Make logging cost free when there is no output target (#12247)

The logging streams now do almost no work when there is no output target for them.

For example, if LL_VERBOSE has no output targets, then `verbosestream << x` will return a StreamProxy with a null target. Any further `<<` operations applied to it will do nothing.

builtin/settingtypes.txt

@@ -1468,7 +1468,8 @@ language (Language) enum   ,be,bg,ca,cs,da,de,el,en,eo,es,et,eu,fi,fr,gd,gl,hu,i
 #    -    action
 #    -    info
 #    -    verbose
-debug_log_level (Debug log level) enum action ,none,error,warning,action,info,verbose
+#    -    trace
+debug_log_level (Debug log level) enum action ,none,error,warning,action,info,verbose,trace
 
 #    If the file size of debug.txt exceeds the number of megabytes specified in
 #    this setting when it is opened, the file is moved to debug.txt.1,
@@ -1477,7 +1478,7 @@ debug_log_level (Debug log level) enum action ,none,error,warning,action,info,ve
 debug_log_size_max (Debug log file size threshold) int 50
 
 #    Minimal level of logging to be written to chat.
-chat_log_level (Chat log level) enum error ,none,error,warning,action,info,verbose
+chat_log_level (Chat log level) enum error ,none,error,warning,action,info,verbose,trace
 
 #    Enable IPv6 support (for both client and server).
 #    Required for IPv6 connections to work at all.

minetest.conf.example

@@ -1768,7 +1768,8 @@
 #    -    action
 #    -    info
 #    -    verbose
-#    type: enum values: , none, error, warning, action, info, verbose
+#    -    trace
+#    type: enum values: , none, error, warning, action, info, verbose, trace
 # debug_log_level = action
 
 #    If the file size of debug.txt exceeds the number of megabytes specified in
@@ -1779,7 +1780,7 @@
 # debug_log_size_max = 50
 
 #    Minimal level of logging to be written to chat.
-#    type: enum values: , none, error, warning, action, info, verbose
+#    type: enum values: , none, error, warning, action, info, verbose, trace
 # chat_log_level = error
 
 #    Enable IPv6 support (for both client and server).

src/client/game.cpp

@@ -1491,7 +1491,7 @@ bool Game::connectToServer(const GameStartData &start_data,
 	client->m_simple_singleplayer_mode = simple_singleplayer_mode;
 
 	infostream << "Connecting to server at ";
-	connect_address.print(&infostream);
+	connect_address.print(infostream);
 	infostream << std::endl;
 
 	client->connect(connect_address,

src/client/renderingengine.cpp

@@ -116,7 +116,7 @@ RenderingEngine::RenderingEngine(IEventReceiver *receiver)
 	}
 
 	SIrrlichtCreationParameters params = SIrrlichtCreationParameters();
-	if (g_logger.getTraceEnabled())
+	if (tracestream)
 		params.LoggingLevel = irr::ELL_DEBUG;
 	params.DriverType = driverType;
 	params.WindowSize = core::dimension2d<u32>(screen_w, screen_h);

src/log.cpp

@@ -35,43 +35,30 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include <cerrno>
 #include <cstring>
 
-const int BUFFER_LENGTH = 256;
-
-class StringBuffer : public std::streambuf {
+class LevelTarget : public LogTarget {
 public:
-	StringBuffer() {
-		buffer_index = 0;
-	}
-
-	int overflow(int c);
-	virtual void flush(const std::string &buf) = 0;
-	std::streamsize xsputn(const char *s, std::streamsize n);
-	void push_back(char c);
-
-private:
-	char buffer[BUFFER_LENGTH];
-	int buffer_index;
-};
-
-
-class LogBuffer : public StringBuffer {
-public:
-	LogBuffer(Logger &logger, LogLevel lev) :
-		logger(logger),
-		level(lev)
+	LevelTarget(Logger &logger, LogLevel level, bool raw = false) :
+		m_logger(logger),
+		m_level(level),
+		m_raw(raw)
 	{}
 
