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 an 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. (1 means 65536)
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 (must be 64)
64** 22 1 Min embedded payload fraction (must be 32)
65** 23 1 Min leaf payload fraction (must be 32)
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 Application-ID
80** 72 20 unused
81** 92 4 The version-valid-for number
82** 96 4 SQLITE_VERSION_NUMBER
83**
84** All of the integer values are big-endian (most significant byte first).
85**
86** The file change counter is incremented when the database is changed
87** This counter allows other processes to know when the file has changed
88** and thus when they need to flush their cache.
89**
90** The max embedded payload fraction is the amount of the total usable
91** space in a page that can be consumed by a single cell for standard
92** B-tree (non-LEAFDATA) tables. A value of 255 means 100%. The default
93** is to limit the maximum cell size so that at least 4 cells will fit
94** on one page. Thus the default max embedded payload fraction is 64.
95**
96** If the payload for a cell is larger than the max payload, then extra
97** payload is spilled to overflow pages. Once an overflow page is allocated,
98** as many bytes as possible are moved into the overflow pages without letting
99** the cell size drop below the min embedded payload fraction.
100**
101** The min leaf payload fraction is like the min embedded payload fraction
102** except that it applies to leaf nodes in a LEAFDATA tree. The maximum
103** payload fraction for a LEAFDATA tree is always 100% (or 255) and it
104** not specified in the header.
105**
106** Each btree pages is divided into three sections: The header, the
107** cell pointer array, and the cell content area. Page 1 also has a 100-byte
108** file header that occurs before the page header.
109**
110** |----------------|
111** | file header | 100 bytes. Page 1 only.
112** |----------------|
113** | page header | 8 bytes for leaves. 12 bytes for interior nodes
114** |----------------|
115** | cell pointer | | 2 bytes per cell. Sorted order.
116** | array | | Grows downward
117** | | v
118** |----------------|
119** | unallocated |
120** | space |
121** |----------------| ^ Grows upwards
122** | cell content | | Arbitrary order interspersed with freeblocks.
123** | area | | and free space fragments.
124** |----------------|
125**
126** The page headers looks like this:
127**
128** OFFSET SIZE DESCRIPTION
129** 0 1 Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf
130** 1 2 byte offset to the first freeblock
131** 3 2 number of cells on this page
132** 5 2 first byte of the cell content area
133** 7 1 number of fragmented free bytes
134** 8 4 Right child (the Ptr(N) value). Omitted on leaves.
135**
136** The flags define the format of this btree page. The leaf flag means that
137** this page has no children. The zerodata flag means that this page carries
138** only keys and no data. The intkey flag means that the key is an integer
139** which is stored in the key size entry of the cell header rather than in
140** the payload area.
141**
142** The cell pointer array begins on the first byte after the page header.
143** The cell pointer array contains zero or more 2-byte numbers which are
144** offsets from the beginning of the page to the cell content in the cell
145** content area. The cell pointers occur in sorted order. The system strives
146** to keep free space after the last cell pointer so that new cells can
147** be easily added without having to defragment the page.
148**
149** Cell content is stored at the very end of the page and grows toward the
150** beginning of the page.
151**
152** Unused space within the cell content area is collected into a linked list of
153** freeblocks. Each freeblock is at least 4 bytes in size. The byte offset
154** to the first freeblock is given in the header. Freeblocks occur in
155** increasing order. Because a freeblock must be at least 4 bytes in size,
156** any group of 3 or fewer unused bytes in the cell content area cannot
157** exist on the freeblock chain. A group of 3 or fewer free bytes is called
158** a fragment. The total number of bytes in all fragments is recorded.
159** in the page header at offset 7.
160**
161** SIZE DESCRIPTION
162** 2 Byte offset of the next freeblock
163** 2 Bytes in this freeblock
164**
165** Cells are of variable length. Cells are stored in the cell content area at
166** the end of the page. Pointers to the cells are in the cell pointer array
167** that immediately follows the page header. Cells is not necessarily
168** contiguous or in order, but cell pointers are contiguous and in order.
