/* ** 2004 April 6 ** ** The author disclaims copyright to this source code. In place of ** a legal notice, here is a blessing: ** ** May you do good and not evil. ** May you find forgiveness for yourself and forgive others. ** May you share freely, never taking more than you give. ** ************************************************************************* ** This file implements a external (disk-based) database using BTrees. ** For a detailed discussion of BTrees, refer to ** ** Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3: ** "Sorting And Searching", pages 473-480. Addison-Wesley ** Publishing Company, Reading, Massachusetts. ** ** The basic idea is that each page of the file contains N database ** entries and N+1 pointers to subpages. ** ** ---------------------------------------------------------------- ** | Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) | ** ---------------------------------------------------------------- ** ** All of the keys on the page that Ptr(0) points to have values less ** than Key(0). All of the keys on page Ptr(1) and its subpages have ** values greater than Key(0) and less than Key(1). All of the keys ** on Ptr(N) and its subpages have values greater than Key(N-1). And ** so forth. ** ** Finding a particular key requires reading O(log(M)) pages from the ** disk where M is the number of entries in the tree. ** ** In this implementation, a single file can hold one or more separate ** BTrees. Each BTree is identified by the index of its root page. The ** key and data for any entry are combined to form the "payload". A ** fixed amount of payload can be carried directly on the database ** page. If the payload is larger than the preset amount then surplus ** bytes are stored on overflow pages. The payload for an entry ** and the preceding pointer are combined to form a "Cell". Each ** page has a small header which contains the Ptr(N) pointer and other ** information such as the size of key and data. ** ** FORMAT DETAILS ** ** The file is divided into pages. The first page is called page 1, ** the second is page 2, and so forth. A page number of zero indicates ** "no such page". The page size can be any power of 2 between 512 and 32768. ** Each page can be either a btree page, a freelist page, an overflow ** page, or a pointer-map page. ** ** The first page is always a btree page. The first 100 bytes of the first ** page contain a special header (the "file header") that describes the file. ** The format of the file header is as follows: ** ** OFFSET SIZE DESCRIPTION ** 0 16 Header string: "SQLite format 3\000" ** 16 2 Page size in bytes. ** 18 1 File format write version ** 19 1 File format read version ** 20 1 Bytes of unused space at the end of each page ** 21 1 Max embedded payload fraction ** 22 1 Min embedded payload fraction ** 23 1 Min leaf payload fraction ** 24 4 File change counter ** 28 4 Reserved for future use ** 32 4 First freelist page ** 36 4 Number of freelist pages in the file ** 40 60 15 4-byte meta values passed to higher layers ** ** 40 4 Schema cookie ** 44 4 File format of schema layer ** 48 4 Size of page cache ** 52 4 Largest root-page (auto/incr_vacuum) ** 56 4 1=UTF-8 2=UTF16le 3=UTF16be ** 60 4 User version ** 64 4 Incremental vacuum mode ** 68 4 unused ** 72 4 unused ** 76 4 unused ** ** All of the integer values are big-endian (most significant byte first). ** ** The file change counter is incremented when the database is changed ** This counter allows other processes to know when the file has changed ** and thus when they need to flush their cache. ** ** The max embedded payload fraction is the amount of the total usable ** space in a page that can be consumed by a single cell for standard ** B-tree (non-LEAFDATA) tables. A value of 255 means 100%. The default ** is to limit the maximum cell size so that at least 4 cells will fit ** on one page. Thus the default max embedded payload fraction is 64. ** ** If the payload for a cell is larger than the max payload, then extra ** payload is spilled to overflow pages. Once an overflow page is allocated, ** as many bytes as possible are moved into the overflow pages without letting ** the cell size drop below the min embedded payload fraction. ** ** The min leaf payload fraction is like the min embedded payload fraction ** except that it applies to leaf nodes in a LEAFDATA tree. The maximum ** payload fraction for a LEAFDATA tree is always 100% (or 255) and it ** not specified in the header. ** ** Each btree pages is divided into three sections: The header, the ** cell pointer array, and the cell content area. Page 1 also has a 100-byte ** file header that occurs before the page header. ** ** |----------------| ** | file header | 100 bytes. Page 1 only. ** |----------------| ** | page header | 8 bytes for leaves. 