-	void flush(const std::string &buffer);
+	virtual bool hasOutput() override {
+		return m_logger.hasOutput(m_level);
+	}
+
+	virtual void log(const std::string &buf) override {
+		if (!m_raw) {
+			m_logger.log(m_level, buf);
+		} else {
+			m_logger.logRaw(m_level, buf);
+		}
+	}
 
 private:
-	Logger &logger;
-	LogLevel level;
-};
-
-
-class RawLogBuffer : public StringBuffer {
-public:
-	void flush(const std::string &buffer);
+	Logger &m_logger;
+	LogLevel m_level;
+	bool m_raw;
 };
 
 ////
@@ -80,31 +67,33 @@ public:
 
 Logger g_logger;
 
+#ifdef __ANDROID__
+AndroidLogOutput stdout_output;
+AndroidLogOutput stderr_output;
+#else
 StreamLogOutput stdout_output(std::cout);
 StreamLogOutput stderr_output(std::cerr);
-std::ostream null_stream(NULL);
+#endif
 
-RawLogBuffer raw_buf;
+LevelTarget none_target_raw(g_logger, LL_NONE, true);
+LevelTarget none_target(g_logger, LL_NONE);
+LevelTarget error_target(g_logger, LL_ERROR);
+LevelTarget warning_target(g_logger, LL_WARNING);
+LevelTarget action_target(g_logger, LL_ACTION);
+LevelTarget info_target(g_logger, LL_INFO);
+LevelTarget verbose_target(g_logger, LL_VERBOSE);
+LevelTarget trace_target(g_logger, LL_TRACE);
 
-LogBuffer none_buf(g_logger, LL_NONE);
-LogBuffer error_buf(g_logger, LL_ERROR);
-LogBuffer warning_buf(g_logger, LL_WARNING);
-LogBuffer action_buf(g_logger, LL_ACTION);
-LogBuffer info_buf(g_logger, LL_INFO);
-LogBuffer verbose_buf(g_logger, LL_VERBOSE);
-
-// Connection
-std::ostream *dout_con_ptr = &null_stream;
-std::ostream *derr_con_ptr = &verbosestream;
-
-// Common streams
-std::ostream rawstream(&raw_buf);
-std::ostream dstream(&none_buf);
-std::ostream errorstream(&error_buf);
-std::ostream warningstream(&warning_buf);
-std::ostream actionstream(&action_buf);
-std::ostream infostream(&info_buf);
-std::ostream verbosestream(&verbose_buf);
+thread_local LogStream dstream(none_target);
+thread_local LogStream rawstream(none_target_raw);
+thread_local LogStream errorstream(error_target);
+thread_local LogStream warningstream(warning_target);
+thread_local LogStream actionstream(action_target);
+thread_local LogStream infostream(info_target);
+thread_local LogStream verbosestream(verbose_target);
+thread_local LogStream tracestream(trace_target);
+thread_local LogStream derr_con(verbose_target);
+thread_local LogStream dout_con(trace_target);
 
 // Android
 #ifdef __ANDROID__
@@ -118,29 +107,15 @@ static unsigned int g_level_to_android[] = {
 	//ANDROID_LOG_INFO,
 	ANDROID_LOG_DEBUG,    // LL_INFO
 	ANDROID_LOG_VERBOSE,  // LL_VERBOSE
+	ANDROID_LOG_VERBOSE,  // LL_TRACE
 };
 
-class AndroidSystemLogOutput : public ICombinedLogOutput {
-	public:
-		AndroidSystemLogOutput()
-		{
-			g_logger.addOutput(this);
-		}
-		~AndroidSystemLogOutput()
-		{
-			g_logger.removeOutput(this);
-		}
-		void logRaw(LogLevel lev, const std::string &line)
-		{
+void AndroidLogOutput::logRaw(LogLevel lev, const std::string &line) {
 	STATIC_ASSERT(ARRLEN(g_level_to_android) == LL_MAX,
 		mismatch_between_android_and_internal_loglevels);
 	__android_log_print(g_level_to_android[lev],
 		PROJECT_NAME_C, "%s", line.c_str());
-		}
-};
-
-AndroidSystemLogOutput g_android_log_output;
-
+}
 #endif
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -164,6 +139,8 @@ LogLevel Logger::stringToLevel(const std::string &name)
 		return LL_INFO;
 	else if (name == "verbose")
 		return LL_VERBOSE;
+	else if (name == "trace")
+		return LL_TRACE;
 	else
 		return LL_MAX;
 }
@@ -176,21 +153,26 @@ void Logger::addOutput(ILogOutput *out)
 void Logger::addOutput(ILogOutput *out, LogLevel lev)
 {
 	m_outputs[lev].push_back(out);
+	m_has_outputs[lev] = true;
 }
 
