summaryrefslogtreecommitdiffstats
path: root/vendor/github.com/lib/pq/conn.go
blob: fadb88e5eac7522a5a97125e4412f719c3a98266 (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
package pq

import (
	"bufio"
	"crypto/md5"
	"database/sql"
	"database/sql/driver"
	"encoding/binary"
	"errors"
	"fmt"
	"io"
	"net"
	"os"
	"os/user"
	"path"
	"path/filepath"
	"strconv"
	"strings"
	"time"
	"unicode"

	"github.com/lib/pq/oid"
)

// Common error types
var (
	ErrNotSupported              = errors.New("pq: Unsupported command")
	ErrInFailedTransaction       = errors.New("pq: Could not complete operation in a failed transaction")
	ErrSSLNotSupported           = errors.New("pq: SSL is not enabled on the server")
	ErrSSLKeyHasWorldPermissions = errors.New("pq: Private key file has group or world access. Permissions should be u=rw (0600) or less")
	ErrCouldNotDetectUsername    = errors.New("pq: Could not detect default username. Please provide one explicitly")

	errUnexpectedReady = errors.New("unexpected ReadyForQuery")
	errNoRowsAffected  = errors.New("no RowsAffected available after the empty statement")
	errNoLastInsertID  = errors.New("no LastInsertId available after the empty statement")
)

// Driver is the Postgres database driver.
type Driver struct{}

// Open opens a new connection to the database. name is a connection string.
// Most users should only use it through database/sql package from the standard
// library.
func (d *Driver) Open(name string) (driver.Conn, error) {
	return Open(name)
}

func init() {
	sql.Register("postgres", &Driver{})
}

type parameterStatus struct {
	// server version in the same format as server_version_num, or 0 if
	// unavailable
	serverVersion int

	// the current location based on the TimeZone value of the session, if
	// available
	currentLocation *time.Location
}

type transactionStatus byte

const (
	txnStatusIdle                transactionStatus = 'I'
	txnStatusIdleInTransaction   transactionStatus = 'T'
	txnStatusInFailedTransaction transactionStatus = 'E'
)

func (s transactionStatus) String() string {
	switch s {
	case txnStatusIdle:
		return "idle"
	case txnStatusIdleInTransaction:
		return "idle in transaction"
	case txnStatusInFailedTransaction:
		return "in a failed transaction"
	default:
		errorf("unknown transactionStatus %d", s)
	}

	panic("not reached")
}

// Dialer is the dialer interface. It can be used to obtain more control over
// how pq creates network connections.
type Dialer interface {
	Dial(network, address string) (net.Conn, error)
	DialTimeout(network, address string, timeout time.Duration) (net.Conn, error)
}

type defaultDialer struct{}

func (d defaultDialer) Dial(ntw, addr string) (net.Conn, error) {
	return net.Dial(ntw, addr)
}
func (d defaultDialer) DialTimeout(ntw, addr string, timeout time.Duration) (net.Conn, error) {
	return net.DialTimeout(ntw, addr, timeout)
}

type conn struct {
	c         net.Conn
	buf       *bufio.Reader
	namei     int
	scratch   [512]byte
	txnStatus transactionStatus
	txnFinish func()

	// Save connection arguments to use during CancelRequest.
	dialer Dialer
	opts   values

	// Cancellation key data for use with CancelRequest messages.
	processID int
	secretKey int

	parameterStatus parameterStatus

	saveMessageType   byte
	saveMessageBuffer []byte

	// If true, this connection is bad and all public-facing functions should
	// return ErrBadConn.
	bad bool

	// If set, this connection should never use the binary format when
	// receiving query results from prepared statements.  Only provided for
	// debugging.
	disablePreparedBinaryResult bool

	// Whether to always send []byte parameters over as binary.  Enables single
	// round-trip mode for non-prepared Query calls.
	binaryParameters bool

	// If true this connection is in the middle of a COPY
	inCopy bool
}

// Handle driver-side settings in parsed connection string.
func (cn *conn) handleDriverSettings(o values) (err error) {
	boolSetting := func(key string, val *bool) error {
		if value, ok := o[key]; ok {
			if value == "yes" {
				*val = true
			} else if value == "no" {
				*val = false
			} else {
				return fmt.Errorf("unrecognized value %q for %s", value, key)
			}
		}
		return nil
	}

	err = boolSetting("disable_prepared_binary_result", &cn.disablePreparedBinaryResult)
	if err != nil {
		return err
	}
	return boolSetting("binary_parameters", &cn.binaryParameters)
}

func (cn *conn) handlePgpass(o values) {
	// if a password was supplied, do not process .pgpass
	if _, ok := o["password"]; ok {
		return
	}
	filename := os.Getenv("PGPASSFILE")
	if filename == "" {
		// XXX this code doesn't work on Windows where the default filename is
		// XXX %APPDATA%\postgresql\pgpass.conf
		// Prefer $HOME over user.Current due to glibc bug: golang.org/issue/13470
		userHome := os.Getenv("HOME")
		if userHome == "" {
			user, err := user.Current()
			if err != nil {
				return
			}
			userHome = user.HomeDir
		}
		filename = filepath.Join(userHome, ".pgpass")
	}
	fileinfo, err := os.Stat(filename)
	if err != nil {
		return
	}
	mode := fileinfo.Mode()
	if mode&(0x77) != 0 {
		// XXX should warn about incorrect .pgpass permissions as psql does
		return
	}
	file, err := os.Open(filename)
	if err != nil {
		return
	}
	defer file.Close()
	scanner := bufio.NewScanner(io.Reader(file))
	hostname := o["host"]
	ntw, _ := network(o)
	port := o["port"]
	db := o["dbname"]
	username := o["user"]
	// From: https://github.com/tg/pgpass/blob/master/reader.go
	getFields := func(s string) []string {
		fs := make([]string, 0, 5)
		f := make([]rune, 0, len(s))

		var esc bool
		for _, c := range s {
			switch {
			case esc:
				f = append(f, c)
				esc = false
			case c == '\\':
				esc = true
			case c == ':':
				fs = append(fs, string(f))
				f = f[:0]
			default:
				f = append(f, c)
			}
		}
		return append(fs, string(f))
	}
	for scanner.Scan() {
		line := scanner.Text()
		if len(line) == 0 || line[0] == '#' {
			continue
		}
		split := getFields(line)
		if len(split) != 5 {
			continue
		}
		if (split[0] == "*" || split[0] == hostname || (split[0] == "localhost" && (hostname == "" || ntw == "unix"))) && (split[1] == "*" || split[1] == port) && (split[2] == "*" || split[2] == db) && (split[3] == "*" || split[3] == username) {
			o["password"] = split[4]
			return
		}
	}
}

func (cn *conn) writeBuf(b byte) *writeBuf {
	cn.scratch[0] = b
	return &writeBuf{
		buf: cn.scratch[:5],
		pos: 1,
	}
}