169**
170** Cell content makes use of variable length integers. A variable
171** length integer is 1 to 9 bytes where the lower 7 bits of each
172** byte are used. The integer consists of all bytes that have bit 8 set and
173** the first byte with bit 8 clear. The most significant byte of the integer
174** appears first. A variable-length integer may not be more than 9 bytes long.
175** As a special case, all 8 bytes of the 9th byte are used as data. This
176** allows a 64-bit integer to be encoded in 9 bytes.
177**
178** 0x00 becomes 0x00000000
179** 0x7f becomes 0x0000007f
180** 0x81 0x00 becomes 0x00000080
181** 0x82 0x00 becomes 0x00000100
182** 0x80 0x7f becomes 0x0000007f
183** 0x8a 0x91 0xd1 0xac 0x78 becomes 0x12345678
184** 0x81 0x81 0x81 0x81 0x01 becomes 0x10204081
185**
186** Variable length integers are used for rowids and to hold the number of
187** bytes of key and data in a btree cell.
188**
189** The content of a cell looks like this:
190**
191** SIZE DESCRIPTION
192** 4 Page number of the left child. Omitted if leaf flag is set.
193** var Number of bytes of data. Omitted if the zerodata flag is set.
194** var Number of bytes of key. Or the key itself if intkey flag is set.
195** * Payload
196** 4 First page of the overflow chain. Omitted if no overflow
197**
198** Overflow pages form a linked list. Each page except the last is completely
199** filled with data (pagesize - 4 bytes). The last page can have as little
200** as 1 byte of data.
201**
202** SIZE DESCRIPTION
203** 4 Page number of next overflow page
204** * Data
205**
206** Freelist pages come in two subtypes: trunk pages and leaf pages. The
207** file header points to the first in a linked list of trunk page. Each trunk
208** page points to multiple leaf pages. The content of a leaf page is
209** unspecified. A trunk page looks like this:
210**
211** SIZE DESCRIPTION
212** 4 Page number of next trunk page
213** 4 Number of leaf pointers on this page
214** * zero or more pages numbers of leaves
215*/
216#include "sqliteInt.h"
217
218
219/* The following value is the maximum cell size assuming a maximum page
220** size give above.
221*/
222#define MX_CELL_SIZE(pBt) ((int)(pBt->pageSize-8))
223
224/* The maximum number of cells on a single page of the database. This
225** assumes a minimum cell size of 6 bytes (4 bytes for the cell itself
226** plus 2 bytes for the index to the cell in the page header). Such
227** small cells will be rare, but they are possible.
228*/
229#define MX_CELL(pBt) ((pBt->pageSize-8)/6)
230
231/* Forward declarations */
232typedef struct MemPage MemPage;
233typedef struct BtLock BtLock;
234typedef struct CellInfo CellInfo;
235
236/*
237** This is a magic string that appears at the beginning of every
238** SQLite database in order to identify the file as a real database.
239**
240** You can change this value at compile-time by specifying a
241** -DSQLITE_FILE_HEADER="..." on the compiler command-line. The
242** header must be exactly 16 bytes including the zero-terminator so
243** the string itself should be 15 characters long. If you change
244** the header, then your custom library will not be able to read
245** databases generated by the standard tools and the standard tools
246** will not be able to read databases created by your custom library.
247*/
248#ifndef SQLITE_FILE_HEADER /* 123456789 123456 */
249# define SQLITE_FILE_HEADER "SQLite format 3"
250#endif
251
252/*
253** Page type flags. An ORed combination of these flags appear as the
254** first byte of on-disk image of every BTree page.
255*/
256#define PTF_INTKEY 0x01
257#define PTF_ZERODATA 0x02
258#define PTF_LEAFDATA 0x04
259#define PTF_LEAF 0x08
260
261/*
262** An instance of this object stores information about each a single database
263** page that has been loaded into memory. The information in this object
264** is derived from the raw on-disk page content.
265**
266** As each database page is loaded into memory, the pager allocats an
267** instance of this object and zeros the first 8 bytes. (This is the
268** "extra" information associated with each page of the pager.)
269**
270** Access to all fields of this structure is controlled by the mutex
271** stored in MemPage.pBt->mutex.