 void Logger::addOutputMasked(ILogOutput *out, LogLevelMask mask)
 {
 	for (size_t i = 0; i < LL_MAX; i++) {
-		if (mask & LOGLEVEL_TO_MASKLEVEL(i))
+		if (mask & LOGLEVEL_TO_MASKLEVEL(i)) {
 			m_outputs[i].push_back(out);
+			m_has_outputs[i] = true;
+		}
 	}
 }
 
 void Logger::addOutputMaxLevel(ILogOutput *out, LogLevel lev)
 {
 	assert(lev < LL_MAX);
-	for (size_t i = 0; i <= lev; i++)
+	for (size_t i = 0; i <= lev; i++) {
 		m_outputs[i].push_back(out);
+		m_has_outputs[i] = true;
+	}
 }
 
 LogLevelMask Logger::removeOutput(ILogOutput *out)
@@ -203,6 +185,7 @@ LogLevelMask Logger::removeOutput(ILogOutput *out)
 		if (it != m_outputs[i].end()) {
 			ret_mask |= LOGLEVEL_TO_MASKLEVEL(i);
 			m_outputs[i].erase(it);
+			m_has_outputs[i] = !m_outputs[i].empty();
 		}
 	}
 	return ret_mask;
@@ -236,6 +219,7 @@ const std::string Logger::getLevelLabel(LogLevel lev)
 		"ACTION",
 		"INFO",
 		"VERBOSE",
+		"TRACE",
 	};
 	assert(lev < LL_MAX && lev >= 0);
 	STATIC_ASSERT(ARRLEN(names) == LL_MAX,
@@ -297,7 +281,6 @@ void Logger::logToOutputs(LogLevel lev, const std::string &combined,
 		m_outputs[lev][i]->log(lev, combined, time, thread_name, payload_text);
 }
 
-
 ////
 //// *LogOutput methods
 ////
@@ -349,6 +332,7 @@ void StreamLogOutput::logRaw(LogLevel lev, const std::string &line)
 			m_stream << "\033[37m";
 			break;
 		case LL_VERBOSE:
+		case LL_TRACE:
 			// verbose is darker than info
 			m_stream << "\033[2m";
 			break;
@@ -396,6 +380,7 @@ void LogOutputBuffer::logRaw(LogLevel lev, const std::string &line)
 			color = "\x1b(c@#BBB)";
 			break;
 		case LL_VERBOSE: // dark grey
+		case LL_TRACE:
 			color = "\x1b(c@#888)";
 			break;
 		default: break;
@@ -404,47 +389,3 @@ void LogOutputBuffer::logRaw(LogLevel lev, const std::string &line)
 
 	m_buffer.push(color.append(line));
 }
-
-////
-//// *Buffer methods
-////
-
-int StringBuffer::overflow(int c)
-{
-	push_back(c);
-	return c;
-}
-
-
-std::streamsize StringBuffer::xsputn(const char *s, std::streamsize n)
-{
-	for (int i = 0; i < n; ++i)
-		push_back(s[i]);
-	return n;
-}
-
-void StringBuffer::push_back(char c)
-{
-	if (c == '\n' || c == '\r') {
-		if (buffer_index)
-			flush(std::string(buffer, buffer_index));
-		buffer_index = 0;
-	} else {
-		buffer[buffer_index++] = c;
-		if (buffer_index >= BUFFER_LENGTH) {
-			flush(std::string(buffer, buffer_index));
-			buffer_index = 0;
-		}
-	}
-}
-
-
-void LogBuffer::flush(const std::string &buffer)
-{
-	logger.log(level, buffer);
-}
-
-void RawLogBuffer::flush(const std::string &buffer)
-{
-	g_logger.logRaw(LL_NONE, buffer);
-}

