#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Append a message to the error message string.
*/
static void checkAppendMsg(
  IntegrityCk *pCheck,
  char *zMsg1,
  const char *zFormat,
  ...
){
  va_list ap;

  if( !pCheck->mxErr ) return;
  pCheck->mxErr--;
  pCheck->nErr++;
  va_start(ap, zFormat);
  if( pCheck->errMsg.nChar ){
    sqlite3StrAccumAppend(&pCheck->errMsg, "\n", 1);
  }
  if( zMsg1 ){

    sqlite3StrAccumAppendAll(&pCheck->errMsg, zMsg1);
  }
  sqlite3VXPrintf(&pCheck->errMsg, 1, zFormat, ap);
  va_end(ap);
  if( pCheck->errMsg.accError==STRACCUM_NOMEM ){
    pCheck->mallocFailed = 1;
  }
}
................................................................................
** Add 1 to the reference count for page iPage.  If this is the second
** reference to the page, add an error message to pCheck->zErrMsg.
** Return 1 if there are 2 or more references to the page and 0 if
** if this is the first reference to the page.
**
** Also check that the page number is in bounds.
*/
static int checkRef(IntegrityCk *pCheck, Pgno iPage, char *zContext){
  if( iPage==0 ) return 1;
  if( iPage>pCheck->nPage ){
    checkAppendMsg(pCheck, zContext, "invalid page number %d", iPage);
    return 1;
  }
  if( getPageReferenced(pCheck, iPage) ){
    checkAppendMsg(pCheck, zContext, "2nd reference to page %d", iPage);
    return 1;
  }
  setPageReferenced(pCheck, iPage);
  return 0;
}

#ifndef SQLITE_OMIT_AUTOVACUUM
................................................................................
** page iParent, pointer type ptrType. If not, append an error message
** to pCheck.
*/
static void checkPtrmap(
  IntegrityCk *pCheck,   /* Integrity check context */
  Pgno iChild,           /* Child page number */
  u8 eType,              /* Expected pointer map type */
  Pgno iParent,          /* Expected pointer map parent page number */
  char *zContext         /* Context description (used for error msg) */
){
  int rc;
  u8 ePtrmapType;
  Pgno iPtrmapParent;

  rc = ptrmapGet(pCheck->pBt, iChild, &ePtrmapType, &iPtrmapParent);
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ) pCheck->mallocFailed = 1;
    checkAppendMsg(pCheck, zContext, "Failed to read ptrmap key=%d", iChild);
    return;
  }

  if( ePtrmapType!=eType || iPtrmapParent!=iParent ){
    checkAppendMsg(pCheck, zContext, 
      "Bad ptr map entry key=%d expected=(%d,%d) got=(%d,%d)", 
      iChild, eType, iParent, ePtrmapType, iPtrmapParent);
  }
}
#endif