272*/
273struct MemPage {
274 u8 isInit; /* True if previously initialized. MUST BE FIRST! */
275 u8 intKey; /* True if table b-trees. False for index b-trees */
276 u8 intKeyLeaf; /* True if the leaf of an intKey table */
277 Pgno pgno; /* Page number for this page */
278 /* Only the first 8 bytes (above) are zeroed by pager.c when a new page
279 ** is allocated. All fields that follow must be initialized before use */
280 u8 leaf; /* True if a leaf page */
281 u8 hdrOffset; /* 100 for page 1. 0 otherwise */
282 u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */
283 u8 max1bytePayload; /* min(maxLocal,127) */
284 u8 nOverflow; /* Number of overflow cell bodies in aCell[] */
285 u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */
286 u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */
287 u16 cellOffset; /* Index in aData of first cell pointer */
288 int nFree; /* Number of free bytes on the page. -1 for unknown */
289 u16 nCell; /* Number of cells on this page, local and ovfl */
290 u16 maskPage; /* Mask for page offset */
291 u16 aiOvfl[4]; /* Insert the i-th overflow cell before the aiOvfl-th
292 ** non-overflow cell */
293 u8 *apOvfl[4]; /* Pointers to the body of overflow cells */
294 BtShared *pBt; /* Pointer to BtShared that this page is part of */
295 u8 *aData; /* Pointer to disk image of the page data */
296 u8 *aDataEnd; /* One byte past the end of the entire page - not just
297 ** the usable space, the entire page. Used to prevent
298 ** corruption-induced buffer overflow. */
299 u8 *aCellIdx; /* The cell index area */
300 u8 *aDataOfst; /* Same as aData for leaves. aData+4 for interior */
301 DbPage *pDbPage; /* Pager page handle */
302 u16 (*xCellSize)(MemPage*,u8*); /* cellSizePtr method */
303 void (*xParseCell)(MemPage*,u8*,CellInfo*); /* btreeParseCell method */
304};
305
306/*
307** A linked list of the following structures is stored at BtShared.pLock.
308** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor
309** is opened on the table with root page BtShared.iTable. Locks are removed
310** from this list when a transaction is committed or rolled back, or when
311** a btree handle is closed.
312*/
313struct BtLock {
314 Btree *pBtree; /* Btree handle holding this lock */
315 Pgno iTable; /* Root page of table */
316 u8 eLock; /* READ_LOCK or WRITE_LOCK */
317 BtLock *pNext; /* Next in BtShared.pLock list */
318};
319
320/* Candidate values for BtLock.eLock */
321#define READ_LOCK 1
322#define WRITE_LOCK 2
323
324/* A Btree handle
325**
326** A database connection contains a pointer to an instance of
327** this object for every database file that it has open. This structure
328** is opaque to the database connection. The database connection cannot
329** see the internals of this structure and only deals with pointers to
330** this structure.
331**
332** For some database files, the same underlying database cache might be
333** shared between multiple connections. In that case, each connection
334** has it own instance of this object. But each instance of this object
335** points to the same BtShared object. The database cache and the
336** schema associated with the database file are all contained within
337** the BtShared object.
338**
339** All fields in this structure are accessed under sqlite3.mutex.
340** The pBt pointer itself may not be changed while there exists cursors
341** in the referenced BtShared that point back to this Btree since those
342** cursors have to go through this Btree to find their BtShared and
343** they often do so without holding sqlite3.mutex.
344*/
345struct Btree {
346 sqlite3 *db; /* The database connection holding this btree */
347 BtShared *pBt; /* Sharable content of this btree */
348 u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
349 u8 sharable; /* True if we can share pBt with another db */
350 u8 locked; /* True if db currently has pBt locked */
351 u8 hasIncrblobCur; /* True if there are one or more Incrblob cursors */
352 int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */
353 int nBackup; /* Number of backup operations reading this btree */
354 u32 iBDataVersion; /* Combines with pBt->pPager->iDataVersion */
355 Btree *pNext; /* List of other sharable Btrees from the same db */
356 Btree *pPrev; /* Back pointer of the same list */
357#ifdef SQLITE_DEBUG
358 u64 nSeek; /* Calls to sqlite3BtreeMovetoUnpacked() */
359#endif
360#ifndef SQLITE_OMIT_SHARED_CACHE
361 BtLock lock; /* Object used to lock page 1 */
362#endif
363};
364
365/*
366** Btree.inTrans may take one of the following values.
