about summary refs log tree commit diff
path: root/src/libstore/local-store.cc
blob: 950e6e7608f11055d8ec556cc8da518983683d28 (plain) (blame)
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
#include "config.h"
#include "local-store.hh"
#include "globals.hh"
#include "archive.hh"
#include "pathlocks.hh"
#include "worker-protocol.hh"
#include "derivations.hh"
#include "immutable.hh"
    
#include <iostream>
#include <algorithm>

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <utime.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <time.h>

#include <sqlite3.h>


namespace nix {


MakeError(SQLiteError, Error);
MakeError(SQLiteBusy, SQLiteError);


static void throwSQLiteError(sqlite3 * db, const format & f)
    __attribute__ ((noreturn));

static void throwSQLiteError(sqlite3 * db, const format & f)
{
    int err = sqlite3_errcode(db);
    if (err == SQLITE_BUSY) {
        printMsg(lvlError, "warning: SQLite database is busy");
        /* Sleep for a while since retrying the transaction right away
           is likely to fail again. */
#if HAVE_NANOSLEEP
        struct timespec t;
        t.tv_sec = 0;
        t.tv_nsec = 100 * 1000 * 1000; /* 0.1s */
        nanosleep(&t, 0);
#else
        sleep(1);
#endif
        throw SQLiteBusy(format("%1%: %2%") % f.str() % sqlite3_errmsg(db));
    }
    else
        throw SQLiteError(format("%1%: %2%") % f.str() % sqlite3_errmsg(db));
}


SQLite::~SQLite()
{
    try {
        if (db && sqlite3_close(db) != SQLITE_OK)
            throwSQLiteError(db, "closing database");
    } catch (...) {
        ignoreException();
    }
}


void SQLiteStmt::create(sqlite3 * db, const string & s)
{
    checkInterrupt();
    assert(!stmt);
    if (sqlite3_prepare_v2(db, s.c_str(), -1, &stmt, 0) != SQLITE_OK)
        throwSQLiteError(db, "creating statement");
    this->db = db;
}


void SQLiteStmt::reset()
{
    assert(stmt);
    /* Note: sqlite3_reset() returns the error code for the most
       recent call to sqlite3_step().  So ignore it. */
    sqlite3_reset(stmt);
    curArg = 1;
}


SQLiteStmt::~SQLiteStmt()
{
    try {
        if (stmt && sqlite3_finalize(stmt) != SQLITE_OK)
            throwSQLiteError(db, "finalizing statement");
    } catch (...) {
        ignoreException();
    }
}


void SQLiteStmt::bind(const string & value)
{
    if (sqlite3_bind_text(stmt, curArg++, value.c_str(), -1, SQLITE_TRANSIENT) != SQLITE_OK)
        throwSQLiteError(db, "binding argument");
}


void SQLiteStmt::bind(int value)
{
    if (sqlite3_bind_int(stmt, curArg++, value) != SQLITE_OK)
        throwSQLiteError(db, "binding argument");
}


void SQLiteStmt::bind64(long long value)
{
    if (sqlite3_bind_int64(stmt, curArg++, value) != SQLITE_OK)
        throwSQLiteError(db, "binding argument");
}


void SQLiteStmt::bind()
{
    if (sqlite3_bind_null(stmt, curArg++) != SQLITE_OK)
        throwSQLiteError(db, "binding argument");
}


/* Helper class to ensure that prepared statements are reset when
   leaving the scope that uses them.  Unfinished prepared statements
   prevent transactions from being aborted, and can cause locks to be
   kept when they should be released. */
struct SQLiteStmtUse
{
    SQLiteStmt & stmt;
    SQLiteStmtUse(SQLiteStmt & stmt) : stmt(stmt)
    {
        stmt.reset();
    }
    ~SQLiteStmtUse()
    {
        try {
            stmt.reset();
        } catch (...) {
            ignoreException();
        }
    }
};


struct SQLiteTxn 
{
    bool active;
    sqlite3 * db;
    
    SQLiteTxn(sqlite3 * db) : active(false) {
        this->db = db;
        if (sqlite3_exec(db, "begin;", 0, 0, 0) != SQLITE_OK)
            throwSQLiteError(db, "starting transaction");
        active = true;
    }

    void commit() 
    {
        if (sqlite3_exec(db, "commit;", 0, 0, 0) != SQLITE_OK)
            throwSQLiteError(db, "committing transaction");
        active = false;
    }
    
    ~SQLiteTxn() 
    {
        try {
            if (active && sqlite3_exec(db, "rollback;", 0, 0, 0) != SQLITE_OK)
                throwSQLiteError(db, "aborting transaction");
        } catch (...) {
            ignoreException();
        }
    }
};


void checkStoreNotSymlink()
{
    if (getEnv("NIX_IGNORE_SYMLINK_STORE") == "1") return;
    Path path = nixStore;
    struct stat st;
    while (path != "/") {
        if (lstat(path.c_str(), &st))
            throw SysError(format("getting status of `%1%'") % path);
        if (S_ISLNK(st.st_mode))
            throw Error(format(
                "the path `%1%' is a symlink; "
                "this is not allowed for the Nix store and its parent directories")
                % path);
        path = dirOf(path);
    }
}


LocalStore::LocalStore()
{
    substitutablePathsLoaded = false;
    
    schemaPath = nixDBPath + "/schema";
    
    if (readOnlyMode) {
        openDB(false);
        return;
    }

    /* Create missing state directories if they don't already exist. */
    createDirs(nixStore);
    Path profilesDir = nixStateDir + "/profiles";
    createDirs(nixStateDir + "/profiles");
    createDirs(nixStateDir + "/temproots");
    createDirs(nixDBPath);
    Path gcRootsDir = nixStateDir + "/gcroots";
    if (!pathExists(gcRootsDir)) {
        createDirs(gcRootsDir);
        if (symlink(profilesDir.c_str(), (gcRootsDir + "/profiles").c_str()) == -1)
            throw SysError(format("creating symlink to `%1%'") % profilesDir);
    }
  
    checkStoreNotSymlink();

    /* Acquire the big fat lock in shared mode to make sure that no
       schema upgrade is in progress. */
    try {
        Path globalLockPath = nixDBPath + "/big-lock";
        globalLock = openLockFile(globalLockPath.c_str(), true);
    } catch (SysError & e) {
        if (e.errNo != EACCES) throw;
        readOnlyMode = true;
        openDB(false);
        return;
    }
    
    if (!lockFile(globalLock, ltRead, false)) {
        printMsg(lvlError, "waiting for the big Nix store lock...");
        lockFile(globalLock, ltRead, true);
    }

