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.::pth(3)		    pthsem Portable Threads		     .::pth(3)

NAME
       pthsem -	GNU Portable Threads

VERSION
       pthsem 2.0.8 based on GNU Pth

SYNOPSIS
       Global Library Management
	   pth_init, pth_kill, pth_ctrl, pth_version.

       Thread Attribute	Handling
	   pth_attr_of,	pth_attr_new, pth_attr_init, pth_attr_set,
	   pth_attr_get, pth_attr_destroy.

       Thread Control
	   pth_spawn, pth_once,	pth_self, pth_suspend, pth_resume, pth_yield,
	   pth_nap, pth_wait, pth_cancel, pth_abort, pth_raise,	pth_join,
	   pth_exit.

       Utilities
	   pth_fdmode, pth_time, pth_timeout, pth_int_time, pth_sfiodisc.

       Cancellation Management
	   pth_cancel_point, pth_cancel_state.

       Event Handling
	   pth_event, pth_event_typeof,	pth_event_extract, pth_event_concat,
	   pth_event_isolate, pth_event_walk, pth_event_status,
	   pth_event_free.

       Key-Based Storage
	   pth_key_create, pth_key_delete, pth_key_setdata, pth_key_getdata.

       Message Port Communication
	   pth_msgport_create, pth_msgport_destroy, pth_msgport_find,
	   pth_msgport_pending,	pth_msgport_put, pth_msgport_get,
	   pth_msgport_reply.

       Thread Cleanups
	   pth_cleanup_push, pth_cleanup_pop.

       Process Forking
	   pth_atfork_push, pth_atfork_pop, pth_fork.

       Synchronization
	   pth_mutex_init, pth_mutex_acquire, pth_mutex_release,
	   pth_rwlock_init, pth_rwlock_acquire,	pth_rwlock_release,
	   pth_cond_init, pth_cond_await, pth_cond_notify, pth_barrier_init,
	   pth_barrier_reach.

       Semaphore support
	   pth_sem_init, pth_sem_dec, pth_sem_dec_value, pth_sem_inc,
	   pth_sem_inc_value, pth_sem_set_value, pth_sem_get_value.

       User-Space Context
	   pth_uctx_create, pth_uctx_make, pth_uctx_switch, pth_uctx_destroy.

       Generalized POSIX Replacement API
	   pth_sigwait_ev, pth_accept_ev, pth_connect_ev, pth_select_ev,
	   pth_poll_ev,	pth_read_ev, pth_readv_ev, pth_write_ev,
	   pth_writev_ev, pth_recv_ev, pth_recvfrom_ev,	pth_send_ev,
	   pth_sendto_ev.

       Standard	POSIX Replacement API
	   pth_nanosleep, pth_usleep, pth_sleep, pth_waitpid, pth_system,
	   pth_sigmask,	pth_sigwait, pth_accept, pth_connect, pth_select,
	   pth_pselect,	pth_poll, pth_read, pth_readv, pth_write, pth_writev,
	   pth_pread, pth_pwrite, pth_recv, pth_recvfrom, pth_send,
	   pth_sendto.

DESCRIPTION
	 ____  _   _
	|  _ \|	|_| |__
	| |_) |	__| '_ \	 ``Only	those who attempt
	|  __/|	|_| | |	|	   the absurd can achieve
	|_|    \__|_| |_|	   the impossible.''

       Pth is a	very portable POSIX/ANSI-C based library for Unix platforms
       which provides non-preemptive priority-based scheduling for multiple
       threads of execution (aka `multithreading') inside event-driven
       applications. All threads run in	the same address space of the
       application process, but	each thread has	its own	individual program
       counter,	run-time stack,	signal mask and	"errno"	variable.

       The thread scheduling itself is done in a cooperative way, i.e.,	the
       threads are managed and dispatched by a priority- and event-driven non-
       preemptive scheduler. The intention is that this	way both better
       portability and run-time	performance is achieved	than with preemptive
       scheduling. The event facility allows threads to	wait until various
       types of	internal and external events occur, including pending I/O on
       file descriptors, asynchronous signals, elapsed timers, pending I/O on
       message ports, thread and process termination, and even results of
       customized callback functions.

       Pth also	provides an optional emulation API for POSIX.1c	threads
       (`Pthreads') which can be used for backward compatibility to existing
       multithreaded applications. See Pth's pthread(3)	manual page for
       details.

   Threading Background
       When programming	event-driven applications, usually servers, lots of
       regular jobs and	one-shot requests have to be processed in parallel.
       To efficiently simulate this parallel processing	on uniprocessor
       machines, we use	`multitasking' -- that is, we have the application ask
       the operating system to spawn multiple instances	of itself. On Unix,
       typically the kernel implements multitasking in a preemptive and
       priority-based way through heavy-weight processes spawned with fork(2).
       These processes usually do not share a common address space. Instead
       they are	clearly	separated from each other, and are created by direct
       cloning a process address space (although modern	kernels	use memory
       segment mapping and copy-on-write semantics to avoid unnecessary
       copying of physical memory).

       The drawbacks are obvious: Sharing data between the processes is
       complicated, and	can usually only be done efficiently through shared
       memory (but which itself	is not very portable). Synchronization is
       complicated because of the preemptive nature of the Unix	scheduler (one
       has to use atomic locks,	etc). The machine's resources can be exhausted
       very quickly when the server application	has to serve too many long-
       running requests	(heavy-weight processes	cost memory). And when each
       request spawns a	sub-process to handle it, the server performance and
       responsiveness is horrible (heavy-weight	processes cost time to spawn).
       Finally,	the server application doesn't scale very well with the	load
       because of these	resource problems. In practice,	lots of	tricks are
       usually used to overcome	these problems - ranging from pre-forked sub-
       process pools to	semi-serialized	processing, etc.

       One of the most elegant ways to solve these resource- and data-sharing
       problems	is to have multiple light-weight threads of execution inside a
       single (heavy-weight) process, i.e., to use multithreading.  Those
       threads usually improve responsiveness and performance of the
       application, often improve and simplify the internal program structure,
       and most	important, require less	system resources than heavy-weight
       processes. Threads are neither the optimal run-time facility for	all
       types of	applications, nor can all applications benefit from them. But
       at least	event-driven server applications usually benefit greatly from
       using threads.

   The World of	Threading
       Even though lots	of documents exists which describe and define the
       world of	threading, to understand Pth, you need only basic knowledge
       about threading.	The following definitions of thread-related terms
       should at least help you	understand thread programming enough to	allow
       you to use Pth.

       o process vs. thread
	 A process on Unix systems consists of at least	the following
	 fundamental ingredients: virtual memory table,	program	code, program
	 counter, heap memory, stack memory, stack pointer, file descriptor
	 set, signal table. On every process switch, the kernel	saves and
	 restores these	ingredients for	the individual processes. On the other
	 hand, a thread	consists of only a private program counter, stack
	 memory, stack pointer and signal table. All other ingredients,	in
	 particular the	virtual	memory,	it shares with the other threads of
	 the same process.

       o kernel-space vs. user-space threading
	 Threads on a Unix platform traditionally can be implemented either
	 inside	kernel-space or	user-space. When threads are implemented by
	 the kernel, the thread	context	switches are performed by the kernel
	 without the application's knowledge. Similarly, when threads are
	 implemented in	user-space, the	thread context switches	are performed
	 by an application library, without the	kernel's knowledge. There also
	 are hybrid threading approaches where,	typically, a user-space
	 library binds one or more user-space threads to one or	more kernel-
	 space threads (there usually called light-weight processes - or in
	 short LWPs).

	 User-space threads are	usually	more portable and can perform faster
	 and cheaper context switches (for instance via	swapcontext(2) or
	 setjmp(3)/longjmp(3)) than kernel based threads. On the other hand,
	 kernel-space threads can take advantage of multiprocessor machines
	 and don't have	any inherent I/O blocking problems. Kernel-space
	 threads are usually scheduled in preemptive way side-by-side with the
	 underlying processes. User-space threads on the other hand use	either
	 preemptive or non-preemptive scheduling.

       o preemptive vs.	non-preemptive thread scheduling
	 In preemptive scheduling, the scheduler lets a	thread execute until a
	 blocking situation occurs (usually a function call which would	block)
	 or the	assigned timeslice elapses. Then it detracts control from the
	 thread	without	a chance for the thread	to object. This	is usually
	 realized by interrupting the thread through a hardware	interrupt
	 signal	(for kernel-space threads) or a	software interrupt signal (for
	 user-space threads), like "SIGALRM" or	"SIGVTALRM". In	non-preemptive
	 scheduling, once a thread received control from the scheduler it
	 keeps it until	either a blocking situation occurs (again a function
	 call which would block	and instead switches back to the scheduler) or
	 the thread explicitly yields control back to the scheduler in a
	 cooperative way.

       o concurrency vs. parallelism
	 Concurrency exists when at least two threads are in progress at the
	 same time. Parallelism	arises when at least two threads are executing
	 simultaneously. Real parallelism can be only achieved on
	 multiprocessor	machines, of course. But one also usually speaks of
	 parallelism or	high concurrency in the	context	of preemptive thread
	 scheduling and	of low concurrency in the context of non-preemptive
	 thread	scheduling.

       o responsiveness
	 The responsiveness of a system	can be described by the	user visible
	 delay until the system	responses to an	external request. When this
	 delay is small	enough and the user doesn't recognize a	noticeable
	 delay,	the responsiveness of the system is considered good. When the
	 user recognizes or is even annoyed by the delay, the responsiveness
	 of the	system is considered bad.

       o reentrant, thread-safe	and asynchronous-safe functions
	 A reentrant function is one that behaves correctly if it is called
	 simultaneously	by several threads and then also executes
	 simultaneously.  Functions that access	global state, such as memory
	 or files, of course, need to be carefully designed in order to	be
	 reentrant. Two	traditional approaches to solve	these problems are
	 caller-supplied states	and thread-specific data.

	 Thread-safety is the avoidance	of data	races, i.e., situations	in
	 which data is set to either correct or	incorrect value	depending upon
	 the (unpredictable) order in which multiple threads access and	modify
	 the data. So a	function is thread-safe	when it	still behaves
	 semantically correct when called simultaneously by several threads
	 (it is	not required that the functions	also execute simultaneously).
	 The traditional approach to achieve thread-safety is to wrap a
	 function body with an internal	mutual exclusion lock (aka `mutex').
	 As you	should recognize, reentrant is a stronger attribute than
	 thread-safe, because it is harder to achieve and results especially
	 in no run-time	contention between threads. So,	a reentrant function
	 is always thread-safe,	but not	vice versa.

	 Additionally there is a related attribute for functions named
	 asynchronous-safe, which comes	into play in conjunction with signal
	 handlers. This	is very	related	to the problem of reentrant functions.
	 An asynchronous-safe function is one that can be called safe and
	 without side-effects from within a signal handler context. Usually
	 very few functions are	of this	type, because an application is	very
	 restricted in what it can perform from	within a signal	handler
	 (especially what system functions it is allowed to call). The reason
	 mainly	is, because only a few system functions	are officially
	 declared by POSIX as guaranteed to be asynchronous-safe.
	 Asynchronous-safe functions usually have to be	already	reentrant.

   User-Space Threads
       User-space threads can be implemented in	various	way. The two
       traditional approaches are:

       1. Matrix-based explicit	dispatching between small units	of execution:

	  Here the global procedures of	the application	are split into small
	  execution units (each	is required to not run for more	than a few
	  milliseconds)	and those units	are implemented	by separate functions.
	  Then a global	matrix is defined which	describes the execution	(and
	  perhaps even dependency) order of these functions. The main server
	  procedure then just dispatches between these units by	calling	one
	  function after each other controlled by this matrix. The threads are
	  created by more than one jump-trail through this matrix and by
	  switching between these jump-trails controlled by corresponding
	  occurred events.

	  This approach	gives the best possible	performance, because one can
	  fine-tune the	threads	of execution by	adjusting the matrix, and the
	  scheduling is	done explicitly	by the application itself. It is also
	  very portable, because the matrix is just an ordinary	data
	  structure, and functions are a standard feature of ANSI C.

	  The disadvantage of this approach is that it is complicated to write
	  large	applications with this approach, because in those applications
	  one quickly gets hundreds(!) of execution units and the control flow
	  inside such an application is	very hard to understand	(because it is
	  interrupted by function borders and one always has to	remember the
	  global dispatching matrix to follow it). Additionally, all threads
	  operate on the same execution	stack. Although	this saves memory, it
	  is often nasty, because one cannot switch between threads in the
	  middle of a function.	Thus the scheduling borders are	the function
	  borders.

       2. Context-based	implicit scheduling between threads of execution:

	  Here the idea	is that	one programs the application as	with forked
	  processes, i.e., one spawns a	thread of execution and	this runs from
	  the begin to the end without an interrupted control flow. But	the
	  control flow can be still interrupted	- even in the middle of	a
	  function.  Actually in a preemptive way, similar to what the kernel
	  does for the heavy-weight processes, i.e., every few milliseconds
	  the user-space scheduler switches between the	threads	of execution.
	  But the thread itself	doesn't	recognize this and usually (except for
	  synchronization issues) doesn't have to care about this.

