4 ** The author disclaims copyright to this source code. In place of
5 ** a legal notice, here is a blessing:
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.
11 *************************************************************************
12 ** $Id: btreeInt.h,v 1.30 2008/08/01 20:10:08 drh Exp $
14 ** This file implements a external (disk-based) database using BTrees.
15 ** For a detailed discussion of BTrees, refer to
17 ** Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
18 ** "Sorting And Searching", pages 473-480. Addison-Wesley
19 ** Publishing Company, Reading, Massachusetts.
21 ** The basic idea is that each page of the file contains N database
22 ** entries and N+1 pointers to subpages.
24 ** ----------------------------------------------------------------
25 ** | Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) |
26 ** ----------------------------------------------------------------
28 ** All of the keys on the page that Ptr(0) points to have values less
29 ** than Key(0). All of the keys on page Ptr(1) and its subpages have
30 ** values greater than Key(0) and less than Key(1). All of the keys
31 ** on Ptr(N) and its subpages have values greater than Key(N-1). And
34 ** Finding a particular key requires reading O(log(M)) pages from the
35 ** disk where M is the number of entries in the tree.
37 ** In this implementation, a single file can hold one or more separate
38 ** BTrees. Each BTree is identified by the index of its root page. The
39 ** key and data for any entry are combined to form the "payload". A
40 ** fixed amount of payload can be carried directly on the database
41 ** page. If the payload is larger than the preset amount then surplus
42 ** bytes are stored on overflow pages. The payload for an entry
43 ** and the preceding pointer are combined to form a "Cell". Each
44 ** page has a small header which contains the Ptr(N) pointer and other
45 ** information such as the size of key and data.
49 ** The file is divided into pages. The first page is called page 1,
50 ** the second is page 2, and so forth. A page number of zero indicates
51 ** "no such page". The page size can be anything between 512 and 65536.
52 ** Each page can be either a btree page, a freelist page or an overflow
55 ** The first page is always a btree page. The first 100 bytes of the first
56 ** page contain a special header (the "file header") that describes the file.
57 ** The format of the file header is as follows:
59 ** OFFSET SIZE DESCRIPTION
60 ** 0 16 Header string: "SQLite format 3\000"
61 ** 16 2 Page size in bytes.
62 ** 18 1 File format write version
63 ** 19 1 File format read version
64 ** 20 1 Bytes of unused space at the end of each page
65 ** 21 1 Max embedded payload fraction
66 ** 22 1 Min embedded payload fraction
67 ** 23 1 Min leaf payload fraction
68 ** 24 4 File change counter
69 ** 28 4 Reserved for future use
70 ** 32 4 First freelist page
71 ** 36 4 Number of freelist pages in the file
72 ** 40 60 15 4-byte meta values passed to higher layers
74 ** All of the integer values are big-endian (most significant byte first).
76 ** The file change counter is incremented when the database is changed
77 ** This counter allows other processes to know when the file has changed
78 ** and thus when they need to flush their cache.
80 ** The max embedded payload fraction is the amount of the total usable
81 ** space in a page that can be consumed by a single cell for standard
82 ** B-tree (non-LEAFDATA) tables. A value of 255 means 100%. The default
83 ** is to limit the maximum cell size so that at least 4 cells will fit
84 ** on one page. Thus the default max embedded payload fraction is 64.
86 ** If the payload for a cell is larger than the max payload, then extra
87 ** payload is spilled to overflow pages. Once an overflow page is allocated,
88 ** as many bytes as possible are moved into the overflow pages without letting
89 ** the cell size drop below the min embedded payload fraction.
91 ** The min leaf payload fraction is like the min embedded payload fraction
92 ** except that it applies to leaf nodes in a LEAFDATA tree. The maximum
93 ** payload fraction for a LEAFDATA tree is always 100% (or 255) and it
94 ** not specified in the header.
96 ** Each btree pages is divided into three sections: The header, the
97 ** cell pointer array, and the cell content area. Page 1 also has a 100-byte
98 ** file header that occurs before the page header.
100 ** |----------------|
101 ** | file header | 100 bytes. Page 1 only.
