summaryrefslogtreecommitdiff
path: root/src/pipe.cpp
blob: 51ecedc3553617df5d2dc925183c944a346a90ba (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
/*
    Copyright (c) 2009-2012 250bpm s.r.o.
    Copyright (c) 2007-2009 iMatix Corporation
    Copyright (c) 2011 VMware, Inc.
    Copyright (c) 2007-2011 Other contributors as noted in the AUTHORS file

    This file is part of Crossroads I/O project.

    Crossroads I/O is free software; you can redistribute it and/or modify it
    under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    Crossroads is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <new>
#include <stddef.h>

#include "pipe.hpp"
#include "err.hpp"

int xs::pipepair (class object_t *parents_ [2], class pipe_t* pipes_ [2],
    int hwms_ [2], bool delays_ [2], int protocol_)
{
    //   Creates two pipe objects. These objects are connected by two ypipes,
    //   each to pass messages in one direction.

    pipe_t::upipe_t *upipe1 = new (std::nothrow) pipe_t::upipe_t ();
    alloc_assert (upipe1);
    pipe_t::upipe_t *upipe2 = new (std::nothrow) pipe_t::upipe_t ();
    alloc_assert (upipe2);

    pipes_ [0] = new (std::nothrow) pipe_t (parents_ [0], upipe1, upipe2,
        hwms_ [1], hwms_ [0], delays_ [0], protocol_);
    alloc_assert (pipes_ [0]);
    pipes_ [1] = new (std::nothrow) pipe_t (parents_ [1], upipe2, upipe1,
        hwms_ [0], hwms_ [1], delays_ [1], protocol_);
    alloc_assert (pipes_ [1]);

    pipes_ [0]->set_peer (pipes_ [1]);
    pipes_ [1]->set_peer (pipes_ [0]);

    return 0;
}

xs::pipe_t::pipe_t (object_t *parent_, upipe_t *inpipe_, upipe_t *outpipe_,
      int inhwm_, int outhwm_, bool delay_, int protocol_) :
    object_t (parent_),
    inpipe (inpipe_),
    outpipe (outpipe_),
    in_active (true),
    out_active (true),
    hwm (outhwm_),
    lwm (compute_lwm (inhwm_)),
    msgs_read (0),
    msgs_written (0),
    peers_msgs_read (0),
    peer (NULL),
    sink (NULL),
    state (active),
    delay (delay_),
    protocol (protocol_)
{
}

xs::pipe_t::~pipe_t ()
{
}

void xs::pipe_t::set_peer (pipe_t *peer_)
{
    //  Peer can be set once only.
    xs_assert (!peer);
    peer = peer_;
}

void xs::pipe_t::set_event_sink (i_pipe_events *sink_)
{
    // Sink can be set once only.
    xs_assert (!sink);
    sink = sink_;
}

void xs::pipe_t::set_identity (const blob_t &identity_)
{
    identity = identity_;
}

xs::blob_t xs::pipe_t::get_identity ()
{
    return identity;
}

bool xs::pipe_t::check_read ()
{
    if (unlikely (!in_active || (state != active && state != pending)))
        return false;

    //  Check if there's an item in the pipe.
    if (!inpipe->check_read ()) {
        in_active = false;
        return false;
    }

    //  If the next item in the pipe is message delimiter,
    //  initiate termination process.
    if (inpipe->probe (is_delimiter)) {
        msg_t msg;
        bool ok = inpipe->read (&msg);
        xs_assert (ok);
        delimit ();
        return false;
    }

    return true;
}

bool xs::pipe_t::read (msg_t *msg_)
{
    if (unlikely (!in_active || (state != active && state != pending)))
        return false;

    if (!inpipe->read (msg_)) {
        in_active = false;
        return false;
    }

