SQLite

  assert( p->sharable==0 || p->locked==0 || sqlite3_mutex_held(p->pBt->mutex) );
  assert( p->sharable==0 || p->locked==0 || sqlite3_mutex_held(p->db->mutex) );

  return (p->sharable==0 || p->locked);
}
#endif


#ifndef SQLITE_OMIT_INCRBLOB
/*
** Enter and leave a mutex on a Btree given a cursor owned by that
** Btree.  These entry points are used by incremental I/O and can be
** omitted if that module is not used.
*/
void sqlite3BtreeEnterCursor(BtCursor *pCur){
  sqlite3BtreeEnter(pCur->pBtree);
}
void sqlite3BtreeLeaveCursor(BtCursor *pCur){
  sqlite3BtreeLeave(pCur->pBtree);
}
#endif /* SQLITE_OMIT_INCRBLOB */


/*
** Enter the mutex on every Btree associated with a database
** connection.  This is needed (for example) prior to parsing
** a statement since we will be comparing table and column names
** against all schemas and we do not want those schemas being
** reset out from under us.

  assert( sqlite3_mutex_held(db->mutex) );
  for(i=0; i<db->nDb; i++){
    p = db->aDb[i].pBt;
    if( p ) sqlite3BtreeLeave(p);
  }
}

/*
** Return true if a particular Btree requires a lock.  Return FALSE if
** no lock is ever required since it is not sharable.
*/
int sqlite3BtreeSharable(Btree *p){
  return p->sharable;
}

#ifndef NDEBUG
/*
** Return true if the current thread holds the database connection
** mutex and all required BtShared mutexes.
**
** This routine is used inside assert() statements only.
*/

    Btree *p = db->aDb[i].pBt;
    if( p ){
      p->pBt->db = p->db;
    }
  }
}
#endif /* if SQLITE_THREADSAFE */

#ifndef SQLITE_OMIT_INCRBLOB
/*
** Enter a mutex on a Btree given a cursor owned by that Btree. 
**
** These entry points are used by incremental I/O only. Enter() is required 
** any time OMIT_SHARED_CACHE is not defined, regardless of whether or not 
** the build is threadsafe. Leave() is only required by threadsafe builds.
*/
void sqlite3BtreeEnterCursor(BtCursor *pCur){
  sqlite3BtreeEnter(pCur->pBtree);
}
# if SQLITE_THREADSAFE
void sqlite3BtreeLeaveCursor(BtCursor *pCur){
  sqlite3BtreeLeave(pCur->pBtree);
}
# endif
#endif /* ifndef SQLITE_OMIT_INCRBLOB */

#endif /* ifndef SQLITE_OMIT_SHARED_CACHE */

**
** Verify that the cursor holds the mutex on its BtShared
*/
#ifdef SQLITE_DEBUG
static int cursorHoldsMutex(BtCursor *p){
  return sqlite3_mutex_held(p->pBt->mutex);
}
static int cursorOwnsBtShared(BtCursor *p){
  assert( cursorHoldsMutex(p) );
  return (p->pBtree->db==p->pBt->db);
}
#endif

/*
** Invalidate the overflow cache of the cursor passed as the first argument.
** on the shared btree structure pBt.
*/
#define invalidateOverflowCache(pCur) (pCur->curFlags &= ~BTCF_ValidOvfl)

** saved position info stored by saveCursorPosition(), so there can be
** at most one effective restoreCursorPosition() call after each 
** saveCursorPosition().
*/
static int btreeRestoreCursorPosition(BtCursor *pCur){
  int rc;
  int skipNext;
  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( pCur->eState>=CURSOR_REQUIRESEEK );
  if( pCur->eState==CURSOR_FAULT ){
    return pCur->skipNext;
  }
  pCur->eState = CURSOR_INVALID;
  rc = btreeMoveto(pCur, pCur->pKey, pCur->nKey, 0, &skipNext);
  if( rc==SQLITE_OK ){

** of A's read lock.  A tries to promote to reserved but is blocked by B.
** One or the other of the two processes must give way or there can be
** no progress.  By returning SQLITE_BUSY and not invoking the busy callback
** when A already has a read lock, we encourage A to give up and let B
** proceed.
*/
int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
  sqlite3 *pBlock = 0;
  BtShared *pBt = p->pBt;
  int rc = SQLITE_OK;

  sqlite3BtreeEnter(p);
  btreeIntegrity(p);

