core/log: add custom log encoder for smaller log storage

Will be used to store more detailed logs in the future without using
as much disk space.

CMakeLists.txt

@@ -6,7 +6,7 @@ set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 option(BUILD_TESTING "Build tests" OFF)
-option(ASAN "Enable ASAN" OFF)
+option(ASAN "Enable ASAN" OFF) # note: better output with gcc than clang
 option(FRAME_POINTERS "Always keep frame pointers" ${ASAN})
 
 option(USE_JEMALLOC "Use jemalloc over the system malloc implementation" ON)

src/core/logging.cpp

@@ -1,24 +1,86 @@
 #include "logging.hpp"
+#include <array>
 #include <cstdio>
-#include <cstring>
 
+#include <qbytearrayview.h>
+#include <qdatetime.h>
+#include <qendian.h>
+#include <qhashfunctions.h>
 #include <qlogging.h>
 #include <qloggingcategory.h>
 #include <qnamespace.h>
 #include <qobject.h>
 #include <qobjectdefs.h>
 #include <qstring.h>
+#include <qsysinfo.h>
 #include <qtenvironmentvariables.h>
 #include <qtextstream.h>
 #include <qthread.h>
 #include <qtmetamacros.h>
+#include <qtypes.h>
 #include <sys/mman.h>
 #include <sys/sendfile.h>
 
+#include "logging_p.hpp"
 #include "paths.hpp"
 
+namespace qs::log {
+
 Q_LOGGING_CATEGORY(logLogging, "quickshell.logging", QtWarningMsg);
 
+bool LogMessage::operator==(const LogMessage& other) const {
+	// note: not including time
+	return this->type == other.type && this->category == other.category && this->body == other.body;
+}
+
+size_t qHash(const LogMessage& message) {
+	return qHash(message.type) ^ qHash(message.category) ^ qHash(message.body);
+}
+
+void LogMessage::formatMessage(
+    QTextStream& stream,
+    const LogMessage& msg,
+    bool color,
+    bool timestamp
+) {
+	if (timestamp) {
+		if (color) stream << "\033[90m";
+		stream << msg.time.toString("yyyy-MM-dd hh:mm:ss.zzz");
+	}
+
+	if (color) {
+		switch (msg.type) {
+		case QtDebugMsg: stream << "\033[34m DEBUG"; break;
+		case QtInfoMsg: stream << "\033[32m  INFO"; break;
+		case QtWarningMsg: stream << "\033[33m  WARN"; break;
+		case QtCriticalMsg: stream << "\033[31m ERROR"; break;
+		case QtFatalMsg: stream << "\033[31m FATAL"; break;
+		}
+	} else {
+		switch (msg.type) {
+		case QtDebugMsg: stream << " DEBUG"; break;
+		case QtInfoMsg: stream << "  INFO"; break;
+		case QtWarningMsg: stream << "  WARN"; break;
+		case QtCriticalMsg: stream << " ERROR"; break;
+		case QtFatalMsg: stream << " FATAL"; break;
+		}
+	}
+
+	const auto isDefault = msg.category == "default";
+
+	if (color && !isDefault && msg.type != QtFatalMsg) stream << "\033[97m";
+
+	if (!isDefault) {
+		stream << ' ' << msg.category;
+	}
+
+	if (color && msg.type != QtFatalMsg) stream << "\033[0m";
+
+	stream << ": " << msg.body;
+
+	if (color && msg.type == QtFatalMsg) stream << "\033[0m";
+}
+
 LogManager::LogManager()
     : colorLogs(qEnvironmentVariableIsEmpty("NO_COLOR"))
     , stdoutStream(stdout) {}
@@ -28,11 +90,11 @@ void LogManager::messageHandler(
     const QMessageLogContext& context,
     const QString& msg
 ) {
-	auto message = LogMessage(type, context.category, msg.toUtf8());
+	auto message = LogMessage(type, QLatin1StringView(context.category), msg.toUtf8());
 
 	auto* self = LogManager::instance();
 
-	LogManager::formatMessage(self->stdoutStream, message, self->colorLogs, false);
+	LogMessage::formatMessage(self->stdoutStream, message, self->colorLogs, false);
 	self->stdoutStream << Qt::endl;
 
 	emit self->logMessage(message);
@@ -64,50 +126,6 @@ void LogManager::initFs() {
 	);
 }
 
-void LogManager::formatMessage(
-    QTextStream& stream,
-    const LogMessage& msg,
-    bool color,
-    bool timestamp
-) {
-	if (timestamp) {
-		if (color) stream << "\033[90m";
-		stream << msg.time.toString("yyyy-MM-dd hh:mm:ss.zzz");
-	}
-
-	if (color) {
-		switch (msg.type) {
-		case QtDebugMsg: stream << "\033[34m DEBUG"; break;
-		case QtInfoMsg: stream << "\033[32m  INFO"; break;
-		case QtWarningMsg: stream << "\033[33m  WARN"; break;
-		case QtCriticalMsg: stream << "\033[31m ERROR"; break;
-		case QtFatalMsg: stream << "\033[31m FATAL"; break;
-		}
-	} else {
-		switch (msg.type) {
-		case QtDebugMsg: stream << " DEBUG"; break;
-		case QtInfoMsg: stream << "  INFO"; break;
-		case QtWarningMsg: stream << "  WARN"; break;
-		case QtCriticalMsg: stream << " ERROR"; break;
-		case QtFatalMsg: stream << " FATAL"; break;
-		}
-	}
-
-	const auto isDefault = strcmp(msg.category, "default") == 0;
-
-	if (color && !isDefault && msg.type != QtFatalMsg) stream << "\033[97m";
-
-	if (!isDefault) {
-		stream << ' ' << msg.category;
-	}
-
-	if (color && msg.type != QtFatalMsg) stream << "\033[0m";
-
-	stream << ": " << msg.body;
-
-	if (color && msg.type == QtFatalMsg) stream << "\033[0m";
-}
-
 void LoggingThreadProxy::initInThread() {
 	this->logging = new ThreadLogging(this);
 	this->logging->init();
@@ -116,17 +134,39 @@ void LoggingThreadProxy::initInThread() {
 void LoggingThreadProxy::initFs() { this->logging->initFs(); }
 
