Compress-LZF/perlmulticore.h

/*
 * Author: Marc A. Lehmann <xsthreadpool@schmorp.de>
 * License: public domain, or where this is not possible/at your option,
 *          CC0 (https://creativecommons.org/publicdomain/zero/1.0/)
 */

#ifndef PERL_MULTICORE_H
#define PERL_MULTICORE_H

/*
=head1 NAME

perlmulticore.h - release the perl interpreter for other uses while doing hard work

=head1 SYNOPSIS

  #include "perlmultiore.h"

  // in your XS function:

  perlinterp_release ();
  do_the_C_thing ();
  perlinterp_acquire ();

=head1 DESCRIPTION

This header file implements a simple mechanism for XS modules to allow
re-use of the perl interpreter for other threads while doing some lengthy
operation, such as cryptography, SQL queries, disk I/O and so on.

The design goals for this mechanism were to be simple to use, very
efficient when not needed, low code and data size overhead and broad
applicability.

The newest version of this document can be found at
L<http://pod.tst.eu/http://cvs.schmorp.de/Coro-Multicore/perlmulticore.h>.

The nwest version of the header fgile itself, which
includes this documentation, can be downloaded from
L<http://cvs.schmorp.de/Coro-Multicore/perlmulticore.h>.

=head1 HOW DO I USE THIS IN MY MODULES?

The usage is very simple - you include this header file in your XS module. Then, before you
do your lengthy operation, you release the perl interpreter:

   perlinterp_release ();

And when you are done with your computation, you acquire it again:

   perlinterp_acquire ();

And that's it. This doesn't load any modules and consists of only a few
machine instructions when no module to take advantage of it is loaded.

Here is a simple example, an C<flock> wrapper implemented in XS. Unlike
perl's built-in C<flock>, it allows other threads (for example, those
provided by L<Coro>) to execute, instead of blocking the whole perl
interpreter. For the sake of this example, it requires a file descriptor
instead of a handle.

   #include "perlmulticore.h" // this header file

   // and in the XS portion
   int flock (int fd, int operation)
           CODE:
           perlinterp_release ();
           RETVAL = flock (fd, operation);
           perlinterp_acquire ();
           OUTPUT:
           RETVAL

Another example would be to modify L<DBD::mysql> to allow other
threads to execute while executing SQL queries. One way to do this
is find all C<mysql_st_internal_execute> and similar calls (such as
C<mysql_st_internal_execute41>), and adorn them with release/acquire
calls:

   {
     perlinterp_release ();
     imp_sth->row_num= mysql_st_internal_execute(sth, ...);
     perlinterp_acquire ();
   }

=head2 HOW ABOUT NOT-SO LONG WORK?

Sometimes you don't know how long your code will take - in a compression
library for example, compressing a few hundred Kilobyte of data can take
a while, while 50 Bytes will compress so fast that even attempting to do
something else could be more costly than just doing it.

This is a very hard problem to solve. The best you can do at the moment is
to release the perl interpreter only when you think the work to be done
justifies the expense.

As a rule of thumb, if you expect to need more than a few thousand cycles,
you should release the interpreter, else you shouldn't. When in doubt,
release.

For example, in a compression library, you might want to do this:

   if (bytes_to_be_compressed > 2000) perlinterp_release ();
   do_compress (...);
   if (bytes_to_be_compressed > 2000) perlinterp_acquire ();

Make sure the if conditions are exactly the same and don't change, so you
always call acquire when you release, and vice versa.

When you don't have a handy indicator, you might still do something
useful. For example, if you do some file locking with C<fcntl> and you
expect the lock to be available immediately in most cases, you could try
with C<F_SETLK> (which doesn't wait), and only release/wait/acquire when
the lock couldn't be set:

   int res = fcntl (fd, F_SETLK, &flock);

   if (res)
     {
       // error, assume lock is held by another process and do it the slow way
       perlinterp_release ();
       res = fcntl (fd, F_SETLKW, &flock);
       perlinterp_release ();
     }

=head1 THE HARD AND FAST RULES

As with everything, there are a number of rules to follow.

=over 4

=item I<Never> touch any perl data structures after calling C<perlinterp_release>.

Possibly the most important rule of them all, anything perl is
completely off-limits after C<perlinterp_release>, until you call
C<perlinterp_acquire>, after which you can access perl stuff again.

