wasCSharpSQLite – Blame information for rev 1

Subversion Repositories:
Rev:
Rev Author Line No. Line
1 office 1 using System;
2 using System.Diagnostics;
3  
4 using i16 = System.Int16;
5 using i64 = System.Int64;
6 using u8 = System.Byte;
7 using u16 = System.UInt16;
8 using u32 = System.UInt32;
9 using u64 = System.UInt64;
10  
11 using sqlite3_int64 = System.Int64;
12 using Pgno = System.UInt32;
13  
14 namespace Community.CsharpSqlite
15 {
16 using DbPage = Sqlite3.PgHdr;
17  
18 public partial class Sqlite3
19 {
20 /*
21 ** 2004 April 6
22 **
23 ** The author disclaims copyright to this source code. In place of
24 ** a legal notice, here is a blessing:
25 **
26 ** May you do good and not evil.
27 ** May you find forgiveness for yourself and forgive others.
28 ** May you share freely, never taking more than you give.
29 **
30 *************************************************************************
31 **
32 ** This file implements a external (disk-based) database using BTrees.
33 ** For a detailed discussion of BTrees, refer to
34 **
35 ** Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
36 ** "Sorting And Searching", pages 473-480. Addison-Wesley
37 ** Publishing Company, Reading, Massachusetts.
38 **
39 ** The basic idea is that each page of the file contains N database
40 ** entries and N+1 pointers to subpages.
41 **
42 ** ----------------------------------------------------------------
43 ** | Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) |
44 ** ----------------------------------------------------------------
45 **
46 ** All of the keys on the page that Ptr(0) points to have values less
47 ** than Key(0). All of the keys on page Ptr(1) and its subpages have
48 ** values greater than Key(0) and less than Key(1). All of the keys
49 ** on Ptr(N) and its subpages have values greater than Key(N-1). And
50 ** so forth.
51 **
52 ** Finding a particular key requires reading O(log(M)) pages from the
53 ** disk where M is the number of entries in the tree.
54 **
55 ** In this implementation, a single file can hold one or more separate
56 ** BTrees. Each BTree is identified by the index of its root page. The
57 ** key and data for any entry are combined to form the "payload". A
58 ** fixed amount of payload can be carried directly on the database
59 ** page. If the payload is larger than the preset amount then surplus
60 ** bytes are stored on overflow pages. The payload for an entry
61 ** and the preceding pointer are combined to form a "Cell". Each
62 ** page has a small header which contains the Ptr(N) pointer and other
63 ** information such as the size of key and data.
64 **
65 ** FORMAT DETAILS
66 **
67 ** The file is divided into pages. The first page is called page 1,
68 ** the second is page 2, and so forth. A page number of zero indicates
69 ** "no such page". The page size can be any power of 2 between 512 and 65536.
70 ** Each page can be either a btree page, a freelist page, an overflow
71 ** page, or a pointer-map page.
72 **
73 ** The first page is always a btree page. The first 100 bytes of the first
74 ** page contain a special header (the "file header") that describes the file.
75 ** The format of the file header is as follows:
76 **
77 ** OFFSET SIZE DESCRIPTION
78 ** 0 16 Header string: "SQLite format 3\000"
79 ** 16 2 Page size in bytes.
80 ** 18 1 File format write version
81 ** 19 1 File format read version
82 ** 20 1 Bytes of unused space at the end of each page
83 ** 21 1 Max embedded payload fraction
84 ** 22 1 Min embedded payload fraction
85 ** 23 1 Min leaf payload fraction
86 ** 24 4 File change counter
87 ** 28 4 Reserved for future use
88 ** 32 4 First freelist page
89 ** 36 4 Number of freelist pages in the file
90 ** 40 60 15 4-byte meta values passed to higher layers
91 **
92 ** 40 4 Schema cookie
93 ** 44 4 File format of schema layer
94 ** 48 4 Size of page cache
95 ** 52 4 Largest root-page (auto/incr_vacuum)
96 ** 56 4 1=UTF-8 2=UTF16le 3=UTF16be
97 ** 60 4 User version
98 ** 64 4 Incremental vacuum mode
99 ** 68 4 unused
100 ** 72 4 unused
101 ** 76 4 unused
102 **
103 ** All of the integer values are big-endian (most significant byte first).
104 **
105 ** The file change counter is incremented when the database is changed
106 ** This counter allows other processes to know when the file has changed
107 ** and thus when they need to flush their cache.