// Open opens a new connection to the database. name is a connection string.
// Most users should only use it through database/sql package from the standard
// library.
func Open(name string) (_ driver.Conn, err error) {
	return DialOpen(defaultDialer{}, name)
}

// DialOpen opens a new connection to the database using a dialer.
func DialOpen(d Dialer, name string) (_ driver.Conn, err error) {
	// Handle any panics during connection initialization.  Note that we
	// specifically do *not* want to use errRecover(), as that would turn any
	// connection errors into ErrBadConns, hiding the real error message from
	// the user.
	defer errRecoverNoErrBadConn(&err)

	o := make(values)

	// A number of defaults are applied here, in this order:
	//
	// * Very low precedence defaults applied in every situation
	// * Environment variables
	// * Explicitly passed connection information
	o["host"] = "localhost"
	o["port"] = "5432"
	// N.B.: Extra float digits should be set to 3, but that breaks
	// Postgres 8.4 and older, where the max is 2.
	o["extra_float_digits"] = "2"
	for k, v := range parseEnviron(os.Environ()) {
		o[k] = v
	}

	if strings.HasPrefix(name, "postgres://") || strings.HasPrefix(name, "postgresql://") {
		name, err = ParseURL(name)
		if err != nil {
			return nil, err
		}
	}

	if err := parseOpts(name, o); err != nil {
		return nil, err
	}

	// Use the "fallback" application name if necessary
	if fallback, ok := o["fallback_application_name"]; ok {
		if _, ok := o["application_name"]; !ok {
			o["application_name"] = fallback
		}
	}

	// We can't work with any client_encoding other than UTF-8 currently.
	// However, we have historically allowed the user to set it to UTF-8
	// explicitly, and there's no reason to break such programs, so allow that.
	// Note that the "options" setting could also set client_encoding, but
	// parsing its value is not worth it.  Instead, we always explicitly send
	// client_encoding as a separate run-time parameter, which should override
	// anything set in options.
	if enc, ok := o["client_encoding"]; ok && !isUTF8(enc) {
		return nil, errors.New("client_encoding must be absent or 'UTF8'")
	}
	o["client_encoding"] = "UTF8"
	// DateStyle needs a similar treatment.
	if datestyle, ok := o["datestyle"]; ok {
		if datestyle != "ISO, MDY" {
			panic(fmt.Sprintf("setting datestyle must be absent or %v; got %v",
				"ISO, MDY", datestyle))
		}
	} else {
		o["datestyle"] = "ISO, MDY"
	}

	// If a user is not provided by any other means, the last
	// resort is to use the current operating system provided user
	// name.
	if _, ok := o["user"]; !ok {
		u, err := userCurrent()
		if err != nil {
			return nil, err
		}
		o["user"] = u
	}

	cn := &conn{
		opts:   o,
		dialer: d,
	}
	err = cn.handleDriverSettings(o)
	if err != nil {
		return nil, err
	}
	cn.handlePgpass(o)

	cn.c, err = dial(d, o)
	if err != nil {
		return nil, err
	}
	cn.ssl(o)
	cn.buf = bufio.NewReader(cn.c)
	cn.startup(o)

	// reset the deadline, in case one was set (see dial)
	if timeout, ok := o["connect_timeout"]; ok && timeout != "0" {
		err = cn.c.SetDeadline(time.Time{})
	}
	return cn, err
}

func dial(d Dialer, o values) (net.Conn, error) {
	ntw, addr := network(o)
	// SSL is not necessary or supported over UNIX domain sockets
	if ntw == "unix" {
		o["sslmode"] = "disable"
	}

	// Zero or not specified means wait indefinitely.
	if timeout, ok := o["connect_timeout"]; ok && timeout != "0" {
		seconds, err := strconv.ParseInt(timeout, 10, 0)
		if err != nil {
			return nil, fmt.Errorf("invalid value for parameter connect_timeout: %s", err)
		}
		duration := time.Duration(seconds) * time.Second
		// connect_timeout should apply to the entire connection establishment
		// procedure, so we both use a timeout for the TCP connection
		// establishment and set a deadline for doing the initial handshake.
		// The deadline is then reset after startup() is done.
		deadline := time.Now().Add(duration)
		conn, err := d.DialTimeout(ntw, addr, duration)
		if err != nil {
			return nil, err
		}
		err = conn.SetDeadline(deadline)
		return conn, err
	}
	return d.Dial(ntw, addr)
}

func network(o values) (string, string) {
	host := o["host"]

	if strings.HasPrefix(host, "/") {
		sockPath := path.Join(host, ".s.PGSQL."+o["port"])
		return "unix", sockPath
	}

	return "tcp", net.JoinHostPort(host, o["port"])
}

type values map[string]string

// scanner implements a tokenizer for libpq-style option strings.
type scanner struct {
	s []rune
	i int
}

// newScanner returns a new scanner initialized with the option string s.
func newScanner(s string) *scanner {
	return &scanner{[]rune(s), 0}
}

// Next returns the next rune.
// It returns 0, false if the end of the text has been reached.
func (s *scanner) Next() (rune, bool) {
	if s.i >= len(s.s) {
		return 0, false
	}
	r := s.s[s.i]
	s.i++
	return r, true
}

// SkipSpaces returns the next non-whitespace rune.
// It returns 0, false if the end of the text has been reached.
func (s *scanner) SkipSpaces() (rune, bool) {
	r, ok := s.Next()
	for unicode.IsSpace(r) && ok {
		r, ok = s.Next()
	}
	return r, ok
}

