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Overview
Comment:continued work on btree (CVS 222)
Downloads: Tarball | ZIP archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: d07e0e80a0b33081adda8651e9a6750b2e40141a
User & Date: drh 2001-06-02 02:40:57.000
Context
2001-06-08
00:21
incremental update (CVS 223) (check-in: 7108b699cc user: drh tags: trunk)
2001-06-02
02:40
continued work on btree (CVS 222) (check-in: d07e0e80a0 user: drh tags: trunk)
2001-05-28
00:41
:-) (CVS 1720) (check-in: d78febd197 user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/btree.c.
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** Boston, MA  02111-1307, USA.
**
** Author contact information:
**   drh@hwaci.com
**   http://www.hwaci.com/drh/
**
*************************************************************************
** $Id: btree.c,v 1.9 2001/05/28 00:41:15 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include <assert.h>


/*
** Primitive data types.  u32 must be 4 bytes and u16 must be 2 bytes.
** Change these typedefs when porting to new architectures.
*/
typedef unsigned int u32;
typedef unsigned short int u16;
typedef unsigned char u8;

/*
** Forward declarations of structures used only in this file.
*/
typedef struct Page1Header Page1Header;
typedef struct MemPage MemPage;
typedef struct PageHdr PageHdr;
typedef struct Cell Cell;
typedef struct CellHdr CellHdr;
typedef struct FreeBlk FreeBlk;
typedef struct OverflowPage OverflowPage;

/*
** All structures on a database page are aligned to 4-byte boundries.
** This routine rounds up a number of bytes to the next multiple of 4.
**
** This might need to change for computer architectures that require
** and 8-byte alignment boundry for structures.
*/
#define ROUNDUP(X)  ((X+3) & ~3)

/*








** The first page of the database file contains some additional
** information used for housekeeping and sanity checking.  Otherwise,





** the first page is just like any other.  The additional information
** found on the first page is described by the following structure.

*/
struct Page1Header {
  u32 magic1;       /* A magic number to verify the file really is a database */
  u32 magic2;       /* A second magic number to be extra sure */

  Pgno firstList;   /* First free page in a list of all free pages */
};
#define MAGIC_1  0x7264dc61
#define MAGIC_2  0x54e55d9e

/*
** Each database page has a header as follows:
**
**      page1_header          Optional instance of Page1Header structure
**      rightmost_pgno        Page number of the right-most child page
**      first_cell            Index into MemPage.aDisk of first cell
**      first_free            Index of first free block
**
** MemPage.pHdr always points to the rightmost_pgno.  First_free is
** 0 if there is no free space on this page.  Otherwise, first_free is
** the index in MemPage.aDisk[] of a FreeBlk structure that describes
** the first block of free space.  All free space is defined by a linked
** list of FreeBlk structures.
**
** Data is stored in a linked list of Cell structures.  First_cell is
** the index into MemPage.aDisk[] of the first cell on the page.  The
** Cells are kept in sorted order.
*/
struct PageHdr {
  Pgno rightChild;  /* Child page that comes after all cells on this page */
  u16 firstCell;    /* Index in MemPage.aDisk[] of the first cell */
  u16 firstFree;    /* Index in MemPage.aDisk[] of the first free block */
};


/*
** Entries on a page of the database are called "Cells".  Each Cell
** has a header and data.  This structure defines the header.  The



** definition of the complete Cell including the data is given below.


*/
struct CellHdr {
  Pgno leftChild; /* Child page that comes before this cell */
  u16 nKey;       /* Number of bytes in the key */
  u16 iNext;      /* Index in MemPage.aDisk[] of next cell in sorted order */
  u32 nData;      /* Number of bytes of data */
}

/*
** The minimum size of a complete Cell.  The Cell must contain a header
** and at least 4 bytes of data.
*/
#define MIN_CELL_SIZE  (sizeof(CellHdr)+4)

/*
** The maximum number of database entries that can be held in a single
** page of the database. 
*/
#define MX_CELL ((SQLITE_PAGE_SIZE-sizeof(PageHdr))/MIN_CELL_SIZE)

/*
** The maximum amount of data (in bytes) that can be stored locally for a
** database entry.  If the entry contains more data than this, the
** extra goes onto overflow pages.


*/
#define MX_LOCAL_PAYLOAD \
  ((SQLITE_PAGE_SIZE-sizeof(PageHdr))/4-(sizeof(CellHdr)+sizeof(Pgno)))

/*
** Data on a database page is stored as a linked list of Cell structures.
** Both the key and the data are stored in aPayload[].  The key always comes
** first.  The aPayload[] field grows as necessary to hold the key and data,
** up to a maximum of MX_LOCAL_PAYLOAD bytes.  If the size of the key and
** data combined exceeds MX_LOCAL_PAYLOAD bytes, then Cell.ovfl is the
** page number of the first overflow page.
**
** Though this structure is fixed in size, the Cell on the database
** page varies in size.  Very cell has a CellHdr and at least 4 bytes
** of payload space.  Additional payload bytes (up to the maximum of
** MX_LOCAL_PAYLOAD) and the Cell.ovfl value are allocated only as
** needed.
*/
struct Cell {
  CellHdr h;                        /* The cell header */
  char aPayload[MX_LOCAL_PAYLOAD];  /* Key and data */








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** Boston, MA  02111-1307, USA.
**
** Author contact information:
**   drh@hwaci.com
**   http://www.hwaci.com/drh/
**
*************************************************************************
** $Id: btree.c,v 1.10 2001/06/02 02:40:57 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include <assert.h>


/*
** Primitive data types.  u32 must be 4 bytes and u16 must be 2 bytes.
** Change these typedefs when porting to new architectures.
*/
typedef unsigned int u32;
typedef unsigned short int u16;
typedef unsigned char u8;

/*
** Forward declarations of structures used only in this file.
*/
typedef struct PageOne PageOne;
typedef struct MemPage MemPage;
typedef struct PageHdr PageHdr;
typedef struct Cell Cell;
typedef struct CellHdr CellHdr;
typedef struct FreeBlk FreeBlk;
typedef struct OverflowPage OverflowPage;

/*
** All structures on a database page are aligned to 4-byte boundries.
** This routine rounds up a number of bytes to the next multiple of 4.
**
** This might need to change for computer architectures that require
** and 8-byte alignment boundry for structures.
*/
#define ROUNDUP(X)  ((X+3) & ~3)

/*
** This is a magic string that appears at the beginning of every
** SQLite database in order to identify the fail as a real database.
*/
static const char zMagicHeader[] = 
   "** This file contains an SQLite 2.0 database **"
#define MAGIC_SIZE (sizeof(zMagicHeader))

/*
** The first page of the database file contains a magic header string

** to identify the file as an SQLite database file.  It also contains
** a pointer to the first free page of the file.  Page 2 contains the
** root of the BTree.
**
** Remember that pages are numbered beginning with 1.  (See pager.c
** for additional information.)  Page 0 does not exist and a page

** number of 0 is used to mean "no such page".
*/
struct PageOne {


  char zMagic[MAGIC_SIZE]; /* String that identifies the file as a database */
  Pgno firstList;          /* First free page in a list of all free pages */
};



/*
** Each database page has a header that is an instance of this
** structure.




**
** MemPage.pHdr always points to the rightmost_pgno.  First_free is
** 0 if there is no free space on this page.  Otherwise, first_free is
** the index in MemPage.aDisk[] of a FreeBlk structure that describes
** the first block of free space.  All free space is defined by a linked
** list of FreeBlk structures.
**
** Data is stored in a linked list of Cell structures.  First_cell is
** the index into MemPage.aDisk[] of the first cell on the page.  The
** Cells are kept in sorted order.
*/
struct PageHdr {
  Pgno rightChild;  /* Child page that comes after all cells on this page */
  u16 firstCell;    /* Index in MemPage.aDisk[] of the first cell */
  u16 firstFree;    /* Index in MemPage.aDisk[] of the first free block */
};


/*
** Entries on a page of the database are called "Cells".  Each Cell
** has a header and data.  This structure defines the header.  The
** key and data (collectively the "payload") follow this header on
** the database page.
**
** A definition of the complete Cell structure is given below.  The
** header for the cell must be defined separately in order to do some
** of the sizing #defines that follow.
*/
struct CellHdr {
  Pgno leftChild; /* Child page that comes before this cell */
  u16 nKey;       /* Number of bytes in the key */
  u16 iNext;      /* Index in MemPage.aDisk[] of next cell in sorted order */
  u32 nData;      /* Number of bytes of data */
}

/*
** The minimum size of a complete Cell.  The Cell must contain a header
** and at least 4 bytes of payload.
*/
#define MIN_CELL_SIZE  (sizeof(CellHdr)+4)

/*
** The maximum number of database entries that can be held in a single
** page of the database. 
*/
#define MX_CELL ((SQLITE_PAGE_SIZE-sizeof(PageHdr))/MIN_CELL_SIZE)

/*
** The maximum amount of data (in bytes) that can be stored locally for a
** database entry.  If the entry contains more data than this, the
** extra goes onto overflow pages.
**
** This number is chosen so that at least 4 cells will fit on every page.
*/
#define MX_LOCAL_PAYLOAD \
  ((SQLITE_PAGE_SIZE-sizeof(PageHdr))/4-(sizeof(CellHdr)+sizeof(Pgno)))

/*
** Data on a database page is stored as a linked list of Cell structures.
** Both the key and the data are stored in aPayload[].  The key always comes
** first.  The aPayload[] field grows as necessary to hold the key and data,
** up to a maximum of MX_LOCAL_PAYLOAD bytes.  If the size of the key and
** data combined exceeds MX_LOCAL_PAYLOAD bytes, then Cell.ovfl is the
** page number of the first overflow page.
**
** Though this structure is fixed in size, the Cell on the database
** page varies in size.  Every cell has a CellHdr and at least 4 bytes
** of payload space.  Additional payload bytes (up to the maximum of
** MX_LOCAL_PAYLOAD) and the Cell.ovfl value are allocated only as
** needed.
*/
struct Cell {
  CellHdr h;                        /* The cell header */
  char aPayload[MX_LOCAL_PAYLOAD];  /* Key and data */
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/*
** When the key and data for a single entry in the BTree will not fit in
** the MX_LOACAL_PAYLOAD bytes of space available on the database page,
** then all extra data is written to a linked list of overflow pages.
** Each overflow page is an instance of the following structure.
**
** Unused pages in the database are also represented by instances of
** the OverflowPage structure.  The Page1Header.freeList field is the
** page number of the first page in a linked list of unused database
** pages.
*/
struct OverflowPage {
  Pgno next;
  char aPayload[OVERFLOW_SIZE];
};

/*
** For every page in the database file, an instance of the following structure
** is stored in memory.  The aDisk[] array contains the data obtained from
** the disk.  The rest is auxiliary data that held in memory only.  The
** auxiliary data is only valid for regular database pages - the auxiliary
** data is meaningless for overflow pages and pages on the freelist.
**
** Of particular interest in the auxiliary data is the apCell[] entry.  Each
** apCell[] entry is a pointer to a Cell structure in aDisk[].  The cells are
** put in this array so that they can be accessed in constant time, rather
** than in linear time which would be needed if we walked the linked list.