/*
................................................................................
** Check the integrity of the freelist or of an overflow page list.
** Verify that the number of pages on the list is N.
*/
static void checkList(
  IntegrityCk *pCheck,  /* Integrity checking context */
  int isFreeList,       /* True for a freelist.  False for overflow page list */
  int iPage,            /* Page number for first page in the list */
  int N,                /* Expected number of pages in the list */
  char *zContext        /* Context for error messages */
){
  int i;
  int expected = N;
  int iFirst = iPage;
  while( N-- > 0 && pCheck->mxErr ){
    DbPage *pOvflPage;
    unsigned char *pOvflData;
    if( iPage<1 ){
      checkAppendMsg(pCheck, zContext,
         "%d of %d pages missing from overflow list starting at %d",
          N+1, expected, iFirst);
      break;
    }
    if( checkRef(pCheck, iPage, zContext) ) break;
    if( sqlite3PagerGet(pCheck->pPager, (Pgno)iPage, &pOvflPage) ){
      checkAppendMsg(pCheck, zContext, "failed to get page %d", iPage);
      break;
    }
    pOvflData = (unsigned char *)sqlite3PagerGetData(pOvflPage);
    if( isFreeList ){
      int n = get4byte(&pOvflData[4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
      if( pCheck->pBt->autoVacuum ){
        checkPtrmap(pCheck, iPage, PTRMAP_FREEPAGE, 0, zContext);
      }
#endif
      if( n>(int)pCheck->pBt->usableSize/4-2 ){
        checkAppendMsg(pCheck, zContext,
           "freelist leaf count too big on page %d", iPage);
        N--;
      }else{
        for(i=0; i<n; i++){
          Pgno iFreePage = get4byte(&pOvflData[8+i*4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
          if( pCheck->pBt->autoVacuum ){
            checkPtrmap(pCheck, iFreePage, PTRMAP_FREEPAGE, 0, zContext);
          }
#endif
          checkRef(pCheck, iFreePage, zContext);
        }
        N -= n;
      }
    }
#ifndef SQLITE_OMIT_AUTOVACUUM
    else{
      /* If this database supports auto-vacuum and iPage is not the last
      ** page in this overflow list, check that the pointer-map entry for
      ** the following page matches iPage.
      */
      if( pCheck->pBt->autoVacuum && N>0 ){
        i = get4byte(pOvflData);
        checkPtrmap(pCheck, i, PTRMAP_OVERFLOW2, iPage, zContext);
      }
    }
#endif
    iPage = get4byte(pOvflData);
    sqlite3PagerUnref(pOvflPage);
  }
}
................................................................................
**      7.  Verify that the depth of all children is the same.
**      8.  Make sure this page is at least 33% full or else it is
**          the root of the tree.
*/
static int checkTreePage(
  IntegrityCk *pCheck,  /* Context for the sanity check */
  int iPage,            /* Page number of the page to check */
  char *zParentContext, /* Parent context */
  i64 *pnParentMinKey, 
  i64 *pnParentMaxKey
){
  MemPage *pPage;
  int i, rc, depth, d2, pgno, cnt;
  int hdr, cellStart;
  int nCell;
  u8 *data;
  BtShared *pBt;
  int usableSize;
  char zContext[100];
  char *hit = 0;
  i64 nMinKey = 0;
  i64 nMaxKey = 0;

  sqlite3_snprintf(sizeof(zContext), zContext, "Page %d: ", iPage);


  /* Check that the page exists
  */
  pBt = pCheck->pBt;
  usableSize = pBt->usableSize;
  if( iPage==0 ) return 0;
  if( checkRef(pCheck, iPage, zParentContext) ) return 0;


  if( (rc = btreeGetPage(pBt, (Pgno)iPage, &pPage, 0))!=0 ){
    checkAppendMsg(pCheck, zContext,
       "unable to get the page. error code=%d", rc);
    return 0;


  }

  /* Clear MemPage.isInit to make sure the corruption detection code in
  ** btreeInitPage() is executed.  */
  pPage->isInit = 0;
  if( (rc = btreeInitPage(pPage))!=0 ){
    assert( rc==SQLITE_CORRUPT );  /* The only possible error from InitPage */
    checkAppendMsg(pCheck, zContext, 
                   "btreeInitPage() returns error code %d", rc);
    releasePage(pPage);
    return 0;

  }

  /* Check out all the cells.
  */
  depth = 0;
  for(i=0; i<pPage->nCell && pCheck->mxErr; i++){
    u8 *pCell;
    u32 sz;
    CellInfo info;

    /* Check payload overflow pages
    */
    sqlite3_snprintf(sizeof(zContext), zContext,
             "On tree page %d cell %d: ", iPage, i);

    pCell = findCell(pPage,i);
    btreeParseCellPtr(pPage, pCell, &info);
    sz = info.nPayload;
    /* For intKey pages, check that the keys are in order.
    */
    if( pPage->intKey ){
      if( i==0 ){
        nMinKey = nMaxKey = info.nKey;
      }else if( info.nKey <= nMaxKey ){
        checkAppendMsg(pCheck, zContext, 
           "Rowid %lld out of order (previous was %lld)", info.nKey, nMaxKey);
      }
      nMaxKey = info.nKey;
    }
    if( (sz>info.nLocal) 
     && (&pCell[info.iOverflow]<=&pPage->aData[pBt->usableSize])
    ){
      int nPage = (sz - info.nLocal + usableSize - 5)/(usableSize - 4);
      Pgno pgnoOvfl = get4byte(&pCell[info.iOverflow]);
#ifndef SQLITE_OMIT_AUTOVACUUM
      if( pBt->autoVacuum ){
        checkPtrmap(pCheck, pgnoOvfl, PTRMAP_OVERFLOW1, iPage, zContext);
      }
#endif
      checkList(pCheck, 0, pgnoOvfl, nPage, zContext);
    }