102 ** |----------------|
103 ** | page header | 8 bytes for leaves. 12 bytes for interior nodes
104 ** |----------------|
105 ** | cell pointer | | 2 bytes per cell. Sorted order.
106 ** | array | | Grows downward
108 ** |----------------|
111 ** |----------------| ^ Grows upwards
112 ** | cell content | | Arbitrary order interspersed with freeblocks.
113 ** | area | | and free space fragments.
114 ** |----------------|
116 ** The page headers looks like this:
118 ** OFFSET SIZE DESCRIPTION
119 ** 0 1 Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf
120 ** 1 2 byte offset to the first freeblock
121 ** 3 2 number of cells on this page
122 ** 5 2 first byte of the cell content area
123 ** 7 1 number of fragmented free bytes
124 ** 8 4 Right child (the Ptr(N) value). Omitted on leaves.
126 ** The flags define the format of this btree page. The leaf flag means that
127 ** this page has no children. The zerodata flag means that this page carries
128 ** only keys and no data. The intkey flag means that the key is a integer
129 ** which is stored in the key size entry of the cell header rather than in
132 ** The cell pointer array begins on the first byte after the page header.
133 ** The cell pointer array contains zero or more 2-byte numbers which are
134 ** offsets from the beginning of the page to the cell content in the cell
135 ** content area. The cell pointers occur in sorted order. The system strives
136 ** to keep free space after the last cell pointer so that new cells can
137 ** be easily added without having to defragment the page.
139 ** Cell content is stored at the very end of the page and grows toward the
140 ** beginning of the page.
142 ** Unused space within the cell content area is collected into a linked list of
143 ** freeblocks. Each freeblock is at least 4 bytes in size. The byte offset
144 ** to the first freeblock is given in the header. Freeblocks occur in
145 ** increasing order. Because a freeblock must be at least 4 bytes in size,
146 ** any group of 3 or fewer unused bytes in the cell content area cannot
147 ** exist on the freeblock chain. A group of 3 or fewer free bytes is called
148 ** a fragment. The total number of bytes in all fragments is recorded.
149 ** in the page header at offset 7.
152 ** 2 Byte offset of the next freeblock
153 ** 2 Bytes in this freeblock
155 ** Cells are of variable length. Cells are stored in the cell content area at
156 ** the end of the page. Pointers to the cells are in the cell pointer array
157 ** that immediately follows the page header. Cells is not necessarily
158 ** contiguous or in order, but cell pointers are contiguous and in order.
160 ** Cell content makes use of variable length integers. A variable
161 ** length integer is 1 to 9 bytes where the lower 7 bits of each
162 ** byte are used. The integer consists of all bytes that have bit 8 set and
163 ** the first byte with bit 8 clear. The most significant byte of the integer
164 ** appears first. A variable-length integer may not be more than 9 bytes long.
165 ** As a special case, all 8 bytes of the 9th byte are used as data. This
166 ** allows a 64-bit integer to be encoded in 9 bytes.
168 ** 0x00 becomes 0x00000000
169 ** 0x7f becomes 0x0000007f
170 ** 0x81 0x00 becomes 0x00000080
171 ** 0x82 0x00 becomes 0x00000100
172 ** 0x80 0x7f becomes 0x0000007f
173 ** 0x8a 0x91 0xd1 0xac 0x78 becomes 0x12345678
174 ** 0x81 0x81 0x81 0x81 0x01 becomes 0x10204081
176 ** Variable length integers are used for rowids and to hold the number of
177 ** bytes of key and data in a btree cell.
179 ** The content of a cell looks like this:
182 ** 4 Page number of the left child. Omitted if leaf flag is set.
183 ** var Number of bytes of data. Omitted if the zerodata flag is set.
184 ** var Number of bytes of key. Or the key itself if intkey flag is set.
186 ** 4 First page of the overflow chain. Omitted if no overflow
188 ** Overflow pages form a linked list. Each page except the last is completely
189 ** filled with data (pagesize - 4 bytes). The last page can have as little
190 ** as 1 byte of data.
