SQLite

# This is how we compile
#
TCCX = $(TCC) $(OPTS) $(THREADSAFE) $(USLEEP) -I. -I$(TOP)/src

# Object files for the SQLite library.
#
LIBOBJ = btree.o hash.o os.o pager.o random.o \
         util.o tclsqlite.o utf.o

LIBOBJ_ORIG = attach.o auth.o btree.o btree_rb.o build.o copy.o date.o delete.o \
         expr.o func.o hash.o insert.o \
         main.o opcodes.o os.o pager.o parse.o pragma.o printf.o random.o \
         select.o table.o tokenize.o trigger.o update.o util.o \
         vacuum.o vdbe.o vdbeaux.o where.o tclsqlite.o

# All of the source code files.
#
SRC = \
  $(TOP)/src/btree.c \
  $(TOP)/src/btree.h \
  $(TOP)/src/hash.c \
  $(TOP)/src/hash.h \
  $(TOP)/src/os.c \
  $(TOP)/src/pager.c \
  $(TOP)/src/pager.h \
  $(TOP)/src/random.c \
  $(TOP)/src/util.c 

# Source code to the test files.
#
TESTSRC = \
  $(TOP)/src/os.c \
  $(TOP)/src/pager.c \
  $(TOP)/src/test2.c \
  $(TOP)/src/test3.c \
  $(TOP)/src/test5.c \
  $(TOP)/src/md5.c

TESTSRC_ORIG = \
  $(TOP)/src/btree.c \
  $(TOP)/src/func.c \
  $(TOP)/src/os.c \

/*
** 2004 April 6
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.110 2004/05/07 13:30:42 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.

  int maxLocal;         /* Maximum local payload */
};
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
** MemPage.aCell[] of the entry.
*/
struct BtCursor {
  Btree *pBt;               /* The Btree to which this cursor belongs */
  BtCursor *pNext, *pPrev;  /* Forms a linked list of all cursors */
  BtCursor *pShared;        /* Loop of cursors with the same root page */
  int (*xCompare)(void*,int,const void*,int,const void*); /* Key comp func */
  void *pArg;               /* First arg to xCompare() */

** 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 space allocated on overflow pages
** is NOT included in the value returned from this routine.
*/
static int cellSize(MemPage *pPage, unsigned char *pCell){

  int n;
  u64 nData, nKey;
  int nPayload, maxPayload;

  parseCellHeader(pPage, pCell, &nData, &nKey, &n);
  nPayload = (int)nData;
  if( !pPage->intKey ){

static void defragmentPage(MemPage *pPage){
  int pc, i, n, addr;
  int start, hdr, size;
  int leftover;
  unsigned char *oldPage;
  unsigned char newPage[MX_PAGE_SIZE];

  assert( sqlite3pager_iswriteable(pPage->aData) );
  assert( pPage->pBt!=0 );
  assert( pPage->pBt->pageSize <= MX_PAGE_SIZE );
  oldPage = pPage->aData;
  hdr = pPage->hdrOffset;
  addr = 3+hdr;
  n = 6+hdr;
  if( !pPage->leaf ){
    n += 4;
  }

  int size;
  unsigned char *data;
#ifndef NDEBUG
  int cnt = 0;
#endif

  data = pPage->aData;
  assert( sqlite3pager_iswriteable(data) );
  assert( pPage->pBt );
  if( nByte<4 ) nByte = 4;
  if( pPage->nFree<nByte || pPage->isOverfull ) return 0;
  hdr = pPage->hdrOffset;
  if( data[hdr+5]>=60 ){
    defragmentPage(pPage);
  }
  addr = hdr+1;
  pc = get2byte(&data[addr]);
  assert( addr<pc );
  assert( pc<=pPage->pBt->pageSize-4 );
  while( (size = get2byte(&data[pc+2]))<nByte ){
    addr = pc;
    pc = get2byte(&data[addr]);
    assert( pc<=pPage->pBt->pageSize-4 );
    assert( pc>=addr+size+4 || pc==0 );
    if( pc==0 ){
      assert( (cnt++)==0 );
      defragmentPage(pPage);
      assert( data[hdr+5]==0 );
      addr = pPage->hdrOffset+1;
      pc = get2byte(&data[addr]);
    }
  }
  assert( pc>0 && size>=nByte );
  assert( pc+size<=pPage->pBt->pageSize );
  if( size>nByte+4 ){
    put2byte(&data[addr], pc+nByte);
    put2byte(&data[pc+size], get2byte(&data[pc]));
    put2byte(&data[pc+size+2], size-nByte);
  }else{
    put2byte(&data[addr], get2byte(&data[pc]));
    data[hdr+5] += size-nByte;

** and the size of the block is "size" bytes.
**
** Most of the effort here is involved in coalesing adjacent
** free blocks into a single big free block.
*/
static void freeSpace(MemPage *pPage, int start, int size){
  int end = start + size;  /* End of the segment being freed */
  int addr, pbegin;
#ifndef NDEBUG
  int tsize = 0;          /* Total size of all freeblocks */
#endif
  unsigned char *data = pPage->aData;

  assert( pPage->pBt!=0 );
  assert( sqlite3pager_iswriteable(data) );
  assert( start>=pPage->hdrOffset+6+(pPage->leaf?0:4) );
  assert( end<=pPage->pBt->pageSize );
  if( size<4 ) size = 4;

  /* Add the space back into the linked list of freeblocks */
  addr = pPage->hdrOffset + 1;
  while( (pbegin = get2byte(&data[addr]))<start && pbegin>0 ){
    assert( pbegin<=pPage->pBt->pageSize-4 );
    assert( pbegin>addr );
    addr = pbegin;
  }
  assert( pbegin<=pPage->pBt->pageSize-4 );
  assert( pbegin>addr || pbegin==0 );
  put2byte(&data[addr], start);
  put2byte(&data[start], pbegin);
  put2byte(&data[start+2], size);
  pPage->nFree += size;

  /* Coalesce adjacent free blocks */
  addr = pPage->hdrOffset + 1;
  while( (pbegin = get2byte(&data[addr]))>0 ){
    int pnext, psize;
    assert( pbegin>addr );

/*
** Resize the aCell[] array of the given page so that it is able to
** hold at least nNewSz entries.
**
** Return SQLITE_OK or SQLITE_NOMEM.
*/
static int resizeCellArray(MemPage *pPage, int nNewSz){
  if( pPage->nCellAlloc<nNewSz ){
    pPage->aCell = sqliteRealloc(pPage->aCell, nNewSz*sizeof(pPage->aCell[0]) );
    if( sqlite_malloc_failed ) return SQLITE_NOMEM;
    pPage->nCellAlloc = nNewSz;
  }
  return SQLITE_OK;
}

/*
** Initialize the auxiliary information for a disk block.
**

** we failed to detect any corruption.
*/
static int initPage(
  MemPage *pPage,        /* The page to be initialized */
  MemPage *pParent       /* The parent.  Might be NULL */
){
  int c, pc, i, hdr;
  unsigned char *data;
  int pageSize;
  int sumCell = 0;       /* Total size of all cells */

  assert( pPage->pBt!=0 );
  assert( pParent==0 || pParent->pBt==pPage->pBt );
  assert( pPage->pgno==sqlite3pager_pagenumber(pPage->aData) );
  assert( pPage->aData == &((unsigned char*)pPage)[pPage->pBt->pageSize] );
  assert( pPage->isInit==0 || pPage->pParent==pParent );
  if( pPage->isInit ) return SQLITE_OK;
  assert( pPage->pParent==0 );
  pPage->pParent = pParent;
  if( pParent ){
    sqlite3pager_ref(pParent->aData);
  }
  pPage->nCell = pPage->nCellAlloc = 0;
  pPage->hdrOffset = hdr = pPage->pgno==1 ? 100 : 0;
  data = pPage->aData;
  c = data[hdr];
  pPage->intKey = (c & PTF_INTKEY)!=0;
  pPage->zeroData = (c & PTF_ZERODATA)!=0;
  pPage->leaf = (c & PTF_LEAF)!=0;
  pageSize = pPage->pBt->pageSize;

  /* Initialize the cell count and cell pointers */
  pc = get2byte(&data[hdr+3]);
  while( pc>0 ){
    if( pc>=pageSize ) return SQLITE_CORRUPT;
    if( pPage->nCell>pageSize ) return SQLITE_CORRUPT;
    pPage->nCell++;
    pc = get2byte(&data[pc]);
  }
  if( resizeCellArray(pPage, pPage->nCell) ){
    return SQLITE_NOMEM;
  }
  pc = get2byte(&data[hdr+3]);
  for(i=0; pc>0; i++){
    pPage->aCell[i] = &data[pc];
    pc = get2byte(&data[pc]);
    sumCell += cellSize(pPage, &data[pc]);
  }

  /* Compute the total free space on the page */
  pPage->nFree = data[hdr+5];
  pc = get2byte(&data[hdr+1]);
  while( pc>0 ){
    int next, size;
    if( pc>=pageSize ) return SQLITE_CORRUPT;
    next = get2byte(&data[pc]);
    size = get2byte(&data[pc+2]);
    if( next>0 && next<=pc+size+3 ) return SQLITE_CORRUPT;
    pPage->nFree += size;
    pc = next;
  }
  if( pPage->nFree>=pageSize ) return SQLITE_CORRUPT;