	  The advantage	of this	approach is that it's very easy	to program,
	  because the control flow and context of a thread directly follows a
	  procedure without forced interrupts through function borders.
	  Additionally,	the programming	is very	similar	to a traditional and
	  well understood fork(2) based	approach.

	  The disadvantage is that although the	general	performance is
	  increased, compared to using approaches based	on heavy-weight
	  processes, it	is decreased compared to the matrix-approach above.
	  Because the implicit preemptive scheduling does usually a lot	more
	  context switches (every user-space context switch costs some
	  overhead even	when it	is a lot cheaper than a	kernel-level context
	  switch) than the explicit cooperative/non-preemptive scheduling.
	  Finally, there is no really portable POSIX/ANSI-C based way to
	  implement user-space preemptive threading. Either the	platform
	  already has threads, or one has to hope that some semi-portable
	  package exists for it. And even those	semi-portable packages usually
	  have to deal with assembler code and other nasty internals and are
	  not easy to port to forthcoming platforms.

       So, in short: the matrix-dispatching approach is	portable and fast, but
       nasty to	program. The thread scheduling approach	is easy	to program,
       but suffers from	synchronization	and portability	problems caused	by its
       preemptive nature.

   The Compromise of Pth
       But why not combine the good aspects of both approaches while avoiding
       their bad aspects? That's the goal of Pth. Pth implements easy-to-
       program threads of execution, but avoids	the problems of	preemptive
       scheduling by using non-preemptive scheduling instead.

       This sounds like, and is, a useful approach. Nevertheless, one has to
       keep the	implications of	non-preemptive thread scheduling in mind when
       working with Pth. The following list summarizes a few essential points:

       o Pth provides maximum portability, but NOT the fanciest	features.

	 This is, because it uses a nifty and portable POSIX/ANSI-C approach
	 for thread creation (and this way doesn't require any platform
	 dependent assembler hacks) and	schedules the threads in non-
	 preemptive way	(which doesn't require unportable facilities like
	 "SIGVTALRM"). On the other hand, this way not all fancy threading
	 features can be implemented.  Nevertheless the	available facilities
	 are enough to provide a robust	and full-featured threading system.

       o Pth increases the responsiveness and concurrency of an	event-driven
	 application, but NOT the concurrency of number-crunching
	 applications.

	 The reason is the non-preemptive scheduling. Number-crunching
	 applications usually require preemptive scheduling to achieve
	 concurrency because of	their long CPU bursts. For them, non-
	 preemptive scheduling (even together with explicit yielding) provides
	 only the old concept of `coroutines'. On the other hand, event	driven
	 applications benefit greatly from non-preemptive scheduling. They
	 have only short CPU bursts and	lots of	events to wait on, and this
	 way run faster	under non-preemptive scheduling	because	no unnecessary
	 context switching occurs, as it is the	case for preemptive
	 scheduling. That's why	Pth is mainly intended for server type
	 applications, although	there is no technical restriction.

       o Pth requires thread-safe functions, but NOT reentrant functions.

	 This nice fact	exists again because of	the nature of non-preemptive
	 scheduling, where a function isn't interrupted	and this way cannot be
	 reentered before it returned. This is a great portability benefit,
	 because thread-safety can be achieved more easily than	reentrance
	 possibility. Especially this means that under Pth more	existing
	 third-party libraries can be used without side-effects	than it's the
	 case for other	threading systems.

       o Pth doesn't require any kernel	support, but can NOT benefit from
	 multiprocessor	machines.

	 This means that Pth runs on almost all	Unix kernels, because the
	 kernel	does not need to be aware of the Pth threads (because they are
	 implemented entirely in user-space). On the other hand, it cannot
	 benefit from the existence of multiprocessors,	because	for this,
	 kernel	support	would be needed. In practice, this is no problem,
	 because multiprocessor	systems	are rare, and portability is almost
	 more important	than highest concurrency.

   The life cycle of a thread
       To understand the Pth Application Programming Interface (API), it helps
       to first	understand the life cycle of a thread in the Pth threading
       system. It can be illustrated with the following	directed graph:

		    NEW
		     |
		     V
	     +---> READY ---+
	     |	     ^	    |
	     |	     |	    V
	  WAITING <--+-- RUNNING
			    |
	     :		    V
	  SUSPENDED	  DEAD

       When a new thread is created, it	is moved into the NEW queue of the
       scheduler. On the next dispatching for this thread, the scheduler picks
       it up from there	and moves it to	the READY queue. This is a queue
       containing all threads which want to perform a CPU burst. There they
       are queued in priority order. On	each dispatching step, the scheduler
       always removes the thread with the highest priority only. It then
       increases the priority of all remaining threads by 1, to	prevent	them
       from `starving'.

       The thread which	was removed from the READY queue is the	new RUNNING
       thread (there is	always just one	RUNNING	thread,	of course). The
       RUNNING thread is assigned execution control. After this	thread yields
       execution (either explicitly by yielding	execution or implicitly	by
       calling a function which	would block) there are three possibilities:
       Either it has terminated, then it is moved to the DEAD queue, or	it has
       events on which it wants	to wait, then it is moved into the WAITING
       queue. Else it is assumed it wants to perform more CPU bursts and
       immediately enters the READY queue again.

       Before the next thread is taken out of the READY	queue, the WAITING
       queue is	checked	for pending events. If one or more events occurred,
       the threads that	are waiting on them are	immediately moved to the READY
       queue.

       The purpose of the NEW queue has	to do with the fact that in Pth	a
       thread never directly switches to another thread. A thread always
       yields execution	to the scheduler and the scheduler dispatches to the
       next thread. So a freshly spawned thread	has to be kept somewhere until
       the scheduler gets a chance to pick it up for scheduling. That is what
       the NEW queue is	for.

       The purpose of the DEAD queue is	to support thread joining. When	a
       thread is marked	to be unjoinable, it is	directly kicked	out of the
       system after it terminated. But when it is joinable, it enters the DEAD
       queue. There it remains until another thread joins it.

       Finally,	there is a special separated queue named SUSPENDED, to where
       threads can be manually moved from the NEW, READY or WAITING queues by
       the application.	The purpose of this special queue is to	temporarily
       absorb suspended	threads	until they are again resumed by	the
       application. Suspended threads do not cost scheduling or	event handling
       resources, because they are temporarily completely out of the
       scheduler's scope. If a thread is resumed, it is	moved back to the
       queue from where	it originally came and this way	again enters the
       schedulers scope.

APPLICATION PROGRAMMING	INTERFACE (API)
       In the following	the Pth	Application Programming	Interface (API)	is
       discussed in detail. With the knowledge given above, it should now be
       easy to understand how to program threads with this API.	In good	Unix
       tradition, Pth functions	use special return values ("NULL" in pointer
       context,	"FALSE"	in boolean context and "-1" in integer context)	to
       indicate	an error condition and set (or pass through) the "errno"
       system variable to pass more details about the error to the caller.

   Global Library Management
       The following functions act on the library as a whole.  They are	used
       to initialize and shutdown the scheduler	and fetch information from it.

       int pth_init(void);
	   This	initializes the	Pth library. It	has to be the first Pth	API
	   function call in an application, and	is mandatory. It's usually
	   done	at the begin of	the main() function of the application.	This
	   implicitly spawns the internal scheduler thread and transforms the
	   single execution unit of the	current	process	into a thread (the
	   `main' thread). It returns "TRUE" on	success	and "FALSE" on error.

       int pth_kill(void);
	   This	kills the Pth library. It should be the	last Pth API function
	   call	in an application, but is not really required. It's usually
	   done	at the end of the main function	of the application. At least,
	   it has to be	called from within the main thread. It implicitly
	   kills all threads and transforms back the calling thread into the
	   single execution unit of the	underlying process.  The usual way to
	   terminate a Pth application is either a simple `"pth_exit(0);"' in
	   the main thread (which waits	for all	other threads to terminate,
	   kills the threading system and then terminates the process) or a
	   `"pth_kill(); exit(0)"' (which immediately kills the	threading
	   system and terminates the process). The pth_kill() return
	   immediately with a return code of "FALSE" if	it is not called from
	   within the main thread. Else	it kills the threading system and
	   returns "TRUE".

       long pth_ctrl(unsigned long query, ...);
	   This	is a generalized query/control function	for the	Pth library.
	   The argument	query is a bitmask formed out of one or	more
	   "PTH_CTRL_"XXXX queries. Currently the following queries are
	   supported:

	   "PTH_CTRL_GETTHREADS"
	       This returns the	total number of	threads	currently in
	       existence.  This	query actually is formed out of	the
	       combination of queries for threads in a particular state, i.e.,
	       the "PTH_CTRL_GETTHREADS" query is equal	to the OR-combination
	       of all the following specialized	queries:

	       "PTH_CTRL_GETTHREADS_NEW" for the number	of threads in the new
	       queue (threads created via pth_spawn(3) but still not scheduled
	       once), "PTH_CTRL_GETTHREADS_READY" for the number of threads in
	       the ready queue (threads	who want to do CPU bursts),
	       "PTH_CTRL_GETTHREADS_RUNNING" for the number of running threads
	       (always just one	thread!), "PTH_CTRL_GETTHREADS_WAITING"	for
	       the number of threads in	the waiting queue (threads waiting for
	       events),	"PTH_CTRL_GETTHREADS_SUSPENDED"	for the	number of
	       threads in the suspended	queue (threads waiting to be resumed)
	       and "PTH_CTRL_GETTHREADS_DEAD" for the number of	threads	in the
	       new queue (terminated threads waiting for a join).

	   "PTH_CTRL_GETAVLOAD"
	       This requires a second argument of type `"float *"' (pointer to
	       a floating point	variable).  It stores a	floating point value
	       describing the exponential averaged load	of the scheduler in
	       this variable. The load is a function from the number of
	       threads in the ready queue of the schedulers dispatching	unit.
	       So a load around	1.0 means there	is only	one ready thread (the
	       standard	situation when the application has no high load). A
	       higher load value means there a more threads ready who want to
	       do CPU bursts. The average load value updates once per second
	       only. The return	value for this query is	always 0.

	   "PTH_CTRL_GETPRIO"
	       This requires a second argument of type `"pth_t"' which
	       identifies a thread.  It	returns	the priority (ranging from
	       "PTH_PRIO_MIN" to "PTH_PRIO_MAX") of the	given thread.

	   "PTH_CTRL_GETNAME"
	       This requires a second argument of type `"pth_t"' which
	       identifies a thread. It returns the name	of the given thread,
	       i.e., the return	value of pth_ctrl(3) should be casted to a
	       `"char *"'.

	   "PTH_CTRL_DUMPSTATE"
	       This requires a second argument of type `"FILE *"' to which a
	       summary of the internal Pth library state is written to.	The
	       main information	which is currently written out is the current
	       state of	the thread pool.

	   "PTH_CTRL_FAVOURNEW"
	       This requires a second argument of type `"int"' which specified
	       whether the GNU Pth scheduler favours new threads on startup,
	       i.e., whether they are moved from the new queue to the top
	       (argument is "TRUE") or middle (argument	is "FALSE") of the
	       ready queue. The	default	is to favour new threads to make sure
	       they do not starve already at startup, although this slightly
	       violates	the strict priority based scheduling.

	   The function	returns	"-1" on	error.

       long pth_version(void);
	   This	function returns a hex-value `0xVRRTLL'	which describes	the
	   current Pth library version.	V is the version, RR the revisions, LL
	   the level and T the type of the level (alphalevel=0,	betalevel=1,
	   patchlevel=2, etc). For instance Pth	version	1.0b1 is encoded as
	   0x100101.  The reason for this unusual mapping is that this way the
	   version number is steadily increasing. The same value is also
	   available under compile time	as "PTH_VERSION".

   Thread Attribute Handling
       Attribute objects are used in Pth for two things: First
       stand-alone/unbound attribute objects are used to store attributes for
       to be spawned threads.  Bounded attribute objects are used to modify
       attributes of already existing threads. The following attribute fields
       exists in attribute objects:

       "PTH_ATTR_PRIO" (read-write) ["int"]
	   Thread Priority between "PTH_PRIO_MIN" and "PTH_PRIO_MAX".  The
	   default is "PTH_PRIO_STD".

       "PTH_ATTR_NAME" (read-write) ["char *"]
	   Name	of thread (up to 40 characters are stored only), mainly	for
	   debugging purposes.

       "PTH_ATTR_DISPATCHES" (read-write) ["int"]
	   In bounded attribute	objects, this field is incremented every time
	   the context is switched to the associated thread.

