summaryrefslogtreecommitdiffstats
path: root/lib/zmq.hpp
blob: 74a0574d842eacf644234677668404d45fa8350f (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
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
/*
    Copyright (c) 2016-2017 ZeroMQ community
    Copyright (c) 2009-2011 250bpm s.r.o.
    Copyright (c) 2011 Botond Ballo
    Copyright (c) 2007-2009 iMatix Corporation

    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to
    deal in the Software without restriction, including without limitation the
    rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
    sell copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
    IN THE SOFTWARE.
*/

#ifndef __ZMQ_HPP_INCLUDED__
#define __ZMQ_HPP_INCLUDED__

// macros defined if has a specific standard or greater
#if (defined(__cplusplus) && __cplusplus >= 201103L) || (defined(_MSC_VER) && _MSC_VER >= 1900)
    #define ZMQ_CPP11
#endif
#if (defined(__cplusplus) && __cplusplus >= 201402L) || \
    (defined(_HAS_CXX14) && _HAS_CXX14 == 1) || \
    (defined(_HAS_CXX17) && _HAS_CXX17 == 1) // _HAS_CXX14 might not be defined when using C++17 on MSVC
    #define ZMQ_CPP14
#endif
#if (defined(__cplusplus) && __cplusplus >= 201703L) || (defined(_HAS_CXX17) && _HAS_CXX17 == 1)
    #define ZMQ_CPP17
#endif

#if defined(ZMQ_CPP14)
#define ZMQ_DEPRECATED(msg) [[deprecated(msg)]]
#elif defined(_MSC_VER)
#define ZMQ_DEPRECATED(msg) __declspec(deprecated(msg))
#elif defined(__GNUC__)
#define ZMQ_DEPRECATED(msg) __attribute__((deprecated(msg)))
#endif

#if defined(ZMQ_CPP17)
#define ZMQ_NODISCARD [[nodiscard]]
#else
#define ZMQ_NODISCARD
#endif

#if defined(ZMQ_CPP11)
#define ZMQ_NOTHROW noexcept
#define ZMQ_EXPLICIT explicit
#define ZMQ_OVERRIDE override
#define ZMQ_NULLPTR nullptr
#define ZMQ_CONSTEXPR_FN constexpr
#define ZMQ_CONSTEXPR_VAR constexpr
#else
#define ZMQ_NOTHROW throw()
#define ZMQ_EXPLICIT
#define ZMQ_OVERRIDE
#define ZMQ_NULLPTR 0
#define ZMQ_CONSTEXPR_FN
#define ZMQ_CONSTEXPR_VAR const
#endif

#include <zmq.h>

#include <cassert>
#include <cstring>

#include <algorithm>
#include <exception>
#include <iomanip>
#include <sstream>
#include <string>
#include <vector>
#ifdef ZMQ_CPP11
#include <array>
#include <chrono>
#include <tuple>
#include <memory>
#endif
#ifdef ZMQ_CPP17
#ifdef __has_include
#if __has_include(<optional>)
#include <optional>
#define ZMQ_HAS_OPTIONAL 1
#endif
#if __has_include(<string_view>)
#include <string_view>
#define ZMQ_HAS_STRING_VIEW 1
#endif
#endif

#endif

/*  Version macros for compile-time API version detection                     */
#define CPPZMQ_VERSION_MAJOR 4
#define CPPZMQ_VERSION_MINOR 6
#define CPPZMQ_VERSION_PATCH 0

#define CPPZMQ_VERSION                                                              \
    ZMQ_MAKE_VERSION(CPPZMQ_VERSION_MAJOR, CPPZMQ_VERSION_MINOR,                    \
                     CPPZMQ_VERSION_PATCH)

//  Detect whether the compiler supports C++11 rvalue references.
#if (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 2))   \
     && defined(__GXX_EXPERIMENTAL_CXX0X__))
#define ZMQ_HAS_RVALUE_REFS
#define ZMQ_DELETED_FUNCTION = delete
#elif defined(__clang__)
#if __has_feature(cxx_rvalue_references)
#define ZMQ_HAS_RVALUE_REFS
#endif

#if __has_feature(cxx_deleted_functions)
#define ZMQ_DELETED_FUNCTION = delete
#else
#define ZMQ_DELETED_FUNCTION
#endif
#elif defined(_MSC_VER) && (_MSC_VER >= 1900)
#define ZMQ_HAS_RVALUE_REFS
#define ZMQ_DELETED_FUNCTION = delete
#elif defined(_MSC_VER) && (_MSC_VER >= 1600)
#define ZMQ_HAS_RVALUE_REFS
#define ZMQ_DELETED_FUNCTION
#else
#define ZMQ_DELETED_FUNCTION
#endif

#if defined(ZMQ_CPP11) && !defined(__llvm__) && !defined(__INTEL_COMPILER) \
    && defined(__GNUC__) && __GNUC__ < 5
#define ZMQ_CPP11_PARTIAL
#elif defined(__GLIBCXX__) && __GLIBCXX__ < 20160805
//the date here is the last date of gcc 4.9.4, which
// effectively means libstdc++ from gcc 5.5 and higher won't trigger this branch
#define ZMQ_CPP11_PARTIAL
#endif

#ifdef ZMQ_CPP11
#ifdef ZMQ_CPP11_PARTIAL
#define ZMQ_IS_TRIVIALLY_COPYABLE(T) __has_trivial_copy(T)
#else
#include <type_traits>
#define ZMQ_IS_TRIVIALLY_COPYABLE(T) std::is_trivially_copyable<T>::value
#endif
#endif

#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(3, 3, 0)
#define ZMQ_NEW_MONITOR_EVENT_LAYOUT
#endif

#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 1, 0)
#define ZMQ_HAS_PROXY_STEERABLE
/*  Socket event data  */
typedef struct
{
    uint16_t event; // id of the event as bitfield
    int32_t value;  // value is either error code, fd or reconnect interval
} zmq_event_t;
#endif

// Avoid using deprecated message receive function when possible
#if ZMQ_VERSION < ZMQ_MAKE_VERSION(3, 2, 0)
#define zmq_msg_recv(msg, socket, flags) zmq_recvmsg(socket, msg, flags)
#endif


// In order to prevent unused variable warnings when building in non-debug
// mode use this macro to make assertions.
#ifndef NDEBUG
#define ZMQ_ASSERT(expression) assert(expression)
#else
#define ZMQ_ASSERT(expression) (void) (expression)
#endif

namespace zmq
{

#ifdef ZMQ_CPP11
namespace detail
{
namespace ranges
{
using std::begin;
using std::end;
template<class T>
auto begin(T&& r) -> decltype(begin(std::forward<T>(r)))
{
    return begin(std::forward<T>(r));
}
template<class T>
auto end(T&& r) -> decltype(end(std::forward<T>(r)))
{
    return end(std::forward<T>(r));
}
} // namespace ranges

template<class T> using void_t = void;

template<class Iter>
using iter_value_t = typename std::iterator_traits<Iter>::value_type;

template<class Range>
using range_iter_t = decltype(
  ranges::begin(std::declval<typename std::remove_reference<Range>::type &>()));

template<class Range>
using range_value_t = iter_value_t<range_iter_t<Range>>;

template<class T, class = void> struct is_range : std::false_type
{
};

template<class T>
struct is_range<
  T,
  void_t<decltype(
    ranges::begin(std::declval<typename std::remove_reference<T>::type &>())
    == ranges::end(std::declval<typename std::remove_reference<T>::type &>()))>>
    : std::true_type
{
};