    /* Check sanity of left child page.
    */
    if( !pPage->leaf ){
      pgno = get4byte(pCell);
#ifndef SQLITE_OMIT_AUTOVACUUM
      if( pBt->autoVacuum ){
        checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage, zContext);
      }
#endif
      d2 = checkTreePage(pCheck, pgno, zContext, &nMinKey, i==0?NULL:&nMaxKey);
      if( i>0 && d2!=depth ){
        checkAppendMsg(pCheck, zContext, "Child page depth differs");
      }
      depth = d2;
    }
  }

  if( !pPage->leaf ){
    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
    sqlite3_snprintf(sizeof(zContext), zContext, 
                     "On page %d at right child: ", iPage);

#ifndef SQLITE_OMIT_AUTOVACUUM
    if( pBt->autoVacuum ){
      checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage, zContext);
    }
#endif
    checkTreePage(pCheck, pgno, zContext, NULL, !pPage->nCell?NULL:&nMaxKey);
  }
 
  /* For intKey leaf pages, check that the min/max keys are in order
  ** with any left/parent/right pages.
  */


  if( pPage->leaf && pPage->intKey ){
    /* if we are a left child page */
    if( pnParentMinKey ){
      /* if we are the left most child page */
      if( !pnParentMaxKey ){
        if( nMaxKey > *pnParentMinKey ){
          checkAppendMsg(pCheck, zContext, 
              "Rowid %lld out of order (max larger than parent min of %lld)",
              nMaxKey, *pnParentMinKey);
        }
      }else{
        if( nMinKey <= *pnParentMinKey ){
          checkAppendMsg(pCheck, zContext, 
              "Rowid %lld out of order (min less than parent min of %lld)",
              nMinKey, *pnParentMinKey);
        }
        if( nMaxKey > *pnParentMaxKey ){
          checkAppendMsg(pCheck, zContext, 
              "Rowid %lld out of order (max larger than parent max of %lld)",
              nMaxKey, *pnParentMaxKey);
        }
        *pnParentMinKey = nMaxKey;
      }
    /* else if we're a right child page */
    } else if( pnParentMaxKey ){
      if( nMinKey <= *pnParentMaxKey ){
        checkAppendMsg(pCheck, zContext, 
            "Rowid %lld out of order (min less than parent max of %lld)",
            nMinKey, *pnParentMaxKey);
      }
    }
  }

  /* Check for complete coverage of the page
  */
  data = pPage->aData;
  hdr = pPage->hdrOffset;
  hit = sqlite3PageMalloc( pBt->pageSize );

  if( hit==0 ){
    pCheck->mallocFailed = 1;
  }else{
    int contentOffset = get2byteNotZero(&data[hdr+5]);
    assert( contentOffset<=usableSize );  /* Enforced by btreeInitPage() */
    memset(hit+contentOffset, 0, usableSize-contentOffset);
    memset(hit, 1, contentOffset);
................................................................................
      int pc = get2byte(&data[cellStart+i*2]);
      u32 size = 65536;
      int j;
      if( pc<=usableSize-4 ){
        size = cellSizePtr(pPage, &data[pc]);
      }
      if( (int)(pc+size-1)>=usableSize ){

        checkAppendMsg(pCheck, 0, 
            "Corruption detected in cell %d on page %d",i,iPage);
      }else{
        for(j=pc+size-1; j>=pc; j--) hit[j]++;
      }
    }
    i = get2byte(&data[hdr+1]);
    while( i>0 ){
................................................................................
      assert( j<=usableSize-4 );   /* Enforced by btreeInitPage() */
      i = j;
    }
    for(i=cnt=0; i<usableSize; i++){
      if( hit[i]==0 ){
        cnt++;
      }else if( hit[i]>1 ){
        checkAppendMsg(pCheck, 0,
          "Multiple uses for byte %d of page %d", i, iPage);
        break;
      }
    }
    if( cnt!=data[hdr+7] ){
      checkAppendMsg(pCheck, 0, 
          "Fragmentation of %d bytes reported as %d on page %d",
          cnt, data[hdr+7], iPage);
    }
  }
  sqlite3PageFree(hit);
  releasePage(pPage);