    /* Check the current database schema and if necessary do an
       upgrade.  */
    int curSchema = getSchema();
    if (curSchema > nixSchemaVersion)
        throw Error(format("current Nix store schema is version %1%, but I only support %2%")
            % curSchema % nixSchemaVersion);
    
    else if (curSchema == 0) { /* new store */
        curSchema = nixSchemaVersion;
        openDB(true);
        writeFile(schemaPath, (format("%1%") % nixSchemaVersion).str());
    }
    
    else if (curSchema < nixSchemaVersion) {
        if (curSchema < 5)
            throw Error(
                "Your Nix store has a database in Berkeley DB format,\n"
                "which is no longer supported. To convert to the new format,\n"
                "please upgrade Nix to version 0.12 first.");
        
        if (!lockFile(globalLock, ltWrite, false)) {
            printMsg(lvlError, "waiting for exclusive access to the Nix store...");
            lockFile(globalLock, ltWrite, true);
        }

        /* Get the schema version again, because another process may
           have performed the upgrade already. */
        curSchema = getSchema();

        if (curSchema < 6) upgradeStore6();

        writeFile(schemaPath, (format("%1%") % nixSchemaVersion).str());

        lockFile(globalLock, ltRead, true);
    }
    
    else openDB(false);
}


LocalStore::~LocalStore()
{
    try {
        foreach (RunningSubstituters::iterator, i, runningSubstituters) {
            i->second.to.close();
            i->second.from.close();
            i->second.pid.wait(true);
        }
    } catch (...) {
        ignoreException();
    }
}


int LocalStore::getSchema()
{
    int curSchema = 0;
    if (pathExists(schemaPath)) {
        string s = readFile(schemaPath);
        if (!string2Int(s, curSchema))
            throw Error(format("`%1%' is corrupt") % schemaPath);
    }
    return curSchema;
}


void LocalStore::openDB(bool create)
{
    /* Open the Nix database. */
    if (sqlite3_open_v2((nixDBPath + "/db.sqlite").c_str(), &db.db,
            SQLITE_OPEN_READWRITE | (create ? SQLITE_OPEN_CREATE : 0), 0) != SQLITE_OK)
        throw Error("cannot open SQLite database");

    if (sqlite3_busy_timeout(db, 60 * 60 * 1000) != SQLITE_OK)
        throwSQLiteError(db, "setting timeout");

    if (sqlite3_exec(db, "pragma foreign_keys = 1;", 0, 0, 0) != SQLITE_OK)
        throwSQLiteError(db, "enabling foreign keys");

    /* !!! check whether sqlite has been built with foreign key
       support */
    
    /* Whether SQLite should fsync().  "Normal" synchronous mode
       should be safe enough.  If the user asks for it, don't sync at
       all.  This can cause database corruption if the system
       crashes. */
    string syncMode = queryBoolSetting("fsync-metadata", true) ? "normal" : "off";
    if (sqlite3_exec(db, ("pragma synchronous = " + syncMode + ";").c_str(), 0, 0, 0) != SQLITE_OK)
        throwSQLiteError(db, "setting synchronous mode");

    /* Set the SQLite journal mode.  WAL mode is fastest, so it's the
       default. */
    string mode = queryBoolSetting("use-sqlite-wal", true) ? "wal" : "truncate";
    string prevMode;
    {
        SQLiteStmt stmt;
        stmt.create(db, "pragma main.journal_mode;");
        if (sqlite3_step(stmt) != SQLITE_ROW)
            throwSQLiteError(db, "querying journal mode");
        prevMode = string((const char *) sqlite3_column_text(stmt, 0));
    }
    if (prevMode != mode &&
        sqlite3_exec(db, ("pragma main.journal_mode = " + mode + ";").c_str(), 0, 0, 0) != SQLITE_OK)
        throwSQLiteError(db, "setting journal mode");

    /* Increase the auto-checkpoint interval to 8192 pages.  This
       seems enough to ensure that instantiating the NixOS system
       derivation is done in a single fsync(). */
    if (mode == "wal" && sqlite3_exec(db, "pragma wal_autocheckpoint = 8192;", 0, 0, 0) != SQLITE_OK)
        throwSQLiteError(db, "setting autocheckpoint interval");
    
    /* Initialise the database schema, if necessary. */
    if (create) {
#include "schema.sql.hh"
        if (sqlite3_exec(db, (const char *) schema, 0, 0, 0) != SQLITE_OK)
            throwSQLiteError(db, "initialising database schema");
    }

    /* Prepare SQL statements. */
    stmtRegisterValidPath.create(db,
        "insert into ValidPaths (path, hash, registrationTime, deriver, narSize) values (?, ?, ?, ?, ?);");
    stmtUpdatePathInfo.create(db,
        "update ValidPaths set narSize = ?, hash = ? where path = ?;");
    stmtAddReference.create(db,
        "insert or replace into Refs (referrer, reference) values (?, ?);");
    stmtQueryPathInfo.create(db,
        "select id, hash, registrationTime, deriver, narSize from ValidPaths where path = ?;");
    stmtQueryReferences.create(db,
        "select path from Refs join ValidPaths on reference = id where referrer = ?;");
    stmtQueryReferrers.create(db,
        "select path from Refs join ValidPaths on referrer = id where reference = (select id from ValidPaths where path = ?);");
    stmtInvalidatePath.create(db,
        "delete from ValidPaths where path = ?;");
    stmtRegisterFailedPath.create(db,
        "insert into FailedPaths (path, time) values (?, ?);");
    stmtHasPathFailed.create(db,
        "select time from FailedPaths where path = ?;");
    stmtQueryFailedPaths.create(db,
        "select path from FailedPaths;");
    // If the path is a derivation, then clear its outputs.
    stmtClearFailedPath.create(db,
        "delete from FailedPaths where ?1 = '*' or path = ?1 "
        "or path in (select d.path from DerivationOutputs d join ValidPaths v on d.drv = v.id where v.path = ?1);");
    stmtAddDerivationOutput.create(db,
        "insert or replace into DerivationOutputs (drv, id, path) values (?, ?, ?);");
    stmtQueryValidDerivers.create(db,
        "select v.id, v.path from DerivationOutputs d join ValidPaths v on d.drv = v.id where d.path = ?;");
    stmtQueryDerivationOutputs.create(db,
        "select id, path from DerivationOutputs where drv = ?;");
}


const time_t mtimeStore = 1; /* 1 second into the epoch */


void canonicalisePathMetaData(const Path & path, bool recurse)
{
    checkInterrupt();

    struct stat st;
    if (lstat(path.c_str(), &st))
	throw SysError(format("getting attributes of path `%1%'") % path);