} // namespace detail
#endif

typedef zmq_free_fn free_fn;
typedef zmq_pollitem_t pollitem_t;

class error_t : public std::exception
{
  public:
    error_t() : errnum(zmq_errno()) {}
    virtual const char *what() const ZMQ_NOTHROW ZMQ_OVERRIDE { return zmq_strerror(errnum); }
    int num() const { return errnum; }

  private:
    int errnum;
};

inline int poll(zmq_pollitem_t *items_, size_t nitems_, long timeout_ = -1)
{
    int rc = zmq_poll(items_, static_cast<int>(nitems_), timeout_);
    if (rc < 0)
        throw error_t();
    return rc;
}

ZMQ_DEPRECATED("from 4.3.1, use poll taking non-const items")
inline int poll(zmq_pollitem_t const *items_, size_t nitems_, long timeout_ = -1)
{
    return poll(const_cast<zmq_pollitem_t *>(items_), nitems_, timeout_);
}

#ifdef ZMQ_CPP11
ZMQ_DEPRECATED("from 4.3.1, use poll taking non-const items")
inline int
poll(zmq_pollitem_t const *items, size_t nitems, std::chrono::milliseconds timeout)
{
    return poll(const_cast<zmq_pollitem_t *>(items), nitems, static_cast<long>(timeout.count()));
}

ZMQ_DEPRECATED("from 4.3.1, use poll taking non-const items")
inline int poll(std::vector<zmq_pollitem_t> const &items,
                std::chrono::milliseconds timeout)
{
    return poll(const_cast<zmq_pollitem_t *>(items.data()), items.size(), static_cast<long>(timeout.count()));
}

ZMQ_DEPRECATED("from 4.3.1, use poll taking non-const items")
inline int poll(std::vector<zmq_pollitem_t> const &items, long timeout_ = -1)
{
    return poll(const_cast<zmq_pollitem_t *>(items.data()), items.size(), timeout_);
}

inline int
poll(zmq_pollitem_t *items, size_t nitems, std::chrono::milliseconds timeout)
{
    return poll(items, nitems, static_cast<long>(timeout.count()));
}

inline int poll(std::vector<zmq_pollitem_t> &items,
                std::chrono::milliseconds timeout)
{
    return poll(items.data(), items.size(), static_cast<long>(timeout.count()));
}

inline int poll(std::vector<zmq_pollitem_t> &items, long timeout_ = -1)
{
    return poll(items.data(), items.size(), timeout_);
}
#endif


inline void version(int *major_, int *minor_, int *patch_)
{
    zmq_version(major_, minor_, patch_);
}

#ifdef ZMQ_CPP11
inline std::tuple<int, int, int> version()
{
    std::tuple<int, int, int> v;
    zmq_version(&std::get<0>(v), &std::get<1>(v), &std::get<2>(v));
    return v;
}
#endif

class message_t
{
  public:
    message_t() ZMQ_NOTHROW
    {
        int rc = zmq_msg_init(&msg);
        ZMQ_ASSERT(rc == 0);
    }

    explicit message_t(size_t size_)
    {
        int rc = zmq_msg_init_size(&msg, size_);
        if (rc != 0)
            throw error_t();
    }

    template<class ForwardIter> message_t(ForwardIter first, ForwardIter last)
    {
        typedef typename std::iterator_traits<ForwardIter>::value_type value_t;

        assert(std::distance(first, last) >= 0);
        size_t const size_ =
          static_cast<size_t>(std::distance(first, last)) * sizeof(value_t);
        int const rc = zmq_msg_init_size(&msg, size_);
        if (rc != 0)
            throw error_t();
        std::copy(first, last, data<value_t>());
    }

    message_t(const void *data_, size_t size_)
    {
        int rc = zmq_msg_init_size(&msg, size_);
        if (rc != 0)
            throw error_t();
        memcpy(data(), data_, size_);
    }

    message_t(void *data_, size_t size_, free_fn *ffn_, void *hint_ = ZMQ_NULLPTR)
    {
        int rc = zmq_msg_init_data(&msg, data_, size_, ffn_, hint_);
        if (rc != 0)
            throw error_t();
    }

#if defined(ZMQ_CPP11) && !defined(ZMQ_CPP11_PARTIAL)
    template<class Range,
             typename = typename std::enable_if<
               detail::is_range<Range>::value
               && ZMQ_IS_TRIVIALLY_COPYABLE(detail::range_value_t<Range>)
               && !std::is_same<Range, message_t>::value>::type>
    explicit message_t(const Range &rng) :
        message_t(detail::ranges::begin(rng), detail::ranges::end(rng))
    {
    }
#endif

#ifdef ZMQ_HAS_RVALUE_REFS
    message_t(message_t &&rhs) ZMQ_NOTHROW : msg(rhs.msg)
    {
        int rc = zmq_msg_init(&rhs.msg);
        ZMQ_ASSERT(rc == 0);
    }

    message_t &operator=(message_t &&rhs) ZMQ_NOTHROW
    {
        std::swap(msg, rhs.msg);
        return *this;
    }
#endif

    ~message_t() ZMQ_NOTHROW
    {
        int rc = zmq_msg_close(&msg);
        ZMQ_ASSERT(rc == 0);
    }

    void rebuild()
    {
        int rc = zmq_msg_close(&msg);
        if (rc != 0)
            throw error_t();
        rc = zmq_msg_init(&msg);
        ZMQ_ASSERT(rc == 0);
    }

    void rebuild(size_t size_)
    {
        int rc = zmq_msg_close(&msg);
        if (rc != 0)
            throw error_t();
        rc = zmq_msg_init_size(&msg, size_);
        if (rc != 0)
            throw error_t();
    }

    void rebuild(const void *data_, size_t size_)
    {
        int rc = zmq_msg_close(&msg);
        if (rc != 0)
            throw error_t();
        rc = zmq_msg_init_size(&msg, size_);
        if (rc != 0)
            throw error_t();
        memcpy(data(), data_, size_);
    }

    void rebuild(void *data_, size_t size_, free_fn *ffn_, void *hint_ = ZMQ_NULLPTR)
    {
        int rc = zmq_msg_close(&msg);
        if (rc != 0)
            throw error_t();
        rc = zmq_msg_init_data(&msg, data_, size_, ffn_, hint_);
        if (rc != 0)
            throw error_t();
    }

    ZMQ_DEPRECATED("from 4.3.1, use move taking non-const reference instead")
    void move(message_t const *msg_)
    {
        int rc = zmq_msg_move(&msg, const_cast<zmq_msg_t *>(msg_->handle()));
        if (rc != 0)
            throw error_t();
    }

    void move(message_t &msg_)
    {
        int rc = zmq_msg_move(&msg, msg_.handle());
        if (rc != 0)
            throw error_t();
    }

    ZMQ_DEPRECATED("from 4.3.1, use copy taking non-const reference instead")
    void copy(message_t const *msg_)
    {
        int rc = zmq_msg_copy(&msg, const_cast<zmq_msg_t *>(msg_->handle()));
        if (rc != 0)
            throw error_t();
    }

    void copy(message_t &msg_)
    {
        int rc = zmq_msg_copy(&msg, msg_.handle());
        if (rc != 0)
            throw error_t();
    }

    bool more() const ZMQ_NOTHROW
    {
        int rc = zmq_msg_more(const_cast<zmq_msg_t *>(&msg));
        return rc != 0;
    }

    void *data() ZMQ_NOTHROW { return zmq_msg_data(&msg); }

    const void *data() const ZMQ_NOTHROW
    {
        return zmq_msg_data(const_cast<zmq_msg_t *>(&msg));
    }

    size_t size() const ZMQ_NOTHROW
    {
        return zmq_msg_size(const_cast<zmq_msg_t *>(&msg));
    }

