1 /* 2 ** 2004 April 6 3 ** 4 ** The author disclaims copyright to this source code. In place of 5 ** a legal notice, here is a blessing: 6 ** 7 ** May you do good and not evil. 8 ** May you find forgiveness for yourself and forgive others. 9 ** May you share freely, never taking more than you give. 10 ** 11 ************************************************************************* 12 ** This file implements a external (disk-based) database using BTrees. 13 ** For a detailed discussion of BTrees, refer to 14 ** 15 ** Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3: 16 ** "Sorting And Searching", pages 473-480. Addison-Wesley 17 ** Publishing Company, Reading, Massachusetts. 18 ** 19 ** The basic idea is that each page of the file contains N database 20 ** entries and N+1 pointers to subpages. 21 ** 22 ** ---------------------------------------------------------------- 23 ** | Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) | 24 ** ---------------------------------------------------------------- 25 ** 26 ** All of the keys on the page that Ptr(0) points to have values less 27 ** than Key(0). All of the keys on page Ptr(1) and its subpages have 28 ** values greater than Key(0) and less than Key(1). All of the keys 29 ** on Ptr(N) and its subpages have values greater than Key(N-1). And 30 ** so forth. 31 ** 32 ** Finding a particular key requires reading O(log(M)) pages from the 33 ** disk where M is the number of entries in the tree. 34 ** 35 ** In this implementation, a single file can hold one or more separate 36 ** BTrees. Each BTree is identified by the index of its root page. The 37 ** key and data for any entry are combined to form the "payload". A 38 ** fixed amount of payload can be carried directly on the database 39 ** page. If the payload is larger than the preset amount then surplus 40 ** bytes are stored on overflow pages. The payload for an entry 41 ** and the preceding pointer are combined to form a "Cell". Each 42 ** page has a small header which contains the Ptr(N) pointer and other 43 ** information such as the size of key and data. 44 ** 45 ** FORMAT DETAILS 46 ** 47 ** The file is divided into pages. The first page is called page 1, 48 ** the second is page 2, and so forth. A page number of zero indicates 49 ** "no such page". The page size can be any power of 2 between 512 and 65536. 50 ** Each page can be either a btree page, a freelist page, an overflow 51 ** page, or a pointer-map page. 52 ** 53 ** The first page is always a btree page. The first 100 bytes of the first 54 ** page contain a special header (the "file header") that describes the file. 55 ** The format of the file header is as follows: 56 ** 57 ** OFFSET SIZE DESCRIPTION 58 ** 0 16 Header string: "SQLite format 3\000" 59 ** 16 2 Page size in bytes. 60 ** 18 1 File format write version 61 ** 19 1 File format read version 62 ** 20 1 Bytes of unused space at the end of each page 63 ** 21 1 Max embedded payload fraction 64 ** 22 1 Min embedded payload fraction 65 ** 23 1 Min leaf payload fraction 66 ** 24 4 File change counter 67 ** 28 4 Reserved for future use 68 ** 32 4 First freelist page 69 ** 36 4 Number of freelist pages in the file 70 ** 40 60 15 4-byte meta values passed to higher layers 71 ** 72 ** 40 4 Schema cookie 73 ** 44 4 File format of schema layer 74 ** 48 4 Size of page cache 75 ** 52 4 Largest root-page (auto/incr_vacuum) 76 ** 56 4 1=UTF-8 2=UTF16le 3=UTF16be 77 ** 60 4 User version 78 ** 64 4 Incremental vacuum mode 79 ** 68 4 unused 80 ** 72 4 unused 81 ** 76 4 unused 82 ** 83 ** All of the integer values are big-endian (most significant byte first). 84 ** 85 ** The file change counter is incremented when the database is changed 86 ** This counter allows other processes to know when the file has changed 87 ** and thus when they need to flush their cache. 88 ** 89 ** The max embedded payload fraction is the amount of the total usable 90 ** space in a page that can be consumed by a single cell for standard 91 ** B-tree (non-LEAFDATA) tables. A value of 255 means 100%. The default 92 ** is to limit the maximum cell size so that at least 4 cells will fit 93 ** on one page. Thus the default max embedded payload fraction is 64. 