core.d

/**
	This module contains the core functionality of the vibe framework.

	Copyright: © 2012-2013 RejectedSoftware e.K.
	License: Subject to the terms of the MIT license, as written in the included LICENSE.txt file.
	Authors: Sönke Ludwig
*/
module vibe.core.core;

public import vibe.core.driver;

import vibe.core.args;
import vibe.core.concurrency;
import vibe.core.log;
import vibe.utils.array;
import std.algorithm;
import std.conv;
import std.encoding;
import std.exception;
import std.functional;
import std.range;
import std.string;
import std.variant;
import core.sync.mutex;
import core.stdc.stdlib;
import core.thread;

version(VibeLibevDriver) import vibe.core.drivers.libev;
version(VibeLibeventDriver) import vibe.core.drivers.libevent2;
version(VibeWin32Driver) import vibe.core.drivers.win32;
version(VibeWinrtDriver) import vibe.core.drivers.winrt;

version(Posix)
{
	import core.sys.posix.signal;
	import core.sys.posix.unistd;
	import core.sys.posix.pwd;

	static if (__traits(compiles, {import core.sys.posix.grp; getgrgid(0);})) {
		import core.sys.posix.grp;
	} else {
		extern (C) {
			struct group {
				char*   gr_name;
				char*   gr_passwd;
				gid_t   gr_gid;
				char**  gr_mem;
			}
			group* getgrgid(gid_t);
			group* getgrnam(in char*);
		}
	}
}

version (Windows)
{
	import core.stdc.signal;
}


/**************************************************************************************************/
/* Public functions                                                                               */
/**************************************************************************************************/

/**
	Starts the vibe event loop.

	Note that this function is usually called automatically by the vibe framework. However, if
	you provide your own main() function, you need to call it manually.

	The event loop will continue running during the whole life time of the application.
	Tasks will be started and handled from within the event loop.
*/
int runEventLoop()
{
	s_eventLoopRunning = true;
	scope(exit) s_eventLoopRunning = false;

	// runs any yield()ed tasks first
	s_core.m_exit = false;
	s_core.notifyIdle();
	if (s_core.m_exit) return 0;

	if( auto err = getEventDriver().runEventLoop() != 0){
		if( err == 1 ){
			logDebug("No events active, exiting message loop.");
			return 0;
		}
		logError("Error running event loop: %d", err);
		return 1;
	}
	return 0;
}

/**
	Stops the currently running event loop.

	Calling this function will cause the event loop to stop event processing and
	the corresponding call to runEventLoop() will return to its caller.
*/
void exitEventLoop(bool shutdown_workers = true)
{
	assert(s_eventLoopRunning);
	if (shutdown_workers && st_workerTaskMutex) {
		synchronized (st_workerTaskMutex)
			foreach (ref ctx; st_workerThreads)
				ctx.exit = true;
		st_workerTaskSignal.emit();
		while (true) {
			synchronized (st_workerTaskMutex)
				if (st_workerThreads.length == 0)
					break;
			st_workerTaskSignal.wait();
		}
	}
	getEventDriver().exitEventLoop();
}

/**
	Process all pending events without blocking.

	Checks if events are ready to trigger immediately, and run their callbacks if so.

	Returns: Returns false iff exitEventLoop was called in the process.
*/
bool processEvents()
{
	return getEventDriver().processEvents();
}

/**
	Sets a callback that is called whenever no events are left in the event queue.

	The callback delegate is called whenever all events in the event queue have been
	processed. Returning true from the callback will cause another idle event to
	be triggered immediately after processing any events that have arrived in the
	meantime. Returning fals will instead wait until another event has arrived first.
*/
void setIdleHandler(void delegate() del)
{
	s_idleHandler = { del(); return false; };
}
/// ditto
void setIdleHandler(bool delegate() del)
{
	s_idleHandler = del;
}

/**
	Runs a new asynchronous task.

