libev/ev_linuxaio.c

/*
 * libev linux aio fd activity backend
 *
 * Copyright (c) 2019 Marc Alexander Lehmann <libev@schmorp.de>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modifica-
 * tion, are permitted provided that the following conditions are met:
 *
 *   1.  Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *
 *   2.  Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License ("GPL") version 2 or any later version,
 * in which case the provisions of the GPL are applicable instead of
 * the above. If you wish to allow the use of your version of this file
 * only under the terms of the GPL and not to allow others to use your
 * version of this file under the BSD license, indicate your decision
 * by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL. If you do not delete the
 * provisions above, a recipient may use your version of this file under
 * either the BSD or the GPL.
 */

#include <sys/time.h> /* actually linux/time.h, but we must assume they are compatible */
#include <linux/aio_abi.h>

/* we try to fill 4kn pages exactly.
 * the ring buffer header is 32 bytes, every io event is 32 bytes.
 * the kernel takes the io event number, doubles it, adds 2, adds the ring buffer
 * so the calculation below will use "exactly" 8kB for the ring buffer
 */
#define EV_LINUXAIO_DEPTH (256 / 2 - 2 - 1) /* max. number of io events per batch */

/*****************************************************************************/
/* syscall wrapdadoop */

#include <sys/syscall.h> /* no glibc wrappers */

/* aio_abi.h is not verioned in any way, so we cannot test for its existance */
#define IOCB_CMD_POLL 5

/* taken from linux/fs/aio.c */
#define AIO_RING_MAGIC                  0xa10a10a1
#define AIO_RING_INCOMPAT_FEATURES      0
struct aio_ring
{
  unsigned id;    /* kernel internal index number */
  unsigned nr;    /* number of io_events */
  unsigned head;  /* Written to by userland or by kernel. */
  unsigned tail;

  unsigned magic;
  unsigned compat_features;
  unsigned incompat_features;
  unsigned header_length;  /* size of aio_ring */

  struct io_event io_events[0];
};

static int
ev_io_setup (unsigned nr_events, aio_context_t *ctx_idp)
{
  return syscall (SYS_io_setup, nr_events, ctx_idp);
}

static int
ev_io_destroy (aio_context_t ctx_id)
{
  return syscall (SYS_io_destroy, ctx_id);
}

static int
ev_io_submit (aio_context_t ctx_id, long nr, struct iocb *cbp[])
{
  return syscall (SYS_io_submit, ctx_id, nr, cbp);
}

static int
ev_io_cancel (aio_context_t ctx_id, struct iocb *cbp, struct io_event *result)
{
  return syscall (SYS_io_cancel, ctx_id, cbp, result);
}

static int
ev_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event *events, struct timespec *timeout)
{
  return syscall (SYS_io_getevents, ctx_id, min_nr, nr, events, timeout);
}

typedef void (*ev_io_cb) (long nr, struct io_event *events);

/*****************************************************************************/
/* actual backed implementation */

/* two iocbs for every fd, one for read, one for write */
typedef struct aniocb
{
  struct iocb io;
  /*int inuse;*/
} *ANIOCBP;

inline_size
void
linuxaio_array_needsize_iocbp (ANIOCBP *base, int count)
{
  /* TODO: quite the overhead to allocate every iocb separately */
  while (count--)
    {
      *base = (ANIOCBP)ev_malloc (sizeof (**base));
      memset (*base, 0, sizeof (**base));
      /* would be nice to initialize fd/data as well */
      (*base)->io.aio_lio_opcode = IOCB_CMD_POLL;
      ++base;
    }
}

static void
linuxaio_free_iocbp (EV_P)
{
  while (linuxaio_iocbpmax--)
    ev_free (linuxaio_iocbps [linuxaio_iocbpmax]);

  linuxaio_iocbpmax = 0;
}

static void
linuxaio_modify (EV_P_ int fd, int oev, int nev)
{
  /* TODO: full zero initialize required? */
  array_needsize (ANIOCBP, linuxaio_iocbps, linuxaio_iocbpmax, fd + 1, linuxaio_array_needsize_iocbp);
  struct aniocb *iocb = linuxaio_iocbps [fd];

  if (iocb->io.aio_buf)
    ev_io_cancel (linuxaio_ctx, &iocb->io, (void *)0);

  if (nev)
    {
      iocb->io.aio_data       = fd;
      iocb->io.aio_fildes     = fd;
      iocb->io.aio_buf        =
          (nev & EV_READ ? POLLIN : 0)
          | (nev & EV_WRITE ? POLLOUT : 0);

