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module;
#include <algorithm>
#include <termios.h>
#include <unistd.h>
#include <cerrno>
#include <system_error>
#include <utility>
export module ttwhy.terminal:scoped_attributes;
namespace ttwhy::terminal
{
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");
}
}
//! RAII wrapper storing the current terminal attributes and restoring them on destruction.
export struct scoped_attributes
{
//! Construct and capture the current attributes of a terminal file descriptor.
//!
//! @param file_descriptor The file descriptor of the terminal.
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.
//!
//! @return True if ICANON is set, false otherwise.
[[nodiscard]] auto canonical_mode() const noexcept -> bool
{
return get_line_discipline_flag(m_file_descriptor, ICANON);
}
//! Set whether canonical mode is active or not on an lvalue reference.
//!
//! @param enabled True to enable canonical mode, false to disable.
//! @return Reference to this object for chaining.
auto canonical_mode(bool enabled) & -> scoped_attributes &
{
set_line_discipline_flag(m_file_descriptor, ICANON, enabled);
return *this;
}
//! Set whether canonical mode is active or not on an rvalue.
//!
//! @param enabled True to enable canonical mode, false to disable.
//! @return The modified scoped_attributes object by value.
auto canonical_mode(bool enabled) && -> scoped_attributes
{
set_line_discipline_flag(m_file_descriptor, ICANON, enabled);
return std::move(*this);
}
//! Check if echo is currently active.
//!
//! @return True if ECHO is set, false otherwise.
[[nodiscard]] auto echo() const noexcept -> bool
{
return get_line_discipline_flag(m_file_descriptor, ECHO);
}
//! Set whether echo is active or not on an lvalue reference.
//!
//! @param enabled True to enable echo, false to disable.
//! @return Reference to this object for chaining.
auto echo(bool enabled) & -> scoped_attributes &
{
set_line_discipline_flag(m_file_descriptor, ECHO, enabled);
return *this;
}
//! Set whether echo is active or not on an rvalue.
//!
//! @param enabled True to enable echo, false to disable.
//! @return The modified scoped_attributes object by value.
auto echo(bool enabled) && -> scoped_attributes
{
set_line_discipline_flag(m_file_descriptor, ECHO, enabled);
return std::move(*this);
}
//! Capture the currently active terminal mode and mark the attributes as suspended.
//!
//! Must be called before the terminal mode is changed while the process is being stopped.
auto suspend() & -> scoped_attributes &
{
if (m_file_descriptor > 0)
{
m_suspended = true;
m_suspended_canonical = canonical_mode();
m_suspended_echo = echo();
}
return *this;
}
//! Restore the terminal mode captured before suspension.
auto resume() & -> scoped_attributes &
{
if (m_suspended)
{
canonical_mode(m_suspended_canonical);
echo(m_suspended_echo);
m_suspended = false;
}
return *this;
}
private:
int m_file_descriptor;
termios m_attributes;
bool m_suspended{false};
bool m_suspended_canonical{false};
bool m_suspended_echo{false};
};
} // namespace ttwhy::terminal
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