**
** 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.
*/
struct MemPage {
  char aDisk[SQLITE_PAGE_SIZE];  /* Page data stored on disk */
  int isInit;                    /* True if auxiliary data is initialized */
  MemPage *pParent;              /* The parent of this page.  NULL for root */
  int idxStart;                  /* Index in aDisk[] of real data */
  PageHdr *pHdr;                 /* Points to aDisk[idxStart] */
  int nFree;                     /* Number of free bytes in aDisk[] */
  int nCell;                     /* Number of entries on this page */
  Cell *apCell[MX_CELL];         /* All data entires in sorted order */
}

/*
** 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)-SQLITE_PAGE_SIZE)

/*
** Everything we need to know about an open database
*/
struct Btree {
  Pager *pPager;        /* The page cache */
  BtCursor *pCursor;    /* A list of all open cursors */
  MemPage *page1;       /* First page of the database */
  int inTrans;          /* True if a transaction is in progress */
};
typedef Btree Bt;

/*
** A cursor is a pointer to a particular entry in the BTree.
** The entry is identified by its MemPage and the index in








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/*
** When the key and data for a single entry in the BTree will not fit in
** the MX_LOACAL_PAYLOAD bytes of space available on the database page,
** then all extra data is written to a linked list of overflow pages.
** Each overflow page is an instance of the following structure.
**
** Unused pages in the database are also represented by instances of
** the OverflowPage structure.  The PageOne.freeList field is the
** page number of the first page in a linked list of unused database
** pages.
*/
struct OverflowPage {
  Pgno next;
  char aPayload[OVERFLOW_SIZE];
};

/*
** For every page in the database file, an instance of the following structure
** is stored in memory.  The aDisk[] array contains the raw bits read from
** the disk.  The rest is auxiliary information that held in memory only. The
** auxiliary info is only valid for regular database pages - it is not
** used for overflow pages and pages on the freelist.
**
** Of particular interest in the auxiliary info is the apCell[] entry.  Each
** apCell[] entry is a pointer to a Cell structure in aDisk[].  The cells are
** put in this array so that they can be accessed in constant time, rather
** than in linear time which would be needed if we had to walk the linked 
** list on every access.
**
** 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.
*/
struct MemPage {
  char aDisk[SQLITE_PAGE_SIZE];  /* Page data stored on disk */
  int isInit;                    /* True if auxiliary data is initialized */
  MemPage *pParent;              /* The parent of this page.  NULL for root */


  int nFree;                     /* Number of free bytes in aDisk[] */
  int nCell;                     /* Number of entries on this page */
  Cell *apCell[MX_CELL];         /* All data entires in sorted order */
}

/*
** 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)-SQLITE_PAGE_SIZE)

/*
** Everything we need to know about an open database
*/
struct Btree {
  Pager *pPager;        /* The page cache */
  BtCursor *pCursor;    /* A list of all open cursors */
  PageOne *page1;       /* First page of the database */
  int inTrans;          /* True if a transaction is in progress */
};
typedef Btree Bt;

/*
** A cursor is a pointer to a particular entry in the BTree.
** The entry is identified by its MemPage and the index in
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  u8 iMatch;                /* compare result from last sqliteBtreeMoveto() */
};

/*
** Compute the total number of bytes that a Cell needs on the main
** database page.  The number returned includes the Cell header,
** local payload storage, and the pointer to overflow pages (if
** applicable).  The point of this routine is that it does not
** include payload storage on overflow pages.
*/
static int cellSize(Cell *pCell){
  int n = pCell->h.nKey + pCell->h.nData;
  if( n>MX_LOCAL_PAYLOAD ){
    n = MX_LOCAL_PAYLOAD + sizeof(Pgno);
  }else{
    n = ROUNDUP(n);








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  u8 iMatch;                /* compare result from last sqliteBtreeMoveto() */
};

/*
** Compute the total number of bytes that a Cell needs on the main
** database page.  The number returned includes the Cell header,
** local payload storage, and the pointer to overflow pages (if
** applicable).  Additional spaced allocated on overflow pages
** is NOT included in the value returned from this routine.
*/
static int cellSize(Cell *pCell){
  int n = pCell->h.nKey + pCell->h.nData;
  if( n>MX_LOCAL_PAYLOAD ){
    n = MX_LOCAL_PAYLOAD + sizeof(Pgno);
  }else{
    n = ROUNDUP(n);
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*/
static void defragmentPage(MemPage *pPage){
  int pc;
  int i, n;
  FreeBlk *pFBlk;
  char newPage[SQLITE_PAGE_SIZE];

  pc = ROUNDUP(pPage->idxStart + sizeof(PageHdr));
  pPage->pHdr->firstCell = pc;
  memcpy(newPage, pPage->aDisk, pc);
  for(i=0; i<pPage->nCell; i++){
    Cell *pCell = &pPage->apCell[i];
    n = cellSize(pCell);
    pCell->h.iNext = i<pPage->nCell ? pc + n : 0;
    memcpy(&newPage[pc], pCell, n);
    pPage->apCell[i] = (Cell*)&pPage->aDisk[pc];
    pc += n;
  }
  assert( pPage->nFree==SQLITE_PAGE_SIZE-pc );
  memcpy(pPage->aDisk, newPage, pc);
  pFBlk = &pPage->aDisk[pc];
  pFBlk->iSize = SQLITE_PAGE_SIZE - pc;
  pFBlk->iNext = 0;
  pPage->pHdr->firstFree = pc;
  memset(&pFBlk[1], 0, SQLITE_PAGE_SIZE - pc - sizeof(FreeBlk));
}

/*
** Allocate space on a page.  The space needs to be at least
** nByte bytes in size.  (Actually, all allocations are rounded
** up to the next even multiple of 4.)  Return the index into
** pPage->aDisk[] of the first byte of the new allocation.
** Or return 0 if there is not enough free space on the page to
** satisfy the allocation request.
**
** If the page contains nBytes of free space but does not contain
** nBytes of contiguous free space, then defragementPage() is
** called to consolidate all free space before allocating the
** new chunk.
*/
static int allocSpace(MemPage *pPage, int nByte){
  FreeBlk *p;
  u16 *pIdx;
  int start;

  assert( nByte==ROUNDUP(nByte) );
  if( pPage->nFree<nByte ) return 0;
  pIdx = &pPage->pHdr->firstFree;
  p = (FreeBlk*)&pPage->aDisk[*pIdx];
  while( p->iSize<nByte ){
    if( p->iNext==0 ){
      defragmentPage(pPage);
      pIdx = &pPage->pHdr->firstFree;
    }else{
      pIdx = &p->iNext;
    }
    p = (FreeBlk*)&pPage->aDisk[*pIdx];
  }
  if( p->iSize==nByte ){
    start = *pIdx;








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*/
static void defragmentPage(MemPage *pPage){
  int pc;
  int i, n;
  FreeBlk *pFBlk;
  char newPage[SQLITE_PAGE_SIZE];

  pc = sizeof(PageHdr);
  ((PageHdr*)pPage)->firstCell = pc;
  memcpy(newPage, pPage->aDisk, pc);
  for(i=0; i<pPage->nCell; i++){
    Cell *pCell = &pPage->apCell[i];
    n = cellSize(pCell);
    pCell->h.iNext = i<pPage->nCell ? pc + n : 0;
    memcpy(&newPage[pc], pCell, n);
    pPage->apCell[i] = (Cell*)&pPage->aDisk[pc];
    pc += n;
  }
  assert( pPage->nFree==SQLITE_PAGE_SIZE-pc );
  memcpy(pPage->aDisk, newPage, pc);
  pFBlk = &pPage->aDisk[pc];
  pFBlk->iSize = SQLITE_PAGE_SIZE - pc;
  pFBlk->iNext = 0;
  ((PageHdr*)pPage)->firstFree = pc;
  memset(&pFBlk[1], 0, SQLITE_PAGE_SIZE - pc - sizeof(FreeBlk));
}

/*
** Allocate space on a page.  The space needs to be at least
** nByte bytes in size.  nByte must be a multiple of 4.
**
** Return the index into pPage->aDisk[] of the first byte of
** the new allocation. Or return 0 if there is not enough free
** space on the page to satisfy the allocation request.
**
** If the page contains nBytes of free space but does not contain
** nBytes of contiguous free space, then defragementPage() is
** called to consolidate all free space before allocating the
** new chunk.
*/
static int allocateSpace(MemPage *pPage, int nByte){
  FreeBlk *p;
  u16 *pIdx;
  int start;

  assert( nByte==ROUNDUP(nByte) );
  if( pPage->nFree<nByte ) return 0;
  pIdx = &((PageHdr*)pPage)->firstFree;
  p = (FreeBlk*)&pPage->aDisk[*pIdx];
  while( p->iSize<nByte ){
    if( p->iNext==0 ){
      defragmentPage(pPage);
      pIdx = &((PageHdr*)pPage)->firstFree;
    }else{
      pIdx = &p->iNext;
    }
    p = (FreeBlk*)&pPage->aDisk[*pIdx];
  }
  if( p->iSize==nByte ){
    start = *pIdx;
︙︙
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361

  u16 *pIdx, idx;
  FreeBlk *pFBlk;
  FreeBlk *pNew;
  FreeBlk *pNext;

  assert( size == ROUNDUP(size) );
  assert( start == ROUNDUP(start) );
  pIdx = &pPage->pHdr->firstFree;
  idx = *pIdx;
  while( idx!=0 && idx<start ){
    pFBlk = (FreeBlk*)&pPage->aDisk[idx];
    if( idx + pFBlk->iSize == start ){
      pFBlk->iSize += size;
      if( idx + pFBlk->iSize == pFBlk->iNext ){
        pNext = (FreeBlk*)&pPage->aDisk[pFblk->iNext];








|








357
358
359
360
361
362
363
364
365
366
367
368
369
370
371

  u16 *pIdx, idx;
  FreeBlk *pFBlk;
  FreeBlk *pNew;
  FreeBlk *pNext;

  assert( size == ROUNDUP(size) );
  assert( start == ROUNDUP(start) );
  pIdx = &((PageHdr*)pPage)->firstFree;
  idx = *pIdx;
  while( idx!=0 && idx<start ){
    pFBlk = (FreeBlk*)&pPage->aDisk[idx];
    if( idx + pFBlk->iSize == start ){
      pFBlk->iSize += size;
      if( idx + pFBlk->iSize == pFBlk->iNext ){
        pNext = (FreeBlk*)&pPage->aDisk[pFblk->iNext];
︙︙
380
381
382
383
384
385
386
387


388
389
390
391
392
393
394

  *pIdx = start;
  pPage->nFree += size;
}

/*
** Initialize the auxiliary information for a disk block.
**
** The pParent field is always


