DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Untracked file

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975
/*
** 2003 September 6
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code used for creating, destroying, and populating
** a VDBE (or an "sqlite3_stmt" as it is known to the outside world.)  Prior
** to version 2.8.7, all this code was combined into the vdbe.c source file.
** But that file was getting too big so this subroutines were split out.
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"


/*
** When debugging the code generator in a symbolic debugger, one can
** set the sqlite3_vdbe_addop_trace to 1 and all opcodes will be printed
** as they are added to the instruction stream.
*/
#ifdef SQLITE_DEBUG
int sqlite3_vdbe_addop_trace = 0;
#endif


/*
** Create a new virtual database engine.
*/
Vdbe *sqlite3VdbeCreate(sqlite3 *db){
  Vdbe *p;
  p = sqliteMalloc( sizeof(Vdbe) );
  if( p==0 ) return 0;
  p->db = db;
  if( db->pVdbe ){
    db->pVdbe->pPrev = p;
  }
  p->pNext = db->pVdbe;
  p->pPrev = 0;
  db->pVdbe = p;
  p->magic = VDBE_MAGIC_INIT;
  return p;
}

/*
** Turn tracing on or off
*/
void sqlite3VdbeTrace(Vdbe *p, FILE *trace){
  p->trace = trace;
}

/*
** Resize the Vdbe.aOp array so that it contains at least N
** elements. If the Vdbe is in VDBE_MAGIC_RUN state, then
** the Vdbe.aOp array will be sized to contain exactly N
** elements. Vdbe.nOpAlloc is set to reflect the new size of
** the array.
**
** If an out-of-memory error occurs while resizing the array,
** Vdbe.aOp and Vdbe.nOpAlloc remain unchanged (this is so that
** any opcodes already allocated can be correctly deallocated
** along with the rest of the Vdbe).
*/
static void resizeOpArray(Vdbe *p, int N){
  int runMode = p->magic==VDBE_MAGIC_RUN;
  if( runMode || p->nOpAlloc<N ){
    VdbeOp *pNew;
    int nNew = N + 100*(!runMode);
    int oldSize = p->nOpAlloc;
    pNew = sqliteRealloc(p->aOp, nNew*sizeof(Op));
    if( pNew ){
      p->nOpAlloc = nNew;
      p->aOp = pNew;
      if( nNew>oldSize ){
        memset(&p->aOp[oldSize], 0, (nNew-oldSize)*sizeof(Op));
      }
    }
  }
}

/*
** Add a new instruction to the list of instructions current in the
** VDBE.  Return the address of the new instruction.
**
** Parameters:
**
**    p               Pointer to the VDBE
**
**    op              The opcode for this instruction
**
**    p1, p2          First two of the three possible operands.
**
** Use the sqlite3VdbeResolveLabel() function to fix an address and
** the sqlite3VdbeChangeP3() function to change the value of the P3
** operand.
*/
int sqlite3VdbeAddOp(Vdbe *p, int op, int p1, int p2){
  int i;
  VdbeOp *pOp;

  i = p->nOp;
  p->nOp++;
  assert( p->magic==VDBE_MAGIC_INIT );
  if( p->nOpAlloc<=i ){
    resizeOpArray(p, i+1);
    if( sqlite3MallocFailed() ){
      return 0;
    }
  }
  pOp = &p->aOp[i];
  pOp->opcode = op;
  pOp->p1 = p1;
  pOp->p2 = p2;
  pOp->p3 = 0;
  pOp->p3type = P3_NOTUSED;
  p->expired = 0;
#ifdef SQLITE_DEBUG
  if( sqlite3_vdbe_addop_trace ) sqlite3VdbePrintOp(0, i, &p->aOp[i]);
#endif
  return i;
}

/*
** Add an opcode that includes the p3 value.
*/
int sqlite3VdbeOp3(Vdbe *p, int op, int p1, int p2, const char *zP3,int p3type){
  int addr = sqlite3VdbeAddOp(p, op, p1, p2);
  sqlite3VdbeChangeP3(p, addr, zP3, p3type);
  return addr;
}

/*
** Create a new symbolic label for an instruction that has yet to be
** coded.  The symbolic label is really just a negative number.  The
** label can be used as the P2 value of an operation.  Later, when
** the label is resolved to a specific address, the VDBE will scan
** through its operation list and change all values of P2 which match
** the label into the resolved address.
**
** The VDBE knows that a P2 value is a label because labels are
** always negative and P2 values are suppose to be non-negative.
** Hence, a negative P2 value is a label that has yet to be resolved.
**
** Zero is returned if a malloc() fails.
*/
int sqlite3VdbeMakeLabel(Vdbe *p){
  int i;
  i = p->nLabel++;
  assert( p->magic==VDBE_MAGIC_INIT );
  if( i>=p->nLabelAlloc ){
    p->nLabelAlloc = p->nLabelAlloc*2 + 10;
    sqliteReallocOrFree((void**)&p->aLabel,
                          p->nLabelAlloc*sizeof(p->aLabel[0]));
  }
  if( p->aLabel ){
    p->aLabel[i] = -1;
  }
  return -1-i;
}

/*
** Resolve label "x" to be the address of the next instruction to
** be inserted.  The parameter "x" must have been obtained from
** a prior call to sqlite3VdbeMakeLabel().
*/
void sqlite3VdbeResolveLabel(Vdbe *p, int x){
  int j = -1-x;
  assert( p->magic==VDBE_MAGIC_INIT );
  assert( j>=0 && j<p->nLabel );
  if( p->aLabel ){
    p->aLabel[j] = p->nOp;
  }
}

/*
** Return non-zero if opcode 'op' is guarenteed not to push more values
** onto the VDBE stack than it pops off.
*/
static int opcodeNoPush(u8 op){
  /* The 10 NOPUSH_MASK_n constants are defined in the automatically
  ** generated header file opcodes.h. Each is a 16-bit bitmask, one
  ** bit corresponding to each opcode implemented by the virtual
  ** machine in vdbe.c. The bit is true if the word "no-push" appears
  ** in a comment on the same line as the "case OP_XXX:" in 
  ** sqlite3VdbeExec() in vdbe.c.
  **
  ** If the bit is true, then the corresponding opcode is guarenteed not
  ** to grow the stack when it is executed. Otherwise, it may grow the
  ** stack by at most one entry.
  **
  ** NOPUSH_MASK_0 corresponds to opcodes 0 to 15. NOPUSH_MASK_1 contains
  ** one bit for opcodes 16 to 31, and so on.
  **
  ** 16-bit bitmasks (rather than 32-bit) are specified in opcodes.h 
  ** because the file is generated by an awk program. Awk manipulates
  ** all numbers as floating-point and we don't want to risk a rounding
  ** error if someone builds with an awk that uses (for example) 32-bit 
  ** IEEE floats.
  */ 
  static const u32 masks[5] = {
    NOPUSH_MASK_0 + (((unsigned)NOPUSH_MASK_1)<<16),
    NOPUSH_MASK_2 + (((unsigned)NOPUSH_MASK_3)<<16),
    NOPUSH_MASK_4 + (((unsigned)NOPUSH_MASK_5)<<16),
    NOPUSH_MASK_6 + (((unsigned)NOPUSH_MASK_7)<<16),
    NOPUSH_MASK_8 + (((unsigned)NOPUSH_MASK_9)<<16)
  };
  assert( op<32*5 );
  return (masks[op>>5] & (1<<(op&0x1F)));
}

#ifndef NDEBUG
int sqlite3VdbeOpcodeNoPush(u8 op){
  return opcodeNoPush(op);
}
#endif

/*
** Loop through the program looking for P2 values that are negative.
** Each such value is a label.  Resolve the label by setting the P2
** value to its correct non-zero value.
**
** This routine is called once after all opcodes have been inserted.
**
** Variable *pMaxFuncArgs is set to the maximum value of any P2 argument 
** to an OP_Function or OP_AggStep opcode. This is used by 
** sqlite3VdbeMakeReady() to size the Vdbe.apArg[] array.
**
** The integer *pMaxStack is set to the maximum number of vdbe stack
** entries that static analysis reveals this program might need.
**
** This routine also does the following optimization:  It scans for
** Halt instructions where P1==SQLITE_CONSTRAINT or P2==OE_Abort or for
** IdxInsert instructions where P2!=0.  If no such instruction is
** found, then every Statement instruction is changed to a Noop.  In
** this way, we avoid creating the statement journal file unnecessarily.
*/
static void resolveP2Values(Vdbe *p, int *pMaxFuncArgs, int *pMaxStack){
  int i;
  int nMaxArgs = 0;
  int nMaxStack = p->nOp;
  Op *pOp;
  int *aLabel = p->aLabel;
  int doesStatementRollback = 0;
  int hasStatementBegin = 0;
  for(pOp=p->aOp, i=p->nOp-1; i>=0; i--, pOp++){
    u8 opcode = pOp->opcode;

    if( opcode==OP_Function || opcode==OP_AggStep ){
      if( pOp->p2>nMaxArgs ) nMaxArgs = pOp->p2;
    }else if( opcode==OP_Halt ){
      if( pOp->p1==SQLITE_CONSTRAINT && pOp->p2==OE_Abort ){
        doesStatementRollback = 1;
      }
    }else if( opcode==OP_IdxInsert ){
      if( pOp->p2 ){
        doesStatementRollback = 1;
      }
    }else if( opcode==OP_Statement ){
      hasStatementBegin = 1;
    }

    if( opcodeNoPush(opcode) ){
      nMaxStack--;
    }

    if( pOp->p2>=0 ) continue;
    assert( -1-pOp->p2<p->nLabel );
    pOp->p2 = aLabel[-1-pOp->p2];
  }
  sqliteFree(p->aLabel);
  p->aLabel = 0;