  /* If the btree is already in a write-transaction, or it

  /* Write transactions are not possible on a read-only database */
  if( (pBt->btsFlags & BTS_READ_ONLY)!=0 && wrflag ){
    rc = SQLITE_READONLY;
    goto trans_begun;
  }

#ifndef SQLITE_OMIT_SHARED_CACHE
  {
    sqlite3 *pBlock = 0;
  /* If another database handle has already opened a write transaction 
  ** on this shared-btree structure and a second write transaction is
  ** requested, return SQLITE_LOCKED.
  */
  if( (wrflag && pBt->inTransaction==TRANS_WRITE)
   || (pBt->btsFlags & BTS_PENDING)!=0
  ){
    pBlock = pBt->pWriter->db;
  }else if( wrflag>1 ){
    BtLock *pIter;
    for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
      if( pIter->pBtree!=p ){
        pBlock = pIter->pBtree->db;
        break;
      }
    }
  }
  if( pBlock ){
    sqlite3ConnectionBlocked(p->db, pBlock);
    rc = SQLITE_LOCKED_SHAREDCACHE;
    goto trans_begun;
    /* If another database handle has already opened a write transaction 
    ** on this shared-btree structure and a second write transaction is
    ** requested, return SQLITE_LOCKED.
    */
    if( (wrflag && pBt->inTransaction==TRANS_WRITE)
     || (pBt->btsFlags & BTS_PENDING)!=0
    ){
      pBlock = pBt->pWriter->db;
    }else if( wrflag>1 ){
      BtLock *pIter;
      for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
        if( pIter->pBtree!=p ){
          pBlock = pIter->pBtree->db;
          break;
        }
      }
    }
    if( pBlock ){
      sqlite3ConnectionBlocked(p->db, pBlock);
      rc = SQLITE_LOCKED_SHAREDCACHE;
      goto trans_begun;
    }
  }
#endif

  /* Any read-only or read-write transaction implies a read-lock on 
  ** page 1. So if some other shared-cache client already has a write-lock 
  ** on page 1, the transaction cannot be opened. */
  rc = querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK);

** that the cursor has Cursor.eState==CURSOR_VALID.
**
** Failure is not possible.  This function always returns SQLITE_OK.
** It might just as well be a procedure (returning void) but we continue
** to return an integer result code for historical reasons.
*/
int sqlite3BtreeDataSize(BtCursor *pCur, u32 *pSize){
  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  assert( pCur->iPage>=0 );
  assert( pCur->iPage<BTCURSOR_MAX_DEPTH );
  assert( pCur->apPage[pCur->iPage]->intKeyLeaf==1 );
  getCellInfo(pCur);
  *pSize = pCur->info.nPayload;
  return SQLITE_OK;

#ifndef SQLITE_OMIT_INCRBLOB
  if ( pCur->eState==CURSOR_INVALID ){
    return SQLITE_ABORT;
  }
#endif

  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  rc = restoreCursorPosition(pCur);
  if( rc==SQLITE_OK ){
    assert( pCur->eState==CURSOR_VALID );
    assert( pCur->iPage>=0 && pCur->apPage[pCur->iPage] );
    assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
    rc = accessPayload(pCur, offset, amt, pBuf, 0);
  }

  BtCursor *pCur,      /* Cursor pointing to entry to read from */
  u32 *pAmt            /* Write the number of available bytes here */
){
  u32 amt;
  assert( pCur!=0 && pCur->iPage>=0 && pCur->apPage[pCur->iPage]);
  assert( pCur->eState==CURSOR_VALID );
  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
  assert( pCur->info.nSize>0 );
  assert( pCur->info.pPayload>pCur->apPage[pCur->iPage]->aData || CORRUPT_DB );
  assert( pCur->info.pPayload<pCur->apPage[pCur->iPage]->aDataEnd ||CORRUPT_DB);
  amt = (int)(pCur->apPage[pCur->iPage]->aDataEnd - pCur->info.pPayload);
  if( pCur->info.nLocal<amt ) amt = pCur->info.nLocal;
  *pAmt = amt;

** the new child page does not match the flags field of the parent (i.e.
** if an intkey page appears to be the parent of a non-intkey page, or
** vice-versa).
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
  BtShared *pBt = pCur->pBt;