108 **
109 ** The max embedded payload fraction is the amount of the total usable
110 ** space in a page that can be consumed by a single cell for standard
111 ** B-tree (non-LEAFDATA) tables. A value of 255 means 100%. The default
112 ** is to limit the maximum cell size so that at least 4 cells will fit
113 ** on one page. Thus the default max embedded payload fraction is 64.
114 **
115 ** If the payload for a cell is larger than the max payload, then extra
116 ** payload is spilled to overflow pages. Once an overflow page is allocated,
117 ** as many bytes as possible are moved into the overflow pages without letting
118 ** the cell size drop below the min embedded payload fraction.
119 **
120 ** The min leaf payload fraction is like the min embedded payload fraction
121 ** except that it applies to leaf nodes in a LEAFDATA tree. The maximum
122 ** payload fraction for a LEAFDATA tree is always 100% (or 255) and it
123 ** not specified in the header.
124 **
125 ** Each btree pages is divided into three sections: The header, the
126 ** cell pointer array, and the cell content area. Page 1 also has a 100-byte
127 ** file header that occurs before the page header.
128 **
129 ** |----------------|
130 ** | file header | 100 bytes. Page 1 only.
131 ** |----------------|
132 ** | page header | 8 bytes for leaves. 12 bytes for interior nodes
133 ** |----------------|
134 ** | cell pointer | | 2 bytes per cell. Sorted order.
135 ** | array | | Grows downward
136 ** | | v
137 ** |----------------|
138 ** | unallocated |
139 ** | space |
140 ** |----------------| ^ Grows upwards
141 ** | cell content | | Arbitrary order interspersed with freeblocks.
142 ** | area | | and free space fragments.
143 ** |----------------|
144 **
145 ** The page headers looks like this:
146 **
147 ** OFFSET SIZE DESCRIPTION
148 ** 0 1 Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf
149 ** 1 2 byte offset to the first freeblock
150 ** 3 2 number of cells on this page
151 ** 5 2 first byte of the cell content area
152 ** 7 1 number of fragmented free bytes
153 ** 8 4 Right child (the Ptr(N) value). Omitted on leaves.
154 **
155 ** The flags define the format of this btree page. The leaf flag means that
156 ** this page has no children. The zerodata flag means that this page carries
157 ** only keys and no data. The intkey flag means that the key is a integer
158 ** which is stored in the key size entry of the cell header rather than in
159 ** the payload area.
160 **
161 ** The cell pointer array begins on the first byte after the page header.
162 ** The cell pointer array contains zero or more 2-byte numbers which are
163 ** offsets from the beginning of the page to the cell content in the cell
164 ** content area. The cell pointers occur in sorted order. The system strives
165 ** to keep free space after the last cell pointer so that new cells can
166 ** be easily added without having to defragment the page.
167 **
168 ** Cell content is stored at the very end of the page and grows toward the
169 ** beginning of the page.
170 **
171 ** Unused space within the cell content area is collected into a linked list of
172 ** freeblocks. Each freeblock is at least 4 bytes in size. The byte offset
173 ** to the first freeblock is given in the header. Freeblocks occur in
174 ** increasing order. Because a freeblock must be at least 4 bytes in size,
175 ** any group of 3 or fewer unused bytes in the cell content area cannot
176 ** exist on the freeblock chain. A group of 3 or fewer free bytes is called
177 ** a fragment. The total number of bytes in all fragments is recorded.
178 ** in the page header at offset 7.
179 **
180 ** SIZE DESCRIPTION
181 ** 2 Byte offset of the next freeblock
182 ** 2 Bytes in this freeblock
183 **
184 ** Cells are of variable length. Cells are stored in the cell content area at
185 ** the end of the page. Pointers to the cells are in the cell pointer array
186 ** that immediately follows the page header. Cells is not necessarily
187 ** contiguous or in order, but cell pointers are contiguous and in order.
188 **
189 ** Cell content makes use of variable length integers. A variable
190 ** length integer is 1 to 9 bytes where the lower 7 bits of each
191 ** byte are used. The integer consists of all bytes that have bit 8 set and
192 ** the first byte with bit 8 clear. The most significant byte of the integer
193 ** appears first. A variable-length integer may not be more than 9 bytes long.
194 ** As a special case, all 8 bytes of the 9th byte are used as data. This
195 ** allows a 64-bit integer to be encoded in 9 bytes.