	task will be called synchronously from within the vibeRunTask call. It will
	continue to run until vibeYield() or any of the I/O or wait functions is
	called.
*/
Task runTask(void delegate() task)
{
	CoreTask f;
	while (s_availableFibersCount > 0) {
		// pick the first available fiber
		f = s_availableFibers[--s_availableFibersCount];
		if (f.state == Fiber.State.TERM) {
			f = null;
			continue;
		}
	}

	if (f is null) {
		// if there is no fiber available, create one.
		if( s_availableFibers.length == 0 ) s_availableFibers.length = 1024;
		logDebug("Creating new fiber...");
		s_fiberCount++;
		f = new CoreTask;
	}
	
	f.m_taskFunc = task;
	f.m_taskCounter++;
	auto handle = f.task();
	logTrace("initial task call (%s)", f.state);
	debug if (s_taskEventCallback) s_taskEventCallback(TaskEvent.preStart);
	s_core.resumeTask(handle, null, true);
	logTrace("run task out");
	return handle;
}

/**
	Runs a new asynchronous task in a worker thread.

	Only function pointers with weakly isolated arguments are allowed to be
	able to guarantee thread-safety.
*/
void runWorkerTask(R, ARGS...)(R function(ARGS) func, ARGS args)
{
	foreach (T; ARGS) static assert(isWeaklyIsolated!T, "Argument type "~T.stringof~" is not safe to pass between threads.");
	runWorkerTask_unsafe({ func(args); });
}
/// ditto
void runWorkerTask(alias method, T, ARGS...)(shared(T) object, ARGS args)
{
	foreach (T; ARGS) static assert(isWeaklyIsolated!T, "Argument type "~T.stringof~" is not safe to pass between threads.");
	runWorkerTask_unsafe({ object.method(args); });
}

private void runWorkerTask_unsafe(void delegate() del)
{
	if (st_workerTaskMutex) {
		synchronized (st_workerTaskMutex) {
			st_workerTasks ~= del;
		}
		st_workerTaskSignal.emit();
	} else {
		runTask(del);
	}
}

/**
	Runs a new asynchronous task in all worker threads concurrently.

	This function is mainly useful for long-living tasks that distribute their
	work across all CPU cores. Only function pointers with weakly isolated
	arguments are allowed to be able to guarantee thread-safety.
*/
void runWorkerTaskDist(R, ARGS...)(R function(ARGS) func, ARGS args)
{
	foreach (T; ARGS) static assert(isWeaklyIsolated!T, "Argument type "~T.stringof~" is not safe to pass between threads.");
	runWorkerTaskDist_unsafe({ func(args); });
}
/// ditto
void runWorkerTaskDist(alias method, T, ARGS...)(shared(T) object, ARGS args)
{
	foreach (T; ARGS) static assert(isWeaklyIsolated!T, "Argument type "~T.stringof~" is not safe to pass between threads.");
	runWorkerTaskDist_unsafe({ object.method(args); });
}

private void runWorkerTaskDist_unsafe(void delegate() del)
{
	if (st_workerTaskMutex) {
		synchronized (st_workerTaskMutex) {
			foreach (ref ctx; st_workerThreads)
				ctx.taskQueue ~= del;
		}
		st_workerTaskSignal.emit();
	} else {
		runTask(del);
	}
}

/**
	Suspends the execution of the calling task to let other tasks and events be
	handled.
	
	Calling this function in short intervals is recommended if long CPU
	computations are carried out by a task. It can also be used in conjunction
	with Signals to implement cross-fiber events with no polling.
*/
void yield()
{
	s_yieldedTasks ~= Task.getThis();
	rawYield();
}


/**
	Yields execution of this task until an event wakes it up again.

	Beware that the task will starve if no event wakes it up.
*/
void rawYield()
{
	s_core.yieldForEvent();
}

/**
	Suspends the execution of the calling task for the specified amount of time.
*/
void sleep(Duration timeout)
{
	auto tm = getEventDriver().createTimer(null);
	tm.rearm(timeout);
	tm.wait();
}


/**
	Returns a new armed timer.