12 bytes for interior nodes ** |----------------| ** | cell pointer | | 2 bytes per cell. Sorted order. ** | array | | Grows downward ** | | v ** |----------------| ** | unallocated | ** | space | ** |----------------| ^ Grows upwards ** | cell content | | Arbitrary order interspersed with freeblocks. ** | area | | and free space fragments. ** |----------------| ** ** The page headers looks like this: ** ** OFFSET SIZE DESCRIPTION ** 0 1 Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf ** 1 2 byte offset to the first freeblock ** 3 2 number of cells on this page ** 5 2 first byte of the cell content area ** 7 1 number of fragmented free bytes ** 8 4 Right child (the Ptr(N) value). Omitted on leaves. ** ** The flags define the format of this btree page. The leaf flag means that ** this page has no children. The zerodata flag means that this page carries ** only keys and no data. The intkey flag means that the key is a integer ** which is stored in the key size entry of the cell header rather than in ** the payload area. ** ** The cell pointer array begins on the first byte after the page header. ** The cell pointer array contains zero or more 2-byte numbers which are ** offsets from the beginning of the page to the cell content in the cell ** content area. The cell pointers occur in sorted order. The system strives ** to keep free space after the last cell pointer so that new cells can ** be easily added without having to defragment the page. ** ** Cell content is stored at the very end of the page and grows toward the ** beginning of the page. ** ** Unused space within the cell content area is collected into a linked list of ** freeblocks. Each freeblock is at least 4 bytes in size. The byte offset ** to the first freeblock is given in the header. Freeblocks occur in ** increasing order. Because a freeblock must be at least 4 bytes in size, ** any group of 3 or fewer unused bytes in the cell content area cannot ** exist on the freeblock chain. A group of 3 or fewer free bytes is called ** a fragment. The total number of bytes in all fragments is recorded. ** in the page header at offset 7. ** ** SIZE DESCRIPTION ** 2 Byte offset of the next freeblock ** 2 Bytes in this freeblock ** ** Cells are of variable length. Cells are stored in the cell content area at ** the end of the page. Pointers to the cells are in the cell pointer array ** that immediately follows the page header. Cells is not necessarily ** contiguous or in order, but cell pointers are contiguous and in order. ** ** Cell content makes use of variable length integers. A variable ** length integer is 1 to 9 bytes where the lower 7 bits of each ** byte are used. The integer consists of all bytes that have bit 8 set and ** the first byte with bit 8 clear. The most significant byte of the integer ** appears first. A variable-length integer may not be more than 9 bytes long. ** As a special case, all 8 bytes of the 9th byte are used as data. This ** allows a 64-bit integer to be encoded in 9 bytes. ** ** 0x00 becomes 0x00000000 ** 0x7f becomes 0x0000007f ** 0x81 0x00 becomes 0x00000080 ** 0x82 0x00 becomes 0x00000100 ** 0x80 0x7f becomes 0x0000007f ** 0x8a 0x91 0xd1 0xac 0x78 becomes 0x12345678 ** 0x81 0x81 0x81 0x81 0x01 becomes 0x10204081 ** ** Variable length integers are used for rowids and to hold the number of ** bytes of key and data in a btree cell. ** ** The content of a cell looks like this: ** ** SIZE DESCRIPTION ** 4 Page number of the left child. Omitted if leaf flag is set. ** var Number of bytes of data. Omitted if the zerodata flag is set. ** var Number of bytes of key. Or the key itself if intkey flag is set. ** * Payload ** 4 First page of the overflow chain. Omitted if no overflow ** ** Overflow pages form a linked list. Each page except the last is completely ** filled with data (pagesize - 4 bytes). The last page can have as little ** as 1 byte of data. ** ** SIZE DESCRIPTION ** 4 Page number of next overflow page ** * Data ** ** Freelist pages come in two subtypes: trunk pages and leaf pages. The ** file header points