367**
368** If the shared-data extension is enabled, there may be multiple users
369** of the Btree structure. At most one of these may open a write transaction,
370** but any number may have active read transactions.
371**
372** These values must match SQLITE_TXN_NONE, SQLITE_TXN_READ, and
373** SQLITE_TXN_WRITE
374*/
375#define TRANS_NONE 0
376#define TRANS_READ 1
377#define TRANS_WRITE 2
378
379#if TRANS_NONE!=SQLITE_TXN_NONE
380# error wrong numeric code for no-transaction
381#endif
382#if TRANS_READ!=SQLITE_TXN_READ
383# error wrong numeric code for read-transaction
384#endif
385#if TRANS_WRITE!=SQLITE_TXN_WRITE
386# error wrong numeric code for write-transaction
387#endif
388
389
390/*
391** An instance of this object represents a single database file.
392**
393** A single database file can be in use at the same time by two
394** or more database connections. When two or more connections are
395** sharing the same database file, each connection has it own
396** private Btree object for the file and each of those Btrees points
397** to this one BtShared object. BtShared.nRef is the number of
398** connections currently sharing this database file.
399**
400** Fields in this structure are accessed under the BtShared.mutex
401** mutex, except for nRef and pNext which are accessed under the
402** global SQLITE_MUTEX_STATIC_MAIN mutex. The pPager field
403** may not be modified once it is initially set as long as nRef>0.
404** The pSchema field may be set once under BtShared.mutex and
405** thereafter is unchanged as long as nRef>0.
406**
407** isPending:
408**
409** If a BtShared client fails to obtain a write-lock on a database
410** table (because there exists one or more read-locks on the table),
411** the shared-cache enters 'pending-lock' state and isPending is
412** set to true.
413**
414** The shared-cache leaves the 'pending lock' state when either of
415** the following occur:
416**
417** 1) The current writer (BtShared.pWriter) concludes its transaction, OR
418** 2) The number of locks held by other connections drops to zero.
419**
420** while in the 'pending-lock' state, no connection may start a new
421** transaction.
422**
423** This feature is included to help prevent writer-starvation.
424*/
425struct BtShared {
426 Pager *pPager; /* The page cache */
427 sqlite3 *db; /* Database connection currently using this Btree */
428 BtCursor *pCursor; /* A list of all open cursors */
429 MemPage *pPage1; /* First page of the database */
430 u8 openFlags; /* Flags to sqlite3BtreeOpen() */
431#ifndef SQLITE_OMIT_AUTOVACUUM
432 u8 autoVacuum; /* True if auto-vacuum is enabled */
433 u8 incrVacuum; /* True if incr-vacuum is enabled */
434 u8 bDoTruncate; /* True to truncate db on commit */
435#endif
436 u8 inTransaction; /* Transaction state */
437 u8 max1bytePayload; /* Maximum first byte of cell for a 1-byte payload */
438 u8 nReserveWanted; /* Desired number of extra bytes per page */
439 u16 btsFlags; /* Boolean parameters. See BTS_* macros below */
440 u16 maxLocal; /* Maximum local payload in non-LEAFDATA tables */
441 u16 minLocal; /* Minimum local payload in non-LEAFDATA tables */
442 u16 maxLeaf; /* Maximum local payload in a LEAFDATA table */
443 u16 minLeaf; /* Minimum local payload in a LEAFDATA table */
444 u32 pageSize; /* Total number of bytes on a page */
445 u32 usableSize; /* Number of usable bytes on each page */
446 int nTransaction; /* Number of open transactions (read + write) */
447 u32 nPage; /* Number of pages in the database */
448 void *pSchema; /* Pointer to space allocated by sqlite3BtreeSchema() */
449 void (*xFreeSchema)(void*); /* Destructor for BtShared.pSchema */