 void ThreadLogging::init() {
-	auto mfd = memfd_create("quickshell:logs", 0);
+	auto logMfd = memfd_create("quickshell:logs", 0);
 
-	if (mfd == -1) {
+	if (logMfd == -1) {
 		qCCritical(logLogging) << "Failed to create memfd for initial log storage"
 		                       << qt_error_string(-1);
-		return;
 	}
 
-	this->file = new QFile();
+	auto dlogMfd = memfd_create("quickshell:detailedlogs", 0);
-	this->file->open(mfd, QFile::WriteOnly, QFile::AutoCloseHandle);
+
-	this->fileStream.setDevice(this->file);
+	if (dlogMfd == -1) {
+		qCCritical(logLogging) << "Failed to create memfd for initial detailed log storage"
+		                       << qt_error_string(-1);
+	}
+
+	if (logMfd != -1) {
+		this->file = new QFile();
+		this->file->open(logMfd, QFile::WriteOnly, QFile::AutoCloseHandle);
+		this->fileStream.setDevice(this->file);
+	}
+
+	if (dlogMfd != -1) {
+		this->detailedFile = new QFile();
+		// buffered by WriteBuffer
+		this->detailedFile->open(dlogMfd, QFile::WriteOnly | QFile::Unbuffered, QFile::AutoCloseHandle);
+		this->detailedWriter.setDevice(this->detailedFile);
+
+		if (!this->detailedWriter.writeHeader()) {
+			qCCritical(logLogging) << "Could not write header for detailed logs.";
+			this->detailedWriter.setDevice(nullptr);
+			delete this->detailedFile;
+			this->detailedFile = nullptr;
+		}
+	}
 
 	// This connection is direct so it works while the event loop is destroyed between
 	// QCoreApplication delete and Q(Gui)Application launch.
@@ -138,11 +178,11 @@ void ThreadLogging::init() {
 	    Qt::DirectConnection
 	);
 
-	qCDebug(logLogging) << "Created memfd" << mfd << "for early logs.";
+	qCDebug(logLogging) << "Created memfd" << logMfd << "for early logs.";
+	qCDebug(logLogging) << "Created memfd" << dlogMfd << "for early detailed logs.";
 }
 
 void ThreadLogging::initFs() {
-
 	qCDebug(logLogging) << "Starting filesystem logging...";
 	auto* runDir = QsPaths::instance()->instanceRunDir();
 
@@ -153,23 +193,62 @@ void ThreadLogging::initFs() {
 	}
 
 	auto path = runDir->filePath("log.log");
+	auto detailedPath = runDir->filePath("log.qslog");
 	auto* file = new QFile(path);
+	auto* detailedFile = new QFile(detailedPath);
 
 	if (!file->open(QFile::WriteOnly | QFile::Truncate)) {
 		qCCritical(logLogging
 		) << "Could not start filesystem logger as the log file could not be created:"
 		  << path;
-		return;
+		delete file;
+		file = nullptr;
+	}
+
+	// buffered by WriteBuffer
+	if (!detailedFile->open(QFile::WriteOnly | QFile::Truncate | QFile::Unbuffered)) {
+		qCCritical(logLogging
+		) << "Could not start detailed filesystem logger as the log file could not be created:"
+		  << detailedPath;
+		delete detailedFile;
+		detailedFile = nullptr;
 	}
 
 	qCDebug(logLogging) << "Copying memfd logs to log file...";
 
-	auto* oldFile = this->file;
+	if (file) {
-	oldFile->seek(0);
+		auto* oldFile = this->file;
-	sendfile(file->handle(), oldFile->handle(), nullptr, oldFile->size());
+		if (oldFile) {
-	this->file = file;
+			oldFile->seek(0);
-	this->fileStream.setDevice(file);
+			sendfile(file->handle(), oldFile->handle(), nullptr, oldFile->size());
-	delete oldFile;
+		}
+
+		this->file = file;
+		this->fileStream.setDevice(file);
+		delete oldFile;
+	}
+
+	if (detailedFile) {
+		auto* oldFile = this->detailedFile;
+		if (oldFile) {
+			oldFile->seek(0);
+			sendfile(detailedFile->handle(), oldFile->handle(), nullptr, oldFile->size());
+		}
+
+		this->detailedFile = detailedFile;
+		this->detailedWriter.setDevice(detailedFile);
+
+		if (!oldFile) {
+			if (!this->detailedWriter.writeHeader()) {
+				qCCritical(logLogging) << "Could not write header for detailed logs.";
+				this->detailedWriter.setDevice(nullptr);
+				delete this->detailedFile;
+				this->detailedFile = nullptr;
+			}
+		}
+
+		delete oldFile;
+	}
 
 	qCDebug(logLogging) << "Switched logging to disk logs.";
 