  *pMaxFuncArgs = nMaxArgs;
  *pMaxStack = nMaxStack;

  /* If we never rollback a statement transaction, then statement
  ** transactions are not needed.  So change every OP_Statement
  ** opcode into an OP_Noop.  This avoid a call to sqlite3OsOpenExclusive()
  ** which can be expensive on some platforms.
  */
  if( hasStatementBegin && !doesStatementRollback ){
    for(pOp=p->aOp, i=p->nOp-1; i>=0; i--, pOp++){
      if( pOp->opcode==OP_Statement ){
        pOp->opcode = OP_Noop;
      }
    }
  }
}

/*
** Return the address of the next instruction to be inserted.
*/
int sqlite3VdbeCurrentAddr(Vdbe *p){
  assert( p->magic==VDBE_MAGIC_INIT );
  return p->nOp;
}

/*
** Add a whole list of operations to the operation stack.  Return the
** address of the first operation added.
*/
int sqlite3VdbeAddOpList(Vdbe *p, int nOp, VdbeOpList const *aOp){
  int addr;
  assert( p->magic==VDBE_MAGIC_INIT );
  resizeOpArray(p, p->nOp + nOp);
  if( sqlite3MallocFailed() ){
    return 0;
  }
  addr = p->nOp;
  if( nOp>0 ){
    int i;
    VdbeOpList const *pIn = aOp;
    for(i=0; i<nOp; i++, pIn++){
      int p2 = pIn->p2;
      VdbeOp *pOut = &p->aOp[i+addr];
      pOut->opcode = pIn->opcode;
      pOut->p1 = pIn->p1;
      pOut->p2 = p2<0 ? addr + ADDR(p2) : p2;
      pOut->p3 = pIn->p3;
      pOut->p3type = pIn->p3 ? P3_STATIC : P3_NOTUSED;
#ifdef SQLITE_DEBUG
      if( sqlite3_vdbe_addop_trace ){
        sqlite3VdbePrintOp(0, i+addr, &p->aOp[i+addr]);
      }
#endif
    }
    p->nOp += nOp;
  }
  return addr;
}

/*
** Change the value of the P1 operand for a specific instruction.
** This routine is useful when a large program is loaded from a
** static array using sqlite3VdbeAddOpList but we want to make a
** few minor changes to the program.
*/
void sqlite3VdbeChangeP1(Vdbe *p, int addr, int val){
  assert( p==0 || p->magic==VDBE_MAGIC_INIT );
  if( p && addr>=0 && p->nOp>addr && p->aOp ){
    p->aOp[addr].p1 = val;
  }
}

/*
** Change the value of the P2 operand for a specific instruction.
** This routine is useful for setting a jump destination.
*/
void sqlite3VdbeChangeP2(Vdbe *p, int addr, int val){
  assert( val>=0 );
  assert( p==0 || p->magic==VDBE_MAGIC_INIT );
  if( p && addr>=0 && p->nOp>addr && p->aOp ){
    p->aOp[addr].p2 = val;
  }
}

/*
** Change the P2 operand of instruction addr so that it points to
** the address of the next instruction to be coded.
*/
void sqlite3VdbeJumpHere(Vdbe *p, int addr){
  sqlite3VdbeChangeP2(p, addr, p->nOp);
}

/*
** Delete a P3 value if necessary.
*/
static void freeP3(int p3type, void *p3){
  if( p3 ){
    switch( p3type ){
      case P3_DYNAMIC:
      case P3_KEYINFO:
      case P3_KEYINFO_HANDOFF: {
        sqliteFree(p3);
        break;
      }
      case P3_VDBEFUNC: {
        VdbeFunc *pVdbeFunc = (VdbeFunc *)p3;
        sqlite3VdbeDeleteAuxData(pVdbeFunc, 0);
        sqliteFree(pVdbeFunc);
        break;
      }
      case P3_MEM: {
        sqlite3ValueFree((sqlite3_value*)p3);
        break;
      }
    }
  }
}


/*
** Change N opcodes starting at addr to No-ops.
*/
void sqlite3VdbeChangeToNoop(Vdbe *p, int addr, int N){
  VdbeOp *pOp = &p->aOp[addr];
  while( N-- ){
    freeP3(pOp->p3type, pOp->p3);
    memset(pOp, 0, sizeof(pOp[0]));
    pOp->opcode = OP_Noop;
    pOp++;
  }
}

/*
** Change the value of the P3 operand for a specific instruction.
** This routine is useful when a large program is loaded from a
** static array using sqlite3VdbeAddOpList but we want to make a
** few minor changes to the program.
**
** If n>=0 then the P3 operand is dynamic, meaning that a copy of
** the string is made into memory obtained from sqliteMalloc().
** A value of n==0 means copy bytes of zP3 up to and including the
** first null byte.  If n>0 then copy n+1 bytes of zP3.
**
** If n==P3_KEYINFO it means that zP3 is a pointer to a KeyInfo structure.
** A copy is made of the KeyInfo structure into memory obtained from
** sqliteMalloc, to be freed when the Vdbe is finalized.
** n==P3_KEYINFO_HANDOFF indicates that zP3 points to a KeyInfo structure
** stored in memory that the caller has obtained from sqliteMalloc. The 
** caller should not free the allocation, it will be freed when the Vdbe is
** finalized.
** 
** Other values of n (P3_STATIC, P3_COLLSEQ etc.) indicate that zP3 points
** to a string or structure that is guaranteed to exist for the lifetime of
** the Vdbe. In these cases we can just copy the pointer.
**
** If addr<0 then change P3 on the most recently inserted instruction.
*/
void sqlite3VdbeChangeP3(Vdbe *p, int addr, const char *zP3, int n){
  Op *pOp;
  assert( p==0 || p->magic==VDBE_MAGIC_INIT );
  if( p==0 || p->aOp==0 || sqlite3MallocFailed() ){
    if (n != P3_KEYINFO) {
      freeP3(n, (void*)*(char**)&zP3);
    }
    return;
  }
  if( addr<0 || addr>=p->nOp ){
    addr = p->nOp - 1;
    if( addr<0 ) return;
  }
  pOp = &p->aOp[addr];
  freeP3(pOp->p3type, pOp->p3);
  pOp->p3 = 0;
  if( zP3==0 ){
    pOp->p3 = 0;
    pOp->p3type = P3_NOTUSED;
  }else if( n==P3_KEYINFO ){
    KeyInfo *pKeyInfo;
    int nField, nByte;

    nField = ((KeyInfo*)zP3)->nField;
    nByte = sizeof(*pKeyInfo) + (nField-1)*sizeof(pKeyInfo->aColl[0]) + nField;
    pKeyInfo = sqliteMallocRaw( nByte );
    pOp->p3 = (char*)pKeyInfo;
    if( pKeyInfo ){
      unsigned char *aSortOrder;
      memcpy(pKeyInfo, zP3, nByte);
      aSortOrder = pKeyInfo->aSortOrder;
      if( aSortOrder ){
        pKeyInfo->aSortOrder = (unsigned char*)&pKeyInfo->aColl[nField];
        memcpy(pKeyInfo->aSortOrder, aSortOrder, nField);
      }
      pOp->p3type = P3_KEYINFO;
    }else{
      pOp->p3type = P3_NOTUSED;
    }
  }else if( n==P3_KEYINFO_HANDOFF ){
    pOp->p3 = (char*)zP3;
    pOp->p3type = P3_KEYINFO;
  }else if( n<0 ){
    pOp->p3 = (char*)zP3;
    pOp->p3type = n;
  }else{
    if( n==0 ) n = strlen(zP3);
    pOp->p3 = sqliteStrNDup(zP3, n);
    pOp->p3type = P3_DYNAMIC;
  }
}