    //  If delimiter was read, start termination process of the pipe.
    if (msg_->is_delimiter ()) {
        delimit ();
        return false;
    }

    if (!(msg_->flags () & msg_t::more))
        msgs_read++;

    if (lwm > 0 && msgs_read % lwm == 0)
        send_activate_write (peer, msgs_read);

    return true;
}

bool xs::pipe_t::check_write (msg_t *msg_)
{
    if (unlikely (!out_active || state != active))
        return false;

    bool full = hwm > 0 && msgs_written - peers_msgs_read == uint64_t (hwm);

    if (unlikely (full)) {
        out_active = false;
        return false;
    }

    return true;
}

bool xs::pipe_t::write (msg_t *msg_)
{
    if (unlikely (!check_write (msg_)))
        return false;

    bool more = msg_->flags () & msg_t::more ? true : false;
    outpipe->write (*msg_, more);
    if (!more)
        msgs_written++;

    return true;
}

void xs::pipe_t::rollback ()
{
    //  Remove incomplete message from the outbound pipe.
    msg_t msg;
    if (outpipe) {
		while (outpipe->unwrite (&msg)) {
		    xs_assert (msg.flags () & msg_t::more);
		    int rc = msg.close ();
		    errno_assert (rc == 0);
		}
    }
}

void xs::pipe_t::flush ()
{
    //  If terminate() was already called do nothing.
    if (state == terminated && state == double_terminated)
        return;

    //  The peer does not exist anymore at this point.
    if (state == terminating)
        return;

    if (outpipe && !outpipe->flush ())
        send_activate_read (peer);
}

void xs::pipe_t::process_activate_read ()
{
    if (!in_active && (state == active || state == pending)) {
        in_active = true;
        sink->read_activated (this);
    }
}

void xs::pipe_t::process_activate_write (uint64_t msgs_read_)
{
    //  Remember the peers's message sequence number.
    peers_msgs_read = msgs_read_;

    if (!out_active && state == active) {
        out_active = true;
        sink->write_activated (this);
    }
}

void xs::pipe_t::process_hiccup (void *pipe_)
{
    //  Destroy old outpipe. Note that the read end of the pipe was already
    //  migrated to this thread.
    xs_assert (outpipe);
    outpipe->flush ();
    msg_t msg;
    while (outpipe->read (&msg)) {
       int rc = msg.close ();
       errno_assert (rc == 0);
    }
    delete outpipe;

    //  Plug in the new outpipe.
    xs_assert (pipe_);
    outpipe = (upipe_t*) pipe_;
    out_active = true;

    //  If appropriate, notify the user about the hiccup.
    if (state == active)
        sink->hiccuped (this);
}

void xs::pipe_t::process_pipe_term ()
{
    //  This is the simple case of peer-induced termination. If there are no
    //  more pending messages to read, or if the pipe was configured to drop
    //  pending messages, we can move directly to the terminating state.
    //  Otherwise we'll hang up in pending state till all the pending messages
    //  are sent.
    if (state == active) {
        if (!delay) {
            state = terminating;
            outpipe = NULL;
            send_pipe_term_ack (peer);
            return;
        }
        else {
            state = pending;
            return;
        }
    }

    //  Delimiter happened to arrive before the term command. Now we have the
    //  term command as well, so we can move straight to terminating state.
    if (state == delimited) {
        state = terminating;
        outpipe = NULL;
        send_pipe_term_ack (peer);
        return;
    }

    //  This is the case where both ends of the pipe are closed in parallel.
    //  We simply reply to the request by ack and continue waiting for our
    //  own ack.
    if (state == terminated) {
        state = double_terminated;
        outpipe = NULL;
        send_pipe_term_ack (peer);
        return;
    }

    //  pipe_term is invalid in other states.
    xs_assert (false);
}

void xs::pipe_t::process_pipe_term_ack ()
{
    //  Notify the user that all the references to the pipe should be dropped.
    xs_assert (sink);
    sink->terminated (this);

    //  In terminating and double_terminated states there's nothing to do.
    //  Simply deallocate the pipe. In terminated state we have to ack the
    //  peer before deallocating this side of the pipe. All the other states
    //  are invalid.
    if (state == terminating) ;
    else if (state == double_terminated);
    else if (state == terminated) {
        outpipe = NULL;
        send_pipe_term_ack (peer);
    }
    else
        xs_assert (false);