450 sqlite3_mutex *mutex; /* Non-recursive mutex required to access this object */
451 Bitvec *pHasContent; /* Set of pages moved to free-list this transaction */
452#ifndef SQLITE_OMIT_SHARED_CACHE
453 int nRef; /* Number of references to this structure */
454 BtShared *pNext; /* Next on a list of sharable BtShared structs */
455 BtLock *pLock; /* List of locks held on this shared-btree struct */
456 Btree *pWriter; /* Btree with currently open write transaction */
457#endif
458 u8 *pTmpSpace; /* Temp space sufficient to hold a single cell */
459 int nPreformatSize; /* Size of last cell written by TransferRow() */
460};
461
462/*
463** Allowed values for BtShared.btsFlags
464*/
465#define BTS_READ_ONLY 0x0001 /* Underlying file is readonly */
466#define BTS_PAGESIZE_FIXED 0x0002 /* Page size can no longer be changed */
467#define BTS_SECURE_DELETE 0x0004 /* PRAGMA secure_delete is enabled */
468#define BTS_OVERWRITE 0x0008 /* Overwrite deleted content with zeros */
469#define BTS_FAST_SECURE 0x000c /* Combination of the previous two */
470#define BTS_INITIALLY_EMPTY 0x0010 /* Database was empty at trans start */
471#define BTS_NO_WAL 0x0020 /* Do not open write-ahead-log files */
472#define BTS_EXCLUSIVE 0x0040 /* pWriter has an exclusive lock */
473#define BTS_PENDING 0x0080 /* Waiting for read-locks to clear */
474
475/*
476** An instance of the following structure is used to hold information
477** about a cell. The parseCellPtr() function fills in this structure
478** based on information extract from the raw disk page.
479*/
480struct CellInfo {
481 i64 nKey; /* The key for INTKEY tables, or nPayload otherwise */
482 u8 *pPayload; /* Pointer to the start of payload */
483 u32 nPayload; /* Bytes of payload */
484 u16 nLocal; /* Amount of payload held locally, not on overflow */
485 u16 nSize; /* Size of the cell content on the main b-tree page */
486};
487
488/*
489** Maximum depth of an SQLite B-Tree structure. Any B-Tree deeper than
490** this will be declared corrupt. This value is calculated based on a
491** maximum database size of 2^31 pages a minimum fanout of 2 for a
492** root-node and 3 for all other internal nodes.
493**
494** If a tree that appears to be taller than this is encountered, it is
495** assumed that the database is corrupt.
496*/
497#define BTCURSOR_MAX_DEPTH 20
498
499/*
500** A cursor is a pointer to a particular entry within a particular
501** b-tree within a database file.
502**
503** The entry is identified by its MemPage and the index in
504** MemPage.aCell[] of the entry.
505**
506** A single database file can be shared by two more database connections,
507** but cursors cannot be shared. Each cursor is associated with a
508** particular database connection identified BtCursor.pBtree.db.
509**
510** Fields in this structure are accessed under the BtShared.mutex
511** found at self->pBt->mutex.
512**
513** skipNext meaning:
514** The meaning of skipNext depends on the value of eState:
515**
516** eState Meaning of skipNext
517** VALID skipNext is meaningless and is ignored
518** INVALID skipNext is meaningless and is ignored
519** SKIPNEXT sqlite3BtreeNext() is a no-op if skipNext>0 and
520** sqlite3BtreePrevious() is no-op if skipNext<0.
521** REQUIRESEEK restoreCursorPosition() restores the cursor to
522** eState=SKIPNEXT if skipNext!=0
523** FAULT skipNext holds the cursor fault error code.
524*/
525struct BtCursor {
526 u8 eState; /* One of the CURSOR_XXX constants (see below) */
527 u8 curFlags; /* zero or more BTCF_* flags defined below */
528 u8 curPagerFlags; /* Flags to send to sqlite3PagerGet() */
529 u8 hints; /* As configured by CursorSetHints() */
530 int skipNext; /* Prev() is noop if negative. Next() is noop if positive.