	Params:
		timeout = Determines the minimum amount of time that elapses before the timer fires.
		callback = This delegate will be called when the timer fires
		periodic = Speficies if the timer fires repeatedly or only once

	Returns:
		Returns a Timer object that can be used to identify and modify the timer.
*/
Timer setTimer(Duration timeout, void delegate() callback, bool periodic = false)
{
	auto tm = getEventDriver().createTimer(callback);
	tm.rearm(timeout, periodic);
	return tm;
}

/**
	Creates a new timer without arming it.
*/
Timer createTimer(void delegate() callback)
{
	return getEventDriver().createTimer(callback);
}

/**
	Sets a variable specific to the calling task/fiber.

	Remarks:
		This function also works if called from outside if a fiber. In this case, it will work
		on a thread local storage.
*/
void setTaskLocal(T)(string name, T value)
{
	auto self = cast(CoreTask)Fiber.getThis();
	if( self ) self.set(name, value);
	s_taskLocalStorageGlobal[name] = Variant(value);
}

/**
	Returns a task/fiber specific variable.

	Remarks:
		This function also works if called from outside if a fiber. In this case, it will work
		on a thread local storage.
*/
T getTaskLocal(T)(string name)
{
	auto self = cast(CoreTask)Fiber.getThis();
	if( self ) return self.get!T(name);
	auto pvar = name in s_taskLocalStorageGlobal;
	enforce(pvar !is null, "Accessing unset TLS variable '"~name~"'.");
	return pvar.get!T();
}

/**
	Returns a task/fiber specific variable.

	Remarks:
		This function also works if called from outside if a fiber. In this case, it will work
		on a thread local storage.
*/
bool isTaskLocalSet(string name)
{
	auto self = cast(CoreTask)Fiber.getThis();
	if( self ) return self.isSet(name);
	return (name in s_taskLocalStorageGlobal) !is null;
}

/**
	Sets the stack size for tasks.

	The default stack size is set to 16 KiB, which is sufficient for most tasks. Tuning this value
	can be used to reduce memory usage for great numbers of concurrent tasks or to allow applications
	with heavy stack use.

	Note that this function must be called before any task is started to have an effect.
*/
void setTaskStackSize(size_t sz)
{
	s_taskStackSize = sz;
}

/**
	Enables multithreaded worker task processing.

	This function will start up a number of worker threads that will process tasks started using
	runWorkerTask(). runTask() will still execute tasks on the calling thread.

	Note that this functionality is experimental right now and is not recommended for general use.
*/
void enableWorkerThreads()
{
	import core.cpuid;

	setupDriver();

	assert(st_workerTaskMutex is null);

	st_workerTaskMutex = new core.sync.mutex.Mutex;	

	st_workerTaskSignal = getEventDriver().createManualEvent();

	foreach (i; 0 .. threadsPerCPU) {
		auto thr = new Thread(&workerThreadFunc);
		thr.name = format("Vibe Task Worker #%s", i);
		st_workerThreads[thr] = WorkerThreadContext();
		thr.start();
	}
}


/**
	Sets the effective user and group ID to the ones configured for privilege lowering.

	This function is useful for services run as root to give up on the privileges that
	they only need for initialization (such as listening on ports <= 1024 or opening
	system log files).
*/
void lowerPrivileges()
{
	if (!isRoot()) return;
	auto uname = s_privilegeLoweringUserName;
	auto gname = s_privilegeLoweringGroupName;
	if (uname || gname) {
		static bool tryParse(T)(string s, out T n)
		{
			import std.conv, std.ascii;
			if (!isDigit(s[0])) return false;
			n = parse!T(s);
			return s.length==0;
		}
		int uid = -1, gid = -1;
		if (uname && !tryParse(uname, uid)) uid = getUID(uname);
		if (gname && !tryParse(gname, gid)) gid = getGID(gname);
		setUID(uid, gid);
	} else logWarn("Vibe was run as root, and no user/group has been specified for privilege lowering. Running with full permissions.");
}


/**
	Sets a callback that is invoked whenever a task changes its status.

