kapi: rework text device interface

5 files changed, 65 insertions, 23 deletions

diff --git a/kapi/CMakeLists.txt b/kapi/CMakeLists.txt
index 3a15fee..14244bc 100644
--- a/kapi/CMakeLists.txt
+++ b/kapi/CMakeLists.txt
@@ -5,12 +5,13 @@ target_sources("kapi" PUBLIC
     FILE_SET HEADERS
     BASE_DIRS "include"
     FILES
-    "include/kapi/io.hpp"
+    "include/kapi/cio.hpp"
     "include/kapi/memory.hpp"
     "include/kapi/system.hpp"
 )
 
 target_sources("kapi" PRIVATE
+    "src/cio.cpp"
     "src/system.cpp"
 )
 
diff --git a/kapi/include/kapi/cio.hpp b/kapi/include/kapi/cio.hpp
new file mode 100644
index 0000000..6b93638
--- /dev/null
+++ b/kapi/include/kapi/cio.hpp
@@ -0,0 +1,29 @@
+#ifndef TEACHOS_KAPI_IO_HPP
+#define TEACHOS_KAPI_IO_HPP
+
+#include <optional>
+#include <string_view>
+
+namespace teachos::cio
+{
+  struct output_device
+  {
+    auto virtual write(std::string_view text [[maybe_unused]]) -> void {}
+    auto virtual writeln(std::string_view text [[maybe_unused]]) -> void {}
+
+    auto virtual write_error(std::string_view text [[maybe_unused]]) -> void {}
+    auto virtual writeln_error(std::string_view text [[maybe_unused]]) -> void {}
+  };
+
+  auto init() -> void;
+
+  auto set_output_device(output_device & device) -> std::optional<output_device *>;
+
+  auto print(std::string_view text) -> void;
+  auto println(std::string_view text) -> void;
+
+  auto print_error(std::string_view text) -> void;
+  auto println_error(std::string_view text) -> void;
+}  // namespace teachos::cio
+
+#endif
diff --git a/kapi/include/kapi/io.hpp b/kapi/include/kapi/io.hpp
deleted file mode 100644
index 764738f..0000000
--- a/kapi/include/kapi/io.hpp
+++ /dev/null
@@ -1,17 +0,0 @@
-#ifndef TEACHOS_KAPI_IO_HPP
-#define TEACHOS_KAPI_IO_HPP
-
-#include <string_view>
-
-namespace teachos::io
-{
-  auto init() -> void;
-
-  auto print(std::string_view text) -> void;
-  auto println(std::string_view text) -> void;
-
-  auto print_error(std::string_view text) -> void;
-  auto println_error(std::string_view text) -> void;
-}  // namespace teachos::io
-
-#endif
diff --git a/kapi/src/cio.cpp b/kapi/src/cio.cpp
new file mode 100644
index 0000000..aa26d49
--- /dev/null
+++ b/kapi/src/cio.cpp
@@ -0,0 +1,29 @@
+#include "kapi/cio.hpp"
+
+#include <optional>
+#include <utility>
+
+namespace teachos::cio
+{
+  auto constinit null_device = output_device{};
+
+  auto constinit active_device = &null_device;
+
+  auto set_output_device(output_device & device) -> std::optional<output_device *>
+  {
+    if (&device == active_device)
+    {
+      return {};
+    }
+    return std::exchange(active_device, &device);
+  }
+
+  auto print(std::string_view text) -> void { active_device->write(text); }
+
+  auto println(std::string_view text) -> void { active_device->writeln(text); }
+
+  auto print_error(std::string_view text) -> void { active_device->write_error(text); }
+
+  auto println_error(std::string_view text) -> void { active_device->writeln_error(text); }
+
+}  // namespace teachos::cio
\ No newline at end of file
diff --git a/kapi/src/system.cpp b/kapi/src/system.cpp
index c3b1c5e..041404e 100644
--- a/kapi/src/system.cpp
+++ b/kapi/src/system.cpp
@@ -1,16 +1,16 @@
 #include "kapi/system.hpp"
 
-#include "kapi/io.hpp"
+#include "kapi/cio.hpp"
 
 namespace teachos::system
 {
 
   auto panic(std::string_view message, std::source_location location) -> void
   {
-    io::println_error("!!!Kernel Panic!!! ");
-    io::println_error(message);
-    io::println_error(location.file_name());
-    io::println_error(location.function_name());
+    cio::println_error("!!!Kernel Panic!!! ");
+    cio::println_error(message);
+    cio::println_error(location.file_name());
+    cio::println_error(location.function_name());
 
     halt();
   }