**
** Return SQLITE_OK on success.  If we see that the page does
** not contained a well-formed database page, then return 
** SQLITE_CORRUPT.  Note that a return of SQLITE_OK does not
** guarantee that the page is well-formed.  It only shows that
** we failed to detect any corruption.
*/








|
>
>








390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406

  *pIdx = start;
  pPage->nFree += size;
}

/*
** Initialize the auxiliary information for a disk block.
**
** The pParent parameter must be a pointer to the MemPage which
** is the parent of the page being initialized.  The root of the
** BTree (page 2) has no parent and so for that page, pParent==NULL.
**
** Return SQLITE_OK on success.  If we see that the page does
** not contained a well-formed database page, then return 
** SQLITE_CORRUPT.  Note that a return of SQLITE_OK does not
** guarantee that the page is well-formed.  It only shows that
** we failed to detect any corruption.
*/
︙︙
404
405
406
407
408
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410
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413
414
415
416
417
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423
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434
435
436
437
438
439
440
441
442













































443
444
445
446
447
448
449

    return SQLITE_OK;
  }
  if( pParent ){
    pPage->pParent = pParent;
    sqlitepager_ref(pParent);
  }
  if( pPage->isInit ) return SQLITE_OK;
  pPage->idxStart = (pgnoThis==1) ? sizeof(Page1Header) : 0;
  pPage->pHdr = (PageHdr*)&pPage->aDisk[pPage->idxStart];
  pPage->isInit = 1;
  pPage->nCell = 0;
  freeSpace = SQLITE_PAGE_SIZE - pPage->idxStart - sizeof(PageHeader);
  idx = pPage->pHdr->firstCell;
  while( idx!=0 ){
    if( idx>SQLITE_PAGE_SIZE-MN_CELL_SIZE ) goto page_format_error;
    if( idx<pPage->idxStart + sizeof(PageHeader) ) goto page_format_error;
    pCell = (Cell*)&pPage->aDisk[idx];
    sz = cellSize(pCell);
    if( idx+sz > SQLITE_PAGE_SIZE ) goto page_format_error;
    freeSpace -= sz;
    pPage->apCell[pPage->nCell++] = pCell;
    idx = pCell->h.iNext;
  }
  pPage->nFree = 0;
  idx = pPage->pHdr->firstFree;
  while( idx!=0 ){
    if( idx>SQLITE_PAGE_SIZE-sizeof(FreeBlk) ) goto page_format_error;
    if( idx<pPage->idxStart + sizeof(PageHeader) ) goto page_format_error;
    pFBlk = (FreeBlk*)&pPage->aDisk[idx];
    pPage->nFree += pFBlk->iSize;
    if( pFBlk->iNext <= idx ) goto page_format_error;
    idx = pFBlk->iNext;
  }
  if( pPage->nFree!=freeSpace ) goto page_format_error;
  return SQLITE_OK;

page_format_error:
  return SQLITE_CORRUPT;
}














































/*
** This routine is called when the reference count for a page
** reaches zero.  We need to unref the pParent pointer when that
** happens.
*/
static void pageDestructor(void *pData){








<
<


|
|


|








|


|











>
>
>
>
>
>
>
>
>
>
>
>
>
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>
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>
>
>
>
>








416
417
418
419
420
421
422


423
424
425
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428
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436
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440
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446
447
448
449
450
451
452
453
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455
456
457
458
459
460
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462
463
464
465
466
467
468
469
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473
474
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482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504

    return SQLITE_OK;
  }
  if( pParent ){
    pPage->pParent = pParent;
    sqlitepager_ref(pParent);
  }
  if( pPage->isInit ) return SQLITE_OK;


  pPage->isInit = 1;
  pPage->nCell = 0;
  freeSpace = SQLITE_PAGE_SIZE - sizeof(PageHdr);
  idx = ((PageHdr*)pPage)->firstCell;
  while( idx!=0 ){
    if( idx>SQLITE_PAGE_SIZE-MN_CELL_SIZE ) goto page_format_error;
    if( idx<sizeof(PageHdr) ) goto page_format_error;
    pCell = (Cell*)&pPage->aDisk[idx];
    sz = cellSize(pCell);
    if( idx+sz > SQLITE_PAGE_SIZE ) goto page_format_error;
    freeSpace -= sz;
    pPage->apCell[pPage->nCell++] = pCell;
    idx = pCell->h.iNext;
  }
  pPage->nFree = 0;
  idx = ((PageHdr*)pPage)->firstFree;
  while( idx!=0 ){
    if( idx>SQLITE_PAGE_SIZE-sizeof(FreeBlk) ) goto page_format_error;
    if( idx<sizeof(PageHdr) ) goto page_format_error;
    pFBlk = (FreeBlk*)&pPage->aDisk[idx];
    pPage->nFree += pFBlk->iSize;
    if( pFBlk->iNext <= idx ) goto page_format_error;
    idx = pFBlk->iNext;
  }
  if( pPage->nFree!=freeSpace ) goto page_format_error;
  return SQLITE_OK;

page_format_error:
  return SQLITE_CORRUPT;
}

/*
** Recompute the MemPage.apCell[], MemPage.nCell, and MemPage.nFree parameters
** for a cell after the content has be changed significantly.
**
** The computation here is similar to initPage() except that in this case
** the MemPage.aDisk[] field has been set up internally (instead of 
** having been read from disk) so we do not need to do as much error
** checking.
*/
static void reinitPage(MemPage *pPage){
  Cell *pCell;

  pPage->nCell = 0;
  idx = ((PageHdr*)pPage)->firstCell;
  while( idx!=0 ){
    pCell = (Cell*)&pPage->aDisk[idx];
    sz = cellSize(pCell);
    pPage->apCell[pPage->nCell++] = pCell;
    idx = pCell->h.iNext;
  }
  pPage->nFree = 0;
  idx = ((PageHdr*)pPage)->firstFree;
  while( idx!=0 ){
    pFBlk = (FreeBlk*)&pPage->aDisk[idx];
    pPage->nFree += pFBlk->iSize;
    idx = pFBlk->iNext;
  }
  return SQLITE_OK;
}

/*
** Initialize a database page so that it holds no entries at all.
*/
static void zeroPage(MemPage *pPage){
  PageHdr *pHdr;
  FreeBlk *pFBlk;
  memset(pPage, 0, SQLITE_PAGE_SIZE);
  pHdr = (PageHdr*)pPage;
  pHdr->firstCell = 0;
  pHdr->firstFree = sizeof(*pHdr);
  pFBlk = (FreeBlk*)&pHdr[1];
  pFBlk->iNext = 0;
  pFBlk->iSize = SQLITE_PAGE_SIZE - sizeof(*pHdr);
}

/*
** This routine is called when the reference count for a page
** reaches zero.  We need to unref the pParent pointer when that
** happens.
*/
static void pageDestructor(void *pData){
︙︙
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529

** if there is a locking protocol violation.
*/
static int lockBtree(Btree *pBt){
  int rc;
  if( pBt->page1 ) return SQLITE_OK;
  rc = sqlitepager_get(pBt->pPager, 1, &pBt->page1);
  if( rc!=SQLITE_OK ) return rc;
  rc = initPage(pBt->page1, 1, 0);
  if( rc!=SQLITE_OK ) goto page1_init_failed;

  /* Do some checking to help insure the file we opened really is
  ** a valid database file. 
  */
  if( sqlitepager_pagecount(pBt->pPager)>0 ){
    Page1Header *pP1 = (Page1Header*)pBt->page1;
    if( pP1->magic1!=MAGIC_1 || pP1->magic2!=MAGIC_2 ){
      rc = SQLITE_CORRUPT;
      goto page1_init_failed;
    }
  }
  return rc;

page1_init_failed:








<
<





|
|








562
563
564
565
566
567
568


569
570
571
572
573
574
575
576
577
578
579
580
581
582

** if there is a locking protocol violation.
*/
static int lockBtree(Btree *pBt){
  int rc;
  if( pBt->page1 ) return SQLITE_OK;
  rc = sqlitepager_get(pBt->pPager, 1, &pBt->page1);
  if( rc!=SQLITE_OK ) return rc;



  /* Do some checking to help insure the file we opened really is
  ** a valid database file. 
  */
  if( sqlitepager_pagecount(pBt->pPager)>0 ){
    PageOne *pP1 = pBt->page1;
    if( strcmp(pP1->zMagic1,zMagicHeader)!=0 ){
      rc = SQLITE_CORRUPT;
      goto page1_init_failed;
    }
  }
  return rc;

page1_init_failed:
︙︙
603
604
605
606
607
608
609
610
611
612









613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630









631
632
633
634

635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676


677
678
679
680
681
682
683

    if( rc!=SQLITE_OK ){
      *ppCur = 0;
      return rc;
    }
  }
  pCur = sqliteMalloc( sizeof(*pCur) );
  if( pCur==0 ){
    *ppCur = 0;
    unlockBtree(pBt);
    return SQLITE_NOMEM;









  }
  pCur->pPrev = 0;
  pCur->pNext = pBt->pCursor;
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur;
  }
  pBt->pCursor = pCur;
  pCur->pBt = pBt;
  rc = sqlitepager_get(pBt->pPager, 1, &pCur->pPage);
  if( rc!=SQLITE_OK ){
    sqliteFree(pCur);
    *ppCur = 0;
    return rc;
  }
  initPage(pCur->pPage, 1, 0);
  pCur->idx = 0;
  *ppCur = pCur;
  return SQLITE_OK;









}

/*
** Close a cursor. 

*/
int sqliteBtreeCloseCursor(BtCursor *pCur){
  Btree *pBt = pCur->pBt;
  int i;
  if( pCur->pPrev ){
    pCur->pPrev->pNext = pCur->pNext;
  }else{
    pBt->pCursor = pCur->pNext;
  }
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur->pPrev;
  }
  sqlitepager_unref(pCur->pPage);
  if( pBt->pCursor==0 && pBt->inTrans==0 ){
    unlockBtree(pBt);
  }
  sqliteFree(pCur);
}

/*
** Make a temporary cursor by filling in the fields of pTempCur.
** The temporary cursor is not on the cursor list for the Btree.
*/
static void createTemporaryCursor(BtCursor *pCur, BtCursor *pTempCur){
  memcpy(pTempCur, pCur, sizeof(*pCur));
  pTempCur->pNext = 0;
  pTempCur->pPrev = 0;
  sqlitepager_ref(pTempCur->pPage);
}

/*
** Delete a temporary cursor such as was made by the createTemporaryCursor()
** function above.
*/
static void destroyTemporaryCursor(BeCursor *pCur){
  sqlitepager_unref(pCur->pPage);
}

/*
** Write the number of bytes of key for the entry the cursor is
** pointing to into *pSize.  Return SQLITE_OK.  Failure is not
** possible.