	This function is useful mostly for implementing debuggers that
	analyze the life time of tasks, including task switches.
*/
void setTaskEventCallback(void function(TaskEvent) func)
{
	s_taskEventCallback = func;
}


/**
	A version string representing the current vibe version
*/
enum VibeVersionString = "0.7.16";


/**
	Implements a task local storage variable.

	Task local variables, similar to thread local variables, exist separately
	in each task. Consequently, they do not need any form of synchronization
	when accessing them.

	Note, however, that each TaskLocal variable will increase the memory footprint
	of any task that uses task local storage. There is also an overhead to access
	TaskLocal variables, higher than for thread local variables, but generelly
	still O(n).

	Notice:
		FiberLocal instances MUST be declared as static/global thread-local
		variables. Defining them as a temporary/stack variable will cause
		crashes or data corruption!

	Examples:
		---
		TaskLocal!string s_myString = "world";

		void taskFunc()
		{
			assert(s_myString == "world");
			s_myString = "hello";
			assert(s_myString == "hello");
		}

		shared static this()
		{
			// both tasks will get independent storage for s_myString
			runTask(&taskFunc);
			runTask(&taskFunc);
		}
		---
*/
struct TaskLocal(T)
{
	private {
		size_t m_offset = size_t.max;
		size_t m_id;
		T m_initValue;
	}

	this(T init_val) { m_initValue = init_val; }

	@disable this(this);

	void opAssign(bool value) { this.storage = value; }

	@property ref T storage()
	{
		auto fiber = cast(CoreTask)Fiber.getThis();

		// lazily register in FLS storage
		if (m_offset == size_t.max) {
			// TODO: handle alignment properly
			m_offset = CoreTask.ms_flsFill;
			m_id = CoreTask.ms_flsCounter++;
			CoreTask.ms_flsFill += T.sizeof;
		}

		// make sure the current fiber has enough FLS storage
		if (fiber.m_fls.length < CoreTask.ms_flsFill) {
			fiber.m_fls.length = CoreTask.ms_flsFill + 128;
			fiber.m_flsInit.length = CoreTask.ms_flsCounter + 64;
		}
		
		// return (possibly default initialized) value
		auto data = fiber.m_fls.ptr[m_offset .. m_offset+T.sizeof];
		if (!fiber.m_flsInit[m_id]) {
			fiber.m_flsInit[m_id] = true;
			emplace!T(data, m_initValue);
		}
		return (cast(T[])data)[0];
	}

	alias storage this;
}


/**
	High level state change events for a Task
*/
enum TaskEvent {
	preStart, /// Just about to invoke the fiber which starts execution
	start,    /// Just about to start execution
	yield,    /// Temporarily paused
	resume,   /// Resumed from a prior yield
	end,      /// Ended normally
	fail      /// Ended with an exception
}


/**************************************************************************************************/
/* private types                                                                                  */
/**************************************************************************************************/

private class CoreTask : TaskFiber {
	import std.bitmanip;
	private {
		void delegate() m_taskFunc;
		Exception m_exception;
		Task[] m_yielders;

		// task local storage
		static size_t ms_flsFill = 0; // thread-local
		static size_t ms_flsCounter = 0;
		BitArray m_flsInit;
		void[] m_fls;
	}

	this()
	{
		super(&run, s_taskStackSize);
	}

	private void run()
	{
		try {
			while(true){
				while( !m_taskFunc ){
					try {
						s_core.yieldForEvent();
					} catch( Exception e ){
						logWarn("CoreTaskFiber was resumed with exception but without active task!");
						logDiagnostic("Full error: %s", e.toString().sanitize());
					}
				}

				auto task = m_taskFunc;
				m_taskFunc = null;
				try {
					m_running = true;
					scope(exit) m_running = false;
					logTrace("entering task.");
					debug if (s_taskEventCallback) s_taskEventCallback(TaskEvent.start);
					task();
					debug if (s_taskEventCallback) s_taskEventCallback(TaskEvent.end);
					logTrace("exiting task.");
				} catch( Exception e ){
					debug if (s_taskEventCallback) s_taskEventCallback(TaskEvent.fail);
					import std.encoding;
					logCritical("Task terminated with uncaught exception: %s", e.msg);
					logDebug("Full error: %s", e.toString().sanitize());
				}
				resetLocalStorage();

				s_yieldedTasks ~= m_yielders;
				m_yielders.length = 0;
				