  /* Sanity check:  Cells and freespace and header must sum to the size
  ** a page. */
  if( sumCell+pPage->nFree+hdr+10-pPage->leaf*4 != pageSize ){
    return SQLITE_CORRUPT;
  }

  return SQLITE_OK;
}

/*
** Set up a raw page so that it looks like a database page holding
** no entries.
*/
static void zeroPage(MemPage *pPage, int flags){
  unsigned char *data = pPage->aData;
  Btree *pBt = pPage->pBt;
  int hdr = pPage->hdrOffset;
  int first;

  assert( sqlite3pager_iswriteable(data) );
  memset(&data[hdr], 0, pBt->pageSize - hdr);
  data[hdr] = flags;
  first = hdr + 6 + 4*((flags&0x01)!=0);
  put2byte(&data[hdr+1], first);
  put2byte(&data[first+2], pBt->pageSize - first);
  sqliteFree(pPage->aCell);
  pPage->aCell = 0;

** Get a page from the pager.  Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
*/
static int getPage(Btree *pBt, Pgno pgno, MemPage **ppPage){
  int rc;
  unsigned char *aData;
  MemPage *pPage;
  rc = sqlite3pager_get(pBt->pPager, pgno, (void**)&aData);
  if( rc ) return rc;
  pPage = (MemPage*)&aData[pBt->pageSize];
  pPage->aData = aData;
  pPage->pBt = pBt;
  pPage->pgno = pgno;
  *ppPage = pPage;
  return SQLITE_OK;
}

/*
** Release a MemPage.  This should be called once for each prior
** call to getPage.
*/
static void releasePage(MemPage *pPage){
  if( pPage ){
    assert( pPage->aData );
    assert( pPage->pBt );
    assert( &pPage->aData[pPage->pBt->pageSize]==(unsigned char*)pPage );
    sqlite3pager_unref(pPage->aData);
  }
}

/*
** 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){
  MemPage *pPage = (MemPage*)&((char*)pData)[SQLITE_PAGE_SIZE];
  if( pPage->pParent ){
    MemPage *pParent = pPage->pParent;
    pPage->pParent = 0;
    releasePage(pParent);
  }
  sqliteFree(pPage->aCell);
  pPage->aCell = 0;
  pPage->isInit = 0;
}

/*

int sqlite3BtreeOpen(
  const char *zFilename,  /* Name of the file containing the BTree database */
  Btree **ppBtree,        /* Pointer to new Btree object written here */
  int nCache,             /* Number of cache pages */
  int flags               /* Options */
){
  Btree *pBt;
  int rc;



  /*
  ** The following asserts make sure that structures used by the btree are
  ** the right size.  This is to guard against size changes that result
  ** when compiling on a different architecture.
  */
  assert( sizeof(u64)==8 );
  assert( sizeof(u32)==4 );
  assert( sizeof(u16)==2 );
  assert( sizeof(Pgno)==4 );
  assert( sizeof(ptr)==sizeof(char*) );
  assert( sizeof(uptr)==sizeof(ptr) );

  pBt = sqliteMalloc( sizeof(*pBt) );
  if( pBt==0 ){
    *ppBtree = 0;
    return SQLITE_NOMEM;
  }
  if( nCache<10 ) nCache = 10;
  rc = sqlite3pager_open(&pBt->pPager, zFilename, nCache, EXTRA_SIZE,
                        (flags & BTREE_OMIT_JOURNAL)==0);
  if( rc!=SQLITE_OK ){
    if( pBt->pPager ) sqlite3pager_close(pBt->pPager);
    sqliteFree(pBt);
    *ppBtree = 0;
    return rc;
  }
  sqlite3pager_set_destructor(pBt->pPager, pageDestructor);
  pBt->pCursor = 0;
  pBt->pPage1 = 0;
  pBt->readOnly = sqlite3pager_isreadonly(pBt->pPager);
  pBt->pageSize = SQLITE_PAGE_SIZE;  /* FIX ME - read from header */
  pBt->maxLocal = (pBt->pageSize-10)/4-12;
  *ppBtree = pBt;
  return SQLITE_OK;
}

/*
** Close an open database and invalidate all cursors.
*/
int sqlite3BtreeClose(Btree *pBt){
  while( pBt->pCursor ){
    sqlite3BtreeCloseCursor(pBt->pCursor);
  }
  sqlite3pager_close(pBt->pPager);
  sqliteFree(pBt);
  return SQLITE_OK;
}

/*
** Change the limit on the number of pages allowed in the cache.
**
** The maximum number of cache pages is set to the absolute
** value of mxPage.  If mxPage is negative, the pager will
** operate asynchronously - it will not stop to do fsync()s
** to insure data is written to the disk surface before
** continuing.  Transactions still work if synchronous is off,
** and the database cannot be corrupted if this program
** crashes.  But if the operating system crashes or there is
** an abrupt power failure when synchronous is off, the database
** could be left in an inconsistent and unrecoverable state.
** Synchronous is on by default so database corruption is not
** normally a worry.
*/
int sqlite3BtreeSetCacheSize(Btree *pBt, int mxPage){
  sqlite3pager_set_cachesize(pBt->pPager, mxPage);
  return SQLITE_OK;
}

/*
** Change the way data is synced to disk in order to increase or decrease
** how well the database resists damage due to OS crashes and power
** failures.  Level 1 is the same as asynchronous (no syncs() occur and
** there is a high probability of damage)  Level 2 is the default.  There
** is a very low but non-zero probability of damage.  Level 3 reduces the
** probability of damage to near zero but with a write performance reduction.
*/
int sqlite3BtreeSetSafetyLevel(Btree *pBt, int level){
  sqlite3pager_set_safety_level(pBt->pPager, level);
  return SQLITE_OK;
}

/*
** Get a reference to pPage1 of the database file.  This will
** also acquire a readlock on that file.
**
** SQLITE_OK is returned on success.  If the file is not a
** well-formed database file, then SQLITE_CORRUPT is returned.
** SQLITE_BUSY is returned if the database is locked.  SQLITE_NOMEM
** is returned if we run out of memory.  SQLITE_PROTOCOL is returned
** if there is a locking protocol violation.
*/
static int lockBtree(Btree *pBt){
  int rc;
  MemPage *pPage1;
  if( pBt->pPage1 ) return SQLITE_OK;
  rc = getPage(pBt, 1, &pPage1);
  if( rc!=SQLITE_OK ) return rc;
  

  /* Do some checking to help insure the file we opened really is
  ** a valid database file. 
  */
  if( sqlite3pager_pagecount(pBt->pPager)>0 ){
    if( memcmp(pPage1->aData, zMagicHeader, 16)!=0 ){
      rc = SQLITE_NOTADB;
      goto page1_init_failed;
    }
    /*** TBD:  Other header checks such as page size ****/
  }
  pBt->pPage1 = pPage1;

** Create a new database by initializing the first page of the
** file.
*/
static int newDatabase(Btree *pBt){
  MemPage *pP1;
  unsigned char *data;
  int rc;
  if( sqlite3pager_pagecount(pBt->pPager)>1 ) return SQLITE_OK;
  pP1 = pBt->pPage1;
  assert( pP1!=0 );
  data = pP1->aData;
  rc = sqlite3pager_write(data);
  if( rc ) return rc;
  memcpy(data, zMagicHeader, sizeof(zMagicHeader));
  assert( sizeof(zMagicHeader)==16 );
  put2byte(&data[16], SQLITE_PAGE_SIZE);
  data[18] = 1;
  data[19] = 1;
  put2byte(&data[22], (SQLITE_PAGE_SIZE-10)/4-12);

  if( pBt->readOnly ) return SQLITE_READONLY;
  if( pBt->pPage1==0 ){
    rc = lockBtree(pBt);
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }
  rc = sqlite3pager_begin(pBt->pPage1->aData);
  if( rc==SQLITE_OK ){
    rc = newDatabase(pBt);
  }
  if( rc==SQLITE_OK ){
    pBt->inTrans = 1;
    pBt->inStmt = 0;
  }else{
    unlockBtreeIfUnused(pBt);
  }
  return rc;
}

/*
** Commit the transaction currently in progress.
**
** This will release the write lock on the database file.  If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeCommit(Btree *pBt){
  int rc;
  rc = pBt->readOnly ? SQLITE_OK : sqlite3pager_commit(pBt->pPager);
  pBt->inTrans = 0;
  pBt->inStmt = 0;
  unlockBtreeIfUnused(pBt);
  return rc;
}

/*

*/
int sqlite3BtreeRollback(Btree *pBt){
  int rc;
  BtCursor *pCur;
  if( pBt->inTrans==0 ) return SQLITE_OK;
  pBt->inTrans = 0;
  pBt->inStmt = 0;
  rc = pBt->readOnly ? SQLITE_OK : sqlite3pager_rollback(pBt->pPager);
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    MemPage *pPage = pCur->pPage;
    if( pPage && !pPage->isInit ){
      releasePage(pPage);
      pCur->pPage = 0;
    }
  }

** to start a new checkpoint if another checkpoint is already active.
*/
int sqlite3BtreeBeginStmt(Btree *pBt){
  int rc;
  if( !pBt->inTrans || pBt->inStmt ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  rc = pBt->readOnly ? SQLITE_OK : sqlite3pager_stmt_begin(pBt->pPager);
  pBt->inStmt = 1;
  return rc;
}


/*
** Commit a checkpoint to transaction currently in progress.  If no
** checkpoint is active, this is a no-op.
*/
int sqlite3BtreeCommitStmt(Btree *pBt){
  int rc;
  if( pBt->inStmt && !pBt->readOnly ){
    rc = sqlite3pager_stmt_commit(pBt->pPager);
  }else{
    rc = SQLITE_OK;
  }
  pBt->inStmt = 0;
  return rc;
}

/*
** Rollback the checkpoint to the current transaction.  If there
** is no active checkpoint or transaction, this routine is a no-op.
**
** All cursors will be invalided by this operation.  Any attempt
** to use a cursor that was open at the beginning of this operation
** will result in an error.
*/
int sqlite3BtreeRollbackStmt(Btree *pBt){
  int rc;
  BtCursor *pCur;
  if( pBt->inStmt==0 || pBt->readOnly ) return SQLITE_OK;
  rc = sqlite3pager_stmt_rollback(pBt->pPager);
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    MemPage *pPage = pCur->pPage;
    if( pPage && !pPage->isInit ){
      releasePage(pPage);
      pCur->pPage = 0;
    }
  }

** The temporary cursor is not on the cursor list for the Btree.
*/
static void getTempCursor(BtCursor *pCur, BtCursor *pTempCur){
  memcpy(pTempCur, pCur, sizeof(*pCur));
  pTempCur->pNext = 0;
  pTempCur->pPrev = 0;
  if( pTempCur->pPage ){
    sqlite3pager_ref(pTempCur->pPage->aData);
  }
}

/*
** Delete a temporary cursor such as was made by the CreateTemporaryCursor()
** function above.
*/
static void releaseTempCursor(BtCursor *pCur){
  if( pCur->pPage ){
    sqlite3pager_unref(pCur->pPage->aData);
  }
}

/*
** Set *pSize to the size of the buffer needed to hold the value of
** the key for the current entry.  If the cursor is not pointing
** to a valid entry, *pSize is set to 0. 

