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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** $Id: btreeInt.h,v 1.13 2007/08/30 01:19:59 drh Exp $
13**
14** This file implements a external (disk-based) database using BTrees.
15** For a detailed discussion of BTrees, refer to
16**
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.
20**
21** The basic idea is that each page of the file contains N database
22** entries and N+1 pointers to subpages.
23**
24** ----------------------------------------------------------------
25** | Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) |
26** ----------------------------------------------------------------
27**
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
32** so forth.
33**
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.
36**
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.
46**
47** FORMAT DETAILS
48**
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
53** page.
54**
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:
58**
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
73**
74** All of the integer values are big-endian (most significant byte first).
75**
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.
79**
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.
85**
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.
90**
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.
95**
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.
99**
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
107** | | v
108** |----------------|
109** | unallocated |
110** | space |
111** |----------------| ^ Grows upwards
112** | cell content | | Arbitrary order interspersed with freeblocks.
113** | area | | and free space fragments.
114** |----------------|
115**
116** The page headers looks like this:
117**
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.
125**
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
130** the payload area.
131**
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.
138**
139** Cell content is stored at the very end of the page and grows toward the
140** beginning of the page.
141**
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.
150**
151** SIZE DESCRIPTION
152** 2 Byte offset of the next freeblock
153** 2 Bytes in this freeblock
154**
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.
159**
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.
167**
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
175**
176** Variable length integers are used for rowids and to hold the number of
177** bytes of key and data in a btree cell.
178**
179** The content of a cell looks like this:
180**
181** SIZE DESCRIPTION
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.
185** * Payload
186** 4 First page of the overflow chain. Omitted if no overflow
187**
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.
191**
192** SIZE DESCRIPTION
193** 4 Page number of next overflow page
194** * Data
195**
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:
200**
201** SIZE DESCRIPTION
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
205*/
206#include "sqliteInt.h"
207#include "pager.h"
208#include "btree.h"
209#include "os.h"
210#include <assert.h>
211
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.
214*/
215#define ROUND8(x) ((x+7)&~7)
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) (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 3 bytes. Such small cells will be
225** exceedingly rare, but they are possible.
226*/
227#define MX_CELL(pBt) ((pBt->pageSize-8)/3)
228
229/* Forward declarations */
230typedef struct MemPage MemPage;
231typedef struct BtLock BtLock;
232
233/*
234** This is a magic string that appears at the beginning of every
235** SQLite database in order to identify the file as a real database.
236**
237** You can change this value at compile-time by specifying a
238** -DSQLITE_FILE_HEADER="..." on the compiler command-line. The
239** header must be exactly 16 bytes including the zero-terminator so
240** the string itself should be 15 characters long. If you change
241** the header, then your custom library will not be able to read
242** databases generated by the standard tools and the standard tools
243** will not be able to read databases created by your custom library.
244*/
245#ifndef SQLITE_FILE_HEADER /* 123456789 123456 */
246# define SQLITE_FILE_HEADER "SQLite format 3"
247#endif
248
249/*
250** Page type flags. An ORed combination of these flags appear as the
251** first byte of on-disk image of every BTree page.
252*/
253#define PTF_INTKEY 0x01
254#define PTF_ZERODATA 0x02
255#define PTF_LEAFDATA 0x04
256#define PTF_LEAF 0x08
257
258/*
259** As each page of the file is loaded into memory, an instance of the following
260** structure is appended and initialized to zero. This structure stores
261** information about the page that is decoded from the raw file page.
262**
263** The pParent field points back to the parent page. This allows us to
264** walk up the BTree from any leaf to the root. Care must be taken to
265** unref() the parent page pointer when this page is no longer referenced.
266** The pageDestructor() routine handles that chore.
267**
268** Access to all fields of this structure is controlled by the mutex
269** stored in MemPage.pBt->mutex.
270*/
271struct MemPage {
272 u8 isInit; /* True if previously initialized. MUST BE FIRST! */
273 u8 idxShift; /* True if Cell indices have changed */
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 zeroData; /* True if table stores keys only */
278 u8 leafData; /* True if tables stores data on leaves only */
279 u8 hasData; /* True if this page stores data */
280 u8 hdrOffset; /* 100 for page 1. 0 otherwise */
281 u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */
282 u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */
283 u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */
284 u16 cellOffset; /* Index in aData of first cell pointer */
285 u16 idxParent; /* Index in parent of this node */
286 u16 nFree; /* Number of free bytes on the page */
287 u16 nCell; /* Number of cells on this page, local and ovfl */
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 */
291 } aOvfl[5];
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 */
297};
298
299/*
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.
