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diff --git a/src/btreeInt.h b/src/btreeInt.h new file mode 100644 index 0000000..1f45553 --- /dev/null +++ b/src/btreeInt.h @@ -0,0 +1,731 @@ +/* +** 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 an 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 65536. +** 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. (1 means 65536) +** 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 (must be 64) +** 22 1 Min embedded payload fraction (must be 32) +** 23 1 Min leaf payload fraction (must be 32) +** 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 Application-ID +** 72 20 unused +** 92 4 The version-valid-for number +** 96 4 SQLITE_VERSION_NUMBER +** +** 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 an 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) ((int)(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; +typedef struct CellInfo CellInfo; + +/* +** 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 + +/* +** An instance of this object stores information about each a single database +** page that has been loaded into memory. The information in this object +** is derived from the raw on-disk page content. +** +** As each database page is loaded into memory, the pager allocats an +** instance of this object and zeros the first 8 bytes. (This is the +** "extra" information associated with each page of the pager.) +** +** 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 intKey; /* True if table b-trees. False for index b-trees */ + u8 intKeyLeaf; /* True if the leaf of an intKey table */ + Pgno pgno; /* Page number for this page */ + /* Only the first 8 bytes (above) are zeroed by pager.c when a new page + ** is allocated. All fields that follow must be initialized before use */ + u8 leaf; /* True if a leaf page */ + u8 hdrOffset; /* 100 for page 1. 0 otherwise */ + u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */ + u8 max1bytePayload; /* min(maxLocal,127) */ + u8 nOverflow; /* Number of overflow cell bodies in aCell[] */ + 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 */ + int nFree; /* Number of free bytes on the page. -1 for unknown */ + u16 nCell; /* Number of cells on this page, local and ovfl */ + u16 maskPage; /* Mask for page offset */ + u16 aiOvfl[4]; /* Insert the i-th overflow cell before the aiOvfl-th + ** non-overflow cell */ + u8 *apOvfl[4]; /* Pointers to the body of overflow cells */ + BtShared *pBt; /* Pointer to BtShared that this page is part of */ + u8 *aData; /* Pointer to disk image of the page data */ + u8 *aDataEnd; /* One byte past the end of the entire page - not just + ** the usable space, the entire page. Used to prevent + ** corruption-induced buffer overflow. */ + u8 *aCellIdx; /* The cell index area */ + u8 *aDataOfst; /* Same as aData for leaves. aData+4 for interior */ + DbPage *pDbPage; /* Pager page handle */ + u16 (*xCellSize)(MemPage*,u8*); /* cellSizePtr method */ + void (*xParseCell)(MemPage*,u8*,CellInfo*); /* btreeParseCell method */ +}; + +/* +** 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 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 */ + u8 hasIncrblobCur; /* True if there are one or more Incrblob cursors */ + int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */ + int nBackup; /* Number of backup operations reading this btree */ + u32 iBDataVersion; /* Combines with pBt->pPager->iDataVersion */ + Btree *pNext; /* List of other sharable Btrees from the same db */ + Btree *pPrev; /* Back pointer of the same list */ +#ifdef SQLITE_DEBUG + u64 nSeek; /* Calls to sqlite3BtreeMovetoUnpacked() */ +#endif +#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. +** +** These values must match SQLITE_TXN_NONE, SQLITE_TXN_READ, and +** SQLITE_TXN_WRITE +*/ +#define TRANS_NONE 0 +#define TRANS_READ 1 +#define TRANS_WRITE 2 + +#if TRANS_NONE!