531 ** Error code if eState==CURSOR_FAULT */
532 Btree *pBtree; /* The Btree to which this cursor belongs */
533 Pgno *aOverflow; /* Cache of overflow page locations */
534 void *pKey; /* Saved key that was cursor last known position */
535 /* All fields above are zeroed when the cursor is allocated. See
536 ** sqlite3BtreeCursorZero(). Fields that follow must be manually
537 ** initialized. */
538#define BTCURSOR_FIRST_UNINIT pBt /* Name of first uninitialized field */
539 BtShared *pBt; /* The BtShared this cursor points to */
540 BtCursor *pNext; /* Forms a linked list of all cursors */
541 CellInfo info; /* A parse of the cell we are pointing at */
542 i64 nKey; /* Size of pKey, or last integer key */
543 Pgno pgnoRoot; /* The root page of this tree */
544 i8 iPage; /* Index of current page in apPage */
545 u8 curIntKey; /* Value of apPage[0]->intKey */
546 u16 ix; /* Current index for apPage[iPage] */
547 u16 aiIdx[BTCURSOR_MAX_DEPTH-1]; /* Current index in apPage[i] */
548 struct KeyInfo *pKeyInfo; /* Arg passed to comparison function */
549 MemPage *pPage; /* Current page */
550 MemPage *apPage[BTCURSOR_MAX_DEPTH-1]; /* Stack of parents of current page */
551};
552
553/*
554** Legal values for BtCursor.curFlags
555*/
556#define BTCF_WriteFlag 0x01 /* True if a write cursor */
557#define BTCF_ValidNKey 0x02 /* True if info.nKey is valid */
558#define BTCF_ValidOvfl 0x04 /* True if aOverflow is valid */
559#define BTCF_AtLast 0x08 /* Cursor is pointing ot the last entry */
560#define BTCF_Incrblob 0x10 /* True if an incremental I/O handle */
561#define BTCF_Multiple 0x20 /* Maybe another cursor on the same btree */
562#define BTCF_Pinned 0x40 /* Cursor is busy and cannot be moved */
563
564/*
565** Potential values for BtCursor.eState.
566**
567** CURSOR_INVALID:
568** Cursor does not point to a valid entry. This can happen (for example)
569** because the table is empty or because BtreeCursorFirst() has not been
570** called.
571**
572** CURSOR_VALID:
573** Cursor points to a valid entry. getPayload() etc. may be called.
574**
575** CURSOR_SKIPNEXT:
576** Cursor is valid except that the Cursor.skipNext field is non-zero
577** indicating that the next sqlite3BtreeNext() or sqlite3BtreePrevious()
578** operation should be a no-op.
579**
580** CURSOR_REQUIRESEEK:
581** The table that this cursor was opened on still exists, but has been
582** modified since the cursor was last used. The cursor position is saved
583** in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in
584** this state, restoreCursorPosition() can be called to attempt to
585** seek the cursor to the saved position.
586**
587** CURSOR_FAULT:
588** An unrecoverable error (an I/O error or a malloc failure) has occurred
589** on a different connection that shares the BtShared cache with this
590** cursor. The error has left the cache in an inconsistent state.
591** Do nothing else with this cursor. Any attempt to use the cursor
592** should return the error code stored in BtCursor.skipNext
593*/
594#define CURSOR_VALID 0
595#define CURSOR_INVALID 1
596#define CURSOR_SKIPNEXT 2
597#define CURSOR_REQUIRESEEK 3
598#define CURSOR_FAULT 4
599
600/*
601** The database page the PENDING_BYTE occupies. This page is never used.
602*/
603#define PENDING_BYTE_PAGE(pBt) ((Pgno)((PENDING_BYTE/((pBt)->pageSize))+1))
604
605/*
606** These macros define the location of the pointer-map entry for a
607** database page. The first argument to each is the number of usable
608** bytes on each page of the database (often 1024). The second is the
609** page number to look up in the pointer map.
610**
611** PTRMAP_PAGENO returns the database page number of the pointer-map
612** page that stores the required pointer. PTRMAP_PTROFFSET returns
613** the offset of the requested map entry.
614**
615** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page,
616** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be
617** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements
618** this test.
619*/
620#define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno)
621#define PTRMAP_PTROFFSET(pgptrmap, pgno) (5*(pgno-pgptrmap-1))
622#define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno))
623
624/*
625** The pointer map is a lookup table that identifies the parent page for
626** each child page in the database file. The parent page is the page that
627** contains a pointer to the child. Every page in the database contains
628** 0 or 1 parent pages. (In this context 'database page' refers
629** to any page that is not part of the pointer map itself.) Each pointer map
630** entry consists of a single byte 'type' and a 4 byte parent page number.