196 **
197 ** 0x00 becomes 0x00000000
198 ** 0x7f becomes 0x0000007f
199 ** 0x81 0x00 becomes 0x00000080
200 ** 0x82 0x00 becomes 0x00000100
201 ** 0x80 0x7f becomes 0x0000007f
202 ** 0x8a 0x91 0xd1 0xac 0x78 becomes 0x12345678
203 ** 0x81 0x81 0x81 0x81 0x01 becomes 0x10204081
204 **
205 ** Variable length integers are used for rowids and to hold the number of
206 ** bytes of key and data in a btree cell.
207 **
208 ** The content of a cell looks like this:
209 **
210 ** SIZE DESCRIPTION
211 ** 4 Page number of the left child. Omitted if leaf flag is set.
212 ** var Number of bytes of data. Omitted if the zerodata flag is set.
213 ** var Number of bytes of key. Or the key itself if intkey flag is set.
214 ** * Payload
215 ** 4 First page of the overflow chain. Omitted if no overflow
216 **
217 ** Overflow pages form a linked list. Each page except the last is completely
218 ** filled with data (pagesize - 4 bytes). The last page can have as little
219 ** as 1 byte of data.
220 **
221 ** SIZE DESCRIPTION
222 ** 4 Page number of next overflow page
223 ** * Data
224 **
225 ** Freelist pages come in two subtypes: trunk pages and leaf pages. The
226 ** file header points to the first in a linked list of trunk page. Each trunk
227 ** page points to multiple leaf pages. The content of a leaf page is
228 ** unspecified. A trunk page looks like this:
229 **
230 ** SIZE DESCRIPTION
231 ** 4 Page number of next trunk page
232 ** 4 Number of leaf pointers on this page
233 ** * zero or more pages numbers of leaves
234 *************************************************************************
235 ** Included in SQLite3 port to C#-SQLite; 2008 Noah B Hart
236 ** C#-SQLite is an independent reimplementation of the SQLite software library
237 **
238 ** SQLITE_SOURCE_ID: 2011-05-19 13:26:54 ed1da510a239ea767a01dc332b667119fa3c908e
239 **
240 *************************************************************************
241 */
242 //#include "sqliteInt.h"
243  
244 /* The following value is the maximum cell size assuming a maximum page
245 ** size give above.
246 */
247 //#define MX_CELL_SIZE(pBt) ((int)(pBt->pageSize-8))
248 static int MX_CELL_SIZE( BtShared pBt )
249 {
250 return (int)( pBt.pageSize - 8 );
251 }
252  
253 /* The maximum number of cells on a single page of the database. This
254 ** assumes a minimum cell size of 6 bytes (4 bytes for the cell itself
255 ** plus 2 bytes for the index to the cell in the page header). Such
256 ** small cells will be rare, but they are possible.
257 */
258 //#define MX_CELL(pBt) ((pBt.pageSize-8)/6)
259 static int MX_CELL( BtShared pBt )
260 {
261 return ( (int)( pBt.pageSize - 8 ) / 6 );
262 }
263  
264 /* Forward declarations */
265 //typedef struct MemPage MemPage;
266 //typedef struct BtLock BtLock;
267  
268 /*
269 ** This is a magic string that appears at the beginning of every
270 ** SQLite database in order to identify the file as a real database.
271 **
272 ** You can change this value at compile-time by specifying a
273 ** -DSQLITE_FILE_HEADER="..." on the compiler command-line. The
274 ** header must be exactly 16 bytes including the zero-terminator so
275 ** the string itself should be 15 characters long. If you change
276 ** the header, then your custom library will not be able to read
277 ** databases generated by the standard tools and the standard tools
278 ** will not be able to read databases created by your custom library.
279 */
280 #if !SQLITE_FILE_HEADER //* 123456789 123456 */
281 const string SQLITE_FILE_HEADER = "SQLite format 3\0";
282 #endif
283  
284 /*
285 ** Page type flags. An ORed combination of these flags appear as the
286 ** first byte of on-disk image of every BTree page.
287 */
288 const byte PTF_INTKEY = 0x01;
289 const byte PTF_ZERODATA = 0x02;
290 const byte PTF_LEAFDATA = 0x04;
291 const byte PTF_LEAF = 0x08;
292  
293 /*
294 ** As each page of the file is loaded into memory, an instance of the following
295 ** structure is appended and initialized to zero. This structure stores
296 ** information about the page that is decoded from the raw file page.
297 **
298 ** The pParent field points back to the parent page. This allows us to
299 ** walk up the BTree from any leaf to the root. Care must be taken to
300 ** unref() the parent page pointer when this page is no longer referenced.
301 ** The pageDestructor() routine handles that chore.
302 **
303 ** Access to all fields of this structure is controlled by the mutex
304 ** stored in MemPage.pBt.mutex.