    ZMQ_NODISCARD bool empty() const ZMQ_NOTHROW
    {
        return size() == 0u;
    }

    template<typename T> T *data() ZMQ_NOTHROW { return static_cast<T *>(data()); }

    template<typename T> T const *data() const ZMQ_NOTHROW
    {
        return static_cast<T const *>(data());
    }

    ZMQ_DEPRECATED("from 4.3.0, use operator== instead")
    bool equal(const message_t *other) const ZMQ_NOTHROW
    {
        return *this == *other;
    }

    bool operator==(const message_t &other) const ZMQ_NOTHROW
    {
        const size_t my_size = size();
        return my_size == other.size() && 0 == memcmp(data(), other.data(), my_size);
    }

    bool operator!=(const message_t &other) const ZMQ_NOTHROW
    {
        return !(*this == other);
    }

#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(3, 2, 0)
    int get(int property_)
    {
        int value = zmq_msg_get(&msg, property_);
        if (value == -1)
            throw error_t();
        return value;
    }
#endif

#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 1, 0)
    const char *gets(const char *property_)
    {
        const char *value = zmq_msg_gets(&msg, property_);
        if (value == ZMQ_NULLPTR)
            throw error_t();
        return value;
    }
#endif

#if defined(ZMQ_BUILD_DRAFT_API) && ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 0)
    uint32_t routing_id() const
    {
        return zmq_msg_routing_id(const_cast<zmq_msg_t*>(&msg));
    }

    void set_routing_id(uint32_t routing_id)
    {
        int rc = zmq_msg_set_routing_id(&msg, routing_id);
        if (rc != 0)
            throw error_t();
    }

    const char* group() const
    {
        return zmq_msg_group(const_cast<zmq_msg_t*>(&msg));
    }

    void set_group(const char* group)
    {
        int rc = zmq_msg_set_group(&msg, group);
        if (rc != 0)
            throw error_t();
    }
#endif

    // interpret message content as a string
    std::string to_string() const
    {
        return std::string(static_cast<const char*>(data()), size());
    }
#ifdef ZMQ_CPP17
    // interpret message content as a string
    std::string_view to_string_view() const noexcept
    {
        return std::string_view(static_cast<const char*>(data()), size());
    }
#endif

    /** Dump content to string for debugging.
    *   Ascii chars are readable, the rest is printed as hex.
    *   Probably ridiculously slow.
    *   Use to_string() or to_string_view() for
    *   interpreting the message as a string.
    */
    std::string str() const
    {
        // Partly mutuated from the same method in zmq::multipart_t
        std::stringstream os;

        const unsigned char *msg_data = this->data<unsigned char>();
        unsigned char byte;
        size_t size = this->size();
        int is_ascii[2] = {0, 0};

        os << "zmq::message_t [size " << std::dec << std::setw(3)
           << std::setfill('0') << size << "] (";
        // Totally arbitrary
        if (size >= 1000) {
            os << "... too big to print)";
        } else {
            while (size--) {
                byte = *msg_data++;

                is_ascii[1] = (byte >= 32 && byte < 127);
                if (is_ascii[1] != is_ascii[0])
                    os << " "; // Separate text/non text

                if (is_ascii[1]) {
                    os << byte;
                } else {
                    os << std::hex << std::uppercase << std::setw(2)
                       << std::setfill('0') << static_cast<short>(byte);
                }
                is_ascii[0] = is_ascii[1];
            }
            os << ")";
        }
        return os.str();
    }

    void swap(message_t &other) ZMQ_NOTHROW
    {
        // this assumes zmq::msg_t from libzmq is trivially relocatable
        std::swap(msg, other.msg);
    }

    ZMQ_NODISCARD zmq_msg_t *handle() ZMQ_NOTHROW { return &msg; }
    ZMQ_NODISCARD const zmq_msg_t *handle() const ZMQ_NOTHROW { return &msg; }

  private:
    //  The underlying message
    zmq_msg_t msg;

    //  Disable implicit message copying, so that users won't use shared
    //  messages (less efficient) without being aware of the fact.
    message_t(const message_t &) ZMQ_DELETED_FUNCTION;
    void operator=(const message_t &) ZMQ_DELETED_FUNCTION;
};

inline void swap(message_t &a, message_t &b) ZMQ_NOTHROW
{
    a.swap(b);
}

class context_t
{
  public:
    context_t()
    {
        ptr = zmq_ctx_new();
        if (ptr == ZMQ_NULLPTR)
            throw error_t();
    }


    explicit context_t(int io_threads_,
                              int max_sockets_ = ZMQ_MAX_SOCKETS_DFLT)
    {
        ptr = zmq_ctx_new();
        if (ptr == ZMQ_NULLPTR)
            throw error_t();

        int rc = zmq_ctx_set(ptr, ZMQ_IO_THREADS, io_threads_);
        ZMQ_ASSERT(rc == 0);

        rc = zmq_ctx_set(ptr, ZMQ_MAX_SOCKETS, max_sockets_);
        ZMQ_ASSERT(rc == 0);
    }

#ifdef ZMQ_HAS_RVALUE_REFS
    context_t(context_t &&rhs) ZMQ_NOTHROW : ptr(rhs.ptr) { rhs.ptr = ZMQ_NULLPTR; }
    context_t &operator=(context_t &&rhs) ZMQ_NOTHROW
    {
        close();
        std::swap(ptr, rhs.ptr);
        return *this;
    }
#endif

    int setctxopt(int option_, int optval_)
    {
        int rc = zmq_ctx_set(ptr, option_, optval_);
        ZMQ_ASSERT(rc == 0);
        return rc;
    }

    int getctxopt(int option_) { return zmq_ctx_get(ptr, option_); }

    ~context_t() ZMQ_NOTHROW { close(); }

    void close() ZMQ_NOTHROW
    {
        if (ptr == ZMQ_NULLPTR)
            return;

        int rc;
        do {
            rc = zmq_ctx_destroy(ptr);
        } while (rc == -1 && errno == EINTR);

        ZMQ_ASSERT(rc == 0);
        ptr = ZMQ_NULLPTR;
    }

    //  Be careful with this, it's probably only useful for
    //  using the C api together with an existing C++ api.
    //  Normally you should never need to use this.
    ZMQ_EXPLICIT operator void *() ZMQ_NOTHROW { return ptr; }

    ZMQ_EXPLICIT operator void const *() const ZMQ_NOTHROW { return ptr; }

    operator bool() const ZMQ_NOTHROW { return ptr != ZMQ_NULLPTR; }

    void swap(context_t &other) ZMQ_NOTHROW
    {
        std::swap(ptr, other.ptr);
    }

  private:
    void *ptr;

    context_t(const context_t &) ZMQ_DELETED_FUNCTION;
    void operator=(const context_t &) ZMQ_DELETED_FUNCTION;
};

inline void swap(context_t &a, context_t &b) ZMQ_NOTHROW {
    a.swap(b);
}

#ifdef ZMQ_CPP11

struct recv_buffer_size
{
    size_t size;    // number of bytes written to buffer
    size_t untruncated_size;  // untruncated message size in bytes

    ZMQ_NODISCARD bool truncated() const noexcept
    {
        return size != untruncated_size;
    }
};

#if defined(ZMQ_HAS_OPTIONAL) && (ZMQ_HAS_OPTIONAL > 0)

using send_result_t = std::optional<size_t>;
using recv_result_t = std::optional<size_t>;
using recv_buffer_result_t = std::optional<recv_buffer_size>;

