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 */ 231typedef struct MemPage MemPage; 232typedef 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*/ 272struct 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*/ 310struct 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*/ 342struct 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*/ 403struct 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*/ 447typedef struct CellInfo CellInfo; 448struct 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*/ 484struct 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*/ 625typedef struct IntegrityCk IntegrityCk; 626struct 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