#ifndef NDEBUG
/*
** Replace the P3 field of the most recently coded instruction with
** comment text.
*/
void sqlite3VdbeComment(Vdbe *p, const char *zFormat, ...){
  va_list ap;
  assert( p->nOp>0 );
  assert( p->aOp==0 || p->aOp[p->nOp-1].p3==0 
          || sqlite3MallocFailed() );
  va_start(ap, zFormat);
  sqlite3VdbeChangeP3(p, -1, sqlite3VMPrintf(zFormat, ap), P3_DYNAMIC);
  va_end(ap);
}
#endif

/*
** Return the opcode for a given address.
*/
VdbeOp *sqlite3VdbeGetOp(Vdbe *p, int addr){
  assert( p->magic==VDBE_MAGIC_INIT );
  assert( addr>=0 && addr<p->nOp );
  return &p->aOp[addr];
}

#if !defined(SQLITE_OMIT_EXPLAIN) || !defined(NDEBUG) \
     || defined(VDBE_PROFILE) || defined(SQLITE_DEBUG)
/*
** Compute a string that describes the P3 parameter for an opcode.
** Use zTemp for any required temporary buffer space.
*/
static char *displayP3(Op *pOp, char *zTemp, int nTemp){
  char *zP3;
  assert( nTemp>=20 );
  switch( pOp->p3type ){
    case P3_KEYINFO: {
      int i, j;
      KeyInfo *pKeyInfo = (KeyInfo*)pOp->p3;
      sprintf(zTemp, "keyinfo(%d", pKeyInfo->nField);
      i = strlen(zTemp);
      for(j=0; j<pKeyInfo->nField; j++){
        CollSeq *pColl = pKeyInfo->aColl[j];
        if( pColl ){
          int n = strlen(pColl->zName);
          if( i+n>nTemp-6 ){
            strcpy(&zTemp[i],",...");
            break;
          }
          zTemp[i++] = ',';
          if( pKeyInfo->aSortOrder && pKeyInfo->aSortOrder[j] ){
            zTemp[i++] = '-';
          }
          strcpy(&zTemp[i], pColl->zName);
          i += n;
        }else if( i+4<nTemp-6 ){
          strcpy(&zTemp[i],",nil");
          i += 4;
        }
      }
      zTemp[i++] = ')';
      zTemp[i] = 0;
      assert( i<nTemp );
      zP3 = zTemp;
      break;
    }
    case P3_COLLSEQ: {
      CollSeq *pColl = (CollSeq*)pOp->p3;
      sprintf(zTemp, "collseq(%.20s)", pColl->zName);
      zP3 = zTemp;
      break;
    }
    case P3_FUNCDEF: {
      FuncDef *pDef = (FuncDef*)pOp->p3;
      char zNum[30];
      sprintf(zTemp, "%.*s", nTemp, pDef->zName);
      sprintf(zNum,"(%d)", pDef->nArg);
      if( strlen(zTemp)+strlen(zNum)+1<=nTemp ){
        strcat(zTemp, zNum);
      }
      zP3 = zTemp;
      break;
    }
    default: {
      zP3 = pOp->p3;
      if( zP3==0 || pOp->opcode==OP_Noop ){
        zP3 = "";
      }
    }
  }
  return zP3;
}
#endif


#if defined(VDBE_PROFILE) || defined(SQLITE_DEBUG)
/*
** Print a single opcode.  This routine is used for debugging only.
*/
void sqlite3VdbePrintOp(FILE *pOut, int pc, Op *pOp){
  char *zP3;
  char zPtr[50];
  static const char *zFormat1 = "%4d %-13s %4d %4d %s\n";
  if( pOut==0 ) pOut = stdout;
  zP3 = displayP3(pOp, zPtr, sizeof(zPtr));
  fprintf(pOut, zFormat1,
      pc, sqlite3OpcodeNames[pOp->opcode], pOp->p1, pOp->p2, zP3);
  fflush(pOut);
}
#endif

/*
** Release an array of N Mem elements
*/
static void releaseMemArray(Mem *p, int N){
  if( p ){
    while( N-->0 ){
      sqlite3VdbeMemRelease(p++);
    }
  }
}

#ifndef SQLITE_OMIT_EXPLAIN
/*
** Give a listing of the program in the virtual machine.
**
** The interface is the same as sqlite3VdbeExec().  But instead of
** running the code, it invokes the callback once for each instruction.
** This feature is used to implement "EXPLAIN".
*/
int sqlite3VdbeList(
  Vdbe *p                   /* The VDBE */
){
  sqlite3 *db = p->db;
  int i;
  int rc = SQLITE_OK;

  assert( p->explain );
  if( p->magic!=VDBE_MAGIC_RUN ) return SQLITE_MISUSE;
  assert( db->magic==SQLITE_MAGIC_BUSY );
  assert( p->rc==SQLITE_OK || p->rc==SQLITE_BUSY );

  /* Even though this opcode does not put dynamic strings onto the
  ** the stack, they may become dynamic if the user calls
  ** sqlite3_column_text16(), causing a translation to UTF-16 encoding.
  */
  if( p->pTos==&p->aStack[4] ){
    releaseMemArray(p->aStack, 5);
  }
  p->resOnStack = 0;

  do{
    i = p->pc++;
  }while( i<p->nOp && p->explain==2 && p->aOp[i].opcode!=OP_Explain );
  if( i>=p->nOp ){
    p->rc = SQLITE_OK;
    rc = SQLITE_DONE;
  }else if( db->flags & SQLITE_Interrupt ){
    db->flags &= ~SQLITE_Interrupt;
    p->rc = SQLITE_INTERRUPT;
    rc = SQLITE_ERROR;
    sqlite3SetString(&p->zErrMsg, sqlite3ErrStr(p->rc), (char*)0);
  }else{
    Op *pOp = &p->aOp[i];
    Mem *pMem = p->aStack;
    pMem->flags = MEM_Int;
    pMem->type = SQLITE_INTEGER;
    pMem->i = i;                                /* Program counter */
    pMem++;

    pMem->flags = MEM_Static|MEM_Str|MEM_Term;
    pMem->z = sqlite3OpcodeNames[pOp->opcode];  /* Opcode */
    pMem->n = strlen(pMem->z);
    pMem->type = SQLITE_TEXT;
    pMem->enc = SQLITE_UTF8;
    pMem++;

    pMem->flags = MEM_Int;
    pMem->i = pOp->p1;                          /* P1 */
    pMem->type = SQLITE_INTEGER;
    pMem++;

    pMem->flags = MEM_Int;
    pMem->i = pOp->p2;                          /* P2 */
    pMem->type = SQLITE_INTEGER;
    pMem++;

    pMem->flags = MEM_Ephem|MEM_Str|MEM_Term;   /* P3 */
    pMem->z = displayP3(pOp, pMem->zShort, sizeof(pMem->zShort));
    pMem->n = strlen(pMem->z);
    pMem->type = SQLITE_TEXT;
    pMem->enc = SQLITE_UTF8;

    p->nResColumn = 5 - 2*(p->explain-1);
    p->pTos = pMem;
    p->rc = SQLITE_OK;
    p->resOnStack = 1;
    rc = SQLITE_ROW;
  }
  return rc;
}
#endif /* SQLITE_OMIT_EXPLAIN */

/*
** Print the SQL that was used to generate a VDBE program.
*/
void sqlite3VdbePrintSql(Vdbe *p){
#ifdef SQLITE_DEBUG
  int nOp = p->nOp;
  VdbeOp *pOp;
  if( nOp<1 ) return;
  pOp = &p->aOp[nOp-1];
  if( pOp->opcode==OP_Noop && pOp->p3!=0 ){
    const char *z = pOp->p3;
    while( isspace(*(u8*)z) ) z++;
    printf("SQL: [%s]\n", z);
  }
#endif
}

/*
** Prepare a virtual machine for execution.  This involves things such
** as allocating stack space and initializing the program counter.
** After the VDBE has be prepped, it can be executed by one or more
** calls to sqlite3VdbeExec().  
**
** This is the only way to move a VDBE from VDBE_MAGIC_INIT to
** VDBE_MAGIC_RUN.
*/
void sqlite3VdbeMakeReady(
  Vdbe *p,                       /* The VDBE */
  int nVar,                      /* Number of '?' see in the SQL statement */
  int nMem,                      /* Number of memory cells to allocate */
  int nCursor,                   /* Number of cursors to allocate */
  int isExplain                  /* True if the EXPLAIN keywords is present */
){
  int n;

  assert( p!=0 );
  assert( p->magic==VDBE_MAGIC_INIT );

  /* There should be at least one opcode.
  */
  assert( p->nOp>0 );

  /* Set the magic to VDBE_MAGIC_RUN sooner rather than later. This
   * is because the call to resizeOpArray() below may shrink the
   * p->aOp[] array to save memory if called when in VDBE_MAGIC_RUN 
   * state.
   */
  p->magic = VDBE_MAGIC_RUN;