#else

namespace detail
{
// A C++11 type emulating the most basic
// operations of std::optional for trivial types
template<class T> class trivial_optional
{
  public:
    static_assert(std::is_trivial<T>::value, "T must be trivial");
    using value_type = T;

    trivial_optional() = default;
    trivial_optional(T value) noexcept : _value(value), _has_value(true) {}

    const T *operator->() const noexcept
    {
        assert(_has_value);
        return &_value;
    }
    T *operator->() noexcept
    {
        assert(_has_value);
        return &_value;
    }

    const T &operator*() const noexcept
    {
        assert(_has_value);
        return _value;
    }
    T &operator*() noexcept
    {
        assert(_has_value);
        return _value;
    }

    T &value()
    {
        if (!_has_value)
            throw std::exception();
        return _value;
    }
    const T &value() const
    {
        if (!_has_value)
            throw std::exception();
        return _value;
    }

    explicit operator bool() const noexcept { return _has_value; }
    bool has_value() const noexcept { return _has_value; }

  private:
    T _value{};
    bool _has_value{false};
};
} // namespace detail

using send_result_t = detail::trivial_optional<size_t>;
using recv_result_t = detail::trivial_optional<size_t>;
using recv_buffer_result_t = detail::trivial_optional<recv_buffer_size>;

#endif

namespace detail
{

template<class T>
constexpr T enum_bit_or(T a, T b) noexcept
{
    static_assert(std::is_enum<T>::value, "must be enum");
    using U = typename std::underlying_type<T>::type;
    return static_cast<T>(static_cast<U>(a) | static_cast<U>(b));
}
template<class T>
constexpr T enum_bit_and(T a, T b) noexcept
{
    static_assert(std::is_enum<T>::value, "must be enum");
    using U = typename std::underlying_type<T>::type;
    return static_cast<T>(static_cast<U>(a) & static_cast<U>(b));
}
template<class T>
constexpr T enum_bit_xor(T a, T b) noexcept
{
    static_assert(std::is_enum<T>::value, "must be enum");
    using U = typename std::underlying_type<T>::type;
    return static_cast<T>(static_cast<U>(a) ^ static_cast<U>(b));
}
template<class T>
constexpr T enum_bit_not(T a) noexcept
{
    static_assert(std::is_enum<T>::value, "must be enum");
    using U = typename std::underlying_type<T>::type;
    return static_cast<T>(~static_cast<U>(a));
}
} // namespace detail

// partially satisfies named requirement BitmaskType
enum class send_flags : int
{
    none = 0,
    dontwait = ZMQ_DONTWAIT,
    sndmore = ZMQ_SNDMORE
};

constexpr send_flags operator|(send_flags a, send_flags b) noexcept
{
    return detail::enum_bit_or(a, b);
}
constexpr send_flags operator&(send_flags a, send_flags b) noexcept
{
    return detail::enum_bit_and(a, b);
}
constexpr send_flags operator^(send_flags a, send_flags b) noexcept
{
    return detail::enum_bit_xor(a, b);
}
constexpr send_flags operator~(send_flags a) noexcept
{
    return detail::enum_bit_not(a);
}

// partially satisfies named requirement BitmaskType
enum class recv_flags : int
{
    none = 0,
    dontwait = ZMQ_DONTWAIT
};

constexpr recv_flags operator|(recv_flags a, recv_flags b) noexcept
{
    return detail::enum_bit_or(a, b);
}
constexpr recv_flags operator&(recv_flags a, recv_flags b) noexcept
{
    return detail::enum_bit_and(a, b);
}
constexpr recv_flags operator^(recv_flags a, recv_flags b) noexcept
{
    return detail::enum_bit_xor(a, b);
}
constexpr recv_flags operator~(recv_flags a) noexcept
{
    return detail::enum_bit_not(a);
}


// mutable_buffer, const_buffer and buffer are based on
// the Networking TS specification, draft:
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/n4771.pdf

class mutable_buffer
{
  public:
    constexpr mutable_buffer() noexcept : _data(nullptr), _size(0) {}
    constexpr mutable_buffer(void *p, size_t n) noexcept : _data(p), _size(n)
    {
#ifdef ZMQ_CPP14
        assert(p != nullptr || n == 0);
#endif
    }

    constexpr void *data() const noexcept { return _data; }
    constexpr size_t size() const noexcept { return _size; }
    mutable_buffer &operator+=(size_t n) noexcept
    {
        // (std::min) is a workaround for when a min macro is defined
        const auto shift = (std::min)(n, _size);
        _data = static_cast<char *>(_data) + shift;
        _size -= shift;
        return *this;
    }

  private:
    void *_data;
    size_t _size;
};

inline mutable_buffer operator+(const mutable_buffer &mb, size_t n) noexcept
{
    return mutable_buffer(static_cast<char *>(mb.data()) + (std::min)(n, mb.size()),
                          mb.size() - (std::min)(n, mb.size()));
}
inline mutable_buffer operator+(size_t n, const mutable_buffer &mb) noexcept
{
    return mb + n;
}

class const_buffer
{
  public:
    constexpr const_buffer() noexcept : _data(nullptr), _size(0) {}
    constexpr const_buffer(const void *p, size_t n) noexcept : _data(p), _size(n)
    {
#ifdef ZMQ_CPP14
        assert(p != nullptr || n == 0);
#endif
    }
    constexpr const_buffer(const mutable_buffer &mb) noexcept :
        _data(mb.data()),
        _size(mb.size())
    {
    }

    constexpr const void *data() const noexcept { return _data; }
    constexpr size_t size() const noexcept { return _size; }
    const_buffer &operator+=(size_t n) noexcept
    {
        const auto shift = (std::min)(n, _size);
        _data = static_cast<const char *>(_data) + shift;
        _size -= shift;
        return *this;
    }

  private:
    const void *_data;
    size_t _size;
};

inline const_buffer operator+(const const_buffer &cb, size_t n) noexcept
{
    return const_buffer(static_cast<const char *>(cb.data())
                          + (std::min)(n, cb.size()),
                        cb.size() - (std::min)(n, cb.size()));
}
inline const_buffer operator+(size_t n, const const_buffer &cb) noexcept
{
    return cb + n;
}

// buffer creation

constexpr mutable_buffer buffer(void* p, size_t n) noexcept
{
    return mutable_buffer(p, n);
}
constexpr const_buffer buffer(const void* p, size_t n) noexcept
{
    return const_buffer(p, n);
}
constexpr mutable_buffer buffer(const mutable_buffer& mb) noexcept
{
    return mb;
}
inline mutable_buffer buffer(const mutable_buffer& mb, size_t n) noexcept
{
    return mutable_buffer(mb.data(), (std::min)(mb.size(), n));
}
constexpr const_buffer buffer(const const_buffer& cb) noexcept
{
    return cb;
}
inline const_buffer buffer(const const_buffer& cb, size_t n) noexcept
{
    return const_buffer(cb.data(), (std::min)(cb.size(), n));
}

namespace detail
{

template<class T>
struct is_buffer
{
    static constexpr bool value = 
        std::is_same<T, const_buffer>::value ||
        std::is_same<T, mutable_buffer>::value;
};

template<class T> struct is_pod_like
{
    // NOTE: The networking draft N4771 section 16.11 requires
    // T in the buffer functions below to be
    // trivially copyable OR standard layout.
    // Here we decide to be conservative and require both.
    static constexpr bool value =
      ZMQ_IS_TRIVIALLY_COPYABLE(T) && std::is_standard_layout<T>::value;
};

template<class C> constexpr auto seq_size(const C &c) noexcept -> decltype(c.size())
{
    return c.size();
}
template<class T, size_t N>
constexpr size_t seq_size(const T (&/*array*/)[N]) noexcept
{
    return N;
}

template<class Seq>
auto buffer_contiguous_sequence(Seq &&seq) noexcept
  -> decltype(buffer(std::addressof(*std::begin(seq)), size_t{}))
{
    using T = typename std::remove_cv<
      typename std::remove_reference<decltype(*std::begin(seq))>::type>::type;
    static_assert(detail::is_pod_like<T>::value, "T must be POD");

    const auto size = seq_size(seq);
    return buffer(size != 0u ? std::addressof(*std::begin(seq)) : nullptr,
                  size * sizeof(T));
}
template<class Seq>
auto buffer_contiguous_sequence(Seq &&seq, size_t n_bytes) noexcept
  -> decltype(buffer_contiguous_sequence(seq))
{
    using T = typename std::remove_cv<
      typename std::remove_reference<decltype(*std::begin(seq))>::type>::type;
    static_assert(detail::is_pod_like<T>::value, "T must be POD");

    const auto size = seq_size(seq);
    return buffer(size != 0u ? std::addressof(*std::begin(seq)) : nullptr,
                  (std::min)(size * sizeof(T), n_bytes));
}