94 ** 95 ** If the payload for a cell is larger than the max payload, then extra 96 ** payload is spilled to overflow pages. Once an overflow page is allocated, 97 ** as many bytes as possible are moved into the overflow pages without letting 98 ** the cell size drop below the min embedded payload fraction. 99 ** 100 ** The min leaf payload fraction is like the min embedded payload fraction 101 ** except that it applies to leaf nodes in a LEAFDATA tree. The maximum 102 ** payload fraction for a LEAFDATA tree is always 100% (or 255) and it 103 ** not specified in the header. 104 ** 105 ** Each btree pages is divided into three sections: The header, the 106 ** cell pointer array, and the cell content area. Page 1 also has a 100-byte 107 ** file header that occurs before the page header. 108 ** 109 ** |----------------| 110 ** | file header | 100 bytes. Page 1 only. 111 ** |----------------| 112 ** | page header | 8 bytes for leaves. 12 bytes for interior nodes 113 ** |----------------| 114 ** | cell pointer | | 2 bytes per cell. Sorted order. 115 ** | array | | Grows downward 116 ** | | v 117 ** |----------------| 118 ** | unallocated | 119 ** | space | 120 ** |----------------| ^ Grows upwards 121 ** | cell content | | Arbitrary order interspersed with freeblocks. 122 ** | area | | and free space fragments. 123 ** |----------------| 124 ** 125 ** The page headers looks like this: 126 ** 127 ** OFFSET SIZE DESCRIPTION 128 ** 0 1 Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf 129 ** 1 2 byte offset to the first freeblock 130 ** 3 2 number of cells on this page 131 ** 5 2 first byte of the cell content area 132 ** 7 1 number of fragmented free bytes 133 ** 8 4 Right child (the Ptr(N) value). Omitted on leaves. 134 ** 135 ** The flags define the format of this btree page. The leaf flag means that 136 ** this page has no children. The zerodata flag means that this page carries 137 ** only keys and no data. The intkey flag means that the key is a integer 138 ** which is stored in the key size entry of the cell header rather than in 139 ** the payload area. 140 ** 141 ** The cell pointer array begins on the first byte after the page header. 142 ** The cell pointer array contains zero or more 2-byte numbers which are 143 ** offsets from the beginning of the page to the cell content in the cell 144 ** content area. The cell pointers occur in sorted order. The system strives 145 ** to keep free space after the last cell pointer so that new cells can 146 ** be easily added without having to defragment the page. 147 ** 148 ** Cell content is stored at the very end of the page and grows toward the 149 ** beginning of the page. 150 ** 151 ** Unused space within the cell content area is collected into a linked list of 152 ** freeblocks. Each freeblock is at least 4 bytes in size. The byte offset 153 ** to the first freeblock is given in the header. Freeblocks occur in 154 ** increasing order. Because a freeblock must be at least 4 bytes in size, 155 ** any group of 3 or fewer unused bytes in the cell content area cannot 156 ** exist on the freeblock chain. A group of 3 or fewer free bytes is called 157 ** a fragment. The total number of bytes in all fragments is recorded. 158 ** in the page header at offset 7. 159 ** 160 ** SIZE DESCRIPTION 161 ** 2 Byte offset of the next freeblock 162 ** 2 Bytes in this freeblock 163 ** 164 ** Cells are of variable length. Cells are stored in the cell content area at 165 ** the end of the page. Pointers to the cells are in the cell pointer array 166 ** that immediately follows the page header. Cells is not necessarily 167 ** contiguous or in order, but cell pointers are contiguous and in order. 168 ** 169 ** Cell content makes use of variable length integers. A variable 170 ** length integer is 1 to 9 bytes where the lower 7 bits of each 171 ** byte are used. The integer consists of all bytes that have bit 8 set and 172 ** the first byte with bit 8 clear. The most significant byte of the integer 173 ** appears first. A variable-length integer may not be more than 9 bytes long. 174 ** As a special case, all 8 bytes of the 9th byte are used as data. This 175 ** allows a 64-bit integer to be encoded in 9 bytes. 