That includes anything in the perl interpreter that you didn't prove to be
safe, and didn't prove to be safe in older and future versions of perl:
global variables, local perl scalars, even if you are sure nobody accesses
them and you only try to "read" their value, and so on.

If you need to access perl things, do it before releasing the
interpreter with C<perlinterp_release>, or after acquiring it again with
C<perlinterp_acquire>.

=item I<Always> call C<perlinterp_release> and C<perlinterp_acquire> in pairs.

For each C<perlinterp_release> call there must be a C<perlinterp_acquire>
call. They don't have to be in the same function, and you can have
multiple calls to them, as long as every C<perlinterp_release> call is
followed by exactly one C<perlinterp_acquire> call.

For example., this would be fine:

   perlinterp_release ();

   if (!function_that_fails_with_0_return_value ())
     {
       perlinterp_acquire ();
       croak ("error");
       // croak doesn't return
     }

   perlinterp_acquire ();
   // do other stuff

=item I<Never> nest calls to C<perlinterp_release> and C<perlinterp_acquire>.

That simply means that after calling C<perlinterp_release>, you must
call C<perlinterp_acquire> before calling C<perlinterp_release>
again. Likewise, after C<perlinterp_acquire>, you can call
C<perlinterp_release> but not another C<perlinterp_acquire>.

=item I<Always> call C<perlinterp_release> first.

Also simple: you I<must not> call C<perlinterp_acquire> without having
called C<perlinterp_release> before.

=item I<Never> underestimate threads.

While it's easy to add parallel execution ability to your XS module, it
doesn't mean it is safe. After you release the perl interpreter, it's
perfectly possible that it will call your XS function in another thread,
even while your original function still executes. In other words: your C
code must be thread safe, and if you use any library, that library must be
thread-safe, too.

Always assume that the code between C<perlinterp_release> and
C<perlinterp_acquire> is executed in parallel on multiple CPUs at the same
time. If your code can't cope with that, you could consider using a mutex
to only allow one such execution, which is still better than blocking
everybody else from doing anything:

   static pthread_mutex_t my_mutex = PTHREAD_MUTEX_INITIALIZER;

   perlinterp_release ();
   pthread_mutex_lock (&my_mutex);
   do_your_non_thread_safe_thing ();
   pthread_mutex_unlock (&my_mutex);
   perlinterp_acquire ();

This isn't as trivial as it looks though, as you need to find out which
threading system is in use (with L<Coro::Multicore>, it currently is
always pthreads).

=item I<Don't> get confused by having to release first.

In many real world scenarios, you acquire a resource, do something, then
release it again. Don't let this confuse you, with this, you already own
the resource (the perl interpreter) so you have to I<release> first, and
I<acquire> it again later, not the other way around.

=back


=head1 DESIGN PRINCIPLES

This section discusses how the design goals were reached (you be the
judge), how it is implemented, and what overheads this implies.

=over 4

=item Simple to Use

All you have to do is identify the place in your existing code where you
stop touching perl stuff, do your actual work, and start touching perl
stuff again.

Then slap C<perlinterp_release ()> and C<perlinterp_acquire ()> around the
actual work code.

You have to include F<perlmulticore.h> and distribute it with your XS
code, but all these things border on the trivial.

=item Very Efficient

The definition for C<perlinterp_release> and C<perlinterp_release> is very
short:

   #define perlinterp_release() perl_multicore_api->pmapi_release ()
   #define perlinterp_acquire() perl_multicore_api->pmapi_acquire ()

Both are macros that read a pointer from memory (perl_multicore_api),
dereference a function pointer stored at that place, and call the
function, which takes no arguments and returns nothing.

The first call to C<perlinterp_release> will check for the presence
of any supporting module, and if none is loaded, will create a dummy
implementation where both C<pmapi_release> and C<pmapi_acquire> execute
this function:

  static void perl_multicore_nop (void) { }

So in the case of no magical module being loaded, all calls except the
first are two memory accesses and a predictable function call of an empty
function.

Of course, the overhead is much higher when these functions actually
implement anything useful, but you always get what you pay for.

With L<Coro::Multicore>, every release/acquire involves two pthread
switches, two coro thread switches, a bunch of syscalls, and sometimes
interacting with the event loop.

