summaryrefslogtreecommitdiffstats
path: root/src/vpp-api/python/vpp_papi.py
blob: ece0e4ee52dcc2ef491452b84c18695199f97a67 (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
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
#!/usr/bin/env python
#
# Copyright (c) 2016 Cisco and/or its affiliates.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at:
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

from __future__ import print_function
import sys
import os
import logging
import collections
import struct
import json
import threading
import fnmatch
import weakref
import atexit
from cffi import FFI
import cffi

if sys.version[0] == '2':
    import Queue as queue
else:
    import queue as queue

ffi = FFI()
ffi.cdef("""
typedef void (*vac_callback_t)(unsigned char * data, int len);
typedef void (*vac_error_callback_t)(void *, unsigned char *, int);
int vac_connect(char * name, char * chroot_prefix, vac_callback_t cb,
    int rx_qlen);
int vac_disconnect(void);
int vac_read(char **data, int *l, unsigned short timeout);
int vac_write(char *data, int len);
void vac_free(void * msg);

int vac_get_msg_index(unsigned char * name);
int vac_msg_table_size(void);
int vac_msg_table_max_index(void);

void vac_rx_suspend (void);
void vac_rx_resume (void);
void vac_set_error_handler(vac_error_callback_t);
 """)

# Barfs on failure, no need to check success.
vpp_api = ffi.dlopen('libvppapiclient.so')


def vpp_atexit(vpp_weakref):
    """Clean up VPP connection on shutdown."""
    vpp_instance = vpp_weakref()
    if vpp_instance.connected:
        vpp_instance.logger.debug('Cleaning up VPP on exit')
        vpp_instance.disconnect()


vpp_object = None


def vpp_iterator(d):
    if sys.version[0] == '2':
        return d.iteritems()
    else:
        return d.items()


@ffi.callback("void(unsigned char *, int)")
def vac_callback_sync(data, len):
    vpp_object.msg_handler_sync(ffi.buffer(data, len))


@ffi.callback("void(unsigned char *, int)")
def vac_callback_async(data, len):
    vpp_object.msg_handler_async(ffi.buffer(data, len))


@ffi.callback("void(void *, unsigned char *, int)")
def vac_error_handler(arg, msg, msg_len):
    vpp_object.logger.warning("VPP API client:: %s", ffi.string(msg, msg_len))


class Empty(object):
    pass


class FuncWrapper(object):
    def __init__(self, func):
        self._func = func
        self.__name__ = func.__name__

    def __call__(self, **kwargs):
        return self._func(**kwargs)


class VPP():
    """VPP interface.

    This class provides the APIs to VPP.  The APIs are loaded
    from provided .api.json files and makes functions accordingly.
    These functions are documented in the VPP .api files, as they
    are dynamically created.

    Additionally, VPP can send callback messages; this class
    provides a means to register a callback function to receive
    these messages in a background thread.
    """
    def __init__(self, apifiles=None, testmode=False, async_thread=True,
                 logger=None, loglevel=None,
                 read_timeout=0):
        """Create a VPP API object.

        apifiles is a list of files containing API
        descriptions that will be loaded - methods will be
        dynamically created reflecting these APIs.  If not
        provided this will load the API files from VPP's
        default install location.

        logger, if supplied, is the logging logger object to log to.
        loglevel, if supplied, is the log level this logger is set
        to report at (from the loglevels in the logging module).
        """
        global vpp_object
        vpp_object = self

        if logger is None:
            logger = logging.getLogger(__name__)
            if loglevel is not None:
                logger.setLevel(loglevel)

        self.logger = logger

        self.messages = {}
        self.id_names = []
        self.id_msgdef = []
        self.connected = False
        self.header = struct.Struct('>HI')
        self.apifiles = []
        self.event_callback = None
        self.message_queue = queue.Queue()
        self.read_timeout = read_timeout
        self.vpp_api = vpp_api
        self.async_thread = async_thread

        if not apifiles:
            # Pick up API definitions from default directory
            try:
                apifiles = self.find_api_files()
            except RuntimeError:
                # In test mode we don't care that we can't find the API files
                if testmode:
                    apifiles = []
                else:
                    raise

        for file in apifiles:
            with open(file) as apidef_file:
                api = json.load(apidef_file)
                for t in api['types']:
                    self.add_type(t[0], t[1:])

                for m in api['messages']:
                    self.add_message(m[0], m[1:])
        self.apifiles = apifiles