176 ** 177 ** 0x00 becomes 0x00000000 178 ** 0x7f becomes 0x0000007f 179 ** 0x81 0x00 becomes 0x00000080 180 ** 0x82 0x00 becomes 0x00000100 181 ** 0x80 0x7f becomes 0x0000007f 182 ** 0x8a 0x91 0xd1 0xac 0x78 becomes 0x12345678 183 ** 0x81 0x81 0x81 0x81 0x01 becomes 0x10204081 184 ** 185 ** Variable length integers are used for rowids and to hold the number of 186 ** bytes of key and data in a btree cell. 187 ** 188 ** The content of a cell looks like this: 189 ** 190 ** SIZE DESCRIPTION 191 ** 4 Page number of the left child. Omitted if leaf flag is set. 192 ** var Number of bytes of data. Omitted if the zerodata flag is set. 193 ** var Number of bytes of key. Or the key itself if intkey flag is set. 194 ** * Payload 195 ** 4 First page of the overflow chain. Omitted if no overflow 196 ** 197 ** Overflow pages form a linked list. Each page except the last is completely 198 ** filled with data (pagesize - 4 bytes). The last page can have as little 199 ** as 1 byte of data. 200 ** 201 ** SIZE DESCRIPTION 202 ** 4 Page number of next overflow page 203 ** * Data 204 ** 205 ** Freelist pages come in two subtypes: trunk pages and leaf pages. The 206 ** file header points to the first in a linked list of trunk page. Each trunk 207 ** page points to multiple leaf pages. The content of a leaf page is 208 ** unspecified. A trunk page looks like this: 209 ** 210 ** SIZE DESCRIPTION 211 ** 4 Page number of next trunk page 212 ** 4 Number of leaf pointers on this page 213 ** * zero or more pages numbers of leaves 214 */ 215 #include "sqliteInt.h" 216 217 218 /* The following value is the maximum cell size assuming a maximum page 219 ** size give above. 220 */ 221 #define MX_CELL_SIZE(pBt) ((int)(pBt->pageSize-8)) 222 223 /* The maximum number of cells on a single page of the database. This 224 ** assumes a minimum cell size of 6 bytes (4 bytes for the cell itself 225 ** plus 2 bytes for the index to the cell in the page header). Such 226 ** small cells will be rare, but they are possible. 227 */ 228 #define MX_CELL(pBt) ((pBt->pageSize-8)/6) 229 230 /* Forward declarations */ 231 typedef struct MemPage MemPage; 232 typedef struct BtLock BtLock; 233 234 /* 235 ** This is a magic string that appears at the beginning of every 236 ** SQLite database in order to identify the file as a real database. 237 ** 238 ** You can change this value at compile-time by specifying a 239 ** -DSQLITE_FILE_HEADER="..." on the compiler command-line. The 240 ** header must be exactly 16 bytes including the zero-terminator so 241 ** the string itself should be 15 characters long. If you change 242 ** the header, then your custom library will not be able to read 243 ** databases generated by the standard tools and the standard tools 244 ** will not be able to read databases created by your custom library. 245 */ 246 #ifndef SQLITE_FILE_HEADER /* 123456789 123456 */ 247 # define SQLITE_FILE_HEADER "SQLite format 3" 248 #endif 249 250 /* 251 ** Page type flags. An ORed combination of these flags appear as the 252 ** first byte of on-disk image of every BTree page. 253 */ 254 #define PTF_INTKEY 0x01 255 #define PTF_ZERODATA 0x02 256 #define PTF_LEAFDATA 0x04 257 #define PTF_LEAF 0x08 258 259 /* 260 ** As each page of the file is loaded into memory, an instance of the following 261 ** structure is appended and initialized to zero. This structure stores 262 ** information about the page that is decoded from the raw file page. 263 ** 264 ** The pParent field points back to the parent page. This allows us to 265 ** walk up the BTree from any leaf to the root. Care must be taken to 266 ** unref() the parent page pointer when this page is no longer referenced. 267 ** The pageDestructor() routine handles that chore. 268 ** 269 ** Access to all fields of this structure is controlled by the mutex 270 ** stored in MemPage.pBt->mutex. 271 */ 272 struct MemPage { 273 u8 isInit; /* True if previously initialized. MUST BE FIRST! */ 274 u8 nOverflow; /* Number of overflow cell bodies in aCell[] */ 275 u8 intKey; /* True if intkey flag is set */ 276 u8 leaf; /* True if leaf flag is set */ 277 u8 hasData; /* True if this page stores data */ 278 u8 hdrOffset; /* 100 for page 1. 