  }else{
    unsigned char *cell = pPage->aCell[pCur->idx];
    cell += 2;   /* Skip the offset to the next cell */
    if( pPage->leaf ){
      cell += 4;  /* Skip the child pointer */
    }
    if( !pPage->zeroData ){
      while( (0x80&*(cell++))!=0 ){}  /* Skip the data size number */
    }
    getVarint(cell, pSize);
  }
  return SQLITE_OK;
}

/*
** Read payload information from the entry that the pCur cursor is
** pointing to.  Begin reading the payload at "offset" and read

    aPayload += 4;  /* Skip the child pointer */
  }
  if( pPage->zeroData ){
    nData = 0;
  }else{
    aPayload += getVarint(aPayload, &nData);
  }
  aPayload += getVarint(aPayload, &nKey);
  if( pPage->intKey ){
    nKey = 0;
  }
  assert( offset>=0 );
  if( skipKey ){
    offset += nKey;
  }
  if( offset+amt > nKey+nData ){
    return SQLITE_ERROR;
  }
  maxLocal = pBt->maxLocal;
  if( offset<maxLocal ){
    int a = amt;
    if( a+offset>maxLocal ){
      a = maxLocal - offset;
    }
    memcpy(pBuf, &aPayload[offset], a);
    if( a==amt ){
      return SQLITE_OK;
    }
    offset = 0;
    pBuf += a;
    amt -= a;
  }else{
    offset -= maxLocal;
  }
  if( amt>0 ){
    nextPage = get4byte(&aPayload[maxLocal]);
  }
  ovflSize = pBt->pageSize - 4;
  while( amt>0 && nextPage ){
    rc = sqlite3pager_get(pBt->pPager, nextPage, (void**)&aPayload);
    if( rc!=0 ){
      return rc;
    }
    nextPage = get4byte(aPayload);
    if( offset<ovflSize ){
      int a = amt;
      if( a + offset > ovflSize ){
        a = ovflSize - offset;
      }
      memcpy(pBuf, &aPayload[offset], a);
      offset = 0;
      amt -= a;
      pBuf += a;
    }else{
      offset -= ovflSize;
    }
    sqlite3pager_unref(aPayload);
  }
  if( amt>0 ){
    return SQLITE_CORRUPT;
  }
  return SQLITE_OK;
}

/*
** Read part of the key associated with cursor pCur.  Exactly
** "amt" bytes will be transfered into pBuf[].  The transfer
** begins at "offset".
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong.  An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite3BtreeKey(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
  MemPage *pPage;

  assert( amt>=0 );
  assert( offset>=0 );
  assert( pCur->pPage!=0 );
  pPage = pCur->pPage;
  if( pCur->idx >= pPage->nCell || pPage->intKey ){

  aPayload += 2;  /* Skip the next cell index */
  if( pPage->leaf ){
    aPayload += 4;  /* Skip the child pointer */
  }
  if( !pPage->zeroData ){
    aPayload += getVarint(aPayload, &nData);
  }
  aPayload += getVarint(aPayload, &nKey);
  if( pPage->intKey || nKey>pBt->maxLocal ){
    return 0;
  }
  return aPayload;
}

    unsigned char *cell;
    u64 size;
    cell = pPage->aCell[pCur->idx];
    cell += 2;   /* Skip the offset to the next cell */
    if( pPage->leaf ){
      cell += 4;  /* Skip the child pointer */
    }
    getVarint(cell, &size);
    assert( (size & 0x00000000ffffffff)==size );
    *pSize = (u32)size;
  }
  return SQLITE_OK;
}

/*
** Read part of the data associated with cursor pCur.  Exactly
** "amt" bytes will be transfered into pBuf[].  The transfer
** begins at "offset".
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong.  An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite3BtreeData(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
  MemPage *pPage;

  assert( amt>=0 );
  assert( offset>=0 );
  assert( pCur->pPage!=0 );
  pPage = pCur->pPage;
  if( pCur->idx >= pPage->nCell ){
    return 0;
  }

  return getPayload(pCur, offset, amt, pBuf, 1);
}

/*
** Move the cursor down to a new child page.  The newPgno argument is the
** page number of the child page in the byte order of the disk image.
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
  int rc;
  MemPage *pNewPage;
  MemPage *pOldPage;

  Btree *pBt = pCur->pBt;

  rc = getPage(pBt, newPgno, &pNewPage);
  if( rc ) return rc;
  rc = initPage(pNewPage, pCur->pPage);
  if( rc ) return rc;
  pNewPage->idxParent = pCur->idx;

  pPage = pCur->pPage;
  assert( pPage!=0 );
  assert( !isRootPage(pPage) );
  pParent = pPage->pParent;
  assert( pParent!=0 );
  idxParent = pPage->idxParent;
  sqlite3pager_ref(pParent->aData);
  oldPgno = pPage->pgno;
  releasePage(pPage);
  pCur->pPage = pParent;
  assert( pParent->idxShift==0 );
  if( pParent->idxShift==0 ){
    pCur->idx = idxParent;
#ifndef NDEBUG  
    /* Verify that pCur->idx is the correct index to point back to the child
    ** page we just came from 
    */
    if( pCur->idx<pParent->nCell ){
      assert( get4byte(&pParent->aCell[idxParent][2])==oldPgno );
    }else{
      assert( get4byte(&pParent->aData[pParent->hdrOffset+6])==oldPgno );
    }
#endif
  }else{
    /* The MemPage.idxShift flag indicates that cell indices might have 
    ** changed since idxParent was set and hence idxParent might be out
    ** of date.  So recompute the parent cell index by scanning all cells
    ** and locating the one that points to the child we just came from.

*/
static int moveToLeftmost(BtCursor *pCur){
  Pgno pgno;
  int rc;
  MemPage *pPage;

  while( !(pPage = pCur->pPage)->leaf ){
    assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
    pgno = get4byte(&pPage->aCell[pCur->idx][2]);
    rc = moveToChild(pCur, pgno);
    if( rc ) return rc;
  }
  return SQLITE_OK;
}

/*

      }else{
        upr = pCur->idx-1;
      }
    }
    assert( lwr==upr+1 );
    assert( pPage->isInit );
    if( pPage->leaf ){
      chldPg = 0;
    }else if( lwr>=pPage->nCell ){
      chldPg = get4byte(&pPage->aData[pPage->hdrOffset+6]);
    }else{
      chldPg = get4byte(&pPage->aCell[lwr][2]);
    }
    if( chldPg==0 ){
      pCur->iMatch = c;

    pCur->eSkip = SKIP_NONE;
    *pRes = 0;
    return SQLITE_OK;
  }
  pCur->eSkip = SKIP_NONE;
  pCur->idx++;
  if( pCur->idx>=pPage->nCell ){
    if( !pPage->leaf ){
      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+6]));
      if( rc ) return rc;
      rc = moveToLeftmost(pCur);
      *pRes = 0;
      return rc;
    }
    do{
      if( isRootPage(pPage) ){

  if( pCur->eSkip==SKIP_PREV ){
    pCur->eSkip = SKIP_NONE;
    *pRes = 0;
    return SQLITE_OK;
  }
  pCur->eSkip = SKIP_NONE;
  assert( pCur->idx>=0 );
  if( !pPage->leaf ){
    pgno = get4byte(&pPage->aCell[pCur->idx][2]);
    rc = moveToChild(pCur, pgno);
    if( rc ) return rc;
    rc = moveToRightmost(pCur);
  }else{
    while( pCur->idx==0 ){
      if( isRootPage(pPage) ){

  *pRes = 0;
  return rc;
}

/*
** Allocate a new page from the database file.
**
** The new page is marked as dirty.  (In other words, sqlite3pager_write()
** has already been called on the new page.)  The new page has also
** been referenced and the calling routine is responsible for calling
** sqlite3pager_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 sqlite3pager_unref() on *ppPage if an error is returned.
**
** If the "nearby" parameter is not 0, then a (feeble) effort is made to 
** locate a page close to the page number "nearby".  This can be used in an
** attempt to keep related pages close to each other in the database file,
** which in turn can make database access faster.
*/
static int allocatePage(Btree *pBt, MemPage **ppPage, Pgno *pPgno, Pgno nearby){