  /* No instruction ever pushes more than a single element onto the
  ** stack.  And the stack never grows on successive executions of the
  ** same loop.  So the total number of instructions is an upper bound
  ** on the maximum stack depth required.  (Added later:)  The
  ** resolveP2Values() call computes a tighter upper bound on the
  ** stack size.
  **
  ** Allocation all the stack space we will ever need.
  */
  if( p->aStack==0 ){
    int nArg;       /* Maximum number of args passed to a user function. */
    int nStack;     /* Maximum number of stack entries required */
    resolveP2Values(p, &nArg, &nStack);
    resizeOpArray(p, p->nOp);
    assert( nVar>=0 );
    assert( nStack<p->nOp );
    nStack = isExplain ? 10 : nStack;
    p->aStack = sqliteMalloc(
        nStack*sizeof(p->aStack[0])    /* aStack */
      + nArg*sizeof(Mem*)              /* apArg */
      + nVar*sizeof(Mem)               /* aVar */
      + nVar*sizeof(char*)             /* azVar */
      + nMem*sizeof(Mem)               /* aMem */
      + nCursor*sizeof(Cursor*)        /* apCsr */
    );
    if( !sqlite3MallocFailed() ){
      p->aMem = &p->aStack[nStack];
      p->nMem = nMem;
      p->aVar = &p->aMem[nMem];
      p->nVar = nVar;
      p->okVar = 0;
      p->apArg = (Mem**)&p->aVar[nVar];
      p->azVar = (char**)&p->apArg[nArg];
      p->apCsr = (Cursor**)&p->azVar[nVar];
      p->nCursor = nCursor;
      for(n=0; n<nVar; n++){
        p->aVar[n].flags = MEM_Null;
      }
    }
  }
  for(n=0; n<p->nMem; n++){
    p->aMem[n].flags = MEM_Null;
  }

#ifdef SQLITE_DEBUG
  if( (p->db->flags & SQLITE_VdbeListing)!=0
    || sqlite3OsFileExists("vdbe_explain")
  ){
    int i;
    printf("VDBE Program Listing:\n");
    sqlite3VdbePrintSql(p);
    for(i=0; i<p->nOp; i++){
      sqlite3VdbePrintOp(stdout, i, &p->aOp[i]);
    }
  }
  if( sqlite3OsFileExists("vdbe_trace") ){
    p->trace = stdout;
  }
#endif
  p->pTos = &p->aStack[-1];
  p->pc = -1;
  p->rc = SQLITE_OK;
  p->uniqueCnt = 0;
  p->returnDepth = 0;
  p->errorAction = OE_Abort;
  p->popStack =  0;
  p->explain |= isExplain;
  p->magic = VDBE_MAGIC_RUN;
  p->nChange = 0;
  p->cacheCtr = 1;
  p->minWriteFileFormat = 255;
#ifdef VDBE_PROFILE
  {
    int i;
    for(i=0; i<p->nOp; i++){
      p->aOp[i].cnt = 0;
      p->aOp[i].cycles = 0;
    }
  }
#endif
}

/*
** Close a cursor and release all the resources that cursor happens
** to hold.
*/
void sqlite3VdbeFreeCursor(Cursor *pCx){
  if( pCx==0 ){
    return;
  }
  if( pCx->pCursor ){
    sqlite3BtreeCloseCursor(pCx->pCursor);
  }
  if( pCx->pBt ){
    sqlite3BtreeClose(pCx->pBt);
  }
  sqliteFree(pCx->pData);
  sqliteFree(pCx->aType);
  sqliteFree(pCx);
}

/*
** Close all cursors
*/
static void closeAllCursors(Vdbe *p){
  int i;
  if( p->apCsr==0 ) return;
  for(i=0; i<p->nCursor; i++){
    sqlite3VdbeFreeCursor(p->apCsr[i]);
    p->apCsr[i] = 0;
  }
}

/*
** Clean up the VM after execution.
**
** This routine will automatically close any cursors, lists, and/or
** sorters that were left open.  It also deletes the values of
** variables in the aVar[] array.
*/
static void Cleanup(Vdbe *p){
  int i;
  if( p->aStack ){
    releaseMemArray(p->aStack, 1 + (p->pTos - p->aStack));
    p->pTos = &p->aStack[-1];
  }
  closeAllCursors(p);
  releaseMemArray(p->aMem, p->nMem);
  sqlite3VdbeFifoClear(&p->sFifo);
  if( p->contextStack ){
    for(i=0; i<p->contextStackTop; i++){
      sqlite3VdbeFifoClear(&p->contextStack[i].sFifo);
    }
    sqliteFree(p->contextStack);
  }
  p->contextStack = 0;
  p->contextStackDepth = 0;
  p->contextStackTop = 0;
  sqliteFree(p->zErrMsg);
  p->zErrMsg = 0;
}

/*
** Set the number of result columns that will be returned by this SQL
** statement. This is now set at compile time, rather than during
** execution of the vdbe program so that sqlite3_column_count() can
** be called on an SQL statement before sqlite3_step().
*/
void sqlite3VdbeSetNumCols(Vdbe *p, int nResColumn){
  Mem *pColName;
  int n;
  releaseMemArray(p->aColName, p->nResColumn*COLNAME_N);
  sqliteFree(p->aColName);
  n = nResColumn*COLNAME_N;
  p->nResColumn = nResColumn;
  p->aColName = pColName = (Mem*)sqliteMalloc( sizeof(Mem)*n );
  if( p->aColName==0 ) return;
  while( n-- > 0 ){
    (pColName++)->flags = MEM_Null;
  }
}

/*
** Set the name of the idx'th column to be returned by the SQL statement.
** zName must be a pointer to a nul terminated string.
**
** This call must be made after a call to sqlite3VdbeSetNumCols().
**
** If N==P3_STATIC  it means that zName is a pointer to a constant static
** string and we can just copy the pointer. If it is P3_DYNAMIC, then 
** the string is freed using sqliteFree() when the vdbe is finished with
** it. Otherwise, N bytes of zName are copied.
*/
int sqlite3VdbeSetColName(Vdbe *p, int idx, int var, const char *zName, int N){
  int rc;
  Mem *pColName;
  assert( idx<p->nResColumn );
  assert( var<COLNAME_N );
  if( sqlite3MallocFailed() ) return SQLITE_NOMEM;
  assert( p->aColName!=0 );
  pColName = &(p->aColName[idx+var*p->nResColumn]);
  if( N==P3_DYNAMIC || N==P3_STATIC ){
    rc = sqlite3VdbeMemSetStr(pColName, zName, -1, SQLITE_UTF8, SQLITE_STATIC);
  }else{
    rc = sqlite3VdbeMemSetStr(pColName, zName, N, SQLITE_UTF8,SQLITE_TRANSIENT);
  }
  if( rc==SQLITE_OK && N==P3_DYNAMIC ){
    pColName->flags = (pColName->flags&(~MEM_Static))|MEM_Dyn;
    pColName->xDel = 0;
  }
  return rc;
}

/*
** A read or write transaction may or may not be active on database handle
** db. If a transaction is active, commit it. If there is a
** write-transaction spanning more than one database file, this routine
** takes care of the master journal trickery.
*/
static int vdbeCommit(sqlite3 *db){
  int i;
  int nTrans = 0;  /* Number of databases with an active write-transaction */
  int rc = SQLITE_OK;
  int needXcommit = 0;

  for(i=0; i<db->nDb; i++){ 
    Btree *pBt = db->aDb[i].pBt;
    if( pBt && sqlite3BtreeIsInTrans(pBt) ){
      needXcommit = 1;
      if( i!=1 ) nTrans++;
    }
  }

  /* If there are any write-transactions at all, invoke the commit hook */
  if( needXcommit && db->xCommitCallback ){
    sqlite3SafetyOff(db);
    rc = db->xCommitCallback(db->pCommitArg);
    sqlite3SafetyOn(db);
    if( rc ){
      return SQLITE_CONSTRAINT;
    }
  }

  /* The simple case - no more than one database file (not counting the
  ** TEMP database) has a transaction active.   There is no need for the
  ** master-journal.
  **
  ** If the return value of sqlite3BtreeGetFilename() is a zero length
  ** string, it means the main database is :memory:.  In that case we do
  ** not support atomic multi-file commits, so use the simple case then
  ** too.
  */
  if( 0==strlen(sqlite3BtreeGetFilename(db->aDb[0].pBt)) || nTrans<=1 ){
    for(i=0; rc==SQLITE_OK && i<db->nDb; i++){ 
      Btree *pBt = db->aDb[i].pBt;
      if( pBt ){
        rc = sqlite3BtreeSync(pBt, 0);
      }
    }