631** The PTRMAP_XXX identifiers below are the valid types.
632**
633** The purpose of the pointer map is to facility moving pages from one
634** position in the file to another as part of autovacuum. When a page
635** is moved, the pointer in its parent must be updated to point to the
636** new location. The pointer map is used to locate the parent page quickly.
637**
638** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not
639** used in this case.
640**
641** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number
642** is not used in this case.
643**
644** PTRMAP_OVERFLOW1: The database page is the first page in a list of
645** overflow pages. The page number identifies the page that
646** contains the cell with a pointer to this overflow page.
647**
648** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of
649** overflow pages. The page-number identifies the previous
650** page in the overflow page list.
651**
652** PTRMAP_BTREE: The database page is a non-root btree page. The page number
653** identifies the parent page in the btree.
654*/
655#define PTRMAP_ROOTPAGE 1
656#define PTRMAP_FREEPAGE 2
657#define PTRMAP_OVERFLOW1 3
658#define PTRMAP_OVERFLOW2 4
659#define PTRMAP_BTREE 5
660
661/* A bunch of assert() statements to check the transaction state variables
662** of handle p (type Btree*) are internally consistent.
663*/
664#define btreeIntegrity(p) \
665 assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \
666 assert( p->pBt->inTransaction>=p->inTrans );
667
668
669/*
670** The ISAUTOVACUUM macro is used within balance_nonroot() to determine
671** if the database supports auto-vacuum or not. Because it is used
672** within an expression that is an argument to another macro
673** (sqliteMallocRaw), it is not possible to use conditional compilation.
674** So, this macro is defined instead.
675*/
676#ifndef SQLITE_OMIT_AUTOVACUUM
677#define ISAUTOVACUUM (pBt->autoVacuum)
678#else
679#define ISAUTOVACUUM 0
680#endif
681
682
683/*
684** This structure is passed around through all the sanity checking routines
685** in order to keep track of some global state information.
686**
687** The aRef[] array is allocated so that there is 1 bit for each page in
688** the database. As the integrity-check proceeds, for each page used in
689** the database the corresponding bit is set. This allows integrity-check to
690** detect pages that are used twice and orphaned pages (both of which
691** indicate corruption).
692*/
693typedef struct IntegrityCk IntegrityCk;
694struct IntegrityCk {
695 BtShared *pBt; /* The tree being checked out */
696 Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */
697 u8 *aPgRef; /* 1 bit per page in the db (see above) */
698 Pgno nPage; /* Number of pages in the database */
699 int mxErr; /* Stop accumulating errors when this reaches zero */
700 int nErr; /* Number of messages written to zErrMsg so far */
701 int bOomFault; /* A memory allocation error has occurred */
702 const char *zPfx; /* Error message prefix */
703 Pgno v1; /* Value for first %u substitution in zPfx */
704 int v2; /* Value for second %d substitution in zPfx */
705 StrAccum errMsg; /* Accumulate the error message text here */
706 u32 *heap; /* Min-heap used for analyzing cell coverage */
707 sqlite3 *db; /* Database connection running the check */
708};
709
710/*
711** Routines to read or write a two- and four-byte big-endian integer values.
712*/
713#define get2byte(x) ((x)[0]<<8 | (x)[1])
714#define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v))
715#define get4byte sqlite3Get4byte
716#define put4byte sqlite3Put4byte
717
718/*
719** get2byteAligned(), unlike get2byte(), requires that its argument point to a
720** two-byte aligned address. get2bytea() is only used for accessing the
721** cell addresses in a btree header.
722*/
723#if SQLITE_BYTEORDER==4321
724# define get2byteAligned(x) (*(u16*)(x))
725#elif SQLITE_BYTEORDER==1234 && GCC_VERSION>=4008000
726# define get2byteAligned(x) __builtin_bswap16(*(u16*)(x))
727#elif SQLITE_BYTEORDER==1234 && MSVC_VERSION>=1300
728# define get2byteAligned(x) _byteswap_ushort(*(u16*)(x))
729#else
730# define get2byteAligned(x) ((x)[0]<<8 | (x)[1])
731#endif
732