to the first in a linked list of trunk page. Each trunk ** page points to multiple leaf pages. The content of a leaf page is ** unspecified. A trunk page looks like this: ** ** SIZE DESCRIPTION ** 4 Page number of next trunk page ** 4 Number of leaf pointers on this page ** * zero or more pages numbers of leaves */ #include "sqliteInt.h" /* The following value is the maximum cell size assuming a maximum page ** size give above. */ #define MX_CELL_SIZE(pBt) (pBt->pageSize-8) /* The maximum number of cells on a single page of the database. This ** assumes a minimum cell size of 6 bytes (4 bytes for the cell itself ** plus 2 bytes for the index to the cell in the page header). Such ** small cells will be rare, but they are possible. */ #define MX_CELL(pBt) ((pBt->pageSize-8)/6) /* Forward declarations */ typedef struct MemPage MemPage; typedef struct BtLock BtLock; /* ** This is a magic string that appears at the beginning of every ** SQLite database in order to identify the file as a real database. ** ** You can change this value at compile-time by specifying a ** -DSQLITE_FILE_HEADER="..." on the compiler command-line. The ** header must be exactly 16 bytes including the zero-terminator so ** the string itself should be 15 characters long. If you change ** the header, then your custom library will not be able to read ** databases generated by the standard tools and the standard tools ** will not be able to read databases created by your custom library. */ #ifndef SQLITE_FILE_HEADER /* 123456789 123456 */ # define SQLITE_FILE_HEADER "SQLite format 3" #endif /* ** Page type flags. An ORed combination of these flags appear as the ** first byte of on-disk image of every BTree page. */ #define PTF_INTKEY 0x01 #define PTF_ZERODATA 0x02 #define PTF_LEAFDATA 0x04 #define PTF_LEAF 0x08 /* ** As each page of the file is loaded into memory, an instance of the following ** structure is appended and initialized to zero. This structure stores ** information about the page that is decoded from the raw file page. ** ** The pParent field points back to the parent page. This allows us to ** walk up the BTree from any leaf to the root. Care must be taken to ** unref() the parent page pointer when this page is no longer referenced. ** The pageDestructor() routine handles that chore. ** ** Access to all fields of this structure is controlled by the mutex ** stored in MemPage.pBt->mutex. */ struct MemPage { u8 isInit; /* True if previously initialized. MUST BE FIRST! */ u8 nOverflow; /* Number of overflow cell bodies in aCell[] */ u8 intKey; /* True if intkey flag is set */ u8 leaf; /* True if leaf flag is set */ u8 hasData; /* True if this page stores data */ u8 hdrOffset; /* 100 for page 1. 0 otherwise */ u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */ u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */ u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */ u16 cellOffset; /* Index in aData of first cell pointer */ u16 nFree; /* Number of free bytes on the page */ u16 nCell; /* Number of cells on this page, local and ovfl */ u16 maskPage; /* Mask for page offset */ struct _OvflCell { /* Cells that will not fit on aData[] */ u8 *pCell; /* Pointers to the body of the overflow cell */ u16 idx; /* Insert this cell before idx-th non-overflow cell */ } aOvfl[5]; BtShared *pBt; /* Pointer to BtShared that this page is part of */ u8 *aData; /* Pointer to disk image of the page data */ DbPage *pDbPage; /* Pager page handle */ Pgno pgno; /* Page number for this page */ }; /* ** The in-memory image of a disk page has the auxiliary information appended ** to the end. EXTRA_SIZE is the number of bytes of space needed to hold ** that extra information. */ #define EXTRA_SIZE sizeof(MemPage) /* ** A linked list of the following structures is stored at BtShared.pLock. ** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor ** is opened on the table with root page BtShared.iTable. Locks are removed ** from this list when a transaction is committed or rolled back, or when ** a btree handle is closed. */ struct BtLock { Btree *pBtree; /* Btree handle holding this lock */ Pgno iTable; /* Root page of table */ u8 eLock; /* READ_LOCK or WRITE_LOCK */ BtLock *pNext; /* Next in BtShared.pLock list */ }; /* Candidate values for BtLock.eLock */ #define READ_LOCK 1 #define WRITE_LOCK 2 /* A Btree handle ** ** A database connection contains a pointer to an instance of ** this object for every