0 otherwise */ 279 u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */ 280 u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */ 281 u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */ 282 u16 cellOffset; /* Index in aData of first cell pointer */ 283 u16 nFree; /* Number of free bytes on the page */ 284 u16 nCell; /* Number of cells on this page, local and ovfl */ 285 u16 maskPage; /* Mask for page offset */ 286 struct _OvflCell { /* Cells that will not fit on aData[] */ 287 u8 *pCell; /* Pointers to the body of the overflow cell */ 288 u16 idx; /* Insert this cell before idx-th non-overflow cell */ 289 } aOvfl[5]; 290 BtShared *pBt; /* Pointer to BtShared that this page is part of */ 291 u8 *aData; /* Pointer to disk image of the page data */ 292 DbPage *pDbPage; /* Pager page handle */ 293 Pgno pgno; /* Page number for this page */ 294 }; 295 296 /* 297 ** The in-memory image of a disk page has the auxiliary information appended 298 ** to the end. EXTRA_SIZE is the number of bytes of space needed to hold 299 ** that extra information. 300 */ 301 #define EXTRA_SIZE sizeof(MemPage) 302 303 /* 304 ** A linked list of the following structures is stored at BtShared.pLock. 305 ** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor 306 ** is opened on the table with root page BtShared.iTable. Locks are removed 307 ** from this list when a transaction is committed or rolled back, or when 308 ** a btree handle is closed. 309 */ 310 struct BtLock { 311 Btree *pBtree; /* Btree handle holding this lock */ 312 Pgno iTable; /* Root page of table */ 313 u8 eLock; /* READ_LOCK or WRITE_LOCK */ 314 BtLock *pNext; /* Next in BtShared.pLock list */ 315 }; 316 317 /* Candidate values for BtLock.eLock */ 318 #define READ_LOCK 1 319 #define WRITE_LOCK 2 320 321 /* A Btree handle 322 ** 323 ** A database connection contains a pointer to an instance of 324 ** this object for every database file that it has open. This structure 325 ** is opaque to the database connection. The database connection cannot 326 ** see the internals of this structure and only deals with pointers to 327 ** this structure. 328 ** 329 ** For some database files, the same underlying database cache might be 330 ** shared between multiple connections. In that case, each connection 331 ** has it own instance of this object. But each instance of this object 332 ** points to the same BtShared object. The database cache and the 333 ** schema associated with the database file are all contained within 334 ** the BtShared object. 335 ** 336 ** All fields in this structure are accessed under sqlite3.mutex. 337 ** The pBt pointer itself may not be changed while there exists cursors 338 ** in the referenced BtShared that point back to this Btree since those 339 ** cursors have to go through this Btree to find their BtShared and 340 ** they often do so without holding sqlite3.mutex. 341 */ 342 struct Btree { 343 sqlite3 *db; /* The database connection holding this btree */ 344 BtShared *pBt; /* Sharable content of this btree */ 345 u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */ 346 u8 sharable; /* True if we can share pBt with another db */ 347 u8 locked; /* True if db currently has pBt locked */ 348 int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */ 349 int nBackup; /* Number of backup operations reading this btree */ 350 Btree *pNext; /* List of other sharable Btrees from the same db */ 351 Btree *pPrev; /* Back pointer of the same list */ 352 #ifndef SQLITE_OMIT_SHARED_CACHE 353 BtLock lock; /* Object used to lock page 1 */ 354 #endif 355 }; 356 357 /* 358 ** Btree.inTrans may take one of the following values. 359 ** 360 ** If the shared-data extension is enabled, there may be multiple users 361 ** of the Btree structure. At most one of these may open a write transaction, 362 ** but any number may have active read transactions. 