  MemPage *pPage1;

  int rc;
  int n;     /* Number of pages on the freelist */
  int k;     /* Number of leaves on the trunk of the freelist */

  pPage1 = pBt->pPage1;
  n = get4byte(&pPage1->aData[36]);
  if( n>0 ){
    /* There are pages on the freelist.  Reuse one of those pages. */
    MemPage *pTrunk;
    rc = sqlite3pager_write(pPage1->aData);
    if( rc ) return rc;
    put4byte(&pPage1->aData[36], n-1);
    rc = getPage(pBt, get4byte(&pPage1->aData[32]), &pTrunk);
    if( rc ) return rc;
    rc = sqlite3pager_write(pTrunk->aData);
    if( rc ){
      releasePage(pTrunk);
      return rc;
    }
    k = get4byte(&pTrunk->aData[4]);
    if( k==0 ){
      /* The trunk has no leaves.  So extract the trunk page itself and
      ** use it as the newly allocated page */
      *pPgno = get4byte(&pPage1->aData[32]);
      memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
      *ppPage = pTrunk;
    }else{
      /* Extract a leaf from the trunk */
      int closest;
      unsigned char *aData = pTrunk->aData;
      if( nearby>0 ){
        int i, dist;
        closest = 0;
        dist = get4byte(&aData[8]) - nearby;
        if( dist<0 ) dist = -dist;
        for(i=1; i<n; i++){
          int d2 = get4byte(&aData[8+i*4]) - nearby;
          if( d2<0 ) d2 = -d2;
          if( d2<dist ) closest = i;
        }
      }else{
        closest = 0;
      }
      put4byte(&aData[4], n-1);
      *pPgno = get4byte(&aData[8+closest*4]);
      memcpy(&aData[8+closest*4], &aData[4+closest*n], 4);
      rc = getPage(pBt, *pPgno, ppPage);
      releasePage(pTrunk);
      if( rc==SQLITE_OK ){
        sqlite3pager_dont_rollback(*ppPage);
        rc = sqlite3pager_write((*ppPage)->aData);
      }
    }
  }else{
    /* There are no pages on the freelist, so create a new page at the
    ** end of the file */
    *pPgno = sqlite3pager_pagecount(pBt->pPager) + 1;
    rc = getPage(pBt, *pPgno, ppPage);
    if( rc ) return rc;
    rc = sqlite3pager_write((*ppPage)->aData);
  }
  return rc;
}

/*
** Add a page of the database file to the freelist.
**
** sqlite3pager_unref() is NOT called for pPage.
*/
static int freePage(MemPage *pPage){
  Btree *pBt = pPage->pBt;
  MemPage *pPage1 = pBt->pPage1;
  int rc, n, k;

  /* Prepare the page for freeing */
  assert( pPage->pgno>1 );
  pPage->isInit = 0;
  releasePage(pPage->pParent);
  pPage->pParent = 0;

  /* Increment the free page count on pPage1 */
  rc = sqlite3pager_write(pPage1->aData);
  if( rc ) return rc;
  n = get4byte(&pPage1->aData[36]);
  put4byte(&pPage1->aData[36], n+1);

  if( n==0 ){
    /* This is the first free page */
    memset(pPage->aData, 0, 8);
    put4byte(&pPage1->aData[32], pPage->pgno);
  }else{
    /* Other free pages already exist.  Retrive the first trunk page
    ** of the freelist and find out how many leaves it has. */
    MemPage *pTrunk;
    rc = getPage(pBt, get4byte(&pPage1->aData[32]), &pTrunk);
    if( rc ) return rc;
    k = get4byte(&pTrunk->aData[4]);
    if( k==pBt->pageSize/4 - 8 ){
      /* The trunk is full.  Turn the page being freed into a new
      ** trunk page with no leaves. */
      rc = sqlite3pager_write(pPage->aData);
      if( rc ) return rc;
      put4byte(pPage->aData, pTrunk->pgno);
      put4byte(&pPage->aData[4], 0);
      put4byte(&pPage1->aData[32], pPage->pgno);
    }else{
      /* Add the newly freed page as a leaf on the current trunk */
      rc = sqlite3pager_write(pTrunk->aData);
      if( rc ) return rc;
      put4byte(&pTrunk->aData[4], k+1);
      put4byte(&pTrunk->aData[8+k*4], pPage->pgno);
      sqlite3pager_dont_write(pBt->pPager, pPage->pgno);
    }
    releasePage(pTrunk);
  }
  return rc;
}

/*
** Free any overflow pages associated with the given Cell.
*/
static int clearCell(MemPage *pPage, unsigned char *pCell){
  Btree *pBt = pPage->pBt;
  int rc, n, nPayload;
  u64 nData, nKey;
  Pgno ovflPgno;

  parseCellHeader(pPage, pCell, &nData, &nKey, &n);
  assert( (nData&0x000000007fffffff)==nData );
  nPayload = (int)nData;
  if( !pPage->intKey ){
    nPayload += nKey;
  }
  if( nPayload<=pBt->maxLocal ){
    return SQLITE_OK;  /* No overflow pages. Return without doing anything */
  }
  ovflPgno = get4byte(&pCell[n+pBt->maxLocal]);
  while( ovflPgno!=0 ){
    MemPage *pOvfl;
    rc = getPage(pBt, ovflPgno, &pOvfl);
    if( rc ) return rc;
    ovflPgno = get4byte(pOvfl->aData);
    rc = freePage(pOvfl);
    if( rc ) return rc;
    sqlite3pager_unref(pOvfl->aData);
  }
  return SQLITE_OK;
}

/*
** Create the byte sequence used to represent a cell on page pPage
** and write that byte sequence into pCell[].  Overflow pages are

  unsigned char *pCell,          /* Complete text of the cell */
  const void *pKey, u64 nKey,    /* The key */
  const void *pData,int nData,   /* The data */
  int *pnSize                    /* Write cell size here */
){
  int nPayload;
  const void *pSrc;
  int nSrc, n, rc;
  int spaceLeft;
  MemPage *pOvfl = 0;
  unsigned char *pPrior;
  unsigned char *pPayload;
  Btree *pBt = pPage->pBt;
  Pgno pgnoOvfl = 0;
  int nHeader;

*/
static void reparentPage(Btree *pBt, Pgno pgno, MemPage *pNewParent, int idx){
  MemPage *pThis;
  unsigned char *aData;

  if( pgno==0 ) return;
  assert( pBt->pPager!=0 );
  aData = sqlite3pager_lookup(pBt->pPager, pgno);
  pThis = (MemPage*)&aData[pBt->pageSize];
  if( pThis && pThis->isInit ){
    if( pThis->pParent!=pNewParent ){
      if( pThis->pParent ) sqlite3pager_unref(pThis->pParent->aData);
      pThis->pParent = pNewParent;
      if( pNewParent ) sqlite3pager_ref(pNewParent->aData);
    }
    pThis->idxParent = idx;
    sqlite3pager_unref(aData);
  }
}

/*
** Change the pParent pointer of all children of pPage to point back
** to pPage.
**
** In other words, for every child of pPage, invoke reparentPage()
** to make sure that each child knows that pPage is its parent.
**
** This routine gets called after you memcpy() one page into
** another.
*/
static void reparentChildPages(MemPage *pPage){
  int i;
  Btree *pBt;

  if( pPage->leaf ) return;
  pBt = pPage->pBt;
  for(i=0; i<pPage->nCell; i++){
    reparentPage(pBt, get4byte(&pPage->aCell[i][2]), pPage, i);
  }
  reparentPage(pBt, get4byte(&pPage->aData[pPage->hdrOffset+6]), pPage, i);
  pPage->idxShift = 0;
}

/*
** Remove the i-th cell from pPage.  This routine effects pPage only.
** The cell content is not freed or deallocated.  It is assumed that
** the cell content has been copied someplace else.  This routine just
** removes the reference to the cell from pPage.
**
** "sz" must be the number of bytes in the cell.
**
** Do not bother maintaining the integrity of the linked list of Cells.
** Only the pPage->aCell[] array is important.  The relinkCellList() 
** routine will be called soon after this routine in order to rebuild 
** the linked list.
*/
static void dropCell(MemPage *pPage, int idx, int sz){
  int j;
  assert( idx>=0 && idx<pPage->nCell );
  assert( sz==cellSize(pPage, pPage->aCell[idx]) );
  assert( sqlite3pager_iswriteable(pPage->aData) );
  assert( pPage->aCell[idx]>=pPage->aData );
  assert( pPage->aCell[idx]<&pPage->aData[pPage->pBt->pageSize-sz] );
  freeSpace(pPage, idx, sz);
  for(j=idx; j<pPage->nCell-1; j++){
    pPage->aCell[j] = pPage->aCell[j+1];
  }
  pPage->nCell--;
  pPage->idxShift = 1;
}

/*
** Insert a new cell on pPage at cell index "i".  pCell points to the
** content of the cell.
**
** If the cell content will fit on the page, then put it there.  If it
** will not fit, then just make pPage->aCell[i] point to the content
** and set pPage->isOverfull.  
**
** Do not bother maintaining the integrity of the linked list of Cells.
** Only the pPage->aCell[] array is important.  The relinkCellList() 
** routine will be called soon after this routine in order to rebuild 
** the linked list.
*/
static void insertCell(MemPage *pPage, int i, unsigned char *pCell, int sz){
  int idx, j;
  assert( i>=0 && i<=pPage->nCell );
  assert( sz==cellSize(pPage, pCell) );
  assert( sqlite3pager_iswriteable(pPage->aData) );
  idx = allocateSpace(pPage, sz);
  resizeCellArray(pPage, pPage->nCell+1);
  for(j=pPage->nCell; j>i; j--){
    pPage->aCell[j] = pPage->aCell[j-1];
  }
  pPage->nCell++;
  if( idx<=0 ){
    pPage->isOverfull = 1;