@@ -189,6 +268,360 @@ void ThreadLogging::initFs() {
 
 void ThreadLogging::onMessage(const LogMessage& msg) {
 	if (this->fileStream.device() == nullptr) return;
-	LogManager::formatMessage(this->fileStream, msg, false, true);
+	LogMessage::formatMessage(this->fileStream, msg, false, true);
 	this->fileStream << Qt::endl;
+
+	if (this->detailedWriter.write(msg)) {
+		this->detailedFile->flush();
+	} else if (this->detailedFile != nullptr) {
+		qCCritical(logLogging) << "Detailed logger failed to write. Ending detailed logs.";
+	}
 }
+
+CompressedLogType compressedTypeOf(QtMsgType type) {
+	switch (type) {
+	case QtDebugMsg: return CompressedLogType::Debug;
+	case QtInfoMsg: return CompressedLogType::Info;
+	case QtWarningMsg: return CompressedLogType::Warn;
+	case QtCriticalMsg:
+	case QtFatalMsg: return CompressedLogType::Critical;
+	}
+}
+
+QtMsgType typeOfCompressed(CompressedLogType type) {
+	switch (type) {
+	case CompressedLogType::Debug: return QtDebugMsg;
+	case CompressedLogType::Info: return QtInfoMsg;
+	case CompressedLogType::Warn: return QtWarningMsg;
+	case CompressedLogType::Critical: return QtCriticalMsg;
+	}
+}
+
+void WriteBuffer::setDevice(QIODevice* device) { this->device = device; }
+bool WriteBuffer::hasDevice() const { return this->device; }
+
+bool WriteBuffer::flush() {
+	auto written = this->device->write(this->buffer);
+	auto success = written == this->buffer.length();
+	this->buffer.clear();
+	return success;
+}
+
+void WriteBuffer::writeBytes(const char* data, qsizetype length) {
+	this->buffer.append(data, length);
+}
+
+void WriteBuffer::writeU8(quint8 data) {
+	this->writeBytes(reinterpret_cast<char*>(&data), 1); // NOLINT
+}
+
+void WriteBuffer::writeU16(quint16 data) {
+	data = qToLittleEndian(data);
+	this->writeBytes(reinterpret_cast<char*>(&data), 2); // NOLINT
+}
+
+void WriteBuffer::writeU32(quint32 data) {
+	data = qToLittleEndian(data);
+	this->writeBytes(reinterpret_cast<char*>(&data), 4); // NOLINT
+}
+
+void WriteBuffer::writeU64(quint64 data) {
+	data = qToLittleEndian(data);
+	this->writeBytes(reinterpret_cast<char*>(&data), 8); // NOLINT
+}
+
+void DeviceReader::setDevice(QIODevice* device) { this->device = device; }
+bool DeviceReader::hasDevice() const { return this->device; }
+
+bool DeviceReader::readBytes(char* data, qsizetype length) {
+	return this->device->read(data, length) == length;
+}
+
+qsizetype DeviceReader::peekBytes(char* data, qsizetype length) {
+	return this->device->peek(data, length);
+}
+
+bool DeviceReader::skip(qsizetype length) { return this->device->skip(length) == length; }
+
+bool DeviceReader::readU8(quint8* data) {
+	return this->readBytes(reinterpret_cast<char*>(data), 1); // NOLINT
+}
+
+bool DeviceReader::readU16(quint16* data) {
+	return this->readBytes(reinterpret_cast<char*>(data), 2); // NOLINT
+}
+
+bool DeviceReader::readU32(quint32* data) {
+	return this->readBytes(reinterpret_cast<char*>(data), 4); // NOLINT
+}
+
+bool DeviceReader::readU64(quint64* data) {
+	return this->readBytes(reinterpret_cast<char*>(data), 8); // NOLINT
+}
+
+void EncodedLogWriter::setDevice(QIODevice* target) { this->buffer.setDevice(target); }
+void EncodedLogReader::setDevice(QIODevice* source) { this->reader.setDevice(source); }
+
+constexpr quint8 LOG_VERSION = 1;
+
+bool EncodedLogWriter::writeHeader() {
+	this->buffer.writeU8(LOG_VERSION);
+	return this->buffer.flush();
+}
+
+bool EncodedLogReader::readHeader(bool* success, quint8* version, quint8* readerVersion) {
+	if (!this->reader.readU8(version)) return false;
+	*success = *version == LOG_VERSION;
+	*readerVersion = LOG_VERSION;
+	return true;
+}
+
+bool EncodedLogWriter::write(const LogMessage& message) {
+	if (!this->buffer.hasDevice()) return false;
+
+	LogMessage* prevMessage = nullptr;
+	auto index = this->recentMessages.indexOf(message, &prevMessage);
+
+	// If its a dupe, save memory by reusing the buffer of the first message and letting
+	// the new one be deallocated.
+	auto body = prevMessage ? prevMessage->body : message.body;
+	this->recentMessages.emplace(message.type, message.category, body, message.time);
+
+	if (index != -1) {
+		auto secondDelta = this->lastMessageTime.secsTo(message.time);
+
+		if (secondDelta < 16 && index < 16) {
+			this->writeOp(EncodedLogOpcode::RecentMessageShort);
+			this->buffer.writeU8(index | (secondDelta << 4));
+		} else {
+			this->writeOp(EncodedLogOpcode::RecentMessageLong);
+			this->buffer.writeU8(index);
+			this->writeVarInt(secondDelta);
+		}
+
+		goto finish;
+	} else {
+		auto categoryId = this->getOrCreateCategory(message.category);
+		this->writeVarInt(categoryId);
+
+		auto writeFullTimestamp = [this, &message]() {
+			this->buffer.writeU64(message.time.toSecsSinceEpoch());
+		};
+
+		if (message.type == QtFatalMsg) {
+			this->buffer.writeU8(0xff);
+			writeFullTimestamp();
+		} else {
+			quint8 field = compressedTypeOf(message.type);
+
+			auto secondDelta = this->lastMessageTime.secsTo(message.time);
+			if (secondDelta > 29) {
+				// 0x1d = followed by delta int
+				// 0x1e = followed by epoch delta int
+				field |= (secondDelta < 0xffff ? 0x1d : 0x1e) << 3;
+			} else {
+				field |= secondDelta << 3;
+			}
+
+			this->buffer.writeU8(field);
+
+			if (secondDelta > 29) {
+				if (secondDelta > 0xffff) {
+					writeFullTimestamp();
+				} else {
+					this->writeVarInt(secondDelta);
+				}
+			}
+		}
+
+		this->writeString(message.body);
+	}
+
+finish:
+	// copy with second precision
