added CORS

source/database/databasepool.h

@@ -0,0 +1,61 @@
+#include <queue>
+#include <mutex>
+#include <condition_variable>
+#include <cassert>
+#include <memory>
+#include "database.hpp"
+
+class DatabasePool {
+public:
+    // Construct pool with path + size
+    DatabasePool(const std::string& path)
+        : db_path(path)
+    {
+        // Enable multithreaded SQLite
+        assert(sqlite3_config(SQLITE_CONFIG_MULTITHREAD) == SQLITE_OK);
+        assert(sqlite3_initialize() == SQLITE_OK);
+    }
+
+    bool init(size_t size){
+        try{
+            // Pre-create the pool
+            for (size_t i = 0; i < size; ++i) {
+                auto db = std::make_shared<decltype(make_database(db_path))>(make_database(db_path));
+                db->sync_schema();
+                pool.push(db);
+            }
+            // init the database
+            auto db = acquire();
+            release(db);
+            return true;
+        }
+        catch (...) {
+            return false;
+        }
+    }
+
+    // Acquire a database connection from the pool
+    std::shared_ptr<decltype(make_database(std::string{}))> acquire() {
+        std::unique_lock<std::mutex> lock(mutex);
+        cv.wait(lock, [&]{ return !pool.empty(); });
+        auto db = pool.front();
+        pool.pop();
+        return db;
+    }
+
+    // Return a connection to the pool
+    void release(std::shared_ptr<decltype(make_database(std::string{}))> db) {
+        std::unique_lock<std::mutex> lock(mutex);
+        pool.push(db);
+        lock.unlock();
+        cv.notify_one();
+    }
+
+private:
+    std::queue<std::shared_ptr<decltype(make_database(std::string{}))>> pool;
+    std::mutex mutex;
+    std::condition_variable cv;
+    const std::string db_path;
+};
+
+extern std::unique_ptr<DatabasePool> dbpool;