       "PTH_ATTR_JOINABLE" (read-write>	["int"]
	   The thread detachment type, "TRUE" indicates	a joinable thread,
	   "FALSE" indicates a detached	thread.	When a thread is detached,
	   after termination it	is immediately kicked out of the system
	   instead of inserted into the	dead queue.

       "PTH_ATTR_CANCEL_STATE" (read-write) ["unsigned int"]
	   The thread cancellation state, i.e.,	a combination of
	   "PTH_CANCEL_ENABLE" or "PTH_CANCEL_DISABLE" and
	   "PTH_CANCEL_DEFERRED" or "PTH_CANCEL_ASYNCHRONOUS".

       "PTH_ATTR_STACK_SIZE" (read-write) ["unsigned int"]
	   The thread stack size in bytes. Use lower values than 64 KB with
	   great care!

       "PTH_ATTR_STACK_ADDR" (read-write) ["char *"]
	   A pointer to	the lower address of a chunk of	malloc(3)'ed memory
	   for the stack.

       "PTH_ATTR_TIME_SPAWN" (read-only) ["pth_time_t"]
	   The time when the thread was	spawned.  This can be queried only
	   when	the attribute object is	bound to a thread.

       "PTH_ATTR_TIME_LAST" (read-only)	["pth_time_t"]
	   The time when the thread was	last dispatched.  This can be queried
	   only	when the attribute object is bound to a	thread.

       "PTH_ATTR_TIME_RAN" (read-only) ["pth_time_t"]
	   The total time the thread was running.  This	can be queried only
	   when	the attribute object is	bound to a thread.

       "PTH_ATTR_START_FUNC" (read-only) ["void	*(*)(void *)"]
	   The thread start function.  This can	be queried only	when the
	   attribute object is bound to	a thread.

       "PTH_ATTR_START_ARG" (read-only)	["void *"]
	   The thread start argument.  This can	be queried only	when the
	   attribute object is bound to	a thread.

       "PTH_ATTR_STATE"	(read-only) ["pth_state_t"]
	   The scheduling state	of the thread, i.e., either "PTH_STATE_NEW",
	   "PTH_STATE_READY", "PTH_STATE_WAITING", or "PTH_STATE_DEAD" This
	   can be queried only when the	attribute object is bound to a thread.

       "PTH_ATTR_EVENTS" (read-only) ["pth_event_t"]
	   The event ring the thread is	waiting	for.  This can be queried only
	   when	the attribute object is	bound to a thread.

       "PTH_ATTR_BOUND"	(read-only) ["int"]
	   Whether the attribute object	is bound ("TRUE") to a thread or not
	   ("FALSE").

       The following API functions can be used to handle the attribute
       objects:

       pth_attr_t pth_attr_of(pth_t tid);
	   This	returns	a new attribute	object bound to	thread tid.  Any
	   queries on this object directly fetch attributes from tid. And
	   attribute modifications directly change tid.	Use such attribute
	   objects to modify existing threads.

       pth_attr_t pth_attr_new(void);
	   This	returns	a new unbound attribute	object.	An implicit
	   pth_attr_init() is done on it. Any queries on this object just
	   fetch stored	attributes from	it.  And attribute modifications just
	   change the stored attributes.  Use such attribute objects to	pre-
	   configure attributes	for to be spawned threads.

       int pth_attr_init(pth_attr_t attr);
	   This	initializes an attribute object	attr to	the default values:
	   "PTH_ATTR_PRIO" := "PTH_PRIO_STD", "PTH_ATTR_NAME" := `"unknown"',
	   "PTH_ATTR_DISPATCHES" := 0, "PTH_ATTR_JOINABLE" := "TRUE",
	   "PTH_ATTR_CANCELSTATE" := "PTH_CANCEL_DEFAULT",
	   "PTH_ATTR_STACK_SIZE" := 64*1024 and	"PTH_ATTR_STACK_ADDR" :=
	   "NULL". All other "PTH_ATTR_*" attributes are read-only attributes
	   and don't receive default values in attr, because they exists only
	   for bounded attribute objects.

       int pth_attr_set(pth_attr_t attr, int field, ...);
	   This	sets the attribute field field in attr to a value specified as
	   an additional argument on the variable argument list. The following
	   attribute fields and	argument pairs can be used:

	    PTH_ATTR_PRIO	    int
	    PTH_ATTR_NAME	    char *
	    PTH_ATTR_DISPATCHES	    int
	    PTH_ATTR_JOINABLE	    int
	    PTH_ATTR_CANCEL_STATE   unsigned int
	    PTH_ATTR_STACK_SIZE	    unsigned int
	    PTH_ATTR_STACK_ADDR	    char *

       int pth_attr_get(pth_attr_t attr, int field, ...);
	   This	retrieves the attribute	field field in attr and	stores its
	   value in the	variable specified through a pointer in	an additional
	   argument on the variable argument list. The following fields	and
	   argument pairs can be used:

	    PTH_ATTR_PRIO	    int	*
	    PTH_ATTR_NAME	    char **
	    PTH_ATTR_DISPATCHES	    int	*
	    PTH_ATTR_JOINABLE	    int	*
	    PTH_ATTR_CANCEL_STATE   unsigned int *
	    PTH_ATTR_STACK_SIZE	    unsigned int *
	    PTH_ATTR_STACK_ADDR	    char **
	    PTH_ATTR_TIME_SPAWN	    pth_time_t *
	    PTH_ATTR_TIME_LAST	    pth_time_t *
	    PTH_ATTR_TIME_RAN	    pth_time_t *
	    PTH_ATTR_START_FUNC	    void *(**)(void *)
	    PTH_ATTR_START_ARG	    void **
	    PTH_ATTR_STATE	    pth_state_t	*
	    PTH_ATTR_EVENTS	    pth_event_t	*
	    PTH_ATTR_BOUND	    int	*

       int pth_attr_destroy(pth_attr_t attr);
	   This	destroys a attribute object attr. After	this attr is no	longer
	   a valid attribute object.

   Thread Control
       The following functions control the threading itself and	make up	the
       main API	of the Pth library.

       pth_t pth_spawn(pth_attr_t attr,	void *(*entry)(void *),	void *arg);
	   This	spawns a new thread with the attributes	given in attr (or
	   "PTH_ATTR_DEFAULT" for default attributes - which means that	thread
	   priority, joinability and cancel state are inherited	from the
	   current thread) with	the starting point at routine entry; the
	   dispatch count is not inherited from	the current thread if attr is
	   not specified - rather, it is initialized to	zero.  This entry
	   routine is called as	`pth_exit(entry(arg))' inside the new thread
	   unit, i.e., entry's return value is fed to an implicit pth_exit(3).
	   So the thread can also exit by just returning. Nevertheless the
	   thread can also exit	explicitly at any time by calling pth_exit(3).
	   But keep in mind that calling the POSIX function exit(3) still
	   terminates the complete process and not just	the current thread.

	   There is no Pth-internal limit on the number	of threads one can
	   spawn, except the limit implied by the available virtual memory.
	   Pth internally keeps	track of thread	in dynamic data	structures.
	   The function	returns	"NULL" on error.

       int pth_once(pth_once_t *ctrlvar, void (*func)(void *), void *arg);
	   This	is a convenience function which	uses a control variable	of
	   type	"pth_once_t" to	make sure a constructor	function func is
	   called only once as `func(arg)' in the system. In other words: Only
	   the first call to pth_once(3) by any	thread in the system succeeds.
	   The variable	referenced via ctrlvar should be declared as
	   `"pth_once_t" variable-name = "PTH_ONCE_INIT";' before calling this
	   function.

       pth_t pth_self(void);
	   This	just returns the unique	thread handle of the currently running
	   thread.  This handle	itself has to be treated as an opaque entity
	   by the application.	It's usually used as an	argument to other
	   functions who require an argument of	type "pth_t".

       int pth_suspend(pth_t tid);
	   This	suspends a thread tid until it is manually resumed again via
	   pth_resume(3). For this, the	thread is moved	to the SUSPENDED queue
	   and this way	is completely out of the scheduler's event handling
	   and thread dispatching scope. Suspending the	current	thread is not
	   allowed.  The function returns "TRUE" on success and	"FALSE"	on
	   errors.

       int pth_resume(pth_t tid);
	   This	function resumes a previously suspended	thread tid, i.e. tid
	   has to stay on the SUSPENDED	queue. The thread is moved to the NEW,
	   READY or WAITING queue (dependent on	what its state was when	the
	   pth_suspend(3) call were made) and this way again enters the	event
	   handling and	thread dispatching scope of the	scheduler. The
	   function returns "TRUE" on success and "FALSE" on errors.

       int pth_raise(pth_t tid,	int sig)
	   This	function raises	a signal for delivery to thread	tid only.
	   When	one just raises	a signal via raise(3) or kill(2), its
	   delivered to	an arbitrary thread which has this signal not blocked.
	   With	pth_raise(3) one can send a signal to a	thread and its
	   guarantees that only	this thread gets the signal delivered. But
	   keep	in mind	that nevertheless the signals action is	still
	   configured process-wide.  When sig is 0 plain thread	checking is
	   performed, i.e., `"pth_raise(tid, 0)"' returns "TRUE" when thread
	   tid still exists in the PTH system but doesn't send any signal to
	   it.

       int pth_yield(pth_t tid);
	   This	explicitly yields back the execution control to	the scheduler
	   thread.  Usually the	execution is implicitly	transferred back to
	   the scheduler when a	thread waits for an event. But when a thread
	   has to do larger CPU	bursts,	it can be reasonable to	interrupt it
	   explicitly by doing a few pth_yield(3) calls	to give	other threads
	   a chance to execute,	too.  This obviously is	the cooperating	part
	   of Pth.  A thread has not to	yield execution, of course. But	when
	   you want to program a server	application with good response times
	   the threads should be cooperative, i.e., when they should split
	   their CPU bursts into smaller units with this call.

	   Usually one specifies tid as	"NULL" to indicate to the scheduler
	   that	it can freely decide which thread to dispatch next.  But if
	   one wants to	indicate to the	scheduler that a particular thread
	   should be favored on	the next dispatching step, one can specify
	   this	thread explicitly. This	allows the usage of the	old concept of
	   coroutines where a thread/routine switches to a particular
	   cooperating thread. If tid is not "NULL" and	points to a new	or
	   ready thread, it is guaranteed that this thread receives execution
	   control on the next dispatching step. If tid	is in a	different
	   state (that is, not in "PTH_STATE_NEW" or "PTH_STATE_READY")	an
	   error is reported.

	   The function	usually	returns	"TRUE" for success and only "FALSE"
	   (with "errno" set to	"EINVAL") if tid specified an invalid or still
	   not new or ready thread.

       int pth_nap(pth_time_t naptime);
	   This	functions suspends the execution of the	current	thread until
	   naptime is elapsed. naptime is of type "pth_time_t" and this	way
	   has theoretically a resolution of one microsecond. In practice you
	   should neither rely on this nor that	the thread is awakened exactly
	   after naptime has elapsed. It's only	guarantees that	the thread
	   will	sleep at least naptime.	But because of the non-preemptive
	   nature of Pth it can	last longer (when another thread kept the CPU
	   for a long time). Additionally the resolution is dependent of the
	   implementation of timers by the operating system and	these usually
	   have	only a resolution of 10	microseconds or	larger.	But usually
	   this	isn't important	for an application unless it tries to use this
	   facility for	real time tasks.

       int pth_wait(pth_event_t	ev);
	   This	is the link between the	scheduler and the event	facility (see
	   below for the various pth_event_xxx() functions). It's modeled like
	   select(2), i.e., one	gives this function one	or more	events (in the
	   event ring specified	by ev) on which	the current thread wants to
	   wait. The scheduler awakes the thread when one ore more of them
	   occurred or failed after tagging them as such. The ev argument is a
	   pointer to an event ring which isn't	changed	except for the
	   tagging. pth_wait(3)	returns	the number of occurred or failed
	   events and the application can use pth_event_status(3) to test
	   which events	occurred or failed.

       int pth_cancel(pth_t tid);
	   This	cancels	a thread tid. How the cancellation is done depends on
	   the cancellation state of tid which the thread can configure
	   itself. When	its state is "PTH_CANCEL_DISABLE" a cancellation
	   request is just made	pending.  When it is "PTH_CANCEL_ENABLE" it
	   depends on the cancellation type what is performed. When its
	   "PTH_CANCEL_DEFERRED" again the cancellation	request	is just	made
	   pending. But	when its "PTH_CANCEL_ASYNCHRONOUS" the thread is
	   immediately canceled	before pth_cancel(3) returns. The effect of a
	   thread cancellation is equal	to implicitly forcing the thread to
	   call	`"pth_exit(PTH_CANCELED)"' at one of his cancellation points.
	   In Pth thread enter a cancellation point either explicitly via
	   pth_cancel_point(3) or implicitly by	waiting	for an event.

       int pth_abort(pth_t tid);
	   This	is the cruel way to cancel a thread tid. When it's already
	   dead	and waits to be	joined it just joins it	(via `"pth_join("tid",
	   NULL)"') and	this way kicks it out of the system.  Else it forces
	   the thread to be not	joinable and to	allow asynchronous
	   cancellation	and then cancels it via	`"pth_cancel("tid")"'.

       int pth_join(pth_t tid, void **value);
	   This	joins the current thread with the thread specified via tid.
	   It first suspends the current thread	until the tid thread has
	   terminated. Then it is awakened and stores the value	of tid's
	   pth_exit(3) call into *value	(if value and not "NULL") and returns
	   to the caller. A thread can be joined only when it has the
	   attribute "PTH_ATTR_JOINABLE" set to	"TRUE" (the default). A	thread
	   can only be joined once, i.e., after	the pth_join(3)	call the
	   thread tid is completely removed from the system.

       void pth_exit(void *value);
	   This	terminates the current thread. Whether it's immediately
	   removed from	the system or inserted into the	dead queue of the
	   scheduler depends on	its join type which was	specified at spawning
	   time. If it has the attribute "PTH_ATTR_JOINABLE" set to "FALSE",
	   it's	immediately removed and	value is ignored. Else the thread is
	   inserted into the dead queue	and value remembered for a subsequent
	   pth_join(3) call by another thread.