  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  assert( pCur->iPage<BTCURSOR_MAX_DEPTH );
  assert( pCur->iPage>=0 );
  if( pCur->iPage>=(BTCURSOR_MAX_DEPTH-1) ){
    return SQLITE_CORRUPT_BKPT;
  }
  pCur->info.nSize = 0;

**
** pCur->idx is set to the cell index that contains the pointer
** to the page we are coming from.  If we are coming from the
** right-most child page then pCur->idx is set to one more than
** the largest cell index.
*/
static void moveToParent(BtCursor *pCur){
  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  assert( pCur->iPage>0 );
  assert( pCur->apPage[pCur->iPage] );
  assertParentIndex(
    pCur->apPage[pCur->iPage-1], 
    pCur->aiIdx[pCur->iPage-1], 
    pCur->apPage[pCur->iPage]->pgno

** structure the flags byte is set to 0x02 or 0x0A, indicating an index
** b-tree).
*/
static int moveToRoot(BtCursor *pCur){
  MemPage *pRoot;
  int rc = SQLITE_OK;

  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
  assert( CURSOR_VALID   < CURSOR_REQUIRESEEK );
  assert( CURSOR_FAULT   > CURSOR_REQUIRESEEK );
  if( pCur->eState>=CURSOR_REQUIRESEEK ){
    if( pCur->eState==CURSOR_FAULT ){
      assert( pCur->skipNext!=SQLITE_OK );
      return pCur->skipNext;

** in ascending order.
*/
static int moveToLeftmost(BtCursor *pCur){
  Pgno pgno;
  int rc = SQLITE_OK;
  MemPage *pPage;

  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  while( rc==SQLITE_OK && !(pPage = pCur->apPage[pCur->iPage])->leaf ){
    assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
    pgno = get4byte(findCell(pPage, pCur->aiIdx[pCur->iPage]));
    rc = moveToChild(pCur, pgno);
  }
  return rc;

** key in ascending order.
*/
static int moveToRightmost(BtCursor *pCur){
  Pgno pgno;
  int rc = SQLITE_OK;
  MemPage *pPage = 0;

  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  while( !(pPage = pCur->apPage[pCur->iPage])->leaf ){
    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
    pCur->aiIdx[pCur->iPage] = pPage->nCell;
    rc = moveToChild(pCur, pgno);
    if( rc ) return rc;
  }
  pCur->aiIdx[pCur->iPage] = pPage->nCell-1;
  assert( pCur->info.nSize==0 );
  assert( (pCur->curFlags & BTCF_ValidNKey)==0 );
  return SQLITE_OK;
}

/* Move the cursor to the first entry in the table.  Return SQLITE_OK
** on success.  Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
  int rc;

  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
  rc = moveToRoot(pCur);
  if( rc==SQLITE_OK ){
    if( pCur->eState==CURSOR_INVALID ){
      assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
      *pRes = 1;
    }else{

/* Move the cursor to the last entry in the table.  Return SQLITE_OK
** on success.  Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
  int rc;
 
  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );

  /* If the cursor already points to the last entry, this is a no-op. */
  if( CURSOR_VALID==pCur->eState && (pCur->curFlags & BTCF_AtLast)!=0 ){
#ifdef SQLITE_DEBUG
    /* This block serves to assert() that the cursor really does point 
    ** to the last entry in the b-tree. */

  i64 intKey,              /* The table key */
  int biasRight,           /* If true, bias the search to the high end */
  int *pRes                /* Write search results here */
){
  int rc;
  RecordCompare xRecordCompare;

  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
  assert( pRes );
  assert( (pIdxKey==0)==(pCur->pKeyInfo==0) );

  /* If the cursor is already positioned at the point we are trying
  ** to move to, then just return without doing any work */
  if( pCur->eState==CURSOR_VALID && (pCur->curFlags & BTCF_ValidNKey)!=0

** implementation does use this hint, however.)
*/
static SQLITE_NOINLINE int btreeNext(BtCursor *pCur, int *pRes){
  int rc;
  int idx;
  MemPage *pPage;