A dedicated thread pool such as the one L<IO::AIO> uses could reduce
these overheads, and would also reduce the dependencies (L<AnyEvent> is a
smaller and more portable dependency than L<Coro>), but it would require a
lot more work on the side of the module author wanting to support it than
this solution.

=item Low Code and Data Size Overhead

On a 64 bit system, F<perlmulticore.h> uses exactly C<8> octets (one
pointer) of your data segment, to store the C<perl_multicore_api>
pointer. In addition it creates a C<16> octet perl string to store the
function pointers in, and stores it in a hash provided by perl for this
purpose.

This is pretty much the equivalent of executing this code:

   $existing_hash{perl_multicore_api} = "123456781234567812345678";

And that's it, which is, as I think, indeed very little.

As for code size, on my amd64 system, every call to C<perlinterp_release>
or C<perlinterp_acquire> results in a variation of the following 9-10
octet sequence:

   150>   mov    0x200f23(%rip),%rax  # <perl_multicore_api>
   157>   callq  *0x8(%rax)

The biggest part if the initialisation code, which consists of 11 lines of
typical XS code. On my system, all the code in F<perlmulticore.h> compiles
to less than 160 octets of read-only data.

=item Broad Applicability

While there are alternative ways to achieve the goal of parallel execution
with threads that might be more efficient, this mechanism was chosen
because it is very simple to retrofit existing modules with it, and it

The design goals for this mechanism were to be simple to use, very
efficient when not needed, low code and data size overhead and broad
applicability.

=back

=head1 AUTHOR

   Marc A. Lehmann <perlmulticore@schmorp.de>

=head1 LICENSE

The F<perlmulticore.h> is put into the public domain. Where this is legally
not possible, or at your option, it can be licensed under creativecommons
CC0 license: L<https://creativecommons.org/publicdomain/zero/1.0/>.

=cut
*/

struct perl_multicore_api
{
  void (*pmapi_release)(void);
  void (*pmapi_acquire)(void);
};

static void perl_multicore_init (void);

const struct perl_multicore_api perl_multicore_api_init = { perl_multicore_init, abort };

static struct perl_multicore_api *perl_multicore_api
   = (struct perl_multicore_api *)&perl_multicore_api_init;

#define perlinterp_release() perl_multicore_api->pmapi_release ()
#define perlinterp_acquire() perl_multicore_api->pmapi_acquire ()

static void
perl_multicore_nop (void)
{
}

static void
perl_multicore_init (void)
{
  dTHX;

  /* check for existing API struct in PL_modglobal */
  SV **api_svp = hv_fetch (PL_modglobal, "perl_multicore_api", sizeof ("perl_multicore_api") - 1, 1);

  if (SvPOKp (*api_svp))
    perl_multicore_api = (struct perl_multicore_api *)SvPVX (*api_svp); /* we have one, use the existing one */
  else
    {
      /* create a new one with a dummy nop implementation */
      SV *api_sv = NEWSV (0, sizeof (*perl_multicore_api));
      SvCUR_set (api_sv, sizeof (*perl_multicore_api));
      SvPOK_only (api_sv);
      perl_multicore_api = (struct perl_multicore_api *)SvPVX (api_sv);
      perl_multicore_api->pmapi_release =
      perl_multicore_api->pmapi_acquire = perl_multicore_nop;
      *api_svp = api_sv;
    }