+	this->lastMessageTime = QDateTime::fromSecsSinceEpoch(message.time.toSecsSinceEpoch());
+	return this->buffer.flush();
+}
+
+bool EncodedLogReader::read(LogMessage* slot) {
+start:
+	quint32 next = 0;
+	if (!this->readVarInt(&next)) return false;
+
+	if (next < EncodedLogOpcode::BeginCategories) {
+		if (next == EncodedLogOpcode::RegisterCategory) {
+			if (!this->registerCategory()) return false;
+			goto start;
+		} else if (next == EncodedLogOpcode::RecentMessageShort || next == EncodedLogOpcode::RecentMessageLong)
+		{
+			quint8 index = 0;
+			quint32 secondDelta = 0;
+
+			if (next == EncodedLogOpcode::RecentMessageShort) {
+				quint8 field = 0;
+				if (!this->reader.readU8(&field)) return false;
+				index = field & 0xf;
+				secondDelta = field >> 4;
+			} else {
+				if (!this->reader.readU8(&index)) return false;
+				if (!this->readVarInt(&secondDelta)) return false;
+			}
+
+			*slot = this->recentMessages.at(index);
+			this->lastMessageTime = this->lastMessageTime.addSecs(static_cast<qint64>(secondDelta));
+			slot->time = this->lastMessageTime;
+		}
+	} else {
+		auto category = this->categories.value(next - EncodedLogOpcode::BeginCategories);
+
+		quint8 field = 0;
+		if (!this->reader.readU8(&field)) return false;
+
+		auto msgType = QtDebugMsg;
+		quint64 secondDelta = 0;
+		auto needsTimeRead = false;
+
+		if (field == 0xff) {
+			msgType = QtFatalMsg;
+			needsTimeRead = true;
+		} else {
+			msgType = typeOfCompressed(static_cast<CompressedLogType>(field & 0x07));
+			secondDelta = field >> 3;
+
+			if (secondDelta == 0x1d) {
+				quint32 slot = 0;
+				if (!this->readVarInt(&slot)) return false;
+				secondDelta = slot;
+			} else if (secondDelta == 0x1e) {
+				needsTimeRead = true;
+			}
+		}
+
+		if (needsTimeRead) {
+			if (!this->reader.readU64(&secondDelta)) return false;
+		}
+
+		this->lastMessageTime = this->lastMessageTime.addSecs(static_cast<qint64>(secondDelta));
+
+		QByteArray body;
+		if (!this->readString(&body)) return false;
+
+		*slot = LogMessage(msgType, QLatin1StringView(category), body, this->lastMessageTime);
+	}
+
+	this->recentMessages.emplace(*slot);
+	return true;
+}
+
+void EncodedLogWriter::writeOp(EncodedLogOpcode opcode) { this->buffer.writeU8(opcode); }
+
+void EncodedLogWriter::writeVarInt(quint32 n) {
+	if (n < 0xff) {
+		this->buffer.writeU8(n);
+	} else if (n < 0xffff) {
+		this->buffer.writeU8(0xff);
+		this->buffer.writeU16(n);
+	} else {
+		this->buffer.writeU8(0xff);
+		this->buffer.writeU16(0xffff);
+		this->buffer.writeU32(n);
+	}
+}
+
+bool EncodedLogReader::readVarInt(quint32* slot) {
+	auto bytes = std::array<quint8, 7>();
+	auto readLength = this->reader.peekBytes(reinterpret_cast<char*>(bytes.data()), 7); // NOLINT
+
+	if (bytes[0] != 0xff && readLength >= 1) {
+		auto n = *reinterpret_cast<quint8*>(bytes.data()); // NOLINT
+		if (!this->reader.skip(1)) return false;
+		*slot = qFromLittleEndian(n);
+	} else if ((bytes[1] != 0xff || bytes[2] != 0xff) && readLength >= 3) {
+		auto n = *reinterpret_cast<quint16*>(bytes.data() + 1); // NOLINT
+		if (!this->reader.skip(3)) return false;
+		*slot = qFromLittleEndian(n);
+	} else if (readLength == 7) {
+		auto n = *reinterpret_cast<quint32*>(bytes.data() + 3); // NOLINT
+		if (!this->reader.skip(7)) return false;
+		*slot = qFromLittleEndian(n);
+	} else return false;
+
+	return true;
+}
+
+void EncodedLogWriter::writeString(QByteArrayView bytes) {
+	this->writeVarInt(bytes.length());
+	this->buffer.writeBytes(bytes.constData(), bytes.length());
+}
+
+bool EncodedLogReader::readString(QByteArray* slot) {
+	quint32 length = 0;
+	if (!this->readVarInt(&length)) return false;
+
+	*slot = QByteArray(length, Qt::Uninitialized);
+	auto r = this->reader.readBytes(slot->data(), slot->size());
+	return r;
+}
+
+quint16 EncodedLogWriter::getOrCreateCategory(QLatin1StringView category) {
+	if (this->categories.contains(category)) {
+		return this->categories.value(category);
+	} else {
+		this->writeOp(EncodedLogOpcode::RegisterCategory);
+		// id is implicitly the next available id
+		this->writeString(category);
+
+		auto id = this->nextCategory++;
+		this->categories.insert(category, id);
+
+		return id;
+	}
+}
+
+bool EncodedLogReader::registerCategory() {
+	QByteArray name;
+	if (!this->readString(&name)) return false;
+	this->categories.append(name);
+	return true;
+}
+
+bool readEncodedLogs(QIODevice* device) {
+	auto reader = EncodedLogReader();
+	reader.setDevice(device);
+
+	bool readable = false;
+	quint8 logVersion = 0;
+	quint8 readerVersion = 0;
+	if (!reader.readHeader(&readable, &logVersion, &readerVersion)) {
+		qCritical() << "Failed to read log header.";
+		return false;
+	}
+
+	if (!readable) {
+		qCritical() << "This log was encoded with version" << logVersion
+		            << "of the quickshell log encoder, which cannot be decoded by the current "
+		               "version of quickshell, with log version"
+		            << readerVersion;
+		return false;
+	}
+
+	auto color = LogManager::instance()->colorLogs;
+
+	LogMessage message;
+	auto stream = QTextStream(stdout);
+	while (reader.read(&message)) {
+		LogMessage::formatMessage(stream, message, color, true);
+		stream << '\n';
+	}
+
+	stream << Qt::flush;
+
+	if (!device->atEnd()) {
+		qCritical() << "An error occurred parsing the end of this log file.";
+		qCritical() << "Remaining data:" << device->readAll();
+	}
+
+	return true;
+}
+
+} // namespace qs::log