*/
int sqliteBtreeKeySize(BtCursor *pCur, int *pSize){
  Cell *pCell;
  MemPage *pPage;

  pPage = pCur->pPage;
  assert( pPage!=0 );








<
<
|
>
>
>
>
>
>
>
>
>








<
<
<
<
<
<
<



>
>
>
>
>
>
>
>
>



|
>













<
|
<







|







|


|




|
|
|
>
>








656
657
658
659
660
661
662


663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680







681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710

711

712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746

    if( rc!=SQLITE_OK ){
      *ppCur = 0;
      return rc;
    }
  }
  pCur = sqliteMalloc( sizeof(*pCur) );
  if( pCur==0 ){


    rc = SQLITE_NOMEM;
    goto create_cursor_exception;
  }
  rc = sqlitepager_get(pBt->pPager, 2, &pCur->pPage);
  if( rc!=SQLITE_OK ){
    goto create_cursor_exception;
  }
  rc = initPage(pCur->pPage, 2, 0);
  if( rc!=SQLITE_OK ){
    goto create_cursor_exception;
  }
  pCur->pPrev = 0;
  pCur->pNext = pBt->pCursor;
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur;
  }
  pBt->pCursor = pCur;
  pCur->pBt = pBt;







  pCur->idx = 0;
  *ppCur = pCur;
  return SQLITE_OK;

create_cursor_exception:
  *ppCur = 0;
  if( pCur ){
    if( pCur->pPage ) sqlitepager_unref(pCur->pPage);
    sqliteFree(pCur);
  }
  unlinkBtree(pBt);
  return rc;
}

/*
** Close a cursor.  The lock on the database file is released
** when the last cursor is closed.
*/
int sqliteBtreeCloseCursor(BtCursor *pCur){
  Btree *pBt = pCur->pBt;
  int i;
  if( pCur->pPrev ){
    pCur->pPrev->pNext = pCur->pNext;
  }else{
    pBt->pCursor = pCur->pNext;
  }
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur->pPrev;
  }
  sqlitepager_unref(pCur->pPage);

  unlockBtree(pBt);

  sqliteFree(pCur);
}

/*
** Make a temporary cursor by filling in the fields of pTempCur.
** The temporary cursor is not on the cursor list for the Btree.
*/
static void CreateTemporaryCursor(BtCursor *pCur, BtCursor *pTempCur){
  memcpy(pTempCur, pCur, sizeof(*pCur));
  pTempCur->pNext = 0;
  pTempCur->pPrev = 0;
  sqlitepager_ref(pTempCur->pPage);
}

/*
** Delete a temporary cursor such as was made by the CreateTemporaryCursor()
** function above.
*/
static void DestroyTemporaryCursor(BeCursor *pCur){
  sqlitepager_unref(pCur->pPage);
}

/*
** Set *pSize to the number of bytes of key in the entry the
** cursor currently points to.  Always return SQLITE_OK.
** Failure is not possible.  If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
int sqliteBtreeKeySize(BtCursor *pCur, int *pSize){
  Cell *pCell;
  MemPage *pPage;

  pPage = pCur->pPage;
  assert( pPage!=0 );
︙︙
712
713
714
715
716
717
718

719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740

741
742
743
744
745
746
747

    memcpy(zBuf, &aPayload[offset], a);
    if( a==amt ){
      return SQLITE_OK;
    }
    offset += a;
    zBuf += a;
    amt -= a;

    if( amt>0 ){
      assert( a==ROUNDUP(a) );
      nextPage = *(Pgno*)&aPayload[a];
    }
  }
  while( amt>0 && nextPage ){
    OverflowPage *pOvfl;
    rc = sqlitepager_get(pCur->pBt->pPager, nextPage, &pOvfl);
    if( rc!=0 ){
      return rc;
    }
    nextPage = pOvfl->next;
    if( offset<OVERFLOW_SIZE ){
      int a = amt;
      if( a + offset > OVERFLOW_SIZE ){
        a = OVERFLOW_SIZE - offset;
      }
      memcpy(zBuf, &pOvfl->aPayload[offset], a);
      offset += a;
      amt -= a;
      zBuf += a;
    }

    sqlitepager_unref(pOvfl);
  }
  return amt==0 ? SQLITE_OK : SQLITE_CORRUPT;
}

/*
** Read part of the key associated with cursor pCur.  A total








>
|
<
|
<














<



>








775
776
777
778
779
780
781
782
783

784

785
786
787
788
789
790
791
792
793
794
795
796
797
798

799
800
801
802
803
804
805
806
807
808
809

    memcpy(zBuf, &aPayload[offset], a);
    if( a==amt ){
      return SQLITE_OK;
    }
    offset += a;
    zBuf += a;
    amt -= a;
  }
  if( amt>0 ){

    nextPage = pCur->pPage->apCell[pCur->idx].ovfl;

  }
  while( amt>0 && nextPage ){
    OverflowPage *pOvfl;
    rc = sqlitepager_get(pCur->pBt->pPager, nextPage, &pOvfl);
    if( rc!=0 ){
      return rc;
    }
    nextPage = pOvfl->next;
    if( offset<OVERFLOW_SIZE ){
      int a = amt;
      if( a + offset > OVERFLOW_SIZE ){
        a = OVERFLOW_SIZE - offset;
      }
      memcpy(zBuf, &pOvfl->aPayload[offset], a);

      amt -= a;
      zBuf += a;
    }
    offset -= OVERFLOW_SIZE;
    sqlitepager_unref(pOvfl);
  }
  return amt==0 ? SQLITE_OK : SQLITE_CORRUPT;
}

/*
** Read part of the key associated with cursor pCur.  A total
︙︙
760
761
762
763
764
765
766


767
768
769
770
771
772
773


774
775
776
777
778
779
780

  pPage = pCur->pPage;
  assert( pPage!=0 );
  if( pCur->idx >= pPage->nCell ){
    return SQLITE_ERROR;
  }
  pCell = pPage->apCell[pCur->idx];
  if( amt+offset > pCell->h.nKey ){


  return getPayload(pCur, offset, amt, zBuf);
}

/*
** Write the number of bytes of data on the entry that the cursor
** is pointing to into *pSize.  Return SQLITE_OK.  Failure is
** not possible.


*/
int sqliteBtreeDataSize(BtCursor *pCur, int *pSize){
  Cell *pCell;
  MemPage *pPage;

  pPage = pCur->pPage;
  assert( pPage!=0 );








>
>




|
|
|
>
>








822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846

  pPage = pCur->pPage;
  assert( pPage!=0 );
  if( pCur->idx >= pPage->nCell ){
    return SQLITE_ERROR;
  }
  pCell = pPage->apCell[pCur->idx];
  if( amt+offset > pCell->h.nKey ){
    return SQLITE_ERROR;
  }
  return getPayload(pCur, offset, amt, zBuf);
}

/*
** Set *pSize to the number of bytes of data in the entry the
** cursor currently points to.  Always return SQLITE_OK.
** Failure is not possible.  If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
int sqliteBtreeDataSize(BtCursor *pCur, int *pSize){
  Cell *pCell;
  MemPage *pPage;

  pPage = pCur->pPage;
  assert( pPage!=0 );
︙︙
803
804
805
806
807
808
809
810


811
812
813
814
815
816
817

  if( amt==0 ) return SQLITE_OK;
  pPage = pCur->pPage;
  assert( pPage!=0 );
  if( pCur->idx >= pPage->nCell ){
    return SQLITE_ERROR;
  }
  pCell = pPage->apCell[pCur->idx];
  if( amt+offset > pCell->h.nKey ){


  return getPayload(pCur, offset + pCell->h.nKey, amt, zBuf);
}

/*
** Compare the key for the entry that pCur points to against the 
** given key (pKey,nKeyOrig).  Put the comparison result in *pResult.
** The result is negative if pCur<pKey, zero if they are equal and








|
>
>








869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885

  if( amt==0 ) return SQLITE_OK;
  pPage = pCur->pPage;
  assert( pPage!=0 );
  if( pCur->idx >= pPage->nCell ){
    return SQLITE_ERROR;
  }
  pCell = pPage->apCell[pCur->idx];
  if( amt+offset > pCell->h.nData ){
    return SQLITE_ERROR;
  }
  return getPayload(pCur, offset + pCell->h.nKey, amt, zBuf);
}

/*
** Compare the key for the entry that pCur points to against the 
** given key (pKey,nKeyOrig).  Put the comparison result in *pResult.
** The result is negative if pCur<pKey, zero if they are equal and
︙︙
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840

  Pgno nextPage;
  int nKey = nKeyOrig;
  int n;
  Cell *pCell;

  assert( pCur->pPage );
  assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
  pCell = &pCur->pPage->apCell[pCur->idx];
  if( nKey > pCell->h.nKey ){
    nKey = pCell->h.nKey;
  }
  n = nKey;
  if( n>MX_LOCAL_PAYLOAD ){
    n = MX_LOCAL_PAYLOAD;
  }








|








894
895
896
897
898
899
900
901
902
903
904
905
906
907
908

  Pgno nextPage;
  int nKey = nKeyOrig;
  int n;
  Cell *pCell;

  assert( pCur->pPage );
  assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
  pCell = pCur->pPage->apCell[pCur->idx];
  if( nKey > pCell->h.nKey ){
    nKey = pCell->h.nKey;
  }
  n = nKey;
  if( n>MX_LOCAL_PAYLOAD ){
    n = MX_LOCAL_PAYLOAD;
  }
︙︙
894
895
896
897
898
899
900
901
902
903
904
905
906
907

908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929

930
931

932
933
934
935
936
937
938


/*
** Move the cursor up to the parent page.
**
** pCur->idx is set to the cell index that contains the pointer
** to the page we are coming from.  If we are coming from the
** right-most child page then pCur->idx is set to one more than
** the largets cell index.
*/
static int moveToParent(BtCursor *pCur){
  Pgno oldPgno;
  MemPage *pParent;

  pParent = pCur->pPage->pParent;

  oldPgno = sqlitepager_pagenumber(pCur->pPage);
  if( pParent==0 ){
    return SQLITE_INTERNAL;
  }
  sqlitepager_ref(pParent);
  sqlitepager_unref(pCur->pPage);
  pCur->pPage = pParent;
  pCur->idx = pPage->nCell;
  for(i=0; i<pPage->nCell; i++){
    if( pPage->apCell[i].h.leftChild==oldPgno ){
      pCur->idx = i;
      break;
    }
  }
  return SQLITE_OK;
}

/*
** Move the cursor to the root page
*/
static int moveToRoot(BtCursor *pCur){
  MemPage *pNew;

  pNew = pCur->pBt->page1;
  sqlitepager_ref(pNew);

  sqlitepager_unref(pCur->pPage);
  pCur->pPage = pNew;
  pCur->idx = 0;
  return SQLITE_OK;
}

/*








|






>

<
<
<


















>
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|
>








962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977



978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006


/*
** Move the cursor up to the parent page.
**
** pCur->idx is set to the cell index that contains the pointer
** to the page we are coming from.  If we are coming from the
** right-most child page then pCur->idx is set to one more than
** the largest cell index.
*/
static int moveToParent(BtCursor *pCur){
  Pgno oldPgno;
  MemPage *pParent;

  pParent = pCur->pPage->pParent;
  if( pParent==0 ) return SQLITE_INTERNAL;
  oldPgno = sqlitepager_pagenumber(pCur->pPage);



  sqlitepager_ref(pParent);
  sqlitepager_unref(pCur->pPage);
  pCur->pPage = pParent;
  pCur->idx = pPage->nCell;
  for(i=0; i<pPage->nCell; i++){
    if( pPage->apCell[i].h.leftChild==oldPgno ){
      pCur->idx = i;
      break;
    }
  }
  return SQLITE_OK;
}

/*
** Move the cursor to the root page
*/
static int moveToRoot(BtCursor *pCur){
  MemPage *pNew;
  int rc;

  rc = sqlitepager_get(pCur->pBt->pPager, 2, &pNew);
  if( rc ) return rc;
  sqlitepager_unref(pCur->pPage);
  pCur->pPage = pNew;
  pCur->idx = 0;
  return SQLITE_OK;
}

/*
︙︙
951
952
953
954
955
956
957
958
959
960
961
962
963



964
965

966
967


968
969
970
971
972
973
974
975

}


/* Move the cursor so that it points to an entry near pKey.
** Return a success code.
**
** If an exact match is not found, then the cursor is always
** left point at a root page which would hold the entry if it
** were present.  The cursor might point to an entry that comes
** before or after the key.
**
** If pRes!=NULL, then *pRes is written with an integer code to
** describe the results.  *pRes is set to 0 if the cursor is left 



** pointing at an entry that exactly matches pKey.  *pRes is made
** negative if the cursor is on the largest entry less than pKey.