// parseOpts parses the options from name and adds them to the values.
//
// The parsing code is based on conninfo_parse from libpq's fe-connect.c
func parseOpts(name string, o values) error {
	s := newScanner(name)

	for {
		var (
			keyRunes, valRunes []rune
			r                  rune
			ok                 bool
		)

		if r, ok = s.SkipSpaces(); !ok {
			break
		}

		// Scan the key
		for !unicode.IsSpace(r) && r != '=' {
			keyRunes = append(keyRunes, r)
			if r, ok = s.Next(); !ok {
				break
			}
		}

		// Skip any whitespace if we're not at the = yet
		if r != '=' {
			r, ok = s.SkipSpaces()
		}

		// The current character should be =
		if r != '=' || !ok {
			return fmt.Errorf(`missing "=" after %q in connection info string"`, string(keyRunes))
		}

		// Skip any whitespace after the =
		if r, ok = s.SkipSpaces(); !ok {
			// If we reach the end here, the last value is just an empty string as per libpq.
			o[string(keyRunes)] = ""
			break
		}

		if r != '\'' {
			for !unicode.IsSpace(r) {
				if r == '\\' {
					if r, ok = s.Next(); !ok {
						return fmt.Errorf(`missing character after backslash`)
					}
				}
				valRunes = append(valRunes, r)

				if r, ok = s.Next(); !ok {
					break
				}
			}
		} else {
		quote:
			for {
				if r, ok = s.Next(); !ok {
					return fmt.Errorf(`unterminated quoted string literal in connection string`)
				}
				switch r {
				case '\'':
					break quote
				case '\\':
					r, _ = s.Next()
					fallthrough
				default:
					valRunes = append(valRunes, r)
				}
			}
		}

		o[string(keyRunes)] = string(valRunes)
	}

	return nil
}

func (cn *conn) isInTransaction() bool {
	return cn.txnStatus == txnStatusIdleInTransaction ||
		cn.txnStatus == txnStatusInFailedTransaction
}

func (cn *conn) checkIsInTransaction(intxn bool) {
	if cn.isInTransaction() != intxn {
		cn.bad = true
		errorf("unexpected transaction status %v", cn.txnStatus)
	}
}

func (cn *conn) Begin() (_ driver.Tx, err error) {
	return cn.begin("")
}

func (cn *conn) begin(mode string) (_ driver.Tx, err error) {
	if cn.bad {
		return nil, driver.ErrBadConn
	}
	defer cn.errRecover(&err)

	cn.checkIsInTransaction(false)
	_, commandTag, err := cn.simpleExec("BEGIN" + mode)
	if err != nil {
		return nil, err
	}
	if commandTag != "BEGIN" {
		cn.bad = true
		return nil, fmt.Errorf("unexpected command tag %s", commandTag)
	}
	if cn.txnStatus != txnStatusIdleInTransaction {
		cn.bad = true
		return nil, fmt.Errorf("unexpected transaction status %v", cn.txnStatus)
	}
	return cn, nil
}

func (cn *conn) closeTxn() {
	if finish := cn.txnFinish; finish != nil {
		finish()
	}
}

func (cn *conn) Commit() (err error) {
	defer cn.closeTxn()
	if cn.bad {
		return driver.ErrBadConn
	}
	defer cn.errRecover(&err)

	cn.checkIsInTransaction(true)
	// We don't want the client to think that everything is okay if it tries
	// to commit a failed transaction.  However, no matter what we return,
	// database/sql will release this connection back into the free connection
	// pool so we have to abort the current transaction here.  Note that you
	// would get the same behaviour if you issued a COMMIT in a failed
	// transaction, so it's also the least surprising thing to do here.
	if cn.txnStatus == txnStatusInFailedTransaction {
		if err := cn.Rollback(); err != nil {
			return err
		}
		return ErrInFailedTransaction
	}

	_, commandTag, err := cn.simpleExec("COMMIT")
	if err != nil {
		if cn.isInTransaction() {
			cn.bad = true
		}
		return err
	}
	if commandTag != "COMMIT" {
		cn.bad = true
		return fmt.Errorf("unexpected command tag %s", commandTag)
	}
	cn.checkIsInTransaction(false)
	return nil
}

func (cn *conn) Rollback() (err error) {
	defer cn.closeTxn()
	if cn.bad {
		return driver.ErrBadConn
	}
	defer cn.errRecover(&err)

	cn.checkIsInTransaction(true)
	_, commandTag, err := cn.simpleExec("ROLLBACK")
	if err != nil {
		if cn.isInTransaction() {
			cn.bad = true
		}
		return err
	}
	if commandTag != "ROLLBACK" {
		return fmt.Errorf("unexpected command tag %s", commandTag)
	}
	cn.checkIsInTransaction(false)
	return nil
}

func (cn *conn) gname() string {
	cn.namei++
	return strconv.FormatInt(int64(cn.namei), 10)
}

func (cn *conn) simpleExec(q string) (res driver.Result, commandTag string, err error) {
	b := cn.writeBuf('Q')
	b.string(q)
	cn.send(b)

	for {
		t, r := cn.recv1()
		switch t {
		case 'C':
			res, commandTag = cn.parseComplete(r.string())
		case 'Z':
			cn.processReadyForQuery(r)
			if res == nil && err == nil {
				err = errUnexpectedReady
			}
			// done
			return
		case 'E':
			err = parseError(r)
		case 'I':
			res = emptyRows
		case 'T', 'D':
			// ignore any results
		default:
			cn.bad = true
			errorf("unknown response for simple query: %q", t)
		}
	}
}

func (cn *conn) simpleQuery(q string) (res *rows, err error) {
	defer cn.errRecover(&err)

	b := cn.writeBuf('Q')
	b.string(q)
	cn.send(b)

	for {
		t, r := cn.recv1()
		switch t {
		case 'C', 'I':
			// We allow queries which don't return any results through Query as
			// well as Exec.  We still have to give database/sql a rows object
			// the user can close, though, to avoid connections from being
			// leaked.  A "rows" with done=true works fine for that purpose.
			if err != nil {
				cn.bad = true
				errorf("unexpected message %q in simple query execution", t)
			}
			if res == nil {
				res = &rows{
					cn: cn,
				}
			}
			// Set the result and tag to the last command complete if there wasn't a
			// query already run. Although queries usually return from here and cede
			// control to Next, a query with zero results does not.
			if t == 'C' && res.colNames == nil {
				res.result, res.tag = cn.parseComplete(r.string())
			}
			res.done = true
		case 'Z':
			cn.processReadyForQuery(r)
			// done
			return
		case 'E':
			res = nil
			err = parseError(r)
		case 'D':
			if res == nil {
				cn.bad = true
				errorf("unexpected DataRow in simple query execution")
			}
			// the query didn't fail; kick off to Next
			cn.saveMessage(t, r)
			return
		case 'T':
			// res might be non-nil here if we received a previous
			// CommandComplete, but that's fine; just overwrite it
			res = &rows{cn: cn}
			res.colNames, res.colFmts, res.colTyps = parsePortalRowDescribe(r)