  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
  assert( *pRes==0 );
  if( pCur->eState!=CURSOR_VALID ){
    assert( (pCur->curFlags & BTCF_ValidOvfl)==0 );
    rc = restoreCursorPosition(pCur);
    if( rc!=SQLITE_OK ){
      return rc;

    return SQLITE_OK;
  }else{
    return moveToLeftmost(pCur);
  }
}
int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
  MemPage *pPage;
  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( pRes!=0 );
  assert( *pRes==0 || *pRes==1 );
  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
  pCur->info.nSize = 0;
  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
  *pRes = 0;
  if( pCur->eState!=CURSOR_VALID ) return btreeNext(pCur, pRes);

** SQLite btree implementation does not. (Note that the comdb2 btree
** implementation does use this hint, however.)
*/
static SQLITE_NOINLINE int btreePrevious(BtCursor *pCur, int *pRes){
  int rc;
  MemPage *pPage;

  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( pRes!=0 );
  assert( *pRes==0 );
  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
  assert( (pCur->curFlags & (BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey))==0 );
  assert( pCur->info.nSize==0 );
  if( pCur->eState!=CURSOR_VALID ){
    rc = restoreCursorPosition(pCur);

    }else{
      rc = SQLITE_OK;
    }
  }
  return rc;
}
int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( pRes!=0 );
  assert( *pRes==0 || *pRes==1 );
  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
  *pRes = 0;
  pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey);
  pCur->info.nSize = 0;
  if( pCur->eState!=CURSOR_VALID

  unsigned char *newCell = 0;

  if( pCur->eState==CURSOR_FAULT ){
    assert( pCur->skipNext!=SQLITE_OK );
    return pCur->skipNext;
  }

  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( (pCur->curFlags & BTCF_WriteFlag)!=0
              && pBt->inTransaction==TRANS_WRITE
              && (pBt->btsFlags & BTS_READ_ONLY)==0 );
  assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );

  /* Assert that the caller has been consistent. If this cursor was opened
  ** expecting an index b-tree, then the caller should be inserting blob

  MemPage *pPage;                      /* Page to delete cell from */
  unsigned char *pCell;                /* Pointer to cell to delete */
  int iCellIdx;                        /* Index of cell to delete */
  int iCellDepth;                      /* Depth of node containing pCell */ 
  u16 szCell;                          /* Size of the cell being deleted */
  int bSkipnext = 0;                   /* Leaf cursor in SKIPNEXT state */

  assert( cursorHoldsMutex(pCur) );
  assert( cursorOwnsBtShared(pCur) );
  assert( pBt->inTransaction==TRANS_WRITE );
  assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
  assert( pCur->curFlags & BTCF_WriteFlag );
  assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
  assert( !hasReadConflicts(p, pCur->pgnoRoot) );
  assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
  assert( pCur->eState==CURSOR_VALID );

** Only the data content may only be modified, it is not possible to 
** change the length of the data stored. If this function is called with
** parameters that attempt to write past the end of the existing data,
** no modifications are made and SQLITE_CORRUPT is returned.
*/
int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
  int rc;
  assert( cursorHoldsMutex(pCsr) );
  assert( cursorOwnsBtShared(pCsr) );
  assert( sqlite3_mutex_held(pCsr->pBtree->db->mutex) );
  assert( pCsr->curFlags & BTCF_Incrblob );

  rc = restoreCursorPosition(pCsr);
  if( rc!=SQLITE_OK ){
    return rc;
  }

  return (p->pBt->btsFlags & BTS_READ_ONLY)!=0;
}

/*
** Return the size of the header added to each page by this module.
*/
int sqlite3HeaderSizeBtree(void){ return ROUND8(sizeof(MemPage)); }

#if !defined(SQLITE_OMIT_SHARED_CACHE)
/*
** Return true if the Btree passed as the only argument is sharable.
*/
int sqlite3BtreeSharable(Btree *p){
  return p->sharable;
}
#endif

** If we are not using shared cache, then there is no need to
** use mutexes to access the BtShared structures.  So make the
** Enter and Leave procedures no-ops.
*/
#ifndef SQLITE_OMIT_SHARED_CACHE
  void sqlite3BtreeEnter(Btree*);
  void sqlite3BtreeEnterAll(sqlite3*);
  int sqlite3BtreeSharable(Btree*);
  void sqlite3BtreeEnterCursor(BtCursor*);
#else
# define sqlite3BtreeEnter(X) 
# define sqlite3BtreeEnterAll(X)
# define sqlite3BtreeSharable(X) 0
# define sqlite3BtreeEnterCursor(X)
#endif