} // namespace detail

// C array
template<class T, size_t N> mutable_buffer buffer(T (&data)[N]) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, size_t N>
mutable_buffer buffer(T (&data)[N], size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
template<class T, size_t N> const_buffer buffer(const T (&data)[N]) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, size_t N>
const_buffer buffer(const T (&data)[N], size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
// std::array
template<class T, size_t N> mutable_buffer buffer(std::array<T, N> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, size_t N>
mutable_buffer buffer(std::array<T, N> &data, size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
template<class T, size_t N>
const_buffer buffer(std::array<const T, N> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, size_t N>
const_buffer buffer(std::array<const T, N> &data, size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
template<class T, size_t N>
const_buffer buffer(const std::array<T, N> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, size_t N>
const_buffer buffer(const std::array<T, N> &data, size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
// std::vector
template<class T, class Allocator>
mutable_buffer buffer(std::vector<T, Allocator> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, class Allocator>
mutable_buffer buffer(std::vector<T, Allocator> &data, size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
template<class T, class Allocator>
const_buffer buffer(const std::vector<T, Allocator> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, class Allocator>
const_buffer buffer(const std::vector<T, Allocator> &data, size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
// std::basic_string
template<class T, class Traits, class Allocator>
mutable_buffer buffer(std::basic_string<T, Traits, Allocator> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, class Traits, class Allocator>
mutable_buffer buffer(std::basic_string<T, Traits, Allocator> &data,
                      size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
template<class T, class Traits, class Allocator>
const_buffer buffer(const std::basic_string<T, Traits, Allocator> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, class Traits, class Allocator>
const_buffer buffer(const std::basic_string<T, Traits, Allocator> &data,
                    size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}

#if defined(ZMQ_HAS_STRING_VIEW) && (ZMQ_HAS_STRING_VIEW > 0)
// std::basic_string_view
template<class T, class Traits>
const_buffer buffer(std::basic_string_view<T, Traits> data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, class Traits>
const_buffer buffer(std::basic_string_view<T, Traits> data, size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
#endif

// Buffer for a string literal (null terminated)
// where the buffer size excludes the terminating character.
// Equivalent to zmq::buffer(std::string_view("...")).
template<class Char, size_t N>
constexpr const_buffer str_buffer(const Char (&data)[N]) noexcept
{
    static_assert(detail::is_pod_like<Char>::value, "Char must be POD");
#ifdef ZMQ_CPP14
    assert(data[N - 1] == Char{0});
#endif
    return const_buffer(static_cast<const Char*>(data),
                        (N - 1) * sizeof(Char));
}

namespace literals
{
    constexpr const_buffer operator"" _zbuf(const char* str, size_t len) noexcept
    {
        return const_buffer(str, len * sizeof(char));
    }
    constexpr const_buffer operator"" _zbuf(const wchar_t* str, size_t len) noexcept
    {
        return const_buffer(str, len * sizeof(wchar_t));
    }
    constexpr const_buffer operator"" _zbuf(const char16_t* str, size_t len) noexcept
    {
        return const_buffer(str, len * sizeof(char16_t));
    }
    constexpr const_buffer operator"" _zbuf(const char32_t* str, size_t len) noexcept
    {
        return const_buffer(str, len * sizeof(char32_t));
    }
}

#endif // ZMQ_CPP11

namespace detail
{

class socket_base
{
public:
    socket_base() ZMQ_NOTHROW : _handle(ZMQ_NULLPTR) {}
    ZMQ_EXPLICIT socket_base(void *handle) ZMQ_NOTHROW : _handle(handle) {}

    template<typename T> void setsockopt(int option_, T const &optval)
    {
        setsockopt(option_, &optval, sizeof(T));
    }

    void setsockopt(int option_, const void *optval_, size_t optvallen_)
    {
        int rc = zmq_setsockopt(_handle, option_, optval_, optvallen_);
        if (rc != 0)
            throw error_t();
    }

    void getsockopt(int option_, void *optval_, size_t *optvallen_) const
    {
        int rc = zmq_getsockopt(_handle, option_, optval_, optvallen_);
        if (rc != 0)
            throw error_t();
    }

    template<typename T> T getsockopt(int option_) const
    {
        T optval;
        size_t optlen = sizeof(T);
        getsockopt(option_, &optval, &optlen);
        return optval;
    }

    void bind(std::string const &addr) { bind(addr.c_str()); }

    void bind(const char *addr_)
    {
        int rc = zmq_bind(_handle, addr_);
        if (rc != 0)
            throw error_t();
    }

    void unbind(std::string const &addr) { unbind(addr.c_str()); }

    void unbind(const char *addr_)
    {
        int rc = zmq_unbind(_handle, addr_);
        if (rc != 0)
            throw error_t();
    }

    void connect(std::string const &addr) { connect(addr.c_str()); }

    void connect(const char *addr_)
    {
        int rc = zmq_connect(_handle, addr_);
        if (rc != 0)
            throw error_t();
    }

    void disconnect(std::string const &addr) { disconnect(addr.c_str()); }

    void disconnect(const char *addr_)
    {
        int rc = zmq_disconnect(_handle, addr_);
        if (rc != 0)
            throw error_t();
    }

    bool connected() const ZMQ_NOTHROW { return (_handle != ZMQ_NULLPTR); }

#ifdef ZMQ_CPP11
    ZMQ_DEPRECATED("from 4.3.1, use send taking a const_buffer and send_flags")
#endif
    size_t send(const void *buf_, size_t len_, int flags_ = 0)
    {
        int nbytes = zmq_send(_handle, buf_, len_, flags_);
        if (nbytes >= 0)
            return static_cast<size_t>(nbytes);
        if (zmq_errno() == EAGAIN)
            return 0;
        throw error_t();
    }

#ifdef ZMQ_CPP11
    ZMQ_DEPRECATED("from 4.3.1, use send taking message_t and send_flags")
#endif
    bool send(message_t &msg_,
              int flags_ = 0) // default until removed
    {
        int nbytes = zmq_msg_send(msg_.handle(), _handle, flags_);
        if (nbytes >= 0)
            return true;
        if (zmq_errno() == EAGAIN)
            return false;
        throw error_t();
    }

    template<typename T>
#ifdef ZMQ_CPP11
    ZMQ_DEPRECATED("from 4.4.1, use send taking message_t or buffer (for contiguous ranges), and send_flags")
#endif
    bool send(T first, T last, int flags_ = 0)
    {
        zmq::message_t msg(first, last);
        int nbytes = zmq_msg_send(msg.handle(), _handle, flags_);
        if (nbytes >= 0)
            return true;
        if (zmq_errno() == EAGAIN)
            return false;
        throw error_t();
    }