  /* call the real (or dummy) implementation now */
  perlinterp_release ();
}

#endif
Revision:	1.1
Committed:	Sat Jun 27 19:53:44 2015 UTC (8 years, 10 months ago) by root
Content type:	text/plain
Branch:	MAIN
Log Message:	* empty log message *
#	Content
1	/*
2	* Author: Marc A. Lehmann <xsthreadpool@schmorp.de>
3	* License: public domain, or where this is not possible/at your option,
4	* CC0 (https://creativecommons.org/publicdomain/zero/1.0/)
5	*/
6
7	#ifndef PERL_MULTICORE_H
8	#define PERL_MULTICORE_H
9
10	/*
11	=head1 NAME
12
13	perlmulticore.h - release the perl interpreter for other uses while doing hard work
14
15	=head1 SYNOPSIS
16
17	#include "perlmultiore.h"
18
19	// in your XS function:
20
21	perlinterp_release ();
22	do_the_C_thing ();
23	perlinterp_acquire ();
24
25	=head1 DESCRIPTION
26
27	This header file implements a simple mechanism for XS modules to allow
28	re-use of the perl interpreter for other threads while doing some lengthy
29	operation, such as cryptography, SQL queries, disk I/O and so on.
30
31	The design goals for this mechanism were to be simple to use, very
32	efficient when not needed, low code and data size overhead and broad
33	applicability.
34
35	The newest version of this document can be found at
36	L<http://pod.tst.eu/http://cvs.schmorp.de/Coro-Multicore/perlmulticore.h>.
37
38	The nwest version of the header fgile itself, which
39	includes this documentation, can be downloaded from
40	L<http://cvs.schmorp.de/Coro-Multicore/perlmulticore.h>.
41
42	=head1 HOW DO I USE THIS IN MY MODULES?
43
44	The usage is very simple - you include this header file in your XS module. Then, before you
45	do your lengthy operation, you release the perl interpreter:
46
47	perlinterp_release ();
48
49	And when you are done with your computation, you acquire it again:
50
51	perlinterp_acquire ();
52
53	And that's it. This doesn't load any modules and consists of only a few
54	machine instructions when no module to take advantage of it is loaded.
55
56	Here is a simple example, an C<flock> wrapper implemented in XS. Unlike
57	perl's built-in C<flock>, it allows other threads (for example, those
58	provided by L<Coro>) to execute, instead of blocking the whole perl
59	interpreter. For the sake of this example, it requires a file descriptor
60	instead of a handle.
61
62	#include "perlmulticore.h" // this header file
63
64	// and in the XS portion
65	int flock (int fd, int operation)
66	CODE:
67	perlinterp_release ();
68	RETVAL = flock (fd, operation);
69	perlinterp_acquire ();
70	OUTPUT:
71	RETVAL
72
73	Another example would be to modify L<DBD::mysql> to allow other
74	threads to execute while executing SQL queries. One way to do this
75	is find all C<mysql_st_internal_execute> and similar calls (such as
76	C<mysql_st_internal_execute41>), and adorn them with release/acquire
77	calls:
78
79	{
80	perlinterp_release ();
81	imp_sth->row_num= mysql_st_internal_execute(sth, ...);
82	perlinterp_acquire ();
83	}
84
85	=head2 HOW ABOUT NOT-SO LONG WORK?
86
87	Sometimes you don't know how long your code will take - in a compression
88	library for example, compressing a few hundred Kilobyte of data can take
89	a while, while 50 Bytes will compress so fast that even attempting to do
90	something else could be more costly than just doing it.
91
92	This is a very hard problem to solve. The best you can do at the moment is
93	to release the perl interpreter only when you think the work to be done
94	justifies the expense.
95
96	As a rule of thumb, if you expect to need more than a few thousand cycles,
97	you should release the interpreter, else you shouldn't. When in doubt,
98	release.
99
100	For example, in a compression library, you might want to do this:
101
102	if (bytes_to_be_compressed > 2000) perlinterp_release ();
103	do_compress (...);
104	if (bytes_to_be_compressed > 2000) perlinterp_acquire ();
105
106	Make sure the if conditions are exactly the same and don't change, so you
107	always call acquire when you release, and vice versa.
108
109	When you don't have a handy indicator, you might still do something
110	useful. For example, if you do some file locking with C<fcntl> and you
111	expect the lock to be available immediately in most cases, you could try
112	with C<F_SETLK> (which doesn't wait), and only release/wait/acquire when
113	the lock couldn't be set:
114
115	int res = fcntl (fd, F_SETLK, &flock);
116
117	if (res)
118	{
119	// error, assume lock is held by another process and do it the slow way
120	perlinterp_release ();
121	res = fcntl (fd, F_SETLKW, &flock);
122	perlinterp_release ();
123	}