			// To work around a bug in QueryRow in Go 1.2 and earlier, wait
			// until the first DataRow has been received.
		default:
			cn.bad = true
			errorf("unknown response for simple query: %q", t)
		}
	}
}

type noRows struct{}

var emptyRows noRows

var _ driver.Result = noRows{}

func (noRows) LastInsertId() (int64, error) {
	return 0, errNoLastInsertID
}

func (noRows) RowsAffected() (int64, error) {
	return 0, errNoRowsAffected
}

// Decides which column formats to use for a prepared statement.  The input is
// an array of type oids, one element per result column.
func decideColumnFormats(colTyps []fieldDesc, forceText bool) (colFmts []format, colFmtData []byte) {
	if len(colTyps) == 0 {
		return nil, colFmtDataAllText
	}

	colFmts = make([]format, len(colTyps))
	if forceText {
		return colFmts, colFmtDataAllText
	}

	allBinary := true
	allText := true
	for i, t := range colTyps {
		switch t.OID {
		// This is the list of types to use binary mode for when receiving them
		// through a prepared statement.  If a type appears in this list, it
		// must also be implemented in binaryDecode in encode.go.
		case oid.T_bytea:
			fallthrough
		case oid.T_int8:
			fallthrough
		case oid.T_int4:
			fallthrough
		case oid.T_int2:
			fallthrough
		case oid.T_uuid:
			colFmts[i] = formatBinary
			allText = false

		default:
			allBinary = false
		}
	}

	if allBinary {
		return colFmts, colFmtDataAllBinary
	} else if allText {
		return colFmts, colFmtDataAllText
	} else {
		colFmtData = make([]byte, 2+len(colFmts)*2)
		binary.BigEndian.PutUint16(colFmtData, uint16(len(colFmts)))
		for i, v := range colFmts {
			binary.BigEndian.PutUint16(colFmtData[2+i*2:], uint16(v))
		}
		return colFmts, colFmtData
	}
}

func (cn *conn) prepareTo(q, stmtName string) *stmt {
	st := &stmt{cn: cn, name: stmtName}

	b := cn.writeBuf('P')
	b.string(st.name)
	b.string(q)
	b.int16(0)

	b.next('D')
	b.byte('S')
	b.string(st.name)

	b.next('S')
	cn.send(b)

	cn.readParseResponse()
	st.paramTyps, st.colNames, st.colTyps = cn.readStatementDescribeResponse()
	st.colFmts, st.colFmtData = decideColumnFormats(st.colTyps, cn.disablePreparedBinaryResult)
	cn.readReadyForQuery()
	return st
}

func (cn *conn) Prepare(q string) (_ driver.Stmt, err error) {
	if cn.bad {
		return nil, driver.ErrBadConn
	}
	defer cn.errRecover(&err)

	if len(q) >= 4 && strings.EqualFold(q[:4], "COPY") {
		s, err := cn.prepareCopyIn(q)
		if err == nil {
			cn.inCopy = true
		}
		return s, err
	}
	return cn.prepareTo(q, cn.gname()), nil
}

func (cn *conn) Close() (err error) {
	// Skip cn.bad return here because we always want to close a connection.
	defer cn.errRecover(&err)

	// Ensure that cn.c.Close is always run. Since error handling is done with
	// panics and cn.errRecover, the Close must be in a defer.
	defer func() {
		cerr := cn.c.Close()
		if err == nil {
			err = cerr
		}
	}()

	// Don't go through send(); ListenerConn relies on us not scribbling on the
	// scratch buffer of this connection.
	return cn.sendSimpleMessage('X')
}

// Implement the "Queryer" interface
func (cn *conn) Query(query string, args []driver.Value) (driver.Rows, error) {
	return cn.query(query, args)
}

func (cn *conn) query(query string, args []driver.Value) (_ *rows, err error) {
	if cn.bad {
		return nil, driver.ErrBadConn
	}
	if cn.inCopy {
		return nil, errCopyInProgress
	}
	defer cn.errRecover(&err)

	// Check to see if we can use the "simpleQuery" interface, which is
	// *much* faster than going through prepare/exec
	if len(args) == 0 {
		return cn.simpleQuery(query)
	}

	if cn.binaryParameters {
		cn.sendBinaryModeQuery(query, args)

		cn.readParseResponse()
		cn.readBindResponse()
		rows := &rows{cn: cn}
		rows.colNames, rows.colFmts, rows.colTyps = cn.readPortalDescribeResponse()
		cn.postExecuteWorkaround()
		return rows, nil
	}
	st := cn.prepareTo(query, "")
	st.exec(args)
	return &rows{
		cn:       cn,
		colNames: st.colNames,
		colTyps:  st.colTyps,
		colFmts:  st.colFmts,
	}, nil
}

// Implement the optional "Execer" interface for one-shot queries
func (cn *conn) Exec(query string, args []driver.Value) (res driver.Result, err error) {
	if cn.bad {
		return nil, driver.ErrBadConn
	}
	defer cn.errRecover(&err)

	// Check to see if we can use the "simpleExec" interface, which is
	// *much* faster than going through prepare/exec
	if len(args) == 0 {
		// ignore commandTag, our caller doesn't care
		r, _, err := cn.simpleExec(query)
		return r, err
	}

	if cn.binaryParameters {
		cn.sendBinaryModeQuery(query, args)

		cn.readParseResponse()
		cn.readBindResponse()
		cn.readPortalDescribeResponse()
		cn.postExecuteWorkaround()
		res, _, err = cn.readExecuteResponse("Execute")
		return res, err
	}
	// Use the unnamed statement to defer planning until bind
	// time, or else value-based selectivity estimates cannot be
	// used.
	st := cn.prepareTo(query, "")
	r, err := st.Exec(args)
	if err != nil {
		panic(err)
	}
	return r, err
}

func (cn *conn) send(m *writeBuf) {
	_, err := cn.c.Write(m.wrap())
	if err != nil {
		panic(err)
	}
}

func (cn *conn) sendStartupPacket(m *writeBuf) error {
	_, err := cn.c.Write((m.wrap())[1:])
	return err
}