				// make the fiber available for the next task
				if( s_availableFibers.length <= s_availableFibersCount )
					s_availableFibers.length = 2*s_availableFibers.length;
				s_availableFibers[s_availableFibersCount++] = this;

				rawYield();
			}
		} catch(Throwable th){
			logCritical("CoreTaskFiber was terminated unexpectedly: %s", th.msg);
			logDiagnostic("Full error: %s", th.toString().sanitize());
		}
	}

	override void join()
	{
		auto caller = Task.getThis();
		assert(caller.fiber !is this, "A task cannot join itself.");
		assert(caller.thread is this.thread, "Joining tasks in foreign threads is currently not supported.");
		m_yielders ~= caller;
		auto run_count = m_taskCounter;
		if (m_running && run_count == m_taskCounter) {
			s_core.resumeTask(this.task);
			while (m_running && run_count == m_taskCounter) rawYield();
		}
	}

	override void interrupt()
	{
		auto caller = Task.getThis();
		assert(caller != this.task, "A task cannot interrupt itself.");
		assert(caller.thread is this.thread, "Interrupting tasks in different threads is not yet supported.");
		s_core.resumeTask(this.task, new InterruptException);
	}

	override void terminate()
	{
		assert(false, "Not implemented");
	}
}


private class VibeDriverCore : DriverCore {
	private {
		Duration m_gcCollectTimeout;
		Timer m_gcTimer;
		bool m_ignoreIdleForGC = false;
		bool m_exit = false;
	}

	private void setupGcTimer()
	{
		m_gcTimer = getEventDriver().createTimer(&collectGarbage);
		m_gcCollectTimeout = dur!"seconds"(2);
	}

	void yieldForEvent()
	{
		auto fiber = cast(CoreTask)Fiber.getThis();
		if( fiber ){
			logTrace("yield");
			debug if (s_taskEventCallback) s_taskEventCallback(TaskEvent.yield);
			Fiber.yield();
			debug if (s_taskEventCallback) s_taskEventCallback(TaskEvent.resume);
			logTrace("resume");
			auto e = fiber.m_exception;
			if( e ){
				fiber.m_exception = null;
				throw e;
			}
		} else {
			assert(!s_eventLoopRunning, "Event processing outside of a fiber should only happen before the event loop is running!?");
			if( auto err = getEventDriver().runEventLoopOnce() ){
				if( err == 1 ){
					logDebug("No events registered, exiting event loop.");
					throw new Exception("No events registered in vibeYieldForEvent.");
				}
				logError("Error running event loop: %d", err);
				throw new Exception("Error waiting for events.");
			}
		}
	}

	void resumeTask(Task task, Exception event_exception = null)
	{
		resumeTask(task, event_exception, false);
	}

	void resumeTask(Task task, Exception event_exception, bool initial_resume)
	{
		assert(initial_resume || task.running, "Resuming terminated task.");
		CoreTask ctask = cast(CoreTask)task.fiber;
		assert(ctask.thread is Thread.getThis(), "Resuming task in foreign thread.");
		assert(ctask.state == Fiber.State.HOLD, "Resuming fiber that is " ~ to!string(ctask.state));

		if( event_exception ){
			extrap();
			ctask.m_exception = event_exception;
		}
		
		auto uncaught_exception = task.call(false);
		if( uncaught_exception ){
			extrap();
			assert(task.state == Fiber.State.TERM);
			logError("Task terminated with unhandled exception: %s", uncaught_exception.toString());
		}
	}

	void notifyIdle()
	{
		bool again = true;
		while (again) {
			if (s_idleHandler)
				again = s_idleHandler();
			else again = false;