      /* queue iocb up for io_submit */
      /* this assumes we only ever get one call per fd per loop iteration */
      ++linuxaio_submitcnt;
      array_needsize (struct iocb *, linuxaio_submits, linuxaio_submitmax, linuxaio_submitcnt, array_needsize_noinit);
      linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io;
    }
}

static void
linuxaio_parse_events (EV_P_ struct io_event *ev, int nr)
{
  while (nr)
    {
      int fd  = ev->data;
      int res = ev->res;

      assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdxmax));

      /* linux aio is oneshot: rearm fd */
      linuxaio_iocbps [fd]->io.aio_buf = 0;
      anfds [fd].events = 0;
      fd_change (EV_A_ fd, 0);

      /* feed events, we do not expect or handle POLLNVAL */
      if (ecb_expect_false (res & POLLNVAL))
        fd_kill (EV_A_ fd);
      else
        fd_event (
          EV_A_
          fd,
          (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
          | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0)
        );

      --nr;
      ++ev;
    }
}

/* get any events from ringbuffer, return true if any were handled */
static int
linuxaio_get_events_from_ring (EV_P)
{
  struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx;

  ECB_MEMORY_FENCE_ACQUIRE;

  unsigned head = ring->head;
  unsigned tail = *(volatile unsigned *)&ring->tail;

  if (ring->magic != AIO_RING_MAGIC
      || ring->incompat_features != AIO_RING_INCOMPAT_FEATURES
      || ring->header_length != sizeof (struct aio_ring) /* TODO: or use it to find io_event[0]? */
      || head == tail)
    return 0;

  /* parse all available events, but only once, to avoid starvation */
  if (tail > head) /* normal case around */
    linuxaio_parse_events (EV_A_ ring->io_events + head, tail - head);
  else
    {
      /* wrapped around */
      linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head);
      linuxaio_parse_events (EV_A_ ring->io_events, tail);
    }

  ring->head = tail;

  return 1;
}

/* read at least one event from kernel, or timeout */
inline_size
void
linuxaio_get_events (EV_P_ ev_tstamp timeout)
{
  struct timespec ts;
  struct io_event ioev;
  int res;

  if (linuxaio_get_events_from_ring (EV_A))
    return;

  /* no events, so wait for at least one, then poll ring buffer again */
  /* this degraded to one event per loop iteration */
  /* if the ring buffer changes layout, but so be it */

  ts.tv_sec  = (long)timeout;
  ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9);

  res = ev_io_getevents (linuxaio_ctx, 1, 1, &ioev, &ts);

  if (res < 0)
    ev_syserr ("(libev) io_getevents");
  else if (res)
    {
      /* at least one event received, handle it and any remaining ones in the ring buffer */
      linuxaio_parse_events (EV_A_ &ioev, 1);
      linuxaio_get_events_from_ring (EV_A);
    }
}

static void
linuxaio_poll (EV_P_ ev_tstamp timeout)
{
  int submitted;

  /* first phase: submit new iocbs */

  /* io_submit might return less than the requested number of iocbs */
  /* this is, afaics, only because of errors, but we go by the book and use a loop, */
  /* which allows us to pinpoint the errornous iocb */
  for (submitted = 0; submitted < linuxaio_submitcnt; )
    {
      int res = ev_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted);

      if (res < 0)
        if (errno == EAGAIN)
          {
            /* This happens when the ring buffer is full, at least. I assume this means
             * that the event was queued synchronously during io_submit, and thus
             * the buffer overflowd.
             * In this case, we just try next loop iteration.
             */
            memcpy (linuxaio_submits, linuxaio_submits + submitted, (linuxaio_submitcnt - submitted) * sizeof (*linuxaio_submits));
            linuxaio_submitcnt -= submitted;
            timeout = 0;
            break;
          }
        else
          /* TODO: we get EAGAIN when the ring buffer is full for some reason */
          /* TODO: should we always just try next time? */
          ev_syserr ("(libev) io_submit");

      submitted += res;
    }

  linuxaio_submitcnt = 0;