   Utilities
       Utility functions.

       int pth_fdmode(int fd, int mode);
	   This	switches the non-blocking mode flag on file descriptor fd.
	   The argument	mode can be "PTH_FDMODE_BLOCK" for switching fd	into
	   blocking I/O	mode, "PTH_FDMODE_NONBLOCK" for	switching fd into non-
	   blocking I/O	mode or	"PTH_FDMODE_POLL" for just polling the current
	   mode. The current mode is returned (either "PTH_FDMODE_BLOCK" or
	   "PTH_FDMODE_NONBLOCK") or "PTH_FDMODE_ERROR"	on error. Keep in mind
	   that	since Pth 1.1 there is no longer a requirement to manually
	   switch a file descriptor into non-blocking mode in order to use it.
	   This	is automatically done temporarily inside Pth.  Instead when
	   you now switch a file descriptor explicitly into non-blocking mode,
	   pth_read(3) or pth_write(3) will never block	the current thread.

       pth_time_t pth_time(long	sec, long usec);
	   This	is a constructor for a "pth_time_t" structure which is a
	   convenient function to avoid	temporary structure values. It returns
	   a pth_time_t	structure which	holds the absolute time	value
	   specified by	sec and	usec.

       pth_time_t pth_timeout(long sec,	long usec);
	   This	is a constructor for a "pth_time_t" structure which is a
	   convenient function to avoid	temporary structure values.  It
	   returns a pth_time_t	structure which	holds the absolute time	value
	   calculated by adding	sec and	usec to	the current time.

       void pth_int_time(struct	timespec *sp);
	   Returns the current time of the pthsem internal time	base.

       Sfdisc_t	*pth_sfiodisc(void);
	   This	functions is always available, but only	reasonably usable when
	   Pth was built with Sfio support ("--with-sfio" option) and
	   "PTH_EXT_SFIO" is then defined by "pth.h". It is useful for
	   applications	which want to use the comprehensive Sfio I/O library
	   with	the Pth	threading library. Then	this function can be used to
	   get an Sfio discipline structure ("Sfdisc_t") which can be pushed
	   onto	Sfio streams ("Sfio_t")	in order to let	this stream use
	   pth_read(3)/pth_write(2) instead of read(2)/write(2). The benefit
	   is that this	way I/O	on the Sfio stream does	only block the current
	   thread instead of the whole process.	The application	has to free(3)
	   the "Sfdisc_t" structure when it is no longer needed. The Sfio
	   package can be found	at http://www.research.att.com/sw/tools/sfio/.

   Cancellation	Management
       Pth supports POSIX style	thread cancellation via	pth_cancel(3) and the
       following two related functions:

       void pth_cancel_state(int newstate, int *oldstate);
	   This	manages	the cancellation state of the current thread.  When
	   oldstate is not "NULL" the function stores the old cancellation
	   state under the variable pointed to by oldstate. When newstate is
	   not 0 it sets the new cancellation state. oldstate is created
	   before newstate is set.  A state is a combination of
	   "PTH_CANCEL_ENABLE" or "PTH_CANCEL_DISABLE" and
	   "PTH_CANCEL_DEFERRED" or "PTH_CANCEL_ASYNCHRONOUS".
	   "PTH_CANCEL_ENABLE|PTH_CANCEL_DEFERRED" (or "PTH_CANCEL_DEFAULT")
	   is the default state	where cancellation is possible but only	at
	   cancellation	points.	 Use "PTH_CANCEL_DISABLE" to complete disable
	   cancellation	for a thread and "PTH_CANCEL_ASYNCHRONOUS" for
	   allowing asynchronous cancellations,	i.e., cancellations which can
	   happen at any time.

       void pth_cancel_point(void);
	   This	explicitly enter a cancellation	point. When the	current
	   cancellation	state is "PTH_CANCEL_DISABLE" or no cancellation
	   request is pending, this has	no side-effect and returns
	   immediately.	Else it	calls `"pth_exit(PTH_CANCELED)"'.

   Event Handling
       Pth has a very flexible event facility which is linked into the
       scheduler through the pth_wait(3) function. The following functions
       provide the handling of event rings.

       pth_event_t pth_event(unsigned long spec, ...);
	   This	creates	a new event ring consisting of a single	initial	event.
	   The type of the generated event is specified	by spec. The following
	   types are available:

	   "PTH_EVENT_FD"
	       This is a file descriptor event.	One or more of
	       "PTH_UNTIL_FD_READABLE",	"PTH_UNTIL_FD_WRITEABLE" or
	       "PTH_UNTIL_FD_EXCEPTION"	have to	be OR-ed into spec to specify
	       on which	state of the file descriptor you want to wait.	The
	       file descriptor itself has to be	given as an additional
	       argument.  Example:
	       `"pth_event(PTH_EVENT_FD|PTH_UNTIL_FD_READABLE, fd)"'.

	   "PTH_EVENT_SELECT"
	       This is a multiple file descriptor event	modeled	directly after
	       the select(2) call (actually it is also used to implement
	       pth_select(3) internally).  It's	a convenient way to wait for a
	       large set of file descriptors at	once and at each file
	       descriptor for a	different type of state. Additionally as a
	       nice side-effect	one receives the number	of file	descriptors
	       which causes the	event to be occurred (using BSD	semantics,
	       i.e., when a file descriptor occurred in	two sets it's counted
	       twice). The arguments correspond	directly to the	select(2)
	       function	arguments except that there is no timeout argument
	       (because	timeouts already can be	handled	via "PTH_EVENT_TIME"
	       events).

	       Example:	`"pth_event(PTH_EVENT_SELECT, &rc, nfd,	rfds, wfds,
	       efds)"' where "rc" has to be of type `"int *"', "nfd" has to be
	       of type `"int"' and "rfds", "wfds" and "efds" have to be	of
	       type `"fd_set *"' (see select(2)). The number of	occurred file
	       descriptors are stored in "rc".

	   "PTH_EVENT_SIGS"
	       This is a signal	set event. The two additional arguments	have
	       to be a pointer to a signal set (type `"sigset_t	*"') and a
	       pointer to a signal number variable (type `"int *"').  This
	       event waits until one of	the signals in the signal set
	       occurred.  As a result the occurred signal number is stored in
	       the second additional argument. Keep in mind that the Pth
	       scheduler doesn't block signals automatically.  So when you
	       want to wait for	a signal with this event you've	to block it
	       via sigprocmask(2) or it	will be	delivered without your notice.
	       Example:	`"sigemptyset(&set); sigaddset(&set, SIGINT);
	       pth_event(PTH_EVENT_SIG,	&set, &sig);"'.

	   "PTH_EVENT_TIME"
	       This is a time point event. The additional argument has to be
	       of type "pth_time_t" (usually on-the-fly	generated via
	       pth_time(3)). This events waits until the specified time	point
	       has elapsed. Keep in mind that the value	is an absolute time
	       point and not an	offset.	When you want to wait for a specified
	       amount of time, you've to add the current time to the offset
	       (usually	on-the-fly achieved via	pth_timeout(3)).  Example:
	       `"pth_event(PTH_EVENT_TIME, pth_timeout(2,0))"'.

	   "PTH_EVENT_RTIME"
	       This is a time interval event. The additional argument has to
	       be of type "pth_time_t" (usually	on-the-fly generated via
	       pth_time(3)), containing	a time interval. During	creation, it
	       is converted into PTH_EVENT_TIME. It has	the advantage, that it
	       only uses the pthsem internal clock. Example:
	       `"pth_event(PTH_EVENT_TIME, pth_timeout(2,0))"'.	 is equal to
	       `"pth_event(PTH_EVENT_RTIME, pth_time(2,0))"'.

	   "PTH_EVENT_MSG"
	       This is a message port event. The additional argument has to be
	       of type "pth_msgport_t".	This events waits until	one or more
	       messages	were received on the specified message port.  Example:
	       `"pth_event(PTH_EVENT_MSG, mp)"'.

	   "PTH_EVENT_TID"
	       This is a thread	event. The additional argument has to be of
	       type "pth_t".  One of "PTH_UNTIL_TID_NEW",
	       "PTH_UNTIL_TID_READY", "PTH_UNTIL_TID_WAITING" or
	       "PTH_UNTIL_TID_DEAD" has	to be OR-ed into spec to specify on
	       which state of the thread you want to wait.  Example:
	       `"pth_event(PTH_EVENT_TID|PTH_UNTIL_TID_DEAD, tid)"'.

	   "PTH_EVENT_FUNC"
	       This is a custom	callback function event. Three additional
	       arguments have to be given with the following types: `"int
	       (*)(void	*)"', `"void *"' and `"pth_time_t"'. The first is a
	       function	pointer	to a check function and	the second argument is
	       a user-supplied context value which is passed to	this function.
	       The scheduler calls this	function on a regular basis (on	his
	       own scheduler stack, so be very careful!) and the thread	is
	       kept sleeping while the function	returns	"FALSE". Once it
	       returned	"TRUE" the thread will be awakened. The	check interval
	       is defined by the third argument, i.e., the check function is
	       polled again not	until this amount of time elapsed. Example:
	       `"pth_event(PTH_EVENT_FUNC, func, arg, pth_time(0,500000))"'.

	   "PTH_EVENT_SEM"
	       This is a semaphore event. It waits for a semaphore, until it
	       can be decremented. By default 1	is used	for this, with the
	       flag "PTH_UNTIL_COUNT" other values can be used.	If the flag
	       "PTH_UNTIL_DECREMENT" is	used, the semaphore value is
	       decremented (so the lock	is obtained), else the event is
	       signaled, if it would be	possible. Examples:

	       * pth_event(PTH_EVENT_SEM|PTH_UNTIL_DECREMENT|PTH_UNTIL_COUNT,
	       &sem,2):	event waits, utils the value of	the semaphore is >= 2
	       and subtracts then two from it

	       * pth_event(PTH_EVENT_SEM|PTH_UNTIL_COUNT, &sem,2): event
	       waits, util the value of	the semaphore is >= 2

	       * pth_event(PTH_EVENT_SEM|PTH_UNTIL_DECREMENT, &sem): event
	       waits, util the value of	the semaphore is >= 1 and subtracts
	       then 1 from it

	       * pth_event(PTH_EVENT_SEM, &sem): event waits, util the value
	       of the semaphore	is >= 1

       unsigned	long pth_event_typeof(pth_event_t ev);
	   This	returns	the type of event ev. It's a combination of the
	   describing "PTH_EVENT_XX" and "PTH_UNTIL_XX"	value. This is
	   especially useful to	know which arguments have to be	supplied to
	   the pth_event_extract(3) function.

       int pth_event_extract(pth_event_t ev, ...);
	   When	pth_event(3) is	treated	like sprintf(3), then this function is
	   sscanf(3), i.e., it is the inverse operation	of pth_event(3). This
	   means that it can be	used to	extract	the ingredients	of an event.
	   The ingredients are stored into variables which are given as
	   pointers on the variable argument list.  Which pointers have	to be
	   present depends on the event	type and has to	be determined by the
	   caller before via pth_event_typeof(3).