src/log.h

@@ -19,6 +19,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #pragma once
 
+#include <atomic>
 #include <map>
 #include <queue>
 #include <string>
@@ -28,6 +29,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #if !defined(_WIN32)  // POSIX
 	#include <unistd.h>
 #endif
+#include "util/basic_macros.h"
+#include "util/stream.h"
 #include "irrlichttypes.h"
 
 class ILogOutput;
@@ -39,6 +42,7 @@ enum LogLevel {
 	LL_ACTION,  // In-game actions
 	LL_INFO,
 	LL_VERBOSE,
+	LL_TRACE,
 	LL_MAX,
 };
 
@@ -67,12 +71,13 @@ public:
 	// Logs without a prefix
 	void logRaw(LogLevel lev, const std::string &text);
 
-	void setTraceEnabled(bool enable) { m_trace_enabled = enable; }
-	bool getTraceEnabled() { return m_trace_enabled; }
-
 	static LogLevel stringToLevel(const std::string &name);
 	static const std::string getLevelLabel(LogLevel lev);
 
+	bool hasOutput(LogLevel level) {
+		return m_has_outputs[level].load(std::memory_order_relaxed);
+	}
+
 	static LogColor color_mode;
 
 private:
@@ -84,6 +89,7 @@ private:
 	const std::string getThreadName();
 
 	std::vector<ILogOutput *> m_outputs[LL_MAX];
+	std::atomic<bool> m_has_outputs[LL_MAX];
 
 	// Should implement atomic loads and stores (even though it's only
 	// written to when one thread has access currently).
@@ -91,7 +97,6 @@ private:
 	volatile bool m_silenced_levels[LL_MAX];
 	std::map<std::thread::id, std::string> m_thread_names;
 	mutable std::mutex m_mutex;
-	bool m_trace_enabled;
 };
 
 class ILogOutput {
@@ -185,35 +190,178 @@ private:
 	Logger &m_logger;
 };
 
+#ifdef __ANDROID__
+class AndroidLogOutput : public ICombinedLogOutput {
+public:
+	void logRaw(LogLevel lev, const std::string &line);
+};
+#endif
 
