Start on rpc, open existing instances ui when trying to launch gsr-ui a second time

include/Rpc.hpp

@@ -0,0 +1,34 @@
+#pragma once
+
+#include <stddef.h>
+#include <functional>
+#include <unordered_map>
+#include <string>
+
+typedef struct _IO_FILE FILE;
+
+namespace gsr {
+    using RpcCallback = std::function<void(const std::string &name)>;
+
+    class Rpc {
+    public:
+        Rpc() = default;
+        Rpc(const Rpc&) = delete;
+        Rpc& operator=(const Rpc&) = delete;
+        ~Rpc();
+
+        bool create(const char *name);
+        bool open(const char *name);
+        bool write(const char *str, size_t size);
+        void poll();
+
+        bool add_handler(const std::string &name, RpcCallback callback);
+    private:
+        bool open_filepath(const char *filepath);
+    private:
+        int fd = 0;
+        FILE *file = nullptr;
+        std::string fifo_filepath;
+        std::unordered_map<std::string, RpcCallback> handlers_by_name;
+    };
+}