  return depth+1;
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */

#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** This routine does a complete check of the given BTree file.  aRoot[] is
................................................................................
  nRef = sqlite3PagerRefcount(pBt->pPager);
  sCheck.pBt = pBt;
  sCheck.pPager = pBt->pPager;
  sCheck.nPage = btreePagecount(sCheck.pBt);
  sCheck.mxErr = mxErr;
  sCheck.nErr = 0;
  sCheck.mallocFailed = 0;



  *pnErr = 0;
  if( sCheck.nPage==0 ){
    sqlite3BtreeLeave(p);
    return 0;
  }

  sCheck.aPgRef = sqlite3MallocZero((sCheck.nPage / 8)+ 1);
................................................................................
  i = PENDING_BYTE_PAGE(pBt);
  if( i<=sCheck.nPage ) setPageReferenced(&sCheck, i);
  sqlite3StrAccumInit(&sCheck.errMsg, zErr, sizeof(zErr), SQLITE_MAX_LENGTH);
  sCheck.errMsg.useMalloc = 2;

  /* 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; (int)i<nRoot && sCheck.mxErr; i++){
    if( aRoot[i]==0 ) continue;
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( pBt->autoVacuum && aRoot[i]>1 ){
      checkPtrmap(&sCheck, aRoot[i], PTRMAP_ROOTPAGE, 0, 0);
    }
#endif

    checkTreePage(&sCheck, aRoot[i], "List of tree roots: ", NULL, NULL);

  }

  /* Make sure every page in the file is referenced
  */
  for(i=1; i<=sCheck.nPage && sCheck.mxErr; i++){
#ifdef SQLITE_OMIT_AUTOVACUUM
    if( getPageReferenced(&sCheck, i)==0 ){
      checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
    }
#else
    /* If the database supports auto-vacuum, make sure no tables contain
    ** references to pointer-map pages.
    */
    if( getPageReferenced(&sCheck, i)==0 && 
       (PTRMAP_PAGENO(pBt, i)!=i || !pBt->autoVacuum) ){
      checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
    }
    if( getPageReferenced(&sCheck, i)!=0 && 
       (PTRMAP_PAGENO(pBt, i)==i && pBt->autoVacuum) ){
      checkAppendMsg(&sCheck, 0, "Pointer map page %d is referenced", i);
    }
#endif
  }

  /* Make sure this analysis did not leave any unref() pages.
  ** This is an internal consistency check; an integrity check
  ** of the integrity check.
  */
  if( NEVER(nRef != sqlite3PagerRefcount(pBt->pPager)) ){
    checkAppendMsg(&sCheck, 0, 
      "Outstanding page count goes from %d to %d during this analysis",
      nRef, sqlite3PagerRefcount(pBt->pPager)
    );
  }

  /* Clean  up and report errors.
  */

#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Append a message to the error message string.
*/
static void checkAppendMsg(
  IntegrityCk *pCheck,

  const char *zFormat,
  ...
){
  va_list ap;
  char zBuf[200];
  if( !pCheck->mxErr ) return;
  pCheck->mxErr--;
  pCheck->nErr++;
  va_start(ap, zFormat);
  if( pCheck->errMsg.nChar ){
    sqlite3StrAccumAppend(&pCheck->errMsg, "\n", 1);
  }
  if( pCheck->zPfx ){
    sqlite3_snprintf(sizeof(zBuf), zBuf, pCheck->zPfx, pCheck->v1, pCheck->v2);
    sqlite3StrAccumAppendAll(&pCheck->errMsg, zBuf);
  }
  sqlite3VXPrintf(&pCheck->errMsg, 1, zFormat, ap);
  va_end(ap);
  if( pCheck->errMsg.accError==STRACCUM_NOMEM ){
    pCheck->mallocFailed = 1;
  }
}
................................................................................
** Add 1 to the reference count for page iPage.  If this is the second
** reference to the page, add an error message to pCheck->zErrMsg.
** Return 1 if there are 2 or more references to the page and 0 if
** if this is the first reference to the page.
**
** Also check that the page number is in bounds.
*/
static int checkRef(IntegrityCk *pCheck, Pgno iPage){
  if( iPage==0 ) return 1;
  if( iPage>pCheck->nPage ){
    checkAppendMsg(pCheck, "invalid page number %d", iPage);
    return 1;
  }
  if( getPageReferenced(pCheck, iPage) ){
    checkAppendMsg(pCheck, "2nd reference to page %d", iPage);
    return 1;
  }
  setPageReferenced(pCheck, iPage);
  return 0;
}