        # Basic sanity check
        if len(self.messages) == 0 and not testmode:
            raise ValueError(1, 'Missing JSON message definitions')

        # Make sure we allow VPP to clean up the message rings.
        atexit.register(vpp_atexit, weakref.ref(self))

        # Register error handler
        vpp_api.vac_set_error_handler(vac_error_handler)

        # Support legacy CFFI
        # from_buffer supported from 1.8.0
        (major, minor, patch) = [int(s) for s in
                                 cffi.__version__.split('.', 3)]
        if major >= 1 and minor >= 8:
            self._write = self._write_new_cffi
        else:
            self._write = self._write_legacy_cffi

    class ContextId(object):
        """Thread-safe provider of unique context IDs."""
        def __init__(self):
            self.context = 0
            self.lock = threading.Lock()

        def __call__(self):
            """Get a new unique (or, at least, not recently used) context."""
            with self.lock:
                self.context += 1
                return self.context
    get_context = ContextId()

    @classmethod
    def find_api_dir(cls):
        """Attempt to find the best directory in which API definition
        files may reside. If the value VPP_API_DIR exists in the environment
        then it is first on the search list. If we're inside a recognized
        location in a VPP source tree (src/scripts and src/vpp-api/python)
        then entries from there to the likely locations in build-root are
        added. Finally the location used by system packages is added.

        :returns: A single directory name, or None if no such directory
            could be found.
        """
        dirs = []

        if 'VPP_API_DIR' in os.environ:
            dirs.append(os.environ['VPP_API_DIR'])

        # perhaps we're in the 'src/scripts' or 'src/vpp-api/python' dir;
        # in which case, plot a course to likely places in the src tree
        import __main__ as main
        if hasattr(main, '__file__'):
            # get the path of the calling script
            localdir = os.path.dirname(os.path.realpath(main.__file__))
        else:
            # use cwd if there is no calling script
            localdir = os.getcwd()
        localdir_s = localdir.split(os.path.sep)

        def dmatch(dir):
            """Match dir against right-hand components of the script dir"""
            d = dir.split('/')  # param 'dir' assumes a / separator
            length = len(d)
            return len(localdir_s) > length and localdir_s[-length:] == d

        def sdir(srcdir, variant):
            """Build a path from srcdir to the staged API files of
            'variant'  (typically '' or '_debug')"""
            # Since 'core' and 'plugin' files are staged
            # in separate directories, we target the parent dir.
            return os.path.sep.join((
                srcdir,
                'build-root',
                'install-vpp%s-native' % variant,
                'vpp',
                'share',
                'vpp',
                'api',
            ))

        srcdir = None
        if dmatch('src/scripts'):
            srcdir = os.path.sep.join(localdir_s[:-2])
        elif dmatch('src/vpp-api/python'):
            srcdir = os.path.sep.join(localdir_s[:-3])
        elif dmatch('test'):
            # we're apparently running tests
            srcdir = os.path.sep.join(localdir_s[:-1])

        if srcdir:
            # we're in the source tree, try both the debug and release
            # variants.
            dirs.append(sdir(srcdir, '_debug'))
            dirs.append(sdir(srcdir, ''))