303*/
304#define EXTRA_SIZE sizeof(MemPage)
305
306/* A Btree handle
307**
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
312** this structure.
313**
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.
320**
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.
326*/
327struct Btree {
328 sqlite3 *pSqlite; /* 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 other pSqlite */
332 u8 locked; /* True if pSqlite currently has pBt locked */
333 int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */
334 Btree *pNext; /* List of other sharable Btrees from the same pSqlite */
335 Btree *pPrev; /* Back pointer of the same list */
336};
337
338/*
339** Btree.inTrans may take one of the following values.
340**
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.
344*/
345#define TRANS_NONE 0
346#define TRANS_READ 1
347#define TRANS_WRITE 2
348
349/*
350** An instance of this object represents a single database file.
351**
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.
358**
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.
365*/
366struct BtShared {
367 Pager *pPager; /* The page cache */
368 BtCursor *pCursor; /* A list of all open cursors */
369 MemPage *pPage1; /* First page of the database */
370 u8 inStmt; /* True if we are in a statement subtransaction */
371 u8 readOnly; /* True if the underlying file is readonly */
372 u8 maxEmbedFrac; /* Maximum payload as % of total page size */
373 u8 minEmbedFrac; /* Minimum payload as % of total page size */
374 u8 minLeafFrac; /* Minimum leaf payload as % of total page size */
375 u8 pageSizeFixed; /* True if the page size can no longer be changed */
376#ifndef SQLITE_OMIT_AUTOVACUUM
377 u8 autoVacuum; /* True if auto-vacuum is enabled */
378 u8 incrVacuum; /* True if incr-vacuum is enabled */
379 Pgno nTrunc; /* Non-zero if the db will be truncated (incr vacuum) */
380#endif
381 u16 pageSize; /* Total number of bytes on a page */
382 u16 usableSize; /* Number of usable bytes on each page */
383 int maxLocal; /* Maximum local payload in non-LEAFDATA tables */
384 int minLocal; /* Minimum local payload in non-LEAFDATA tables */
385 int maxLeaf; /* Maximum local payload in a LEAFDATA table */
386 int minLeaf; /* Minimum local payload in a LEAFDATA table */
387 BusyHandler *pBusyHandler; /* Callback for when there is lock contention */
388 u8 inTransaction; /* Transaction state */
389 int nTransaction; /* Number of open transactions (read + write) */
390 void *pSchema; /* Pointer to space allocated by sqlite3BtreeSchema() */
391 void (*xFreeSchema)(void*); /* Destructor for BtShared.pSchema */
392 sqlite3_mutex *mutex; /* Non-recursive mutex required to access this struct */
393#ifndef SQLITE_OMIT_SHARED_CACHE
394 int nRef; /* Number of references to this structure */
395 BtShared *pNext; /* Next on a list of sharable BtShared structs */
396 BtLock *pLock; /* List of locks held on this shared-btree struct */
397#endif
398};
399
400/*
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.
404*/
405typedef struct CellInfo CellInfo;
406struct 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 */
415};
416
417/*
418** A cursor is a pointer to a particular entry within a particular
419** b-tree within a database file.
420**
421** The entry is identified by its MemPage and the index in
422** MemPage.aCell[] of the entry.
423**
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.pSqlite.
427**
428** Fields in this structure are accessed under the BtShared.mutex
429** found at self->pBt->mutex.