#ifndef SQLITE_OMIT_AUTOVACUUM
................................................................................
** page iParent, pointer type ptrType. If not, append an error message
** to pCheck.
*/
static void checkPtrmap(
  IntegrityCk *pCheck,   /* Integrity check context */
  Pgno iChild,           /* Child page number */
  u8 eType,              /* Expected pointer map type */
  Pgno iParent           /* Expected pointer map parent page number */

){
  int rc;
  u8 ePtrmapType;
  Pgno iPtrmapParent;

  rc = ptrmapGet(pCheck->pBt, iChild, &ePtrmapType, &iPtrmapParent);
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ) pCheck->mallocFailed = 1;
    checkAppendMsg(pCheck, "Failed to read ptrmap key=%d", iChild);
    return;
  }

  if( ePtrmapType!=eType || iPtrmapParent!=iParent ){
    checkAppendMsg(pCheck,
      "Bad ptr map entry key=%d expected=(%d,%d) got=(%d,%d)", 
      iChild, eType, iParent, ePtrmapType, iPtrmapParent);
  }
}
#endif

/*
................................................................................
** Check the integrity of the freelist or of an overflow page list.
** Verify that the number of pages on the list is N.
*/
static void checkList(
  IntegrityCk *pCheck,  /* Integrity checking context */
  int isFreeList,       /* True for a freelist.  False for overflow page list */
  int iPage,            /* Page number for first page in the list */
  int N                 /* Expected number of pages in the list */

){
  int i;
  int expected = N;
  int iFirst = iPage;
  while( N-- > 0 && pCheck->mxErr ){
    DbPage *pOvflPage;
    unsigned char *pOvflData;
    if( iPage<1 ){
      checkAppendMsg(pCheck,
         "%d of %d pages missing from overflow list starting at %d",
          N+1, expected, iFirst);
      break;
    }
    if( checkRef(pCheck, iPage) ) break;
    if( sqlite3PagerGet(pCheck->pPager, (Pgno)iPage, &pOvflPage) ){
      checkAppendMsg(pCheck, "failed to get page %d", iPage);
      break;
    }
    pOvflData = (unsigned char *)sqlite3PagerGetData(pOvflPage);
    if( isFreeList ){
      int n = get4byte(&pOvflData[4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
      if( pCheck->pBt->autoVacuum ){
        checkPtrmap(pCheck, iPage, PTRMAP_FREEPAGE, 0);
      }
#endif
      if( n>(int)pCheck->pBt->usableSize/4-2 ){
        checkAppendMsg(pCheck,
           "freelist leaf count too big on page %d", iPage);
        N--;
      }else{
        for(i=0; i<n; i++){
          Pgno iFreePage = get4byte(&pOvflData[8+i*4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
          if( pCheck->pBt->autoVacuum ){
            checkPtrmap(pCheck, iFreePage, PTRMAP_FREEPAGE, 0);
          }
#endif
          checkRef(pCheck, iFreePage);
        }
        N -= n;
      }
    }
#ifndef SQLITE_OMIT_AUTOVACUUM
    else{
      /* If this database supports auto-vacuum and iPage is not the last
      ** page in this overflow list, check that the pointer-map entry for
      ** the following page matches iPage.
      */
      if( pCheck->pBt->autoVacuum && N>0 ){
        i = get4byte(pOvflData);
        checkPtrmap(pCheck, i, PTRMAP_OVERFLOW2, iPage);
      }
    }
#endif
    iPage = get4byte(pOvflData);
    sqlite3PagerUnref(pOvflPage);
  }
}
................................................................................
**      7.  Verify that the depth of all children is the same.
**      8.  Make sure this page is at least 33% full or else it is
**          the root of the tree.
*/
static int checkTreePage(
  IntegrityCk *pCheck,  /* Context for the sanity check */
  int iPage,            /* Page number of the page to check */