        # Test for staged copies of the scripts
        # For these, since we explicitly know if we're running a debug versus
        # release variant, target only the relevant directory
        if dmatch('build-root/install-vpp_debug-native/vpp/bin'):
            srcdir = os.path.sep.join(localdir_s[:-4])
            dirs.append(sdir(srcdir, '_debug'))
        if dmatch('build-root/install-vpp-native/vpp/bin'):
            srcdir = os.path.sep.join(localdir_s[:-4])
            dirs.append(sdir(srcdir, ''))

        # finally, try the location system packages typically install into
        dirs.append(os.path.sep.join(('', 'usr', 'share', 'vpp', 'api')))

        # check the directories for existance; first one wins
        for dir in dirs:
            if os.path.isdir(dir):
                return dir

        return None

    @classmethod
    def find_api_files(cls, api_dir=None, patterns='*'):
        """Find API definition files from the given directory tree with the
        given pattern. If no directory is given then find_api_dir() is used
        to locate one. If no pattern is given then all definition files found
        in the directory tree are used.

        :param api_dir: A directory tree in which to locate API definition
            files; subdirectories are descended into.
            If this is None then find_api_dir() is called to discover it.
        :param patterns: A list of patterns to use in each visited directory
            when looking for files.
            This can be a list/tuple object or a comma-separated string of
            patterns. Each value in the list will have leading/trialing
            whitespace stripped.
            The pattern specifies the first part of the filename, '.api.json'
            is appended.
            The results are de-duplicated, thus overlapping patterns are fine.
            If this is None it defaults to '*' meaning "all API files".
        :returns: A list of file paths for the API files found.
        """
        if api_dir is None:
            api_dir = cls.find_api_dir()
            if api_dir is None:
                raise RuntimeError("api_dir cannot be located")

        if isinstance(patterns, list) or isinstance(patterns, tuple):
            patterns = [p.strip() + '.api.json' for p in patterns]
        else:
            patterns = [p.strip() + '.api.json' for p in patterns.split(",")]

        api_files = []
        for root, dirnames, files in os.walk(api_dir):
            # iterate all given patterns and de-dup the result
            files = set(sum([fnmatch.filter(files, p) for p in patterns], []))
            for filename in files:
                api_files.append(os.path.join(root, filename))

        return api_files

    def status(self):
        """Debug function: report current VPP API status to stdout."""
        print('Connected') if self.connected else print('Not Connected')
        print('Read API definitions from', ', '.join(self.apifiles))

    def __struct(self, t, n=None, e=-1, vl=None):
        """Create a packing structure for a message."""
        base_types = {'u8': 'B',
                      'u16': 'H',
                      'u32': 'I',
                      'i32': 'i',
                      'u64': 'Q',
                      'f64': 'd', }

        if t in base_types:
            if not vl:
                if e > 0 and t == 'u8':
                    # Fixed byte array
                    s = struct.Struct('>' + str(e) + 's')
                    return s.size, s
                if e > 0:
                    # Fixed array of base type
                    s = struct.Struct('>' + base_types[t])
                    return s.size, [e, s]
                elif e == 0:
                    # Old style variable array
                    s = struct.Struct('>' + base_types[t])
                    return s.size, [-1, s]
            else:
                # Variable length array
                if t == 'u8':
                    s = struct.Struct('>s')
                    return s.size, [vl, s]
                else:
                    s = struct.Struct('>' + base_types[t])
                return s.size, [vl, s]

            s = struct.Struct('>' + base_types[t])
            return s.size, s

        if t in self.messages:
            size = self.messages[t]['sizes'][0]

