From 4bace6f68165ca031ddad75d01122a25a2bafec2 Mon Sep 17 00:00:00 2001
From: ImBenji <benjamin.watt@imbenji.net>
Date: Thu, 4 Dec 2025 20:33:06 +0000
Subject: [PATCH] Add thread-local caches for file locks and handles in fd_pool

---
 cpp/CMakeLists.txt                            |  1 -
 .../Private/sweepstore/utils/file_lock.cpp    |  7 ++
 cpp/src/Public/sweepstore/sweepstore.h        |  2 +-
 cpp/src/Public/sweepstore/utils/file_lock.h   | 66 +++++++++++++++++++
 4 files changed, 74 insertions(+), 2 deletions(-)
 create mode 100644 cpp/src/Private/sweepstore/utils/file_lock.cpp

diff --git a/cpp/CMakeLists.txt b/cpp/CMakeLists.txt
index cbc396f..b660dab 100644
--- a/cpp/CMakeLists.txt
+++ b/cpp/CMakeLists.txt
@@ -20,7 +20,6 @@ add_executable(main
         src/Public/sweepstore/concurrency.h
         src/Private/sweepstore/concurrency.cpp
         src/Public/sweepstore/utils/file_lock.h
-        src/Private/sweepstore/utils/fd_pool.h
         src/Private/sweepstore/utils/fd_pool.cpp
         src/Public/sweepstore/utils/file_handle.h
         src/Private/sweepstore/utils/file_handle.cpp
diff --git a/cpp/src/Private/sweepstore/utils/file_lock.cpp b/cpp/src/Private/sweepstore/utils/file_lock.cpp
new file mode 100644
index 0000000..9096650
--- /dev/null
+++ b/cpp/src/Private/sweepstore/utils/file_lock.cpp
@@ -0,0 +1,7 @@
+#include "sweepstore/utils/file_lock.h"
+
+#ifdef _WIN32
+thread_local std::unordered_map<std::string, HANDLE> SweepstoreFileLock::handleCache;
+#else
+thread_local std::unordered_map<std::string, int> SweepstoreFileLock::fdCache;
+#endif
diff --git a/cpp/src/Public/sweepstore/sweepstore.h b/cpp/src/Public/sweepstore/sweepstore.h
index 7fc2253..1febfc9 100644
--- a/cpp/src/Public/sweepstore/sweepstore.h
+++ b/cpp/src/Public/sweepstore/sweepstore.h
@@ -57,7 +57,7 @@ public:
 
                 }
             );
-        };
+        }
     };
 
     Proxy operator[](const std::string& key) {
diff --git a/cpp/src/Public/sweepstore/utils/file_lock.h b/cpp/src/Public/sweepstore/utils/file_lock.h
index 2b49037..3e1a52e 100644
--- a/cpp/src/Public/sweepstore/utils/file_lock.h
+++ b/cpp/src/Public/sweepstore/utils/file_lock.h
@@ -25,6 +25,55 @@ private:
     Mode mode;
     bool locked = false;
 
+#ifdef _WIN32
+    // Thread-local HANDLE cache for Windows
+    static thread_local std::unordered_map<std::string, HANDLE> handleCache;
+
+    static HANDLE getOrOpenHandle(const std::string& path) {
+        auto it = handleCache.find(path);
+        if (it != handleCache.end()) {
+            return it->second;
+        }
+
+        HANDLE handle = CreateFileA(
+            path.c_str(),
+            GENERIC_READ | GENERIC_WRITE,
+            FILE_SHARE_READ | FILE_SHARE_WRITE,
+            NULL,
+            OPEN_EXISTING,
+            FILE_ATTRIBUTE_NORMAL,
+            NULL
+        );
+
+        if (handle == INVALID_HANDLE_VALUE) {
+            throw std::runtime_error("Failed to open file for locking: " + path);
+        }
+
+        handleCache[path] = handle;
+        return handle;
+    }
+
+    void acquire() {
+        HANDLE handle = getOrOpenHandle(filePath);
+        OVERLAPPED overlapped = {0};
+        DWORD flags = (mode == Mode::Exclusive) ? LOCKFILE_EXCLUSIVE_LOCK : 0;
+        flags |= LOCKFILE_FAIL_IMMEDIATELY;
+
+        if (!LockFileEx(handle, flags, 0, MAXDWORD, MAXDWORD, &overlapped)) {
+            throw std::runtime_error("Failed to acquire file lock");
+        }
+        locked = true;
+    }
+
+    void release() {
+        if (locked) {
+            HANDLE handle = getOrOpenHandle(filePath);
+            OVERLAPPED overlapped = {0};
+            UnlockFileEx(handle, 0, MAXDWORD, MAXDWORD, &overlapped);
+            locked = false;
+        }
+    }
+#else
     // Thread-local FD cache - each thread has its own FD per file
     static thread_local std::unordered_map<std::string, int> fdCache;
 
@@ -60,6 +109,7 @@ private:
             locked = false;
         }
     }
+#endif
 
 public:
     // Constructor accepts offset/length for API compatibility (unused with flock)
@@ -82,6 +132,21 @@ public:
 
     // Check if file is currently locked (non-blocking test)
     bool isLocked() const {
+#ifdef _WIN32
+        HANDLE handle = getOrOpenHandle(filePath);
+        OVERLAPPED overlapped = {0};
+        DWORD flags = (mode == Mode::Exclusive) ? LOCKFILE_EXCLUSIVE_LOCK : 0;
+        flags |= LOCKFILE_FAIL_IMMEDIATELY;
+
+        // Try non-blocking lock
+        if (!LockFileEx(handle, flags, 0, MAXDWORD, MAXDWORD, &overlapped)) {
+            return true; // Already locked
+        }
+
+        // Got the lock, release immediately
+        UnlockFileEx(handle, 0, MAXDWORD, MAXDWORD, &overlapped);
+        return false;
+#else
         int fd = getOrOpenFD(filePath);
         int operation = (mode == Mode::Exclusive) ? LOCK_EX : LOCK_SH;
 
@@ -93,6 +158,7 @@ public:
         // Got the lock, release immediately
         flock(fd, LOCK_UN);
         return false;
+#endif
     }
 
     // RAII helper for scoped locking