    /* Do the commit only if all databases successfully synced */
    if( rc==SQLITE_OK ){
      for(i=0; i<db->nDb; i++){
        Btree *pBt = db->aDb[i].pBt;
        if( pBt ){
          sqlite3BtreeCommit(pBt);
        }
      }
    }
  }

  /* The complex case - There is a multi-file write-transaction active.
  ** This requires a master journal file to ensure the transaction is
  ** committed atomicly.
  */
#ifndef SQLITE_OMIT_DISKIO
  else{
    int needSync = 0;
    char *zMaster = 0;   /* File-name for the master journal */
    char const *zMainFile = sqlite3BtreeGetFilename(db->aDb[0].pBt);
    OsFile *master = 0;

    /* Select a master journal file name */
    do {
      u32 random;
      sqliteFree(zMaster);
      sqlite3Randomness(sizeof(random), &random);
      zMaster = sqlite3MPrintf("%s-mj%08X", zMainFile, random&0x7fffffff);
      if( !zMaster ){
        return SQLITE_NOMEM;
      }
    }while( sqlite3OsFileExists(zMaster) );

    /* Open the master journal. */
    rc = sqlite3OsOpenExclusive(zMaster, &master, 0);
    if( rc!=SQLITE_OK ){
      sqliteFree(zMaster);
      return rc;
    }
 
    /* Write the name of each database file in the transaction into the new
    ** master journal file. If an error occurs at this point close
    ** and delete the master journal file. All the individual journal files
    ** still have 'null' as the master journal pointer, so they will roll
    ** back independently if a failure occurs.
    */
    for(i=0; i<db->nDb; i++){ 
      Btree *pBt = db->aDb[i].pBt;
      if( i==1 ) continue;   /* Ignore the TEMP database */
      if( pBt && sqlite3BtreeIsInTrans(pBt) ){
        char const *zFile = sqlite3BtreeGetJournalname(pBt);
        if( zFile[0]==0 ) continue;  /* Ignore :memory: databases */
        if( !needSync && !sqlite3BtreeSyncDisabled(pBt) ){
          needSync = 1;
        }
        rc = sqlite3OsWrite(master, zFile, strlen(zFile)+1);
        if( rc!=SQLITE_OK ){
          sqlite3OsClose(&master);
          sqlite3OsDelete(zMaster);
          sqliteFree(zMaster);
          return rc;
        }
      }
    }


    /* Sync the master journal file. Before doing this, open the directory
    ** the master journal file is store in so that it gets synced too.
    */
    zMainFile = sqlite3BtreeGetDirname(db->aDb[0].pBt);
    rc = sqlite3OsOpenDirectory(master, zMainFile);
    if( rc!=SQLITE_OK ||
          (needSync && (rc=sqlite3OsSync(master,0))!=SQLITE_OK) ){
      sqlite3OsClose(&master);
      sqlite3OsDelete(zMaster);
      sqliteFree(zMaster);
      return rc;
    }

    /* Sync all the db files involved in the transaction. The same call
    ** sets the master journal pointer in each individual journal. If
    ** an error occurs here, do not delete the master journal file.
    **
    ** If the error occurs during the first call to sqlite3BtreeSync(),
    ** then there is a chance that the master journal file will be
    ** orphaned. But we cannot delete it, in case the master journal
    ** file name was written into the journal file before the failure
    ** occured.
    */
    for(i=0; i<db->nDb; i++){ 
      Btree *pBt = db->aDb[i].pBt;
      if( pBt && sqlite3BtreeIsInTrans(pBt) ){
        rc = sqlite3BtreeSync(pBt, zMaster);
        if( rc!=SQLITE_OK ){
          sqlite3OsClose(&master);
          sqliteFree(zMaster);
          return rc;
        }
      }
    }
    sqlite3OsClose(&master);

    /* Delete the master journal file. This commits the transaction. After
    ** doing this the directory is synced again before any individual
    ** transaction files are deleted.
    */
    rc = sqlite3OsDelete(zMaster);
    assert( rc==SQLITE_OK );
    sqliteFree(zMaster);
    zMaster = 0;
    rc = sqlite3OsSyncDirectory(zMainFile);
    if( rc!=SQLITE_OK ){
      /* This is not good. The master journal file has been deleted, but
      ** the directory sync failed. There is no completely safe course of
      ** action from here. The individual journals contain the name of the
      ** master journal file, but there is no way of knowing if that
      ** master journal exists now or if it will exist after the operating
      ** system crash that may follow the fsync() failure.
      */
      return rc;
    }

    /* All files and directories have already been synced, so the following
    ** calls to sqlite3BtreeCommit() are only closing files and deleting
    ** journals. If something goes wrong while this is happening we don't
    ** really care. The integrity of the transaction is already guaranteed,
    ** but some stray 'cold' journals may be lying around. Returning an
    ** error code won't help matters.
    */
    for(i=0; i<db->nDb; i++){ 
      Btree *pBt = db->aDb[i].pBt;
      if( pBt ){
        sqlite3BtreeCommit(pBt);
      }
    }
  }
#endif

  return rc;
}

/*
** Find every active VM other than pVdbe and change its status to
** aborted.  This happens when one VM causes a rollback due to an
** ON CONFLICT ROLLBACK clause (for example).  The other VMs must be
** aborted so that they do not have data rolled out from underneath
** them leading to a segfault.
*/
void sqlite3AbortOtherActiveVdbes(sqlite3 *db, Vdbe *pExcept){
  Vdbe *pOther;
  for(pOther=db->pVdbe; pOther; pOther=pOther->pNext){
    if( pOther==pExcept ) continue;
    if( pOther->magic!=VDBE_MAGIC_RUN || pOther->pc<0 ) continue;
    closeAllCursors(pOther);
    pOther->aborted = 1;
  }
}

/* 
** This routine checks that the sqlite3.activeVdbeCnt count variable
** matches the number of vdbe's in the list sqlite3.pVdbe that are
** currently active. An assertion fails if the two counts do not match.
** This is an internal self-check only - it is not an essential processing
** step.
**
** This is a no-op if NDEBUG is defined.
*/
#ifndef NDEBUG
static void checkActiveVdbeCnt(sqlite3 *db){
  Vdbe *p;
  int cnt = 0;
  p = db->pVdbe;
  while( p ){
    if( p->magic==VDBE_MAGIC_RUN && p->pc>=0 ){
      cnt++;
    }
    p = p->pNext;
  }
  assert( cnt==db->activeVdbeCnt );
}
#else
#define checkActiveVdbeCnt(x)
#endif

/*
** This routine is called the when a VDBE tries to halt.  If the VDBE
** has made changes and is in autocommit mode, then commit those
** changes.  If a rollback is needed, then do the rollback.
**
** This routine is the only way to move the state of a VM from
** SQLITE_MAGIC_RUN to SQLITE_MAGIC_HALT.
**
** Return an error code.  If the commit could not complete because of
** lock contention, return SQLITE_BUSY.  If SQLITE_BUSY is returned, it
** means the close did not happen and needs to be repeated.
*/
int sqlite3VdbeHalt(Vdbe *p){
  sqlite3 *db = p->db;
  int i;
  int (*xFunc)(Btree *pBt) = 0;  /* Function to call on each btree backend */
  int isSpecialError;            /* Set to true if SQLITE_NOMEM or IOERR */

  /* This function contains the logic that determines if a statement or
  ** transaction will be committed or rolled back as a result of the
  ** execution of this virtual machine. 
  **
  ** Special errors:
  **
  **     If an SQLITE_NOMEM error has occured in a statement that writes to
  **     the database, then either a statement or transaction must be rolled
  **     back to ensure the tree-structures are in a consistent state. A
  **     statement transaction is rolled back if one is open, otherwise the
  **     entire transaction must be rolled back.
  **
  **     If an SQLITE_IOERR error has occured in a statement that writes to
  **     the database, then the entire transaction must be rolled back. The
  **     I/O error may have caused garbage to be written to the journal 
  **     file. Were the transaction to continue and eventually be rolled 
  **     back that garbage might end up in the database file.
  **     
  **     In both of the above cases, the Vdbe.errorAction variable is 
  **     ignored. If the sqlite3.autoCommit flag is false and a transaction
  **     is rolled back, it will be set to true.
  **
  ** Other errors:
  **
  ** No error:
  **
  */

  if( sqlite3MallocFailed() ){
    p->rc = SQLITE_NOMEM;
  }
  if( p->magic!=VDBE_MAGIC_RUN ){
    /* Already halted.  Nothing to do. */
    assert( p->magic==VDBE_MAGIC_HALT );
    return SQLITE_OK;
  }
  closeAllCursors(p);
  checkActiveVdbeCnt(db);

  /* No commit or rollback needed if the program never started */
  if( p->pc>=0 ){