            # Return a list in case of array
            if e > 0 and not vl:
                return size, [e, lambda self, encode, buf, offset, args: (
                    self.__struct_type(encode, self.messages[t], buf, offset,
                                       args))]
            if vl:
                return size, [vl, lambda self, encode, buf, offset, args: (
                    self.__struct_type(encode, self.messages[t], buf, offset,
                                       args))]
            elif e == 0:
                # Old style VLA
                raise NotImplementedError(1,
                                          'No support for compound types ' + t)
            return size, lambda self, encode, buf, offset, args: (
                self.__struct_type(encode, self.messages[t], buf, offset, args)
            )

        raise ValueError(1, 'Invalid message type: ' + t)

    def __struct_type(self, encode, msgdef, buf, offset, kwargs):
        """Get a message packer or unpacker."""
        if encode:
            return self.__struct_type_encode(msgdef, buf, offset, kwargs)
        else:
            return self.__struct_type_decode(msgdef, buf, offset)

    def __struct_type_encode(self, msgdef, buf, offset, kwargs):
        off = offset
        size = 0

        for k in kwargs:
            if k not in msgdef['args']:
                raise ValueError(1, 'Non existing argument [' + k + ']' +
                                    ' used in call to: ' +
                                 self.id_names[kwargs['_vl_msg_id']] + '()')

        for k, v in vpp_iterator(msgdef['args']):
            off += size
            if k in kwargs:
                if type(v) is list:
                    if callable(v[1]):
                        e = kwargs[v[0]] if v[0] in kwargs else v[0]
                        if e != len(kwargs[k]):
                            raise (ValueError(1,
                                              'Input list length mismatch: '
                                              '%s (%s != %s)' %
                                              (k, e, len(kwargs[k]))))
                        size = 0
                        for i in range(e):
                            size += v[1](self, True, buf, off + size,
                                         kwargs[k][i])
                    else:
                        if v[0] in kwargs:
                            kwargslen = kwargs[v[0]]
                            if kwargslen != len(kwargs[k]):
                                raise ValueError(1,
                                                 'Input list length mismatch:'
                                                 ' %s (%s != %s)' %
                                                 (k, kwargslen,
                                                  len(kwargs[k])))
                        else:
                            kwargslen = len(kwargs[k])
                        if v[1].size == 1:
                            buf[off:off + kwargslen] = bytearray(kwargs[k])
                            size = kwargslen
                        else:
                            size = 0
                            for i in kwargs[k]:
                                v[1].pack_into(buf, off + size, i)
                                size += v[1].size
                else:
                    if callable(v):
                        size = v(self, True, buf, off, kwargs[k])
                    else:
                        if type(kwargs[k]) is str and v.size < len(kwargs[k]):
                            raise ValueError(1,
                                             'Input list length mismatch: '
                                             '%s (%s < %s)' %
                                             (k, v.size, len(kwargs[k])))
                        v.pack_into(buf, off, kwargs[k])
                        size = v.size
            else:
                size = v.size if not type(v) is list else 0

        return off + size - offset

    def __getitem__(self, name):
        if name in self.messages:
            return self.messages[name]
        return None

    def get_size(self, sizes, kwargs):
        total_size = sizes[0]
        for e in sizes[1]:
            if e in kwargs and type(kwargs[e]) is list:
                total_size += len(kwargs[e]) * sizes[1][e]
        return total_size

    def encode(self, msgdef, kwargs):
        # Make suitably large buffer
        size = self.get_size(msgdef['sizes'], kwargs)
        buf = bytearray(size)
        offset = 0
        size = self.__struct_type(True, msgdef, buf, offset, kwargs)
        return buf[:offset + size]

    def decode(self, msgdef, buf):
        return self.__struct_type(False, msgdef, buf, 0, None)[1]

    def __struct_type_decode(self, msgdef, buf, offset):
        res = []
        off = offset
        size = 0
        for k, v in vpp_iterator(msgdef['args']):
            off += size
            if type(v) is list:
                lst = []
                if callable(v[1]):  # compound type
                    size = 0
                    if v[0] in msgdef['args']:  # vla
                        e = res[v[2]]
                    else:  # fixed array
                        e = v[0]
                    res.append(lst)
                    for i in range(e):
                        (s, l) = v[1](self, False, buf, off + size, None)
                        lst.append(l)
                        size += s
                    continue
                if v[1].size == 1:
                    if type(v[0]) is int:
                        size = len(buf) - off
                    else:
                        size = res[v[2]]
                    res.append(buf[off:off + size])
                else:
                    e = v[0] if type(v[0]) is int else res[v[2]]
                    if e == -1:
                        e = (len(buf) - off) / v[1].size
                    lst = []
                    res.append(lst)
                    size = 0
                    for i in range(e):
                        lst.append(v[1].unpack_from(buf, off + size)[0])
                        size += v[1].size
            else:
                if callable(v):
                    size = 0
                    (s, l) = v(self, False, buf, off, None)
                    res.append(l)
                    size += s
                else:
                    res.append(v.unpack_from(buf, off)[0])
                    size = v.size