363 */ 364 #define TRANS_NONE 0 365 #define TRANS_READ 1 366 #define TRANS_WRITE 2 367 368 /* 369 ** An instance of this object represents a single database file. 370 ** 371 ** A single database file can be in use as the same time by two 372 ** or more database connections. When two or more connections are 373 ** sharing the same database file, each connection has it own 374 ** private Btree object for the file and each of those Btrees points 375 ** to this one BtShared object. BtShared.nRef is the number of 376 ** connections currently sharing this database file. 377 ** 378 ** Fields in this structure are accessed under the BtShared.mutex 379 ** mutex, except for nRef and pNext which are accessed under the 380 ** global SQLITE_MUTEX_STATIC_MASTER mutex. The pPager field 381 ** may not be modified once it is initially set as long as nRef>0. 382 ** The pSchema field may be set once under BtShared.mutex and 383 ** thereafter is unchanged as long as nRef>0. 384 ** 385 ** isPending: 386 ** 387 ** If a BtShared client fails to obtain a write-lock on a database 388 ** table (because there exists one or more read-locks on the table), 389 ** the shared-cache enters 'pending-lock' state and isPending is 390 ** set to true. 391 ** 392 ** The shared-cache leaves the 'pending lock' state when either of 393 ** the following occur: 394 ** 395 ** 1) The current writer (BtShared.pWriter) concludes its transaction, OR 396 ** 2) The number of locks held by other connections drops to zero. 397 ** 398 ** while in the 'pending-lock' state, no connection may start a new 399 ** transaction. 400 ** 401 ** This feature is included to help prevent writer-starvation. 402 */ 403 struct BtShared { 404 Pager *pPager; /* The page cache */ 405 sqlite3 *db; /* Database connection currently using this Btree */ 406 BtCursor *pCursor; /* A list of all open cursors */ 407 MemPage *pPage1; /* First page of the database */ 408 u8 readOnly; /* True if the underlying file is readonly */ 409 u8 pageSizeFixed; /* True if the page size can no longer be changed */ 410 u8 secureDelete; /* True if secure_delete is enabled */ 411 u8 initiallyEmpty; /* Database is empty at start of transaction */ 412 u8 openFlags; /* Flags to sqlite3BtreeOpen() */ 413 #ifndef SQLITE_OMIT_AUTOVACUUM 414 u8 autoVacuum; /* True if auto-vacuum is enabled */ 415 u8 incrVacuum; /* True if incr-vacuum is enabled */ 416 #endif 417 u8 inTransaction; /* Transaction state */ 418 u8 doNotUseWAL; /* If true, do not open write-ahead-log file */ 419 u16 maxLocal; /* Maximum local payload in non-LEAFDATA tables */ 420 u16 minLocal; /* Minimum local payload in non-LEAFDATA tables */ 421 u16 maxLeaf; /* Maximum local payload in a LEAFDATA table */ 422 u16 minLeaf; /* Minimum local payload in a LEAFDATA table */ 423 u32 pageSize; /* Total number of bytes on a page */ 424 u32 usableSize; /* Number of usable bytes on each page */ 425 int nTransaction; /* Number of open transactions (read + write) */ 426 u32 nPage; /* Number of pages in the database */ 427 void *pSchema; /* Pointer to space allocated by sqlite3BtreeSchema() */ 428 void (*xFreeSchema)(void*); /* Destructor for BtShared.pSchema */ 429 sqlite3_mutex *mutex; /* Non-recursive mutex required to access this object */ 430 Bitvec *pHasContent; /* Set of pages moved to free-list this transaction */ 431 #ifndef SQLITE_OMIT_SHARED_CACHE 432 int nRef; /* Number of references to this structure */ 433 BtShared *pNext; /* Next on a list of sharable BtShared structs */ 434 BtLock *pLock; /* List of locks held on this shared-btree struct */ 435 Btree *pWriter; /* Btree with currently open write transaction */ 436 u8 isExclusive; /* True if pWriter has an EXCLUSIVE lock on the db */ 437 u8 isPending; /* If waiting for read-locks to clear */ 438 #endif 439 u8 *pTmpSpace; /* BtShared.pageSize bytes of space for tmp use */ 440 }; 441 442 /* 443 ** An instance of the following structure is used to hold information 444 ** about a cell. The parseCellPtr() function fills in this structure 445 ** based on information extract from the raw disk page. 446 */ 447 typedef struct CellInfo CellInfo; 448 struct CellInfo { 449 i64 nKey; /* The key for INTKEY tables, or number of bytes in key */ 450 u8 *pCell; /* Pointer to the start of cell content */ 451 u32 nData; /* Number of bytes of data */ 452 u32 nPayload; /* Total amount of payload */ 453 u16 nHeader; /* Size of the cell content header in bytes */ 454 u16 nLocal; /* Amount of payload held locally */ 455 u16 iOverflow; /* Offset to overflow page number. Zero if no overflow */ 456 u16 nSize; /* Size of the cell content on the main b-tree page */ 457 }; 458 459 /* 460 ** Maximum depth of an SQLite B-Tree structure. Any B-Tree deeper than 461 ** this will be declared corrupt. This value is calculated based on a 462 ** maximum database size of 2^31 pages a minimum fanout of 2 for a 463 ** root-node and 3 for all other internal nodes. 