	   To make it clear, when you constructed ev via `"ev =
	   pth_event(PTH_EVENT_FD, fd);"' you have to extract it via
	   `"pth_event_extract(ev, &fd)"', etc.	For multiple arguments of an
	   event the order of the pointer arguments is the same	as for
	   pth_event(3). But always keep in mind that you have to always
	   supply pointers to variables	and these variables have to be of the
	   same	type as	the argument of	pth_event(3) required.

       pth_event_t pth_event_concat(pth_event_t	ev, ...);
	   This	concatenates one or more additional event rings	to the event
	   ring	ev and returns ev. The end of the argument list	has to be
	   marked with a "NULL"	argument. Use this function to create real
	   events rings	out of the single-event	rings created by pth_event(3).

       pth_event_t pth_event_isolate(pth_event_t ev);
	   This	isolates the event ev from possibly appended events in the
	   event ring.	When in	ev only	one event exists, this returns "NULL".
	   When	remaining events exists, they form a new event ring which is
	   returned.

       pth_event_t pth_event_walk(pth_event_t ev, int direction);
	   This	walks to the next (when	direction is "PTH_WALK_NEXT") or
	   previews (when direction is "PTH_WALK_PREV")	event in the event
	   ring	ev and returns this new	reached	event. Additionally
	   "PTH_UNTIL_OCCURRED"	can be OR-ed into direction to walk to the
	   next/previous occurred event	in the ring ev.

       pth_status_t pth_event_status(pth_event_t ev);
	   This	returns	the status of event ev.	This is	a fast operation
	   because only	a tag on ev is checked which was either	set or still
	   not set by the scheduler. In	other words: This doesn't check	the
	   event itself, it just checks	the last knowledge of the scheduler.
	   The possible	returned status	codes are: "PTH_STATUS_PENDING"	(event
	   is still pending), "PTH_STATUS_OCCURRED" (event successfully
	   occurred), "PTH_STATUS_FAILED" (event failed).

       int pth_event_free(pth_event_t ev, int mode);
	   This	deallocates the	event ev (when mode is "PTH_FREE_THIS")	or all
	   events appended to the event	ring under ev (when mode is
	   "PTH_FREE_ALL").

   Key-Based Storage
       The following functions provide thread-local storage through unique
       keys similar to the POSIX Pthread API. Use this for thread specific
       global data.

       int pth_key_create(pth_key_t *key, void (*func)(void *));
	   This	created	a new unique key and stores it in key.	Additionally
	   func	can specify a destructor function which	is called on the
	   current threads termination with the	key.

       int pth_key_delete(pth_key_t key);
	   This	explicitly destroys a key key.

       int pth_key_setdata(pth_key_t key, const	void *value);
	   This	stores value under key.

       void *pth_key_getdata(pth_key_t key);
	   This	retrieves the value under key.

   Message Port	Communication
       The following functions provide message ports which can be used for
       efficient and flexible inter-thread communication.

       pth_msgport_t pth_msgport_create(const char *name);
	   This	returns	a pointer to a new message port. If name name is not
	   "NULL", the name can	be used	by other threads via
	   pth_msgport_find(3) to find the message port	in case	they do	not
	   know	directly the pointer to	the message port.

       void pth_msgport_destroy(pth_msgport_t mp);
	   This	destroys a message port	mp. Before all pending messages	on it
	   are replied to their	origin message port.

       pth_msgport_t pth_msgport_find(const char *name);
	   This	finds a	message	port in	the system by name and returns the
	   pointer to it.

       int pth_msgport_pending(pth_msgport_t mp);
	   This	returns	the number of pending messages on message port mp.

       int pth_msgport_put(pth_msgport_t mp, pth_message_t *m);
	   This	puts (or sends)	a message m to message port mp.

       pth_message_t *pth_msgport_get(pth_msgport_t mp);
	   This	gets (or receives) the top message from	message	port mp.
	   Incoming messages are always	kept in	a queue, so there can be more
	   pending messages, of	course.

       int pth_msgport_reply(pth_message_t *m);
	   This	replies	a message m to the message port	of the sender.

   Thread Cleanups
       Per-thread cleanup functions.

       int pth_cleanup_push(void (*handler)(void *), void *arg);
	   This	pushes the routine handler onto	the stack of cleanup routines
	   for the current thread.  These routines are called in LIFO order
	   when	the thread terminates.

       int pth_cleanup_pop(int execute);
	   This	pops the top-most routine from the stack of cleanup routines
	   for the current thread. When	execute	is "TRUE" the routine is
	   additionally	called.

   Process Forking
       The following functions provide some special support for	process
       forking situations inside the threading environment.

       int pth_atfork_push(void	(*prepare)(void	*), void (*)(void *parent),
       void (*)(void *child), void *arg);
	   This	function declares forking handlers to be called	before and
	   after pth_fork(3), in the context of	the thread that	called
	   pth_fork(3).	The prepare handler is called before fork(2)
	   processing commences. The parent handler is called	after fork(2)
	   processing completes	in the parent process.	The child handler is
	   called after	fork(2)	processing completed in	the child process. If
	   no handling is desired at one or more of these three	points,	the
	   corresponding handler can be	given as "NULL".  Each handler is
	   called with arg as the argument.

	   The order of	calls to pth_atfork_push(3) is significant. The	parent
	   and child handlers are called in the	order in which they were
	   established by calls	to pth_atfork_push(3), i.e., FIFO. The prepare
	   fork	handlers are called in the opposite order, i.e., LIFO.

       int pth_atfork_pop(void);
	   This	removes	the top-most handlers on the forking handler stack
	   which were established with the last	pth_atfork_push(3) call. It
	   returns "FALSE" when	no more	handlers couldn't be removed from the
	   stack.

       pid_t pth_fork(void);
	   This	is a variant of	fork(2)	with the difference that the current
	   thread only is forked into a	separate process, i.e.,	in the parent
	   process nothing changes while in the	child process all threads are
	   gone	except for the scheduler and the calling thread. When you
	   really want to duplicate all	threads	in the current process you
	   should use fork(2) directly.	But this is usually not	reasonable.
	   Additionally	this function takes care of forking handlers as
	   established by pth_fork_push(3).

   Synchronization
       The following functions provide synchronization support via mutual
       exclusion locks (mutex),	read-write locks (rwlock), condition variables
       (cond) and barriers (barrier). Keep in mind that	in a non-preemptive
       threading system	like Pth this might sound unnecessary at the first
       look, because a thread isn't interrupted	by the system. Actually	when
       you have	a critical code	section	which doesn't contain any pth_xxx()
       functions, you don't need any mutex to protect it, of course.

       But when	your critical code section contains any	pth_xxx() function the
       chance is high that these temporarily switch to the scheduler. And this
       way other threads can make progress and enter your critical code
       section,	too.  This is especially true for critical code	sections which
       implicitly or explicitly	use the	event mechanism.

       int pth_mutex_init(pth_mutex_t *mutex);
	   This	dynamically initializes	a mutex	variable of type
	   `"pth_mutex_t"'.  Alternatively one can also	use static
	   initialization via `"pth_mutex_t mutex = PTH_MUTEX_INIT"'.

       int pth_mutex_acquire(pth_mutex_t *mutex, int try, pth_event_t ev);
	   This	acquires a mutex mutex.	 If the	mutex is already locked	by
	   another thread, the current threads execution is suspended until
	   the mutex is	unlocked again or additionally the extra events	in ev
	   occurred (when ev is	not "NULL").  Recursive	locking	is explicitly
	   supported, i.e., a thread is	allowed	to acquire a mutex more	than
	   once	before its released. But it then also has be released the same
	   number of times until the mutex is again lockable by	others.	 When
	   try is "TRUE" this function never suspends execution. Instead it
	   returns "FALSE" with	"errno"	set to "EBUSY".

       int pth_mutex_release(pth_mutex_t *mutex);
	   This	decrements the recursion locking count on mutex	and when it is
	   zero	it releases the	mutex mutex.

       int pth_rwlock_init(pth_rwlock_t	*rwlock);
	   This	dynamically initializes	a read-write lock variable of type
	   `"pth_rwlock_t"'.  Alternatively one	can also use static
	   initialization via `"pth_rwlock_t rwlock = PTH_RWLOCK_INIT"'.

       int pth_rwlock_acquire(pth_rwlock_t *rwlock, int	op, int	try,
       pth_event_t ev);
	   This	acquires a read-only (when op is "PTH_RWLOCK_RD") or a read-
	   write (when op is "PTH_RWLOCK_RW") lock rwlock. When	the lock is
	   only	locked by other	threads	in read-only mode, the lock succeeds.
	   But when one	thread holds a read-write lock,	all locking attempts
	   suspend the current thread until this lock is released again.
	   Additionally	in ev events can be given to let the locking timeout,
	   etc.	When try is "TRUE" this	function never suspends	execution.
	   Instead it returns "FALSE" with "errno" set to "EBUSY".

       int pth_rwlock_release(pth_rwlock_t *rwlock);
	   This	releases a previously acquired (read-only or read-write) lock.

       int pth_cond_init(pth_cond_t *cond);
	   This	dynamically initializes	a condition variable variable of type
	   `"pth_cond_t"'.  Alternatively one can also use static
	   initialization via `"pth_cond_t cond	= PTH_COND_INIT"'.

       int pth_cond_await(pth_cond_t *cond, pth_mutex_t	*mutex,	pth_event_t
       ev);
	   This	awaits a condition situation. The caller has to	follow the
	   semantics of	the POSIX condition variables: mutex has to be
	   acquired before this	function is called. The	execution of the
	   current thread is then suspended either until the events in ev
	   occurred (when ev is	not "NULL") or cond was	notified by another
	   thread via pth_cond_notify(3).  While the thread is waiting,	mutex
	   is released.	Before it returns mutex	is reacquired.

       int pth_cond_notify(pth_cond_t *cond, int broadcast);
	   This	notified one or	all threads which are waiting on cond.	When
	   broadcast is	"TRUE" all thread are notified,	else only a single
	   (unspecified) one.

       int pth_barrier_init(pth_barrier_t *barrier, int	threshold);
	   This	dynamically initializes	a barrier variable of type
	   `"pth_barrier_t"'.  Alternatively one can also use static
	   initialization via `"pth_barrier_t barrier =
	   PTH_BARRIER_INIT("threadhold")"'.

       int pth_barrier_reach(pth_barrier_t *barrier);
	   This	function reaches a barrier barrier. If this is the last	thread
	   (as specified by threshold on init of barrier) all threads are
	   awakened.  Else the current thread is suspended until the last
	   thread reached the barrier and this way awakes all threads. The
	   function returns (beside "FALSE" on error) the value	"TRUE" for any
	   thread which	neither	reached	the barrier as the first nor the last
	   thread; "PTH_BARRIER_HEADLIGHT" for the thread which	reached	the
	   barrier as the first	thread and "PTH_BARRIER_TAILLIGHT" for the
	   thread which	reached	the barrier as the last	thread.

   Semaphore support
       The interface provides functions	to set/get the value of	a semaphore,
       increment it with arbitrary values, wait, until the value becomes
       bigger than a given value (without or with decrementing,	if the
       condition becomes true.

       The data-type for the semaphore is names	"pth_sem_t" and	it has an
       initializer like	"pth_cond_t".

       int pth_sem_init(pth_sem_t *sem);
	   This	dynamically initializes	a semaphore variable of	type
	   `"pth_sem_t"'.  Alternatively one can also use static
	   initialization via `"pth_sem_t semaphore = PTH_SEM_INIT"'.

       int pth_sem_dec(pth_sem_t *sem);
	   waits, until	the value of "sem" is >= 1 and decrement it.

       int pth_sem_dec_value(pth_sem_t *sem, unsigned value);
	   waits, until	the value of "sem" is >= "value" and subtracts
	   "value".

       int pth_sem_inc(pth_sem_t *sem, int notify);
	   increments "sem". The scheduler is started, if "notify" is not
	   null.

       int pth_sem_inc_value(pth_sem_t *sem, unsigned value, int notify);
	   adds	value to "sem".	The scheduler is started, if "notify" is not
	   null.

       int pth_sem_set_value(pth_sem_t *sem, unsigned value);
	   sets	the value of "sem" to "value".

       int pth_sem_get_value(pth_sem_t *sem, unsigned *value);
	   stores the value of "sem" in	*"value".

   User-Space Context
       The following functions provide a stand-alone sub-API for user-space
       context switching. It internally	is based on the	same underlying
       machine context switching mechanism the threads in GNU Pth are based
       on.  Hence these	functions you can use for implementing your own	simple
       user-space threads. The "pth_uctx_t" context is somewhat	modeled	after
       POSIX ucontext(3).