193 ** 4 Page number of next overflow page
196 ** Freelist pages come in two subtypes: trunk pages and leaf pages. The
197 ** file header points to the first in a linked list of trunk page. Each trunk
198 ** page points to multiple leaf pages. The content of a leaf page is
199 ** unspecified. A trunk page looks like this:
202 ** 4 Page number of next trunk page
203 ** 4 Number of leaf pointers on this page
204 ** * zero or more pages numbers of leaves
206 #include "sqliteInt.h"
212 /* Round up a number to the next larger multiple of 8. This is used
213 ** to force 8-byte alignment on 64-bit architectures.
215 #define ROUND8(x) ((x+7)&~7)
218 /* The following value is the maximum cell size assuming a maximum page
221 #define MX_CELL_SIZE(pBt) (pBt->pageSize-8)
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.
228 #define MX_CELL(pBt) ((pBt->pageSize-8)/6)
230 /* Forward declarations */
231 typedef struct MemPage MemPage;
232 typedef struct BtLock BtLock;
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.
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.
246 #ifndef SQLITE_FILE_HEADER /* 123456789 123456 */
247 # define SQLITE_FILE_HEADER "SQLite format 3"
251 ** Page type flags. An ORed combination of these flags appear as the
252 ** first byte of on-disk image of every BTree page.
254 #define PTF_INTKEY 0x01
255 #define PTF_ZERODATA 0x02
256 #define PTF_LEAFDATA 0x04
257 #define PTF_LEAF 0x08
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.
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.
269 ** Access to all fields of this structure is controlled by the mutex
270 ** stored in MemPage.pBt->mutex.
273 u8 isInit; /* True if previously initialized. MUST BE FIRST! */
274 u8 idxShift; /* True if Cell indices have changed */
275 u8 nOverflow; /* Number of overflow cell bodies in aCell[] */
276 u8 intKey; /* True if intkey flag is set */
277 u8 leaf; /* True if leaf flag is set */
278 u8 hasData; /* True if this page stores data */
279 u8 hdrOffset; /* 100 for page 1. 0 otherwise */
280 u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */
281 u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */
282 u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */
283 u16 cellOffset; /* Index in aData of first cell pointer */
284 u16 idxParent; /* Index in parent of this node */
285 u16 nFree; /* Number of free bytes on the page */
286 u16 nCell; /* Number of cells on this page, local and ovfl */
287 u16 maskPage; /* Mask for page offset */
288 struct _OvflCell { /* Cells that will not fit on aData[] */
289 u8 *pCell; /* Pointers to the body of the overflow cell */
290 u16 idx; /* Insert this cell before idx-th non-overflow cell */
292 BtShared *pBt; /* Pointer to BtShared that this page is part of */
293 u8 *aData; /* Pointer to disk image of the page data */
294 DbPage *pDbPage; /* Pager page handle */
295 Pgno pgno; /* Page number for this page */
296 MemPage *pParent; /* The parent of this page. NULL for root */
300 ** The in-memory image of a disk page has the auxiliary information appended
301 ** to the end. EXTRA_SIZE is the number of bytes of space needed to hold
302 ** that extra information.
304 #define EXTRA_SIZE sizeof(MemPage)
308 ** A database connection contains a pointer to an instance of
309 ** this object for every database file that it has open. This structure
310 ** is opaque to the database connection. The database connection cannot
311 ** see the internals of this structure and only deals with pointers to
314 ** For some database files, the same underlying database cache might be
315 ** shared between multiple connections. In that case, each contection
316 ** has it own pointer to this object. But each instance of this object
317 ** points to the same BtShared object. The database cache and the
318 ** schema associated with the database file are all contained within
319 ** the BtShared object.
321 ** All fields in this structure are accessed under sqlite3.mutex.
322 ** The pBt pointer itself may not be changed while there exists cursors
323 ** in the referenced BtShared that point back to this Btree since those
324 ** cursors have to do go through this Btree to find their BtShared and
325 ** they often do so without holding sqlite3.mutex.
328 sqlite3 *db; /* The database connection holding this btree */
329 BtShared *pBt; /* Sharable content of this btree */
330 u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
331 u8 sharable; /* True if we can share pBt with another db */
332 u8 locked; /* True if db currently has pBt locked */
333 int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */
334 Btree *pNext; /* List of other sharable Btrees from the same db */
335 Btree *pPrev; /* Back pointer of the same list */
339 ** Btree.inTrans may take one of the following values.