database file that it has open. This structure ** is opaque to the database connection. The database connection cannot ** see the internals of this structure and only deals with pointers to ** this structure. ** ** For some database files, the same underlying database cache might be ** shared between multiple connections. In that case, each connection ** has it own instance of this object. But each instance of this object ** points to the same BtShared object. The database cache and the ** schema associated with the database file are all contained within ** the BtShared object. ** ** All fields in this structure are accessed under sqlite3.mutex. ** The pBt pointer itself may not be changed while there exists cursors ** in the referenced BtShared that point back to this Btree since those ** cursors have to do go through this Btree to find their BtShared and ** they often do so without holding sqlite3.mutex. */ struct Btree { sqlite3 *db; /* The database connection holding this btree */ BtShared *pBt; /* Sharable content of this btree */ u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */ u8 sharable; /* True if we can share pBt with another db */ u8 locked; /* True if db currently has pBt locked */ int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */ int nBackup; /* Number of backup operations reading this btree */ Btree *pNext; /* List of other sharable Btrees from the same db */ Btree *pPrev; /* Back pointer of the same list */ #ifndef SQLITE_OMIT_SHARED_CACHE BtLock lock; /* Object used to lock page 1 */ #endif }; /* ** Btree.inTrans may take one of the following values. ** ** If the shared-data extension is enabled, there may be multiple users ** of the Btree structure. At most one of these may open a write transaction, ** but any number may have active read transactions. */ #define TRANS_NONE 0 #define TRANS_READ 1 #define TRANS_WRITE 2 /* ** An instance of this object represents a single database file. ** ** A single database file can be in use as the same time by two ** or more database connections. When two or more connections are ** sharing the same database file, each connection has it own ** private Btree object for the file and each of those Btrees points ** to this one BtShared object. BtShared.nRef is the number of ** connections currently sharing this database file. ** ** Fields in this structure are accessed under the BtShared.mutex ** mutex, except for nRef and pNext which are accessed under the ** global SQLITE_MUTEX_STATIC_MASTER mutex. The pPager field ** may not be modified once it is initially set as long as nRef>0. ** The pSchema field may be set once under BtShared.mutex and ** thereafter is unchanged as long as nRef>0. ** ** isPending: ** ** If a BtShared client fails to obtain a write-lock on a database ** table (because there exists one or more read-locks on the table), ** the shared-cache enters 'pending-lock' state and isPending is ** set to true. ** ** The shared-cache leaves the 'pending lock' state when either of ** the following occur: ** ** 1) The current writer (BtShared.pWriter) concludes its transaction, OR ** 2) The number of locks held by other connections drops to zero. ** ** while in the 'pending-lock' state, no connection may start a new ** transaction. ** ** This feature is included to help prevent writer-starvation. */ struct BtShared { Pager *pPager; /* The page cache */ sqlite3 *db; /* Database connection currently using this Btree */ BtCursor *pCursor; /* A list of all open cursors */ MemPage *pPage1; /* First page of the database */ u8 readOnly; /* True if the underlying file is readonly */ u8 pageSizeFixed; /* True if the page size can no longer be changed */ u8 secureDelete; /* True if secure_delete is enabled */ u8 initiallyEmpty; /* Database is empty at start of transaction */ #ifndef SQLITE_OMIT_AUTOVACUUM u8 autoVacuum; /* True if auto-vacuum is enabled */ u8 incrVacuum; /* True if incr-vacuum is enabled */ #endif u16 pageSize; /* Total number of bytes on a page */ u16 usableSize; /* Number of usable bytes on each page */ u16 maxLocal; /* Maximum local payload in non-LEAFDATA tables */ u16 minLocal; /* Minimum local payload in non-LEAFDATA tables */ u16 maxLeaf; /* Maximum local payload in a LEAFDATA table */ u16 minLeaf; /* Minimum local payload in a LEAFDATA table */ u8 inTransaction; /* Transaction state */ u8 doNotUseWAL; /* If true, do not open write-ahead-log file */ int nTransaction; /* Number of