			Task[] tmp;
			swap(s_yieldedTasks, tmp);
			foreach(t; tmp)
				if (t.running)
					resumeTask(t);
			if (s_yieldedTasks.length > 0)
				again = true;
			if (again)
				if (!processEvents()) {
					m_exit = true;
					return;
				}
		}

		if( !m_ignoreIdleForGC && m_gcTimer ){
			m_gcTimer.rearm(m_gcCollectTimeout);
		} else m_ignoreIdleForGC = false;
	}

	private void collectGarbage()
	{
		import core.memory;
		logTrace("gc idle collect");
		GC.collect();
		GC.minimize();
		m_ignoreIdleForGC = true;
	}
}

private struct WorkerThreadContext {
	void delegate()[] taskQueue;
	bool exit = false;
}

/**************************************************************************************************/
/* private functions                                                                              */
/**************************************************************************************************/

private {
	__gshared VibeDriverCore s_core;
	__gshared size_t s_taskStackSize = 16*4096;

	__gshared core.sync.mutex.Mutex st_workerTaskMutex;
	__gshared void delegate()[] st_workerTasks;
	__gshared WorkerThreadContext[Thread] st_workerThreads;
	__gshared ManualEvent st_workerTaskSignal;

	bool delegate() s_idleHandler;
	__gshared debug void function(TaskEvent) s_taskEventCallback;
	Task[] s_yieldedTasks;
	bool s_eventLoopRunning = false;
	Variant[string] s_taskLocalStorageGlobal; // for use outside of a task
	CoreTask[] s_availableFibers;
	size_t s_availableFibersCount;
	size_t s_fiberCount;

	string s_privilegeLoweringUserName;
	string s_privilegeLoweringGroupName;
}

// per process setup
shared static this()
{
	version(Windows){
		version(VibeLibeventDriver) enum need_wsa = true;
		else version(VibeWin32Driver) enum need_wsa = true;
		else enum need_wsa = false;
		static if (need_wsa) {
			logTrace("init winsock");
			// initialize WinSock2
			import std.c.windows.winsock;
			WSADATA data;
			WSAStartup(0x0202, &data);

		}
	}

	initializeLogModule();
	
	logTrace("create driver core");
	
	s_core = new VibeDriverCore;

	version(Posix){
		logTrace("setup signal handler");
		// support proper shutdown using signals
		sigset_t sigset;
		sigemptyset(&sigset);
		sigaction_t siginfo;
		siginfo.sa_handler = &onSignal;
		siginfo.sa_mask = sigset;
		siginfo.sa_flags = SA_RESTART;
		sigaction(SIGINT, &siginfo, null);
		sigaction(SIGTERM, &siginfo, null);

		siginfo.sa_handler = &onBrokenPipe;
		sigaction(SIGPIPE, &siginfo, null);
	}

	version(Windows){
		signal(SIGABRT, &onSignal);
		signal(SIGTERM, &onSignal);
		signal(SIGINT, &onSignal);
	}

	setupDriver();

	version(VibeIdleCollect){
		logTrace("setup gc");
		s_core.setupGcTimer();
	}

	getOption("uid|user", &s_privilegeLoweringUserName, "Sets the user name or id used for privilege lowering.");
	getOption("gid|group", &s_privilegeLoweringGroupName, "Sets the group name or id used for privilege lowering.");
}

shared static ~this()
{
	bool tasks_left = false;

	if(st_workerTaskMutex !is null) { //This mutex is experimentally in enableWorkerThreads
		synchronized(st_workerTaskMutex){ 
			if( !st_workerTasks.empty ) tasks_left = true;
		}	
	} else {
		if( !st_workerTasks.empty ) tasks_left = true;
	}

	
	if( !s_yieldedTasks.empty ) tasks_left = true;
	if( tasks_left ) logWarn("There are still tasks running at exit.");

	delete s_core;
}

// per thread setup
static this()
{
	assert(s_core !is null);

	setupDriver();
}

static ~this()
{
	deleteEventDriver();
}

private void setupDriver()
{
	if( getEventDriver() !is null ) return;