124
125	=head1 THE HARD AND FAST RULES
126
127	As with everything, there are a number of rules to follow.
128
129	=over 4
130
131	=item I<Never> touch any perl data structures after calling C<perlinterp_release>.
132
133	Possibly the most important rule of them all, anything perl is
134	completely off-limits after C<perlinterp_release>, until you call
135	C<perlinterp_acquire>, after which you can access perl stuff again.
136
137	That includes anything in the perl interpreter that you didn't prove to be
138	safe, and didn't prove to be safe in older and future versions of perl:
139	global variables, local perl scalars, even if you are sure nobody accesses
140	them and you only try to "read" their value, and so on.
141
142	If you need to access perl things, do it before releasing the
143	interpreter with C<perlinterp_release>, or after acquiring it again with
144	C<perlinterp_acquire>.
145
146	=item I<Always> call C<perlinterp_release> and C<perlinterp_acquire> in pairs.
147
148	For each C<perlinterp_release> call there must be a C<perlinterp_acquire>
149	call. They don't have to be in the same function, and you can have
150	multiple calls to them, as long as every C<perlinterp_release> call is
151	followed by exactly one C<perlinterp_acquire> call.
152
153	For example., this would be fine:
154
155	perlinterp_release ();
156
157	if (!function_that_fails_with_0_return_value ())
158	{
159	perlinterp_acquire ();
160	croak ("error");
161	// croak doesn't return
162	}
163
164	perlinterp_acquire ();
165	// do other stuff
166
167	=item I<Never> nest calls to C<perlinterp_release> and C<perlinterp_acquire>.
168
169	That simply means that after calling C<perlinterp_release>, you must
170	call C<perlinterp_acquire> before calling C<perlinterp_release>
171	again. Likewise, after C<perlinterp_acquire>, you can call
172	C<perlinterp_release> but not another C<perlinterp_acquire>.
173
174	=item I<Always> call C<perlinterp_release> first.
175
176	Also simple: you I<must not> call C<perlinterp_acquire> without having
177	called C<perlinterp_release> before.
178
179	=item I<Never> underestimate threads.
180
181	While it's easy to add parallel execution ability to your XS module, it
182	doesn't mean it is safe. After you release the perl interpreter, it's
183	perfectly possible that it will call your XS function in another thread,
184	even while your original function still executes. In other words: your C
185	code must be thread safe, and if you use any library, that library must be
186	thread-safe, too.
187
188	Always assume that the code between C<perlinterp_release> and
189	C<perlinterp_acquire> is executed in parallel on multiple CPUs at the same
190	time. If your code can't cope with that, you could consider using a mutex
191	to only allow one such execution, which is still better than blocking
192	everybody else from doing anything:
193
194	static pthread_mutex_t my_mutex = PTHREAD_MUTEX_INITIALIZER;
195
196	perlinterp_release ();
197	pthread_mutex_lock (&my_mutex);
198	do_your_non_thread_safe_thing ();
199	pthread_mutex_unlock (&my_mutex);
200	perlinterp_acquire ();
201
202	This isn't as trivial as it looks though, as you need to find out which
203	threading system is in use (with L<Coro::Multicore>, it currently is
204	always pthreads).
205
206	=item I<Don't> get confused by having to release first.
207
208	In many real world scenarios, you acquire a resource, do something, then
209	release it again. Don't let this confuse you, with this, you already own
210	the resource (the perl interpreter) so you have to I<release> first, and
211	I<acquire> it again later, not the other way around.
212
213	=back
214
215
216	=head1 DESIGN PRINCIPLES
217
218	This section discusses how the design goals were reached (you be the
219	judge), how it is implemented, and what overheads this implies.
220
221	=over 4
222
223	=item Simple to Use
224
225	All you have to do is identify the place in your existing code where you
226	stop touching perl stuff, do your actual work, and start touching perl
227	stuff again.
228
229	Then slap C<perlinterp_release ()> and C<perlinterp_acquire ()> around the
230	actual work code.
231
232	You have to include F<perlmulticore.h> and distribute it with your XS
233	code, but all these things border on the trivial.
234
235	=item Very Efficient
236
237	The definition for C<perlinterp_release> and C<perlinterp_release> is very
238	short:
239
240	#define perlinterp_release() perl_multicore_api->pmapi_release ()
241	#define perlinterp_acquire() perl_multicore_api->pmapi_acquire ()
242