src/core/logging.hpp

@@ -2,17 +2,22 @@
 
 #include <utility>
 
+#include <qcontainerfwd.h>
 #include <qdatetime.h>
-#include <qfile.h>
+#include <qhash.h>
+#include <qlatin1stringview.h>
 #include <qlogging.h>
 #include <qobject.h>
-#include <qtextstream.h>
 #include <qtmetamacros.h>
 
+namespace qs::log {
+
 struct LogMessage {
+	explicit LogMessage() = default;
+
 	explicit LogMessage(
 	    QtMsgType type,
-	    const char* category,
+	    QLatin1StringView category,
 	    QByteArray body,
 	    QDateTime time = QDateTime::currentDateTime()
 	)
@@ -21,29 +26,19 @@ struct LogMessage {
 	    , category(category)
 	    , body(std::move(body)) {}
 
-	QtMsgType type;
+	bool operator==(const LogMessage& other) const;
+
+	QtMsgType type = QtDebugMsg;
 	QDateTime time;
-	const char* category;
+	QLatin1StringView category;
 	QByteArray body;
+
+	static void formatMessage(QTextStream& stream, const LogMessage& msg, bool color, bool timestamp);
 };
 
-class ThreadLogging: public QObject {
+size_t qHash(const LogMessage& message);
-	Q_OBJECT;
 
-public:
+class ThreadLogging;
-	explicit ThreadLogging(QObject* parent): QObject(parent) {}
-
-	void init();
-	void initFs();
-	void setupFileLogging();
-
-private slots:
-	void onMessage(const LogMessage& msg);
-
-private:
-	QFile* file = nullptr;
-	QTextStream fileStream;
-};
 
 class LoggingThreadProxy: public QObject {
 	Q_OBJECT;
@@ -67,7 +62,7 @@ public:
 	static void initFs();
 	static LogManager* instance();
 
-	static void formatMessage(QTextStream& stream, const LogMessage& msg, bool color, bool timestamp);
+	bool colorLogs;
 
 signals:
 	void logMessage(LogMessage msg);
@@ -76,7 +71,12 @@ private:
 	explicit LogManager();
 	static void messageHandler(QtMsgType type, const QMessageLogContext& context, const QString& msg);
 