  /* second phase: fetch and parse events */

  linuxaio_get_events (EV_A_ timeout);
}

inline_size
int
linuxaio_init (EV_P_ int flags)
{
  /* would be great to have a nice test for IOCB_CMD_POLL instead */
  if (ev_linux_version () < 0x041200) /* 4.18 introduced IOCB_CMD_POLL */
    return 0;

  if (ev_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0)
    return 0;

  backend_modify  = linuxaio_modify;
  backend_poll    = linuxaio_poll;

  linuxaio_iocbpmax = 0;
  linuxaio_iocbps = 0;

  linuxaio_submits = 0;
  linuxaio_submitmax = 0;
  linuxaio_submitcnt = 0;

  return EVBACKEND_LINUXAIO;
}

inline_size
void
linuxaio_destroy (EV_P)
{
  linuxaio_free_iocbp (EV_A);
  ev_io_destroy (linuxaio_ctx);
}

inline_size
void
linuxaio_fork (EV_P)
{
  abort ();//D
}

Revision:	1.1
Committed:	Thu Jun 20 22:44:59 2019 UTC (4 years, 10 months ago) by root
Content type:	text/plain
Branch:	MAIN
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	/*
2			* libev linux aio fd activity backend
3			*
4			* Copyright (c) 2019 Marc Alexander Lehmann <libev@schmorp.de>
5			* All rights reserved.
6			*
7			* Redistribution and use in source and binary forms, with or without modifica-
8			* tion, are permitted provided that the following conditions are met:
9			*
10			* 1. Redistributions of source code must retain the above copyright notice,
11			* this list of conditions and the following disclaimer.
12			*
13			* 2. Redistributions in binary form must reproduce the above copyright
14			* notice, this list of conditions and the following disclaimer in the
15			* documentation and/or other materials provided with the distribution.
16			*
17			* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
18			* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
19			* CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
20			* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
21			* CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
22			* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
23			* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24			* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
25			* ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
26			* OF THE POSSIBILITY OF SUCH DAMAGE.
27			*
28			* Alternatively, the contents of this file may be used under the terms of
29			* the GNU General Public License ("GPL") version 2 or any later version,
30			* in which case the provisions of the GPL are applicable instead of
31			* the above. If you wish to allow the use of your version of this file
32			* only under the terms of the GPL and not to allow others to use your
33			* version of this file under the BSD license, indicate your decision
34			* by deleting the provisions above and replace them with the notice
35			* and other provisions required by the GPL. If you do not delete the
36			* provisions above, a recipient may use your version of this file under
37			* either the BSD or the GPL.
38			*/
39
40			#include <sys/time.h> /* actually linux/time.h, but we must assume they are compatible */
41			#include <linux/aio_abi.h>
42
43			/* we try to fill 4kn pages exactly.
44			* the ring buffer header is 32 bytes, every io event is 32 bytes.
45			* the kernel takes the io event number, doubles it, adds 2, adds the ring buffer
46			* so the calculation below will use "exactly" 8kB for the ring buffer
47			*/
48			#define EV_LINUXAIO_DEPTH (256 / 2 - 2 - 1) /* max. number of io events per batch */
49
50			/*****************************************************************************/
51			/* syscall wrapdadoop */
52
53			#include <sys/syscall.h> /* no glibc wrappers */
54
55			/* aio_abi.h is not verioned in any way, so we cannot test for its existance */
56			#define IOCB_CMD_POLL 5
57
58			/* taken from linux/fs/aio.c */
59			#define AIO_RING_MAGIC 0xa10a10a1
60			#define AIO_RING_INCOMPAT_FEATURES 0
61			struct aio_ring
62			{
63			unsigned id; /* kernel internal index number */
64			unsigned nr; /* number of io_events */