    /* Check for one of the special errors - SQLITE_NOMEM or SQLITE_IOERR */
    isSpecialError = ((p->rc==SQLITE_NOMEM || p->rc==SQLITE_IOERR)?1:0);
    if( isSpecialError ){
      /* This loop does static analysis of the query to see which of the
      ** following three categories it falls into:
      **
      **     Read-only
      **     Query with statement journal
      **     Query without statement journal
      **
      ** We could do something more elegant than this static analysis (i.e.
      ** store the type of query as part of the compliation phase), but 
      ** handling malloc() or IO failure is a fairly obscure edge case so 
      ** this is probably easier. Todo: Might be an opportunity to reduce 
      ** code size a very small amount though...
      */
      int isReadOnly = 1;
      int isStatement = 0;
      assert(p->aOp || p->nOp==0);
      for(i=0; i<p->nOp; i++){ 
        switch( p->aOp[i].opcode ){
          case OP_Transaction:
            isReadOnly = 0;
            break;
          case OP_Statement:
            isStatement = 1;
            break;
        }
      }
  
      /* If the query was read-only, we need do no rollback at all. Otherwise,
      ** proceed with the special handling.
      */
      if( !isReadOnly ){
        if( p->rc==SQLITE_NOMEM && isStatement ){
          xFunc = sqlite3BtreeRollbackStmt;
        }else{
          /* We are forced to roll back the active transaction. Before doing
          ** so, abort any other statements this handle currently has active.
          */
          sqlite3AbortOtherActiveVdbes(db, p);
          sqlite3RollbackAll(db);
          db->autoCommit = 1;
        }
      }
    }
  
    /* If the auto-commit flag is set and this is the only active vdbe, then
    ** we do either a commit or rollback of the current transaction. 
    **
    ** Note: This block also runs if one of the special errors handled 
    ** above has occured. 
    */
    if( db->autoCommit && db->activeVdbeCnt==1 ){
      if( p->rc==SQLITE_OK || (p->errorAction==OE_Fail && !isSpecialError) ){
	/* The auto-commit flag is true, and the vdbe program was 
        ** successful or hit an 'OR FAIL' constraint. This means a commit 
        ** is required.
        */
        int rc = vdbeCommit(db);
        if( rc==SQLITE_BUSY ){
          return SQLITE_BUSY;
        }else if( rc!=SQLITE_OK ){
          p->rc = rc;
          sqlite3RollbackAll(db);
        }else{
          sqlite3CommitInternalChanges(db);
        }
      }else{
        sqlite3RollbackAll(db);
      }
    }else if( !xFunc ){
      if( p->rc==SQLITE_OK || p->errorAction==OE_Fail ){
        xFunc = sqlite3BtreeCommitStmt;
      }else if( p->errorAction==OE_Abort ){
        xFunc = sqlite3BtreeRollbackStmt;
      }else{
        sqlite3AbortOtherActiveVdbes(db, p);
        sqlite3RollbackAll(db);
        db->autoCommit = 1;
      }
    }
  
    /* If xFunc is not NULL, then it is one of sqlite3BtreeRollbackStmt or
    ** sqlite3BtreeCommitStmt. Call it once on each backend. If an error occurs
    ** and the return code is still SQLITE_OK, set the return code to the new
    ** error value.
    */
    assert(!xFunc ||
      xFunc==sqlite3BtreeCommitStmt ||
      xFunc==sqlite3BtreeRollbackStmt
    );
    for(i=0; xFunc && i<db->nDb; i++){ 
      int rc;
      Btree *pBt = db->aDb[i].pBt;
      if( pBt ){
        rc = xFunc(pBt);
        if( rc && (p->rc==SQLITE_OK || p->rc==SQLITE_CONSTRAINT) ){
          p->rc = rc;
          sqlite3SetString(&p->zErrMsg, 0);
        }
      }
    }
  
    /* If this was an INSERT, UPDATE or DELETE and the statement was committed, 
    ** set the change counter. 
    */
    if( p->changeCntOn && p->pc>=0 ){
      if( !xFunc || xFunc==sqlite3BtreeCommitStmt ){
        sqlite3VdbeSetChanges(db, p->nChange);
      }else{
        sqlite3VdbeSetChanges(db, 0);
      }
      p->nChange = 0;
    }
  
    /* Rollback or commit any schema changes that occurred. */
    if( p->rc!=SQLITE_OK && db->flags&SQLITE_InternChanges ){
      sqlite3ResetInternalSchema(db, 0);
      db->flags = (db->flags | SQLITE_InternChanges);
    }
  }

  /* We have successfully halted and closed the VM.  Record this fact. */
  if( p->pc>=0 ){
    db->activeVdbeCnt--;
  }
  p->magic = VDBE_MAGIC_HALT;
  checkActiveVdbeCnt(db);

  return SQLITE_OK;
}

/*
** Clean up a VDBE after execution but do not delete the VDBE just yet.
** Write any error messages into *pzErrMsg.  Return the result code.
**
** After this routine is run, the VDBE should be ready to be executed
** again.
**
** To look at it another way, this routine resets the state of the
** virtual machine from VDBE_MAGIC_RUN or VDBE_MAGIC_HALT back to
** VDBE_MAGIC_INIT.
*/
int sqlite3VdbeReset(Vdbe *p){
  if( p->magic!=VDBE_MAGIC_RUN && p->magic!=VDBE_MAGIC_HALT ){
    sqlite3Error(p->db, SQLITE_MISUSE, 0);
    return SQLITE_MISUSE;
  }

  /* If the VM did not run to completion or if it encountered an
  ** error, then it might not have been halted properly.  So halt
  ** it now.
  */
  sqlite3VdbeHalt(p);

  /* If the VDBE has be run even partially, then transfer the error code
  ** and error message from the VDBE into the main database structure.  But
  ** if the VDBE has just been set to run but has not actually executed any
  ** instructions yet, leave the main database error information unchanged.
  */
  if( p->pc>=0 ){
    if( p->zErrMsg ){
      sqlite3* db = p->db;
      sqlite3ValueSetStr(db->pErr, -1, p->zErrMsg, SQLITE_UTF8, sqlite3FreeX);
      db->errCode = p->rc;
      p->zErrMsg = 0;
    }else if( p->rc ){
      sqlite3Error(p->db, p->rc, 0);
    }else{
      sqlite3Error(p->db, SQLITE_OK, 0);
    }
  }else if( p->rc && p->expired ){
    /* The expired flag was set on the VDBE before the first call
    ** to sqlite3_step(). For consistency (since sqlite3_step() was
    ** called), set the database error in this case as well.
    */
    sqlite3Error(p->db, p->rc, 0);
  }

  /* Reclaim all memory used by the VDBE
  */
  Cleanup(p);

  /* Save profiling information from this VDBE run.
  */
  assert( p->pTos<&p->aStack[p->pc<0?0:p->pc] || !p->aStack );
#ifdef VDBE_PROFILE
  {
    FILE *out = fopen("vdbe_profile.out", "a");
    if( out ){
      int i;
      fprintf(out, "---- ");
      for(i=0; i<p->nOp; i++){
        fprintf(out, "%02x", p->aOp[i].opcode);
      }
      fprintf(out, "\n");
      for(i=0; i<p->nOp; i++){
        fprintf(out, "%6d %10lld %8lld ",
           p->aOp[i].cnt,
           p->aOp[i].cycles,
           p->aOp[i].cnt>0 ? p->aOp[i].cycles/p->aOp[i].cnt : 0
        );
        sqlite3VdbePrintOp(out, i, &p->aOp[i]);
      }
      fclose(out);
    }
  }
#endif
  p->magic = VDBE_MAGIC_INIT;
  p->aborted = 0;
  if( p->rc==SQLITE_SCHEMA ){
    sqlite3ResetInternalSchema(p->db, 0);
  }
  return p->rc;
}
 
/*
** Clean up and delete a VDBE after execution.  Return an integer which is
** the result code.  Write any error message text into *pzErrMsg.
*/
int sqlite3VdbeFinalize(Vdbe *p){
  int rc = SQLITE_OK;

  if( p->magic==VDBE_MAGIC_RUN || p->magic==VDBE_MAGIC_HALT ){
    rc = sqlite3VdbeReset(p);
  }else if( p->magic!=VDBE_MAGIC_INIT ){
    return SQLITE_MISUSE;
  }
  sqlite3VdbeDelete(p);
  return rc;
}

/*
** Call the destructor for each auxdata entry in pVdbeFunc for which
** the corresponding bit in mask is clear.  Auxdata entries beyond 31
** are always destroyed.  To destroy all auxdata entries, call this
** routine with mask==0.
*/
void sqlite3VdbeDeleteAuxData(VdbeFunc *pVdbeFunc, int mask){
  int i;
  for(i=0; i<pVdbeFunc->nAux; i++){
    struct AuxData *pAux = &pVdbeFunc->apAux[i];
    if( (i>31 || !(mask&(1<<i))) && pAux->pAux ){
      if( pAux->xDelete ){
        pAux->xDelete(pAux->pAux);
      }
      pAux->pAux = 0;
    }
  }
}