        return off + size - offset, msgdef['return_tuple']._make(res)

    def ret_tup(self, name):
        if name in self.messages and 'return_tuple' in self.messages[name]:
            return self.messages[name]['return_tuple']
        return None

    def duplicate_check_ok(self, name, msgdef):
        crc = None
        for c in msgdef:
            if type(c) is dict and 'crc' in c:
                crc = c['crc']
                break
        if crc:
            # We can get duplicates because of imports
            if crc == self.messages[name]['crc']:
                return True
        return False

    def add_message(self, name, msgdef, typeonly=False):
        if name in self.messages:
            if typeonly:
                if self.duplicate_check_ok(name, msgdef):
                    return
            raise ValueError('Duplicate message name: ' + name)

        args = collections.OrderedDict()
        argtypes = collections.OrderedDict()
        fields = []
        msg = {}
        total_size = 0
        sizes = {}
        for i, f in enumerate(msgdef):
            if type(f) is dict and 'crc' in f:
                msg['crc'] = f['crc']
                continue
            field_type = f[0]
            field_name = f[1]
            if len(f) == 3 and f[2] == 0 and i != len(msgdef) - 2:
                raise ValueError('Variable Length Array must be last: ' + name)
            size, s = self.__struct(*f)
            args[field_name] = s
            if type(s) == list and type(s[0]) == int and \
               type(s[1]) == struct.Struct:
                if s[0] < 0:
                    sizes[field_name] = size
                else:
                    sizes[field_name] = size
                    total_size += s[0] * size
            else:
                sizes[field_name] = size
                total_size += size

            argtypes[field_name] = field_type
            if len(f) == 4:  # Find offset to # elements field
                idx = list(args.keys()).index(f[3]) - i
                args[field_name].append(idx)
            fields.append(field_name)
        msg['return_tuple'] = collections.namedtuple(name, fields,
                                                     rename=True)
        self.messages[name] = msg
        self.messages[name]['args'] = args
        self.messages[name]['argtypes'] = argtypes
        self.messages[name]['typeonly'] = typeonly
        self.messages[name]['sizes'] = [total_size, sizes]
        return self.messages[name]

    def add_type(self, name, typedef):
        return self.add_message('vl_api_' + name + '_t', typedef,
                                typeonly=True)

    def make_function(self, name, i, msgdef, multipart, async):
        if (async):
            def f(**kwargs):
                return self._call_vpp_async(i, msgdef, **kwargs)
        else:
            def f(**kwargs):
                return self._call_vpp(i, msgdef, multipart, **kwargs)
        args = self.messages[name]['args']
        argtypes = self.messages[name]['argtypes']
        f.__name__ = str(name)
        f.__doc__ = ", ".join(["%s %s" %
                               (argtypes[k], k) for k in args.keys()])
        return f