// Send a message of type typ to the server on the other end of cn.  The
// message should have no payload.  This method does not use the scratch
// buffer.
func (cn *conn) sendSimpleMessage(typ byte) (err error) {
	_, err = cn.c.Write([]byte{typ, '\x00', '\x00', '\x00', '\x04'})
	return err
}

// saveMessage memorizes a message and its buffer in the conn struct.
// recvMessage will then return these values on the next call to it.  This
// method is useful in cases where you have to see what the next message is
// going to be (e.g. to see whether it's an error or not) but you can't handle
// the message yourself.
func (cn *conn) saveMessage(typ byte, buf *readBuf) {
	if cn.saveMessageType != 0 {
		cn.bad = true
		errorf("unexpected saveMessageType %d", cn.saveMessageType)
	}
	cn.saveMessageType = typ
	cn.saveMessageBuffer = *buf
}

// recvMessage receives any message from the backend, or returns an error if
// a problem occurred while reading the message.
func (cn *conn) recvMessage(r *readBuf) (byte, error) {
	// workaround for a QueryRow bug, see exec
	if cn.saveMessageType != 0 {
		t := cn.saveMessageType
		*r = cn.saveMessageBuffer
		cn.saveMessageType = 0
		cn.saveMessageBuffer = nil
		return t, nil
	}

	x := cn.scratch[:5]
	_, err := io.ReadFull(cn.buf, x)
	if err != nil {
		return 0, err
	}

	// read the type and length of the message that follows
	t := x[0]
	n := int(binary.BigEndian.Uint32(x[1:])) - 4
	var y []byte
	if n <= len(cn.scratch) {
		y = cn.scratch[:n]
	} else {
		y = make([]byte, n)
	}
	_, err = io.ReadFull(cn.buf, y)
	if err != nil {
		return 0, err
	}
	*r = y
	return t, nil
}

// recv receives a message from the backend, but if an error happened while
// reading the message or the received message was an ErrorResponse, it panics.
// NoticeResponses are ignored.  This function should generally be used only
// during the startup sequence.
func (cn *conn) recv() (t byte, r *readBuf) {
	for {
		var err error
		r = &readBuf{}
		t, err = cn.recvMessage(r)
		if err != nil {
			panic(err)
		}

		switch t {
		case 'E':
			panic(parseError(r))
		case 'N':
			// ignore
		default:
			return
		}
	}
}

// recv1Buf is exactly equivalent to recv1, except it uses a buffer supplied by
// the caller to avoid an allocation.
func (cn *conn) recv1Buf(r *readBuf) byte {
	for {
		t, err := cn.recvMessage(r)
		if err != nil {
			panic(err)
		}

		switch t {
		case 'A', 'N':
			// ignore
		case 'S':
			cn.processParameterStatus(r)
		default:
			return t
		}
	}
}

// recv1 receives a message from the backend, panicking if an error occurs
// while attempting to read it.  All asynchronous messages are ignored, with
// the exception of ErrorResponse.
func (cn *conn) recv1() (t byte, r *readBuf) {
	r = &readBuf{}
	t = cn.recv1Buf(r)
	return t, r
}

func (cn *conn) ssl(o values) {
	upgrade := ssl(o)
	if upgrade == nil {
		// Nothing to do
		return
	}

	w := cn.writeBuf(0)
	w.int32(80877103)
	if err := cn.sendStartupPacket(w); err != nil {
		panic(err)
	}

	b := cn.scratch[:1]
	_, err := io.ReadFull(cn.c, b)
	if err != nil {
		panic(err)
	}

	if b[0] != 'S' {
		panic(ErrSSLNotSupported)
	}

	cn.c = upgrade(cn.c)
}

// isDriverSetting returns true iff a setting is purely for configuring the
// driver's options and should not be sent to the server in the connection
// startup packet.
func isDriverSetting(key string) bool {
	switch key {
	case "host", "port":
		return true
	case "password":
		return true
	case "sslmode", "sslcert", "sslkey", "sslrootcert":
		return true
	case "fallback_application_name":
		return true
	case "connect_timeout":
		return true
	case "disable_prepared_binary_result":
		return true
	case "binary_parameters":
		return true

	default:
		return false
	}
}

func (cn *conn) startup(o values) {
	w := cn.writeBuf(0)
	w.int32(196608)
	// Send the backend the name of the database we want to connect to, and the
	// user we want to connect as.  Additionally, we send over any run-time
	// parameters potentially included in the connection string.  If the server
	// doesn't recognize any of them, it will reply with an error.
	for k, v := range o {
		if isDriverSetting(k) {
			// skip options which can't be run-time parameters
			continue
		}
		// The protocol requires us to supply the database name as "database"
		// instead of "dbname".
		if k == "dbname" {
			k = "database"
		}
		w.string(k)
		w.string(v)
	}
	w.string("")
	if err := cn.sendStartupPacket(w); err != nil {
		panic(err)
	}

	for {
		t, r := cn.recv()
		switch t {
		case 'K':
			cn.processBackendKeyData(r)
		case 'S':
			cn.processParameterStatus(r)
		case 'R':
			cn.auth(r, o)
		case 'Z':
			cn.processReadyForQuery(r)
			return
		default:
			errorf("unknown response for startup: %q", t)
		}
	}
}

func (cn *conn) auth(r *readBuf, o values) {
	switch code := r.int32(); code {
	case 0:
		// OK
	case 3:
		w := cn.writeBuf('p')
		w.string(o["password"])
		cn.send(w)

		t, r := cn.recv()
		if t != 'R' {
			errorf("unexpected password response: %q", t)
		}

		if r.int32() != 0 {
			errorf("unexpected authentication response: %q", t)
		}
	case 5:
		s := string(r.next(4))
		w := cn.writeBuf('p')
		w.string("md5" + md5s(md5s(o["password"]+o["user"])+s))
		cn.send(w)

		t, r := cn.recv()
		if t != 'R' {
			errorf("unexpected password response: %q", t)
		}

		if r.int32() != 0 {
			errorf("unexpected authentication response: %q", t)
		}
	default:
		errorf("unknown authentication response: %d", code)
	}
}

type format int

const formatText format = 0
const formatBinary format = 1

// One result-column format code with the value 1 (i.e. all binary).
var colFmtDataAllBinary = []byte{0, 1, 0, 1}