/*
** Delete an entire VDBE.
*/
void sqlite3VdbeDelete(Vdbe *p){
  int i;
  if( p==0 ) return;
  Cleanup(p);
  if( p->pPrev ){
    p->pPrev->pNext = p->pNext;
  }else{
    assert( p->db->pVdbe==p );
    p->db->pVdbe = p->pNext;
  }
  if( p->pNext ){
    p->pNext->pPrev = p->pPrev;
  }
  if( p->aOp ){
    for(i=0; i<p->nOp; i++){
      Op *pOp = &p->aOp[i];
      freeP3(pOp->p3type, pOp->p3);
    }
    sqliteFree(p->aOp);
  }
  releaseMemArray(p->aVar, p->nVar);
  sqliteFree(p->aLabel);
  sqliteFree(p->aStack);
  releaseMemArray(p->aColName, p->nResColumn*COLNAME_N);
  sqliteFree(p->aColName);
  p->magic = VDBE_MAGIC_DEAD;
  sqliteFree(p);
}

/*
** If a MoveTo operation is pending on the given cursor, then do that
** MoveTo now.  Return an error code.  If no MoveTo is pending, this
** routine does nothing and returns SQLITE_OK.
*/
int sqlite3VdbeCursorMoveto(Cursor *p){
  if( p->deferredMoveto ){
    int res, rc;
    extern int sqlite3_search_count;
    assert( p->isTable );
    if( p->isTable ){
      rc = sqlite3BtreeMoveto(p->pCursor, 0, p->movetoTarget, &res);
    }else{
      rc = sqlite3BtreeMoveto(p->pCursor,(char*)&p->movetoTarget,
                              sizeof(i64),&res);
    }
    if( rc ) return rc;
    *p->pIncrKey = 0;
    p->lastRowid = keyToInt(p->movetoTarget);
    p->rowidIsValid = res==0;
    if( res<0 ){
      rc = sqlite3BtreeNext(p->pCursor, &res);
      if( rc ) return rc;
    }
    sqlite3_search_count++;
    p->deferredMoveto = 0;
    p->cacheStatus = CACHE_STALE;
  }
  return SQLITE_OK;
}

/*
** The following functions:
**
** sqlite3VdbeSerialType()
** sqlite3VdbeSerialTypeLen()
** sqlite3VdbeSerialRead()
** sqlite3VdbeSerialLen()
** sqlite3VdbeSerialWrite()
**
** encapsulate the code that serializes values for storage in SQLite
** data and index records. Each serialized value consists of a
** 'serial-type' and a blob of data. The serial type is an 8-byte unsigned
** integer, stored as a varint.
**
** In an SQLite index record, the serial type is stored directly before
** the blob of data that it corresponds to. In a table record, all serial
** types are stored at the start of the record, and the blobs of data at
** the end. Hence these functions allow the caller to handle the
** serial-type and data blob seperately.
**
** The following table describes the various storage classes for data:
**
**   serial type        bytes of data      type
**   --------------     ---------------    ---------------
**      0                     0            NULL
**      1                     1            signed integer
**      2                     2            signed integer
**      3                     3            signed integer
**      4                     4            signed integer
**      5                     6            signed integer
**      6                     8            signed integer
**      7                     8            IEEE float
**      8                     0            Integer constant 0
**      9                     0            Integer constant 1
**     10,11                               reserved for expansion
**    N>=12 and even       (N-12)/2        BLOB
**    N>=13 and odd        (N-13)/2        text
**
** The 8 and 9 types were added in 3.3.0, file format 4.  Prior versions
** of SQLite will not understand those serial types.
*/

/*
** Return the serial-type for the value stored in pMem.
*/
u32 sqlite3VdbeSerialType(Mem *pMem, int file_format){
  int flags = pMem->flags;

  if( flags&MEM_Null ){
    return 0;
  }
  if( flags&MEM_Int ){
    /* Figure out whether to use 1, 2, 4, 6 or 8 bytes. */
#   define MAX_6BYTE ((((i64)0x00001000)<<32)-1)
    i64 i = pMem->i;
    u64 u;
    if( file_format>=4 && (i&1)==i ){
      return 8+i;
    }
    u = i<0 ? -i : i;
    if( u<=127 ) return 1;
    if( u<=32767 ) return 2;
    if( u<=8388607 ) return 3;
    if( u<=2147483647 ) return 4;
    if( u<=MAX_6BYTE ) return 5;
    return 6;
  }
  if( flags&MEM_Real ){
    return 7;
  }
  if( flags&MEM_Str ){
    int n = pMem->n;
    assert( n>=0 );
    return ((n*2) + 13);
  }
  if( flags&MEM_Blob ){
    return (pMem->n*2 + 12);
  }
  return 0;
}

/*
** Return the length of the data corresponding to the supplied serial-type.
*/
int sqlite3VdbeSerialTypeLen(u32 serial_type){
  if( serial_type>=12 ){
    return (serial_type-12)/2;
  }else{
    static const u8 aSize[] = { 0, 1, 2, 3, 4, 6, 8, 8, 0, 0, 0, 0 };
    return aSize[serial_type];
  }
}

/*
** Write the serialized data blob for the value stored in pMem into 
** buf. It is assumed that the caller has allocated sufficient space.
** Return the number of bytes written.
*/ 
int sqlite3VdbeSerialPut(unsigned char *buf, Mem *pMem, int file_format){
  u32 serial_type = sqlite3VdbeSerialType(pMem, file_format);
  int len;

  /* Integer and Real */
  if( serial_type<=7 && serial_type>0 ){
    u64 v;
    int i;
    if( serial_type==7 ){
      v = *(u64*)&pMem->r;
    }else{
      v = *(u64*)&pMem->i;
    }
    len = i = sqlite3VdbeSerialTypeLen(serial_type);
    while( i-- ){
      buf[i] = (v&0xFF);
      v >>= 8;
    }
    return len;
  }

  /* String or blob */
  if( serial_type>=12 ){
    len = sqlite3VdbeSerialTypeLen(serial_type);
    memcpy(buf, pMem->z, len);
    return len;
  }

  /* NULL or constants 0 or 1 */
  return 0;
}

/*
** Deserialize the data blob pointed to by buf as serial type serial_type
** and store the result in pMem.  Return the number of bytes read.
*/ 
int sqlite3VdbeSerialGet(
  const unsigned char *buf,     /* Buffer to deserialize from */
  u32 serial_type,              /* Serial type to deserialize */
  Mem *pMem                     /* Memory cell to write value into */
){
  switch( serial_type ){
    case 10:   /* Reserved for future use */
    case 11:   /* Reserved for future use */
    case 0: {  /* NULL */
      pMem->flags = MEM_Null;
      break;
    }
    case 1: { /* 1-byte signed integer */
      pMem->i = (signed char)buf[0];
      pMem->flags = MEM_Int;
      return 1;
    }
    case 2: { /* 2-byte signed integer */
      pMem->i = (((signed char)buf[0])<<8) | buf[1];
      pMem->flags = MEM_Int;
      return 2;
    }
    case 3: { /* 3-byte signed integer */
      pMem->i = (((signed char)buf[0])<<16) | (buf[1]<<8) | buf[2];
      pMem->flags = MEM_Int;
      return 3;
    }
    case 4: { /* 4-byte signed integer */
      pMem->i = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
      pMem->flags = MEM_Int;
      return 4;
    }
    case 5: { /* 6-byte signed integer */
      u64 x = (((signed char)buf[0])<<8) | buf[1];
      u32 y = (buf[2]<<24) | (buf[3]<<16) | (buf[4]<<8) | buf[5];
      x = (x<<32) | y;
      pMem->i = *(i64*)&x;
      pMem->flags = MEM_Int;
      return 6;
    }
    case 6:   /* 8-byte signed integer */
    case 7: { /* IEEE floating point */
      u64 x;
      u32 y;
#if !defined(NDEBUG) && !defined(SQLITE_OMIT_FLOATING_POINT)
      /* Verify that integers and floating point values use the same
      ** byte order.  The byte order differs on some (broken) architectures.
      */
      static const u64 t1 = ((u64)0x3ff00000)<<32;
      assert( 1.0==*(double*)&t1 );
#endif

      x = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
      y = (buf[4]<<24) | (buf[5]<<16) | (buf[6]<<8) | buf[7];
      x = (x<<32) | y;
      if( serial_type==6 ){
        pMem->i = *(i64*)&x;
        pMem->flags = MEM_Int;
      }else{
        pMem->r = *(double*)&x;
        pMem->flags = MEM_Real;
      }
      return 8;
    }
    case 8:    /* Integer 0 */
    case 9: {  /* Integer 1 */
      pMem->i = serial_type-8;
      pMem->flags = MEM_Int;
      return 0;
    }
    default: {
      int len = (serial_type-12)/2;
      pMem->z = (char *)buf;
      pMem->n = len;
      pMem->xDel = 0;
      if( serial_type&0x01 ){
        pMem->flags = MEM_Str | MEM_Ephem;
      }else{
        pMem->flags = MEM_Blob | MEM_Ephem;
      }
      return len;
    }
  }
  return 0;
}

