMode(mode)
 #ifdef WITH_UNREAL
 {
     IPlatformFile& platformFile = FPlatformFileManager::Get().GetPlatformFile();
@@ -24,11 +25,30 @@ SweepstoreFileHandle::SweepstoreFileHandle(const std::string& p, std::ios::openm
     }
 }
 #else
-    , stream(std::make_unique<std::fstream>(p, mode))
 {
-    if (!stream->is_open()) {
-        throw std::runtime_error("Failed to open file: " + path);
+    // Thread-local streams created on demand in getThreadStream()
+}
+#endif
+
+#ifndef WITH_UNREAL
+// Get or create the fstream for this thread
+std::fstream& SweepstoreFileHandle::getThreadStream() {
+    auto it = streamCache.find(path);
+    if (it == streamCache.end() || !it->second || !it->second->is_open()) {
+        // Create new stream for this thread
+        auto stream = std::make_unique<std::fstream>(path, openMode);
+        if (!stream->is_open()) {
+            throw std::runtime_error("Failed to open file: " + path);
+        }
+        streamCache[path] = std::move(stream);
+        return *streamCache[path];
     }
+    return *it->second;
+}
+
+const std::fstream& SweepstoreFileHandle::getThreadStream() const {
+    // Use const_cast to reuse the non-const version
+    return const_cast<SweepstoreFileHandle*>(this)->getThreadStream();
 }
 #endif
 
@@ -37,7 +57,8 @@ bool SweepstoreFileHandle::isOpen() const {
 #ifdef WITH_UNREAL
     return unrealHandle != nullptr;
 #else
-    return stream && stream->is_open();
+    auto it = streamCache.find(path);
+    return it != streamCache.end() && it->second && it->second->is_open();
 #endif
 }
 
@@ -49,8 +70,10 @@ void SweepstoreFileHandle::close() {
         unrealHandle = nullptr;
     }
 #else
-    if (stream) {
-        stream->close();
+    // Close this thread's stream if it exists
+    auto it = streamCache.find(path);
+    if (it != streamCache.end() && it->second && it->second->is_open()) {
+        it->second->close();
     }
 #endif
 }
@@ -63,11 +86,10 @@ void SweepstoreFileHandle::flush() {
         unrealHandle->Flush();
     }
 #else
-    if (stream) {
-        stream->flush();
-        // On Windows, also sync to ensure data hits disk
-        stream->sync();
-    }
+    auto& stream = getThreadStream();
+    stream.flush();
+    // On Windows, also sync to ensure data hits disk
+    stream.sync();
 #endif
 }
 
@@ -85,13 +107,14 @@ void SweepstoreFileHandle::readSeek(std::streampos pos, std::ios::seekdir dir) {
     }
 #else
     // Windows
+    auto& stream = getThreadStream();
     // On Windows, flush and sync to disk, then invalidate buffers
-    stream->flush();
-    stream->sync();
-    stream->clear();
+    stream.flush();
+    stream.sync();
+    stream.clear();
     // Sync both pointers to same position
-    stream->seekp(pos, dir);
-    stream->seekg(pos, dir);
+    stream.seekp(pos, dir);
+    stream.seekg(pos, dir);
 #endif
 }
 
@@ -102,9 +125,10 @@ void SweepstoreFileHandle::writeSeek(std::streampos pos, std::ios::seekdir dir)
     readSeek(pos, dir);
 #else
     // Windows
-    stream->flush();
-    stream->sync();
-    stream->seekp(pos, dir);
+    auto& stream = getThreadStream();
+    stream.flush();
+    stream.sync();
+    stream.seekp(pos, dir);
 #endif
 }
 
@@ -114,10 +138,11 @@ void SweepstoreFileHandle::readBytes(char* buffer, std::streamsize size) {
     unrealHandle->Read(reinterpret_cast<uint8*>(buffer), size);
 #else
     // Windows
-    stream->read(buffer, size);
+    auto& stream = getThreadStream();
+    stream.read(buffer, size);
     // Check for read errors on Windows
-    if (stream->fail() && !stream->eof()) {
-        stream->clear();
+    if (stream.fail() && !stream.eof()) {
+        stream.clear();
     }
 #endif
 }
@@ -129,10 +154,11 @@ void SweepstoreFileHandle::writeBytes(const char* buffer, std::streamsize size)
     unrealHandle->Flush();  // Unreal requires explicit flush
 #else
     // Windows
-    stream->write(buffer, size);
+    auto& stream = getThreadStream();
+    stream.write(buffer, size);
     // Check for write errors on Windows
-    if (stream->fail()) {
-        stream->clear();
+    if (stream.fail()) {
+        stream.clear();
     }
 #endif
 }