464 ** 465 ** If a tree that appears to be taller than this is encountered, it is 466 ** assumed that the database is corrupt. 467 */ 468 #define BTCURSOR_MAX_DEPTH 20 469 470 /* 471 ** A cursor is a pointer to a particular entry within a particular 472 ** b-tree within a database file. 473 ** 474 ** The entry is identified by its MemPage and the index in 475 ** MemPage.aCell[] of the entry. 476 ** 477 ** A single database file can shared by two more database connections, 478 ** but cursors cannot be shared. Each cursor is associated with a 479 ** particular database connection identified BtCursor.pBtree.db. 480 ** 481 ** Fields in this structure are accessed under the BtShared.mutex 482 ** found at self->pBt->mutex. 483 */ 484 struct BtCursor { 485 Btree *pBtree; /* The Btree to which this cursor belongs */ 486 BtShared *pBt; /* The BtShared this cursor points to */ 487 BtCursor *pNext, *pPrev; /* Forms a linked list of all cursors */ 488 struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */ 489 Pgno pgnoRoot; /* The root page of this tree */ 490 sqlite3_int64 cachedRowid; /* Next rowid cache. 0 means not valid */ 491 CellInfo info; /* A parse of the cell we are pointing at */ 492 i64 nKey; /* Size of pKey, or last integer key */ 493 void *pKey; /* Saved key that was cursor's last known position */ 494 int skipNext; /* Prev() is noop if negative. Next() is noop if positive */ 495 u8 wrFlag; /* True if writable */ 496 u8 atLast; /* Cursor pointing to the last entry */ 497 u8 validNKey; /* True if info.nKey is valid */ 498 u8 eState; /* One of the CURSOR_XXX constants (see below) */ 499 #ifndef SQLITE_OMIT_INCRBLOB 500 Pgno *aOverflow; /* Cache of overflow page locations */ 501 u8 isIncrblobHandle; /* True if this cursor is an incr. io handle */ 502 #endif 503 i16 iPage; /* Index of current page in apPage */ 504 u16 aiIdx[BTCURSOR_MAX_DEPTH]; /* Current index in apPage[i] */ 505 MemPage *apPage[BTCURSOR_MAX_DEPTH]; /* Pages from root to current page */ 506 }; 507 508 /* 509 ** Potential values for BtCursor.eState. 510 ** 511 ** CURSOR_VALID: 512 ** Cursor points to a valid entry. getPayload() etc. may be called. 513 ** 514 ** CURSOR_INVALID: 515 ** Cursor does not point to a valid entry. This can happen (for example) 516 ** because the table is empty or because BtreeCursorFirst() has not been 517 ** called. 518 ** 519 ** CURSOR_REQUIRESEEK: 520 ** The table that this cursor was opened on still exists, but has been 521 ** modified since the cursor was last used. The cursor position is saved 522 ** in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in 523 ** this state, restoreCursorPosition() can be called to attempt to 524 ** seek the cursor to the saved position. 525 ** 526 ** CURSOR_FAULT: 527 ** A unrecoverable error (an I/O error or a malloc failure) has occurred 528 ** on a different connection that shares the BtShared cache with this 529 ** cursor. The error has left the cache in an inconsistent state. 530 ** Do nothing else with this cursor. Any attempt to use the cursor 531 ** should return the error code stored in BtCursor.skip 532 */ 533 #define CURSOR_INVALID 0 534 #define CURSOR_VALID 1 535 #define CURSOR_REQUIRESEEK 2 536 #define CURSOR_FAULT 3 537 538 /* 539 ** The database page the PENDING_BYTE occupies. This page is never used. 540 */ 541 # define PENDING_BYTE_PAGE(pBt) PAGER_MJ_PGNO(pBt) 542 543 /* 544 ** These macros define the location of the pointer-map entry for a 545 ** database page. The first argument to each is the number of usable 546 ** bytes on each page of the database (often 1024). The second is the 547 ** page number to look up in the pointer map. 548 ** 549 ** PTRMAP_PAGENO returns the database page number of the pointer-map 550 ** page that stores the required pointer. PTRMAP_PTROFFSET returns 551 ** the offset of the requested map entry. 