kapi: rework text device interface

11 files changed, 148 insertions, 145 deletions

diff --git a/arch/x86_64/CMakeLists.txt b/arch/x86_64/CMakeLists.txt
index c585cbf..e8b5162 100644
--- a/arch/x86_64/CMakeLists.txt
+++ b/arch/x86_64/CMakeLists.txt
@@ -12,7 +12,7 @@ target_link_libraries("x86_64" PUBLIC
 
 target_sources("x86_64" PRIVATE
     # api::kapi implementation
-    "kapi/io.cpp"
+    "kapi/cio.cpp"
     "kapi/memory.cpp"
     "kapi/system.cpp"
 
diff --git a/arch/x86_64/include/x86_64/vga/text.hpp b/arch/x86_64/include/x86_64/vga/text.hpp
index 267eae9..f8e6f1b 100644
--- a/arch/x86_64/include/x86_64/vga/text.hpp
+++ b/arch/x86_64/include/x86_64/vga/text.hpp
@@ -1,9 +1,10 @@
 #ifndef TEACHOS_X86_64_VIDEO_VGA_TEXT_HPP
 #define TEACHOS_X86_64_VIDEO_VGA_TEXT_HPP
 
+#include "kapi/cio.hpp"
+
 #include <cstdint>
 #include <string_view>
-#include <type_traits>
 
 namespace teachos::x86_64::vga::text
 {
@@ -89,84 +90,57 @@ namespace teachos::x86_64::vga::text
         attribute{color::gray, foreground_flag::intense, color::red, background_flag::none};
   }  // namespace common_attributes
 
-  /**
-   * @brief Clear the VGA text mode buffer.
-   *
-   * @note This function also resets the text mode buffer pointer.
-   *
-   * @param attribute The attribute to "clear" the screen with.
-   */
-  auto clear(attribute attribute = common_attributes::gray_on_black) -> void;
-
-  /**
-   * @brief Enable or disable the VGA text mode cursor.
-   *
-   * @param enabled Whether or not to enable the cursors.
-   */
-  auto cursor(bool enabled) -> void;
+  struct device final : teachos::cio::output_device
+  {
+    /**
+     * @brief Clear the VGA text mode buffer.
+     *
+     * @note This function also resets the text mode buffer pointer.
+     *
+     * @param attribute The attribute to "clear" the screen with.
+     */
+    auto clear(attribute attribute = common_attributes::gray_on_black) -> void;
 
-  /**
-   * @brief Move the cursor to a new line, scrolling the buffer if necessary.
-   */
-  auto newline() -> void;
+    /**
+     * @brief Enable or disable the VGA text mode cursor.
+     *
+     * @param enabled Whether or not to enable the cursors.
+     */
+    auto cursor(bool enabled) -> void;
 
-  /**
-   * @brief Write a string of code points to the VGA text buffer.
-   *
-   * @note This function also updates the text mode buffer pointer.
-   *
-   * @param code_points A string of (8-bit) code points to write to the VGA text mode buffer.
-   * @param attribute The attribute to apply to the written sequence of code points.
-   * @see vga::text::attribute
-   */
-  auto write(std::string_view code_points, attribute attribute) -> void;
+    auto write(std::string_view text) -> void override { write(text, common_attributes::green_on_black); }
+    auto writeln(std::string_view text) -> void override { writeln(text, common_attributes::green_on_black); }
+    auto write_error(std::string_view text) -> void override { write(text, common_attributes::red_on_black); }
+    auto writeln_error(std::string_view text) -> void override { writeln(text, common_attributes::red_on_black); }
 
-  /**
-   * @brief Write a single character to the VGA text buffer.
-   *
-   * @note This function also updates the text mode buffer pointer.
-   *
-   * @param code_point A code point to write to the VGA text mode buffer.
-   * @param attribute The attribute to apply to the written sequence of code points.
-   * @see vga::text::attribute
-   */
-  auto write_char(char code_point, attribute attribute) -> void;
+  private:
+    /**
+     * @brief Move the cursor to a new line, scrolling the buffer if necessary.
+     */
+    auto newline() -> void;
 
-  template<typename T>
-  concept Integral = std::is_integral_v<T>;
+    /**
+     * @brief Write a string of code points to the VGA text buffer.
+     *
+     * @note This function also updates the text mode buffer pointer.
+     *
+     * @param code_points A string of (8-bit) code points to write to the VGA text mode buffer.
+     * @param attribute The attribute to apply to the written sequence of code points.
+     * @see vga::text::attribute
+     */
+    auto write(std::string_view code_points, attribute attribute) -> void;
 
-  /**
-   * @brief Write a integral value to the VGA text buffer.
-   *
-   * @note This function also updates the text mode buffer pointer.
-   *
-   * @param value A integral value to write to the VGA text mode buffer.
-   * @param attribute The attribute to apply to the written sequence of code points.
-   * @see vga::text::attribute
-   */
-  template<Integral T>
-  auto write_number(T value, attribute attribute) -> void
-  {
-    T current_value = value;
-    T divisor = 1;
-
-    while (current_value > 9)
-    {
-      divisor *= 10;
-      current_value = current_value / 10;
-    }
-
-    current_value = value;
-    while (divisor > 0)
-    {
-      uint8_t quotient = current_value / divisor;
-      char ascii_digit = quotient + '0';
-
-      write_char(ascii_digit, attribute);
-      current_value %= divisor;
-      divisor /= 10;
-    }
-  }
+    /**
+     * @brief Write a string of code points followed by a newline to the VGA text buffer.
+     *
+     * @note This function also updates the text mode buffer pointer.
+     *
+     * @param code_points A string of (8-bit) code points to write to the VGA text mode buffer.
+     * @param attribute The attribute to apply to the written sequence of code points.
+     * @see vga::text::attribute
+     */
+    auto writeln(std::string_view code_points, attribute attribute) -> void;
+  };
 