#ifdef ZMQ_HAS_RVALUE_REFS
#ifdef ZMQ_CPP11
    ZMQ_DEPRECATED("from 4.3.1, use send taking message_t and send_flags")
#endif
    bool send(message_t &&msg_,
              int flags_ = 0) // default until removed
    {
        #ifdef ZMQ_CPP11
        return send(msg_, static_cast<send_flags>(flags_)).has_value();
        #else
        return send(msg_, flags_);
        #endif
    }
#endif

#ifdef ZMQ_CPP11
    send_result_t send(const_buffer buf, send_flags flags = send_flags::none)
    {
        const int nbytes =
          zmq_send(_handle, buf.data(), buf.size(), static_cast<int>(flags));
        if (nbytes >= 0)
            return static_cast<size_t>(nbytes);
        if (zmq_errno() == EAGAIN)
            return {};
        throw error_t();
    }

    send_result_t send(message_t &msg, send_flags flags)
    {
        int nbytes = zmq_msg_send(msg.handle(), _handle, static_cast<int>(flags));
        if (nbytes >= 0)
            return static_cast<size_t>(nbytes);
        if (zmq_errno() == EAGAIN)
            return {};
        throw error_t();
    }

    send_result_t send(message_t &&msg, send_flags flags)
    {
        return send(msg, flags);
    }
#endif

#ifdef ZMQ_CPP11
    ZMQ_DEPRECATED("from 4.3.1, use recv taking a mutable_buffer and recv_flags")
#endif
    size_t recv(void *buf_, size_t len_, int flags_ = 0)
    {
        int nbytes = zmq_recv(_handle, buf_, len_, flags_);
        if (nbytes >= 0)
            return static_cast<size_t>(nbytes);
        if (zmq_errno() == EAGAIN)
            return 0;
        throw error_t();
    }

#ifdef ZMQ_CPP11
    ZMQ_DEPRECATED("from 4.3.1, use recv taking a reference to message_t and recv_flags")
#endif
    bool recv(message_t *msg_, int flags_ = 0)
    {
        int nbytes = zmq_msg_recv(msg_->handle(), _handle, flags_);
        if (nbytes >= 0)
            return true;
        if (zmq_errno() == EAGAIN)
            return false;
        throw error_t();
    }

#ifdef ZMQ_CPP11
    ZMQ_NODISCARD
    recv_buffer_result_t recv(mutable_buffer buf,
                                    recv_flags flags = recv_flags::none)
    {
        const int nbytes =
          zmq_recv(_handle, buf.data(), buf.size(), static_cast<int>(flags));
        if (nbytes >= 0) {
            return recv_buffer_size{(std::min)(static_cast<size_t>(nbytes), buf.size()),
                                 static_cast<size_t>(nbytes)};
        }
        if (zmq_errno() == EAGAIN)
            return {};
        throw error_t();
    }

    ZMQ_NODISCARD
    recv_result_t recv(message_t &msg, recv_flags flags = recv_flags::none)
    {
        const int nbytes = zmq_msg_recv(msg.handle(), _handle, static_cast<int>(flags));
        if (nbytes >= 0) {
            assert(msg.size() == static_cast<size_t>(nbytes));
            return static_cast<size_t>(nbytes);
        }
        if (zmq_errno() == EAGAIN)
            return {};
        throw error_t();
    }
#endif

#if defined(ZMQ_BUILD_DRAFT_API) && ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 0)
    void join(const char* group)
    {
        int rc = zmq_join(_handle, group);
        if (rc != 0)
            throw error_t();
    }

    void leave(const char* group)
    {
        int rc = zmq_leave(_handle, group);
        if (rc != 0)
            throw error_t();
    }
#endif

    ZMQ_NODISCARD void *handle() ZMQ_NOTHROW { return _handle; }
    ZMQ_NODISCARD const void *handle() const ZMQ_NOTHROW { return _handle; }

    ZMQ_EXPLICIT operator bool() const ZMQ_NOTHROW { return _handle != ZMQ_NULLPTR; }
    // note: non-const operator bool can be removed once
    // operator void* is removed from socket_t
    ZMQ_EXPLICIT operator bool() ZMQ_NOTHROW { return _handle != ZMQ_NULLPTR; }

protected:
    void *_handle;
};
} // namespace detail

#ifdef ZMQ_CPP11
enum class socket_type : int
{
    req = ZMQ_REQ,
    rep = ZMQ_REP,
    dealer = ZMQ_DEALER,
    router = ZMQ_ROUTER,
    pub = ZMQ_PUB,
    sub = ZMQ_SUB,
    xpub = ZMQ_XPUB,
    xsub = ZMQ_XSUB,
    push = ZMQ_PUSH,
    pull = ZMQ_PULL,
#if defined(ZMQ_BUILD_DRAFT_API) && ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 0)
    server = ZMQ_SERVER,
    client = ZMQ_CLIENT,
    radio = ZMQ_RADIO,
    dish = ZMQ_DISH,
#endif
#if ZMQ_VERSION_MAJOR >= 4
    stream = ZMQ_STREAM,
#endif
    pair = ZMQ_PAIR
};
#endif

struct from_handle_t
{
    struct _private {}; // disabling use other than with from_handle
    ZMQ_CONSTEXPR_FN ZMQ_EXPLICIT from_handle_t(_private /*p*/) ZMQ_NOTHROW {}
};

ZMQ_CONSTEXPR_VAR from_handle_t from_handle = from_handle_t(from_handle_t::_private());

// A non-owning nullable reference to a socket.
// The reference is invalidated on socket close or destruction.
class socket_ref : public detail::socket_base
{
  public:
    socket_ref() ZMQ_NOTHROW : detail::socket_base() {}
#ifdef ZMQ_CPP11
    socket_ref(std::nullptr_t) ZMQ_NOTHROW : detail::socket_base() {}
#endif
    socket_ref(from_handle_t /*fh*/, void *handle) ZMQ_NOTHROW
        : detail::socket_base(handle) {}
};

#ifdef ZMQ_CPP11
inline bool operator==(socket_ref sr, std::nullptr_t /*p*/) ZMQ_NOTHROW
{
    return sr.handle() == nullptr;
}
inline bool operator==(std::nullptr_t /*p*/, socket_ref sr) ZMQ_NOTHROW
{
    return sr.handle() == nullptr;
}
inline bool operator!=(socket_ref sr, std::nullptr_t /*p*/) ZMQ_NOTHROW
{
    return !(sr == nullptr);
}
inline bool operator!=(std::nullptr_t /*p*/, socket_ref sr) ZMQ_NOTHROW
{
    return !(sr == nullptr);
}
#endif

inline bool operator==(socket_ref a, socket_ref b) ZMQ_NOTHROW
{
    return std::equal_to<void*>()(a.handle(), b.handle());
}
inline bool operator!=(socket_ref a, socket_ref b) ZMQ_NOTHROW
{
    return !(a == b);
}
inline bool operator<(socket_ref a, socket_ref b) ZMQ_NOTHROW
{
    return std::less<void*>()(a.handle(), b.handle());
}
inline bool operator>(socket_ref a, socket_ref b) ZMQ_NOTHROW
{
    return b < a;
}
inline bool operator<=(socket_ref a, socket_ref b) ZMQ_NOTHROW
{
    return !(a > b);
}
inline bool operator>=(socket_ref a, socket_ref b) ZMQ_NOTHROW
{
    return !(a < b);
}