    //  We'll deallocate the inbound pipe, the peer will deallocate the outbound
    //  pipe (which is an inbound pipe from its point of view).
    //  First, delete all the unread messages in the pipe. We have to do it by
    //  hand because msg_t doesn't have automatic destructor. Then deallocate
    //  the ypipe itself.
    msg_t msg;
    while (inpipe->read (&msg)) {
       int rc = msg.close ();
       errno_assert (rc == 0);
    }
    delete inpipe;

    //  Deallocate the pipe object
    delete this;
}

void xs::pipe_t::terminate (bool delay_)
{
    //  Overload the value specified at pipe creation.
    delay = delay_;

    //  If terminate was already called, we can ignore the duplicit invocation.
    if (state == terminated || state == double_terminated)
        return;

    //  If the pipe is in the final phase of async termination, it's going to
    //  closed anyway. No need to do anything special here.
    else if (state == terminating)
        return;

    //  The simple sync termination case. Ask the peer to terminate and wait
    //  for the ack.
    else if (state == active) {
        send_pipe_term (peer);
        state = terminated;
    }

    //  There are still pending messages available, but the user calls
    //  'terminate'. We can act as if all the pending messages were read.
    else if (state == pending && !delay) {
            outpipe = NULL;
            send_pipe_term_ack (peer);
            state = terminating;
    }

    //  If there are pending messages still availabe, do nothing.
    else if (state == pending && delay) {
    }

    //  We've already got delimiter, but not term command yet. We can ignore
    //  the delimiter and ack synchronously terminate as if we were in
    //  active state.    
    else if (state == delimited) {
        send_pipe_term (peer);
        state = terminated;    
    }

    //  There are no other states.
    else
        xs_assert (false);

    //  Stop outbound flow of messages.
    out_active = false;

    if (outpipe) {

		//  Rollback any unfinished outbound messages.
		rollback ();

		//  Push delimiter into the outbound pipe. Note that watermarks are not
		//  checked thus the delimiter can be written even though the pipe
        //  is full.
		msg_t msg;
		msg.init_delimiter ();
		outpipe->write (msg, false);
		flush ();
    }
}

int xs::pipe_t::get_protocol ()
{
    return protocol;
}

bool xs::pipe_t::is_delimiter (msg_t &msg_)
{
    return msg_.is_delimiter ();
}

int xs::pipe_t::compute_lwm (int hwm_)
{
    //  Compute the low water mark. Following point should be taken
    //  into consideration:
    //
    //  1. LWM has to be less than HWM.
    //  2. LWM cannot be set to very low value (such as zero) as after filling
    //     the queue it would start to refill only after all the messages are
    //     read from it and thus unnecessarily hold the progress back.
    //  3. LWM cannot be set to very high value (such as HWM-1) as it would
    //     result in lock-step filling of the queue - if a single message is
    //     read from a full queue, writer thread is resumed to write exactly one
    //     message to the queue and go back to sleep immediately. This would
    //     result in low performance.
    //
    //  Given the 3. it would be good to keep HWM and LWM as far apart as
    //  possible to reduce the thread switching overhead to almost zero,
    //  say HWM-LWM should be max_wm_delta.
    //
    //  That done, we still we have to account for the cases where
    //  HWM < max_wm_delta thus driving LWM to negative numbers.
    //  Let's make LWM 1/2 of HWM in such cases.
    int result = (hwm_ > max_wm_delta * 2) ?
        hwm_ - max_wm_delta : (hwm_ + 1) / 2;

    return result;
}

void xs::pipe_t::delimit ()
{
    if (state == active) {
        state = delimited;
        return;
    }

    if (state == pending) {
        outpipe = NULL;
        send_pipe_term_ack (peer);
        state = terminating;
        return;
    }

    //  Delimiter in any other state is invalid.
    xs_assert (false);
}

void xs::pipe_t::hiccup ()
{
    //  If termination is already under way do nothing.
    if (state != active)
        return;

    //  We'll drop the pointer to the inpipe. From now on, the peer is
    //  responsible for deallocating it.
    inpipe = NULL;

    //  Create new inpipe.
    inpipe = new (std::nothrow) pipe_t::upipe_t ();
    alloc_assert (inpipe);
    in_active = true;

    //  Notify the peer about the hiccup.
    send_hiccup (peer, (void*) inpipe);
}