305 */
306 public struct _OvflCell
307 { /* Cells that will not fit on aData[] */
308 public u8[] pCell; /* Pointers to the body of the overflow cell */
309 public u16 idx; /* Insert this cell before idx-th non-overflow cell */
310 public _OvflCell Copy()
311 {
312 _OvflCell cp = new _OvflCell();
313 if ( pCell != null )
314 {
315 cp.pCell = sqlite3Malloc( pCell.Length );
316 Buffer.BlockCopy( pCell, 0, cp.pCell, 0, pCell.Length );
317 }
318 cp.idx = idx;
319 return cp;
320 }
321 };
322 public class MemPage
323 {
324 public u8 isInit; /* True if previously initialized. MUST BE FIRST! */
325 public u8 nOverflow; /* Number of overflow cell bodies in aCell[] */
326 public u8 intKey; /* True if u8key flag is set */
327 public u8 leaf; /* 1 if leaf flag is set */
328 public u8 hasData; /* True if this page stores data */
329 public u8 hdrOffset; /* 100 for page 1. 0 otherwise */
330 public u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */
331 public u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */
332 public u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */
333 public u16 cellOffset; /* Index in aData of first cell pou16er */
334 public u16 nFree; /* Number of free bytes on the page */
335 public u16 nCell; /* Number of cells on this page, local and ovfl */
336 public u16 maskPage; /* Mask for page offset */
337 public _OvflCell[] aOvfl = new _OvflCell[5];
338 public BtShared pBt; /* Pointer to BtShared that this page is part of */
339 public byte[] aData; /* Pointer to disk image of the page data */
340 public DbPage pDbPage; /* Pager page handle */
341 public Pgno pgno; /* Page number for this page */
342  
343 //public byte[] aData
344 //{
345 // get
346 // {
347 // Debug.Assert( pgno != 1 || pDbPage.pData == _aData );
348 // return _aData;
349 // }
350 // set
351 // {
352 // _aData = value;
353 // Debug.Assert( pgno != 1 || pDbPage.pData == _aData );
354 // }
355 //}
356  
357 public MemPage Copy()
358 {
359 MemPage cp = (MemPage)MemberwiseClone();
360 if ( aOvfl != null )
361 {
362 cp.aOvfl = new _OvflCell[aOvfl.Length];
363 for ( int i = 0; i < aOvfl.Length; i++ )
364 cp.aOvfl[i] = aOvfl[i].Copy();
365 }
366 if ( aData != null )
367 {
368 cp.aData = sqlite3Malloc( aData.Length );
369 Buffer.BlockCopy( aData, 0, cp.aData, 0, aData.Length );
370 }
371 return cp;
372 }
373 };
374  
375 /*
376 ** The in-memory image of a disk page has the auxiliary information appended
377 ** to the end. EXTRA_SIZE is the number of bytes of space needed to hold
378 ** that extra information.
379 */
380 const int EXTRA_SIZE = 0;// No used in C#, since we use create a class; was MemPage.Length;
381  
382 /*
383 ** A linked list of the following structures is stored at BtShared.pLock.
384 ** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor
385 ** is opened on the table with root page BtShared.iTable. Locks are removed
386 ** from this list when a transaction is committed or rolled back, or when
387 ** a btree handle is closed.
388 */
389 public class BtLock
390 {
391 Btree pBtree; /* Btree handle holding this lock */
392 Pgno iTable; /* Root page of table */
393 u8 eLock; /* READ_LOCK or WRITE_LOCK */
394 BtLock pNext; /* Next in BtShared.pLock list */
395 };
396  
397 /* Candidate values for BtLock.eLock */
398 //#define READ_LOCK 1
399 //#define WRITE_LOCK 2
400 const int READ_LOCK = 1;
401 const int WRITE_LOCK = 2;
402  
403 /* A Btree handle
404 **
405 ** A database connection contains a pointer to an instance of
406 ** this object for every database file that it has open. This structure
407 ** is opaque to the database connection. The database connection cannot
408 ** see the internals of this structure and only deals with pointers to
409 ** this structure.
410 **
411 ** For some database files, the same underlying database cache might be
412 ** shared between multiple connections. In that case, each connection
413 ** has it own instance of this object. But each instance of this object
414 ** points to the same BtShared object. The database cache and the
415 ** schema associated with the database file are all contained within
416 ** the BtShared object.
417 **
418 ** All fields in this structure are accessed under sqlite3.mutex.