// No result-column format codes (i.e. all text).
var colFmtDataAllText = []byte{0, 0}

type stmt struct {
	cn         *conn
	name       string
	colNames   []string
	colFmts    []format
	colFmtData []byte
	colTyps    []fieldDesc
	paramTyps  []oid.Oid
	closed     bool
}

func (st *stmt) Close() (err error) {
	if st.closed {
		return nil
	}
	if st.cn.bad {
		return driver.ErrBadConn
	}
	defer st.cn.errRecover(&err)

	w := st.cn.writeBuf('C')
	w.byte('S')
	w.string(st.name)
	st.cn.send(w)

	st.cn.send(st.cn.writeBuf('S'))

	t, _ := st.cn.recv1()
	if t != '3' {
		st.cn.bad = true
		errorf("unexpected close response: %q", t)
	}
	st.closed = true

	t, r := st.cn.recv1()
	if t != 'Z' {
		st.cn.bad = true
		errorf("expected ready for query, but got: %q", t)
	}
	st.cn.processReadyForQuery(r)

	return nil
}

func (st *stmt) Query(v []driver.Value) (r driver.Rows, err error) {
	if st.cn.bad {
		return nil, driver.ErrBadConn
	}
	defer st.cn.errRecover(&err)

	st.exec(v)
	return &rows{
		cn:       st.cn,
		colNames: st.colNames,
		colTyps:  st.colTyps,
		colFmts:  st.colFmts,
	}, nil
}

func (st *stmt) Exec(v []driver.Value) (res driver.Result, err error) {
	if st.cn.bad {
		return nil, driver.ErrBadConn
	}
	defer st.cn.errRecover(&err)

	st.exec(v)
	res, _, err = st.cn.readExecuteResponse("simple query")
	return res, err
}

func (st *stmt) exec(v []driver.Value) {
	if len(v) >= 65536 {
		errorf("got %d parameters but PostgreSQL only supports 65535 parameters", len(v))
	}
	if len(v) != len(st.paramTyps) {
		errorf("got %d parameters but the statement requires %d", len(v), len(st.paramTyps))
	}

	cn := st.cn
	w := cn.writeBuf('B')
	w.byte(0) // unnamed portal
	w.string(st.name)

	if cn.binaryParameters {
		cn.sendBinaryParameters(w, v)
	} else {
		w.int16(0)
		w.int16(len(v))
		for i, x := range v {
			if x == nil {
				w.int32(-1)
			} else {
				b := encode(&cn.parameterStatus, x, st.paramTyps[i])
				w.int32(len(b))
				w.bytes(b)
			}
		}
	}
	w.bytes(st.colFmtData)

	w.next('E')
	w.byte(0)
	w.int32(0)

	w.next('S')
	cn.send(w)

	cn.readBindResponse()
	cn.postExecuteWorkaround()

}

func (st *stmt) NumInput() int {
	return len(st.paramTyps)
}

// parseComplete parses the "command tag" from a CommandComplete message, and
// returns the number of rows affected (if applicable) and a string
// identifying only the command that was executed, e.g. "ALTER TABLE".  If the
// command tag could not be parsed, parseComplete panics.
func (cn *conn) parseComplete(commandTag string) (driver.Result, string) {
	commandsWithAffectedRows := []string{
		"SELECT ",
		// INSERT is handled below
		"UPDATE ",
		"DELETE ",
		"FETCH ",
		"MOVE ",
		"COPY ",
	}

	var affectedRows *string
	for _, tag := range commandsWithAffectedRows {
		if strings.HasPrefix(commandTag, tag) {
			t := commandTag[len(tag):]
			affectedRows = &t
			commandTag = tag[:len(tag)-1]
			break
		}
	}
	// INSERT also includes the oid of the inserted row in its command tag.
	// Oids in user tables are deprecated, and the oid is only returned when
	// exactly one row is inserted, so it's unlikely to be of value to any
	// real-world application and we can ignore it.
	if affectedRows == nil && strings.HasPrefix(commandTag, "INSERT ") {
		parts := strings.Split(commandTag, " ")
		if len(parts) != 3 {
			cn.bad = true
			errorf("unexpected INSERT command tag %s", commandTag)
		}
		affectedRows = &parts[len(parts)-1]
		commandTag = "INSERT"
	}
	// There should be no affected rows attached to the tag, just return it
	if affectedRows == nil {
		return driver.RowsAffected(0), commandTag
	}
	n, err := strconv.ParseInt(*affectedRows, 10, 64)
	if err != nil {
		cn.bad = true
		errorf("could not parse commandTag: %s", err)
	}
	return driver.RowsAffected(n), commandTag
}

type rows struct {
	cn       *conn
	finish   func()
	colNames []string
	colTyps  []fieldDesc
	colFmts  []format
	done     bool
	rb       readBuf
	result   driver.Result
	tag      string
}

func (rs *rows) Close() error {
	if finish := rs.finish; finish != nil {
		defer finish()
	}
	// no need to look at cn.bad as Next() will
	for {
		err := rs.Next(nil)
		switch err {
		case nil:
		case io.EOF:
			// rs.Next can return io.EOF on both 'Z' (ready for query) and 'T' (row
			// description, used with HasNextResultSet). We need to fetch messages until
			// we hit a 'Z', which is done by waiting for done to be set.
			if rs.done {
				return nil
			}
		default:
			return err
		}
	}
}

func (rs *rows) Columns() []string {
	return rs.colNames
}

func (rs *rows) Result() driver.Result {
	if rs.result == nil {
		return emptyRows
	}
	return rs.result
}

func (rs *rows) Tag() string {
	return rs.tag
}

func (rs *rows) Next(dest []driver.Value) (err error) {
	if rs.done {
		return io.EOF
	}

	conn := rs.cn
	if conn.bad {
		return driver.ErrBadConn
	}
	defer conn.errRecover(&err)