341 ** If the shared-data extension is enabled, there may be multiple users
342 ** of the Btree structure. At most one of these may open a write transaction,
343 ** but any number may have active read transactions.
347 #define TRANS_WRITE 2
350 ** An instance of this object represents a single database file.
352 ** A single database file can be in use as the same time by two
353 ** or more database connections. When two or more connections are
354 ** sharing the same database file, each connection has it own
355 ** private Btree object for the file and each of those Btrees points
356 ** to this one BtShared object. BtShared.nRef is the number of
357 ** connections currently sharing this database file.
359 ** Fields in this structure are accessed under the BtShared.mutex
360 ** mutex, except for nRef and pNext which are accessed under the
361 ** global SQLITE_MUTEX_STATIC_MASTER mutex. The pPager field
362 ** may not be modified once it is initially set as long as nRef>0.
363 ** The pSchema field may be set once under BtShared.mutex and
364 ** thereafter is unchanged as long as nRef>0.
367 Pager *pPager; /* The page cache */
368 sqlite3 *db; /* Database connection currently using this Btree */
369 BtCursor *pCursor; /* A list of all open cursors */
370 MemPage *pPage1; /* First page of the database */
371 u8 inStmt; /* True if we are in a statement subtransaction */
372 u8 readOnly; /* True if the underlying file is readonly */
373 u8 pageSizeFixed; /* True if the page size can no longer be changed */
374 #ifndef SQLITE_OMIT_AUTOVACUUM
375 u8 autoVacuum; /* True if auto-vacuum is enabled */
376 u8 incrVacuum; /* True if incr-vacuum is enabled */
377 Pgno nTrunc; /* Non-zero if the db will be truncated (incr vacuum) */
379 u16 pageSize; /* Total number of bytes on a page */
380 u16 usableSize; /* Number of usable bytes on each page */
381 int maxLocal; /* Maximum local payload in non-LEAFDATA tables */
382 int minLocal; /* Minimum local payload in non-LEAFDATA tables */
383 int maxLeaf; /* Maximum local payload in a LEAFDATA table */
384 int minLeaf; /* Minimum local payload in a LEAFDATA table */
385 u8 inTransaction; /* Transaction state */
386 int nTransaction; /* Number of open transactions (read + write) */
387 void *pSchema; /* Pointer to space allocated by sqlite3BtreeSchema() */
388 void (*xFreeSchema)(void*); /* Destructor for BtShared.pSchema */
389 sqlite3_mutex *mutex; /* Non-recursive mutex required to access this struct */
390 BusyHandler busyHdr; /* The busy handler for this btree */
391 #ifndef SQLITE_OMIT_SHARED_CACHE
392 int nRef; /* Number of references to this structure */
393 BtShared *pNext; /* Next on a list of sharable BtShared structs */
394 BtLock *pLock; /* List of locks held on this shared-btree struct */
395 Btree *pExclusive; /* Btree with an EXCLUSIVE lock on the whole db */
397 u8 *pTmpSpace; /* BtShared.pageSize bytes of space for tmp use */
401 ** An instance of the following structure is used to hold information
402 ** about a cell. The parseCellPtr() function fills in this structure
403 ** based on information extract from the raw disk page.
405 typedef struct CellInfo CellInfo;
407 u8 *pCell; /* Pointer to the start of cell content */
408 i64 nKey; /* The key for INTKEY tables, or number of bytes in key */
409 u32 nData; /* Number of bytes of data */
410 u32 nPayload; /* Total amount of payload */
411 u16 nHeader; /* Size of the cell content header in bytes */
412 u16 nLocal; /* Amount of payload held locally */
413 u16 iOverflow; /* Offset to overflow page number. Zero if no overflow */
414 u16 nSize; /* Size of the cell content on the main b-tree page */
418 ** A cursor is a pointer to a particular entry within a particular
419 ** b-tree within a database file.
421 ** The entry is identified by its MemPage and the index in
422 ** MemPage.aCell[] of the entry.