    @property
    def api(self):
        if not hasattr(self, "_api"):
            raise Exception("Not connected, api definitions not available")
        return self._api

    def _register_functions(self, async=False):
        self.id_names = [None] * (self.vpp_dictionary_maxid + 1)
        self.id_msgdef = [None] * (self.vpp_dictionary_maxid + 1)
        self._api = Empty()
        for name, msgdef in vpp_iterator(self.messages):
            if self.messages[name]['typeonly']:
                continue
            crc = self.messages[name]['crc']
            n = name + '_' + crc[2:]
            i = vpp_api.vac_get_msg_index(n.encode())
            if i > 0:
                self.id_msgdef[i] = msgdef
                self.id_names[i] = name
                multipart = True if name.find('_dump') > 0 else False
                f = self.make_function(name, i, msgdef, multipart, async)
                setattr(self._api, name, FuncWrapper(f))
            else:
                self.logger.debug(
                    'No such message type or failed CRC checksum: %s', n)

    def _write_new_cffi(self, buf):
        """Send a binary-packed message to VPP."""
        if not self.connected:
            raise IOError(1, 'Not connected')
        return vpp_api.vac_write(ffi.from_buffer(buf), len(buf))

    def _write_legacy_cffi(self, buf):
        """Send a binary-packed message to VPP."""
        if not self.connected:
            raise IOError(1, 'Not connected')
        return vpp_api.vac_write(bytes(buf), len(buf))

    def _read(self):
        if not self.connected:
            raise IOError(1, 'Not connected')
        mem = ffi.new("char **")
        size = ffi.new("int *")
        rv = vpp_api.vac_read(mem, size, self.read_timeout)
        if rv:
            raise IOError(rv, 'vac_read failed')
        msg = bytes(ffi.buffer(mem[0], size[0]))
        vpp_api.vac_free(mem[0])
        return msg

    def connect_internal(self, name, msg_handler, chroot_prefix, rx_qlen,
                         async):
        pfx = chroot_prefix.encode() if chroot_prefix else ffi.NULL
        rv = vpp_api.vac_connect(name.encode(), pfx, msg_handler, rx_qlen)
        if rv != 0:
            raise IOError(2, 'Connect failed')
        self.connected = True

        self.vpp_dictionary_maxid = vpp_api.vac_msg_table_max_index()
        self._register_functions(async=async)

        # Initialise control ping
        crc = self.messages['control_ping']['crc']
        self.control_ping_index = vpp_api.vac_get_msg_index(
            ('control_ping' + '_' + crc[2:]).encode())
        self.control_ping_msgdef = self.messages['control_ping']
        if self.async_thread:
            self.event_thread = threading.Thread(
                target=self.thread_msg_handler)
            self.event_thread.daemon = True
            self.event_thread.start()
        return rv

    def connect(self, name, chroot_prefix=None, async=False, rx_qlen=32):
        """Attach to VPP.

        name - the name of the client.
        chroot_prefix - if VPP is chroot'ed, the prefix of the jail
        async - if true, messages are sent without waiting for a reply
        rx_qlen - the length of the VPP message receive queue between
        client and server.
        """
        msg_handler = vac_callback_sync if not async else vac_callback_async
        return self.connect_internal(name, msg_handler, chroot_prefix, rx_qlen,
                                     async)

    def connect_sync(self, name, chroot_prefix=None, rx_qlen=32):
        """Attach to VPP in synchronous mode. Application must poll for events.

        name - the name of the client.
        chroot_prefix - if VPP is chroot'ed, the prefix of the jail
        rx_qlen - the length of the VPP message receive queue between
        client and server.
        """

        return self.connect_internal(name, ffi.NULL, chroot_prefix, rx_qlen,
                                     async=False)

    def disconnect(self):
        """Detach from VPP."""
        rv = vpp_api.vac_disconnect()
        self.connected = False
        self.message_queue.put("terminate event thread")
        return rv

    def msg_handler_sync(self, msg):
        """Process an incoming message from VPP in sync mode.

