lib/io: refactor I/O module

1 files changed, 135 insertions, 0 deletions

diff --git a/ttwhy/io/scoped_attributes.cppm b/ttwhy/io/scoped_attributes.cppm
new file mode 100644
index 0000000..5e42e39
--- /dev/null
+++ b/ttwhy/io/scoped_attributes.cppm
@@ -0,0 +1,135 @@
+module;
+
+#include <termios.h>
+#include <unistd.h>
+
+#include <cerrno>
+#include <system_error>
+#include <utility>
+
+export module ttwhy.io:scoped_attributes;
+
+namespace ttwhy::io
+{
+
+  auto static read_attributes(int file_descriptor) -> termios
+  {
+    auto active_attributes = termios{};
+    if (::tcgetattr(file_descriptor, &active_attributes))
+    {
+      throw std::system_error(errno, std::system_category(), "failed to read termios attributes");
+    }
+    return active_attributes;
+  }
+
+  auto static get_line_discipline_flag(int file_descriptor, int flag) -> bool
+  {
+    auto active_attributes = read_attributes(file_descriptor);
+    return active_attributes.c_lflag & flag;
+  }
+
+  auto static set_line_discipline_flag(int file_descriptor, int flag, bool enabled) -> void
+  {
+    auto active_attributes = read_attributes(file_descriptor);
+
+    if ((active_attributes.c_lflag & flag) == enabled)
+    {
+      return;
+    }
+
+    if (enabled)
+    {
+      active_attributes.c_lflag = active_attributes.c_lflag | flag;
+    }
+    else
+    {
+      active_attributes.c_lflag = active_attributes.c_lflag & ~flag;
+    }
+
+    if (::tcsetattr(file_descriptor, TCSANOW, &active_attributes))
+    {
+      throw std::system_error(errno, std::system_category(), "failed to write termios attributes");
+    }
+  }
+
+  //! Store the current TC attributes and restore them on destruction.
+  export struct scoped_attributes
+  {
+    explicit scoped_attributes(int file_descriptor)
+        : m_file_descriptor{-1}
+        , m_attributes{}
+    {
+      if (isatty(file_descriptor))
+      {
+        m_file_descriptor = dup(file_descriptor);
+        m_attributes = read_attributes(m_file_descriptor);
+      }
+    }
+
+    scoped_attributes(scoped_attributes const &) = delete;
+
+    scoped_attributes(scoped_attributes && other)
+        : m_file_descriptor{std::exchange(other.m_file_descriptor, -1)}
+        , m_attributes{std::move(other.m_attributes)}
+    {}
+
+    ~scoped_attributes()
+    {
+      if (m_file_descriptor > 0)
+      {
+        ::tcsetattr(m_file_descriptor, TCSANOW, &m_attributes);
+        ::close(m_file_descriptor);
+      }
+    }
+
+    auto operator=(scoped_attributes const &) -> scoped_attributes & = delete;
+
+    auto operator=(scoped_attributes && other) -> scoped_attributes &
+    {
+      std::ranges::swap(m_file_descriptor, other.m_file_descriptor);
+      std::ranges::swap(m_attributes, other.m_attributes);
+      return *this;
+    }
+
+    //! Check if canonical mode is currently active
+    [[nodiscard]] auto canonical_mode() const noexcept -> bool
+    {
+      return get_line_discipline_flag(m_file_descriptor, ICANON);
+    }
+
+    //! Set whether canonical mode is active or not.
+    auto canonical_mode(bool enabled) & -> scoped_attributes &
+    {
+      set_line_discipline_flag(m_file_descriptor, ICANON, enabled);
+      return *this;
+    }
+
+    auto canonical_mode(bool enabled) && -> scoped_attributes
+    {
+      set_line_discipline_flag(m_file_descriptor, ICANON, enabled);
+      return std::move(*this);
+    }
+
+    [[nodiscard]] auto echo() const noexcept -> bool
+    {
+      return get_line_discipline_flag(m_file_descriptor, ECHO);
+    }
+
+    auto echo(bool enabled) & -> scoped_attributes &
+    {
+      set_line_discipline_flag(m_file_descriptor, ECHO, enabled);
+      return *this;
+    }
+
+    auto echo(bool enabled) && -> scoped_attributes
+    {
+      set_line_discipline_flag(m_file_descriptor, ECHO, enabled);
+      return std::move(*this);
+    }
+
+  private:
+    int m_file_descriptor;
+    termios m_attributes;
+  };
+
+}  // namespace ttwhy::io