#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE
  int sqlite3BtreeSharable(Btree*);
  void sqlite3BtreeLeave(Btree*);
  void sqlite3BtreeEnterCursor(BtCursor*);
  void sqlite3BtreeLeaveCursor(BtCursor*);
  void sqlite3BtreeLeaveAll(sqlite3*);
#ifndef NDEBUG
  /* These routines are used inside assert() statements only. */
  int sqlite3BtreeHoldsMutex(Btree*);
  int sqlite3BtreeHoldsAllMutexes(sqlite3*);
  int sqlite3SchemaMutexHeld(sqlite3*,int,Schema*);
#endif
#else

# define sqlite3BtreeSharable(X) 0
# define sqlite3BtreeLeave(X)
# define sqlite3BtreeEnterCursor(X)
# define sqlite3BtreeLeaveCursor(X)
# define sqlite3BtreeLeaveAll(X)

# define sqlite3BtreeHoldsMutex(X) 1
# define sqlite3BtreeHoldsAllMutexes(X) 1
# define sqlite3SchemaMutexHeld(X,Y,Z) 1
#endif

**     creating ID lists
**     BEGIN TRANSACTION
**     COMMIT
**     ROLLBACK
*/
#include "sqliteInt.h"

/*
** This routine is called when a new SQL statement is beginning to
** be parsed.  Initialize the pParse structure as needed.
*/
void sqlite3BeginParse(Parse *pParse, int explainFlag){
  pParse->explain = (u8)explainFlag;
  pParse->nVar = 0;
}

#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** The TableLock structure is only used by the sqlite3TableLock() and
** codeTableLocks() functions.
*/
struct TableLock {
  int iDb;             /* The database containing the table to be locked */

  if( pToken ){
    if( op!=TK_INTEGER || pToken->z==0
          || sqlite3GetInt32(pToken->z, &iValue)==0 ){
      nExtra = pToken->n+1;
      assert( iValue>=0 );
    }
  }
  pNew = sqlite3DbMallocZero(db, sizeof(Expr)+nExtra);
  pNew = sqlite3DbMallocRaw(db, sizeof(Expr)+nExtra);
  if( pNew ){
    memset(pNew, 0, sizeof(Expr));
    pNew->op = (u8)op;
    pNew->iAgg = -1;
    if( pToken ){
      if( nExtra==0 ){
        pNew->flags |= EP_IntValue;
        pNew->u.iValue = iValue;
      }else{

  sqlite3_result_int(context, sqlite3_total_changes(db));
}

/*
** A structure defining how to do GLOB-style comparisons.
*/
struct compareInfo {
  u8 matchAll;
  u8 matchOne;
  u8 matchSet;
  u8 noCase;
  u8 matchAll;          /* "*" or "%" */
  u8 matchOne;          /* "?" or "_" */
  u8 matchSet;          /* "[" or 0 */
  u8 noCase;            /* true to ignore case differences */
};

/*
** For LIKE and GLOB matching on EBCDIC machines, assume that every
** character is exactly one byte in size.  Also, provde the Utf8Read()
** macro for fast reading of the next character in the common case where
** the next character is ASCII.

**
** This routine is usually quick, but can be N**2 in the worst case.
*/
static int patternCompare(
  const u8 *zPattern,              /* The glob pattern */
  const u8 *zString,               /* The string to compare against the glob */
  const struct compareInfo *pInfo, /* Information about how to do the compare */
  u32 esc                          /* The escape character */
  u32 matchOther                   /* The escape char (LIKE) or '[' (GLOB) */
){
  u32 c, c2;                       /* Next pattern and input string chars */
  u32 matchOne = pInfo->matchOne;  /* "?" or "_" */
  u32 matchAll = pInfo->matchAll;  /* "*" or "%" */
  u32 matchOther;                  /* "[" or the escape character */
  u8 noCase = pInfo->noCase;       /* True if uppercase==lowercase */
  const u8 *zEscaped = 0;          /* One past the last escaped input char */
  