/*
** The header of a record consists of a sequence variable-length integers.
** These integers are almost always small and are encoded as a single byte.
** The following macro takes advantage this fact to provide a fast decode
** of the integers in a record header.  It is faster for the common case
** where the integer is a single byte.  It is a little slower when the
** integer is two or more bytes.  But overall it is faster.
**
** The following expressions are equivalent:
**
**     x = sqlite3GetVarint32( A, &B );
**
**     x = GetVarint( A, B );
**
*/
#define GetVarint(A,B)  ((B = *(A))<=0x7f ? 1 : sqlite3GetVarint32(A, &B))

/*
** This function compares the two table rows or index records specified by 
** {nKey1, pKey1} and {nKey2, pKey2}, returning a negative, zero
** or positive integer if {nKey1, pKey1} is less than, equal to or 
** greater than {nKey2, pKey2}.  Both Key1 and Key2 must be byte strings
** composed by the OP_MakeRecord opcode of the VDBE.
*/
int sqlite3VdbeRecordCompare(
  void *userData,
  int nKey1, const void *pKey1, 
  int nKey2, const void *pKey2
){
  KeyInfo *pKeyInfo = (KeyInfo*)userData;
  u32 d1, d2;          /* Offset into aKey[] of next data element */
  u32 idx1, idx2;      /* Offset into aKey[] of next header element */
  u32 szHdr1, szHdr2;  /* Number of bytes in header */
  int i = 0;
  int nField;
  int rc = 0;
  const unsigned char *aKey1 = (const unsigned char *)pKey1;
  const unsigned char *aKey2 = (const unsigned char *)pKey2;

  Mem mem1;
  Mem mem2;
  mem1.enc = pKeyInfo->enc;
  mem2.enc = pKeyInfo->enc;
  
  idx1 = GetVarint(aKey1, szHdr1);
  d1 = szHdr1;
  idx2 = GetVarint(aKey2, szHdr2);
  d2 = szHdr2;
  nField = pKeyInfo->nField;
  while( idx1<szHdr1 && idx2<szHdr2 ){
    u32 serial_type1;
    u32 serial_type2;

    /* Read the serial types for the next element in each key. */
    idx1 += GetVarint( aKey1+idx1, serial_type1 );
    if( d1>=nKey1 && sqlite3VdbeSerialTypeLen(serial_type1)>0 ) break;
    idx2 += GetVarint( aKey2+idx2, serial_type2 );
    if( d2>=nKey2 && sqlite3VdbeSerialTypeLen(serial_type2)>0 ) break;

    /* Assert that there is enough space left in each key for the blob of
    ** data to go with the serial type just read. This assert may fail if
    ** the file is corrupted.  Then read the value from each key into mem1
    ** and mem2 respectively.
    */
    d1 += sqlite3VdbeSerialGet(&aKey1[d1], serial_type1, &mem1);
    d2 += sqlite3VdbeSerialGet(&aKey2[d2], serial_type2, &mem2);

    rc = sqlite3MemCompare(&mem1, &mem2, i<nField ? pKeyInfo->aColl[i] : 0);
    if( mem1.flags & MEM_Dyn ) sqlite3VdbeMemRelease(&mem1);
    if( mem2.flags & MEM_Dyn ) sqlite3VdbeMemRelease(&mem2);
    if( rc!=0 ){
      break;
    }
    i++;
  }

  /* One of the keys ran out of fields, but all the fields up to that point
  ** were equal. If the incrKey flag is true, then the second key is
  ** treated as larger.
  */
  if( rc==0 ){
    if( pKeyInfo->incrKey ){
      rc = -1;
    }else if( d1<nKey1 ){
      rc = 1;
    }else if( d2<nKey2 ){
      rc = -1;
    }
  }else if( pKeyInfo->aSortOrder && i<pKeyInfo->nField
               && pKeyInfo->aSortOrder[i] ){
    rc = -rc;
  }

  return rc;
}

/*
** The argument is an index entry composed using the OP_MakeRecord opcode.
** The last entry in this record should be an integer (specifically
** an integer rowid).  This routine returns the number of bytes in
** that integer.
*/
int sqlite3VdbeIdxRowidLen(const u8 *aKey){
  u32 szHdr;        /* Size of the header */
  u32 typeRowid;    /* Serial type of the rowid */

  sqlite3GetVarint32(aKey, &szHdr);
  sqlite3GetVarint32(&aKey[szHdr-1], &typeRowid);
  return sqlite3VdbeSerialTypeLen(typeRowid);
}
  

/*
** pCur points at an index entry created using the OP_MakeRecord opcode.
** Read the rowid (the last field in the record) and store it in *rowid.
** Return SQLITE_OK if everything works, or an error code otherwise.
*/
int sqlite3VdbeIdxRowid(BtCursor *pCur, i64 *rowid){
  i64 nCellKey;
  int rc;
  u32 szHdr;        /* Size of the header */
  u32 typeRowid;    /* Serial type of the rowid */
  u32 lenRowid;     /* Size of the rowid */
  Mem m, v;

  sqlite3BtreeKeySize(pCur, &nCellKey);
  if( nCellKey<=0 ){
    return SQLITE_CORRUPT_BKPT;
  }
  rc = sqlite3VdbeMemFromBtree(pCur, 0, nCellKey, 1, &m);
  if( rc ){
    return rc;
  }
  sqlite3GetVarint32((u8*)m.z, &szHdr);
  sqlite3GetVarint32((u8*)&m.z[szHdr-1], &typeRowid);
  lenRowid = sqlite3VdbeSerialTypeLen(typeRowid);
  sqlite3VdbeSerialGet((u8*)&m.z[m.n-lenRowid], typeRowid, &v);
  *rowid = v.i;
  sqlite3VdbeMemRelease(&m);
  return SQLITE_OK;
}

/*
** Compare the key of the index entry that cursor pC is point to against
** the key string in pKey (of length nKey).  Write into *pRes a number
** that is negative, zero, or positive if pC is less than, equal to,
** or greater than pKey.  Return SQLITE_OK on success.
**
** pKey is either created without a rowid or is truncated so that it
** omits the rowid at the end.  The rowid at the end of the index entry
** is ignored as well.
*/
int sqlite3VdbeIdxKeyCompare(
  Cursor *pC,                 /* The cursor to compare against */
  int nKey, const u8 *pKey,   /* The key to compare */
  int *res                    /* Write the comparison result here */
){
  i64 nCellKey;
  int rc;
  BtCursor *pCur = pC->pCursor;
  int lenRowid;
  Mem m;

  sqlite3BtreeKeySize(pCur, &nCellKey);
  if( nCellKey<=0 ){
    *res = 0;
    return SQLITE_OK;
  }
  rc = sqlite3VdbeMemFromBtree(pC->pCursor, 0, nCellKey, 1, &m);
  if( rc ){
    return rc;
  }
  lenRowid = sqlite3VdbeIdxRowidLen((u8*)m.z);
  *res = sqlite3VdbeRecordCompare(pC->pKeyInfo, m.n-lenRowid, m.z, nKey, pKey);
  sqlite3VdbeMemRelease(&m);
  return SQLITE_OK;
}

/*
** This routine sets the value to be returned by subsequent calls to
** sqlite3_changes() on the database handle 'db'. 
*/
void sqlite3VdbeSetChanges(sqlite3 *db, int nChange){
  db->nChange = nChange;
  db->nTotalChange += nChange;
}

/*
** Set a flag in the vdbe to update the change counter when it is finalised
** or reset.
*/
void sqlite3VdbeCountChanges(Vdbe *v){
  v->changeCntOn = 1;
}

/*
** Mark every prepared statement associated with a database connection
** as expired.
**
** An expired statement means that recompilation of the statement is
** recommend.  Statements expire when things happen that make their
** programs obsolete.  Removing user-defined functions or collating
** sequences, or changing an authorization function are the types of
** things that make prepared statements obsolete.
*/
void sqlite3ExpirePreparedStatements(sqlite3 *db){
  Vdbe *p;
  for(p = db->pVdbe; p; p=p->pNext){
    p->expired = 1;
  }
}

/*
** Return the database associated with the Vdbe.
*/
sqlite3 *sqlite3VdbeDb(Vdbe *v){
  return v->db;
}