** Rebuild the linked list of cells on a page so that the cells
** occur in the order specified by the pPage->aCell[] array.  
** Invoke this routine once to repair damage after one or more
** invocations of either insertCell() or dropCell().
*/
static void relinkCellList(MemPage *pPage){
  int i, idxFrom;
  assert( sqlite3pager_iswriteable(pPage->aData) );
  idxFrom = pPage->hdrOffset+3;
  for(i=0; i<pPage->nCell; i++){
    int idx = Addr(pPage->aCell[i]) - Addr(pPage);
    assert( idx>pPage->hdrOffset && idx<pPage->pBt->pageSize );
    put2byte(&pPage->aData[idxFrom], idx);
    idxFrom = idx;
  }

** If this routine fails for any reason, it might leave the database
** in a corrupted state.  So if this routine fails, the database should
** be rolled back.
*/
static int balance(MemPage *pPage){
  MemPage *pParent;            /* The parent of pPage */
  Btree *pBt;                  /* The whole database */
  int nCell;                   /* Number of cells in aCell[] */
  int nOld;                    /* Number of pages in apOld[] */
  int nNew;                    /* Number of pages in apNew[] */
  int nDiv;                    /* Number of cells in apDiv[] */
  int i, j, k;                 /* Loop counters */
  int idx;                     /* Index of pPage in pParent->aCell[] */
  int nxDiv;                   /* Next divider slot in pParent->aCell[] */
  int rc;                      /* The return code */

  int leafCorrection;          /* 4 if pPage is a leaf.  0 if not */
  int usableSpace;             /* Bytes in pPage beyond the header */
  int pageFlags;               /* Value of pPage->aData[0] */

  int subtotal;                /* Subtotal of bytes in cells on one page */
  MemPage *apOld[NB];          /* pPage and up to two siblings */
  Pgno pgnoOld[NB];            /* Page numbers for each page in apOld[] */
  MemPage *apCopy[NB];         /* Private copies of apOld[] pages */
  MemPage *apNew[NB+1];        /* pPage and up to NB siblings after balancing */
  Pgno pgnoNew[NB+1];          /* Page numbers for each page in apNew[] */
  int idxDiv[NB];              /* Indices of divider cells in pParent */
  u8 *apDiv[NB];               /* Divider cells in pParent */
  u8 aTemp[NB][MX_CELL_SIZE];  /* Temporary holding area for apDiv[] */
  int cntNew[NB+1];            /* Index in aCell[] of cell after i-th page */
  int szNew[NB+1];             /* Combined size of cells place on i-th page */
  u8 *apCell[(MX_CELL+2)*NB];  /* All cells from pages being balanced */
  int szCell[(MX_CELL+2)*NB];  /* Local size of all cells */
  u8 aCopy[NB][MX_PAGE_SIZE+sizeof(MemPage)];  /* Space for apCopy[] */

  /* 
  ** Return without doing any work if pPage is neither overfull nor
  ** underfull.
  */
  assert( sqlite3pager_iswriteable(pPage->aData) );
  pBt = pPage->pBt;
  if( !pPage->isOverfull && pPage->nFree<pBt->pageSize/2 && pPage->nCell>=2){
    relinkCellList(pPage);
    return SQLITE_OK;
  }

  /*

        ** its child (due to the 100 byte header that occurs at the beginning
        ** of the database fle), so it might not be able to hold all of the 
        ** information currently contained in the child.  If this is the 
        ** case, then do not do the transfer.  Leave page 1 empty except
        ** for the right-pointer to the child page.  The child page becomes
        ** the virtual root of the tree.
        */
        pgnoChild = get4byte(&pPage->aData[pPage->hdrOffset+6]);
        assert( pgnoChild>0 && pgnoChild<=sqlite3pager_pagecount(pBt->pPager) );
        rc = getPage(pBt, pgnoChild, &pChild);
        if( rc ) return rc;
        if( pPage->pgno==1 ){
          rc = initPage(pChild, pPage);
          if( rc ) return rc;
          if( pChild->nFree>=100 ){
            /* The child information will fit on the root page, so do the

          pPage->pParent = 0;
          rc = initPage(pPage, 0);
          assert( rc==SQLITE_OK );
          freePage(pChild);
        }
        reparentChildPages(pPage);
        releasePage(pChild);


      }
      return SQLITE_OK;
    }
    if( !pPage->isOverfull ){
      /* It is OK for the root page to be less than half full.
      */
      relinkCellList(pPage);
      return SQLITE_OK;
    }
    /*
    ** If we get to here, it means the root page is overfull.
    ** When this happens, Create a new child page and copy the
    ** contents of the root into the child.  Then make the root
    ** page an empty page with rightChild pointing to the new
    ** child.  Then fall thru to the code below which will cause
    ** the overfull child page to be split.
    */
    rc = allocatePage(pBt, &pChild, &pgnoChild, pPage->pgno);
    if( rc ) return rc;
    assert( sqlite3pager_iswriteable(pChild->aData) );
    copyPage(pChild, pPage);
    pChild->pParent = pPage;
    pChild->idxParent = 0;
    sqlite3pager_ref(pPage->aData);
    pChild->isOverfull = 1;
    zeroPage(pPage, pPage->aData[pPage->hdrOffset] & ~PTF_LEAF);
    put4byte(&pPage->aData[pPage->hdrOffset+6], pChild->pgno);
    pParent = pPage;
    pPage = pChild;
  }
  rc = sqlite3pager_write(pParent->aData);
  if( rc ) return rc;
  assert( pParent->isInit );
  
  /*
  ** Find the cell in the parent page whose left child points back
  ** to pPage.  The "idx" variable is the index of that cell.  If pPage
  ** is the rightmost child of pParent then set idx to pParent->nCell 
  */
  if( pParent->idxShift ){
    Pgno pgno;
    pgno = pPage->pgno;
    assert( pgno==sqlite3pager_pagenumber(pPage->aData) );
    for(idx=0; idx<pParent->nCell; idx++){
      if( get4byte(&pParent->aCell[idx][2])==pgno ){
        break;
      }
    }
    assert( idx<pParent->nCell
             || get4byte(&pParent->aData[pParent->hdrOffset+6])==pgno );
  }else{
    idx = pPage->idxParent;
  }

  /*
  ** Initialize variables so that it will be safe to jump
  ** directly to balance_cleanup at any moment.
  */
  nOld = nNew = 0;
  sqlite3pager_ref(pParent->aData);

  /*
  ** Find sibling pages to pPage and the cells in pParent that divide
  ** the siblings.  An attempt is made to find NN siblings on either
  ** side of pPage.  More siblings are taken from one side, however, if
  ** pPage there are fewer than NN siblings on the other side.  If pParent
  ** has NB or fewer children then all children of pParent are taken.

  }
  nDiv = 0;
  for(i=0, k=nxDiv; i<NB; i++, k++){
    if( k<pParent->nCell ){
      idxDiv[i] = k;
      apDiv[i] = pParent->aCell[k];
      nDiv++;
      assert( !pParent->leaf );
      pgnoOld[i] = get4byte(&apDiv[i][2]);
    }else if( k==pParent->nCell ){
      pgnoOld[i] = get4byte(&pParent->aData[pParent->hdrOffset+6]);
    }else{
      break;
    }
    rc = getPage(pBt, pgnoOld[i], &apOld[i]);
    if( rc ) goto balance_cleanup;

  assert( pPage->pgno>1 );
  pageFlags = pPage->aData[0];
  for(i=0; i<k; i++){
    if( i<nOld ){
      apNew[i] = apOld[i];
      pgnoNew[i] = pgnoOld[i];
      apOld[i] = 0;
      sqlite3pager_write(apNew[i]);
    }else{
      rc = allocatePage(pBt, &apNew[i], &pgnoNew[i], pgnoNew[i-1]);
      if( rc ) goto balance_cleanup;
    }
    nNew++;
    zeroPage(apNew[i], pageFlags);
    apNew[i]->isInit = 1;
  }

  /* Free any old pages that were not reused as new pages.
  */
  while( i<nOld ){
    rc = freePage(apOld[i]);
    if( rc ) goto balance_cleanup;
    sqlite3pager_unref(apOld[i]->aData);
    apOld[i] = 0;
    i++;
  }

  /*
  ** Put the new pages in accending order.  This helps to
  ** keep entries in the disk file in order so that a scan

  j = 0;
  for(i=0; i<nNew; i++){
    MemPage *pNew = apNew[i];
    assert( pNew->pgno==pgnoNew[i] );
    resizeCellArray(pNew, cntNew[i] - j);
    while( j<cntNew[i] ){
      assert( pNew->nFree>=szCell[j] );
      insertCell(pNew, pNew->nCell, apCell[j], szCell[j]);
      j++;
    }
    assert( pNew->nCell>0 );
    assert( !pNew->isOverfull );
    relinkCellList(pNew);
    if( i<nNew-1 && j<nCell ){
      u8 *pCell = apCell[j];

  }
  if( nxDiv==pParent->nCell ){
    /* Right-most sibling is the right-most child of pParent */
    put4byte(&pParent->aData[pParent->hdrOffset+6], pgnoNew[nNew-1]);
  }else{
    /* Right-most sibling is the left child of the first entry in pParent
    ** past the right-most divider entry */
    put4byte(&pParent->aCell[nxDiv][2], pgnoNew[nNew-1]);
  }