    /* Really make sure that the path is of a supported type.  This
       has already been checked in dumpPath(). */
    assert(S_ISREG(st.st_mode) || S_ISDIR(st.st_mode) || S_ISLNK(st.st_mode));

    /* Change ownership to the current uid.  If it's a symlink, use
       lchown if available, otherwise don't bother.  Wrong ownership
       of a symlink doesn't matter, since the owning user can't change
       the symlink and can't delete it because the directory is not
       writable.  The only exception is top-level paths in the Nix
       store (since that directory is group-writable for the Nix build
       users group); we check for this case below. */
    if (st.st_uid != geteuid()) {
#if HAVE_LCHOWN
        if (lchown(path.c_str(), geteuid(), (gid_t) -1) == -1)
#else
        if (!S_ISLNK(st.st_mode) &&
            chown(path.c_str(), geteuid(), (gid_t) -1) == -1)
#endif
            throw SysError(format("changing owner of `%1%' to %2%")
                % path % geteuid());
    }
    
    if (!S_ISLNK(st.st_mode)) {

        /* Mask out all type related bits. */
        mode_t mode = st.st_mode & ~S_IFMT;
        
        if (mode != 0444 && mode != 0555) {
            mode = (st.st_mode & S_IFMT)
                 | 0444
                 | (st.st_mode & S_IXUSR ? 0111 : 0);
            if (chmod(path.c_str(), mode) == -1)
                throw SysError(format("changing mode of `%1%' to %2$o") % path % mode);
        }

        if (st.st_mtime != mtimeStore) {
            struct utimbuf utimbuf;
            utimbuf.actime = st.st_atime;
            utimbuf.modtime = mtimeStore;
            if (utime(path.c_str(), &utimbuf) == -1) 
                throw SysError(format("changing modification time of `%1%'") % path);
        }

    }

    if (recurse && S_ISDIR(st.st_mode)) {
        Strings names = readDirectory(path);
	foreach (Strings::iterator, i, names)
	    canonicalisePathMetaData(path + "/" + *i, true);
    }

    makeImmutable(path);
}


void canonicalisePathMetaData(const Path & path)
{
    canonicalisePathMetaData(path, true);

    /* On platforms that don't have lchown(), the top-level path can't
       be a symlink, since we can't change its ownership. */
    struct stat st;
    if (lstat(path.c_str(), &st))
	throw SysError(format("getting attributes of path `%1%'") % path);

    if (st.st_uid != geteuid()) {
        assert(S_ISLNK(st.st_mode));
        throw Error(format("wrong ownership of top-level store path `%1%'") % path);
    }
}


void LocalStore::checkDerivationOutputs(const Path & drvPath, const Derivation & drv)
{
    string drvName = storePathToName(drvPath);
    assert(isDerivation(drvName));
    drvName = string(drvName, 0, drvName.size() - drvExtension.size());
        
    if (isFixedOutputDrv(drv)) {
        DerivationOutputs::const_iterator out = drv.outputs.find("out");
        if (out == drv.outputs.end())
            throw Error(format("derivation `%1%' does not have an output named `out'") % drvPath);

        bool recursive; HashType ht; Hash h;
        out->second.parseHashInfo(recursive, ht, h);
        Path outPath = makeFixedOutputPath(recursive, ht, h, drvName);

        StringPairs::const_iterator j = drv.env.find("out");
        if (out->second.path != outPath || j == drv.env.end() || j->second != outPath)
            throw Error(format("derivation `%1%' has incorrect output `%2%', should be `%3%'")
                % drvPath % out->second.path % outPath);
    }

    else {
        Derivation drvCopy(drv);
        foreach (DerivationOutputs::iterator, i, drvCopy.outputs) {
            i->second.path = "";
            drvCopy.env[i->first] = "";
        }

        Hash h = hashDerivationModulo(*this, drvCopy);
        
        foreach (DerivationOutputs::const_iterator, i, drv.outputs) {
            Path outPath = makeOutputPath(i->first, h, drvName);
            StringPairs::const_iterator j = drv.env.find(i->first);
            if (i->second.path != outPath || j == drv.env.end() || j->second != outPath)
                throw Error(format("derivation `%1%' has incorrect output `%2%', should be `%3%'")
                    % drvPath % i->second.path % outPath);
        }
    }
}


unsigned long long LocalStore::addValidPath(const ValidPathInfo & info, bool checkOutputs)
{
    SQLiteStmtUse use(stmtRegisterValidPath);
    stmtRegisterValidPath.bind(info.path);
    stmtRegisterValidPath.bind("sha256:" + printHash(info.hash));
    stmtRegisterValidPath.bind(info.registrationTime == 0 ? time(0) : info.registrationTime);
    if (info.deriver != "")
        stmtRegisterValidPath.bind(info.deriver);
    else
        stmtRegisterValidPath.bind(); // null
    if (info.narSize != 0)
        stmtRegisterValidPath.bind64(info.narSize);
    else
        stmtRegisterValidPath.bind(); // null
    if (sqlite3_step(stmtRegisterValidPath) != SQLITE_DONE)
        throwSQLiteError(db, format("registering valid path `%1%' in database") % info.path);
    unsigned long long id = sqlite3_last_insert_rowid(db);

    /* If this is a derivation, then store the derivation outputs in
       the database.  This is useful for the garbage collector: it can
       efficiently query whether a path is an output of some
       derivation. */
    if (isDerivation(info.path)) {
        Derivation drv = parseDerivation(readFile(info.path));
        