} // namespace zmq

#ifdef ZMQ_CPP11
namespace std
{
template<>
struct hash<zmq::socket_ref>
{
    size_t operator()(zmq::socket_ref sr) const ZMQ_NOTHROW
    {
        return hash<void*>()(sr.handle());
    }
};
} // namespace std
#endif

namespace zmq
{

class socket_t : public detail::socket_base
{
    friend class monitor_t;

  public:
    socket_t() ZMQ_NOTHROW
      : detail::socket_base(ZMQ_NULLPTR)
      , ctxptr(ZMQ_NULLPTR)
    {
    }

    socket_t(context_t &context_, int type_)
        : detail::socket_base(zmq_socket(static_cast<void*>(context_), type_))
        , ctxptr(static_cast<void*>(context_))
    {
        if (_handle == ZMQ_NULLPTR)
            throw error_t();
    }

#ifdef ZMQ_CPP11
    socket_t(context_t &context_, socket_type type_)
        : socket_t(context_, static_cast<int>(type_))
    {
    }
#endif

#ifdef ZMQ_HAS_RVALUE_REFS
    socket_t(socket_t &&rhs) ZMQ_NOTHROW : detail::socket_base(rhs._handle), ctxptr(rhs.ctxptr)
    {
        rhs._handle = ZMQ_NULLPTR;
        rhs.ctxptr = ZMQ_NULLPTR;
    }
    socket_t &operator=(socket_t &&rhs) ZMQ_NOTHROW
    {
        close();
        std::swap(_handle, rhs._handle);
        return *this;
    }
#endif

    ~socket_t() ZMQ_NOTHROW { close(); }

    operator void *() ZMQ_NOTHROW { return _handle; }

    operator void const *() const ZMQ_NOTHROW { return _handle; }

    void close() ZMQ_NOTHROW
    {
        if (_handle == ZMQ_NULLPTR)
            // already closed
            return;
        int rc = zmq_close(_handle);
        ZMQ_ASSERT(rc == 0);
        _handle = ZMQ_NULLPTR;
    }

    void swap(socket_t &other) ZMQ_NOTHROW
    {
        std::swap(_handle, other._handle);
        std::swap(ctxptr, other.ctxptr);
    }

    operator socket_ref() ZMQ_NOTHROW
    {
        return socket_ref(from_handle, _handle);
    }

  private:
    void *ctxptr;

    socket_t(const socket_t &) ZMQ_DELETED_FUNCTION;
    void operator=(const socket_t &) ZMQ_DELETED_FUNCTION;

    // used by monitor_t
    socket_t(void *context_, int type_)
        : detail::socket_base(zmq_socket(context_, type_))
        , ctxptr(context_)
    {
        if (_handle == ZMQ_NULLPTR)
            throw error_t();
    }
};

inline void swap(socket_t &a, socket_t &b) ZMQ_NOTHROW {
    a.swap(b);
}

ZMQ_DEPRECATED("from 4.3.1, use proxy taking socket_t objects")
inline void proxy(void *frontend, void *backend, void *capture)
{
    int rc = zmq_proxy(frontend, backend, capture);
    if (rc != 0)
        throw error_t();
}

inline void
proxy(socket_ref frontend, socket_ref backend, socket_ref capture = socket_ref())
{
    int rc = zmq_proxy(frontend.handle(), backend.handle(), capture.handle());
    if (rc != 0)
        throw error_t();
}

#ifdef ZMQ_HAS_PROXY_STEERABLE
ZMQ_DEPRECATED("from 4.3.1, use proxy_steerable taking socket_t objects")
inline void
proxy_steerable(void *frontend, void *backend, void *capture, void *control)
{
    int rc = zmq_proxy_steerable(frontend, backend, capture, control);
    if (rc != 0)
        throw error_t();
}

inline void proxy_steerable(socket_ref frontend,
                            socket_ref backend,
                            socket_ref capture,
                            socket_ref control)
{
    int rc = zmq_proxy_steerable(frontend.handle(), backend.handle(),
                                 capture.handle(), control.handle());
    if (rc != 0)
        throw error_t();
}
#endif

class monitor_t
{
  public:
    monitor_t() : _socket(), _monitor_socket() {}

    virtual ~monitor_t()
    {
        close();
    }

#ifdef ZMQ_HAS_RVALUE_REFS
    monitor_t(monitor_t &&rhs) ZMQ_NOTHROW : _socket(), _monitor_socket()
    {
        std::swap(_socket, rhs._socket);
        std::swap(_monitor_socket, rhs._monitor_socket);
    }

    monitor_t &operator=(monitor_t &&rhs) ZMQ_NOTHROW
    {
        close();
        _socket = socket_ref();
        std::swap(_socket, rhs._socket);
        std::swap(_monitor_socket, rhs._monitor_socket);
        return *this;
    }
#endif


    void
    monitor(socket_t &socket, std::string const &addr, int events = ZMQ_EVENT_ALL)
    {
        monitor(socket, addr.c_str(), events);
    }

    void monitor(socket_t &socket, const char *addr_, int events = ZMQ_EVENT_ALL)
    {
        init(socket, addr_, events);
        while (true) {
            check_event(-1);
        }
    }

    void init(socket_t &socket, std::string const &addr, int events = ZMQ_EVENT_ALL)
    {
        init(socket, addr.c_str(), events);
    }

    void init(socket_t &socket, const char *addr_, int events = ZMQ_EVENT_ALL)
    {
        int rc = zmq_socket_monitor(socket.handle(), addr_, events);
        if (rc != 0)
            throw error_t();

        _socket = socket;
        _monitor_socket = socket_t(socket.ctxptr, ZMQ_PAIR);
        _monitor_socket.connect(addr_);

        on_monitor_started();
    }

    bool check_event(int timeout = 0)
    {
        assert(_monitor_socket);

        zmq_msg_t eventMsg;
        zmq_msg_init(&eventMsg);

        zmq::pollitem_t items[] = {
          {_monitor_socket.handle(), 0, ZMQ_POLLIN, 0},
        };

        zmq::poll(&items[0], 1, timeout);

        if (items[0].revents & ZMQ_POLLIN) {
            int rc = zmq_msg_recv(&eventMsg, _monitor_socket.handle(), 0);
            if (rc == -1 && zmq_errno() == ETERM)
                return false;
            assert(rc != -1);

        } else {
            zmq_msg_close(&eventMsg);
            return false;
        }

#if ZMQ_VERSION_MAJOR >= 4
        const char *data = static_cast<const char *>(zmq_msg_data(&eventMsg));
        zmq_event_t msgEvent;
        memcpy(&msgEvent.event, data, sizeof(uint16_t));
        data += sizeof(uint16_t);
        memcpy(&msgEvent.value, data, sizeof(int32_t));
        zmq_event_t *event = &msgEvent;
#else
        zmq_event_t *event = static_cast<zmq_event_t *>(zmq_msg_data(&eventMsg));
#endif

#ifdef ZMQ_NEW_MONITOR_EVENT_LAYOUT
        zmq_msg_t addrMsg;
        zmq_msg_init(&addrMsg);
        int rc = zmq_msg_recv(&addrMsg, _monitor_socket.handle(), 0);
        if (rc == -1 && zmq_errno() == ETERM) {
            zmq_msg_close(&eventMsg);
            return false;
        }

        assert(rc != -1);
        const char *str = static_cast<const char *>(zmq_msg_data(&addrMsg));
        std::string address(str, str + zmq_msg_size(&addrMsg));
        zmq_msg_close(&addrMsg);
#else
        // Bit of a hack, but all events in the zmq_event_t union have the same layout so this will work for all event types.
        std::string address = event->data.connected.addr;
#endif

#ifdef ZMQ_EVENT_MONITOR_STOPPED
        if (event->event == ZMQ_EVENT_MONITOR_STOPPED) {
            zmq_msg_close(&eventMsg);
            return false;
        }