open transactions (read + write) */ u32 nPage; /* Number of pages in the database */ void *pSchema; /* Pointer to space allocated by sqlite3BtreeSchema() */ void (*xFreeSchema)(void*); /* Destructor for BtShared.pSchema */ sqlite3_mutex *mutex; /* Non-recursive mutex required to access this struct */ Bitvec *pHasContent; /* Set of pages moved to free-list this transaction */ #ifndef SQLITE_OMIT_SHARED_CACHE int nRef; /* Number of references to this structure */ BtShared *pNext; /* Next on a list of sharable BtShared structs */ BtLock *pLock; /* List of locks held on this shared-btree struct */ Btree *pWriter; /* Btree with currently open write transaction */ u8 isExclusive; /* True if pWriter has an EXCLUSIVE lock on the db */ u8 isPending; /* If waiting for read-locks to clear */ #endif u8 *pTmpSpace; /* BtShared.pageSize bytes of space for tmp use */ }; /* ** An instance of the following structure is used to hold information ** about a cell. The parseCellPtr() function fills in this structure ** based on information extract from the raw disk page. */ typedef struct CellInfo CellInfo; struct CellInfo { u8 *pCell; /* Pointer to the start of cell content */ i64 nKey; /* The key for INTKEY tables, or number of bytes in key */ u32 nData; /* Number of bytes of data */ u32 nPayload; /* Total amount of payload */ u16 nHeader; /* Size of the cell content header in bytes */ u16 nLocal; /* Amount of payload held locally */ u16 iOverflow; /* Offset to overflow page number. Zero if no overflow */ u16 nSize; /* Size of the cell content on the main b-tree page */ }; /* ** Maximum depth of an SQLite B-Tree structure. Any B-Tree deeper than ** this will be declared corrupt. This value is calculated based on a ** maximum database size of 2^31 pages a minimum fanout of 2 for a ** root-node and 3 for all other internal nodes. ** ** If a tree that appears to be taller than this is encountered, it is ** assumed that the database is corrupt. */ #define BTCURSOR_MAX_DEPTH 20 /* ** A cursor is a pointer to a particular entry within a particular ** b-tree within a database file. ** ** The entry is identified by its MemPage and the index in ** MemPage.aCell[] of the entry. ** ** A single database file can shared by two more database connections, ** but cursors cannot be shared. Each cursor is associated with a ** particular database connection identified BtCursor.pBtree.db. ** ** Fields in this structure are accessed under the BtShared.mutex ** found at self->pBt->mutex. */ struct BtCursor { Btree *pBtree; /* The Btree to which this cursor belongs */ BtShared *pBt; /* The BtShared this cursor points to */ BtCursor *pNext, *pPrev; /* Forms a linked list of all cursors */ struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */ Pgno pgnoRoot; /* The root page of this tree */ sqlite3_int64 cachedRowid; /* Next rowid cache. 0 means not valid */ CellInfo info; /* A parse of the cell we are pointing at */ u8 wrFlag; /* True if writable */ u8 atLast; /* Cursor pointing to the last entry */ u8 validNKey; /* True if info.nKey is valid */ u8 eState; /* One of the CURSOR_XXX constants (see below) */ void *pKey; /* Saved key that was cursor's last known position */ i64 nKey; /* Size of pKey, or last integer key */ int skipNext; /* Prev() is noop if negative. Next() is noop if positive */ #ifndef SQLITE_OMIT_INCRBLOB u8 isIncrblobHandle; /* True if this cursor is an incr. io handle */ Pgno *aOverflow; /* Cache of overflow page locations */ #endif i16 iPage; /* Index of current page in apPage */ MemPage *apPage[BTCURSOR_MAX_DEPTH]; /* Pages from root to current page */ u16 aiIdx[BTCURSOR_MAX_DEPTH]; /* Current index in apPage[i] */ }; /* ** Potential values for BtCursor.eState. ** ** CURSOR_VALID: ** Cursor points to a valid entry. getPayload() etc. may be called. ** ** CURSOR_INVALID: ** Cursor does not point to a valid entry. This can happen (for example) ** because the table is empty or because BtreeCursorFirst() has not been ** called. ** ** CURSOR_REQUIRESEEK: ** The table that this cursor was opened on still exists, but has been ** modified since the cursor was last used. The cursor position is saved ** in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in ** this state, restoreCursorPosition() can be called to attempt to ** seek the cursor to the saved position. ** ** CURSOR_FAULT: ** A unrecoverable error (an I/O error or a malloc failure) has occurred ** on a different connection that