        /* Verify that the output paths in the derivation are correct
           (i.e., follow the scheme for computing output paths from
           derivations).  Note that if this throws an error, then the
           DB transaction is rolled back, so the path validity
           registration above is undone. */
        if (checkOutputs) checkDerivationOutputs(info.path, drv);
        
        foreach (DerivationOutputs::iterator, i, drv.outputs) {
            SQLiteStmtUse use(stmtAddDerivationOutput);
            stmtAddDerivationOutput.bind(id);
            stmtAddDerivationOutput.bind(i->first);
            stmtAddDerivationOutput.bind(i->second.path);
            if (sqlite3_step(stmtAddDerivationOutput) != SQLITE_DONE)
                throwSQLiteError(db, format("adding derivation output for `%1%' in database") % info.path);
        }
    }

    return id;
}


void LocalStore::addReference(unsigned long long referrer, unsigned long long reference)
{
    SQLiteStmtUse use(stmtAddReference);
    stmtAddReference.bind(referrer);
    stmtAddReference.bind(reference);
    if (sqlite3_step(stmtAddReference) != SQLITE_DONE)
        throwSQLiteError(db, "adding reference to database");
}


void LocalStore::registerFailedPath(const Path & path)
{
    if (hasPathFailed(path)) return;
    SQLiteStmtUse use(stmtRegisterFailedPath);
    stmtRegisterFailedPath.bind(path);
    stmtRegisterFailedPath.bind(time(0));
    if (sqlite3_step(stmtRegisterFailedPath) != SQLITE_DONE)
        throwSQLiteError(db, format("registering failed path `%1%'") % path);
}


bool LocalStore::hasPathFailed(const Path & path)
{
    SQLiteStmtUse use(stmtHasPathFailed);
    stmtHasPathFailed.bind(path);
    int res = sqlite3_step(stmtHasPathFailed);
    if (res != SQLITE_DONE && res != SQLITE_ROW)
        throwSQLiteError(db, "querying whether path failed");
    return res == SQLITE_ROW;
}


PathSet LocalStore::queryFailedPaths()
{
    SQLiteStmtUse use(stmtQueryFailedPaths);

    PathSet res;
    int r;
    while ((r = sqlite3_step(stmtQueryFailedPaths)) == SQLITE_ROW) {
        const char * s = (const char *) sqlite3_column_text(stmtQueryFailedPaths, 0);
        assert(s);
        res.insert(s);
    }

    if (r != SQLITE_DONE)
        throwSQLiteError(db, "error querying failed paths");

    return res;
}


void LocalStore::clearFailedPaths(const PathSet & paths)
{
    SQLiteTxn txn(db);

    foreach (PathSet::const_iterator, i, paths) {
        SQLiteStmtUse use(stmtClearFailedPath);
        stmtClearFailedPath.bind(*i);
        if (sqlite3_step(stmtClearFailedPath) != SQLITE_DONE)
            throwSQLiteError(db, format("clearing failed path `%1%' in database") % *i);
    }

    txn.commit();
}


Hash parseHashField(const Path & path, const string & s)
{
    string::size_type colon = s.find(':');
    if (colon == string::npos)
        throw Error(format("corrupt hash `%1%' in valid-path entry for `%2%'")
            % s % path);
    HashType ht = parseHashType(string(s, 0, colon));
    if (ht == htUnknown)
        throw Error(format("unknown hash type `%1%' in valid-path entry for `%2%'")
            % string(s, 0, colon) % path);
    return parseHash(ht, string(s, colon + 1));
}


ValidPathInfo LocalStore::queryPathInfo(const Path & path)
{
    ValidPathInfo info;
    info.path = path;

    assertStorePath(path);

    /* Get the path info. */
    SQLiteStmtUse use1(stmtQueryPathInfo);

    stmtQueryPathInfo.bind(path);
    
    int r = sqlite3_step(stmtQueryPathInfo);
    if (r == SQLITE_DONE) throw Error(format("path `%1%' is not valid") % path);
    if (r != SQLITE_ROW) throwSQLiteError(db, "querying path in database");

    info.id = sqlite3_column_int(stmtQueryPathInfo, 0);

    const char * s = (const char *) sqlite3_column_text(stmtQueryPathInfo, 1);
    assert(s);
    info.hash = parseHashField(path, s);
    
    info.registrationTime = sqlite3_column_int(stmtQueryPathInfo, 2);

    s = (const char *) sqlite3_column_text(stmtQueryPathInfo, 3);
    if (s) info.deriver = s;

    /* Note that narSize = NULL yields 0. */
    info.narSize = sqlite3_column_int64(stmtQueryPathInfo, 4);

    /* Get the references. */
    SQLiteStmtUse use2(stmtQueryReferences);

    stmtQueryReferences.bind(info.id);

    while ((r = sqlite3_step(stmtQueryReferences)) == SQLITE_ROW) {
        s = (const char *) sqlite3_column_text(stmtQueryReferences, 0);
        assert(s);
        info.references.insert(s);
    }

    if (r != SQLITE_DONE)
        throwSQLiteError(db, format("error getting references of `%1%'") % path);

    return info;
}


/* Update path info in the database.  Currently only updates the
   narSize field. */
void LocalStore::updatePathInfo(const ValidPathInfo & info)
{
    SQLiteStmtUse use(stmtUpdatePathInfo);
    if (info.narSize != 0)
        stmtUpdatePathInfo.bind64(info.narSize);
    else
        stmtUpdatePathInfo.bind(); // null
    stmtUpdatePathInfo.bind("sha256:" + printHash(info.hash));
    stmtUpdatePathInfo.bind(info.path);
    if (sqlite3_step(stmtUpdatePathInfo) != SQLITE_DONE)
        throwSQLiteError(db, format("updating info of path `%1%' in database") % info.path);
}


unsigned long long LocalStore::queryValidPathId(const Path & path)
{
    SQLiteStmtUse use(stmtQueryPathInfo);
    stmtQueryPathInfo.bind(path);
    int res = sqlite3_step(stmtQueryPathInfo);
    if (res == SQLITE_ROW) return sqlite3_column_int(stmtQueryPathInfo, 0);
    if (res == SQLITE_DONE) throw Error(format("path `%1%' is not valid") % path);
    throwSQLiteError(db, "querying path in database");
}


bool LocalStore::isValidPath(const Path & path)
{
    SQLiteStmtUse use(stmtQueryPathInfo);
    stmtQueryPathInfo.bind(path);
    int res = sqlite3_step(stmtQueryPathInfo);
    if (res != SQLITE_DONE && res != SQLITE_ROW)
        throwSQLiteError(db, "querying path in database");
    return res == SQLITE_ROW;
}