#endif

        switch (event->event) {
            case ZMQ_EVENT_CONNECTED:
                on_event_connected(*event, address.c_str());
                break;
            case ZMQ_EVENT_CONNECT_DELAYED:
                on_event_connect_delayed(*event, address.c_str());
                break;
            case ZMQ_EVENT_CONNECT_RETRIED:
                on_event_connect_retried(*event, address.c_str());
                break;
            case ZMQ_EVENT_LISTENING:
                on_event_listening(*event, address.c_str());
                break;
            case ZMQ_EVENT_BIND_FAILED:
                on_event_bind_failed(*event, address.c_str());
                break;
            case ZMQ_EVENT_ACCEPTED:
                on_event_accepted(*event, address.c_str());
                break;
            case ZMQ_EVENT_ACCEPT_FAILED:
                on_event_accept_failed(*event, address.c_str());
                break;
            case ZMQ_EVENT_CLOSED:
                on_event_closed(*event, address.c_str());
                break;
            case ZMQ_EVENT_CLOSE_FAILED:
                on_event_close_failed(*event, address.c_str());
                break;
            case ZMQ_EVENT_DISCONNECTED:
                on_event_disconnected(*event, address.c_str());
                break;
#ifdef ZMQ_BUILD_DRAFT_API
#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 3)
            case ZMQ_EVENT_HANDSHAKE_FAILED_NO_DETAIL:
                on_event_handshake_failed_no_detail(*event, address.c_str());
                break;
            case ZMQ_EVENT_HANDSHAKE_FAILED_PROTOCOL:
                on_event_handshake_failed_protocol(*event, address.c_str());
                break;
            case ZMQ_EVENT_HANDSHAKE_FAILED_AUTH:
                on_event_handshake_failed_auth(*event, address.c_str());
                break;
            case ZMQ_EVENT_HANDSHAKE_SUCCEEDED:
                on_event_handshake_succeeded(*event, address.c_str());
                break;
#elif ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 1)
            case ZMQ_EVENT_HANDSHAKE_FAILED:
                on_event_handshake_failed(*event, address.c_str());
                break;
            case ZMQ_EVENT_HANDSHAKE_SUCCEED:
                on_event_handshake_succeed(*event, address.c_str());
                break;
#endif
#endif
            default:
                on_event_unknown(*event, address.c_str());
                break;
        }
        zmq_msg_close(&eventMsg);

        return true;
    }

#ifdef ZMQ_EVENT_MONITOR_STOPPED
    void abort()
    {
        if (_socket)
            zmq_socket_monitor(_socket.handle(), ZMQ_NULLPTR, 0);

        _socket = socket_ref();
    }
#endif
    virtual void on_monitor_started() {}
    virtual void on_event_connected(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_connect_delayed(const zmq_event_t &event_,
                                          const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_connect_retried(const zmq_event_t &event_,
                                          const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_listening(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_bind_failed(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_accepted(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_accept_failed(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_closed(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_close_failed(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_disconnected(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 3)
    virtual void on_event_handshake_failed_no_detail(const zmq_event_t &event_,
                                                     const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_handshake_failed_protocol(const zmq_event_t &event_,
                                                    const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_handshake_failed_auth(const zmq_event_t &event_,
                                                const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_handshake_succeeded(const zmq_event_t &event_,
                                              const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
#elif ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 1)
    virtual void on_event_handshake_failed(const zmq_event_t &event_,
                                           const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_handshake_succeed(const zmq_event_t &event_,
                                            const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
#endif
    virtual void on_event_unknown(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }

  private:
    monitor_t(const monitor_t &) ZMQ_DELETED_FUNCTION;
    void operator=(const monitor_t &) ZMQ_DELETED_FUNCTION;

    socket_ref _socket;
    socket_t _monitor_socket;

    void close() ZMQ_NOTHROW
    {
        if (_socket)
            zmq_socket_monitor(_socket.handle(), ZMQ_NULLPTR, 0);
        _monitor_socket.close();
    }
};

#if defined(ZMQ_BUILD_DRAFT_API) && defined(ZMQ_CPP11) && defined(ZMQ_HAVE_POLLER)

// polling events
enum class event_flags : short
{
    none = 0,
    pollin = ZMQ_POLLIN,
    pollout = ZMQ_POLLOUT,
    pollerr = ZMQ_POLLERR,
    pollpri = ZMQ_POLLPRI
};

constexpr event_flags operator|(event_flags a, event_flags b) noexcept
{
    return detail::enum_bit_or(a, b);
}
constexpr event_flags operator&(event_flags a, event_flags b) noexcept
{
    return detail::enum_bit_and(a, b);
}
constexpr event_flags operator^(event_flags a, event_flags b) noexcept
{
    return detail::enum_bit_xor(a, b);
}
constexpr event_flags operator~(event_flags a) noexcept
{
    return detail::enum_bit_not(a);
}

struct no_user_data;

// layout compatible with zmq_poller_event_t
template<class T = no_user_data>
struct poller_event
{
    socket_ref socket;
#ifdef _WIN32
    SOCKET fd;
#else
    int fd;
#endif
    T *user_data;
    event_flags events;
};

template<typename T = no_user_data> class poller_t
{
  public:
    using event_type = poller_event<T>;

    poller_t() : poller_ptr(zmq_poller_new())
    {
        if (!poller_ptr)
            throw error_t();
    }

    template<
      typename Dummy = void,
      typename =
        typename std::enable_if<!std::is_same<T, no_user_data>::value, Dummy>::type>
    void add(zmq::socket_ref socket, event_flags events, T *user_data)
    {
        add_impl(socket, events, user_data);
    }

    void add(zmq::socket_ref socket, event_flags events)
    {
        add_impl(socket, events, nullptr);
    }

    void remove(zmq::socket_ref socket)
    {
        if (0 != zmq_poller_remove(poller_ptr.get(), socket.handle())) {
            throw error_t();
        }
    }

    void modify(zmq::socket_ref socket, event_flags events)
    {
        if (0
            != zmq_poller_modify(poller_ptr.get(), socket.handle(),
                                 static_cast<short>(events))) {
            throw error_t();
        }
    }

    size_t wait_all(std::vector<event_type> &poller_events,
                    const std::chrono::milliseconds timeout)
    {
        int rc = zmq_poller_wait_all(
          poller_ptr.get(),
          reinterpret_cast<zmq_poller_event_t *>(poller_events.data()),
          static_cast<int>(poller_events.size()),
          static_cast<long>(timeout.count()));
        if (rc > 0)
            return static_cast<size_t>(rc);

#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 3)
        if (zmq_errno() == EAGAIN)
#else
        if (zmq_errno() == ETIMEDOUT)
#endif
            return 0;

        throw error_t();
    }

  private:
    struct destroy_poller_t
    {
        void operator()(void *ptr) noexcept
        {
            int rc = zmq_poller_destroy(&ptr);
            ZMQ_ASSERT(rc == 0);
        }
    };

    std::unique_ptr<void, destroy_poller_t> poller_ptr;

    void add_impl(zmq::socket_ref socket, event_flags events, T *user_data)
    {
        if (0
            != zmq_poller_add(poller_ptr.get(), socket.handle(),
                              user_data, static_cast<short>(events))) {
            throw error_t();
        }
    }
};
#endif //  defined(ZMQ_BUILD_DRAFT_API) && defined(ZMQ_CPP11) && defined(ZMQ_HAVE_POLLER)

inline std::ostream &operator<<(std::ostream &os, const message_t &msg)
{
    return os << msg.str();
}

} // namespace zmq

#endif // __ZMQ_HPP_INCLUDED__