430*/
431struct BtCursor {
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 int (*xCompare)(void*,int,const void*,int,const void*); /* Key comp func */
436 void *pArg; /* First arg to xCompare() */
437 Pgno pgnoRoot; /* The root page of this tree */
438 MemPage *pPage; /* Page that contains the entry */
439 int idx; /* Index of the entry in pPage->aCell[] */
440 CellInfo info; /* A parse of the cell we are pointing at */
441 u8 wrFlag; /* True if writable */
442 u8 eState; /* One of the CURSOR_XXX constants (see below) */
443 void *pKey; /* Saved key that was cursor's last known position */
444 i64 nKey; /* Size of pKey, or last integer key */
445 int skip; /* (skip<0) -> Prev() is a no-op. (skip>0) -> Next() is */
446#ifndef SQLITE_OMIT_INCRBLOB
447 u8 isIncrblobHandle; /* True if this cursor is an incr. io handle */
448 Pgno *aOverflow; /* Cache of overflow page locations */
449#endif
450};
451
452/*
453** Potential values for BtCursor.eState.
454**
455** CURSOR_VALID:
456** Cursor points to a valid entry. getPayload() etc. may be called.
457**
458** CURSOR_INVALID:
459** Cursor does not point to a valid entry. This can happen (for example)
460** because the table is empty or because BtreeCursorFirst() has not been
461** called.
462**
463** CURSOR_REQUIRESEEK:
464** The table that this cursor was opened on still exists, but has been
465** modified since the cursor was last used. The cursor position is saved
466** in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in
467** this state, restoreOrClearCursorPosition() can be called to attempt to
468** seek the cursor to the saved position.
469**
470** CURSOR_FAULT:
471** A unrecoverable error (an I/O error or a malloc failure) has occurred
472** on a different connection that shares the BtShared cache with this
473** cursor. The error has left the cache in an inconsistent state.
474** Do nothing else with this cursor. Any attempt to use the cursor
475** should return the error code stored in BtCursor.skip
476*/
477#define CURSOR_INVALID 0
478#define CURSOR_VALID 1
479#define CURSOR_REQUIRESEEK 2
480#define CURSOR_FAULT 3
481
482/*
483** The TRACE macro will print high-level status information about the
484** btree operation when the global variable sqlite3_btree_trace is
485** enabled.
486*/
487#if SQLITE_TEST
488# define TRACE(X) if( sqlite3_btree_trace ){ printf X; fflush(stdout); }
489#else
490# define TRACE(X)
491#endif
492
493/*
494** Routines to read and write variable-length integers. These used to
495** be defined locally, but now we use the varint routines in the util.c
496** file.
497*/
498#define getVarint sqlite3GetVarint
499#define getVarint32(A,B) ((*B=*(A))<=0x7f?1:sqlite3GetVarint32(A,B))
500#define putVarint sqlite3PutVarint
501
502/* The database page the PENDING_BYTE occupies. This page is never used.
503** TODO: This macro is very similary to PAGER_MJ_PGNO() in pager.c. They
504** should possibly be consolidated (presumably in pager.h).
505**
506** If disk I/O is omitted (meaning that the database is stored purely
507** in memory) then there is no pending byte.
508*/
509#ifdef SQLITE_OMIT_DISKIO
510# define PENDING_BYTE_PAGE(pBt) 0x7fffffff
511#else
512# define PENDING_BYTE_PAGE(pBt) ((PENDING_BYTE/(pBt)->pageSize)+1)
513#endif
514
515/*
516** A linked list of the following structures is stored at BtShared.pLock.
517** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor
518** is opened on the table with root page BtShared.iTable. Locks are removed
519** from this list when a transaction is committed or rolled back, or when
520** a btree handle is closed.
521*/
522struct BtLock {
523 Btree *pBtree; /* Btree handle holding this lock */
524 Pgno iTable; /* Root page of table */
525 u8 eLock; /* READ_LOCK or WRITE_LOCK */
526 BtLock *pNext; /* Next in BtShared.pLock list */
527};
528
529/* Candidate values for BtLock.eLock */
530#define READ_LOCK 1
531#define WRITE_LOCK 2
532
533/*
534** These macros define the location of the pointer-map entry for a
535** database page. The first argument to each is the number of usable
536** bytes on each page of the database (often 1024). The second is the
537** page number to look up in the pointer map.
538**
539** PTRMAP_PAGENO returns the database page number of the pointer-map
540** page that stores the required pointer. PTRMAP_PTROFFSET returns
541** the offset of the requested map entry.
542**
543** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page,
544** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be
545** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements
546** this test.