419 ** The pBt pointer itself may not be changed while there exists cursors
420 ** in the referenced BtShared that point back to this Btree since those
421 ** cursors have to go through this Btree to find their BtShared and
422 ** they often do so without holding sqlite3.mutex.
423 */
424 public class Btree
425 {
426 public sqlite3 db; /* The database connection holding this Btree */
427 public BtShared pBt; /* Sharable content of this Btree */
428 public u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
429 public bool sharable; /* True if we can share pBt with another db */
430 public bool locked; /* True if db currently has pBt locked */
431 public int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */
432 public int nBackup; /* Number of backup operations reading this btree */
433 public Btree pNext; /* List of other sharable Btrees from the same db */
434 public Btree pPrev; /* Back pointer of the same list */
435 #if !SQLITE_OMIT_SHARED_CACHE
436 BtLock lock; /* Object used to lock page 1 */
437 #endif
438 };
439  
440 /*
441 ** Btree.inTrans may take one of the following values.
442 **
443 ** If the shared-data extension is enabled, there may be multiple users
444 ** of the Btree structure. At most one of these may open a write transaction,
445 ** but any number may have active read transactions.
446 */
447 const byte TRANS_NONE = 0;
448 const byte TRANS_READ = 1;
449 const byte TRANS_WRITE = 2;
450  
451 /*
452 ** An instance of this object represents a single database file.
453 **
454 ** A single database file can be in use as the same time by two
455 ** or more database connections. When two or more connections are
456 ** sharing the same database file, each connection has it own
457 ** private Btree object for the file and each of those Btrees points
458 ** to this one BtShared object. BtShared.nRef is the number of
459 ** connections currently sharing this database file.
460 **
461 ** Fields in this structure are accessed under the BtShared.mutex
462 ** mutex, except for nRef and pNext which are accessed under the
463 ** global SQLITE_MUTEX_STATIC_MASTER mutex. The pPager field
464 ** may not be modified once it is initially set as long as nRef>0.
465 ** The pSchema field may be set once under BtShared.mutex and
466 ** thereafter is unchanged as long as nRef>0.
467 **
468 ** isPending:
469 **
470 ** If a BtShared client fails to obtain a write-lock on a database
471 ** table (because there exists one or more read-locks on the table),
472 ** the shared-cache enters 'pending-lock' state and isPending is
473 ** set to true.
474 **
475 ** The shared-cache leaves the 'pending lock' state when either of
476 ** the following occur:
477 **
478 ** 1) The current writer (BtShared.pWriter) concludes its transaction, OR
479 ** 2) The number of locks held by other connections drops to zero.
480 **
481 ** while in the 'pending-lock' state, no connection may start a new
482 ** transaction.
483 **
484 ** This feature is included to help prevent writer-starvation.
485 */
486 public class BtShared
487 {
488 public Pager pPager; /* The page cache */
489 public sqlite3 db; /* Database connection currently using this Btree */
490 public BtCursor pCursor; /* A list of all open cursors */
491 public MemPage pPage1; /* First page of the database */
492 public bool readOnly; /* True if the underlying file is readonly */
493 public bool pageSizeFixed; /* True if the page size can no longer be changed */
494 public bool secureDelete; /* True if secure_delete is enabled */
495 public bool initiallyEmpty; /* Database is empty at start of transaction */
496 public u8 openFlags; /* Flags to sqlite3BtreeOpen() */
497 #if !SQLITE_OMIT_AUTOVACUUM
498 public bool autoVacuum; /* True if auto-vacuum is enabled */
499 public bool incrVacuum; /* True if incr-vacuum is enabled */
500 #endif
501 public u8 inTransaction; /* Transaction state */
502 public bool doNotUseWAL; /* If true, do not open write-ahead-log file */
503 public u16 maxLocal; /* Maximum local payload in non-LEAFDATA tables */
504 public u16 minLocal; /* Minimum local payload in non-LEAFDATA tables */
505 public u16 maxLeaf; /* Maximum local payload in a LEAFDATA table */
506 public u16 minLeaf; /* Minimum local payload in a LEAFDATA table */
507 public u32 pageSize; /* Total number of bytes on a page */
508 public u32 usableSize; /* Number of usable bytes on each page */
509 public int nTransaction; /* Number of open transactions (read + write) */
510 public Pgno nPage; /* Number of pages in the database */
511 public Schema pSchema; /* Pointer to space allocated by sqlite3BtreeSchema() */
512 public dxFreeSchema xFreeSchema;/* Destructor for BtShared.pSchema */
513 public sqlite3_mutex mutex; /* Non-recursive mutex required to access this object */
514 public Bitvec pHasContent; /* Set of pages moved to free-list this transaction */
515 #if !SQLITE_OMIT_SHARED_CACHE
516 public int nRef; /* Number of references to this structure */
517 public BtShared pNext; /* Next on a list of sharable BtShared structs */
518 public BtLock pLock; /* List of locks held on this shared-btree struct */
519 public Btree pWriter; /* Btree with currently open write transaction */
520 public u8 isExclusive; /* True if pWriter has an EXCLUSIVE lock on the db */
521 public u8 isPending; /* If waiting for read-locks to clear */
522 #endif
523 public byte[] pTmpSpace; /* BtShared.pageSize bytes of space for tmp use */
524 };
525  
526 /*
527 ** An instance of the following structure is used to hold information
528 ** about a cell. The parseCellPtr() function fills in this structure
529 ** based on information extract from the raw disk page.
