1 files changed, 36 insertions, 0 deletions
diff --git a/kernel/kapi/cio.cpp b/kernel/kapi/cio.cpp
new file mode 100644
index 0000000..d447a6a
--- /dev/null
+++ b/kernel/kapi/cio.cpp
@@ -0,0 +1,36 @@
+#include "kapi/cio.hpp"
+
+#include <optional>
+#include <string_view>
+#include <utility>
+
+namespace kapi::cio
+{
+  namespace
+  {
+    struct null_device final : public output_device
+    {
+      null_device static instance;
+      auto write(output_stream, std::string_view) -> void override {}
+    };
+
+    constinit null_device null_device::instance;
+  }  // namespace
+
+  constinit auto static active_device = static_cast<output_device *>(&null_device::instance);
+
+  auto set_output_device(output_device & device) -> std::optional<output_device *>
+  {
+    if (&device == active_device)
+    {
+      return {};
+    }
+    return std::exchange(active_device, &device);
+  }
+
+  auto write(output_stream stream, std::string_view text) -> void
+  {
+    active_device->write(stream, text);
+  }
+
+}  // namespace kapi::cio