	for {
		t := conn.recv1Buf(&rs.rb)
		switch t {
		case 'E':
			err = parseError(&rs.rb)
		case 'C', 'I':
			if t == 'C' {
				rs.result, rs.tag = conn.parseComplete(rs.rb.string())
			}
			continue
		case 'Z':
			conn.processReadyForQuery(&rs.rb)
			rs.done = true
			if err != nil {
				return err
			}
			return io.EOF
		case 'D':
			n := rs.rb.int16()
			if err != nil {
				conn.bad = true
				errorf("unexpected DataRow after error %s", err)
			}
			if n < len(dest) {
				dest = dest[:n]
			}
			for i := range dest {
				l := rs.rb.int32()
				if l == -1 {
					dest[i] = nil
					continue
				}
				dest[i] = decode(&conn.parameterStatus, rs.rb.next(l), rs.colTyps[i].OID, rs.colFmts[i])
			}
			return
		case 'T':
			rs.colNames, rs.colFmts, rs.colTyps = parsePortalRowDescribe(&rs.rb)
			return io.EOF
		default:
			errorf("unexpected message after execute: %q", t)
		}
	}
}

func (rs *rows) HasNextResultSet() bool {
	return !rs.done
}

func (rs *rows) NextResultSet() error {
	return nil
}

// QuoteIdentifier quotes an "identifier" (e.g. a table or a column name) to be
// used as part of an SQL statement.  For example:
//
//    tblname := "my_table"
//    data := "my_data"
//    quoted := pq.QuoteIdentifier(tblname)
//    err := db.Exec(fmt.Sprintf("INSERT INTO %s VALUES ($1)", quoted), data)
//
// Any double quotes in name will be escaped.  The quoted identifier will be
// case sensitive when used in a query.  If the input string contains a zero
// byte, the result will be truncated immediately before it.
func QuoteIdentifier(name string) string {
	end := strings.IndexRune(name, 0)
	if end > -1 {
		name = name[:end]
	}
	return `"` + strings.Replace(name, `"`, `""`, -1) + `"`
}

func md5s(s string) string {
	h := md5.New()
	h.Write([]byte(s))
	return fmt.Sprintf("%x", h.Sum(nil))
}

func (cn *conn) sendBinaryParameters(b *writeBuf, args []driver.Value) {
	// Do one pass over the parameters to see if we're going to send any of
	// them over in binary.  If we are, create a paramFormats array at the
	// same time.
	var paramFormats []int
	for i, x := range args {
		_, ok := x.([]byte)
		if ok {
			if paramFormats == nil {
				paramFormats = make([]int, len(args))
			}
			paramFormats[i] = 1
		}
	}
	if paramFormats == nil {
		b.int16(0)
	} else {
		b.int16(len(paramFormats))
		for _, x := range paramFormats {
			b.int16(x)
		}
	}

	b.int16(len(args))
	for _, x := range args {
		if x == nil {
			b.int32(-1)
		} else {
			datum := binaryEncode(&cn.parameterStatus, x)
			b.int32(len(datum))
			b.bytes(datum)
		}
	}
}

func (cn *conn) sendBinaryModeQuery(query string, args []driver.Value) {
	if len(args) >= 65536 {
		errorf("got %d parameters but PostgreSQL only supports 65535 parameters", len(args))
	}

	b := cn.writeBuf('P')
	b.byte(0) // unnamed statement
	b.string(query)
	b.int16(0)

	b.next('B')
	b.int16(0) // unnamed portal and statement
	cn.sendBinaryParameters(b, args)
	b.bytes(colFmtDataAllText)

	b.next('D')
	b.byte('P')
	b.byte(0) // unnamed portal

	b.next('E')
	b.byte(0)
	b.int32(0)

	b.next('S')
	cn.send(b)
}

func (cn *conn) processParameterStatus(r *readBuf) {
	var err error

	param := r.string()
	switch param {
	case "server_version":
		var major1 int
		var major2 int
		var minor int
		_, err = fmt.Sscanf(r.string(), "%d.%d.%d", &major1, &major2, &minor)
		if err == nil {
			cn.parameterStatus.serverVersion = major1*10000 + major2*100 + minor
		}

	case "TimeZone":
		cn.parameterStatus.currentLocation, err = time.LoadLocation(r.string())
		if err != nil {
			cn.parameterStatus.currentLocation = nil
		}

	default:
		// ignore
	}
}

func (cn *conn) processReadyForQuery(r *readBuf) {
	cn.txnStatus = transactionStatus(r.byte())
}

func (cn *conn) readReadyForQuery() {
	t, r := cn.recv1()
	switch t {
	case 'Z':
		cn.processReadyForQuery(r)
		return
	default:
		cn.bad = true
		errorf("unexpected message %q; expected ReadyForQuery", t)
	}
}

func (cn *conn) processBackendKeyData(r *readBuf) {
	cn.processID = r.int32()
	cn.secretKey = r.int32()
}

func (cn *conn) readParseResponse() {
	t, r := cn.recv1()
	switch t {
	case '1':
		return
	case 'E':
		err := parseError(r)
		cn.readReadyForQuery()
		panic(err)
	default:
		cn.bad = true
		errorf("unexpected Parse response %q", t)
	}
}

func (cn *conn) readStatementDescribeResponse() (paramTyps []oid.Oid, colNames []string, colTyps []fieldDesc) {
	for {
		t, r := cn.recv1()
		switch t {
		case 't':
			nparams := r.int16()
			paramTyps = make([]oid.Oid, nparams)
			for i := range paramTyps {
				paramTyps[i] = r.oid()
			}
		case 'n':
			return paramTyps, nil, nil
		case 'T':
			colNames, colTyps = parseStatementRowDescribe(r)
			return paramTyps, colNames, colTyps
		case 'E':
			err := parseError(r)
			cn.readReadyForQuery()
			panic(err)
		default:
			cn.bad = true
			errorf("unexpected Describe statement response %q", t)
		}
	}
}

func (cn *conn) readPortalDescribeResponse() (colNames []string, colFmts []format, colTyps []fieldDesc) {
	t, r := cn.recv1()
	switch t {
	case 'T':
		return parsePortalRowDescribe(r)
	case 'n':
		return nil, nil, nil
	case 'E':
		err := parseError(r)
		cn.readReadyForQuery()
		panic(err)
	default:
		cn.bad = true
		errorf("unexpected Describe response %q", t)
	}
	panic("not reached")
}