       The time	required to create (via	pth_uctx_make(3)) a user-space context
       can range from just a few microseconds up to a more dramatical time
       (depending on the machine context switching method which	is available
       on the platform). On the	other hand, the	raw performance	in switching
       the user-space contexts is always very good (nearly independent of the
       used machine context switching method). For instance, on	an Intel
       Pentium-III CPU with 800Mhz running under FreeBSD 4 one usually
       achieves	about 260,000 user-space context switches (via
       pth_uctx_switch(3)) per second.

       int pth_uctx_create(pth_uctx_t *uctx);
	   This	function creates a user-space context and stores it into uctx.
	   There is still no underlying	user-space context configured. You
	   still have to do this with pth_uctx_make(3).	On success, this
	   function returns "TRUE", else "FALSE".

       int pth_uctx_make(pth_uctx_t uctx, char *sk_addr, size_t	sk_size, const
       sigset_t	*sigmask, void (*start_func)(void *), void *start_arg,
       pth_uctx_t uctx_after);
	   This	function makes a new user-space	context	in uctx	which will
	   operate on the run-time stack sk_addr (which	is of maximum size
	   sk_size), with the signals in sigmask blocked (if sigmask is	not
	   "NULL") and starting	to execute with	the call
	   start_func(start_arg). If sk_addr is	"NULL",	a stack	is dynamically
	   allocated. The stack	size sk_size has to be at least	16384 (16KB).
	   If the start	function start_func returns and	uctx_after is not
	   "NULL", an implicit user-space context switch to this context is
	   performed. Else (if uctx_after is "NULL") the process is terminated
	   with	exit(3). This function is somewhat modeled after POSIX
	   makecontext(3). On success, this function returns "TRUE", else
	   "FALSE".

       int pth_uctx_switch(pth_uctx_t uctx_from, pth_uctx_t uctx_to);
	   This	function saves the current user-space context in uctx_from for
	   later restoring by another call to pth_uctx_switch(3) and restores
	   the new user-space context from uctx_to, which previously had to be
	   set with either a previous call to pth_uctx_switch(3) or initially
	   by pth_uctx_make(3).	This function is somewhat modeled after	POSIX
	   swapcontext(3). If uctx_from	or uctx_to are "NULL" or if uctx_to
	   contains no valid user-space	context, "FALSE" is returned instead
	   of "TRUE". These are	the only errors	possible.

       int pth_uctx_destroy(pth_uctx_t uctx);
	   This	function destroys the user-space context in uctx. The run-time
	   stack associated with the user-space	context	is deallocated only if
	   it was not given by the application (see sk_addr of
	   pth_uctx_create(3)).	 If uctx is "NULL", "FALSE" is returned
	   instead of "TRUE". This is the only error possible.

   Generalized POSIX Replacement API
       The following functions are generalized replacements functions for the
       POSIX API, i.e.,	they are similar to the	functions under	`Standard
       POSIX Replacement API' but all have an additional event argument	which
       can be used for timeouts, etc.

       int pth_sigwait_ev(const	sigset_t *set, int *sig, pth_event_t ev);
	   This	is equal to pth_sigwait(3) (see	below),	but has	an additional
	   event argument ev. When pth_sigwait(3) suspends the current threads
	   execution it	usually	only uses the signal event on set to awake.
	   With	this function any number of extra events can be	used to	awake
	   the current thread (remember	that ev	actually is an event ring).

       int pth_connect_ev(int s, const struct sockaddr *addr, socklen_t
       addrlen,	pth_event_t ev);
	   This	is equal to pth_connect(3) (see	below),	but has	an additional
	   event argument ev. When pth_connect(3) suspends the current threads
	   execution it	usually	only uses the I/O event	on s to	awake. With
	   this	function any number of extra events can	be used	to awake the
	   current thread (remember that ev actually is	an event ring).

       int pth_accept_ev(int s,	struct sockaddr	*addr, socklen_t *addrlen,
       pth_event_t ev);
	   This	is equal to pth_accept(3) (see below), but has an additional
	   event argument ev. When pth_accept(3) suspends the current threads
	   execution it	usually	only uses the I/O event	on s to	awake. With
	   this	function any number of extra events can	be used	to awake the
	   current thread (remember that ev actually is	an event ring).

       int pth_select_ev(int nfd, fd_set *rfds,	fd_set *wfds, fd_set *efds,
       struct timeval *timeout,	pth_event_t ev);
	   This	is equal to pth_select(3) (see below), but has an additional
	   event argument ev. When pth_select(3) suspends the current threads
	   execution it	usually	only uses the I/O event	on rfds, wfds and efds
	   to awake. With this function	any number of extra events can be used
	   to awake the	current	thread (remember that ev actually is an	event
	   ring).

       int pth_poll_ev(struct pollfd *fds, unsigned int	nfd, int timeout,
       pth_event_t ev);
	   This	is equal to pth_poll(3)	(see below), but has an	additional
	   event argument ev. When pth_poll(3) suspends	the current threads
	   execution it	usually	only uses the I/O event	on fds to awake. With
	   this	function any number of extra events can	be used	to awake the
	   current thread (remember that ev actually is	an event ring).

       ssize_t pth_read_ev(int fd, void	*buf, size_t nbytes, pth_event_t ev);
	   This	is equal to pth_read(3)	(see below), but has an	additional
	   event argument ev. When pth_read(3) suspends	the current threads
	   execution it	usually	only uses the I/O event	on fd to awake.	With
	   this	function any number of extra events can	be used	to awake the
	   current thread (remember that ev actually is	an event ring).

       ssize_t pth_readv_ev(int	fd, const struct iovec *iovec, int iovcnt,
       pth_event_t ev);
	   This	is equal to pth_readv(3) (see below), but has an additional
	   event argument ev. When pth_readv(3)	suspends the current threads
	   execution it	usually	only uses the I/O event	on fd to awake.	With
	   this	function any number of extra events can	be used	to awake the
	   current thread (remember that ev actually is	an event ring).

       ssize_t pth_write_ev(int	fd, const void *buf, size_t nbytes,
       pth_event_t ev);
	   This	is equal to pth_write(3) (see below), but has an additional
	   event argument ev. When pth_write(3)	suspends the current threads
	   execution it	usually	only uses the I/O event	on fd to awake.	With
	   this	function any number of extra events can	be used	to awake the
	   current thread (remember that ev actually is	an event ring).

       ssize_t pth_writev_ev(int fd, const struct iovec	*iovec,	int iovcnt,
       pth_event_t ev);
	   This	is equal to pth_writev(3) (see below), but has an additional
	   event argument ev. When pth_writev(3) suspends the current threads
	   execution it	usually	only uses the I/O event	on fd to awake.	With
	   this	function any number of extra events can	be used	to awake the
	   current thread (remember that ev actually is	an event ring).

       ssize_t pth_recv_ev(int fd, void	*buf, size_t nbytes, int flags,
       pth_event_t ev);
	   This	is equal to pth_recv(3)	(see below), but has an	additional
	   event argument ev. When pth_recv(3) suspends	the current threads
	   execution it	usually	only uses the I/O event	on fd to awake.	With
	   this	function any number of extra events can	be used	to awake the
	   current thread (remember that ev actually is	an event ring).

       ssize_t pth_recvfrom_ev(int fd, void *buf, size_t nbytes, int flags,
       struct sockaddr *from, socklen_t	*fromlen, pth_event_t ev);
	   This	is equal to pth_recvfrom(3) (see below), but has an additional
	   event argument ev. When pth_recvfrom(3) suspends the	current
	   threads execution it	usually	only uses the I/O event	on fd to
	   awake. With this function any number	of extra events	can be used to
	   awake the current thread (remember that ev actually is an event
	   ring).

       ssize_t pth_send_ev(int fd, const void *buf, size_t nbytes, int flags,
       pth_event_t ev);
	   This	is equal to pth_send(3)	(see below), but has an	additional
	   event argument ev. When pth_send(3) suspends	the current threads
	   execution it	usually	only uses the I/O event	on fd to awake.	With
	   this	function any number of extra events can	be used	to awake the
	   current thread (remember that ev actually is	an event ring).

       ssize_t pth_sendto_ev(int fd, const void	*buf, size_t nbytes, int
       flags, const struct sockaddr *to, socklen_t tolen, pth_event_t ev);
	   This	is equal to pth_sendto(3) (see below), but has an additional
	   event argument ev. When pth_sendto(3) suspends the current threads
	   execution it	usually	only uses the I/O event	on fd to awake.	With
	   this	function any number of extra events can	be used	to awake the
	   current thread (remember that ev actually is	an event ring).

   Standard POSIX Replacement API
       The following functions are standard replacements functions for the
       POSIX API.  The difference is mainly that they suspend the current
       thread only instead of the whole	process	in case	the file descriptors
       will block.

       int pth_nanosleep(const struct timespec *rqtp, struct timespec *rmtp);
	   This	is a variant of	the POSIX nanosleep(3) function. It suspends
	   the current threads execution until the amount of time in rqtp
	   elapsed.  The thread	is guaranteed to not wake up before this time,
	   but because of the non-preemptive scheduling	nature of Pth, it can
	   be awakened later, of course. If rmtp is not	"NULL",	the "timespec"
	   structure it	references is updated to contain the unslept amount
	   (the	request	time minus the time actually slept time). The
	   difference between nanosleep(3) and pth_nanosleep(3)	is that	that
	   pth_nanosleep(3) suspends only the execution	of the current thread
	   and not the whole process.

       int pth_usleep(unsigned int usec);
	   This	is a variant of	the 4.3BSD usleep(3) function. It suspends the
	   current threads execution until usec	microseconds (=	usec*1/1000000
	   sec)	elapsed.  The thread is	guaranteed to not wake up before this
	   time, but because of	the non-preemptive scheduling nature of	Pth,
	   it can be awakened later, of	course.	 The difference	between
	   usleep(3) and pth_usleep(3) is that that pth_usleep(3) suspends
	   only	the execution of the current thread and	not the	whole process.

       unsigned	int pth_sleep(unsigned int sec);
	   This	is a variant of	the POSIX sleep(3) function. It	suspends the
	   current threads execution until sec seconds elapsed.	 The thread is
	   guaranteed to not wake up before this time, but because of the non-
	   preemptive scheduling nature	of Pth,	it can be awakened later, of
	   course.  The	difference between sleep(3) and	pth_sleep(3) is	that
	   pth_sleep(3)	suspends only the execution of the current thread and
	   not the whole process.

       pid_t pth_waitpid(pid_t pid, int	*status, int options);
	   This	is a variant of	the POSIX waitpid(2) function. It suspends the
	   current threads execution until status information is available for
	   a terminated	child process pid.  The	difference between waitpid(2)
	   and pth_waitpid(3) is that pth_waitpid(3) suspends only the
	   execution of	the current thread and not the whole process.  For
	   more	details	about the arguments and	return code semantics see
	   waitpid(2).

       int pth_system(const char *cmd);
	   This	is a variant of	the POSIX system(3) function. It executes the
	   shell command cmd with Bourne Shell ("sh") and suspends the current
	   threads execution until this	command	terminates. The	difference
	   between system(3) and pth_system(3) is that pth_system(3) suspends
	   only	the execution of the current thread and	not the	whole process.
	   For more details about the arguments	and return code	semantics see
	   system(3).

       int pth_sigmask(int how,	const sigset_t *set, sigset_t *oset)
	   This	is the Pth thread-related equivalent of	POSIX sigprocmask(2)
	   respectively	pthread_sigmask(3). The	arguments how, set and oset
	   directly relate to sigprocmask(2), because Pth internally just uses
	   sigprocmask(2) here.	So alternatively you can also directly call
	   sigprocmask(2), but for consistency reasons you should use this
	   function pth_sigmask(3).

       int pth_sigwait(const sigset_t *set, int	*sig);
	   This	is a variant of	the POSIX.1c sigwait(3)	function. It suspends
	   the current threads execution until a signal	in set occurred	and
	   stores the signal number in sig. The	important point	is that	the
	   signal is not delivered to a	signal handler.	Instead	it's caught by
	   the scheduler only in order to awake	the pth_sigwait() call.	The
	   trick and noticeable	point here is that this	way you	get an
	   asynchronous	aware application that is written completely
	   synchronously. When you think about the problem of asynchronous
	   safe	functions you should recognize that this is a great benefit.

       int pth_connect(int s, const struct sockaddr *addr, socklen_t addrlen);
	   This	is a variant of	the 4.2BSD connect(2) function.	It establishes
	   a connection	on a socket s to target	specified in addr and addrlen.
	   The difference between connect(2) and pth_connect(3)	is that
	   pth_connect(3) suspends only	the execution of the current thread
	   and not the whole process.  For more	details	about the arguments
	   and return code semantics see connect(2).

       int pth_accept(int s, struct sockaddr *addr, socklen_t *addrlen);
	   This	is a variant of	the 4.2BSD accept(2) function. It accepts a
	   connection on a socket by extracting	the first connection request
	   on the queue	of pending connections,	creating a new socket with the
	   same	properties of s	and allocates a	new file descriptor for	the
	   socket (which is returned).	The difference between accept(2) and
	   pth_accept(3) is that pth_accept(3) suspends	only the execution of
	   the current thread and not the whole	process.  For more details
	   about the arguments and return code semantics see accept(2).

       int pth_select(int nfd, fd_set *rfds, fd_set *wfds, fd_set *efds,
       struct timeval *timeout);
	   This	is a variant of	the 4.2BSD select(2) function.	It examines
	   the I/O descriptor sets whose addresses are passed in rfds, wfds,
	   and efds to see if some of their descriptors	are ready for reading,
	   are ready for writing, or have an exceptional condition pending,
	   respectively.  For more details about the arguments and return code
	   semantics see select(2).