  /* The GLOB operator does not have an ESCAPE clause.  And LIKE does not
  ** have the matchSet operator.  So we either have to look for one or
  ** the other, never both.  Hence the single variable matchOther is used
  ** to store the one we have to look for.
  */
  matchOther = esc ? esc : pInfo->matchSet;

  while( (c = Utf8Read(zPattern))!=0 ){
    if( c==matchAll ){  /* Match "*" */
      /* Skip over multiple "*" characters in the pattern.  If there
      ** are also "?" characters, skip those as well, but consume a
      ** single character of the input string for each "?" skipped */
      while( (c=Utf8Read(zPattern)) == matchAll || c == matchOne ){
        if( c==matchOne && sqlite3Utf8Read(&zString)==0 ){
          return 0;
        }
      }
      if( c==0 ){
        return 1;   /* "*" at the end of the pattern matches */
      }else if( c==matchOther ){
        if( esc ){
        if( pInfo->matchSet==0 ){
          c = sqlite3Utf8Read(&zPattern);
          if( c==0 ) return 0;
        }else{
          /* "[...]" immediately follows the "*".  We have to do a slow
          ** recursive search in this case, but it is an unusual case. */
          assert( matchOther<0x80 );  /* '[' is a single-byte character */
          while( *zString
                 && patternCompare(&zPattern[-1],zString,pInfo,esc)==0 ){
                 && patternCompare(&zPattern[-1],zString,pInfo,matchOther)==0 ){
            SQLITE_SKIP_UTF8(zString);
          }
          return *zString!=0;
        }
      }

      /* At this point variable c contains the first character of the

          cx = sqlite3Toupper(c);
          c = sqlite3Tolower(c);
        }else{
          cx = c;
        }
        while( (c2 = *(zString++))!=0 ){
          if( c2!=c && c2!=cx ) continue;
          if( patternCompare(zPattern,zString,pInfo,esc) ) return 1;
          if( patternCompare(zPattern,zString,pInfo,matchOther) ) return 1;
        }
      }else{
        while( (c2 = Utf8Read(zString))!=0 ){
          if( c2!=c ) continue;
          if( patternCompare(zPattern,zString,pInfo,esc) ) return 1;
          if( patternCompare(zPattern,zString,pInfo,matchOther) ) return 1;
        }
      }
      return 0;
    }
    if( c==matchOther ){
      if( esc ){
      if( pInfo->matchSet==0 ){
        c = sqlite3Utf8Read(&zPattern);
        if( c==0 ) return 0;
        zEscaped = zPattern;
      }else{
        u32 prior_c = 0;
        int seen = 0;
        int invert = 0;

  return *zString==0;
}

/*
** The sqlite3_strglob() interface.
*/
int sqlite3_strglob(const char *zGlobPattern, const char *zString){
  return patternCompare((u8*)zGlobPattern, (u8*)zString, &globInfo, 0)==0;
  return patternCompare((u8*)zGlobPattern, (u8*)zString, &globInfo, '[')==0;
}

/*
** The sqlite3_strlike() interface.
*/
int sqlite3_strlike(const char *zPattern, const char *zStr, unsigned int esc){
  return patternCompare((u8*)zPattern, (u8*)zStr, &likeInfoNorm, esc)==0;

*/
static void likeFunc(
  sqlite3_context *context, 
  int argc, 
  sqlite3_value **argv
){
  const unsigned char *zA, *zB;
  u32 escape = 0;
  u32 escape;
  int nPat;
  sqlite3 *db = sqlite3_context_db_handle(context);
  struct compareInfo *pInfo = sqlite3_user_data(context);

#ifdef SQLITE_LIKE_DOESNT_MATCH_BLOBS
  if( sqlite3_value_type(argv[0])==SQLITE_BLOB
   || sqlite3_value_type(argv[1])==SQLITE_BLOB
  ){
#ifdef SQLITE_TEST
    sqlite3_like_count++;

    if( zEsc==0 ) return;
    if( sqlite3Utf8CharLen((char*)zEsc, -1)!=1 ){
      sqlite3_result_error(context, 
          "ESCAPE expression must be a single character", -1);
      return;
    }
    escape = sqlite3Utf8Read(&zEsc);
  }else{
    escape = pInfo->matchSet;
  }
  if( zA && zB ){
    struct compareInfo *pInfo = sqlite3_user_data(context);
#ifdef SQLITE_TEST
    sqlite3_like_count++;
#endif
    
    sqlite3_result_int(context, patternCompare(zB, zA, pInfo, escape));
  }
}

/*
** Implementation of the NULLIF(x,y) function.  The result is the first
** argument if the arguments are different.  The result is NULL if the

  u8 *zPool;       /* Memory available to be allocated */
  
  /*
  ** Mutex to control access to the memory allocation subsystem.
  */
  sqlite3_mutex *mutex;