func (cn *conn) readBindResponse() {
	t, r := cn.recv1()
	switch t {
	case '2':
		return
	case 'E':
		err := parseError(r)
		cn.readReadyForQuery()
		panic(err)
	default:
		cn.bad = true
		errorf("unexpected Bind response %q", t)
	}
}

func (cn *conn) postExecuteWorkaround() {
	// Work around a bug in sql.DB.QueryRow: in Go 1.2 and earlier it ignores
	// any errors from rows.Next, which masks errors that happened during the
	// execution of the query.  To avoid the problem in common cases, we wait
	// here for one more message from the database.  If it's not an error the
	// query will likely succeed (or perhaps has already, if it's a
	// CommandComplete), so we push the message into the conn struct; recv1
	// will return it as the next message for rows.Next or rows.Close.
	// However, if it's an error, we wait until ReadyForQuery and then return
	// the error to our caller.
	for {
		t, r := cn.recv1()
		switch t {
		case 'E':
			err := parseError(r)
			cn.readReadyForQuery()
			panic(err)
		case 'C', 'D', 'I':
			// the query didn't fail, but we can't process this message
			cn.saveMessage(t, r)
			return
		default:
			cn.bad = true
			errorf("unexpected message during extended query execution: %q", t)
		}
	}
}

// Only for Exec(), since we ignore the returned data
func (cn *conn) readExecuteResponse(protocolState string) (res driver.Result, commandTag string, err error) {
	for {
		t, r := cn.recv1()
		switch t {
		case 'C':
			if err != nil {
				cn.bad = true
				errorf("unexpected CommandComplete after error %s", err)
			}
			res, commandTag = cn.parseComplete(r.string())
		case 'Z':
			cn.processReadyForQuery(r)
			if res == nil && err == nil {
				err = errUnexpectedReady
			}
			return res, commandTag, err
		case 'E':
			err = parseError(r)
		case 'T', 'D', 'I':
			if err != nil {
				cn.bad = true
				errorf("unexpected %q after error %s", t, err)
			}
			if t == 'I' {
				res = emptyRows
			}
			// ignore any results
		default:
			cn.bad = true
			errorf("unknown %s response: %q", protocolState, t)
		}
	}
}

func parseStatementRowDescribe(r *readBuf) (colNames []string, colTyps []fieldDesc) {
	n := r.int16()
	colNames = make([]string, n)
	colTyps = make([]fieldDesc, n)
	for i := range colNames {
		colNames[i] = r.string()
		r.next(6)
		colTyps[i].OID = r.oid()
		colTyps[i].Len = r.int16()
		colTyps[i].Mod = r.int32()
		// format code not known when describing a statement; always 0
		r.next(2)
	}
	return
}

func parsePortalRowDescribe(r *readBuf) (colNames []string, colFmts []format, colTyps []fieldDesc) {
	n := r.int16()
	colNames = make([]string, n)
	colFmts = make([]format, n)
	colTyps = make([]fieldDesc, n)
	for i := range colNames {
		colNames[i] = r.string()
		r.next(6)
		colTyps[i].OID = r.oid()
		colTyps[i].Len = r.int16()
		colTyps[i].Mod = r.int32()
		colFmts[i] = format(r.int16())
	}
	return
}

// parseEnviron tries to mimic some of libpq's environment handling
//
// To ease testing, it does not directly reference os.Environ, but is
// designed to accept its output.
//
// Environment-set connection information is intended to have a higher
// precedence than a library default but lower than any explicitly
// passed information (such as in the URL or connection string).
func parseEnviron(env []string) (out map[string]string) {
	out = make(map[string]string)

	for _, v := range env {
		parts := strings.SplitN(v, "=", 2)

		accrue := func(keyname string) {
			out[keyname] = parts[1]
		}
		unsupported := func() {
			panic(fmt.Sprintf("setting %v not supported", parts[0]))
		}

		// The order of these is the same as is seen in the
		// PostgreSQL 9.1 manual. Unsupported but well-defined
		// keys cause a panic; these should be unset prior to
		// execution. Options which pq expects to be set to a
		// certain value are allowed, but must be set to that
		// value if present (they can, of course, be absent).
		switch parts[0] {
		case "PGHOST":
			accrue("host")
		case "PGHOSTADDR":
			unsupported()
		case "PGPORT":
			accrue("port")
		case "PGDATABASE":
			accrue("dbname")
		case "PGUSER":
			accrue("user")
		case "PGPASSWORD":
			accrue("password")
		case "PGSERVICE", "PGSERVICEFILE", "PGREALM":
			unsupported()
		case "PGOPTIONS":
			accrue("options")
		case "PGAPPNAME":
			accrue("application_name")
		case "PGSSLMODE":
			accrue("sslmode")
		case "PGSSLCERT":
			accrue("sslcert")
		case "PGSSLKEY":
			accrue("sslkey")
		case "PGSSLROOTCERT":
			accrue("sslrootcert")
		case "PGREQUIRESSL", "PGSSLCRL":
			unsupported()
		case "PGREQUIREPEER":
			unsupported()
		case "PGKRBSRVNAME", "PGGSSLIB":
			unsupported()
		case "PGCONNECT_TIMEOUT":
			accrue("connect_timeout")
		case "PGCLIENTENCODING":
			accrue("client_encoding")
		case "PGDATESTYLE":
			accrue("datestyle")
		case "PGTZ":
			accrue("timezone")
		case "PGGEQO":
			accrue("geqo")
		case "PGSYSCONFDIR", "PGLOCALEDIR":
			unsupported()
		}
	}

	return out
}

// isUTF8 returns whether name is a fuzzy variation of the string "UTF-8".
func isUTF8(name string) bool {
	// Recognize all sorts of silly things as "UTF-8", like Postgres does
	s := strings.Map(alnumLowerASCII, name)
	return s == "utf8" || s == "unicode"
}

func alnumLowerASCII(ch rune) rune {
	if 'A' <= ch && ch <= 'Z' {
		return ch + ('a' - 'A')
	}
	if 'a' <= ch && ch <= 'z' || '0' <= ch && ch <= '9' {
		return ch
	}
	return -1 // discard
}