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Try once again to fix stdin handling on Windows
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On Windows, there is apparently no unified non-blocking API to wait for
input on stdin.  Thus, call the blocking API from a worker thread.

Tested the following use cases:

* Starting from the Windows console
* Starting from Windows Explorer (should be the same, but who knows)
* Starting from the client (I guess stdin is a named pipe in this case)
* Starting from the MSYS console (no idea what it uses, maybe a file)

The thread is only used on Windows, no reason for the extra overhead to
propagate to sane OSes.

Closes longturn#850.
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@lmoureaux
lmoureaux committed Mar 1, 2022
1 parent 796001c commit bcfa146
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Showing 5 changed files with 243 additions and 33 deletions.
2 changes: 2 additions & 0 deletions server/CMakeLists.txt
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Original file line number Diff line number Diff line change
@@ -1,3 +1,5 @@
set(CMAKE_AUTOMOC true)

# Generate the packet handling code
add_custom_command(
OUTPUT
Expand Down
206 changes: 177 additions & 29 deletions server/server.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -30,10 +30,7 @@

// Stuff to wait for input on stdin.
#ifdef Q_OS_WIN
#include <QtCore/QWinEventNotifier>
#include <array>
#include <io.h>
#include <windows.h>
#include <QMutexLocker>
#else
#include <QtCore/QSocketNotifier>
#endif
Expand Down Expand Up @@ -80,6 +77,7 @@ static const char *HISTORY_FILENAME = "freeciv-server_history";
static const int HISTORY_LENGTH = 100;

namespace {
#ifndef Q_OS_WIN
/**
Readline callback for input.
*/
Expand All @@ -99,6 +97,7 @@ void handle_readline_input_callback(char *line)
delete[] line_internal;
free(line);
}
#endif // !Q_OS_WIN

/**
Initialize server specific functions.
Expand Down Expand Up @@ -214,27 +213,80 @@ std::pair<QTcpServer *, bool> srv_prepare()

} // anonymous namespace

#ifdef Q_OS_WIN
/**
* Constructor.
*/
detail::async_readline_wrapper::async_readline_wrapper(bool interactive,
QObject *parent)
: QThread(parent), m_interactive(interactive)
{
}

/**
* Blocks until a line of input can be read from stdin, then emits
* `line_available`.
*/
void detail::async_readline_wrapper::wait_for_input()
{
// Loop until we get a non-trivial line
QString line;
while (line.isEmpty()) {
if (m_interactive) {
char *buffer = readline("> ");
if (buffer == nullptr) {
break;
}

if (buffer && buffer[0] != '\0') {
add_history(buffer);
}

line = QString::fromLocal8Bit(buffer);
} else {
QFile f;
f.open(stdin, QIODevice::ReadOnly);
line = QString::fromLocal8Bit(f.readLine());
}
}
emit line_available(line);
}

/// Synchronizes stdin and network handling
QRecursiveMutex server::s_stdin_mutex = QRecursiveMutex();
#endif // Q_OS_WIN

/**
Creates a server. It starts working as soon as there is an event loop.
*/
server::server()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

// Are we running an interactive session?
#ifdef Q_OS_WIN
// isatty and fileno are deprecated on Windows
m_interactive = _isatty(_fileno(stdin));
#else
m_interactive = isatty(fileno(stdin));
#endif

// Get notifications when there's some input on stdin. This is OS-dependent
// and Qt doesn't have a wrapper. Maybe it should be split to a separate
// class.
#ifdef Q_OS_WIN
{
auto handle = CreateFileA("CONIN$", GENERIC_READ, FILE_SHARE_READ,
nullptr, OPEN_EXISTING, 0, nullptr);
if (handle == INVALID_HANDLE_VALUE) {
// TRANS: Don't translate HANDLE and CONIN$
qCritical(_("Failed to get a HANDLE for CONIN$"));
} else {
auto notifier = new QWinEventNotifier(handle, this);
connect(notifier, &QWinEventNotifier::activated, this,
&server::input_on_stdin);
m_stdin_notifier = notifier;
}
// Spawn a thread from where we can afford to do blocking calls
auto wrapper = new detail::async_readline_wrapper(m_interactive);
wrapper->moveToThread(wrapper);
connect(wrapper, &detail::async_readline_wrapper::line_available, this,
&server::input_on_stdin);
connect(this, &server::input_requested, wrapper,
&detail::async_readline_wrapper::wait_for_input);
wrapper->start();
m_stdin_notifier = wrapper;
}
#else
{
Expand All @@ -247,14 +299,6 @@ server::server()
}
#endif

// Are we running an interactive session?
#ifdef Q_OS_WIN
// isatty and fileno are deprecated on Windows
m_interactive = _isatty(_fileno(stdin));
#else
m_interactive = isatty(fileno(stdin));
#endif

// Now init the old C API
fc_interface_init_server();
bool success;
Expand Down Expand Up @@ -286,20 +330,29 @@ server::server()
connect(m_pulse_timer, &QTimer::timeout, this, &server::pulse);

m_ready = true;

#ifdef Q_OS_WIN
// Ask the stdin worker thread to start looking at imput.
emit input_requested();
#endif // Q_OS_WIN
}

/**
Shut down a server.
*/
server::~server()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