+/*
+ * LogTarget
+ *
+ * This is the interface that sits between the LogStreams and the global logger.
+ * Primarily used to route streams to log levels, but could also enable other
+ * custom behavior.
+ *
+ */
+class LogTarget {
+public:
+	// Must be thread-safe. These can be called from any thread.
+	virtual bool hasOutput() = 0;
+	virtual void log(const std::string &buf) = 0;
+};
+
+
+/*
+ * StreamProxy
+ *
+ * An ostream-like object that can proxy to a real ostream or do nothing,
+ * depending on how it is configured. See LogStream below.
+ *
+ */
+class StreamProxy {
+public:
+	StreamProxy(std::ostream *os) : m_os(os) { }
+
+	template<typename T>
+	StreamProxy& operator<<(T&& arg) {
+		if (m_os) {
+			*m_os << std::forward<T>(arg);
+		}
+		return *this;
+	}
+
+	StreamProxy& operator<<(std::ostream& (*manip)(std::ostream&)) {
+		if (m_os) {
+			*m_os << manip;
+		}
+		return *this;
+	}
+
+private:
+	std::ostream *m_os;
+};
+
+
+/*
+ * LogStream
+ *
+ * The public interface for log streams (infostream, verbosestream, etc).
+ *
+ * LogStream minimizes the work done when a given stream is off. (meaning
+ * it has no output targets, so it goes to /dev/null)
+ *
+ * For example, consider:
+ *
+ *     verbosestream << "hello world" << 123 << std::endl;
+ *
+ * The compiler evaluates this as:
+ *
+ *   (((verbosestream << "hello world") << 123) << std::endl)
+ *      ^                            ^
+ *
+ * If `verbosestream` is on, the innermost expression (marked by ^) will return
+ * a StreamProxy that forwards to a real ostream, that feeds into the logger.
+ * However, if `verbosestream` is off, it will return a StreamProxy that does
+ * nothing on all later operations. Specifically, CPU time won't be wasted
+ * writing "hello world" and 123 into a buffer, or formatting the log entry.
+ *
+ * It is also possible to directly check if the stream is on/off:
+ *
+ *   if (verbosestream) {
+ *       auto data = ComputeExpensiveDataForTheLog();
+ *       verbosestream << data << endl;
+ *   }
+ *
+*/
+
+class LogStream {
+public:
+	LogStream() = delete;
+	DISABLE_CLASS_COPY(LogStream);
+
+	LogStream(LogTarget &target) :
+		m_target(target),
+		m_buffer(std::bind(&LogStream::internalFlush, this, std::placeholders::_1)),
+		m_dummy_buffer(),
+		m_stream(&m_buffer),
+		m_dummy_stream(&m_dummy_buffer),
+		m_proxy(&m_stream),
+		m_dummy_proxy(nullptr) { }
+
+	template<typename T>
+	StreamProxy& operator<<(T&& arg) {
+		StreamProxy& sp = m_target.hasOutput() ? m_proxy : m_dummy_proxy;
+		sp << std::forward<T>(arg);
+		return sp;
+	}
+
+	StreamProxy& operator<<(std::ostream& (*manip)(std::ostream&)) {
+		StreamProxy& sp = m_target.hasOutput() ? m_proxy : m_dummy_proxy;
+		sp << manip;
+		return sp;
+	}
+
+	operator bool() {
+		return m_target.hasOutput();
+	}
+
+	void internalFlush(const std::string &buf) {
+		m_target.log(buf);
+	}
+
+	operator std::ostream&() {
+		return m_target.hasOutput() ? m_stream : m_dummy_stream;
+	}
+
+private:
+	// 10 streams per thread x (256 + overhead) ~ 3K per thread
+	static const int BUFFER_LENGTH = 256;
+	LogTarget &m_target;
+	StringStreamBuffer<BUFFER_LENGTH> m_buffer;
+	DummyStreamBuffer m_dummy_buffer;
+	std::ostream m_stream;
+	std::ostream m_dummy_stream;
+	StreamProxy m_proxy;
+	StreamProxy m_dummy_proxy;
+
+};
+
+#ifdef __ANDROID__
+extern AndroidLogOutput stdout_output;
+extern AndroidLogOutput stderr_output;
+#else
 extern StreamLogOutput stdout_output;
 extern StreamLogOutput stderr_output;
-extern std::ostream null_stream;
-
-extern std::ostream *dout_con_ptr;
-extern std::ostream *derr_con_ptr;
-extern std::ostream *derr_server_ptr;
+#endif
 
 extern Logger g_logger;
 
-// Writes directly to all LL_NONE log outputs for g_logger with no prefix.
-extern std::ostream rawstream;
+/*
+ * By making the streams thread_local, each thread has its own
+ * private buffer. Two or more threads can write to the same stream
+ * simultaneously (lock-free), and there won't be any interference.
+ *
+ * The finished lines are sent to a LogTarget which is a global (not thread-local)
+ * object, and from there relayed to g_logger. The final writes are serialized
+ * by the mutex in g_logger.
+*/
 
-extern std::ostream errorstream;
-extern std::ostream warningstream;
-extern std::ostream actionstream;
-extern std::ostream infostream;
-extern std::ostream verbosestream;
-extern std::ostream dstream;
+extern thread_local LogStream dstream;
+extern thread_local LogStream rawstream;  // Writes directly to all LL_NONE log outputs with no prefix.
+extern thread_local LogStream errorstream;
+extern thread_local LogStream warningstream;
+extern thread_local LogStream actionstream;
+extern thread_local LogStream infostream;
+extern thread_local LogStream verbosestream;
+extern thread_local LogStream tracestream;
+// TODO: Search/replace these with verbose/tracestream
+extern thread_local LogStream derr_con;
+extern thread_local LogStream dout_con;
 