424 ** When a single database file can shared by two more database connections,
425 ** but cursors cannot be shared. Each cursor is associated with a
426 ** particular database connection identified BtCursor.pBtree.db.
428 ** Fields in this structure are accessed under the BtShared.mutex
429 ** found at self->pBt->mutex.
432 Btree *pBtree; /* The Btree to which this cursor belongs */
433 BtShared *pBt; /* The BtShared this cursor points to */
434 BtCursor *pNext, *pPrev; /* Forms a linked list of all cursors */
435 struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */
436 Pgno pgnoRoot; /* The root page of this tree */
437 MemPage *pPage; /* Page that contains the entry */
438 int idx; /* Index of the entry in pPage->aCell[] */
439 CellInfo info; /* A parse of the cell we are pointing at */
440 u8 wrFlag; /* True if writable */
441 u8 atLast; /* Cursor pointing to the last entry */
442 u8 validNKey; /* True if info.nKey is valid */
443 u8 eState; /* One of the CURSOR_XXX constants (see below) */
444 void *pKey; /* Saved key that was cursor's last known position */
445 i64 nKey; /* Size of pKey, or last integer key */
446 int skip; /* (skip<0) -> Prev() is a no-op. (skip>0) -> Next() is */
447 #ifndef SQLITE_OMIT_INCRBLOB
448 u8 isIncrblobHandle; /* True if this cursor is an incr. io handle */
449 Pgno *aOverflow; /* Cache of overflow page locations */
454 ** Potential values for BtCursor.eState.
457 ** Cursor points to a valid entry. getPayload() etc. may be called.
460 ** Cursor does not point to a valid entry. This can happen (for example)
461 ** because the table is empty or because BtreeCursorFirst() has not been
464 ** CURSOR_REQUIRESEEK:
465 ** The table that this cursor was opened on still exists, but has been
466 ** modified since the cursor was last used. The cursor position is saved
467 ** in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in
468 ** this state, restoreCursorPosition() can be called to attempt to
469 ** seek the cursor to the saved position.
472 ** A unrecoverable error (an I/O error or a malloc failure) has occurred
473 ** on a different connection that shares the BtShared cache with this
474 ** cursor. The error has left the cache in an inconsistent state.
475 ** Do nothing else with this cursor. Any attempt to use the cursor
476 ** should return the error code stored in BtCursor.skip
478 #define CURSOR_INVALID 0
479 #define CURSOR_VALID 1
480 #define CURSOR_REQUIRESEEK 2
481 #define CURSOR_FAULT 3
483 /* The database page the PENDING_BYTE occupies. This page is never used.
484 ** TODO: This macro is very similary to PAGER_MJ_PGNO() in pager.c. They
485 ** should possibly be consolidated (presumably in pager.h).
487 ** If disk I/O is omitted (meaning that the database is stored purely
488 ** in memory) then there is no pending byte.
490 #ifdef SQLITE_OMIT_DISKIO
491 # define PENDING_BYTE_PAGE(pBt) 0x7fffffff
493 # define PENDING_BYTE_PAGE(pBt) ((PENDING_BYTE/(pBt)->pageSize)+1)
497 ** A linked list of the following structures is stored at BtShared.pLock.
498 ** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor
499 ** is opened on the table with root page BtShared.iTable. Locks are removed
500 ** from this list when a transaction is committed or rolled back, or when
501 ** a btree handle is closed.
504 Btree *pBtree; /* Btree handle holding this lock */
505 Pgno iTable; /* Root page of table */
506 u8 eLock; /* READ_LOCK or WRITE_LOCK */
507 BtLock *pNext; /* Next in BtShared.pLock list */
510 /* Candidate values for BtLock.eLock */
515 ** These macros define the location of the pointer-map entry for a
516 ** database page. The first argument to each is the number of usable
517 ** bytes on each page of the database (often 1024). The second is the
518 ** page number to look up in the pointer map.
520 ** PTRMAP_PAGENO returns the database page number of the pointer-map
521 ** page that stores the required pointer. PTRMAP_PTROFFSET returns
522 ** the offset of the requested map entry.