243	Both are macros that read a pointer from memory (perl_multicore_api),
244	dereference a function pointer stored at that place, and call the
245	function, which takes no arguments and returns nothing.
246
247	The first call to C<perlinterp_release> will check for the presence
248	of any supporting module, and if none is loaded, will create a dummy
249	implementation where both C<pmapi_release> and C<pmapi_acquire> execute
250	this function:
251
252	static void perl_multicore_nop (void) { }
253
254	So in the case of no magical module being loaded, all calls except the
255	first are two memory accesses and a predictable function call of an empty
256	function.
257
258	Of course, the overhead is much higher when these functions actually
259	implement anything useful, but you always get what you pay for.
260
261	With L<Coro::Multicore>, every release/acquire involves two pthread
262	switches, two coro thread switches, a bunch of syscalls, and sometimes
263	interacting with the event loop.
264
265	A dedicated thread pool such as the one L<IO::AIO> uses could reduce
266	these overheads, and would also reduce the dependencies (L<AnyEvent> is a
267	smaller and more portable dependency than L<Coro>), but it would require a
268	lot more work on the side of the module author wanting to support it than
269	this solution.
270
271	=item Low Code and Data Size Overhead
272
273	On a 64 bit system, F<perlmulticore.h> uses exactly C<8> octets (one
274	pointer) of your data segment, to store the C<perl_multicore_api>
275	pointer. In addition it creates a C<16> octet perl string to store the
276	function pointers in, and stores it in a hash provided by perl for this
277	purpose.
278
279	This is pretty much the equivalent of executing this code:
280
281	$existing_hash{perl_multicore_api} = "123456781234567812345678";
282
283	And that's it, which is, as I think, indeed very little.
284
285	As for code size, on my amd64 system, every call to C<perlinterp_release>
286	or C<perlinterp_acquire> results in a variation of the following 9-10
287	octet sequence:
288
289	150> mov 0x200f23(%rip),%rax # <perl_multicore_api>
290	157> callq *0x8(%rax)
291
292	The biggest part if the initialisation code, which consists of 11 lines of
293	typical XS code. On my system, all the code in F<perlmulticore.h> compiles
294	to less than 160 octets of read-only data.
295
296	=item Broad Applicability
297
298	While there are alternative ways to achieve the goal of parallel execution
299	with threads that might be more efficient, this mechanism was chosen
300	because it is very simple to retrofit existing modules with it, and it
301
302	The design goals for this mechanism were to be simple to use, very
303	efficient when not needed, low code and data size overhead and broad
304	applicability.
305
306	=back
307
308	=head1 AUTHOR
309
310	Marc A. Lehmann <perlmulticore@schmorp.de>
311
312	=head1 LICENSE
313
314	The F<perlmulticore.h> is put into the public domain. Where this is legally
315	not possible, or at your option, it can be licensed under creativecommons
316	CC0 license: L<https://creativecommons.org/publicdomain/zero/1.0/>.
317
318	=cut
319	*/
320
321	struct perl_multicore_api
322	{
323	void (*pmapi_release)(void);
324	void (*pmapi_acquire)(void);
325	};
326
327	static void perl_multicore_init (void);
328
329	const struct perl_multicore_api perl_multicore_api_init = { perl_multicore_init, abort };
330
331	static struct perl_multicore_api *perl_multicore_api
332	= (struct perl_multicore_api *)&perl_multicore_api_init;
333
334	#define perlinterp_release() perl_multicore_api->pmapi_release ()
335	#define perlinterp_acquire() perl_multicore_api->pmapi_acquire ()
336
337	static void
338	perl_multicore_nop (void)
339	{
340	}
341
342	static void
343	perl_multicore_init (void)
344	{
345	dTHX;
346
347	/* check for existing API struct in PL_modglobal */
348	SV **api_svp = hv_fetch (PL_modglobal, "perl_multicore_api", sizeof ("perl_multicore_api") - 1, 1);
349
350	if (SvPOKp (*api_svp))
351	perl_multicore_api = (struct perl_multicore_api )SvPVX (api_svp); /* we have one, use the existing one */
352	else
353	{
354	/* create a new one with a dummy nop implementation */
355	SV api_sv = NEWSV (0, sizeof (perl_multicore_api));
356	SvCUR_set (api_sv, sizeof (*perl_multicore_api));
357	SvPOK_only (api_sv);
358	perl_multicore_api = (struct perl_multicore_api *)SvPVX (api_sv);
359	perl_multicore_api->pmapi_release =
360	perl_multicore_api->pmapi_acquire = perl_multicore_nop;
361	*api_svp = api_sv;
362	}
363
364	/* call the real (or dummy) implementation now */
365	perlinterp_release ();
366	}
367
368	#endif