552 ** 553 ** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page, 554 ** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be 555 ** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements 556 ** this test. 557 */ 558 #define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno) 559 #define PTRMAP_PTROFFSET(pgptrmap, pgno) (5*(pgno-pgptrmap-1)) 560 #define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno)) 561 562 /* 563 ** The pointer map is a lookup table that identifies the parent page for 564 ** each child page in the database file. The parent page is the page that 565 ** contains a pointer to the child. Every page in the database contains 566 ** 0 or 1 parent pages. (In this context 'database page' refers 567 ** to any page that is not part of the pointer map itself.) Each pointer map 568 ** entry consists of a single byte 'type' and a 4 byte parent page number. 569 ** The PTRMAP_XXX identifiers below are the valid types. 570 ** 571 ** The purpose of the pointer map is to facility moving pages from one 572 ** position in the file to another as part of autovacuum. When a page 573 ** is moved, the pointer in its parent must be updated to point to the 574 ** new location. The pointer map is used to locate the parent page quickly. 575 ** 576 ** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not 577 ** used in this case. 578 ** 579 ** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number 580 ** is not used in this case. 581 ** 582 ** PTRMAP_OVERFLOW1: The database page is the first page in a list of 583 ** overflow pages. The page number identifies the page that 584 ** contains the cell with a pointer to this overflow page. 585 ** 586 ** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of 587 ** overflow pages. The page-number identifies the previous 588 ** page in the overflow page list. 589 ** 590 ** PTRMAP_BTREE: The database page is a non-root btree page. The page number 591 ** identifies the parent page in the btree. 592 */ 593 #define PTRMAP_ROOTPAGE 1 594 #define PTRMAP_FREEPAGE 2 595 #define PTRMAP_OVERFLOW1 3 596 #define PTRMAP_OVERFLOW2 4 597 #define PTRMAP_BTREE 5 598 599 /* A bunch of assert() statements to check the transaction state variables 600 ** of handle p (type Btree*) are internally consistent. 601 */ 602 #define btreeIntegrity(p) \ 603 assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \ 604 assert( p->pBt->inTransaction>=p->inTrans ); 605 606 607 /* 608 ** The ISAUTOVACUUM macro is used within balance_nonroot() to determine 609 ** if the database supports auto-vacuum or not. Because it is used 610 ** within an expression that is an argument to another macro 611 ** (sqliteMallocRaw), it is not possible to use conditional compilation. 612 ** So, this macro is defined instead. 613 */ 614 #ifndef SQLITE_OMIT_AUTOVACUUM 615 #define ISAUTOVACUUM (pBt->autoVacuum) 616 #else 617 #define ISAUTOVACUUM 0 618 #endif 619 620 621 /* 622 ** This structure is passed around through all the sanity checking routines 623 ** in order to keep track of some global state information. 624 */ 625 typedef struct IntegrityCk IntegrityCk; 626 struct IntegrityCk { 627 BtShared *pBt; /* The tree being checked out */ 628 Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */ 629 Pgno nPage; /* Number of pages in the database */ 630 int *anRef; /* Number of times each page is referenced */ 631 int mxErr; /* Stop accumulating errors when this reaches zero */ 632 int nErr; /* Number of messages written to zErrMsg so far */ 633 int mallocFailed; /* A memory allocation error has occurred */ 634 StrAccum errMsg; /* Accumulate the error message text here */ 635 }; 636 637 /* 638 ** Read or write a two- and four-byte big-endian integer values. 639 */ 640 #define get2byte(x) ((x)[0]<<8 | (x)[1]) 641 #define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v)) 642 #define get4byte sqlite3Get4byte 643 #define put4byte sqlite3Put4byte 644