PathSet LocalStore::queryValidPaths()
{
    SQLiteStmt stmt;
    stmt.create(db, "select path from ValidPaths");
    
    PathSet res;
    
    int r;
    while ((r = sqlite3_step(stmt)) == SQLITE_ROW) {
        const char * s = (const char *) sqlite3_column_text(stmt, 0);
        assert(s);
        res.insert(s);
    }

    if (r != SQLITE_DONE)
        throwSQLiteError(db, "error getting valid paths");

    return res;
}


void LocalStore::queryReferences(const Path & path,
    PathSet & references)
{
    ValidPathInfo info = queryPathInfo(path);
    references.insert(info.references.begin(), info.references.end());
}


void LocalStore::queryReferrers(const Path & path, PathSet & referrers)
{
    assertStorePath(path);

    SQLiteStmtUse use(stmtQueryReferrers);

    stmtQueryReferrers.bind(path);

    int r;
    while ((r = sqlite3_step(stmtQueryReferrers)) == SQLITE_ROW) {
        const char * s = (const char *) sqlite3_column_text(stmtQueryReferrers, 0);
        assert(s);
        referrers.insert(s);
    }

    if (r != SQLITE_DONE)
        throwSQLiteError(db, format("error getting references of `%1%'") % path);
}


Path LocalStore::queryDeriver(const Path & path)
{
    return queryPathInfo(path).deriver;
}


PathSet LocalStore::queryValidDerivers(const Path & path)
{
    assertStorePath(path);

    SQLiteStmtUse use(stmtQueryValidDerivers);
    stmtQueryValidDerivers.bind(path);

    PathSet derivers;
    int r;
    while ((r = sqlite3_step(stmtQueryValidDerivers)) == SQLITE_ROW) {
        const char * s = (const char *) sqlite3_column_text(stmtQueryValidDerivers, 1);
        assert(s);
        derivers.insert(s);
    }
    
    if (r != SQLITE_DONE)
        throwSQLiteError(db, format("error getting valid derivers of `%1%'") % path);
    
    return derivers;
}


PathSet LocalStore::queryDerivationOutputs(const Path & path)
{
    SQLiteTxn txn(db);
    
    SQLiteStmtUse use(stmtQueryDerivationOutputs);
    stmtQueryDerivationOutputs.bind(queryValidPathId(path));
    
    PathSet outputs;
    int r;
    while ((r = sqlite3_step(stmtQueryDerivationOutputs)) == SQLITE_ROW) {
        const char * s = (const char *) sqlite3_column_text(stmtQueryDerivationOutputs, 1);
        assert(s);
        outputs.insert(s);
    }
    
    if (r != SQLITE_DONE)
        throwSQLiteError(db, format("error getting outputs of `%1%'") % path);

    return outputs;
}


StringSet LocalStore::queryDerivationOutputNames(const Path & path)
{
    SQLiteTxn txn(db);
    
    SQLiteStmtUse use(stmtQueryDerivationOutputs);
    stmtQueryDerivationOutputs.bind(queryValidPathId(path));
    
    StringSet outputNames;
    int r;
    while ((r = sqlite3_step(stmtQueryDerivationOutputs)) == SQLITE_ROW) {
        const char * s = (const char *) sqlite3_column_text(stmtQueryDerivationOutputs, 0);
        assert(s);
        outputNames.insert(s);
    }
    
    if (r != SQLITE_DONE)
        throwSQLiteError(db, format("error getting output names of `%1%'") % path);

    return outputNames;
}


void LocalStore::startSubstituter(const Path & substituter, RunningSubstituter & run)
{
    if (run.pid != -1) return;
    
    debug(format("starting substituter program `%1%'") % substituter);

    Pipe toPipe, fromPipe;
            
    toPipe.create();
    fromPipe.create();

    run.pid = fork();
            
    switch (run.pid) {

    case -1:
        throw SysError("unable to fork");

    case 0: /* child */
        try {
            /* Hack to let "make check" succeed on Darwin.  The
               libtool wrapper script sets DYLD_LIBRARY_PATH to our
               libutil (among others), but Perl also depends on a
               library named libutil.  As a result, substituters
               written in Perl (i.e. all of them) fail. */
            unsetenv("DYLD_LIBRARY_PATH");
            
            fromPipe.readSide.close();
            toPipe.writeSide.close();
            if (dup2(toPipe.readSide, STDIN_FILENO) == -1)
                throw SysError("dupping stdin");
            if (dup2(fromPipe.writeSide, STDOUT_FILENO) == -1)
                throw SysError("dupping stdout");
            closeMostFDs(set<int>());
            execl(substituter.c_str(), substituter.c_str(), "--query", NULL);
            throw SysError(format("executing `%1%'") % substituter);
        } catch (std::exception & e) {
            std::cerr << "error: " << e.what() << std::endl;
        }
        quickExit(1);
    }

    /* Parent. */
    
    run.to = toPipe.writeSide.borrow();
    run.from = fromPipe.readSide.borrow();
}


template<class T> T getIntLine(int fd)
{
    string s = readLine(fd);
    T res;
    if (!string2Int(s, res)) throw Error("integer expected from stream");
    return res;
}


bool LocalStore::hasSubstitutes(const Path & path)
{
    foreach (Paths::iterator, i, substituters) {
        RunningSubstituter & run(runningSubstituters[*i]);
        startSubstituter(*i, run);
        writeLine(run.to, "have\n" + path);
        if (getIntLine<int>(run.from)) return true;
    }

    return false;
}


bool LocalStore::querySubstitutablePathInfo(const Path & substituter,
    const Path & path, SubstitutablePathInfo & info)
{
    RunningSubstituter & run(runningSubstituters[substituter]);
    startSubstituter(substituter, run);

    writeLine(run.to, "info\n" + path);

    if (!getIntLine<int>(run.from)) return false;
    
    info.deriver = readLine(run.from);
    if (info.deriver != "") assertStorePath(info.deriver);
    int nrRefs = getIntLine<int>(run.from);
    while (nrRefs--) {
        Path p = readLine(run.from);
        assertStorePath(p);
        info.references.insert(p);
    }
    info.downloadSize = getIntLine<long long>(run.from);
    info.narSize = getIntLine<long long>(run.from);
    
    return true;
}


bool LocalStore::querySubstitutablePathInfo(const Path & path,
    SubstitutablePathInfo & info)
{
    foreach (Paths::iterator, i, substituters)
        if (querySubstitutablePathInfo(*i, path, info)) return true;
    return false;
}


