support a nixide C API extension

nixide-sys/libnixide-c/nixide_api_main.cc

@@ -0,0 +1,30 @@
+#include <dlfcn.h>
+
+#include <nix_api_util.h>
+#include <nix_api_util_internal.h>
+
+#include <nix/main/plugin.hh>
+
+extern "C" {
+
+nix_err nixide_register_plugin(nix_c_context * context, char * plugin)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+    if (plugin == nullptr) {
+        // TODO: should this be `NIX_ERR_RECOVERABLE` or `NIX_ERR_UNKNOWN`?
+        return nix_set_err_msg(context, NIX_ERR_RECOVERABLE, "Plugin is null");
+    }
+
+    void * handle = dlopen("libnixmainc.so", RTLD_LAZY | RTLD_GLOBAL);
+    if (!handle) {
+        return nix_set_err_msg(context, NIX_ERR_UNKNOWN, dlerror());
+    }
+
+    void * sym_addr = dlsym(handle, "pluginSettings");
+
+    try {
+    }
+    NIXC_CATCH_ERRS
+}
+}