       int pth_pselect(int nfd,	fd_set *rfds, fd_set *wfds, fd_set *efds,
       const struct timespec *timeout, const sigset_t *sigmask);
	   This	is a variant of	the POSIX pselect(2) function, which in	turn
	   is a	stronger variant of 4.2BSD select(2). The difference is	that
	   the higher-resolution "struct timespec" is passed instead of	the
	   lower-resolution "struct timeval" and that a	signal mask is
	   specified which is temporarily set while waiting for	input. For
	   more	details	about the arguments and	return code semantics see
	   pselect(2) and select(2).

       int pth_poll(struct pollfd *fds,	unsigned int nfd, int timeout);
	   This	is a variant of	the SysV poll(2) function. It examines the I/O
	   descriptors which are passed	in the array fds to see	if some	of
	   them	are ready for reading, are ready for writing, or have an
	   exceptional condition pending, respectively.	For more details about
	   the arguments and return code semantics see poll(2).

       ssize_t pth_read(int fd,	void *buf, size_t nbytes);
	   This	is a variant of	the POSIX read(2) function. It reads up	to
	   nbytes bytes	into buf from file descriptor fd.  The difference
	   between read(2) and pth_read(2) is that pth_read(2) suspends
	   execution of	the current thread until the file descriptor is	ready
	   for reading.	For more details about the arguments and return	code
	   semantics see read(2).

       ssize_t pth_readv(int fd, const struct iovec *iovec, int	iovcnt);
	   This	is a variant of	the POSIX readv(2) function. It	reads data
	   from	file descriptor	fd into	the first iovcnt rows of the iov
	   vector.  The	difference between readv(2) and	pth_readv(2) is	that
	   pth_readv(2)	suspends execution of the current thread until the
	   file	descriptor is ready for	reading. For more details about	the
	   arguments and return	code semantics see readv(2).

       ssize_t pth_write(int fd, const void *buf, size_t nbytes);
	   This	is a variant of	the POSIX write(2) function. It	writes nbytes
	   bytes from buf to file descriptor fd.  The difference between
	   write(2) and	pth_write(2) is	that pth_write(2) suspends execution
	   of the current thread until the file	descriptor is ready for
	   writing.  For more details about the	arguments and return code
	   semantics see write(2).

       ssize_t pth_writev(int fd, const	struct iovec *iovec, int iovcnt);
	   This	is a variant of	the POSIX writev(2) function. It writes	data
	   to file descriptor fd from the first	iovcnt rows of the iov vector.
	   The difference between writev(2) and	pth_writev(2) is that
	   pth_writev(2) suspends execution of the current thread until	the
	   file	descriptor is ready for	reading. For more details about	the
	   arguments and return	code semantics see writev(2).

       ssize_t pth_pread(int fd, void *buf, size_t nbytes, off_t offset);
	   This	is a variant of	the POSIX pread(3) function.  It performs the
	   same	action as a regular read(2), except that it reads from a given
	   position in the file	without	changing the file pointer.  The	first
	   three arguments are the same	as for pth_read(3) with	the addition
	   of a	fourth argument	offset for the desired position	inside the
	   file.

       ssize_t pth_pwrite(int fd, const	void *buf, size_t nbytes, off_t
       offset);
	   This	is a variant of	the POSIX pwrite(3) function.  It performs the
	   same	action as a regular write(2), except that it writes to a given
	   position in the file	without	changing the file pointer. The first
	   three arguments are the same	as for pth_write(3) with the addition
	   of a	fourth argument	offset for the desired position	inside the
	   file.

       ssize_t pth_recv(int fd,	void *buf, size_t nbytes, int flags);
	   This	is a variant of	the SUSv2 recv(2) function and equal to
	   ``pth_recvfrom(fd, buf, nbytes, flags, NULL,	0)''.

       ssize_t pth_recvfrom(int	fd, void *buf, size_t nbytes, int flags,
       struct sockaddr *from, socklen_t	*fromlen);
	   This	is a variant of	the SUSv2 recvfrom(2) function.	It reads up to
	   nbytes bytes	into buf from file descriptor fd while using flags and
	   from/fromlen. The difference	between	recvfrom(2) and
	   pth_recvfrom(2) is that pth_recvfrom(2) suspends execution of the
	   current thread until	the file descriptor is ready for reading. For
	   more	details	about the arguments and	return code semantics see
	   recvfrom(2).

       ssize_t pth_send(int fd,	const void *buf, size_t	nbytes,	int flags);
	   This	is a variant of	the SUSv2 send(2) function and equal to
	   ``pth_sendto(fd, buf, nbytes, flags,	NULL, 0)''.

       ssize_t pth_sendto(int fd, const	void *buf, size_t nbytes, int flags,
       const struct sockaddr *to, socklen_t tolen);
	   This	is a variant of	the SUSv2 sendto(2) function. It writes	nbytes
	   bytes from buf to file descriptor fd	while using flags and
	   to/tolen. The difference between sendto(2) and pth_sendto(2)	is
	   that	pth_sendto(2) suspends execution of the	current	thread until
	   the file descriptor is ready	for writing. For more details about
	   the arguments and return code semantics see sendto(2).

EXAMPLE
       The following example is	a useless server which does nothing more than
       listening on TCP	port 12345 and displaying the current time to the
       socket when a connection	was established. For each incoming connection
       a thread	is spawned. Additionally, to see more multithreading, a
       useless ticker thread runs simultaneously which outputs the current
       time to "stderr"	every 5	seconds. The example contains no error
       checking	and is only intended to	show you the look and feel of Pth.

	#include <stdio.h>
	#include <stdlib.h>
	#include <errno.h>
	#include <sys/types.h>
	#include <sys/socket.h>
	#include <netinet/in.h>
	#include <arpa/inet.h>
	#include <signal.h>
	#include <netdb.h>
	#include <unistd.h>
	#include "pth.h"

	#define	PORT 12345

	/* the socket connection handler thread	*/
	static void *handler(void *_arg)
	{
	    int	fd = (int)_arg;
	    time_t now;
	    char *ct;

	    now	= time(NULL);
	    ct = ctime(&now);
	    pth_write(fd, ct, strlen(ct));
	    close(fd);
	    return NULL;
	}

	/* the stderr time ticker thread */
	static void *ticker(void *_arg)
	{
	    time_t now;
	    char *ct;
	    float load;

	    for	(;;) {
		pth_sleep(5);
		now = time(NULL);
		ct = ctime(&now);
		ct[strlen(ct)-1] = '\0';
		pth_ctrl(PTH_CTRL_GETAVLOAD, &load);
		printf("ticker:	time: %s, average load:	%.2f\n", ct, load);
	    }
	}

	/* the main thread/procedure */
	int main(int argc, char	*argv[])
	{
	    pth_attr_t attr;
	    struct sockaddr_in sar;
	    struct protoent *pe;
	    struct sockaddr_in peer_addr;
	    int	peer_len;
	    int	sa, sw;
	    int	port;

	    pth_init();
	    signal(SIGPIPE, SIG_IGN);

	    attr = pth_attr_new();
	    pth_attr_set(attr, PTH_ATTR_NAME, "ticker");
	    pth_attr_set(attr, PTH_ATTR_STACK_SIZE, 64*1024);
	    pth_attr_set(attr, PTH_ATTR_JOINABLE, FALSE);
	    pth_spawn(attr, ticker, NULL);

	    pe = getprotobyname("tcp");
	    sa = socket(AF_INET, SOCK_STREAM, pe->p_proto);
	    sar.sin_family = AF_INET;
	    sar.sin_addr.s_addr	= INADDR_ANY;
	    sar.sin_port = htons(PORT);
	    bind(sa, (struct sockaddr *)&sar, sizeof(struct sockaddr_in));
	    listen(sa, 10);

	    pth_attr_set(attr, PTH_ATTR_NAME, "handler");
	    for	(;;) {
		peer_len = sizeof(peer_addr);
		sw = pth_accept(sa, (struct sockaddr *)&peer_addr, &peer_len);
		pth_spawn(attr,	handler, (void *)sw);
	    }
	}

BUILD ENVIRONMENTS
       In this section we will discuss the canonical ways to establish the
       build environment for a Pth based program. The possibilities supported
       by Pth range from very simple environments to rather complex ones.

   Manual Build	Environment (Novice)
       As a first example, assume we have the above test program staying in
       the source file "foo.c".	Then we	can create a very simple build
       environment by just adding the following	"Makefile":

	$ vi Makefile
	| CC	  = cc
	| CFLAGS  = `pth-config	--cflags`
	| LDFLAGS = `pth-config	--ldflags`
	| LIBS	  = `pth-config	--libs`
	|
	| all: foo
	| foo: foo.o
	|     $(CC) $(LDFLAGS) -o foo foo.o $(LIBS)
	| foo.o: foo.c
	|     $(CC) $(CFLAGS) -c foo.c
	| clean:
	|     rm -f foo	foo.o

       This imports the	necessary compiler and linker flags on-the-fly from
       the Pth installation via	its "pth-config" program. This approach	is
       straight-forward	and works fine for small projects.

   Autoconf Build Environment (Advanced)
       The previous approach is	simple but inflexible. First, to speed up
       building, it would be nice to not expand	the compiler and linker	flags
       every time the compiler is started. Second, it would be useful to also
       be able to build	against	uninstalled Pth, that is, against a Pth	source
       tree which was just configured and built, but not installed. Third, it
       would be	also useful to allow checking of the Pth version to make sure
       it is at	least a	minimum	required version.  And finally,	it would be
       also great to make sure Pth works correctly by first performing some
       sanity compile and run-time checks. All this can	be done	if we use GNU
       autoconf	and the	"AC_CHECK_PTH" macro provided by Pth. For this,	we
       establish the following three files:

       First we	again need the "Makefile", but this time it contains autoconf
       placeholders and	additional cleanup targets. And	we create it under the
       name "Makefile.in", because it is now an	input file for autoconf:

	$ vi Makefile.in
	| CC	  = @CC@
	| CFLAGS  = @CFLAGS@
	| LDFLAGS = @LDFLAGS@
	| LIBS	  = @LIBS@
	|
	| all: foo
	| foo: foo.o
	|     $(CC) $(LDFLAGS) -o foo foo.o $(LIBS)
	| foo.o: foo.c
	|     $(CC) $(CFLAGS) -c foo.c
	| clean:
	|     rm -f foo	foo.o
	| distclean:
	|     rm -f foo	foo.o
	|     rm -f config.log config.status config.cache
	|     rm -f Makefile

       Because autoconf	generates additional files, we added a canonical
       "distclean" target which	cleans this up.	Secondly, we wrote
       "configure.ac", a (minimal) autoconf script specification:

	$ vi configure.ac
	| AC_INIT(Makefile.in)
	| AC_CHECK_PTH(1.3.0)
	| AC_OUTPUT(Makefile)

       Then we let autoconf's "aclocal"	program	generate for us	an
       "aclocal.m4" file containing Pth's "AC_CHECK_PTH" macro.	Then we
       generate	the final "configure" script out of this "aclocal.m4" file and
       the "configure.ac" file:

	$ aclocal --acdir=`pth-config --acdir`
	$ autoconf

       After these steps, the working directory	should look similar to this:

	$ ls -l
	-rw-r--r--  1 rse  users    176	Nov  3 11:11 Makefile.in
	-rw-r--r--  1 rse  users  15314	Nov  3 11:16 aclocal.m4
	-rwxr-xr-x  1 rse  users  52045	Nov  3 11:16 configure
	-rw-r--r--  1 rse  users     63	Nov  3 11:11 configure.ac
	-rw-r--r--  1 rse  users   4227	Nov  3 11:11 foo.c

       If we now run "configure" we get	a correct "Makefile" which immediately
       can be used to build "foo" (assuming that Pth is	already	installed
       somewhere, so that "pth-config" is in $PATH):

	$ ./configure
	creating cache ./config.cache
	checking for gcc... gcc
	checking whether the C compiler	(gcc   ) works... yes
	checking whether the C compiler	(gcc   ) is a cross-compiler...	no
	checking whether we are	using GNU C... yes
	checking whether gcc accepts -g... yes
	checking how to	run the	C preprocessor... gcc -E
	checking for GNU Pth...	version	1.3.0, installed under /usr/local
	updating cache ./config.cache
	creating ./config.status
	creating Makefile
	rse@en1:/e/gnu/pth/ac
	$ make
	gcc -g -O2 -I/usr/local/include	-c foo.c
	gcc -L/usr/local/lib -o	foo foo.o -lpth

       If Pth is installed in non-standard locations or	"pth-config" is	not in
       $PATH, one just has to drop the "configure" script a note about the
       location	by running "configure" with the	option "--with-pth="dir	(where
       dir is the argument which was used with the "--prefix" option when Pth
       was installed).