547*/
548#define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno)
549#define PTRMAP_PTROFFSET(pBt, pgno) (5*(pgno-ptrmapPageno(pBt, pgno)-1))
550#define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno))
551
552/*
553** The pointer map is a lookup table that identifies the parent page for
554** each child page in the database file. The parent page is the page that
555** contains a pointer to the child. Every page in the database contains
556** 0 or 1 parent pages. (In this context 'database page' refers
557** to any page that is not part of the pointer map itself.) Each pointer map
558** entry consists of a single byte 'type' and a 4 byte parent page number.
559** The PTRMAP_XXX identifiers below are the valid types.
560**
561** The purpose of the pointer map is to facility moving pages from one
562** position in the file to another as part of autovacuum. When a page
563** is moved, the pointer in its parent must be updated to point to the
564** new location. The pointer map is used to locate the parent page quickly.
565**
566** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not
567** used in this case.
568**
569** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number
570** is not used in this case.
571**
572** PTRMAP_OVERFLOW1: The database page is the first page in a list of
573** overflow pages. The page number identifies the page that
574** contains the cell with a pointer to this overflow page.
575**
576** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of
577** overflow pages. The page-number identifies the previous
578** page in the overflow page list.
579**
580** PTRMAP_BTREE: The database page is a non-root btree page. The page number
581** identifies the parent page in the btree.
582*/
583#define PTRMAP_ROOTPAGE 1
584#define PTRMAP_FREEPAGE 2
585#define PTRMAP_OVERFLOW1 3
586#define PTRMAP_OVERFLOW2 4
587#define PTRMAP_BTREE 5
588
589/* A bunch of assert() statements to check the transaction state variables
590** of handle p (type Btree*) are internally consistent.
591*/
592#define btreeIntegrity(p) \
593 assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \
594 assert( p->pBt->inTransaction>=p->inTrans );
595
596
597/*
598** The ISAUTOVACUUM macro is used within balance_nonroot() to determine
599** if the database supports auto-vacuum or not. Because it is used
600** within an expression that is an argument to another macro
601** (sqliteMallocRaw), it is not possible to use conditional compilation.
602** So, this macro is defined instead.
603*/
604#ifndef SQLITE_OMIT_AUTOVACUUM
605#define ISAUTOVACUUM (pBt->autoVacuum)
606#else
607#define ISAUTOVACUUM 0
608#endif
609
610
611/*
612** This structure is passed around through all the sanity checking routines
613** in order to keep track of some global state information.
614*/
615typedef struct IntegrityCk IntegrityCk;
616struct IntegrityCk {
617 BtShared *pBt; /* The tree being checked out */
618 Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */
619 int nPage; /* Number of pages in the database */
620 int *anRef; /* Number of times each page is referenced */
621 int mxErr; /* Stop accumulating errors when this reaches zero */
622 char *zErrMsg; /* An error message. NULL if no errors seen. */
623 int nErr; /* Number of messages written to zErrMsg so far */
624};
625
626/*
627** Read or write a two- and four-byte big-endian integer values.
628*/
629#define get2byte(x) ((x)[0]<<8 | (x)[1])
630#define put2byte(p,v) ((p)[0] = (v)>>8, (p)[1] = (v))
631#define get4byte sqlite3Get4byte
632#define put4byte sqlite3Put4byte
633
634/*
635** Internal routines that should be accessed by the btree layer only.
636*/
637int sqlite3BtreeGetPage(BtShared*, Pgno, MemPage**, int);
638int sqlite3BtreeInitPage(MemPage *pPage, MemPage *pParent);
639void sqlite3BtreeParseCellPtr(MemPage*, u8*, CellInfo*);
640void sqlite3BtreeParseCell(MemPage*, int, CellInfo*);
641#ifdef SQLITE_TEST
642u8 *sqlite3BtreeFindCell(MemPage *pPage, int iCell);
643#endif
644int sqlite3BtreeRestoreOrClearCursorPosition(BtCursor *pCur);
645void sqlite3BtreeGetTempCursor(BtCursor *pCur, BtCursor *pTempCur);
646void sqlite3BtreeReleaseTempCursor(BtCursor *pCur);
647int sqlite3BtreeIsRootPage(MemPage *pPage);
648void sqlite3BtreeMoveToParent(BtCursor *pCur);
generated by cgit v1.1 at 2024-12-14 17:10:49 +0000