Hash LocalStore::queryPathHash(const Path & path)
{
    return queryPathInfo(path).hash;
}


void LocalStore::registerValidPath(const ValidPathInfo & info)
{
    ValidPathInfos infos;
    infos.push_back(info);
    registerValidPaths(infos);
}


void LocalStore::registerValidPaths(const ValidPathInfos & infos)
{
    if (queryBoolSetting("sync-before-registering", true))
        sync();
    while (1) {
        try {
            SQLiteTxn txn(db);
            PathSet paths;
    
            foreach (ValidPathInfos::const_iterator, i, infos) {
                assert(i->hash.type == htSHA256);
                /* !!! Maybe the registration info should be updated if the
                   path is already valid. */
                if (!isValidPath(i->path)) addValidPath(*i);
                paths.insert(i->path);
            }

            foreach (ValidPathInfos::const_iterator, i, infos) {
                unsigned long long referrer = queryValidPathId(i->path);
                foreach (PathSet::iterator, j, i->references)
                    addReference(referrer, queryValidPathId(*j));
            }

            /* Do a topological sort of the paths.  This will throw an
               error if a cycle is detected and roll back the
               transaction.  Cycles can only occur when a derivation
               has multiple outputs. */
            topoSortPaths(*this, paths);

            txn.commit();
            break;
        } catch (SQLiteBusy & e) {
            /* Retry; the `txn' destructor will roll back the current
               transaction. */
        }
    }
}


/* Invalidate a path.  The caller is responsible for checking that
   there are no referrers. */
void LocalStore::invalidatePath(const Path & path)
{
    debug(format("invalidating path `%1%'") % path);

    drvHashes.erase(path);

    SQLiteStmtUse use(stmtInvalidatePath);

    stmtInvalidatePath.bind(path);

    if (sqlite3_step(stmtInvalidatePath) != SQLITE_DONE)
        throwSQLiteError(db, format("invalidating path `%1%' in database") % path);

    /* Note that the foreign key constraints on the Refs table take
       care of deleting the references entries for `path'. */
}


Path LocalStore::addToStoreFromDump(const string & dump, const string & name,
    bool recursive, HashType hashAlgo)
{
    Hash h = hashString(hashAlgo, dump);

    Path dstPath = makeFixedOutputPath(recursive, hashAlgo, h, name);

    addTempRoot(dstPath);

    if (!isValidPath(dstPath)) {

        /* The first check above is an optimisation to prevent
           unnecessary lock acquisition. */

        PathLocks outputLock(singleton<PathSet, Path>(dstPath));

        if (!isValidPath(dstPath)) {

            if (pathExists(dstPath)) deletePathWrapped(dstPath);

            if (recursive) {
                StringSource source(dump);
                restorePath(dstPath, source);
            } else
                writeFile(dstPath, dump);

            canonicalisePathMetaData(dstPath);

            /* Register the SHA-256 hash of the NAR serialisation of
               the path in the database.  We may just have computed it
               above (if called with recursive == true and hashAlgo ==
               sha256); otherwise, compute it here. */
            HashResult hash;
            if (recursive) {
                hash.first = hashAlgo == htSHA256 ? h : hashString(htSHA256, dump);
                hash.second = dump.size();
            } else
                hash = hashPath(htSHA256, dstPath);
            
            ValidPathInfo info;
            info.path = dstPath;
            info.hash = hash.first;
            info.narSize = hash.second;
            registerValidPath(info);
        }

        outputLock.setDeletion(true);
    }

    return dstPath;
}


Path LocalStore::addToStore(const Path & _srcPath,
    bool recursive, HashType hashAlgo, PathFilter & filter)
{
    Path srcPath(absPath(_srcPath));
    debug(format("adding `%1%' to the store") % srcPath);

    /* Read the whole path into memory. This is not a very scalable
       method for very large paths, but `copyPath' is mainly used for
       small files. */
    StringSink sink;
    if (recursive) 
        dumpPath(srcPath, sink, filter);
    else
        sink.s = readFile(srcPath);

    return addToStoreFromDump(sink.s, baseNameOf(srcPath), recursive, hashAlgo);
}


Path LocalStore::addTextToStore(const string & name, const string & s,
    const PathSet & references)
{
    Path dstPath = computeStorePathForText(name, s, references);
    
    addTempRoot(dstPath);

    if (!isValidPath(dstPath)) {

        PathLocks outputLock(singleton<PathSet, Path>(dstPath));

        if (!isValidPath(dstPath)) {

            if (pathExists(dstPath)) deletePathWrapped(dstPath);

            writeFile(dstPath, s);

            canonicalisePathMetaData(dstPath);

            HashResult hash = hashPath(htSHA256, dstPath);
            
            ValidPathInfo info;
            info.path = dstPath;
            info.hash = hash.first;
            info.narSize = hash.second;
            info.references = references;
            registerValidPath(info);
        }

        outputLock.setDeletion(true);
    }

    return dstPath;
}


struct HashAndWriteSink : Sink
{
    Sink & writeSink;
    HashSink hashSink;
    HashAndWriteSink(Sink & writeSink) : writeSink(writeSink), hashSink(htSHA256)
    {
    }
    virtual void operator () (const unsigned char * data, size_t len)
    {
        writeSink(data, len);
        hashSink(data, len);
    }
    Hash currentHash()
    {
        return hashSink.currentHash().first;
    }
};


#define EXPORT_MAGIC 0x4558494e


static void checkSecrecy(const Path & path)
{
    struct stat st;
    if (stat(path.c_str(), &st))
        throw SysError(format("getting status of `%1%'") % path);
    if ((st.st_mode & (S_IRWXG | S_IRWXO)) != 0)
        throw Error(format("file `%1%' should be secret (inaccessible to everybody else)!") % path);
}


void LocalStore::exportPath(const Path & path, bool sign,
    Sink & sink)
{
    assertStorePath(path);

    addTempRoot(path);
    if (!isValidPath(path))
        throw Error(format("path `%1%' is not valid") % path);

    HashAndWriteSink hashAndWriteSink(sink);
    
    dumpPath(path, hashAndWriteSink);