	logTrace("create driver");
	version(VibeWin32Driver) setEventDriver(new Win32EventDriver(s_core));
	else version(VibeWinrtDriver) setEventDriver(new WinRTEventDriver(s_core));
	else version(VibeLibevDriver) setEventDriver(new LibevDriver(s_core));
	else version(VibeLibeventDriver) setEventDriver(new Libevent2Driver(s_core));
	else static assert(false, "No event driver is available. Please specify a -version=Vibe*Driver for the desired driver.");
	logTrace("driver %s created", (cast(Object)getEventDriver()).classinfo.name);
}

private void workerThreadFunc()
{
	logDebug("entering worker thread");
	runTask(toDelegate(&handleWorkerTasks));
	logDebug("running event loop");
	runEventLoop();
}

private void handleWorkerTasks()
{
	logDebug("worker task enter");
	yield();

	auto thisthr = Thread.getThis();

	logDebug("worker task loop enter");
	while(true){
		void delegate() t;
		auto emit_count = st_workerTaskSignal.emitCount;
		synchronized(st_workerTaskMutex){
			logDebug("worker task check");
			if (st_workerThreads[thisthr].exit) {
				if (st_workerThreads[thisthr].taskQueue.length > 0)
					logWarn("Worker thread shuts down with specific worker tasks left in its queue.");
				if (st_workerThreads.length == 1 && st_workerTasks.length > 0)
					logWarn("Worker threads shut down with worker tasks still left in the queue.");
				st_workerThreads.remove(thisthr);
				getEventDriver().exitEventLoop();
				break;
			}
			if (!st_workerTasks.empty) {
				logDebug("worker task got");
				t = st_workerTasks.front;
				st_workerTasks.popFront();
			} else if (!st_workerThreads[thisthr].taskQueue.empty) {
				logDebug("worker task got specific");
				t = st_workerThreads[thisthr].taskQueue.front;
				st_workerThreads[thisthr].taskQueue.popFront();
			}
		}
		if (t) runTask(t);
		else st_workerTaskSignal.wait(emit_count);
	}
	logDebug("worker task exit");
	synchronized(st_workerTaskMutex)
		st_workerThreads.remove(thisthr);
	st_workerTaskSignal.emit();
}


private extern(C) void extrap()
nothrow {
	logTrace("exception trap");
}

private extern(C) void onSignal(int signal)
nothrow {
	logInfo("Received signal %d. Shutting down.", signal);

	if( s_eventLoopRunning ) try exitEventLoop(); catch(Exception e) {}
	else exit(1);
}

private extern(C) void onBrokenPipe(int signal)
nothrow {
	logTrace("Broken pipe.");
}

version(Posix)
{
	private bool isRoot() { return geteuid() == 0; }

	private void setUID(int uid, int gid)
	{
		logInfo("Lowering privileges to uid=%d, gid=%d...", uid, gid);
		if (gid >= 0) {
			enforce(getgrgid(gid) !is null, "Invalid group id!");
			enforce(setegid(gid) == 0, "Error setting group id!");
		}
		//if( initgroups(const char *user, gid_t group);
		if (uid >= 0) {
			enforce(getpwuid(uid) !is null, "Invalid user id!");
			enforce(seteuid(uid) == 0, "Error setting user id!");
		}
	}

	private int getUID(string name)
	{
		auto pw = getpwnam(name.toStringz());
		enforce(pw !is null, "Unknown user name: "~name);
		return pw.pw_uid;
	}

	private int getGID(string name)
	{
		auto gr = getgrnam(name.toStringz());
		enforce(gr !is null, "Unknown group name: "~name);
		return gr.gr_gid;
	}
} else version(Windows){
	private bool isRoot() { return false; }

	private void setUID(int uid, int gid)
	{
		enforce(false, "UID/GID not supported on Windows.");
	}

	private int getUID(string name)
	{
		enforce(false, "Privilege lowering not supported on Windows.");
		assert(false);
	}

	private int getGID(string name)
	{
		enforce(false, "Privilege lowering not supported on Windows.");
		assert(false);
	}
}