  i64 *pnParentMinKey, 
  i64 *pnParentMaxKey
){
  MemPage *pPage;
  int i, rc, depth, d2, pgno, cnt;
  int hdr, cellStart;
  int nCell;
  u8 *data;
  BtShared *pBt;
  int usableSize;

  char *hit = 0;
  i64 nMinKey = 0;
  i64 nMaxKey = 0;
  const char *saved_zPfx = pCheck->zPfx;
  int saved_v1 = pCheck->v1;
  int saved_v2 = pCheck->v2;

  /* Check that the page exists
  */
  pBt = pCheck->pBt;
  usableSize = pBt->usableSize;
  if( iPage==0 ) return 0;
  if( checkRef(pCheck, iPage) ) return 0;
  pCheck->zPfx = "Page %d: ";
  pCheck->v1 = iPage;
  if( (rc = btreeGetPage(pBt, (Pgno)iPage, &pPage, 0))!=0 ){
    checkAppendMsg(pCheck,
       "unable to get the page. error code=%d", rc);

    depth = -1;
    goto end_of_check;
  }

  /* Clear MemPage.isInit to make sure the corruption detection code in
  ** btreeInitPage() is executed.  */
  pPage->isInit = 0;
  if( (rc = btreeInitPage(pPage))!=0 ){
    assert( rc==SQLITE_CORRUPT );  /* The only possible error from InitPage */
    checkAppendMsg(pCheck,
                   "btreeInitPage() returns error code %d", rc);
    releasePage(pPage);
    depth = -1;
    goto end_of_check;
  }

  /* Check out all the cells.
  */
  depth = 0;
  for(i=0; i<pPage->nCell && pCheck->mxErr; i++){
    u8 *pCell;
    u32 sz;
    CellInfo info;

    /* Check payload overflow pages
    */
    pCheck->zPfx = "On tree page %d cell %d: ";
    pCheck->v1 = iPage;
    pCheck->v2 = i;
    pCell = findCell(pPage,i);
    btreeParseCellPtr(pPage, pCell, &info);
    sz = info.nPayload;
    /* For intKey pages, check that the keys are in order.
    */
    if( pPage->intKey ){
      if( i==0 ){
        nMinKey = nMaxKey = info.nKey;
      }else if( info.nKey <= nMaxKey ){
        checkAppendMsg(pCheck,
           "Rowid %lld out of order (previous was %lld)", info.nKey, nMaxKey);
      }
      nMaxKey = info.nKey;
    }
    if( (sz>info.nLocal) 
     && (&pCell[info.iOverflow]<=&pPage->aData[pBt->usableSize])
    ){
      int nPage = (sz - info.nLocal + usableSize - 5)/(usableSize - 4);
      Pgno pgnoOvfl = get4byte(&pCell[info.iOverflow]);
#ifndef SQLITE_OMIT_AUTOVACUUM
      if( pBt->autoVacuum ){
        checkPtrmap(pCheck, pgnoOvfl, PTRMAP_OVERFLOW1, iPage);
      }
#endif
      checkList(pCheck, 0, pgnoOvfl, nPage);
    }

    /* Check sanity of left child page.
    */
    if( !pPage->leaf ){
      pgno = get4byte(pCell);
#ifndef SQLITE_OMIT_AUTOVACUUM
      if( pBt->autoVacuum ){
        checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
      }
#endif
      d2 = checkTreePage(pCheck, pgno, &nMinKey, i==0?NULL:&nMaxKey);
      if( i>0 && d2!=depth ){
        checkAppendMsg(pCheck, "Child page depth differs");
      }
      depth = d2;
    }
  }

  if( !pPage->leaf ){
    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);

    pCheck->zPfx = "On page %d at right child: ";
    pCheck->v1 = iPage;
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( pBt->autoVacuum ){
      checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
    }
#endif
    checkTreePage(pCheck, pgno, NULL, !pPage->nCell?NULL:&nMaxKey);
  }
 