  /*
  ** Reparent children of all cells.
  */
  for(i=0; i<nNew; i++){
    reparentChildPages(apNew[i]);

*/
static int checkReadLocks(BtCursor *pCur){
  BtCursor *p;
  assert( pCur->wrFlag );
  for(p=pCur->pShared; p!=pCur; p=p->pShared){
    assert( p );
    assert( p->pgnoRoot==pCur->pgnoRoot );
    assert( p->pPage->pgno==sqlite3pager_pagenumber(p->pPage->aData) );
    if( p->wrFlag==0 ) return SQLITE_LOCKED;
    if( p->pPage->pgno!=p->pgnoRoot ){
      moveToRoot(p);
    }
  }
  return SQLITE_OK;
}

  const void *pData, int nData   /* The data of the new record */
){
  int rc;
  int loc;
  int szNew;
  MemPage *pPage;
  Btree *pBt = pCur->pBt;
  unsigned char *oldCell;
  unsigned char newCell[MX_CELL_SIZE];

  if( pCur->pPage==0 ){
    return SQLITE_ABORT;  /* A rollback destroyed this cursor */
  }
  if( !pBt->inTrans || nKey+nData==0 ){
    /* Must start a transaction before doing an insert */
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  assert( !pBt->readOnly );
  if( !pCur->wrFlag ){
    return SQLITE_PERM;   /* Cursor not open for writing */
  }
  if( checkReadLocks(pCur) ){
    return SQLITE_LOCKED; /* The table pCur points to has a read lock */
  }
  rc = sqlite3BtreeMoveto(pCur, pKey, nKey, &loc);
  if( rc ) return rc;
  pPage = pCur->pPage;
  assert( pPage->isInit );
  rc = sqlite3pager_write(pPage->aData);
  if( rc ) return rc;
  rc = fillInCell(pPage, newCell, pKey, nKey, pData, nData, &szNew);
  if( rc ) return rc;
  assert( szNew==cellSize(pPage, newCell) );
  if( loc==0 ){
    int szOld;
    assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
    oldCell = pPage->aCell[pCur->idx];
    if( !pPage->leaf ){
      memcpy(&newCell[2], &oldCell[2], 4);
    }
    szOld = cellSize(pPage, oldCell);
    rc = clearCell(pPage, oldCell);
    if( rc ) return rc;
    dropCell(pPage, pCur->idx, szOld);
  }else if( loc<0 && pPage->nCell>0 ){
    assert( pPage->leaf );
    pCur->idx++;
  }else{
    assert( pPage->leaf );
  }
  insertCell(pPage, pCur->idx, newCell, szNew);
  rc = balance(pPage);
  /* sqlite3BtreePageDump(pCur->pBt, pCur->pgnoRoot, 1); */
  /* fflush(stdout); */
  moveToRoot(pCur);
  pCur->eSkip = SKIP_INVALID;
  return rc;
}

  }
  if( !pCur->wrFlag ){
    return SQLITE_PERM;   /* Did not open this cursor for writing */
  }
  if( checkReadLocks(pCur) ){
    return SQLITE_LOCKED; /* The table pCur points to has a read lock */
  }
  rc = sqlite3pager_write(pPage->aData);
  if( rc ) return rc;
  pCell = pPage->aCell[pCur->idx];
  if( !pPage->leaf ){
    pgnoChild = get4byte(&pCell[2]);
  }
  clearCell(pPage, pCell);
  if( !pPage->leaf ){

    int notUsed;
    getTempCursor(pCur, &leafCur);
    rc = sqlite3BtreeNext(&leafCur, &notUsed);
    if( rc!=SQLITE_OK ){
      if( rc!=SQLITE_NOMEM ) rc = SQLITE_CORRUPT;
      return rc;
    }
    rc = sqlite3pager_write(leafCur.pPage->aData);
    if( rc ) return rc;
    dropCell(pPage, pCur->idx, cellSize(pPage, pCell));
    pNext = leafCur.pPage->aCell[leafCur.idx];
    szNext = cellSize(leafCur.pPage, pNext);
    insertCell(pPage, pCur->idx, &pNext[-4], szNext+4);
    put4byte(&pNext[-2], pgnoChild);
    rc = balance(pPage);

    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  if( pBt->readOnly ){
    return SQLITE_READONLY;
  }
  rc = allocatePage(pBt, &pRoot, &pgnoRoot, 0);
  if( rc ) return rc;
  assert( sqlite3pager_iswriteable(pRoot->aData) );
  zeroPage(pRoot, flags);
  sqlite3pager_unref(pRoot->aData);
  *piTable = (int)pgnoRoot;
  return SQLITE_OK;
}

/*
** Erase the given database page and all its children.  Return
** the page to the freelist.

  MemPage *pPage;
  int rc;
  unsigned char *pCell;
  int i;

  rc = getPage(pBt, pgno, &pPage);
  if( rc ) return rc;
  rc = sqlite3pager_write(pPage->aData);
  if( rc ) return rc;
  rc = initPage(pPage, pParent);
  if( rc ) return rc;
  for(i=0; i<pPage->nCell; i++){
    pCell = pPage->aCell[i];
    if( !pPage->leaf ){
      rc = clearDatabasePage(pBt, get4byte(&pCell[2]), pPage->pParent, 1);
      if( rc ) return rc;
    }
    rc = clearCell(pPage, pCell);
    if( rc ) return rc;
  }
  if( !pPage->leaf ){
    rc = clearDatabasePage(pBt, get4byte(&pPage->aData[6]), pPage->pParent, 1);
    if( rc ) return rc;
  }
  if( freePageFlag ){
    rc = freePage(pPage);
  }else{
    zeroPage(pPage, pPage->aData[0]);
  }

  }
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->pgnoRoot==(Pgno)iTable ){
      if( pCur->wrFlag==0 ) return SQLITE_LOCKED;
      moveToRoot(pCur);
    }
  }
  rc = clearDatabasePage(pBt, (Pgno)iTable, 0, 0);
  if( rc ){
    sqlite3BtreeRollback(pBt);
  }
  return rc;
}

/*

    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->pgnoRoot==(Pgno)iTable ){
      return SQLITE_LOCKED;  /* Cannot drop a table that has a cursor */
    }
  }
  rc = getPage(pBt, (Pgno)iTable, &pPage);
  if( rc ) return rc;
  rc = sqlite3BtreeClearTable(pBt, iTable);
  if( rc ) return rc;
  if( iTable>1 ){
    rc = freePage(pPage);
  }else{
    zeroPage(pPage, PTF_INTKEY|PTF_LEAF );
  }
  releasePage(pPage);
  return rc;  
}


/*
** Read the meta-information out of a database file.  Meta[0]
** is the number of free pages currently in the database.  Meta[1]
** through meta[15] are available for use by higher layers.
*/
int sqlite3BtreeGetMeta(Btree *pBt, int idx, u32 *pMeta){
  int rc;

  unsigned char *pP1;

  assert( idx>=0 && idx<=15 );
  rc = sqlite3pager_get(pBt->pPager, 1, (void**)&pP1);
  if( rc ) return rc;
  *pMeta = get4byte(&pP1[36 + idx*4]);
  sqlite3pager_unref(pP1);
  return SQLITE_OK;
}

/*
** Write meta-information back into the database.  Meta[0] is
** read-only and may not be written.
*/
int sqlite3BtreeUpdateMeta(Btree *pBt, int idx, u32 iMeta){
  unsigned char *pP1;
  int rc;
  assert( idx>=1 && idx<=15 );
  if( !pBt->inTrans ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  rc = sqlite3pager_get(pBt->pPager, 1, (void**)&pP1);
  if( rc ) return rc;
  rc = sqlite3pager_write(pP1);
  if( rc ) return rc;
  put4byte(&pP1[36 + idx*4], iMeta);
  return SQLITE_OK;
}

/******************************************************************************
** The complete implementation of the BTree subsystem is above this line.

  int hdrOffset;
  char range[20];
  unsigned char payload[20];
  rc = getPage(pBt, (Pgno)pgno, &pPage);
  if( rc ){
    return rc;
  }
  printf("PAGE %d:  flags=0x%02x  frag=%d\n", pgno,
    pPage->aData[pPage->hdrOffset], pPage->aData[pPage->hdrOffset+5]);
  i = 0;
  hdrOffset = pgno==1 ? 100 : 0;
  idx = get2byte(&pPage->aData[hdrOffset+3]);
  while( idx>0 && idx<=pBt->pageSize ){
    u64 nData, nKey;
    int nHeader;
    Pgno child;
    unsigned char *pCell = &pPage->aData[idx];
    int sz = cellSize(pPage, pCell);
    sprintf(range,"%d..%d", idx, idx+sz-1);
    parseCellHeader(pPage, pCell, &nData, &nKey, &nHeader);
    if( pPage->leaf ){
      child = 0;
    }else{
      child = get4byte(&pCell[2]);
    }
    sz = nData;
    if( !pPage->intKey ) sz += nKey;
    if( sz>sizeof(payload)-1 ) sz = sizeof(payload)-1;
    memcpy(payload, &pCell[nHeader], sz);
    for(j=0; j<sz; j++){
      if( payload[j]<0x20 || payload[j]>0x7f ) payload[j] = '.';
    }
    payload[sz] = 0;
    printf(
      "cell %2d: i=%-10s chld=%-4d nk=%-4lld nd=%-4lld payload=%s\n",
      i, range, child, nKey, nData, payload
    );
    if( pPage->isInit && pPage->aCell[i]!=pCell ){
      printf("**** aCell[%d] does not match on prior entry ****\n", i);
    }
    i++;
    idx = get2byte(pCell);
  }

       i, range, sz, nFree);
    idx = get2byte(&pPage->aData[idx]);
    i++;
  }
  if( idx!=0 ){
    printf("ERROR: next freeblock index out of range: %d\n", idx);
  }
  if( recursive && !pPage->leaf ){
    idx = get2byte(&pPage->aData[hdrOffset+3]);
    while( idx>0 && idx<pBt->pageSize ){
      unsigned char *pCell = &pPage->aData[idx];
      sqlite3BtreePageDump(pBt, get4byte(&pCell[2]), 1);
      idx = get2byte(pCell);
    }
    sqlite3BtreePageDump(pBt, get4byte(&pPage->aData[hdrOffset+6]), 1);
  }
  sqlite3pager_unref(pPage->aData);
  return SQLITE_OK;
}
#endif