 }  // namespace teachos::x86_64::vga::text
 
diff --git a/arch/x86_64/kapi/cio.cpp b/arch/x86_64/kapi/cio.cpp
new file mode 100644
index 0000000..ac3ae39
--- /dev/null
+++ b/arch/x86_64/kapi/cio.cpp
@@ -0,0 +1,16 @@
+#include "kapi/cio.hpp"
+
+#include "x86_64/vga/text.hpp"
+
+namespace teachos::cio
+{
+
+  auto static constinit vga_device = std::optional<x86_64::vga::text::device>{};
+
+  auto init() -> void
+  {
+    vga_device.emplace();
+    set_output_device(*vga_device);
+  }
+
+}  // namespace teachos::cio
diff --git a/arch/x86_64/kapi/io.cpp b/arch/x86_64/kapi/io.cpp
deleted file mode 100644
index eab6473..0000000
--- a/arch/x86_64/kapi/io.cpp
+++ /dev/null
@@ -1,36 +0,0 @@
-#include "kapi/io.hpp"
-
-#include "x86_64/vga/text.hpp"
-
-namespace teachos::io
-{
-
-  auto init() -> void
-  {
-    x86_64::vga::text::clear();
-    x86_64::vga::text::cursor(false);
-  }
-
-  auto print(std::string_view text) -> void
-  {
-    x86_64::vga::text::write(text, x86_64::vga::text::common_attributes::green_on_black);
-  }
-
-  auto println(std::string_view text) -> void
-  {
-    x86_64::vga::text::write(text, x86_64::vga::text::common_attributes::green_on_black);
-    x86_64::vga::text::newline();
-  }
-
-  auto print_error(std::string_view text) -> void
-  {
-    x86_64::vga::text::write(text, x86_64::vga::text::common_attributes::red_on_black);
-  }
-
-  auto println_error(std::string_view text) -> void
-  {
-    x86_64::vga::text::write(text, x86_64::vga::text::common_attributes::red_on_black);
-    x86_64::vga::text::newline();
-  }
-
-}  // namespace teachos::io
diff --git a/arch/x86_64/src/vga/text.cpp b/arch/x86_64/src/vga/text.cpp
index 5c94b84..af089fd 100644
--- a/arch/x86_64/src/vga/text.cpp
+++ b/arch/x86_64/src/vga/text.cpp
@@ -13,19 +13,24 @@ namespace teachos::x86_64::vga::text
 {
   namespace
   {
-    auto buffer_offset = std::ptrdiff_t{};
+    auto constinit buffer_offset = std::ptrdiff_t{};
 
     auto constexpr DEFAULT_TEXT_BUFFER_WIDTH = 80U;
     auto constexpr DEFAULT_TEXT_BUFFER_HEIGHT = 25U;
+
+    auto write_char(char code_point, attribute attribute) -> void
+    {
+      vga_buffer_pointer[buffer_offset++] = std::pair{code_point, std::bit_cast<std::byte>(attribute)};
+    };
   }  // namespace
 
-  auto clear(attribute attribute) -> void
+  auto device::clear(attribute attribute) -> void
   {
     buffer_offset = 0;
     std::ranges::fill_n(vga_buffer_pointer.get(), 2000, std::pair{' ', std::bit_cast<std::byte>(attribute)});
   }
 
-  auto cursor(bool enabled) -> void
+  auto device::cursor(bool enabled) -> void
   {
     auto cursor_disable_byte = std::byte{!enabled} << 5;
 
@@ -33,7 +38,7 @@ namespace teachos::x86_64::vga::text
     crtc::data::write(crtc::data::read() | cursor_disable_byte);
   }
 
-  auto newline() -> void
+  auto device::newline() -> void
   {
     auto current_line = buffer_offset / DEFAULT_TEXT_BUFFER_WIDTH;
     auto next_line = current_line + 1;
@@ -51,13 +56,15 @@ namespace teachos::x86_64::vga::text
     }
   }
 
-  auto write_char(char code_point, attribute attribute) -> void
+  auto device::write(std::string_view code_points, attribute attribute) -> void
   {
-    vga_buffer_pointer[buffer_offset++] = std::pair{code_point, std::bit_cast<std::byte>(attribute)};
-  };
+    std::ranges::for_each(code_points, [&](auto code_point) { write_char(code_point, attribute); });
+  }
 
-  auto write(std::string_view code_points, attribute attribute) -> void
+  auto device::writeln(std::string_view code_points, attribute attribute) -> void
   {
     std::ranges::for_each(code_points, [&](auto code_point) { write_char(code_point, attribute); });
+    newline();
   }
+
 }  // namespace teachos::x86_64::vga::text
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();
   }
diff --git a/src/main.cpp b/src/main.cpp
index d6199d0..120e7e0 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,11 +1,11 @@
-#include "kapi/io.hpp"
+#include "kapi/cio.hpp"
 #include "kapi/memory.hpp"
 #include "kapi/system.hpp"
 
 auto main() -> int
 {
-  teachos::io::init();
-  teachos::io::println("[OS] IO subsystem initialized.");
+  teachos::cio::init();
+  teachos::cio::println("[OS] IO subsystem initialized.");
 
   teachos::memory::init();