-#define TRACEDO(x) do {               \
-	if (g_logger.getTraceEnabled()) { \
-		x;                            \
+#define TRACESTREAM(x) do {	\
+	if (tracestream) { 	\
+		tracestream x;	\
 	}			\
 } while (0)
-
-#define TRACESTREAM(x) TRACEDO(verbosestream x)
-
-#define dout_con (*dout_con_ptr)
-#define derr_con (*derr_con_ptr)
-

src/main.cpp

@@ -453,14 +453,6 @@ static bool setup_log_params(const Settings &cmd_args)
 		}
 	}
 
-	// If trace is enabled, enable logging of certain things
-	if (cmd_args.getFlag("trace")) {
-		dstream << _("Enabling trace level debug output") << std::endl;
-		g_logger.setTraceEnabled(true);
-		dout_con_ptr = &verbosestream; // This is somewhat old
-		socket_enable_debug_output = true; // Sockets doesn't use log.h
-	}
-
 	// In certain cases, output info level on stderr
 	if (cmd_args.getFlag("info") || cmd_args.getFlag("verbose") ||
 			cmd_args.getFlag("trace") || cmd_args.getFlag("speedtests"))
@@ -470,6 +462,12 @@ static bool setup_log_params(const Settings &cmd_args)
 	if (cmd_args.getFlag("verbose") || cmd_args.getFlag("trace"))
 		g_logger.addOutput(&stderr_output, LL_VERBOSE);
 
+	if (cmd_args.getFlag("trace")) {
+		dstream << _("Enabling trace level debug output") << std::endl;
+		g_logger.addOutput(&stderr_output, LL_TRACE);
+		socket_enable_debug_output = true;
+	}
+
 	return true;
 }
 
@@ -599,7 +597,7 @@ static void init_log_streams(const Settings &cmd_args)
 		warningstream << "Deprecated use of debug_log_level with an "
 			"integer value; please update your configuration." << std::endl;
 		static const char *lev_name[] =
-			{"", "error", "action", "info", "verbose"};
+			{"", "error", "action", "info", "verbose", "trace"};
 		int lev_i = atoi(conf_loglev.c_str());
 		if (lev_i < 0 || lev_i >= (int)ARRLEN(lev_name)) {
 			warningstream << "Supplied invalid debug_log_level!"

src/network/address.cpp

@@ -230,14 +230,14 @@ void Address::setPort(u16 port)
 	m_port = port;
 }
 
-void Address::print(std::ostream *s) const
+void Address::print(std::ostream& s) const
 {
 	if (m_addr_family == AF_INET6)
-		*s << "[" << serializeString() << "]:" << m_port;
+		s << "[" << serializeString() << "]:" << m_port;
 	else if (m_addr_family == AF_INET)
-		*s << serializeString() << ":" << m_port;
+		s << serializeString() << ":" << m_port;
 	else
-		*s << "(undefined)";
+		s << "(undefined)";
 }
 
 bool Address::isLocalhost() const

src/network/address.h

@@ -59,7 +59,7 @@ public:
 	int getFamily() const { return m_addr_family; }
 	bool isIPv6() const { return m_addr_family == AF_INET6; }
 	bool isZero() const;
-	void print(std::ostream *s) const;
+	void print(std::ostream &s) const;
 	std::string serializeString() const;
 	bool isLocalhost() const;
 

src/network/connection.cpp

@@ -41,25 +41,14 @@ namespace con
 /* defines used for debugging and profiling                                   */
 /******************************************************************************/
 #ifdef NDEBUG
-	#define LOG(a) a
 	#define PROFILE(a)
 #else
-	#if 0
-	/* this mutex is used to achieve log message consistency */
-	std::mutex log_message_mutex;
-	#define LOG(a)                                                                 \
-		{                                                                          \
-		MutexAutoLock loglock(log_message_mutex);                                 \
-		a;                                                                         \
-		}
-	#else
-	// Prevent deadlocks until a solution is found after 5.2.0 (TODO)
-	#define LOG(a) a
-	#endif
-
 	#define PROFILE(a) a
 #endif
 