#ifdef SQLITE_TEST
/*
** Return the flag byte at the beginning of the page that the cursor
** is currently pointing to.
*/
int sqlite3BtreeFlags(BtCursor *pCur){
  return pCur->pPage->aData[pCur->pPage->hdrOffset];
}
#endif

#ifdef SQLITE_TEST
/*
** Fill aResult[] with information about the entry and page that the
** cursor is pointing to.
** 
**   aResult[0] =  The page number
**   aResult[1] =  The entry number
**   aResult[2] =  Total number of entries on this page
**   aResult[3] =  Size of this entry
**   aResult[4] =  Number of free bytes on this page
**   aResult[5] =  Number of free blocks on the page
**   aResult[6] =  Page number of the left child of this entry
**   aResult[7] =  Page number of the right child for the whole page
**
** This routine is used for testing and debugging only.
*/
int sqlite3BtreeCursorDump(BtCursor *pCur, int *aResult){
  int cnt, idx;
  MemPage *pPage = pCur->pPage;

  assert( pPage->isInit );
  aResult[0] = sqlite3pager_pagenumber(pPage->aData);
  assert( aResult[0]==pPage->pgno );
  aResult[1] = pCur->idx;
  aResult[2] = pPage->nCell;
  if( pCur->idx>=0 && pCur->idx<pPage->nCell ){
    aResult[3] = cellSize(pPage, pPage->aCell[pCur->idx]);
    aResult[6] = pPage->leaf ? 0 : get4byte(&pPage->aCell[pCur->idx][2]);
  }else{

    unsigned char *pOvfl;
    if( iPage<1 ){
      sprintf(zMsg, "%d pages missing from overflow list", N+1);
      checkAppendMsg(pCheck, zContext, zMsg);
      break;
    }
    if( checkRef(pCheck, iPage, zContext) ) break;
    if( sqlite3pager_get(pCheck->pPager, (Pgno)iPage, (void**)&pOvfl) ){
      sprintf(zMsg, "failed to get page %d", iPage);
      checkAppendMsg(pCheck, zContext, zMsg);
      break;
    }
    if( isFreeList ){
      int n = get4byte(&pOvfl[4]);
      for(i=0; i<n; i++){
        checkRef(pCheck, get4byte(&pOvfl[8+i*4]), zContext);
      }
      N -= n;
    }
    iPage = get4byte(pOvfl);
    sqlite3pager_unref(pOvfl);
  }
}

/*
** Return negative if zKey1<zKey2.
** Return zero if zKey1==zKey2.
** Return positive if zKey1>zKey2.

    zKey1[nLower] = 0;
  }else{
    zKey1 = 0;
  }
  nKey1 = nLower;
  cur.pPage = pPage;
  for(i=0; i<pPage->nCell; i++){
    Cell *pCell = pPage->aCell[i];
    int sz;

    /* Check payload overflow pages
    */
    nKey2 = NKEY(pBt, pCell->h);
    sz = nKey2 + NDATA(pBt, pCell->h);
    sprintf(zContext, "On page %d cell %d: ", iPage, i);

** is responsible for freeing the error message when it is done.
*/
char *sqlite3BtreeIntegrityCheck(Btree *pBt, int *aRoot, int nRoot){
  int i;
  int nRef;
  IntegrityCk sCheck;

  nRef = *sqlite3pager_stats(pBt->pPager);
  if( lockBtree(pBt)!=SQLITE_OK ){
    return sqliteStrDup("Unable to acquire a read lock on the database");
  }
  sCheck.pBt = pBt;
  sCheck.pPager = pBt->pPager;
  sCheck.nPage = sqlite3pager_pagecount(sCheck.pPager);
  if( sCheck.nPage==0 ){
    unlockBtreeIfUnused(pBt);
    return 0;
  }
  sCheck.anRef = sqliteMallocRaw( (sCheck.nPage+1)*sizeof(sCheck.anRef[0]) );
  sCheck.anRef[1] = 1;
  for(i=2; i<=sCheck.nPage; i++){ sCheck.anRef[i] = 0; }
  sCheck.zErrMsg = 0;

  /* Check the integrity of the freelist
  */
  checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
            get4byte(&pBt->pPage1->aData[36]), "Main freelist: ");

  /* Check all the tables.
  */
  for(i=0; i<nRoot; i++){
    if( aRoot[i]==0 ) continue;
    checkTreePage(&sCheck, aRoot[i], 0, "List of tree roots: ", 0,0,0,0);
  }

      checkAppendMsg(&sCheck, zBuf, 0);
    }
  }

  /* Make sure this analysis did not leave any unref() pages
  */
  unlockBtreeIfUnused(pBt);
  if( nRef != *sqlite3pager_stats(pBt->pPager) ){
    char zBuf[100];
    sprintf(zBuf, 
      "Outstanding page count goes from %d to %d during this analysis",
      nRef, *sqlite3pager_stats(pBt->pPager)
    );
    checkAppendMsg(&sCheck, zBuf, 0);
  }

  /* Clean  up and report errors.
  */
  sqliteFree(sCheck.anRef);
  return sCheck.zErrMsg;
}

/*
** Return the full pathname of the underlying database file.
*/
const char *sqlite3BtreeGetFilename(Btree *pBt){
  assert( pBt->pPager!=0 );
  return sqlite3pager_filename(pBt->pPager);
}

/*
** Copy the complete content of pBtFrom into pBtTo.  A transaction
** must be active for both files.
**
** The size of file pBtFrom may be reduced by this operation.
** If anything goes wrong, the transaction on pBtFrom is rolled back.
*/
int sqlite3BtreeCopyFile(Btree *pBtTo, Btree *pBtFrom){
  int rc = SQLITE_OK;
  Pgno i, nPage, nToPage;

  if( !pBtTo->inTrans || !pBtFrom->inTrans ) return SQLITE_ERROR;

  if( pBtTo->pCursor ) return SQLITE_BUSY;
  memcpy(pBtTo->pPage1, pBtFrom->pPage1, SQLITE_USABLE_SIZE);
  rc = sqlite3pager_overwrite(pBtTo->pPager, 1, pBtFrom->pPage1);
  nToPage = sqlite3pager_pagecount(pBtTo->pPager);
  nPage = sqlite3pager_pagecount(pBtFrom->pPager);
  for(i=2; rc==SQLITE_OK && i<=nPage; i++){
    void *pPage;
    rc = sqlite3pager_get(pBtFrom->pPager, i, &pPage);
    if( rc ) break;
    rc = sqlite3pager_overwrite(pBtTo->pPager, i, pPage);
    if( rc ) break;
    sqlite3pager_unref(pPage);
  }
  for(i=nPage+1; rc==SQLITE_OK && i<=nToPage; i++){
    void *pPage;
    rc = sqlite3pager_get(pBtTo->pPager, i, &pPage);
    if( rc ) break;
    rc = sqlite3pager_write(pPage);
    sqlite3pager_unref(pPage);
    sqlite3pager_dont_write(pBtTo->pPager, i);
  }
  if( !rc && nPage<nToPage ){
    rc = sqlite3pager_truncate(pBtTo->pPager, nPage);
  }
  if( rc ){
    sqlite3BtreeRollback(pBtTo);
  }
  return rc;  
}

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite B-Tree file
** subsystem.  See comments in the source code for a detailed description
** of what each interface routine does.
**
** @(#) $Id: btree.h,v 1.38 2004/05/07 13:30:42 drh Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/*
** Forward declarations of structure
*/

  int iTable,                          /* Index of root page */
  int wrFlag,                          /* 1 for writing.  0 for read-only */
  int(*)(void*,int,const void*,int,const void*),  /* Key comparison function */
  void*,                               /* First argument to compare function */
  BtCursor **ppCursor                  /* Returned cursor */
);

int sqlite3BtreeCloseCursor(BtCursor*);
int sqlite3BtreeMoveto(BtCursor*, const void *pKey, u64 nKey, int *pRes);
int sqlite3BtreeDelete(BtCursor*);
int sqlite3BtreeInsert(BtCursor*, const void *pKey, u64 nKey,
                                  const void *pData, int nData);
int sqlite3BtreeFirst(BtCursor*, int *pRes);
int sqlite3BtreeLast(BtCursor*, int *pRes);
int sqlite3BtreeNext(BtCursor*, int *pRes);
int sqlite3BtreePrevious(BtCursor*, int *pRes);
int sqlite3BtreeKeySize(BtCursor*, u64 *pSize);
int sqlite3BtreeKey(BtCursor*, u32 offset, u32 amt, void*);
void *sqlite3BtreeKeyFetch(BtCursor*);
int sqlite3BtreeDataSize(BtCursor*, u32 *pSize);
int sqlite3BtreeData(BtCursor*, u32 offset, u32 amt, void*);

char *sqlite3BtreeIntegrityCheck(Btree*, int *aRoot, int nRoot);
struct Pager *sqlite3BtreePager(Btree*);