65			unsigned head; /* Written to by userland or by kernel. */
66			unsigned tail;
67
68			unsigned magic;
69			unsigned compat_features;
70			unsigned incompat_features;
71			unsigned header_length; /* size of aio_ring */
72
73			struct io_event io_events[0];
74			};
75
76			static int
77			ev_io_setup (unsigned nr_events, aio_context_t *ctx_idp)
78			{
79			return syscall (SYS_io_setup, nr_events, ctx_idp);
80			}
81
82			static int
83			ev_io_destroy (aio_context_t ctx_id)
84			{
85			return syscall (SYS_io_destroy, ctx_id);
86			}
87
88			static int
89			ev_io_submit (aio_context_t ctx_id, long nr, struct iocb *cbp[])
90			{
91			return syscall (SYS_io_submit, ctx_id, nr, cbp);
92			}
93
94			static int
95			ev_io_cancel (aio_context_t ctx_id, struct iocb cbp, struct io_event result)
96			{
97			return syscall (SYS_io_cancel, ctx_id, cbp, result);
98			}
99
100			static int
101			ev_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event events, struct timespec timeout)
102			{
103			return syscall (SYS_io_getevents, ctx_id, min_nr, nr, events, timeout);
104			}
105
106			typedef void (ev_io_cb) (long nr, struct io_event events);
107
108			/*****************************************************************************/
109			/* actual backed implementation */
110
111			/* two iocbs for every fd, one for read, one for write */
112			typedef struct aniocb
113			{
114			struct iocb io;
115			/int inuse;/
116			} *ANIOCBP;
117
118			inline_size
119			void
120			linuxaio_array_needsize_iocbp (ANIOCBP *base, int count)
121			{
122			/* TODO: quite the overhead to allocate every iocb separately */
123			while (count--)
124			{
125			base = (ANIOCBP)ev_malloc (sizeof (*base));
126			memset (base, 0, sizeof (*base));
127			/* would be nice to initialize fd/data as well */
128			(*base)->io.aio_lio_opcode = IOCB_CMD_POLL;
129			++base;
130			}
131			}
132
133			static void
134			linuxaio_free_iocbp (EV_P)
135			{
136			while (linuxaio_iocbpmax--)
137			ev_free (linuxaio_iocbps [linuxaio_iocbpmax]);
138
139			linuxaio_iocbpmax = 0;
140			}
141
142			static void
143			linuxaio_modify (EV_P_ int fd, int oev, int nev)
144			{
145			/* TODO: full zero initialize required? */
146			array_needsize (ANIOCBP, linuxaio_iocbps, linuxaio_iocbpmax, fd + 1, linuxaio_array_needsize_iocbp);
147			struct aniocb *iocb = linuxaio_iocbps [fd];
148
149			if (iocb->io.aio_buf)
150			ev_io_cancel (linuxaio_ctx, &iocb->io, (void *)0);
151
152			if (nev)
153			{
154			iocb->io.aio_data = fd;
155			iocb->io.aio_fildes = fd;
156			iocb->io.aio_buf =
157			(nev & EV_READ ? POLLIN : 0)
158			\| (nev & EV_WRITE ? POLLOUT : 0);
159
160			/* queue iocb up for io_submit */
161			/* this assumes we only ever get one call per fd per loop iteration */
162			++linuxaio_submitcnt;
163			array_needsize (struct iocb *, linuxaio_submits, linuxaio_submitmax, linuxaio_submitcnt, array_needsize_noinit);
164			linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io;
165			}
166			}
167
168			static void
169			linuxaio_parse_events (EV_P_ struct io_event *ev, int nr)
170			{
171			while (nr)
172			{
173			int fd = ev->data;
174			int res = ev->res;
175
176			assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdxmax));
177
178			/* linux aio is oneshot: rearm fd */
179			linuxaio_iocbps [fd]->io.aio_buf = 0;
180			anfds [fd].events = 0;
181			fd_change (EV_A_ fd, 0);
182
183			/* feed events, we do not expect or handle POLLNVAL */
184			if (ecb_expect_false (res & POLLNVAL))
185			fd_kill (EV_A_ fd);
186			else
187			fd_event (
188			EV_A_
189			fd,
190			(res & (POLLOUT \| POLLERR \| POLLHUP) ? EV_WRITE : 0)
191			\| (res & (POLLIN \| POLLERR \| POLLHUP) ? EV_READ : 0)
192			);
193
194			--nr;
195			++ev;
196			}
197			}
198
199			/* get any events from ringbuffer, return true if any were handled */
200			static int
201			linuxaio_get_events_from_ring (EV_P)
202			{
203			struct aio_ring ring = (struct aio_ring )linuxaio_ctx;
204
205			ECB_MEMORY_FENCE_ACQUIRE;