+// TODO: Clean this up.
+#define LOG(a) a
+
 #define PING_TIMEOUT 5.0
 
 u16 BufferedPacket::getSeqnum() const

src/network/connectionthreads.cpp

@@ -32,22 +32,18 @@ namespace con
 /* defines used for debugging and profiling                                   */
 /******************************************************************************/
 #ifdef NDEBUG
-#define LOG(a) a
 #define PROFILE(a)
 #undef DEBUG_CONNECTION_KBPS
 #else
 /* this mutex is used to achieve log message consistency */
-std::mutex log_conthread_mutex;
-#define LOG(a)                                                                \
-	{                                                                         \
-	MutexAutoLock loglock(log_conthread_mutex);                                 \
-	a;                                                                        \
-	}
 #define PROFILE(a) a
 //#define DEBUG_CONNECTION_KBPS
 #undef DEBUG_CONNECTION_KBPS
 #endif
 
+// TODO: Clean this up.
+#define LOG(a) a
+
 #define WINDOW_SIZE 5
 
 static session_t readPeerId(const u8 *packetdata)

src/network/socket.cpp

@@ -198,7 +198,7 @@ void UDPSocket::Send(const Address &destination, const void *data, int size)
 	if (socket_enable_debug_output) {
 		// Print packet destination and size
 		dstream << (int)m_handle << " -> ";
-		destination.print(&dstream);
+		destination.print(dstream);
 		dstream << ", size=" << size;
 
 		// Print packet contents
@@ -295,7 +295,7 @@ int UDPSocket::Receive(Address &sender, void *data, int size)
 	if (socket_enable_debug_output) {
 		// Print packet sender and size
 		dstream << (int)m_handle << " <- ";
-		sender.print(&dstream);
+		sender.print(dstream);
 		dstream << ", size=" << received;
 
 		// Print packet contents

src/server.cpp

@@ -525,7 +525,7 @@ void Server::start()
 	actionstream << "World at [" << m_path_world << "]" << std::endl;
 	actionstream << "Server for gameid=\"" << m_gamespec.id
 			<< "\" listening on ";
-	m_bind_addr.print(&actionstream);
+	m_bind_addr.print(actionstream);
 	actionstream << "." << std::endl;
 }
 

src/util/stream.h

@@ -0,0 +1,70 @@
+/*
+Minetest
+Copyright (C) 2022 Minetest Authors
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#pragma once
+
+#include <iostream>
+#include <string>
+#include <functional>
+
+template<int BufferLength, typename Emitter = std::function<void(const std::string &)> >
+class StringStreamBuffer : public std::streambuf {
+public:
+	StringStreamBuffer(Emitter emitter) : m_emitter(emitter) {
+		buffer_index = 0;
+	}
+
+	int overflow(int c) {
+		push_back(c);
+		return c;
+	}
+
+	void push_back(char c) {
+		if (c == '\n' || c == '\r') {
+			if (buffer_index)
+				m_emitter(std::string(buffer, buffer_index));
+			buffer_index = 0;
+		} else {
+			buffer[buffer_index++] = c;
+			if (buffer_index >= BufferLength) {
+				m_emitter(std::string(buffer, buffer_index));
+				buffer_index = 0;
+			}
+		}
+	}
+
+	std::streamsize xsputn(const char *s, std::streamsize n) {
+		for (int i = 0; i < n; ++i)
+			push_back(s[i]);
+		return n;
+	}
+private:
+	Emitter m_emitter;
+	char buffer[BufferLength];
+	int buffer_index;
+};
+
+class DummyStreamBuffer : public std::streambuf {
+	int overflow(int c) {
+		return c;
+	}
+	std::streamsize xsputn(const char *s, std::streamsize n) {
+		return n;
+	}
+};