530 */
531 //typedef struct CellInfo CellInfo;
532 public struct CellInfo
533 {
534 public int iCell; /* Offset to start of cell content -- Needed for C# */
535 public byte[] pCell; /* Pointer to the start of cell content */
536 public i64 nKey; /* The key for INTKEY tables, or number of bytes in key */
537 public u32 nData; /* Number of bytes of data */
538 public u32 nPayload; /* Total amount of payload */
539 public u16 nHeader; /* Size of the cell content header in bytes */
540 public u16 nLocal; /* Amount of payload held locally */
541 public u16 iOverflow; /* Offset to overflow page number. Zero if no overflow */
542 public u16 nSize; /* Size of the cell content on the main b-tree page */
543 public bool Equals( CellInfo ci )
544 {
545 if ( ci.iCell >= ci.pCell.Length || iCell >= this.pCell.Length )
546 return false;
547 if ( ci.pCell[ci.iCell] != this.pCell[iCell] )
548 return false;
549 if ( ci.nKey != this.nKey || ci.nData != this.nData || ci.nPayload != this.nPayload )
550 return false;
551 if ( ci.nHeader != this.nHeader || ci.nLocal != this.nLocal )
552 return false;
553 if ( ci.iOverflow != this.iOverflow || ci.nSize != this.nSize )
554 return false;
555 return true;
556 }
557 };
558  
559 /*
560 ** Maximum depth of an SQLite B-Tree structure. Any B-Tree deeper than
561 ** this will be declared corrupt. This value is calculated based on a
562 ** maximum database size of 2^31 pages a minimum fanout of 2 for a
563 ** root-node and 3 for all other internal nodes.
564 **
565 ** If a tree that appears to be taller than this is encountered, it is
566 ** assumed that the database is corrupt.
567 */
568 //#define BTCURSOR_MAX_DEPTH 20
569 const int BTCURSOR_MAX_DEPTH = 20;
570  
571 /*
572 ** A cursor is a pointer to a particular entry within a particular
573 ** b-tree within a database file.
574 **
575 ** The entry is identified by its MemPage and the index in
576 ** MemPage.aCell[] of the entry.
577 **
578 ** A single database file can shared by two more database connections,
579 ** but cursors cannot be shared. Each cursor is associated with a
580 ** particular database connection identified BtCursor.pBtree.db.
581 **
582 ** Fields in this structure are accessed under the BtShared.mutex
583 ** found at self.pBt.mutex.
584 */
585 public class BtCursor
586 {
587 public Btree pBtree; /* The Btree to which this cursor belongs */
588 public BtShared pBt; /* The BtShared this cursor points to */
589 public BtCursor pNext;
590 public BtCursor pPrev; /* Forms a linked list of all cursors */
591 public KeyInfo pKeyInfo; /* Argument passed to comparison function */
592 public Pgno pgnoRoot; /* The root page of this tree */
593 public sqlite3_int64 cachedRowid; /* Next rowid cache. 0 means not valid */
594 public CellInfo info = new CellInfo(); /* A parse of the cell we are pointing at */
595 public byte[] pKey; /* Saved key that was cursor's last known position */
596 public i64 nKey; /* Size of pKey, or last integer key */
597 public int skipNext; /* Prev() is noop if negative. Next() is noop if positive */
598 public u8 wrFlag; /* True if writable */
599 public u8 atLast; /* VdbeCursor pointing to the last entry */
600 public bool validNKey; /* True if info.nKey is valid */
601 public int eState; /* One of the CURSOR_XXX constants (see below) */
602 #if !SQLITE_OMIT_INCRBLOB
603 public Pgno[] aOverflow; /* Cache of overflow page locations */
604 public bool isIncrblobHandle; /* True if this cursor is an incr. io handle */
605 #endif
606 public i16 iPage; /* Index of current page in apPage */
607 public u16[] aiIdx = new u16[BTCURSOR_MAX_DEPTH]; /* Current index in apPage[i] */
608 public MemPage[] apPage = new MemPage[BTCURSOR_MAX_DEPTH]; /* Pages from root to current page */
609  
610 public void Clear()
611 {
612 pNext = null;
613 pPrev = null;
614 pKeyInfo = null;
615 pgnoRoot = 0;
616 cachedRowid = 0;
617 info = new CellInfo();
618 wrFlag = 0;
619 atLast = 0;
620 validNKey = false;
621 eState = 0;
622 pKey = null;
623 nKey = 0;
624 skipNext = 0;
625 #if !SQLITE_OMIT_INCRBLOB
626 isIncrblobHandle=false;
627 aOverflow= null;
628 #endif
629 iPage = 0;
630 }
631 public BtCursor Copy()
632 {
633 BtCursor cp = (BtCursor)MemberwiseClone();
634 return cp;
635 }
636 };
637  
638 /*
639 ** Potential values for BtCursor.eState.