    /* Refuse to export paths that have changed.  This prevents
       filesystem corruption from spreading to other machines.
       Don't complain if the stored hash is zero (unknown). */
    Hash hash = hashAndWriteSink.currentHash();
    Hash storedHash = queryPathHash(path);
    if (hash != storedHash && storedHash != Hash(storedHash.type))
        throw Error(format("hash of path `%1%' has changed from `%2%' to `%3%'!") % path
            % printHash(storedHash) % printHash(hash));

    writeInt(EXPORT_MAGIC, hashAndWriteSink);

    writeString(path, hashAndWriteSink);
    
    PathSet references;
    queryReferences(path, references);
    writeStrings(references, hashAndWriteSink);

    Path deriver = queryDeriver(path);
    writeString(deriver, hashAndWriteSink);

    if (sign) {
        Hash hash = hashAndWriteSink.currentHash();
 
        writeInt(1, hashAndWriteSink);
        
        Path tmpDir = createTempDir();
        AutoDelete delTmp(tmpDir);
        Path hashFile = tmpDir + "/hash";
        writeFile(hashFile, printHash(hash));

        Path secretKey = nixConfDir + "/signing-key.sec";
        checkSecrecy(secretKey);

        Strings args;
        args.push_back("rsautl");
        args.push_back("-sign");
        args.push_back("-inkey");
        args.push_back(secretKey);
        args.push_back("-in");
        args.push_back(hashFile);
        string signature = runProgram(OPENSSL_PATH, true, args);

        writeString(signature, hashAndWriteSink);
        
    } else
        writeInt(0, hashAndWriteSink);
}


struct HashAndReadSource : Source
{
    Source & readSource;
    HashSink hashSink;
    bool hashing;
    HashAndReadSource(Source & readSource) : readSource(readSource), hashSink(htSHA256)
    {
        hashing = true;
    }
    size_t read(unsigned char * data, size_t len)
    {
        size_t n = readSource.read(data, len);
        if (hashing) hashSink(data, n);
        return n;
    }
};


/* Create a temporary directory in the store that won't be
   garbage-collected. */
Path LocalStore::createTempDirInStore()
{
    Path tmpDir;
    do {
        /* There is a slight possibility that `tmpDir' gets deleted by
           the GC between createTempDir() and addTempRoot(), so repeat
           until `tmpDir' exists. */
        tmpDir = createTempDir(nixStore);
        addTempRoot(tmpDir);
    } while (!pathExists(tmpDir));
    return tmpDir;
}


Path LocalStore::importPath(bool requireSignature, Source & source)
{
    HashAndReadSource hashAndReadSource(source);
    
    /* We don't yet know what store path this archive contains (the
       store path follows the archive data proper), and besides, we
       don't know yet whether the signature is valid. */
    Path tmpDir = createTempDirInStore();
    AutoDelete delTmp(tmpDir);
    Path unpacked = tmpDir + "/unpacked";

    restorePath(unpacked, hashAndReadSource);

    unsigned int magic = readInt(hashAndReadSource);
    if (magic != EXPORT_MAGIC)
        throw Error("Nix archive cannot be imported; wrong format");

    Path dstPath = readStorePath(hashAndReadSource);

    printMsg(lvlInfo, format("importing path `%1%'") % dstPath);

    PathSet references = readStorePaths<PathSet>(hashAndReadSource);

    Path deriver = readString(hashAndReadSource);
    if (deriver != "") assertStorePath(deriver);

    Hash hash = hashAndReadSource.hashSink.finish().first;
    hashAndReadSource.hashing = false;

    bool haveSignature = readInt(hashAndReadSource) == 1;

    if (requireSignature && !haveSignature)
        throw Error(format("imported archive of `%1%' lacks a signature") % dstPath);
    
    if (haveSignature) {
        string signature = readString(hashAndReadSource);

        if (requireSignature) {
            Path sigFile = tmpDir + "/sig";
            writeFile(sigFile, signature);

            Strings args;
            args.push_back("rsautl");
            args.push_back("-verify");
            args.push_back("-inkey");
            args.push_back(nixConfDir + "/signing-key.pub");
            args.push_back("-pubin");
            args.push_back("-in");
            args.push_back(sigFile);
            string hash2 = runProgram(OPENSSL_PATH, true, args);

            /* Note: runProgram() throws an exception if the signature
               is invalid. */

            if (printHash(hash) != hash2)
                throw Error(
                    "signed hash doesn't match actual contents of imported "
                    "archive; archive could be corrupt, or someone is trying "
                    "to import a Trojan horse");
        }
    }

    /* Do the actual import. */

    /* !!! way too much code duplication with addTextToStore() etc. */
    addTempRoot(dstPath);

    if (!isValidPath(dstPath)) {

        PathLocks outputLock;

        /* Lock the output path.  But don't lock if we're being called
           from a build hook (whose parent process already acquired a
           lock on this path). */
        Strings locksHeld = tokenizeString(getEnv("NIX_HELD_LOCKS"));
        if (find(locksHeld.begin(), locksHeld.end(), dstPath) == locksHeld.end())
            outputLock.lockPaths(singleton<PathSet, Path>(dstPath));

        if (!isValidPath(dstPath)) {

            if (pathExists(dstPath)) deletePathWrapped(dstPath);

            if (rename(unpacked.c_str(), dstPath.c_str()) == -1)
                throw SysError(format("cannot move `%1%' to `%2%'")
                    % unpacked % dstPath);

            canonicalisePathMetaData(dstPath);
            
            /* !!! if we were clever, we could prevent the hashPath()
               here. */
            HashResult hash = hashPath(htSHA256, dstPath);
            
            ValidPathInfo info;
            info.path = dstPath;
            info.hash = hash.first;
            info.narSize = hash.second;
            info.references = references;
            info.deriver = deriver != "" && isValidPath(deriver) ? deriver : "";
            registerValidPath(info);
        }
        
        outputLock.setDeletion(true);
    }
    
    return dstPath;
}


Paths LocalStore::importPaths(bool requireSignature, Source & source)
{
    Paths res;
    while (true) {
        unsigned long long n = readLongLong(source);
        if (n == 0) break;
        if (n != 1) throw Error("input doesn't look like something created by `nix-store --export'");
        res.push_back(importPath(requireSignature, source));
    }
    return res;
}


void LocalStore::deleteFromStore(const Path & path, unsigned long long & bytesFreed,
    unsigned long long & blocksFreed)
{
    bytesFreed = 0;

    assertStorePath(path);

    while (1) {
        try {
            SQLiteTxn txn(db);

            if (isValidPath(path)) {
                PathSet referrers; queryReferrers(path, referrers);
                referrers.erase(path); /* ignore self-references */
                if (!referrers.empty())
                    throw PathInUse(format("cannot delete path `%1%' because it is in use by %2%")
                        % path % showPaths(referrers));
                invalidatePath(path);
            }

            txn.commit();
            break;
        } catch (SQLiteBusy & e) { };
    }
    
    deletePathWrapped(path, bytesFreed, blocksFreed);
}


void LocalStore::verifyStore(bool checkContents)
{
    printMsg(lvlError, format("reading the Nix store..."));