shares the BtShared cache with this ** cursor. The error has left the cache in an inconsistent state. ** Do nothing else with this cursor. Any attempt to use the cursor ** should return the error code stored in BtCursor.skip */ #define CURSOR_INVALID 0 #define CURSOR_VALID 1 #define CURSOR_REQUIRESEEK 2 #define CURSOR_FAULT 3 /* ** The database page the PENDING_BYTE occupies. This page is never used. */ # define PENDING_BYTE_PAGE(pBt) PAGER_MJ_PGNO(pBt) /* ** These macros define the location of the pointer-map entry for a ** database page. The first argument to each is the number of usable ** bytes on each page of the database (often 1024). The second is the ** page number to look up in the pointer map. ** ** PTRMAP_PAGENO returns the database page number of the pointer-map ** page that stores the required pointer. PTRMAP_PTROFFSET returns ** the offset of the requested map entry. ** ** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page, ** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be ** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements ** this test. */ #define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno) #define PTRMAP_PTROFFSET(pgptrmap, pgno) (5*(pgno-pgptrmap-1)) #define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno)) /* ** The pointer map is a lookup table that identifies the parent page for ** each child page in the database file. The parent page is the page that ** contains a pointer to the child. Every page in the database contains ** 0 or 1 parent pages. (In this context 'database page' refers ** to any page that is not part of the pointer map itself.) Each pointer map ** entry consists of a single byte 'type' and a 4 byte parent page number. ** The PTRMAP_XXX identifiers below are the valid types. ** ** The purpose of the pointer map is to facility moving pages from one ** position in the file to another as part of autovacuum. When a page ** is moved, the pointer in its parent must be updated to point to the ** new location. The pointer map is used to locate the parent page quickly. ** ** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not ** used in this case. ** ** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number ** is not used in this case. ** ** PTRMAP_OVERFLOW1: The database page is the first page in a list of ** overflow pages. The page number identifies the page that ** contains the cell with a pointer to this overflow page. ** ** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of ** overflow pages. The page-number identifies the previous ** page in the overflow page list. ** ** PTRMAP_BTREE: The database page is a non-root btree page. The page number ** identifies the parent page in the btree. */ #define PTRMAP_ROOTPAGE 1 #define PTRMAP_FREEPAGE 2 #define PTRMAP_OVERFLOW1 3 #define PTRMAP_OVERFLOW2 4 #define PTRMAP_BTREE 5 /* A bunch of assert() statements to check the transaction state variables ** of handle p (type Btree*) are internally consistent. */ #define btreeIntegrity(p) \ assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \ assert( p->pBt->inTransaction>=p->inTrans ); /* ** The ISAUTOVACUUM macro is used within balance_nonroot() to determine ** if the database supports auto-vacuum or not. Because it is used ** within an expression that is an argument to another macro ** (sqliteMallocRaw), it is not possible to use conditional compilation. ** So, this macro is defined instead. */ #ifndef SQLITE_OMIT_AUTOVACUUM #define ISAUTOVACUUM (pBt->autoVacuum) #else #define ISAUTOVACUUM 0 #endif /* ** This structure is passed around through all the sanity checking routines ** in order to keep track of some global state information. */ typedef struct IntegrityCk IntegrityCk; struct IntegrityCk { BtShared *pBt; /* The tree being checked out */ Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */ Pgno nPage; /* Number of pages in the database */ int *anRef; /* Number of times each page is referenced */ int mxErr; /* Stop accumulating errors when this reaches zero */ int nErr; /* Number of messages written to zErrMsg so far */ int mallocFailed; /* A memory allocation error has occurred */ StrAccum errMsg; /* Accumulate the error message text here */ }; /* ** Read or write a two- and four-byte big-endian integer values. */ #define get2byte(x) ((x)[0]<<8 | (x)[1]) #define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v)) #define get4byte sqlite3Get4byte #define put4byte sqlite3Put4byte