640 **
641 ** CURSOR_VALID:
642 ** VdbeCursor points to a valid entry. getPayload() etc. may be called.
643 **
644 ** CURSOR_INVALID:
645 ** VdbeCursor does not point to a valid entry. This can happen (for example)
646 ** because the table is empty or because BtreeCursorFirst() has not been
647 ** called.
648 **
649 ** CURSOR_REQUIRESEEK:
650 ** The table that this cursor was opened on still exists, but has been
651 ** modified since the cursor was last used. The cursor position is saved
652 ** in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in
653 ** this state, restoreCursorPosition() can be called to attempt to
654 ** seek the cursor to the saved position.
655 **
656 ** CURSOR_FAULT:
657 ** A unrecoverable error (an I/O error or a malloc failure) has occurred
658 ** on a different connection that shares the BtShared cache with this
659 ** cursor. The error has left the cache in an inconsistent state.
660 ** Do nothing else with this cursor. Any attempt to use the cursor
661 ** should return the error code stored in BtCursor.skip
662 */
663 const int CURSOR_INVALID = 0;
664 const int CURSOR_VALID = 1;
665 const int CURSOR_REQUIRESEEK = 2;
666 const int CURSOR_FAULT = 3;
667  
668 /*
669 ** The database page the PENDING_BYTE occupies. This page is never used.
670 */
671 //# define PENDING_BYTE_PAGE(pBt) PAGER_MJ_PGNO(pBt)
672 // TODO -- Convert PENDING_BYTE_PAGE to inline
673 static u32 PENDING_BYTE_PAGE( BtShared pBt )
674 {
675 return (u32)PAGER_MJ_PGNO( pBt.pPager );
676 }
677  
678 /*
679 ** These macros define the location of the pointer-map entry for a
680 ** database page. The first argument to each is the number of usable
681 ** bytes on each page of the database (often 1024). The second is the
682 ** page number to look up in the pointer map.
683 **
684 ** PTRMAP_PAGENO returns the database page number of the pointer-map
685 ** page that stores the required pointer. PTRMAP_PTROFFSET returns
686 ** the offset of the requested map entry.
687 **
688 ** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page,
689 ** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be
690 ** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements
691 ** this test.
692 */
693 //#define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno)
694 static Pgno PTRMAP_PAGENO( BtShared pBt, Pgno pgno )
695 {
696 return ptrmapPageno( pBt, pgno );
697 }
698 //#define PTRMAP_PTROFFSET(pgptrmap, pgno) (5*(pgno-pgptrmap-1))
699 static u32 PTRMAP_PTROFFSET( u32 pgptrmap, u32 pgno )
700 {
701 return ( 5 * ( pgno - pgptrmap - 1 ) );
702 }
703 //#define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno))
704 static bool PTRMAP_ISPAGE( BtShared pBt, u32 pgno )
705 {
706 return ( PTRMAP_PAGENO( ( pBt ), ( pgno ) ) == ( pgno ) );
707 }
708 /*
709 ** The pointer map is a lookup table that identifies the parent page for
710 ** each child page in the database file. The parent page is the page that
711 ** contains a pointer to the child. Every page in the database contains
712 ** 0 or 1 parent pages. (In this context 'database page' refers
713 ** to any page that is not part of the pointer map itself.) Each pointer map
714 ** entry consists of a single byte 'type' and a 4 byte parent page number.