    /* Acquire the global GC lock to prevent a garbage collection. */
    AutoCloseFD fdGCLock = openGCLock(ltWrite);
    
    Paths entries = readDirectory(nixStore);
    PathSet store(entries.begin(), entries.end());

    /* Check whether all valid paths actually exist. */
    printMsg(lvlInfo, "checking path existence...");

    PathSet validPaths2 = queryValidPaths(), validPaths, done;

    foreach (PathSet::iterator, i, validPaths2)
        verifyPath(*i, store, done, validPaths);

    /* Release the GC lock so that checking content hashes (which can
       take ages) doesn't block the GC or builds. */
    fdGCLock.close();

    /* Optionally, check the content hashes (slow). */
    if (checkContents) {
        printMsg(lvlInfo, "checking hashes...");

        Hash nullHash(htSHA256);

        foreach (PathSet::iterator, i, validPaths) {
            try {
                ValidPathInfo info = queryPathInfo(*i);

                /* Check the content hash (optionally - slow). */
                printMsg(lvlTalkative, format("checking contents of `%1%'") % *i);
                HashResult current = hashPath(info.hash.type, *i);
                
                if (info.hash != nullHash && info.hash != current.first) {
                    printMsg(lvlError, format("path `%1%' was modified! "
                            "expected hash `%2%', got `%3%'")
                        % *i % printHash(info.hash) % printHash(current.first));
                } else {

                    bool update = false;

                    /* Fill in missing hashes. */
                    if (info.hash == nullHash) {
                        printMsg(lvlError, format("fixing missing hash on `%1%'") % *i);
                        info.hash = current.first;
                        update = true;
                    }
                    
                    /* Fill in missing narSize fields (from old stores). */
                    if (info.narSize == 0) {
                        printMsg(lvlError, format("updating size field on `%1%' to %2%") % *i % current.second);
                        info.narSize = current.second;
                        update = true;                        
                    }

                    if (update) updatePathInfo(info);

                }
            
            } catch (Error & e) {
                /* It's possible that the path got GC'ed, so ignore
                   errors on invalid paths. */
                if (isValidPath(*i)) throw;
                printMsg(lvlError, format("warning: %1%") % e.msg());
            }
        }
    }
}


void LocalStore::verifyPath(const Path & path, const PathSet & store,
    PathSet & done, PathSet & validPaths)
{
    checkInterrupt();
    
    if (done.find(path) != done.end()) return;
    done.insert(path);

    if (!isStorePath(path)) {
        printMsg(lvlError, format("path `%1%' is not in the Nix store") % path);
        invalidatePath(path);
        return;
    }

    if (store.find(baseNameOf(path)) == store.end()) {
        /* Check any referrers first.  If we can invalidate them
           first, then we can invalidate this path as well. */
        bool canInvalidate = true;
        PathSet referrers; queryReferrers(path, referrers);
        foreach (PathSet::iterator, i, referrers)
            if (*i != path) {
                verifyPath(*i, store, done, validPaths);
                if (validPaths.find(*i) != validPaths.end())
                    canInvalidate = false;
            }

        if (canInvalidate) {
            printMsg(lvlError, format("path `%1%' disappeared, removing from database...") % path);
            invalidatePath(path);
        } else
            printMsg(lvlError, format("path `%1%' disappeared, but it still has valid referrers!") % path);
        
        return;
    }
    
    validPaths.insert(path);
}


/* Functions for upgrading from the pre-SQLite database. */

PathSet LocalStore::queryValidPathsOld()
{
    PathSet paths;
    Strings entries = readDirectory(nixDBPath + "/info");
    foreach (Strings::iterator, i, entries)
        if (i->at(0) != '.') paths.insert(nixStore + "/" + *i);
    return paths;
}


ValidPathInfo LocalStore::queryPathInfoOld(const Path & path)
{
    ValidPathInfo res;
    res.path = path;

    /* Read the info file. */
    string baseName = baseNameOf(path);
    Path infoFile = (format("%1%/info/%2%") % nixDBPath % baseName).str();
    if (!pathExists(infoFile))
        throw Error(format("path `%1%' is not valid") % path);
    string info = readFile(infoFile);

    /* Parse it. */
    Strings lines = tokenizeString(info, "\n");

    foreach (Strings::iterator, i, lines) {
        string::size_type p = i->find(':');
        if (p == string::npos)
            throw Error(format("corrupt line in `%1%': %2%") % infoFile % *i);
        string name(*i, 0, p);
        string value(*i, p + 2);
        if (name == "References") {
            Strings refs = tokenizeString(value, " ");
            res.references = PathSet(refs.begin(), refs.end());
        } else if (name == "Deriver") {
            res.deriver = value;
        } else if (name == "Hash") {
            res.hash = parseHashField(path, value);
        } else if (name == "Registered-At") {
            int n = 0;
            string2Int(value, n);
            res.registrationTime = n;
        }
    }

    return res;
}


/* Upgrade from schema 5 (Nix 0.12) to schema 6 (Nix >= 0.15). */
void LocalStore::upgradeStore6()
{
    printMsg(lvlError, "upgrading Nix store to new schema (this may take a while)...");

    openDB(true);

    PathSet validPaths = queryValidPathsOld();

    SQLiteTxn txn(db);
    
    foreach (PathSet::iterator, i, validPaths) {
        addValidPath(queryPathInfoOld(*i), false);
        std::cerr << ".";
    }

    std::cerr << "|";
    
    foreach (PathSet::iterator, i, validPaths) {
        ValidPathInfo info = queryPathInfoOld(*i);
        unsigned long long referrer = queryValidPathId(*i);
        foreach (PathSet::iterator, j, info.references)
            addReference(referrer, queryValidPathId(*j));
        std::cerr << ".";
    }

    std::cerr << "\n";

    txn.commit();
}


}