-	bool colorLogs;
 	QTextStream stdoutStream;
 	LoggingThreadProxy threadProxy;
 };
+
+bool readEncodedLogs(QIODevice* device);
+
+} // namespace qs::log
+
+using LogManager = qs::log::LogManager;

src/core/logging_p.hpp

@@ -0,0 +1,123 @@
+#pragma once
+#include <qbytearrayview.h>
+#include <qcontainerfwd.h>
+#include <qfile.h>
+#include <qlogging.h>
+#include <qtmetamacros.h>
+#include <qtypes.h>
+
+#include "logging.hpp"
+#include "ringbuf.hpp"
+
+namespace qs::log {
+
+enum EncodedLogOpcode : quint8 {
+	RegisterCategory = 0,
+	RecentMessageShort,
+	RecentMessageLong,
+	BeginCategories,
+};
+
+enum CompressedLogType : quint8 {
+	Debug = 0,
+	Info = 1,
+	Warn = 2,
+	Critical = 3,
+};
+
+CompressedLogType compressedTypeOf(QtMsgType type);
+QtMsgType typeOfCompressed(CompressedLogType type);
+
+class WriteBuffer {
+public:
+	void setDevice(QIODevice* device);
+	[[nodiscard]] bool hasDevice() const;
+	[[nodiscard]] bool flush();
+	void writeBytes(const char* data, qsizetype length);
+	void writeU8(quint8 data);
+	void writeU16(quint16 data);
+	void writeU32(quint32 data);
+	void writeU64(quint64 data);
+
+private:
+	QIODevice* device = nullptr;
+	QByteArray buffer;
+};
+
+class DeviceReader {
+public:
+	void setDevice(QIODevice* device);
+	[[nodiscard]] bool hasDevice() const;
+	[[nodiscard]] bool readBytes(char* data, qsizetype length);
+	// peek UP TO length
+	[[nodiscard]] qsizetype peekBytes(char* data, qsizetype length);
+	[[nodiscard]] bool skip(qsizetype length);
+	[[nodiscard]] bool readU8(quint8* data);
+	[[nodiscard]] bool readU16(quint16* data);
+	[[nodiscard]] bool readU32(quint32* data);
+	[[nodiscard]] bool readU64(quint64* data);
+
+private:
+	QIODevice* device = nullptr;
+};
+
+class EncodedLogWriter {
+public:
+	void setDevice(QIODevice* target);
+	[[nodiscard]] bool writeHeader();
+	[[nodiscard]] bool write(const LogMessage& message);
+
+private:
+	void writeOp(EncodedLogOpcode opcode);
+	void writeVarInt(quint32 n);
+	void writeString(QByteArrayView bytes);
+	quint16 getOrCreateCategory(QLatin1StringView category);
+
+	WriteBuffer buffer;
+
+	QHash<QLatin1StringView, quint16> categories;
+	quint16 nextCategory = EncodedLogOpcode::BeginCategories;
+
+	QDateTime lastMessageTime = QDateTime::fromSecsSinceEpoch(0);
+	HashBuffer<LogMessage> recentMessages {256};
+};
+
+class EncodedLogReader {
+public:
+	void setDevice(QIODevice* source);
+	[[nodiscard]] bool readHeader(bool* success, quint8* logVersion, quint8* readerVersion);
+	// WARNING: log messages written to the given slot are invalidated when the log reader is destroyed.
+	[[nodiscard]] bool read(LogMessage* slot);
+
+private:
+	[[nodiscard]] bool readVarInt(quint32* slot);
+	[[nodiscard]] bool readString(QByteArray* slot);
+	[[nodiscard]] bool registerCategory();
+
+	DeviceReader reader;
+	QVector<QByteArray> categories;
+	QDateTime lastMessageTime = QDateTime::fromSecsSinceEpoch(0);
+	RingBuffer<LogMessage> recentMessages {256};
+};
+
+class ThreadLogging: public QObject {
+	Q_OBJECT;
+
+public:
+	explicit ThreadLogging(QObject* parent): QObject(parent) {}
+
+	void init();
+	void initFs();
+	void setupFileLogging();
+
+private slots:
+	void onMessage(const LogMessage& msg);
+
+private:
+	QFile* file = nullptr;
+	QTextStream fileStream;
+	QFile* detailedFile = nullptr;
+	EncodedLogWriter detailedWriter;
+};
+
+} // namespace qs::log

src/core/main.cpp

@@ -61,6 +61,7 @@ int qs_main(int argc, char** argv) {
 		auto workdirOption = QCommandLineOption({"d", "workdir"}, "Initial working directory.", "path");
 		auto debugPortOption = QCommandLineOption("debugport", "Enable the QML debugger.", "port");
 		auto debugWaitOption = QCommandLineOption("waitfordebug", "Wait for debugger connection before launching.");
+		auto readLogOption = QCommandLineOption("read-log", "Read a quickshell log file to stdout.", "path");
 		// clang-format on
 
 		parser.addOption(currentOption);
@@ -70,8 +71,22 @@ int qs_main(int argc, char** argv) {
 		parser.addOption(workdirOption);
 		parser.addOption(debugPortOption);
 		parser.addOption(debugWaitOption);
+		parser.addOption(readLogOption);
 		parser.process(app);
 
+		auto logOption = parser.value(readLogOption);
+		if (!logOption.isEmpty()) {
+			auto file = QFile(logOption);
+			if (!file.open(QFile::ReadOnly)) {
+				qCritical() << "Failed to open log for reading:" << logOption;
+				return -1;
+			} else {
+				qInfo() << "Reading log" << logOption;
+			}
+
+			return qs::log::readEncodedLogs(&file) ? 0 : -1;
+		}
+
 		auto debugPortStr = parser.value(debugPortOption);
 		if (!debugPortStr.isEmpty()) {
 			auto ok = false;