715 ** The PTRMAP_XXX identifiers below are the valid types.
716 **
717 ** The purpose of the pointer map is to facility moving pages from one
718 ** position in the file to another as part of autovacuum. When a page
719 ** is moved, the pointer in its parent must be updated to point to the
720 ** new location. The pointer map is used to locate the parent page quickly.
721 **
722 ** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not
723 ** used in this case.
724 **
725 ** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number
726 ** is not used in this case.
727 **
728 ** PTRMAP_OVERFLOW1: The database page is the first page in a list of
729 ** overflow pages. The page number identifies the page that
730 ** contains the cell with a pointer to this overflow page.
731 **
732 ** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of
733 ** overflow pages. The page-number identifies the previous
734 ** page in the overflow page list.
735 **
736 ** PTRMAP_BTREE: The database page is a non-root btree page. The page number
737 ** identifies the parent page in the btree.
738 */
739 //#define PTRMAP_ROOTPAGE 1
740 //#define PTRMAP_FREEPAGE 2
741 //#define PTRMAP_OVERFLOW1 3
742 //#define PTRMAP_OVERFLOW2 4
743 //#define PTRMAP_BTREE 5
744 const int PTRMAP_ROOTPAGE = 1;
745 const int PTRMAP_FREEPAGE = 2;
746 const int PTRMAP_OVERFLOW1 = 3;
747 const int PTRMAP_OVERFLOW2 = 4;
748 const int PTRMAP_BTREE = 5;
749  
750 /* A bunch of Debug.Assert() statements to check the transaction state variables
751 ** of handle p (type Btree*) are internally consistent.
752 */
753 #if DEBUG
754 //#define btreeIntegrity(p) \
755 // Debug.Assert( p.pBt.inTransaction!=TRANS_NONE || p.pBt.nTransaction==0 ); \
756 // Debug.Assert( p.pBt.inTransaction>=p.inTrans );
757 static void btreeIntegrity( Btree p )
758 {
759 Debug.Assert( p.pBt.inTransaction != TRANS_NONE || p.pBt.nTransaction == 0 );
760 Debug.Assert( p.pBt.inTransaction >= p.inTrans );
761 }
762 #else
763 static void btreeIntegrity(Btree p) { }
764 #endif
765  
766 /*
767 ** The ISAUTOVACUUM macro is used within balance_nonroot() to determine
768 ** if the database supports auto-vacuum or not. Because it is used
769 ** within an expression that is an argument to another macro
770 ** (sqliteMallocRaw), it is not possible to use conditional compilation.
771 ** So, this macro is defined instead.
772 */
773 #if !SQLITE_OMIT_AUTOVACUUM
774 //#define ISAUTOVACUUM (pBt.autoVacuum)
775 #else
776 //#define ISAUTOVACUUM 0
777 public static bool ISAUTOVACUUM =false;
778 #endif
779  
780  
781 /*
782 ** This structure is passed around through all the sanity checking routines
783 ** in order to keep track of some global state information.
784 */
785 //typedef struct IntegrityCk IntegrityCk;
786 public class IntegrityCk
787 {
788 public BtShared pBt; /* The tree being checked out */
789 public Pager pPager; /* The associated pager. Also accessible by pBt.pPager */
790 public Pgno nPage; /* Number of pages in the database */
791 public int[] anRef; /* Number of times each page is referenced */
792 public int mxErr; /* Stop accumulating errors when this reaches zero */
793 public int nErr; /* Number of messages written to zErrMsg so far */
794 //public int mallocFailed; /* A memory allocation error has occurred */
795 public StrAccum errMsg = new StrAccum( 100 ); /* Accumulate the error message text here */
796 };
797  
798 /*
799 ** Read or write a two- and four-byte big-endian integer values.
800 */
801 //#define get2byte(x) ((x)[0]<<8 | (x)[1])
802 static int get2byte( byte[] p, int offset )
803 {
804 return p[offset + 0] << 8 | p[offset + 1];
805 }
806  
807 //#define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v))
808 static void put2byte( byte[] pData, int Offset, u32 v )
809 {
810 pData[Offset + 0] = (byte)( v >> 8 );
811 pData[Offset + 1] = (byte)v;
812 }
813 static void put2byte( byte[] pData, int Offset, int v )
814 {
815 pData[Offset + 0] = (byte)( v >> 8 );
816 pData[Offset + 1] = (byte)v;
817 }
818  
819 //#define get4byte sqlite3Get4byte
820 //#define put4byte sqlite3Put4byte
821  
822 }
823 }