** *pRes is set positive if the cursor is on the smallest entry
** greater than pKey.  *pRes is not changed if the return value


** is something other than SQLITE_OK;
*/
int sqliteBtreeMoveto(BtCursor *pCur, void *pKey, int nKey, int *pRes){
  int rc;
  rc = moveToRoot(pCur);
  if( rc ) return rc;
  for(;;){
    int lwr, upr;








|



|
|
>
>
>
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>
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>
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|








1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049

}


/* Move the cursor so that it points to an entry near pKey.
** Return a success code.
**
** If an exact match is not found, then the cursor is always
** left pointing at a leaf page which would hold the entry if it
** were present.  The cursor might point to an entry that comes
** before or after the key.
**
** The result of comparing the key with the entry to which the
** cursor is left pointing is stored in pCur->iMatch.  The same
** value is also written to *pRes if pRes!=NULL.  The meaning of
** this value is as follows:
**
**     *pRes<0      The cursor is left pointing at an entry that
**                  is larger than pKey.
**
**     *pRes==0     The cursor is left pointing at an entry that
**                  exactly matches pKey.
**
**     *pRes>0      The cursor is left pointing at an entry that
**                  is smaller than pKey.
*/
int sqliteBtreeMoveto(BtCursor *pCur, void *pKey, int nKey, int *pRes){
  int rc;
  rc = moveToRoot(pCur);
  if( rc ) return rc;
  for(;;){
    int lwr, upr;
︙︙
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009

1010
1011
1012
1013
1014
1015

1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034

        lwr = pCur->idx+1;
      }else{
        upr = pCur->idx-1;
      }
    }
    assert( lwr==upr+1 );
    if( lwr>=pPage->nCell ){
      chldPg = pPage->pHdr->rightChild;
    }else{
      chldPg = pPage->apCell[lwr]->h.leftChild;
    }
    if( chldPg==0 ){
      pCur->iMatch = c;
      if( pRes ) *pRes = c;
      return SQLITE_OK;
    }
    rc = moveToChild(pCur, chldPg);
    if( rc ) return rc;
  }

}

/*
** Advance the cursor to the next entry in the database.  If pRes!=NULL
** then set *pRes=0 on success and set *pRes=1 if the cursor was
** pointing to the last entry in the database.

*/
int sqliteBtreeNext(BtCursor *pCur, int *pRes){
  int rc;
  if( pCur->bSkipNext ){
    pCur->bSkipNext = 0;
    if( pRes ) *pRes = 0;
    return SQLITE_OK;
  }
  pCur->idx++;
  if( pCur->idx>=pCur->pPage->nCell ){
    if( pPage->pHdr->rightChild ){
      rc = moveToChild(pCur, pPage->pHdr->rightChild);
      if( rc ) return rc;
      rc = moveToLeftmost(pCur);
      if( rc ) return rc;
      if( pRes ) *pRes = 0;
      return SQLITE_OK;
    }
    do{








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>



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|








1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110

        lwr = pCur->idx+1;
      }else{
        upr = pCur->idx-1;
      }
    }
    assert( lwr==upr+1 );
    if( lwr>=pPage->nCell ){
      chldPg = ((PageHdr*)pPage)->rightChild;
    }else{
      chldPg = pPage->apCell[lwr]->h.leftChild;
    }
    if( chldPg==0 ){
      pCur->iMatch = c;
      if( pRes ) *pRes = c;
      return SQLITE_OK;
    }
    rc = moveToChild(pCur, chldPg);
    if( rc ) return rc;
  }
  /* NOT REACHED */
}

/*
** Advance the cursor to the next entry in the database.  If
** successful and pRes!=NULL then set *pRes=0.  If the cursor
** was already pointing to the last entry in the database before
** this routine was called, then set *pRes=1 if pRes!=NULL.
*/
int sqliteBtreeNext(BtCursor *pCur, int *pRes){
  int rc;
  if( pCur->bSkipNext ){
    pCur->bSkipNext = 0;
    if( pRes ) *pRes = 0;
    return SQLITE_OK;
  }
  pCur->idx++;
  if( pCur->idx>=pCur->pPage->nCell ){
    if( ((PageHdr*)pPage)->rightChild ){
      rc = moveToChild(pCur, ((PageHdr*)pPage)->rightChild);
      if( rc ) return rc;
      rc = moveToLeftmost(pCur);
      if( rc ) return rc;
      if( pRes ) *pRes = 0;
      return SQLITE_OK;
    }
    do{
︙︙
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071

** sqlitepager_unref() on the new page when it is done.
**
** SQLITE_OK is returned on success.  Any other return value indicates
** an error.  *ppPage and *pPgno are undefined in the event of an error.
** Do not invoke sqlitepager_unref() on *ppPage if an error is returned.
*/
static int allocatePage(Btree *pBt, MemPage **ppPage, Pgno *pPgno){
  Page1Header *pPage1 = (Page1Header*)pBt->page1;
  if( pPage1->freeList ){
    OverflowPage *pOvfl;
    rc = sqlitepager_write(pPage1);
    if( rc ) return rc;
    *pPgno = pPage1->freeList;
    rc = sqlitepager_get(pBt->pPager, pPage1->freeList, &pOvfl);
    if( rc ) return rc;








|








1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147

** sqlitepager_unref() on the new page when it is done.
**
** SQLITE_OK is returned on success.  Any other return value indicates
** an error.  *ppPage and *pPgno are undefined in the event of an error.
** Do not invoke sqlitepager_unref() on *ppPage if an error is returned.
*/
static int allocatePage(Btree *pBt, MemPage **ppPage, Pgno *pPgno){
  PageOne *pPage1 = pBt->page1;
  if( pPage1->freeList ){
    OverflowPage *pOvfl;
    rc = sqlitepager_write(pPage1);
    if( rc ) return rc;
    *pPgno = pPage1->freeList;
    rc = sqlitepager_get(pBt->pPager, pPage1->freeList, &pOvfl);
    if( rc ) return rc;
︙︙
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103

** Add a page of the database file to the freelist.  Either pgno or
** pPage but not both may be 0. 
**
** sqlitepager_unref() is NOT called for pPage.  The calling routine
** needs to do that.
*/
static int freePage(Btree *pBt, void *pPage, Pgno pgno){
  Page1Header *pPage1 = (Page1Header*)pBt->page1;
  OverflowPage *pOvfl = (OverflowPage*)pPage;
  int rc;
  int needOvflUnref = 0;
  if( pgno==0 ){
    assert( pOvfl!=0 );
    pgno = sqlitepager_pagenumber(pOvfl);
  }








|








1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179

** Add a page of the database file to the freelist.  Either pgno or
** pPage but not both may be 0. 
**
** sqlitepager_unref() is NOT called for pPage.  The calling routine
** needs to do that.
*/
static int freePage(Btree *pBt, void *pPage, Pgno pgno){
  PageOne *pPage1 = pBt->page1;
  OverflowPage *pOvfl = (OverflowPage*)pPage;
  int rc;
  int needOvflUnref = 0;
  if( pgno==0 ){
    assert( pOvfl!=0 );
    pgno = sqlitepager_pagenumber(pOvfl);
  }
︙︙
1115
1116
1117
1118
1119
1120
1121


1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146

1147
1148
1149
1150
1151
1152
1153

  if( rc ){
    if( needOvflUnref ) sqlitepager_unref(pOvfl);
    return rc;
  }
  pOvfl->next = pPage1->freeList;
  pPage1->freeList = pgno;
  memset(pOvfl->aPayload, 0, OVERFLOW_SIZE);


  rc = sqlitepager_unref(pOvfl);
  return rc;
}

/*
** Erase all the data out of a cell.  This involves returning overflow
** pages back the freelist.
*/
static int clearCell(Btree *pBt, Cell *pCell){
  Pager *pPager = pBt->pPager;
  OverflowPage *pOvfl;
  Page1Header *pPage1 = (Page1Header*)pBt->page1;
  Pgno ovfl, nextOvfl;
  int rc;

  if( pCell->h.nKey + pCell->h.nData <= MX_LOCAL_PAYLOAD ){
    return SQLITE_OK;
  }
  ovfl = pCell->ovfl;
  pCell->ovfl = 0;
  while( ovfl ){
    rc = sqlitepager_get(pPager, ovfl, &pOvfl);
    if( rc ) return rc;
    nextOvfl = pOvfl->next;
    freePage(pBt, pOvfl, ovfl);

    ovfl = nextOvfl;
    sqlitepager_unref(pOvfl);
  }
  return SQLITE_OK;
}

/*








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<












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>








1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210

1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231

  if( rc ){
    if( needOvflUnref ) sqlitepager_unref(pOvfl);
    return rc;
  }
  pOvfl->next = pPage1->freeList;
  pPage1->freeList = pgno;
  memset(pOvfl->aPayload, 0, OVERFLOW_SIZE);
  pPage->isInit = 0;
  assert( pPage->pParent==0 );
  rc = sqlitepager_unref(pOvfl);
  return rc;
}

/*
** Erase all the data out of a cell.  This involves returning overflow
** pages back the freelist.
*/
static int clearCell(Btree *pBt, Cell *pCell){
  Pager *pPager = pBt->pPager;
  OverflowPage *pOvfl;

  Pgno ovfl, nextOvfl;
  int rc;

  if( pCell->h.nKey + pCell->h.nData <= MX_LOCAL_PAYLOAD ){
    return SQLITE_OK;
  }
  ovfl = pCell->ovfl;
  pCell->ovfl = 0;
  while( ovfl ){
    rc = sqlitepager_get(pPager, ovfl, &pOvfl);
    if( rc ) return rc;
    nextOvfl = pOvfl->next;
    rc = freePage(pBt, pOvfl, ovfl);
    if( rc ) return rc;
    ovfl = nextOvfl;
    sqlitepager_unref(pOvfl);
  }
  return SQLITE_OK;
}