  /* For intKey leaf pages, check that the min/max keys are in order
  ** with any left/parent/right pages.
  */
  pCheck->zPfx = "Page %d: ";
  pCheck->v1 = iPage;
  if( pPage->leaf && pPage->intKey ){
    /* if we are a left child page */
    if( pnParentMinKey ){
      /* if we are the left most child page */
      if( !pnParentMaxKey ){
        if( nMaxKey > *pnParentMinKey ){
          checkAppendMsg(pCheck,
              "Rowid %lld out of order (max larger than parent min of %lld)",
              nMaxKey, *pnParentMinKey);
        }
      }else{
        if( nMinKey <= *pnParentMinKey ){
          checkAppendMsg(pCheck,
              "Rowid %lld out of order (min less than parent min of %lld)",
              nMinKey, *pnParentMinKey);
        }
        if( nMaxKey > *pnParentMaxKey ){
          checkAppendMsg(pCheck,
              "Rowid %lld out of order (max larger than parent max of %lld)",
              nMaxKey, *pnParentMaxKey);
        }
        *pnParentMinKey = nMaxKey;
      }
    /* else if we're a right child page */
    } else if( pnParentMaxKey ){
      if( nMinKey <= *pnParentMaxKey ){
        checkAppendMsg(pCheck,
            "Rowid %lld out of order (min less than parent max of %lld)",
            nMinKey, *pnParentMaxKey);
      }
    }
  }

  /* Check for complete coverage of the page
  */
  data = pPage->aData;
  hdr = pPage->hdrOffset;
  hit = sqlite3PageMalloc( pBt->pageSize );
  pCheck->zPfx = 0;
  if( hit==0 ){
    pCheck->mallocFailed = 1;
  }else{
    int contentOffset = get2byteNotZero(&data[hdr+5]);
    assert( contentOffset<=usableSize );  /* Enforced by btreeInitPage() */
    memset(hit+contentOffset, 0, usableSize-contentOffset);
    memset(hit, 1, contentOffset);
................................................................................
      int pc = get2byte(&data[cellStart+i*2]);
      u32 size = 65536;
      int j;
      if( pc<=usableSize-4 ){
        size = cellSizePtr(pPage, &data[pc]);
      }
      if( (int)(pc+size-1)>=usableSize ){
        pCheck->zPfx = 0;
        checkAppendMsg(pCheck,
            "Corruption detected in cell %d on page %d",i,iPage);
      }else{
        for(j=pc+size-1; j>=pc; j--) hit[j]++;
      }
    }
    i = get2byte(&data[hdr+1]);
    while( i>0 ){
................................................................................
      assert( j<=usableSize-4 );   /* Enforced by btreeInitPage() */
      i = j;
    }
    for(i=cnt=0; i<usableSize; i++){
      if( hit[i]==0 ){
        cnt++;
      }else if( hit[i]>1 ){
        checkAppendMsg(pCheck,
          "Multiple uses for byte %d of page %d", i, iPage);
        break;
      }
    }
    if( cnt!=data[hdr+7] ){
      checkAppendMsg(pCheck,
          "Fragmentation of %d bytes reported as %d on page %d",
          cnt, data[hdr+7], iPage);
    }
  }
  sqlite3PageFree(hit);
  releasePage(pPage);

end_of_check:
  pCheck->zPfx = saved_zPfx;
  pCheck->v1 = saved_v1;
  pCheck->v2 = saved_v2;
  return depth+1;
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */

#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** This routine does a complete check of the given BTree file.  aRoot[] is
................................................................................
  nRef = sqlite3PagerRefcount(pBt->pPager);
  sCheck.pBt = pBt;
  sCheck.pPager = pBt->pPager;
  sCheck.nPage = btreePagecount(sCheck.pBt);
  sCheck.mxErr = mxErr;
  sCheck.nErr = 0;
  sCheck.mallocFailed = 0;
  sCheck.zPfx = 0;
  sCheck.v1 = 0;
  sCheck.v2 = 0;
  *pnErr = 0;
  if( sCheck.nPage==0 ){
    sqlite3BtreeLeave(p);
    return 0;
  }

  sCheck.aPgRef = sqlite3MallocZero((sCheck.nPage / 8)+ 1);
................................................................................
  i = PENDING_BYTE_PAGE(pBt);
  if( i<=sCheck.nPage ) setPageReferenced(&sCheck, i);
  sqlite3StrAccumInit(&sCheck.errMsg, zErr, sizeof(zErr), SQLITE_MAX_LENGTH);
  sCheck.errMsg.useMalloc = 2;