        The message may be a reply or it may be an async notification.
        """
        r = self.decode_incoming_msg(msg)
        if r is None:
            return

        # If we have a context, then use the context to find any
        # request waiting for a reply
        context = 0
        if hasattr(r, 'context') and r.context > 0:
            context = r.context

        if context == 0:
            # No context -> async notification that we feed to the callback
            self.message_queue.put_nowait(r)
        else:
            raise IOError(2, 'RPC reply message received in event handler')

    def decode_incoming_msg(self, msg):
        if not msg:
            self.logger.warning('vpp_api.read failed')
            return

        i, ci = self.header.unpack_from(msg, 0)
        if self.id_names[i] == 'rx_thread_exit':
            return

        #
        # Decode message and returns a tuple.
        #
        msgdef = self.id_msgdef[i]
        if not msgdef:
            raise IOError(2, 'Reply message undefined')

        r = self.decode(msgdef, msg)

        return r

    def msg_handler_async(self, msg):
        """Process a message from VPP in async mode.

        In async mode, all messages are returned to the callback.
        """
        r = self.decode_incoming_msg(msg)
        if r is None:
            return

        msgname = type(r).__name__

        if self.event_callback:
            self.event_callback(msgname, r)

    def _control_ping(self, context):
        """Send a ping command."""
        self._call_vpp_async(self.control_ping_index,
                             self.control_ping_msgdef,
                             context=context)

    def _call_vpp(self, i, msgdef, multipart, **kwargs):
        """Given a message, send the message and await a reply.

        msgdef - the message packing definition
        i - the message type index
        multipart - True if the message returns multiple
        messages in return.
        context - context number - chosen at random if not
        supplied.
        The remainder of the kwargs are the arguments to the API call.

        The return value is the message or message array containing
        the response.  It will raise an IOError exception if there was
        no response within the timeout window.
        """

        if 'context' not in kwargs:
            context = self.get_context()
            kwargs['context'] = context
        else:
            context = kwargs['context']
        kwargs['_vl_msg_id'] = i
        b = self.encode(msgdef, kwargs)

        vpp_api.vac_rx_suspend()
        self._write(b)

        if multipart:
            # Send a ping after the request - we use its response
            # to detect that we have seen all results.
            self._control_ping(context)

        # Block until we get a reply.
        rl = []
        while (True):
            msg = self._read()
            if not msg:
                raise IOError(2, 'VPP API client: read failed')

            r = self.decode_incoming_msg(msg)
            msgname = type(r).__name__
            if context not in r or r.context == 0 or context != r.context:
                self.message_queue.put_nowait(r)
                continue

            if not multipart:
                rl = r
                break
            if msgname == 'control_ping_reply':
                break

            rl.append(r)

        vpp_api.vac_rx_resume()

        return rl

    def _call_vpp_async(self, i, msgdef, **kwargs):
        """Given a message, send the message and await a reply.

        msgdef - the message packing definition
        i - the message type index
        context - context number - chosen at random if not
        supplied.
        The remainder of the kwargs are the arguments to the API call.
        """
        if 'context' not in kwargs:
            context = self.get_context()
            kwargs['context'] = context
        else:
            context = kwargs['context']
        kwargs['_vl_msg_id'] = i
        b = self.encode(msgdef, kwargs)

        self._write(b)

    def register_event_callback(self, callback):
        """Register a callback for async messages.

        This will be called for async notifications in sync mode,
        and all messages in async mode.  In sync mode, replies to
        requests will not come here.

        callback is a fn(msg_type_name, msg_type) that will be
        called when a message comes in.  While this function is
        executing, note that (a) you are in a background thread and
        may wish to use threading.Lock to protect your datastructures,
        and (b) message processing from VPP will stop (so if you take
        a long while about it you may provoke reply timeouts or cause
        VPP to fill the RX buffer).  Passing None will disable the
        callback.
        """
        self.event_callback = callback

    def thread_msg_handler(self):
        """Python thread calling the user registerd message handler.

        This is to emulate the old style event callback scheme. Modern
        clients should provide their own thread to poll the event
        queue.
        """
        while True:
            r = self.message_queue.get()
            if r == "terminate event thread":
                break
            msgname = type(r).__name__
            if self.event_callback:
                self.event_callback(msgname, r)


# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4