/*
︙︙
1203
1204
1205
1206
1207
1208
1209

































1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232

      pPayload += n;
    }
    spaceLeft -= n;
    pSpace += n;
  }
  return SQLITE_OK;
}


































/*
** Attempt to move N or more bytes out of the page that the cursor
** points to into the left sibling page.  (The left sibling page
** contains cells that are less than the cells on this page.)  The
** entry that the cursor is pointing to cannot be moved.  Return
** TRUE if successful and FALSE if not.
**
** Reasons for not being successful include: 
**
**    (1) there is no left sibling,
**    (2) we could only move N-1 bytes or less,
**    (3) some kind of file I/O error occurred
**
** Note that a partial rotation may have occurred even if this routine
** returns FALSE.  Failure means we could not rotation a fill N bytes.
** If it is possible to rotation some smaller number M, then the 
** rotation occurs but we still return false.
**
** Example:  Consider a segment of the Btree that looks like the
** figure below prior to rotation.  The cursor is pointing to the
** entry *.  The sort order of the entries is A B C D E * F Y.
**








>
>
>
>
>
>
>
>
>
>
>
>
>
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>
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1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343

      pPayload += n;
    }
    spaceLeft -= n;
    pSpace += n;
  }
  return SQLITE_OK;
}

/*
** Change the MemPage.pParent pointer on the page whose number is
** given in the second argument sot that MemPage.pParent holds the
** pointer in the third argument.
*/
static void reparentPage(Pager *pPager, Pgno pgno, MemPage *pNewParent){
  MemPage *pThis;

  assert( pPager!=0 && pgno!=0 );
  pThis = sqlitepager_lookup(pPager, pgno);
  if( pThis && pThis->pParent!=pNewParent ){
    if( pThis->pParent ) sqlitepager_unref(pThis->pParent);
    pThis->pParent = pNewParent;
    if( pNewParent ) sqlitepager_ref(pNewParent);
  }
}

/*
** Reparent all children of the given page to be the given page.
** In other words, for every child of pPage, invoke reparentPage()
** to make sure that child knows that pPage is its parent.
**
** This routine gets called after you memcpy() one page into
** another.
*/
static void reparentChildPages(Pager *pPager, Page *pPage){
  int i;
  for(i=0; i<pPage->nCell; i++){
    reparentPage(pPager, pPage->apCell[i]->leftChild, pPage);
  }
  reparentPage(pPager, ((PageHdr*)pPage)->rightChild, pPage);
}

/*
** Attempt to move N or more bytes out of the page that the cursor
** points to into the left sibling page.  (The left sibling page
** contains cells that are less than the cells on this page.)  The
** entry that the cursor is pointing to cannot be moved.  Return
** TRUE if successful and FALSE if not.
**
** Reasons for not being successful include: 
**
**    (1) there is no left sibling,
**    (2) we could only move N-1 bytes or less,
**    (3) some kind of file I/O error occurred
**
** Note that a partial rotation may have occurred even if this routine
** returns FALSE.  Failure means we could not rotation a full N bytes.
** If it is possible to rotation some smaller number M, then the 
** rotation occurs but we still return false.
**
** Example:  Consider a segment of the Btree that looks like the
** figure below prior to rotation.  The cursor is pointing to the
** entry *.  The sort order of the entries is A B C D E * F Y.
**
︙︙
1262
1263
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1268






























1269
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1271
1272
1273
1274
1275

** This routine is the same as rotateLeft() except that it move data
** to the right instead of to the left.  See comments on the rotateLeft()
** routine for additional information.
*/
static int rotateRight(BtCursor *pCur, int N){
  return 0;
}































/*
** Split a single database page into two roughly equal-sized pages.
**
** The input is an existing page and a new Cell.  The Cell might contain
** a valid Cell.h.leftChild field pointing to a child page.
**








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1373
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1416

** This routine is the same as rotateLeft() except that it move data
** to the right instead of to the left.  See comments on the rotateLeft()
** routine for additional information.
*/
static int rotateRight(BtCursor *pCur, int N){
  return 0;
}

/*
** Append a cell onto the end of a page.
**
** The child page of the cell is reparented if pPager!=NULL.
*/
static void appendCell(
  Pager *pPager,      /* The page cache.  Needed for reparenting */
  Cell *pSrc,         /* The Cell to be copied onto a new page */
  MemPage *pPage      /* The page into which the cell is copied */
){
  int pc;
  int sz;
  Cell *pDest;

  sz = cellSize(pSrc);
  pc = allocateSpace(pPage, sz);
  assert( pc>0 ){
  pDest = pPage->apCell[pPage->nCell] = &pPage->aDisk[pc];
  memcpy(pDest, pSrc, sz);
  pDest->h.iNext = 0;
  if( pPage->nCell>0 ){
    pPage->apCell[pPage->nCell-1]->h.iNext = pc;
  }else{
    ((PageHdr*)pPage)->firstCell = pc;
  }
  if( pPager && pDest->h.leftChild ){
    reparentPage(pPager, pDest->h.leftChild, pPage);
  }
}

/*
** Split a single database page into two roughly equal-sized pages.
**
** The input is an existing page and a new Cell.  The Cell might contain
** a valid Cell.h.leftChild field pointing to a child page.
**
︙︙
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1312

1313
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*/
static int split(
  BtCursor *pCur,     /* A cursor pointing at a cell on the page to be split */
  Cell *pNewCell,     /* A new cell to add to pIn before dividing it up */
  Cell *pCenter,      /* Write the cell that divides the two pages here */
  MemPage **ppOut     /* If not NULL, put larger cells in new page at *ppOut */
){






  




























































}

/*
** Unlink a cell from a database page.  Add the space used by the cell
** back to the freelist for the database page on which the cell used to
** reside.
**
** This operation overwrites the cell header and content.
*/
static void unlinkCell(BtCursor *pCur){
  MemPage *pPage;    /* Page containing cell to be unlinked */
  int idx;           /* The index of the cell to be unlinked */
  Cell *pCell;       /* Pointer to the cell to be unlinked */
  u16 *piCell;       /* iNext pointer from prior cell */
  int iCell;         /* Index in pPage->aDisk[] of cell to be unlinked */
  int i;             /* Loop counter */

  pPage = pCur->pPage;

  idx = pCur->idx;
  pCell = pPage->apCell[idx];
  if( idx==0 ){
    piCell = &pPage->pHdr->firstCell;
  }else{
    piCell = &pPage->apCell[idx-1]->h.iNext;
  }








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*/
static int split(
  BtCursor *pCur,     /* A cursor pointing at a cell on the page to be split */
  Cell *pNewCell,     /* A new cell to add to pIn before dividing it up */
  Cell *pCenter,      /* Write the cell that divides the two pages here */
  MemPage **ppOut     /* If not NULL, put larger cells in new page at *ppOut */
){
  MemPage *pLeft, *pRight;
  Pgno pgnoLeft, pgnoRight;
  PageHdr *pHdr;
  int rc;
  Pager *pPager = pCur->pBt->pPager;
  MemPage tempPage;

  /* Allocate pages to hold cells after the split and make pRight and 
  ** pLeft point to the newly allocated pages.
  */
  rc = allocatePage(pCur->pBt, &pLeft, &pgnoLeft);
  if( rc ) return rc;
  if( ppOut ){
    rc = allocatePage(pCur->pBt, &pRight, &pgnoRight);
    if( rc ){
      freePage(pCur->pBt, pLeft, pgnoLeft);
      return rc;
    }
    *ppOut = pRight;
  }else{
    *ppOut = tempPage;
  }

  /* Copy the smaller cells from the original page into the left page
  ** of the split.
  */
  zeroPage(pLeft);
  if( pCur->idx==0 && pCur->match>0 ){
    appendCell(pPager, pNewCell, pLeft);
  }
  do{
    assert( i<pPage->nCell );
    appendCell(pPager, pPage->apCell[i++], pLeft);
    if( pCur->idx==i && pCur->iMatch>0 ){
      appendCell(pPager, pNewCell, Left);
    }
  }while( pc < SQLITE_PAGE_SIZE/2 );

  /* Copy the middle entry into *pCenter
  */
  assert( i<pPage->nCell );
  memcpy(pCenter, pPage->aCell[i], cellSize(pPage->aCell[i]));
  i++;
  pHdr = (PageHdr*)pLeft;
  pHdr->rightChild = pCenter->h.leftChild;
  if( pHdr->rightChild ){
    reparentPage(pPager, pHdr->rightChild, pLeft);
  }
  pCenter->h.leftChild = pgnoLeft;
 
  /* Copy the larger cells from the original page into the right
  ** page of the split
  */
  zeroPage(pRight);
  while( i<pPage->nCell ){
    appendCell(0, pPage->apCell[i++], pRight);
  }

  /* If ppOut==NULL then copy the temporary right page over top of
  ** the original input page.
  */
  if( ppOut==0 ){
    pRight->pParent = pPage->pParent;
    pRight->isInit = 1;
    memcpy(pPage, pRight, sizeof(*pPage));
  }
  reparentChildPages(pPager, pPage);
}

/*
** Unlink a cell from a database page.  Add the space used by the cell
** back to the freelist for the database page on which the cell used to
** reside.
**
** This operation overwrites the cell header and content.
*/
static void unlinkCell(BtCursor *pCur){
  MemPage *pPage;    /* Page containing cell to be unlinked */
  int idx;           /* The index of the cell to be unlinked */
  Cell *pCell;       /* Pointer to the cell to be unlinked */
  u16 *piCell;       /* iNext pointer from prior cell */
  int iCell;         /* Index in pPage->aDisk[] of cell to be unlinked */
  int i;             /* Loop counter */

  pPage = pCur->pPage;
  sqlitepager_write(pPage);
  idx = pCur->idx;
  pCell = pPage->apCell[idx];
  if( idx==0 ){
    piCell = &pPage->pHdr->firstCell;
  }else{
    piCell = &pPage->apCell[idx-1]->h.iNext;
  }
︙︙
1329
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1341
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1343

/*
** Add a Cell to a database page at the spot indicated by the cursor.
**
** With this routine, we know that the Cell pNewCell will fit into the
** database page that pCur points to.  The calling routine has made
** sure it will fit.  All this routine needs to do is add the Cell
** to the page.  The addToPage() routine should be used for cases
** were it is not know if the new cell will fit.
**
** The new cell is added to the page either before or after the cell
** to which the cursor is pointing.  The new cell is added before
** the cursor cell if pCur->iMatch>0 and the new cell is added after
** the cursor cell if pCur->iMatch<0.  pCur->iMatch should have been set
** by a prior call to sqliteBtreeMoveto() where the key was the key
** of the cell being inserted.  If sqliteBtreeMoveto() ended up on a








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1537
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1551