206
207			unsigned head = ring->head;
208			unsigned tail = (volatile unsigned )&ring->tail;
209
210			if (ring->magic != AIO_RING_MAGIC
211			\|\| ring->incompat_features != AIO_RING_INCOMPAT_FEATURES
212			\|\| ring->header_length != sizeof (struct aio_ring) /* TODO: or use it to find io_event[0]? */
213			\|\| head == tail)
214			return 0;
215
216			/* parse all available events, but only once, to avoid starvation */
217			if (tail > head) /* normal case around */
218			linuxaio_parse_events (EV_A_ ring->io_events + head, tail - head);
219			else
220			{
221			/* wrapped around */
222			linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head);
223			linuxaio_parse_events (EV_A_ ring->io_events, tail);
224			}
225
226			ring->head = tail;
227
228			return 1;
229			}
230
231			/* read at least one event from kernel, or timeout */
232			inline_size
233			void
234			linuxaio_get_events (EV_P_ ev_tstamp timeout)
235			{
236			struct timespec ts;
237			struct io_event ioev;
238			int res;
239
240			if (linuxaio_get_events_from_ring (EV_A))
241			return;
242
243			/* no events, so wait for at least one, then poll ring buffer again */
244			/* this degraded to one event per loop iteration */
245			/* if the ring buffer changes layout, but so be it */
246
247			ts.tv_sec = (long)timeout;
248			ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9);
249
250			res = ev_io_getevents (linuxaio_ctx, 1, 1, &ioev, &ts);
251
252			if (res < 0)
253			ev_syserr ("(libev) io_getevents");
254			else if (res)
255			{
256			/* at least one event received, handle it and any remaining ones in the ring buffer */
257			linuxaio_parse_events (EV_A_ &ioev, 1);
258			linuxaio_get_events_from_ring (EV_A);
259			}
260			}
261
262			static void
263			linuxaio_poll (EV_P_ ev_tstamp timeout)
264			{
265			int submitted;
266
267			/* first phase: submit new iocbs */
268
269			/* io_submit might return less than the requested number of iocbs */
270			/* this is, afaics, only because of errors, but we go by the book and use a loop, */
271			/* which allows us to pinpoint the errornous iocb */
272			for (submitted = 0; submitted < linuxaio_submitcnt; )
273			{
274			int res = ev_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted);
275
276			if (res < 0)
277			if (errno == EAGAIN)
278			{
279			/* This happens when the ring buffer is full, at least. I assume this means
280			* that the event was queued synchronously during io_submit, and thus
281			* the buffer overflowd.
282			* In this case, we just try next loop iteration.
283			*/
284			memcpy (linuxaio_submits, linuxaio_submits + submitted, (linuxaio_submitcnt - submitted) * sizeof (*linuxaio_submits));
285			linuxaio_submitcnt -= submitted;
286			timeout = 0;
287			break;
288			}
289			else
290			/* TODO: we get EAGAIN when the ring buffer is full for some reason */
291			/* TODO: should we always just try next time? */
292			ev_syserr ("(libev) io_submit");
293
294			submitted += res;
295			}
296
297			linuxaio_submitcnt = 0;
298
299			/* second phase: fetch and parse events */
300
301			linuxaio_get_events (EV_A_ timeout);
302			}
303
304			inline_size
305			int
306			linuxaio_init (EV_P_ int flags)
307			{
308			/* would be great to have a nice test for IOCB_CMD_POLL instead */
309			if (ev_linux_version () < 0x041200) /* 4.18 introduced IOCB_CMD_POLL */
310			return 0;
311
312			if (ev_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0)
313			return 0;
314
315			backend_modify = linuxaio_modify;
316			backend_poll = linuxaio_poll;
317
318			linuxaio_iocbpmax = 0;
319			linuxaio_iocbps = 0;
320
321			linuxaio_submits = 0;
322			linuxaio_submitmax = 0;
323			linuxaio_submitcnt = 0;
324
325			return EVBACKEND_LINUXAIO;
326			}
327
328			inline_size
329			void
330			linuxaio_destroy (EV_P)
331			{
332			linuxaio_free_iocbp (EV_A);
333			ev_io_destroy (linuxaio_ctx);
334			}
335
336			inline_size
337			void
338			linuxaio_fork (EV_P)
339			{
340			abort ();//D
341			}
342