  /* Check the integrity of the freelist
  */
  sCheck.zPfx = "Main freelist: ";
  checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
            get4byte(&pBt->pPage1->aData[36]));
  sCheck.zPfx = 0;

  /* Check all the tables.
  */
  for(i=0; (int)i<nRoot && sCheck.mxErr; i++){
    if( aRoot[i]==0 ) continue;
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( pBt->autoVacuum && aRoot[i]>1 ){
      checkPtrmap(&sCheck, aRoot[i], PTRMAP_ROOTPAGE, 0);
    }
#endif
    sCheck.zPfx = "List of tree roots: ";
    checkTreePage(&sCheck, aRoot[i], NULL, NULL);
    sCheck.zPfx = 0;
  }

  /* Make sure every page in the file is referenced
  */
  for(i=1; i<=sCheck.nPage && sCheck.mxErr; i++){
#ifdef SQLITE_OMIT_AUTOVACUUM
    if( getPageReferenced(&sCheck, i)==0 ){
      checkAppendMsg(&sCheck, "Page %d is never used", i);
    }
#else
    /* If the database supports auto-vacuum, make sure no tables contain
    ** references to pointer-map pages.
    */
    if( getPageReferenced(&sCheck, i)==0 && 
       (PTRMAP_PAGENO(pBt, i)!=i || !pBt->autoVacuum) ){
      checkAppendMsg(&sCheck, "Page %d is never used", i);
    }
    if( getPageReferenced(&sCheck, i)!=0 && 
       (PTRMAP_PAGENO(pBt, i)==i && pBt->autoVacuum) ){
      checkAppendMsg(&sCheck, "Pointer map page %d is referenced", i);
    }
#endif
  }

  /* Make sure this analysis did not leave any unref() pages.
  ** This is an internal consistency check; an integrity check
  ** of the integrity check.
  */
  if( NEVER(nRef != sqlite3PagerRefcount(pBt->pPager)) ){
    checkAppendMsg(&sCheck,
      "Outstanding page count goes from %d to %d during this analysis",
      nRef, sqlite3PagerRefcount(pBt->pPager)
    );
  }

  /* Clean  up and report errors.
  */

  BtShared *pBt;    /* The tree being checked out */
  Pager *pPager;    /* The associated pager.  Also accessible by pBt->pPager */
  u8 *aPgRef;       /* 1 bit per page in the db (see above) */
  Pgno nPage;       /* Number of pages in the database */
  int mxErr;        /* Stop accumulating errors when this reaches zero */
  int nErr;         /* Number of messages written to zErrMsg so far */
  int mallocFailed; /* A memory allocation error has occurred */


  StrAccum errMsg;  /* Accumulate the error message text here */
};

/*
** Routines to read or write a two- and four-byte big-endian integer values.
*/
#define get2byte(x)   ((x)[0]<<8 | (x)[1])
#define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v))
#define get4byte sqlite3Get4byte
#define put4byte sqlite3Put4byte

  BtShared *pBt;    /* The tree being checked out */
  Pager *pPager;    /* The associated pager.  Also accessible by pBt->pPager */
  u8 *aPgRef;       /* 1 bit per page in the db (see above) */
  Pgno nPage;       /* Number of pages in the database */
  int mxErr;        /* Stop accumulating errors when this reaches zero */
  int nErr;         /* Number of messages written to zErrMsg so far */
  int mallocFailed; /* A memory allocation error has occurred */
  const char *zPfx; /* Error message prefix */
  int v1, v2;       /* Values for up to two %d fields in zPfx */
  StrAccum errMsg;  /* Accumulate the error message text here */
};

/*
** Routines to read or write a two- and four-byte big-endian integer values.
*/
#define get2byte(x)   ((x)[0]<<8 | (x)[1])
#define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v))
#define get4byte sqlite3Get4byte
#define put4byte sqlite3Put4byte