=SQLITE_TXN_NONE +# error wrong numeric code for no-transaction +#endif +#if TRANS_READ!=SQLITE_TXN_READ +# error wrong numeric code for read-transaction +#endif +#if TRANS_WRITE!=SQLITE_TXN_WRITE +# error wrong numeric code for write-transaction +#endif + + +/* +** An instance of this object represents a single database file. +** +** A single database file can be in use at 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_MAIN 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 openFlags; /* Flags to sqlite3BtreeOpen() */ +#ifndef SQLITE_OMIT_AUTOVACUUM + u8 autoVacuum; /* True if auto-vacuum is enabled */ + u8 incrVacuum; /* True if incr-vacuum is enabled */ + u8 bDoTruncate; /* True to truncate db on commit */ +#endif + u8 inTransaction; /* Transaction state */ + u8 max1bytePayload; /* Maximum first byte of cell for a 1-byte payload */ + u8 nReserveWanted; /* Desired number of extra bytes per page */ + u16 btsFlags; /* Boolean parameters. See BTS_* macros below */ + 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 */ + u32 pageSize; /* Total number of bytes on a page */ + u32 usableSize; /* Number of usable bytes on each page */ + 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 object */ + 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 */ +#endif + u8 *pTmpSpace; /* Temp space sufficient to hold a single cell */ + int nPreformatSize; /* Size of last cell written by TransferRow() */ +}; + +/* +** Allowed values for BtShared.btsFlags +*/ +#define BTS_READ_ONLY 0x0001 /* Underlying file is readonly */ +#define BTS_PAGESIZE_FIXED 0x0002 /* Page size can no longer be changed */ +#define BTS_SECURE_DELETE 0x0004 /* PRAGMA secure_delete is enabled */ +#define BTS_OVERWRITE 0x0008 /* Overwrite deleted content with zeros */ +#define BTS_FAST_SECURE 0x000c /* Combination of the previous two */ +#define BTS_INITIALLY_EMPTY 0x0010 /* Database was empty at trans start */ +#define BTS_NO_WAL 0x0020 /* Do not open write-ahead-log files */ +#define BTS_EXCLUSIVE 0x0040 /* pWriter has an exclusive lock */ +#define BTS_PENDING 0x0080 /* Waiting for read-locks to clear */ + +/* +** 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. +*/ +struct CellInfo { + i64 nKey; /* The key for INTKEY tables, or nPayload otherwise */ + u8 *pPayload; /* Pointer to the start of payload */ + u32 nPayload; /* Bytes of payload */ + u16 nLocal; /* Amount of payload held locally, not on 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 be 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. +** +** skipNext meaning: +** The meaning of skipNext depends on the value of eState: +** +** eState Meaning of skipNext +** VALID skipNext is meaningless and is ignored +** INVALID skipNext is meaningless and is ignored +** SKIPNEXT sqlite3BtreeNext() is a no-op if skipNext>0 and +** sqlite3BtreePrevious() is no-op if skipNext<0. +** REQUIRESEEK restoreCursorPosition() restores the cursor to +** eState=SKIPNEXT if skipNext!=0 +** FAULT skipNext holds the cursor fault error code. +*/ +struct BtCursor { + u8 eState; /* One of the CURSOR_XXX constants (see below) */ + u8 curFlags; /* zero or more BTCF_* flags defined below */ + u8 curPagerFlags; /* Flags to send to sqlite3PagerGet() */ + u8 hints; /* As configured by CursorSetHints() */ + int skipNext; /* Prev() is noop if negative. Next() is noop if positive. + ** Error code if eState==CURSOR_FAULT */ + Btree *pBtree; /* The Btree to which this cursor belongs */ + Pgno *aOverflow; /* Cache of overflow page locations */ + void *pKey; /* Saved key that was cursor last known position */ + /* All fields above are zeroed when the cursor is allocated. See + ** sqlite3BtreeCursorZero(). Fields that follow must be manually + ** initialized. */ +#define BTCURSOR_FIRST_UNINIT pBt /* Name of first uninitialized field */ + BtShared *pBt; /* The BtShared this cursor points to */ + BtCursor *pNext; /* Forms a linked list of all cursors */ + CellInfo info; /* A parse of the cell we are pointing at */ + i64 nKey; /* Size of pKey, or last integer key */ + Pgno pgnoRoot; /* The root page of this tree */ + i8 iPage; /* Index of current page in apPage */ + u8 curIntKey; /* Value of apPage[0]->intKey */ + u16 ix; /* Current index for apPage[iPage] */ + u16 aiIdx[BTCURSOR_MAX_DEPTH-1]; /* Current index in apPage[i] */ + struct KeyInfo *pKeyInfo; /* Arg passed to comparison function */ + MemPage *pPage; /* Current page */ + MemPage *apPage[BTCURSOR_MAX_DEPTH-1]; /* Stack of parents of current page */ +}; + +/* +** Legal values for BtCursor.curFlags +*/ +#define BTCF_WriteFlag 0x01 /* True if a write cursor */ +#define BTCF_ValidNKey 0x02 /* True if info.nKey is valid */ +#define BTCF_ValidOvfl 0x04 /* True if aOverflow is valid */ +#define BTCF_AtLast 0x08 /* Cursor is pointing ot the last entry */ +#define BTCF_Incrblob 0x10 /* True if an incremental I/O handle */ +#define BTCF_Multiple 0x20 /* Maybe another cursor on the same btree */ +#define BTCF_Pinned 0x40 /* Cursor is busy and cannot be moved */ + +/* +** Potential values for BtCursor.eState. +** +** 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_VALID: +** Cursor points to a valid entry. getPayload() etc. may be called. +** +** CURSOR_SKIPNEXT: +** Cursor is valid except that the Cursor.skipNext field is non-zero +** indicating that the next sqlite3BtreeNext() or sqlite3BtreePrevious() +** operation should be a no-op. +** +** 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: +** An 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.skipNext +*/ +#define CURSOR_VALID 0 +#define CURSOR_INVALID 1 +#define CURSOR_SKIPNEXT 2 +#define CURSOR_REQUIRESEEK 3 +#define CURSOR_FAULT 4 + +/* +** The database page the PENDING_BYTE occupies. This page is never used. +*/ +#define PENDING_BYTE_PAGE(pBt) ((Pgno)((PENDING_BYTE/((pBt)->pageSize))+1)) + +/* +** 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. +** +** The aRef[] array is allocated so that there is 1 bit for each page in +** the database. As the integrity-check proceeds, for each page used in +** the database the corresponding bit is set. This allows integrity-check to +** detect pages that are used twice and orphaned pages (both of which +** indicate corruption). +*/ +typedef struct IntegrityCk IntegrityCk; +struct IntegrityCk { + BtShared *pBt; /* The tree being checked out */ + Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */ + u8 *aPgRef; /* 1 bit per page in the db (see above) */ + Pgno nPage; /* Number of pages in the database */ + int mxErr; /* Stop accumulating errors when this reaches zero */ + int nErr; /* Number of messages written to zErrMsg so far */ + int bOomFault; /* A memory allocation error has occurred */ + const char *zPfx; /* Error message prefix */ + Pgno v1; /* Value for first %u substitution in zPfx */ + int v2; /* Value for second %d substitution in zPfx */ + StrAccum errMsg; /* Accumulate the error message text here */ + u32 *heap; /* Min-heap used for analyzing cell coverage */ + sqlite3 *db; /* Database connection running the check */ +}; + +/* +** Routines to 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 + +/* +** get2byteAligned(), unlike get2byte(), requires that its argument point to a +** two-byte aligned address. get2bytea() is only used for accessing the +** cell addresses in a btree header. +*/ +#if SQLITE_BYTEORDER==4321 +# define get2byteAligned(x) (*(u16*)(x)) +#elif SQLITE_BYTEORDER==1234 && GCC_VERSION>=4008000 +# define get2byteAligned(x) __builtin_bswap16(*(u16*)(x)) +#elif SQLITE_BYTEORDER==1234 && MSVC_VERSION>=1300 +# define get2byteAligned(x) _byteswap_ushort(*(u16*)(x)) +#else +# define get2byteAligned(x) ((x)[0]<<8 | (x)[1]) +#endif |