/*
** Add a Cell to a database page at the spot indicated by the cursor.
**
** With this routine, we know that the Cell pNewCell will fit into the
** database page that pCur points to.  The calling routine has made
** sure it will fit.  All this routine needs to do is add the Cell
** to the page.  The addToPage() routine should be used for cases
** were it is not known if the new cell will fit.
**
** The new cell is added to the page either before or after the cell
** to which the cursor is pointing.  The new cell is added before
** the cursor cell if pCur->iMatch>0 and the new cell is added after
** the cursor cell if pCur->iMatch<0.  pCur->iMatch should have been set
** by a prior call to sqliteBtreeMoveto() where the key was the key
** of the cell being inserted.  If sqliteBtreeMoveto() ended up on a
︙︙
1403
1404
1405
1406
1407
1408
1409


1410
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1428
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1432

*/
static int addToPage(BtCursor *pCur, Cell *pNewCell){
  Cell tempCell;
  Cell centerCell;

  for(;;){
    MemPage *pPage = pCur->pPage;


    int sz = cellSize(pNewCell);
    if( sz<=pPage->nFree ){
      insertCell(pCur, pNewCell);
      return SQLITE_OK;
    }
    if( pPage->pParent==0 ){
      MemPage *pRight;
      PageHdr *pHdr;
      FreeBlk *pFBlk;
      int pc;
      rc = split(pCur, pNewCell, &centerCell, &pRight);
      if( rc ) return rc;
      pHdr = pPage->pHdr;
      pHdr->right = sqlitepager_pagenumber(pRight);
      sqlitepager_unref(pRight);
      pHdr->firstCell = pc = pPage->idxStart + sizeof(*pHdr);
      sz = cellSize(&centerCell);
      memcpy(&pPage->aDisk[pc], &centerCell, sz);
      pc += sz;
      pHdr->firstFree = pc;
      pFBlk = (FreeBlk*)&pPage->aDisk[pc];
      pFBlk->iSize = SQLITE_PAGE_SIZE - pc;
      pFBlk->iNext = 0;








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1611
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*/
static int addToPage(BtCursor *pCur, Cell *pNewCell){
  Cell tempCell;
  Cell centerCell;

  for(;;){
    MemPage *pPage = pCur->pPage;
    rc = sqlitepager_write(pPage);
    if( rc ) return rc;
    int sz = cellSize(pNewCell);
    if( sz<=pPage->nFree ){
      insertCell(pCur, pNewCell);
      return SQLITE_OK;
    }
    if( pPage->pParent==0 ){
      MemPage *pRight;
      PageHdr *pHdr;
      FreeBlk *pFBlk;
      int pc;
      rc = split(pCur, pNewCell, &centerCell, &pRight);
      if( rc ) return rc;
      pHdr = pPage->pHdr;
      pHdr->right = sqlitepager_pagenumber(pRight);
      sqlitepager_unref(pRight);
      pHdr->firstCell = pc = sizeof(*pHdr);
      sz = cellSize(&centerCell);
      memcpy(&pPage->aDisk[pc], &centerCell, sz);
      pc += sz;
      pHdr->firstFree = pc;
      pFBlk = (FreeBlk*)&pPage->aDisk[pc];
      pFBlk->iSize = SQLITE_PAGE_SIZE - pc;
      pFBlk->iNext = 0;
︙︙
1461
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1486






1487
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1489




1490






1491

1492
1493

1494








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1537





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  Cell newCell;
  int rc;
  int loc;
  MemPage *pPage;
  Btree *pBt = pCur->pBt;

  rc = sqliteBtreeMoveTo(pCur, pKey, nKey, &loc);


  if( rc ) return rc;
  rc = fillInCell(pBt, &newCell, pKey, nKey, pData, nData);
  if( rc ) return rc;
  if( loc==0 ){
    newCell.h.leftChild = pCur->pPage->apCell[pCur->idx]->h.leftChild;
    rc = clearCell(pBt, pCur->pPage->apCell[pCur->idx]);
    if( rc ) return rc;
    unlinkCell(pCur);
  }
  return addToPage(pCur, &newCell);
}

/*
** Check the page given as the argument to see if it is less than
** half full.  If it is less than half full, then try to increase
** its fill factor by grabbing cells from siblings or by merging
** the page with siblings.
*/
static int refillPage(Btree *pBt, MemPage *pPage){






  if( pPage->nFree < SQLITE_PAGE_SIZE/2 ){
    return SQLITE_OK;
  }




  if( pPage->nCell==0 ){






    assert( pPage->pParent==0 );

    if( pPage->pHdr->rightChild ){
      

    }








    return SQLITE_OK;
  }

  /** merge with siblings **/

  /** borrow from siblings **/
}

/*
** Replace the content of the cell that pCur is pointing to with the content
** in pNewContent.  The pCur cell is not unlinked or moved in the Btree,
** its content is just replaced.
**
** If the size of pNewContent is greater than the current size of the
** cursor cell then the page that cursor points to might have to split.
*/
static int replaceContent(BtCursor *pCur, Cell *pNewContent){
  Cell *pCell;       /* The cell whose content will be changed */
  Pgno pgno;         /* Temporary storage for a page number */

  pCell = pCur->pPage->apCell[pCur->idx];
  rc = clearCell(pCur->pBt, pCell);
  if( rc ) return rc;
  pgno = pNewCell->h.leftChild;
  pNewCell->h.leftChild = pCell->h.leftChild;
  unlinkCell(pCur);
  rc = addToPage(pCur, pNewCell);
  pNewCell->h.leftChild = pgno;
  return rc;
}

/*
** Delete the record that the cursor is pointing to.
**
** The cursor is left point at either the next or the previous
** entry.  If left pointing to the next entry, then the pCur->bSkipNext
** flag is set which forces the next call to sqliteBtreeNext() to be
** a no-op.  That way, you can always call sqliteBtreeNext() after
** a delete and the cursor will be left pointing to the first entry
** after the deleted entry.
*/
int sqliteBtreeDelete(BtCursor *pCur){
  MemPage *pPage = pCur->pPage;
  Cell *pCell;
  int rc;





  pCell = pPage->apCell[pCur->idx];
  if( pPage->pHdr->rightChild ){
    /* The entry to be deleted is not on a leaf page.  Non-leaf entries 
    ** cannot be deleted directly because they have to be present to
    ** hold pointers to subpages.  So what we do is look at the next 
    ** entry in sequence.  The next entry is guaranteed to exist and 
    ** be a leaf.  We copy the payload from the next entry into this
    ** entry, then delete the next entry.
    */
    BtCursor origCur;
    createTemporaryCursor(pCur, &origCur);
    rc = sqliteBtreeNext(pCur, 0);
    if( rc==SQLITE_OK ){
      pPage = pCur->pPage;
      pCell = pPage->apCell[pCur->idx];
      rc = replaceContent(&origCur, pCell);
    }
    destroyTemporaryCursor(&origCur);
    if( rc ) return rc;
  }
  rc = clearCell(pCell);
  if( rc ) return rc;
  unlinkCell(pCur->pBt, pCell);
  if( pCur->idx == 0 ){
    pCur->bSkipNext = 1;
  }else{
    pCur->idx--;
  }
  rc = refillPage(pCur->pBt, pPage);
  return rc;
}








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1813

  Cell newCell;
  int rc;
  int loc;
  MemPage *pPage;
  Btree *pBt = pCur->pBt;

  rc = sqliteBtreeMoveTo(pCur, pKey, nKey, &loc);
  if( rc ) return rc;
  rc = sqlitepager_write(pCur->pPage);
  if( rc ) return rc;
  rc = fillInCell(pBt, &newCell, pKey, nKey, pData, nData);
  if( rc ) return rc;
  if( loc==0 ){
    newCell.h.leftChild = pCur->pPage->apCell[pCur->idx]->h.leftChild;
    rc = clearCell(pBt, pCur->pPage->apCell[pCur->idx]);
    if( rc ) return rc;
    unlinkCell(pCur);
  }
  return addToPage(pCur, &newCell);
}

/*
** Check the page at which the cursor points to see if it is less than
** half full.  If it is less than half full, then try to increase
** its fill factor by grabbing cells from siblings or by merging
** the page with siblings.
*/
static int refillPage(BtCursor *pCur){
  MemPage *pPage;
  BtCursor tempCur;
  int rc;
  Pager *pPager;

  pPage = pCur->pPage;
  if( pPage->nFree < SQLITE_PAGE_SIZE/2 ){
    return SQLITE_OK;
  }
  rc = sqlitepager_write(pPage);
  if( rc ) return rc;
  pPager = pCur->pBt->pPager;

  if( pPage->nCell==0 ){
    /* The page being refilled is the root of the BTree and it has
    ** no entries of its own.  If there is a child page, then make the
    ** child become the new root.
    */
    MemPage *pChild;
    Pgno pgnoChild;
    assert( pPage->pParent==0 );
    assert( sqlitepager_pagenumber(pPage)==2 );
    pgnoChild = ((PageHdr*)pPage)->rightChild;
    if( pgnoChild==0 ){
      return SQLITE_OK;
    }
    rc = sqlitepager_get(pPager, pgno, &pChild);
    if( rc ) return rc;
    memcpy(pPage, pChild, SQLITE_PAGE_SIZE);
    memset(&pPage->aDisk[SQLITE_PAGE_SIZE], 0, EXTRA_SIZE);
    freePage(pCur->pBt, pChild, pgnoChild);
    sqlitepager_unref(pChild);
    rc = initPage(pPage, 2, 0);
    reparentChildPages(pPager, pPage);
    return SQLITE_OK;
  }

  /** merge with siblings **/

  /** borrow from siblings **/
}

/*
** Replace the content of the cell that pCur is pointing to with the content
** in pNewContent.  The pCur cell is not unlinked or moved in the Btree,
** its content is just replaced.
**
** If the size of pNewContent is greater than the current size of the
** cursor cell then the page that cursor points to might have to split.
*/
static int ReplaceContentOfCell(BtCursor *pCur, Cell *pNewContent){
  Cell *pCell;       /* The cell whose content will be changed */
  Pgno pgno;         /* Temporary storage for a page number */

  pCell = pCur->pPage->apCell[pCur->idx];
  rc = clearCell(pCur->pBt, pCell);
  if( rc ) return rc;
  pgno = pNewCell->h.leftChild;
  pNewCell->h.leftChild = pCell->h.leftChild;
  unlinkCell(pCur);
  rc = addToPage(pCur, pNewCell);
  pNewCell->h.leftChild = pgno;
  return rc;
}