   Autoconf Build Environment with Local Copy of Pth (Expert)
       Finally let us assume the "foo" program stays under either a GPL	or
       LGPL distribution license and we	want to	make it	a stand-alone package
       for easier distribution and installation.  That is, we don't want to
       oblige the end-user to install Pth just to allow	our "foo" package to
       compile.	For this, it is	a convenient practice to include the required
       libraries (here Pth) into the source tree of the	package	(here "foo").
       Pth ships with all necessary support to allow us	to easily achieve this
       approach. Say, we want Pth in a subdirectory named "pth/" and this
       directory should	be seamlessly integrated into the configuration	and
       build process of	"foo".

       First we	again start with the "Makefile.in", but	this time it is	a more
       advanced	version	which supports subdirectory movement:

	$ vi Makefile.in
	| CC	  = @CC@
	| CFLAGS  = @CFLAGS@
	| LDFLAGS = @LDFLAGS@
	| LIBS	  = @LIBS@
	|
	| SUBDIRS = pth
	|
	| all: subdirs_all foo
	|
	| subdirs_all:
	|     @$(MAKE) $(MFLAGS) subdirs TARGET=all
	| subdirs_clean:
	|     @$(MAKE) $(MFLAGS) subdirs TARGET=clean
	| subdirs_distclean:
	|     @$(MAKE) $(MFLAGS) subdirs TARGET=distclean
	| subdirs:
	|     @for subdir in $(SUBDIRS); do \
	|	  echo "===> $$subdir ($(TARGET))"; \
	|	  (cd $$subdir;	$(MAKE)	$(MFLAGS) $(TARGET) || exit 1) || exit 1; \
	|	  echo "<=== $$subdir";	\
	|     done
	|
	| foo: foo.o
	|     $(CC) $(LDFLAGS) -o foo foo.o $(LIBS)
	| foo.o: foo.c
	|     $(CC) $(CFLAGS) -c foo.c
	|
	| clean: subdirs_clean
	|     rm -f foo	foo.o
	| distclean: subdirs_distclean
	|     rm -f foo	foo.o
	|     rm -f config.log config.status config.cache
	|     rm -f Makefile

       Then we create a	slightly different autoconf script "configure.ac":

	$ vi configure.ac
	| AC_INIT(Makefile.in)
	| AC_CONFIG_AUX_DIR(pth)
	| AC_CHECK_PTH(1.3.0, subdir:pth --disable-tests)
	| AC_CONFIG_SUBDIRS(pth)
	| AC_OUTPUT(Makefile)

       Here we provided	a default value	for "foo"'s "--with-pth" option	as the
       second argument to "AC_CHECK_PTH" which indicates that Pth can be found
       in the subdirectory named "pth/". Additionally we specified that	the
       "--disable-tests" option	of Pth should be passed	to the "pth/"
       subdirectory, because we	need only to build the Pth library itself. And
       we added	a "AC_CONFIG_SUBDIR" call which	indicates to autoconf that it
       should configure	the "pth/" subdirectory, too. The "AC_CONFIG_AUX_DIR"
       directive was added just	to make	autoconf happy,	because	it wants to
       find a "install.sh" or "shtool" script if "AC_CONFIG_SUBDIRS" is	used.

       Now we let autoconf's "aclocal" program again generate for us an
       "aclocal.m4" file with the contents of Pth's "AC_CHECK_PTH" macro.
       Finally we generate the "configure" script out of this "aclocal.m4"
       file and	the "configure.ac" file.

	$ aclocal --acdir=`pth-config --acdir`
	$ autoconf

       Now we have to create the "pth/"	subdirectory itself. For this, we
       extract the Pth distribution to the "foo" source	tree and just rename
       it to "pth/":

	$ gunzip <pth-X.Y.Z.tar.gz | tar xvf -
	$ mv pth-X.Y.Z pth

SYSTEM CALL WRAPPER FACILITY
       Pth per default uses an explicit	API, including the system calls. For
       instance	you've to explicitly use pth_read(3) when you need a thread-
       aware read(3) and cannot	expect that by just calling read(3) only the
       current thread is blocked. Instead with the standard read(3) call the
       whole process will be blocked. But because for some applications
       (mainly those consisting	of lots	of third-party stuff) this can be
       inconvenient.  Here it's	required that a	call to	read(3)	`magically'
       means pth_read(3). The problem here is that such	magic Pth cannot
       provide per default because it's	not really portable.  Nevertheless Pth
       provides	a two step approach to solve this problem:

   Soft	System Call Mapping
       This variant is available on all	platforms and can always be enabled by
       building	Pth with "--enable-syscall-soft". This then triggers some
       "#define"'s in the "pth.h" header which map for instance	read(3)	to
       pth_read(3), etc. Currently the following functions are mapped:
       fork(2),	nanosleep(3), usleep(3), sleep(3), sigwait(3), waitpid(2),
       system(3), select(2), poll(2), connect(2), accept(2), read(2),
       write(2), recv(2), send(2), recvfrom(2),	sendto(2).

       The drawback of this approach is	just that really all source files of
       the application where these function calls occur	have to	include
       "pth.h",	of course. And this also means that existing libraries,
       including the vendor's stdio, usually will still	block the whole
       process if one of its I/O functions block.

   Hard	System Call Mapping
       This variant is available only on those platforms where the syscall(2)
       function	exists and there it can	be enabled by building Pth with
       "--enable-syscall-hard".	This then builds wrapper functions (for
       instances read(3)) into the Pth library which internally	call the real
       Pth replacement functions (pth_read(3)).	Currently the following
       functions are mapped: fork(2), nanosleep(3), usleep(3), sleep(3),
       waitpid(2), system(3), select(2), poll(2), connect(2), accept(2),
       read(2),	write(2).

       The drawback of this approach is	that it	depends	on syscall(2)
       interface and prototype conflicts can occur while building the wrapper
       functions due to	different function signatures in the vendor C header
       files.  But the advantage of this mapping variant is that the source
       files of	the application	where these function calls occur have not to
       include "pth.h" and that	existing libraries, including the vendor's
       stdio, magically	become thread-aware (and then block only the current
       thread).

IMPLEMENTATION NOTES
       Pth is very portable because it has only	one part which perhaps has to
       be ported to new	platforms (the machine context initialization).	But it
       is written in a way which works on mostly all Unix platforms which
       support makecontext(2) or at least sigstack(2) or sigaltstack(2)	[see
       "pth_mctx.c" for	details]. Any other Pth	code is	POSIX and ANSI C based
       only.

       The context switching is	done via either	SUSv2 makecontext(2) or	POSIX
       make[sig]setjmp(3) and [sig]longjmp(3). Here all	CPU registers, the
       program counter and the stack pointer are switched. Additionally	the
       Pth dispatcher switches also the	global Unix "errno" variable [see
       "pth_mctx.c" for	details] and the signal	mask (either implicitly	via
       sigsetjmp(3) or in an emulated way via explicit setprocmask(2) calls).

       The Pth event manager is	mainly select(2) and gettimeofday(2) based,
       i.e., the current time is fetched via gettimeofday(2) once per context
       switch for time calculations and	all I/O	events are implemented via a
       single central select(2)	call [see "pth_sched.c"	for details].

       The thread control block	management is done via virtual priority	queues
       without any additional data structure overhead. For this, the queue
       linkage attributes are part of the thread control blocks	and the	queues
       are actually implemented	as rings with a	selected element as the	entry
       point [see "pth_tcb.h" and "pth_pqueue.c" for details].

       Most time critical code sections	(especially the	dispatcher and event
       manager)	are speeded up by inline functions (implemented	as ANSI	C pre-
       processor macros). Additionally any debugging code is completely
       removed from the	source when not	built with "-DPTH_DEBUG" (see Autoconf
       "--enable-debug"	option), i.e., not only	stub functions remain [see
       "pth_debug.c" for details].

RESTRICTIONS
       Pth (intentionally) provides no replacements for	non-thread-safe
       functions (like strtok(3) which uses a static internal buffer) or
       synchronous system functions (like gethostbyname(3) which doesn't
       provide an asynchronous mode where it doesn't block). When you want to
       use those functions in your server application together with threads,
       you've to either	link the application against special third-party
       libraries (or for thread-safe/reentrant functions possibly against an
       existing	"libc_r" of the	platform vendor). For an asynchronous DNS
       resolver	library	use the	GNU adns package from Ian Jackson ( see
       http://www.gnu.org/software/adns/adns.html ).

HISTORY
       The Pth library was designed and	implemented between February and July
       1999 by Ralf S. Engelschall after evaluating numerous (mostly
       preemptive) thread libraries and	after intensive	discussions with Peter
       Simons, Martin Kraemer, Lars Eilebrecht and Ralph Babel related to an
       experimental (matrix based) non-preemptive C++ scheduler	class written
       by Peter	Simons.

       Pth was then implemented	in order to combine the	non-preemptive
       approach	of multithreading (which provides better portability and
       performance) with an API	similar	to the popular one found in Pthread
       libraries (which	provides easy programming).

       So the essential	idea of	the non-preemptive approach was	taken over
       from Peter Simons scheduler. The	priority based scheduling algorithm
       was suggested by	Martin Kraemer.	Some code inspiration also came	from
       an experimental threading library (rsthreads) written by	Robert S. Thau
       for an ancient internal test version of the Apache webserver.  The
       concept and API of message ports	was borrowed from AmigaOS' Exec
       subsystem. The concept and idea for the flexible	event mechanism	came
       from Paul Vixie's eventlib (which can be	found as a part	of BIND	v8).

BUG REPORTS AND	SUPPORT
       If you think you	have found a bug in Pth, you should send a report as
       complete	as possible to bug-pth@gnu.org.	If you can, please try to fix
       the problem and include a patch,	made with '"diff -u3"',	in your
       report. Always, at least, include a reasonable amount of	description in
       your report to allow the	author to deterministically reproduce the bug.

       For further support you additionally can	subscribe to the
       pth-users@gnu.org mailing list by sending an Email to
       pth-users-request@gnu.org with `"subscribe pth-users"' (or `"subscribe
       pth-users" address' if you want to subscribe from a particular Email
       address)	in the body. Then you can discuss your issues with other Pth
       users by	sending	messages to pth-users@gnu.org. Currently (as of	August
       2000) you can reach about 110 Pth users on this mailing list. Old
       postings	you can	find at
       http://www.mail-archive.com/pth-users@gnu.org/.

SEE ALSO
   Related Web Locations
       `comp.programming.threads Newsgroup Archive',
       http://www.deja.com/topics_if.xp?
       search=topic&group=comp.programming.threads

       `comp.programming.threads Frequently Asked Questions (F.A.Q.)',
       http://www.lambdacs.com/newsgroup/FAQ.html

       `Multithreading - Definitions and Guidelines', Numeric Quest Inc	1998;
       http://www.numeric-quest.com/lang/multi-frame.html

       `The Single UNIX	Specification, Version 2 - Threads', The Open Group
       1997; http://www.opengroup.org/onlinepubs /007908799/xsh/threads.html

       SMI Thread Resources, Sun Microsystems Inc;
       http://www.sun.com/workshop/threads/

       Bibliography on threads and multithreading, Torsten Amundsen;
       http://liinwww.ira.uka.de/bibliography/Os/threads.html

   Related Books
       B. Nichols, D. Buttlar, J.P. Farrel: `Pthreads Programming - A POSIX
       Standard	for Better Multiprocessing', O'Reilly 1996; ISBN 1-56592-115-1

       B. Lewis, D. J. Berg: `Multithreaded Programming	with Pthreads',	Sun
       Microsystems Press, Prentice Hall 1998; ISBN 0-13-680729-1

       B. Lewis, D. J. Berg: `Threads Primer - A Guide To Multithreaded
       Programming', Prentice Hall 1996; ISBN 0-13-443698-9

       S. J. Norton, M.	D. Dipasquale: `Thread Time - The Multithreaded
       Programming Guide', Prentice Hall 1997; ISBN 0-13-190067-6

       D. R. Butenhof: `Programming with POSIX Threads', Addison Wesley	1997;
       ISBN 0-201-63392-2

   Related Manpages
       pth-config(1), pthread(3).

       getcontext(2), setcontext(2), makecontext(2), swapcontext(2),
       sigstack(2), sigaltstack(2), sigaction(2), sigemptyset(2),
       sigaddset(2), sigprocmask(2), sigsuspend(2), sigsetjmp(3),
       siglongjmp(3), setjmp(3), longjmp(3), select(2),	gettimeofday(2).

AUTHOR
	Ralf S.	Engelschall
	rse@engelschall.com
	www.engelschall.com

2.0.8				 pthsem	2.0.8			     .::pth(3)

NAME | VERSION | SYNOPSIS | DESCRIPTION | APPLICATION PROGRAMMING INTERFACE (API) | EXAMPLE | BUILD ENVIRONMENTS | SYSTEM CALL WRAPPER FACILITY | IMPLEMENTATION NOTES | RESTRICTIONS | HISTORY | BUG REPORTS AND SUPPORT | SEE ALSO | AUTHOR

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