#ifdef SQLITE_TEST
int sqlite3BtreeCursorDump(BtCursor*, int*);
int sqlite3BtreeFlags(BtCursor*);
int sqlite3BtreePageDump(Btree*, int, int recursive);
#endif


#endif /* _BTREE_H_ */

  int width;                 /* Width of the current field */
  etByte flag_leftjustify;   /* True if "-" flag is present */
  etByte flag_plussign;      /* True if "+" flag is present */
  etByte flag_blanksign;     /* True if " " flag is present */
  etByte flag_alternateform; /* True if "#" flag is present */
  etByte flag_zeropad;       /* True if field width constant starts with zero */
  etByte flag_long;          /* True if "l" flag is present */
  etByte flag_longlong;      /* True if the "ll" flag is present */
  UINT64_TYPE longvalue;     /* Value for integer types */
  LONGDOUBLE_TYPE realvalue; /* Value for real types */
  et_info *infop;            /* Pointer to the appropriate info structure */
  char buf[etBUFSIZE];       /* Conversion buffer */
  char prefix;               /* Prefix character.  "+" or "-" or " " or '\0'. */
  etByte errorflag = 0;      /* True if an error is encountered */
  etByte xtype;              /* Conversion paradigm */
  char *zExtra;              /* Extra memory used for etTCLESCAPE conversions */

    }else{
      precision = -1;
    }
    /* Get the conversion type modifier */
    if( c=='l' ){
      flag_long = 1;
      c = *++fmt;
      if( c=='l' ){
        flag_longlong = 1;
        c = *++fmt;
      }else{
        flag_longlong = 0;
      }
    }else{
      flag_long = flag_longlong = 0;
    }
    /* Fetch the info entry for the field */
    infop = 0;
    xtype = etERROR;
    for(idx=0; idx<etNINFO; idx++){
      if( c==fmtinfo[idx].fmttype ){
        infop = &fmtinfo[idx];

    **   flag_alternateform          TRUE if a '#' is present.
    **   flag_plussign               TRUE if a '+' is present.
    **   flag_leftjustify            TRUE if a '-' is present or if the
    **                               field width was negative.
    **   flag_zeropad                TRUE if the width began with 0.
    **   flag_long                   TRUE if the letter 'l' (ell) prefixed
    **                               the conversion character.
    **   flag_longlong               TRUE if the letter 'll' (ell ell) prefixed
    **                               the conversion character.
    **   flag_blanksign              TRUE if a ' ' is present.
    **   width                       The specified field width.  This is
    **                               always non-negative.  Zero is the default.
    **   precision                   The specified precision.  The default
    **                               is -1.
    **   xtype                       The class of the conversion.
    **   infop                       Pointer to the appropriate info struct.
    */
    switch( xtype ){
      case etRADIX:
        if( flag_longlong )   longvalue = va_arg(ap,INT64_TYPE);
        else if( flag_long )  longvalue = va_arg(ap,long ing);
        else                  longvalue = va_arg(ap,int);
#if 1
        /* For the format %#x, the value zero is printed "0" not "0x0".
        ** I think this is stupid. */
        if( longvalue==0 ) flag_alternateform = 0;
#else
        /* More sensible: turn off the prefix for octal (to prevent "00"),
        ** but leave the prefix for hex. */

/*
** 2001 September 15
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.223 2004/05/07 13:30:42 drh Exp $
*/
#include "config.h"
#include "sqlite.h"
#include "hash.h"
#include "parse.h"
#include <stdio.h>
#include <stdlib.h>

/*
** Integers of known sizes.  These typedefs might change for architectures
** where the sizes very.  Preprocessor macros are available so that the
** types can be conveniently redefined at compile-type.  Like this:
**
**         cc '-DUINTPTR_TYPE=long long int' ...
*/
#ifndef INT64_TYPE
# define INT64_TYPE long long int
#endif
#ifndef UINT64_TYPE
# define UINT64_TYPE unsigned long long int
#endif
#ifndef UINT32_TYPE
# define UINT32_TYPE unsigned int
#endif
#ifndef UINT16_TYPE

int sqliteFitsIn32Bits(const char *);

unsigned char *sqlite3utf16to8(const void *pData, int N);
void *sqlite3utf8to16be(const unsigned char *pIn, int N);
void *sqlite3utf8to16le(const unsigned char *pIn, int N);
void sqlite3utf16to16le(void *pData, int N);
void sqlite3utf16to16be(void *pData, int N);

**    May you share freely, never taking more than you give.
**
*************************************************************************
** 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 1.26 2004/05/07 13:30:42 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

  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;
  a = sqlite3pager_stats(sqlite3BtreePager(pBt));
  for(i=0; i<9; i++){
    static char *zName[] = {
      "ref", "page", "max", "size", "state", "err",
      "hit", "miss", "ovfl",
    };
    char zBuf[100];
    Tcl_AppendElement(interp, zName[i]);

  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;
  sqlite3pager_refdump(sqlite3BtreePager(pBt));
  return TCL_OK;
}

/*
** Usage:   btree_integrity_check ID ROOT ...
**
** Look through every page of the given BTree file to verify correct

    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID TABLENUM WRITEABLE\"", 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;
  if( Tcl_GetBoolean(interp, argv[3], &wrFlag) ) return TCL_ERROR;
  rc = sqlite3BtreeCursor(pBt, iTable, wrFlag, 0, 0, &pCur);
  if( rc ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sprintf(zBuf,"0x%x", (int)pCur);
  Tcl_AppendResult(interp, zBuf, 0);
  return SQLITE_OK;

static int btree_keysize(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  BtCursor *pCur;

  u64 n;

  char zBuf[50];

  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pCur) ) return TCL_ERROR;
  sqlite3BtreeKeySize(pCur, &n);

  sprintf(zBuf, "%llu", n);
  Tcl_AppendResult(interp, zBuf, 0);
  return SQLITE_OK;
}

/*
** Usage:   btree_key ID
**

  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pCur) ) return TCL_ERROR;
  sqlite3BtreeKeySize(pCur, &n);
  if( sqlite3BtreeFlags(pCur) & BTREE_INTKEY ){
    char zBuf2[60];
    sprintf(zBuf2, "%llu", n);
    Tcl_AppendResult(interp, zBuf2, 0);
  }else{
    zBuf = malloc( n+1 );
    rc = sqlite3BtreeKey(pCur, 0, n, zBuf);
    if( rc!=n ){
      char zMsg[100];
      free(zBuf);
      sprintf(zMsg, "truncated key: got %d of %llu bytes", rc, n);
      Tcl_AppendResult(interp, zMsg, 0);
      return TCL_ERROR;
    }
    zBuf[n] = 0;
    Tcl_AppendResult(interp, zBuf, 0);
    free(zBuf);
  }
  return SQLITE_OK;
}

/*
** Usage:   btree_data ID
**
** Return the data for the entry at which the cursor is pointing.
*/
static int btree_data(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  BtCursor *pCur;
  int rc;
  u32 n;
  char *zBuf;

  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pCur) ) return TCL_ERROR;
  sqlite3BtreeDataSize(pCur, &n);
  zBuf = malloc( n+1 );
  rc = sqlite3BtreeData(pCur, 0, n, zBuf);
  if( rc!=n ){
    char zMsg[100];
    free(zBuf);
    sprintf(zMsg, "truncated data: got %d of %u bytes", rc, n);
    Tcl_AppendResult(interp, zMsg, 0);
    return TCL_ERROR;
  }
  zBuf[n] = 0;
  Tcl_AppendResult(interp, zBuf, 0);
  free(zBuf);
  return SQLITE_OK;

  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  BtCursor *pCur;
  int n2;
  u64 n1;
  char zBuf[50];

  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pCur) ) return TCL_ERROR;
  if( sqlite3BtreeFlags(pCur) & BTREE_INTKEY ){
    n1 = 0;
  }else{
    sqlite3BtreeKeySize(pCur, &n1);
  }
  sqlite3BtreeDataSize(pCur, &n2);
  sprintf(zBuf, "%d", (int)(n1+n2));
  Tcl_AppendResult(interp, zBuf, 0);
  return SQLITE_OK;
}

/*
** Usage:   btree_cursor_dump ID
**

     { "btree_cursor",             (Tcl_CmdProc*)btree_cursor             },
     { "btree_close_cursor",       (Tcl_CmdProc*)btree_close_cursor       },
     { "btree_move_to",            (Tcl_CmdProc*)btree_move_to            },
     { "btree_delete",             (Tcl_CmdProc*)btree_delete             },
     { "btree_insert",             (Tcl_CmdProc*)btree_insert             },
     { "btree_next",               (Tcl_CmdProc*)btree_next               },
     { "btree_prev",               (Tcl_CmdProc*)btree_prev               },
     { "btree_keysize",            (Tcl_CmdProc*)btree_keysize            },
     { "btree_key",                (Tcl_CmdProc*)btree_key                },
     { "btree_data",               (Tcl_CmdProc*)btree_data               },
     { "btree_payload_size",       (Tcl_CmdProc*)btree_payload_size       },
     { "btree_first",              (Tcl_CmdProc*)btree_first              },
     { "btree_last",               (Tcl_CmdProc*)btree_last               },
     { "btree_cursor_dump",        (Tcl_CmdProc*)btree_cursor_dump        },
     { "btree_integrity_check",    (Tcl_CmdProc*)btree_integrity_check    },
  };
  int i;

  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
  }
  Tcl_LinkVar(interp, "pager_refinfo_enable", (char*)&pager3_refinfo_enable,
     TCL_LINK_INT);
  return TCL_OK;
}