524 ** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page,
525 ** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be
526 ** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements
529 #define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno)
530 #define PTRMAP_PTROFFSET(pgptrmap, pgno) (5*(pgno-pgptrmap-1))
531 #define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno))
534 ** The pointer map is a lookup table that identifies the parent page for
535 ** each child page in the database file. The parent page is the page that
536 ** contains a pointer to the child. Every page in the database contains
537 ** 0 or 1 parent pages. (In this context 'database page' refers
538 ** to any page that is not part of the pointer map itself.) Each pointer map
539 ** entry consists of a single byte 'type' and a 4 byte parent page number.
540 ** The PTRMAP_XXX identifiers below are the valid types.
542 ** The purpose of the pointer map is to facility moving pages from one
543 ** position in the file to another as part of autovacuum. When a page
544 ** is moved, the pointer in its parent must be updated to point to the
545 ** new location. The pointer map is used to locate the parent page quickly.
547 ** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not
548 ** used in this case.
550 ** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number
551 ** is not used in this case.
553 ** PTRMAP_OVERFLOW1: The database page is the first page in a list of
554 ** overflow pages. The page number identifies the page that
555 ** contains the cell with a pointer to this overflow page.
557 ** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of
558 ** overflow pages. The page-number identifies the previous
559 ** page in the overflow page list.
561 ** PTRMAP_BTREE: The database page is a non-root btree page. The page number
562 ** identifies the parent page in the btree.
564 #define PTRMAP_ROOTPAGE 1
565 #define PTRMAP_FREEPAGE 2
566 #define PTRMAP_OVERFLOW1 3
567 #define PTRMAP_OVERFLOW2 4
568 #define PTRMAP_BTREE 5
570 /* A bunch of assert() statements to check the transaction state variables
571 ** of handle p (type Btree*) are internally consistent.
573 #define btreeIntegrity(p) \
574 assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \
575 assert( p->pBt->inTransaction>=p->inTrans );
579 ** The ISAUTOVACUUM macro is used within balance_nonroot() to determine
580 ** if the database supports auto-vacuum or not. Because it is used
581 ** within an expression that is an argument to another macro
582 ** (sqliteMallocRaw), it is not possible to use conditional compilation.
583 ** So, this macro is defined instead.
585 #ifndef SQLITE_OMIT_AUTOVACUUM
586 #define ISAUTOVACUUM (pBt->autoVacuum)
588 #define ISAUTOVACUUM 0
593 ** This structure is passed around through all the sanity checking routines
594 ** in order to keep track of some global state information.
596 typedef struct IntegrityCk IntegrityCk;
598 BtShared *pBt; /* The tree being checked out */
599 Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */
600 int nPage; /* Number of pages in the database */
601 int *anRef; /* Number of times each page is referenced */
602 int mxErr; /* Stop accumulating errors when this reaches zero */
603 int nErr; /* Number of messages written to zErrMsg so far */
604 int mallocFailed; /* A memory allocation error has occurred */
605 StrAccum errMsg; /* Accumulate the error message text here */
609 ** Read or write a two- and four-byte big-endian integer values.
611 #define get2byte(x) ((x)[0]<<8 | (x)[1])
612 #define put2byte(p,v) ((p)[0] = (v)>>8, (p)[1] = (v))
613 #define get4byte sqlite3Get4byte
614 #define put4byte sqlite3Put4byte
617 ** Internal routines that should be accessed by the btree layer only.
619 int sqlite3BtreeGetPage(BtShared*, Pgno, MemPage**, int);
620 int sqlite3BtreeInitPage(MemPage *pPage, MemPage *pParent);
621 void sqlite3BtreeParseCellPtr(MemPage*, u8*, CellInfo*);
622 void sqlite3BtreeParseCell(MemPage*, int, CellInfo*);
623 int sqlite3BtreeRestoreCursorPosition(BtCursor *pCur);
624 void sqlite3BtreeGetTempCursor(BtCursor *pCur, BtCursor *pTempCur);
625 void sqlite3BtreeReleaseTempCursor(BtCursor *pCur);
626 int sqlite3BtreeIsRootPage(MemPage *pPage);
627 void sqlite3BtreeMoveToParent(BtCursor *pCur);