src/core/ringbuf.hpp

@@ -0,0 +1,169 @@
+#pragma once
+
+#include <new>
+#include <tuple>
+#include <utility>
+
+#include <qcontainerfwd.h>
+#include <qhashfunctions.h>
+#include <qtclasshelpermacros.h>
+#include <qtypes.h>
+
+// NOLINTBEGIN(cppcoreguidelines-pro-bounds-pointer-arithmetic)
+
+// capacity 0 buffer cannot be inserted into, only replaced with =
+// this is NOT exception safe for constructors
+template <typename T>
+class RingBuffer {
+public:
+	explicit RingBuffer() = default;
+	explicit RingBuffer(qsizetype capacity): mCapacity(capacity) {
+		if (capacity > 0) this->createData();
+	}
+
+	~RingBuffer() { this->deleteData(); }
+
+	Q_DISABLE_COPY(RingBuffer);
+
+	explicit RingBuffer(RingBuffer&& other) noexcept { *this = std::move(other); }
+
+	RingBuffer& operator=(RingBuffer&& other) noexcept {
+		this->deleteData();
+		this->data = other.data;
+		this->head = other.head;
+		this->mSize = other.mSize;
+		this->mCapacity = other.mCapacity;
+		other.data = nullptr;
+		other.head = -1;
+		return *this;
+	}
+
+	// undefined if capacity is 0
+	template <typename... Args>
+	T& emplace(Args&&... args) {
+		auto i = (this->head + 1) % this->mCapacity;
+
+		if (this->indexIsAllocated(i)) {
+			this->data[i].~T();
+		}
+
+		auto* slot = &this->data[i];
+		new (&this->data[i]) T(std::forward<Args>(args)...);
+
+		this->head = i;
+		if (this->mSize != this->mCapacity) this->mSize = i + 1;
+
+		return *slot;
+	}
+
+	void clear() {
+		if (this->head == -1) return;
+
+		auto i = this->head;
+
+		do {
+			i = (i + 1) % this->mSize;
+			this->data[i].~T();
+		} while (i != this->head);
+
+		this->mSize = 0;
+		this->head = -1;
+	}
+
+	// negative indexes and >size indexes are undefined
+	[[nodiscard]] T& at(qsizetype i) {
+		auto bufferI = (this->head - i) % this->mCapacity;
+		if (bufferI < 0) bufferI += this->mCapacity;
+		return this->data[bufferI];
+	}
+
+	[[nodiscard]] const T& at(qsizetype i) const {
+		return const_cast<RingBuffer<T>*>(this)->at(i); // NOLINT
+	}
+
+	[[nodiscard]] qsizetype size() const { return this->mSize; }
+	[[nodiscard]] qsizetype capacity() const { return this->mCapacity; }
+
+private:
+	void createData() {
+		if (this->data != nullptr) return;
+		this->data =
+		    static_cast<T*>(::operator new(this->mCapacity * sizeof(T), std::align_val_t {alignof(T)}));
+	}
+
+	void deleteData() {
+		this->clear();
+		::operator delete(this->data, std::align_val_t {alignof(T)});
+		this->data = nullptr;
+	}
+
+	bool indexIsAllocated(qsizetype index) {
+		return this->mSize == this->mCapacity || index <= this->head;
+	}
+
+	T* data = nullptr;
+	qsizetype mCapacity = 0;
+	qsizetype head = -1;
+	qsizetype mSize = 0;
+};
+
+// ring buffer with the ability to look up elements by hash (single bucket)
+template <typename T>
+class HashBuffer {
+public:
+	explicit HashBuffer() = default;
+	explicit HashBuffer(qsizetype capacity): ring(capacity) {}
+	~HashBuffer() = default;
+
+	Q_DISABLE_COPY(HashBuffer);
+	explicit HashBuffer(HashBuffer&& other) noexcept: ring(other.ring) {}
+
+	HashBuffer& operator=(HashBuffer&& other) noexcept {
+		this->ring = other.ring;
+		return *this;
+	}
+
+	// returns the index of the given value or -1 if missing
+	[[nodiscard]] qsizetype indexOf(const T& value, T** slot = nullptr) {
+		auto hash = qHash(value);
+
+		for (auto i = 0; i < this->size(); i++) {
+			auto& v = this->ring.at(i);
+			if (hash == v.first && value == v.second) {
+				if (slot != nullptr) *slot = &v.second;
+				return i;
+			}
+		}
+
+		return -1;
+	}
+
+	[[nodiscard]] qsizetype indexOf(const T& value, T const** slot = nullptr) const {
+		return const_cast<HashBuffer<T>*>(this)->indexOf(value, slot); // NOLINT
+	}
+
+	template <typename... Args>
+	T& emplace(Args&&... args) {
+		auto& entry = this->ring.emplace(
+		    std::piecewise_construct,
+		    std::forward_as_tuple(0),
+		    std::forward_as_tuple(std::forward<Args>(args)...)
+		);
+
+		entry.first = qHash(entry.second);
+		return entry.second;
+	}
+
+	void clear() { this->ring.clear(); }
+
+	// negative indexes and >size indexes are undefined
+	[[nodiscard]] T& at(qsizetype i) { return this->ring.at(i).second; }
+	[[nodiscard]] const T& at(qsizetype i) const { return this->ring.at(i).second; }
+	[[nodiscard]] qsizetype size() const { return this->ring.size(); }
+	[[nodiscard]] qsizetype capacity() const { return this->ring.capacity(); }
+
+private:
+	RingBuffer<std::pair<size_t, T>> ring;
+};
+
+// NOLINTEND(cppcoreguidelines-pro-bounds-pointer-arithmetic)

src/core/test/CMakeLists.txt

@@ -6,3 +6,4 @@ endfunction()
 