/*
** Delete the entry that the cursor is pointing to.
**
** The cursor is left pointing at either the next or the previous
** entry.  If the cursor is left pointing to the next entry, then 
** the pCur->bSkipNext flag is set which forces the next call to 
** sqliteBtreeNext() to be a no-op.  That way, you can always call
** sqliteBtreeNext() after a delete and the cursor will be left
** pointing to the first entry after the deleted entry.
*/
int sqliteBtreeDelete(BtCursor *pCur){
  MemPage *pPage = pCur->pPage;
  Cell *pCell;
  int rc;
  if( pCur->idx >= pPage->nCell ){
    return SQLITE_ERROR;  /* The cursor is not pointing to anything */
  }
  rc = sqlitepager_write(pPage);
  if( rc ) return rc;
  pCell = pPage->apCell[pCur->idx];
  if( pPage->pHdr->rightChild ){
    /* The entry to be deleted is not on a leaf page.  Non-leaf entries 
    ** cannot be deleted directly because they have to be present to
    ** hold pointers to subpages.  So what we do is look at the next 
    ** entry in sequence.  The next entry is guaranteed to exist and 
    ** be a leaf.  We copy the payload from the next entry into this
    ** entry, then delete the next entry.
    */
    BtCursor origCur;
    CreateTemporaryCursor(pCur, &origCur);
    rc = sqliteBtreeNext(pCur, 0);
    if( rc==SQLITE_OK ){
      pPage = pCur->pPage;
      pCell = pPage->apCell[pCur->idx];
      rc = ReplaceContentOfCell(&origCur, pCell);
    }
    DestroyTemporaryCursor(&origCur);
    if( rc ) return rc;
  }
  rc = clearCell(pCell);
  if( rc ) return rc;
  unlinkCell(pCur->pBt, pCell);
  if( pCur->idx == 0 ){
    pCur->bSkipNext = 1;
  }else{
    pCur->idx--;
  }
  rc = refillPage(pCur);
  return rc;
}
Changes to src/btree.h.
︙︙
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**   drh@hwaci.com
**   http://www.hwaci.com/drh/
**
*************************************************************************
** This header file defines the interface that the sqlite B-Tree file
** subsystem.
**
** @(#) $Id: btree.h,v 1.2 2001/05/24 21:06:36 drh Exp $
*/

typedef struct Btree Btree;
typedef struct BtCursor BtCursor;

int sqliteBtreeOpen(const char *zFilename, int mode, Btree **ppBtree);
int sqliteBtreeClose(Btree*);

int sqliteBtreeBeginTrans(Btree*);
int sqliteBtreeCommit(Btree*);
int sqliteBtreeRollback(Btree*);




int sqliteBtreeCursor(Btree*, BtCursor **ppCur);
int sqliteBtreeMoveto(BtCursor*, void *pKey, int nKey, *pRes);
int sqliteBtreeDelete(BtCursor*);
int sqliteBtreeInsert(BtCursor*, void *pKey, int nKey, void *pData, int nData);
int sqliteBtreeNext(BtCursor*, int *pRes);
int sqliteBtreeKeySize(BtCursor*, int *pSize);
int sqliteBtreeKey(BtCursor*, int offset, int amt, char *zBuf);
int sqliteBtreeDataSize(BtCursor*, int *pSize);








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>
>

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**   drh@hwaci.com
**   http://www.hwaci.com/drh/
**
*************************************************************************
** This header file defines the interface that the sqlite B-Tree file
** subsystem.
**
** @(#) $Id: btree.h,v 1.3 2001/06/02 02:40:57 drh Exp $
*/

typedef struct Btree Btree;
typedef struct BtCursor BtCursor;

int sqliteBtreeOpen(const char *zFilename, int mode, Btree **ppBtree);
int sqliteBtreeClose(Btree*);

int sqliteBtreeBeginTrans(Btree*);
int sqliteBtreeCommit(Btree*);
int sqliteBtreeRollback(Btree*);

int sqliteBtreeCreateTable(Btree*, int*);
int sqliteBtreeDropTable(Btree*, int);

int sqliteBtreeCursor(Btree*, int iTable, BtCursor **ppCur);
int sqliteBtreeMoveto(BtCursor*, void *pKey, int nKey, *pRes);
int sqliteBtreeDelete(BtCursor*);
int sqliteBtreeInsert(BtCursor*, void *pKey, int nKey, void *pData, int nData);
int sqliteBtreeNext(BtCursor*, int *pRes);
int sqliteBtreeKeySize(BtCursor*, int *pSize);
int sqliteBtreeKey(BtCursor*, int offset, int amt, char *zBuf);
int sqliteBtreeDataSize(BtCursor*, int *pSize);
︙︙
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*************************************************************************
** This is the implementation of the page cache subsystem.
** 
** The page cache is used to access a database file.  The pager journals
** all writes in order to support rollback.  Locking is used to limit
** access to one or more reader or one writer.
**
** @(#) $Id: pager.c,v 1.7 2001/05/24 21:06:36 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
#include <assert.h>








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*************************************************************************
** This is the implementation of the page cache subsystem.
** 
** The page cache is used to access a database file.  The pager journals
** all writes in order to support rollback.  Locking is used to limit
** access to one or more reader or one writer.
**
** @(#) $Id: pager.c,v 1.8 2001/06/02 02:40:57 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
#include <assert.h>
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#define SQLITE_UNLOCK      0
#define SQLITE_READLOCK    1
#define SQLITE_WRITELOCK   2


/*
** Each in-memory image of a page begins with the following header.


*/
typedef struct PgHdr PgHdr;
struct PgHdr {
  Pager *pPager;                 /* The pager to which this page belongs */
  Pgno pgno;                     /* The page number for this page */
  PgHdr *pNextHash, *pPrevHash;  /* Hash collision chain for PgHdr.pgno */
  int nRef;                      /* Number of users of this page */








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#define SQLITE_UNLOCK      0
#define SQLITE_READLOCK    1
#define SQLITE_WRITELOCK   2


/*
** Each in-memory image of a page begins with the following header.
** This header is only visible to this pager module.  The client
** code that calls pager sees only the data that follows the header.
*/
typedef struct PgHdr PgHdr;
struct PgHdr {
  Pager *pPager;                 /* The pager to which this page belongs */
  Pgno pgno;                     /* The page number for this page */
  PgHdr *pNextHash, *pPrevHash;  /* Hash collision chain for PgHdr.pgno */
  int nRef;                      /* Number of users of this page */
︙︙
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/*
** Copyright (c) 2001 D. Richard Hipp
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of the GNU General Public
** License as published by the Free Software Foundation; either
** version 2 of the License, or (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
** General Public License for more details.
** 
** You should have received a copy of the GNU General Public
** License along with this library; if not, write to the
** Free Software Foundation, Inc., 59 Temple Place - Suite 330,
** Boston, MA  02111-1307, USA.
**
** Author contact information:
**   drh@hwaci.com
**   http://www.hwaci.com/drh/
**
*************************************************************************
** Code for testing the btree.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test3.c,v 1.1 2001/06/02 02:40:57 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

/*
** Interpret an SQLite error number
*/
static char *errorName(int rc){
  char *zName;
  switch( rc ){
    case SQLITE_OK:         zName = "SQLITE_OK";          break;
    case SQLITE_ERROR:      zName = "SQLITE_ERROR";       break;
    case SQLITE_INTERNAL:   zName = "SQLITE_INTERNAL";    break;
    case SQLITE_PERM:       zName = "SQLITE_PERM";        break;
    case SQLITE_ABORT:      zName = "SQLITE_ABORT";       break;
    case SQLITE_BUSY:       zName = "SQLITE_BUSY";        break;
    case SQLITE_NOMEM:      zName = "SQLITE_NOMEM";       break;
    case SQLITE_READONLY:   zName = "SQLITE_READONLY";    break;
    case SQLITE_INTERRUPT:  zName = "SQLITE_INTERRUPT";   break;
    case SQLITE_IOERR:      zName = "SQLITE_IOERR";       break;
    case SQLITE_CORRUPT:    zName = "SQLITE_CORRUPT";     break;
    case SQLITE_NOTFOUND:   zName = "SQLITE_NOTFOUND";    break;
    case SQLITE_FULL:       zName = "SQLITE_FULL";        break;
    case SQLITE_CANTOPEN:   zName = "SQLITE_CANTOPEN";    break;
    case SQLITE_PROTOCOL:   zName = "SQLITE_PROTOCOL";    break;
    default:                zName = "SQLITE_Unknown";     break;
  }
  return zName;
}

/*
** Usage:   btree_open FILENAME
**
** Open a new database
*/
static int btree_open(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  char **argv            /* Text of each argument */
){
  BTree *pBt;
  int nPage;
  int rc;
  char zBuf[100];
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " FILENAME\"", 0);
    return TCL_ERROR;
  }
  rc = sqliteBtreeOpen(argv[1], 0666, &pBt);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sprintf(zBuf,"0x%x",(int)pBt);
  Tcl_AppendResult(interp, zBuf, 0);
  return TCL_OK;
}

/*
** Usage:   btree_close ID
**
** Close the given database.
*/
static int btree_close(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  char **argv            /* Text of each argument */
){
  Btree *pBt;
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pBt) ) return TCL_ERROR;
  rc = sqliteBtreeClose(pBt);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

/*
** Usage:   btree_begin_transaction ID
**
** Start a new transaction
*/
static int btree_begin_transaction(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  char **argv            /* Text of each argument */
){
  Btree *pBt;
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pBt) ) return TCL_ERROR;
  rc = sqliteBtreeBeginTrans(pBt);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

/*
** Usage:   btree_rollback ID
**
** Rollback changes
*/
static int btree_rollback(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  char **argv            /* Text of each argument */
){
  Btree *pBt
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pBt) ) return TCL_ERROR;
  rc = sqliteBtreeRollback(pBt);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

/*
** Usage:   btree_commit ID
**
** Commit all changes
*/
static int btree_commit(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  char **argv            /* Text of each argument */
){
  Btree *pBt;
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pBt) ) return TCL_ERROR;
  rc = sqliteBtreeCommit(pBt);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

/*
** Usage:   btree_create_table ID
**
** Create a new table in the database
*/
static int btree_create_table(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  char **argv            /* Text of each argument */
){
  Btree *pBt;
  int rc, iTable;
  char zBuf[30];
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pBt) ) return TCL_ERROR;
  rc = sqliteBtreeCreateTable(pBt, &iTable);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sprintf(zBuf, "%d", iTable);
  Tcl_AppendResult(interp, zBuf, 0);
  return TCL_OK;
}

/*
** Usage:   btree_drop_table ID TABLENUM
**
** Delete an entire table from the database
*/
static int btree_drop_table(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  char **argv            /* Text of each argument */
){
  Pager *pPager;
  int iTable;
  char zBuf[100];
  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID TABLENUM\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pBt) ) return TCL_ERROR;
  if( Tcl_GetInt(interp, argv[2], &iTable ) return TCL_ERROR;
  rc = sqliteBtreeDropTable(pBt, iTable);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

/*
** Register commands with the TCL interpreter.
*/
int Sqlitetest3_Init(Tcl_Interp *interp){
  Tcl_CreateCommand(interp, "btree_open", btree_open, 0, 0);
  Tcl_CreateCommand(interp, "btree_close", btree_close, 0, 0);
  Tcl_CreateCommand(interp, "btree_begin_transaction",
      btree_begin_transaction, 0, 0);
  Tcl_CreateCommand(interp, "btree_commit", btree_commit, 0, 0);
  Tcl_CreateCommand(interp, "btree_rollback", btree_rollback, 0, 0);
  Tcl_CreateCommand(interp, "btree_create_table", btree_create_table, 0, 0);
  Tcl_CreateCommand(interp, "btree_drop_table", btree_drop_table, 0, 0);
  return TCL_OK;
}