#ifdef Q_OS_WIN
{
// Close the handle to stdin
auto notifier = dynamic_cast<QWinEventNotifier *>(m_stdin_notifier);
auto notifier =
qobject_cast<detail::async_readline_wrapper *>(m_stdin_notifier);
if (notifier) {
notifier->setEnabled(false);
(void) CloseHandle(notifier->handle());
notifier->wait();
delete notifier;
}
}
#endif // Q_OS_WIN
Expand Down Expand Up @@ -342,8 +395,12 @@ void server::init_interactive()

// Initialize readline
rl_initialize();
#ifdef Q_OS_WIN
rl_attempted_completion_function = synchronized_completion;
#else
rl_callback_handler_install((char *) "> ", handle_readline_input_callback);
rl_attempted_completion_function = freeciv_completion;
#endif
}

/**
Expand All @@ -358,6 +415,10 @@ bool server::is_ready() const { return m_ready; }
*/
void server::accept_connections()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

// There may be several connections available.
while (m_tcp_server->hasPendingConnections()) {
auto *socket = m_tcp_server->nextPendingConnection();
Expand Down Expand Up @@ -437,6 +498,10 @@ void server::accept_connections()
*/
void server::send_pings()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

// Pinging around for statistics
if (time(NULL) > (game.server.last_ping + game.server.pingtime)) {
conn_list_iterate(game.all_connections, pconn)
Expand Down Expand Up @@ -471,6 +536,10 @@ void server::send_pings()
*/
void server::error_on_socket()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

// Get the socket
auto *socket = dynamic_cast<QTcpSocket *>(sender());
if (socket == nullptr) {
Expand All @@ -496,6 +565,10 @@ void server::error_on_socket()
*/
void server::input_on_socket()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

// Get the socket
auto *socket = dynamic_cast<QTcpSocket *>(sender());
if (socket == nullptr) {
Expand Down Expand Up @@ -525,18 +598,55 @@ void server::input_on_socket()
update_game_state();
}

#ifdef Q_OS_WIN

/**
* Called when a line was read from stdin.
*/
void server::input_on_stdin(const QString &line)
{
QMutexLocker lock(&s_stdin_mutex);

auto buffer = line.toUtf8();
handle_stdin_input(NULL, buffer.data());
if (should_quit()) {
// Stop the worker thread
auto notifier =
qobject_cast<detail::async_readline_wrapper *>(m_stdin_notifier);
if (notifier) {
notifier->quit();
}
} else {
// Ask the notifier to block until it reads the next line
emit input_requested();
}

update_game_state();
}

/**
* Synchronized wrapper around @ref freeciv_completion.
*/
char **server::synchronized_completion(const char *text, int start, int end)
{
QMutexLocker lock(&s_stdin_mutex);
return freeciv_completion(text, start, end);
}

#else // !Q_OS_WIN

/**
Called when there's something to read on stdin.
* Called when there's something to read on stdin.
*/
void server::input_on_stdin()
{
if (m_interactive) {
// Readline does everything nicely in interactive sessions
rl_callback_read_char();
} else {
// Read from the input
QFile f;
f.open(stdin, QIODevice::ReadOnly);
// Read from the input
if (f.atEnd() && m_stdin_notifier != nullptr) {
// QSocketNotifier gets mad after EOF. Turn it off.
m_stdin_notifier->deleteLater();
Expand All @@ -556,11 +666,17 @@ void server::input_on_stdin()
update_game_state();
}

#endif

/**
Prepares for a new game.
*/
void server::prepare_game()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

set_server_state(S_S_INITIAL);

// Load a script file.
Expand Down Expand Up @@ -588,6 +704,10 @@ void server::prepare_game()
*/
void server::begin_turn()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

::begin_turn(m_is_new_turn);

// Start the first phase
Expand All @@ -599,6 +719,10 @@ void server::begin_turn()
*/
void server::begin_phase()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

log_debug("Starting phase %d/%d.", game.info.phase,
game.server.num_phases);
::begin_phase(m_is_new_turn);
Expand Down Expand Up @@ -672,6 +796,10 @@ void server::begin_phase()
*/
void server::end_phase()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

m_between_turns_timer =
timer_renew(m_between_turns_timer, TIMER_USER, TIMER_ACTIVE);
timer_start(m_between_turns_timer);
Expand Down Expand Up @@ -711,6 +839,10 @@ void server::end_phase()
*/
void server::end_turn()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

::end_turn();
log_debug("Sendinfotometaserver");
(void) send_server_info_to_metaserver(META_REFRESH);
Expand Down Expand Up @@ -761,6 +893,10 @@ void server::end_turn()
*/
void server::update_game_state()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

// Set in the following cases:
// - in pregame: game start
// - during the game: turn done, end game and any other command affecting
Expand Down Expand Up @@ -836,6 +972,10 @@ void server::update_game_state()
*/
bool server::shut_game_down()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

// Close it even between games.
save_system_close();

Expand All @@ -861,6 +1001,10 @@ bool server::shut_game_down()
*/
void server::quit_idle()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

m_quitidle_timer = nullptr;

if (conn_list_size(game.est_connections) > 0) {
Expand Down Expand Up @@ -894,6 +1038,10 @@ void server::quit_idle()
*/
void server::pulse()
{
#ifdef Q_OS_WIN
QMutexLocker lock(&s_stdin_mutex);
#endif

send_pings();

get_lanserver_announcement();
Expand Down
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