 qs_test(popupwindow popupwindow.cpp)
 qs_test(transformwatcher transformwatcher.cpp)
+qs_test(ringbuffer ringbuf.cpp)

src/core/test/ringbuf.cpp

@@ -0,0 +1,125 @@
+#include "ringbuf.hpp"
+#include <utility>
+
+#include <qlogging.h>
+#include <qtest.h>
+#include <qtestcase.h>
+#include <qtypes.h>
+
+#include "../ringbuf.hpp"
+
+TestObject::TestObject(quint32* count): count(count) {
+	(*this->count)++;
+	qDebug() << "Created TestObject" << this << "- count is now" << *this->count;
+}
+
+TestObject::~TestObject() {
+	(*this->count)--;
+	qDebug() << "Destroyed TestObject" << this << "- count is now" << *this->count;
+}
+
+void TestRingBuffer::fill() {
+	quint32 counter = 0;
+	auto rb = RingBuffer<TestObject>(3);
+	QCOMPARE(rb.capacity(), 3);
+
+	qInfo() << "adding test objects";
+	auto* n1 = &rb.emplace(&counter);
+	auto* n2 = &rb.emplace(&counter);
+	auto* n3 = &rb.emplace(&counter);
+	QCOMPARE(counter, 3);
+	QCOMPARE(rb.size(), 3);
+	QCOMPARE(&rb.at(0), n3);
+	QCOMPARE(&rb.at(1), n2);
+	QCOMPARE(&rb.at(2), n1);
+
+	qInfo() << "replacing last object with new one";
+	auto* n4 = &rb.emplace(&counter);
+	QCOMPARE(counter, 3);
+	QCOMPARE(rb.size(), 3);
+	QCOMPARE(&rb.at(0), n4);
+	QCOMPARE(&rb.at(1), n3);
+	QCOMPARE(&rb.at(2), n2);
+
+	qInfo() << "replacing the rest";
+	auto* n5 = &rb.emplace(&counter);
+	auto* n6 = &rb.emplace(&counter);
+	QCOMPARE(counter, 3);
+	QCOMPARE(rb.size(), 3);
+	QCOMPARE(&rb.at(0), n6);
+	QCOMPARE(&rb.at(1), n5);
+	QCOMPARE(&rb.at(2), n4);
+
+	qInfo() << "clearing buffer";
+	rb.clear();
+	QCOMPARE(counter, 0);
+	QCOMPARE(rb.size(), 0);
+}
+
+void TestRingBuffer::clearPartial() {
+	quint32 counter = 0;
+	auto rb = RingBuffer<TestObject>(2);
+
+	qInfo() << "adding object to buffer";
+	auto* n1 = &rb.emplace(&counter);
+	QCOMPARE(counter, 1);
+	QCOMPARE(rb.size(), 1);
+	QCOMPARE(&rb.at(0), n1);
+
+	qInfo() << "clearing buffer";
+	rb.clear();
+	QCOMPARE(counter, 0);
+	QCOMPARE(rb.size(), 0);
+}
+
+void TestRingBuffer::move() {
+	quint32 counter = 0;
+
+	{
+		auto rb1 = RingBuffer<TestObject>(1);
+
+		qInfo() << "adding object to first buffer";
+		auto* n1 = &rb1.emplace(&counter);
+		QCOMPARE(counter, 1);
+		QCOMPARE(rb1.size(), 1);
+		QCOMPARE(&rb1.at(0), n1);
+
+		qInfo() << "move constructing new buffer";
+		auto rb2 = RingBuffer<TestObject>(std::move(rb1));
+		QCOMPARE(counter, 1);
+		QCOMPARE(rb2.size(), 1);
+		QCOMPARE(&rb2.at(0), n1);
+
+		qInfo() << "move assigning new buffer";
+		auto rb3 = RingBuffer<TestObject>();
+		rb3 = std::move(rb2);
+		QCOMPARE(counter, 1);
+		QCOMPARE(rb3.size(), 1);
+		QCOMPARE(&rb3.at(0), n1);
+	}
+
+	QCOMPARE(counter, 0);
+}
+
+void TestRingBuffer::hashLookup() {
+	auto hb = HashBuffer<int>(3);
+
+	qInfo() << "inserting 1,2,3 into HashBuffer";
+	hb.emplace(1);
+	hb.emplace(2);
+	hb.emplace(3);
+
+	qInfo() << "checking lookups";
+	QCOMPARE(hb.indexOf(3), 0);
+	QCOMPARE(hb.indexOf(2), 1);
+	QCOMPARE(hb.indexOf(1), 2);
+
+	qInfo() << "adding 4";
+	hb.emplace(4);
+	QCOMPARE(hb.indexOf(4), 0);
+	QCOMPARE(hb.indexOf(3), 1);
+	QCOMPARE(hb.indexOf(2), 2);
+	QCOMPARE(hb.indexOf(1), -1);
+}
+
+QTEST_MAIN(TestRingBuffer);

src/core/test/ringbuf.hpp

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <qobject.h>
+#include <qtclasshelpermacros.h>
+#include <qtmetamacros.h>
+#include <qtypes.h>
+
+class TestObject {
+public:
+	explicit TestObject(quint32* count);
+	~TestObject();
+	Q_DISABLE_COPY_MOVE(TestObject);
+
+private:
+	quint32* count;
+};
+
+class TestRingBuffer: public QObject {
+	Q_OBJECT;
+
+private slots:
+	static void fill();
+	static void clearPartial();
+	static void move();
+
+	static void hashLookup();
+};