#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
  /*
  ** Performance statistics
  */
  u64 nAlloc;         /* Total number of calls to malloc */
  u64 totalAlloc;     /* Total of all malloc calls - includes internal frag */
  u64 totalExcess;    /* Total internal fragmentation */
  u32 currentOut;     /* Current checkout, including internal fragmentation */
  u32 currentCount;   /* Current number of distinct checkouts */
  u32 maxOut;         /* Maximum instantaneous currentOut */
  u32 maxCount;       /* Maximum instantaneous currentCount */
  u32 maxRequest;     /* Largest allocation (exclusive of internal frag) */
#endif
  
  /*
  ** Lists of free blocks.  aiFreelist[0] is a list of free blocks of
  ** size mem5.szAtom.  aiFreelist[1] holds blocks of size szAtom*2.
  ** aiFreelist[2] holds free blocks of size szAtom*4.  And so forth.
  */
  int aiFreelist[LOGMAX+1];

  int iBin;        /* Index into mem5.aiFreelist[] */
  int iFullSz;     /* Size of allocation rounded up to power of 2 */
  int iLogsize;    /* Log2 of iFullSz/POW2_MIN */

  /* nByte must be a positive */
  assert( nByte>0 );

  /* No more than 1GiB per allocation */
  if( nByte > 0x40000000 ) return 0;

#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
  /* Keep track of the maximum allocation request.  Even unfulfilled
  ** requests are counted */
  if( (u32)nByte>mem5.maxRequest ){
    /* Abort if the requested allocation size is larger than the largest
    ** power of two that we can represent using 32-bit signed integers. */
    if( nByte > 0x40000000 ) return 0;
    mem5.maxRequest = nByte;
  }
#endif


  /* Round nByte up to the next valid power of two */
  for(iFullSz=mem5.szAtom,iLogsize=0; iFullSz<nByte; iFullSz*=2,iLogsize++){}

  /* Make sure mem5.aiFreelist[iLogsize] contains at least one free
  ** block.  If not, then split a block of the next larger power of
  ** two in order to create a new free block of size iLogsize.

    iBin--;
    newSize = 1 << iBin;
    mem5.aCtrl[i+newSize] = CTRL_FREE | iBin;
    memsys5Link(i+newSize, iBin);
  }
  mem5.aCtrl[i] = iLogsize;

#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
  /* Update allocator performance statistics. */
  mem5.nAlloc++;
  mem5.totalAlloc += iFullSz;
  mem5.totalExcess += iFullSz - nByte;
  mem5.currentCount++;
  mem5.currentOut += iFullSz;
  if( mem5.maxCount<mem5.currentCount ) mem5.maxCount = mem5.currentCount;
  if( mem5.maxOut<mem5.currentOut ) mem5.maxOut = mem5.currentOut;
#endif

#ifdef SQLITE_DEBUG
  /* Make sure the allocated memory does not assume that it is set to zero
  ** or retains a value from a previous allocation */
  memset(&mem5.zPool[i*mem5.szAtom], 0xAA, iFullSz);
#endif

  iLogsize = mem5.aCtrl[iBlock] & CTRL_LOGSIZE;
  size = 1<<iLogsize;
  assert( iBlock+size-1<(u32)mem5.nBlock );

  mem5.aCtrl[iBlock] |= CTRL_FREE;
  mem5.aCtrl[iBlock+size-1] |= CTRL_FREE;

#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
  assert( mem5.currentCount>0 );
  assert( mem5.currentOut>=(size*mem5.szAtom) );
  mem5.currentCount--;
  mem5.currentOut -= size*mem5.szAtom;
  assert( mem5.currentOut>0 || mem5.currentCount==0 );
  assert( mem5.currentCount>0 || mem5.currentOut==0 );
#endif

  mem5.aCtrl[iBlock] = CTRL_FREE | iLogsize;
  while( ALWAYS(iLogsize<LOGMAX) ){
    int iBuddy;
    if( (iBlock>>iLogsize) & 1 ){
      iBuddy = iBlock - size;
    }else{

  { "fchown",       (sqlite3_syscall_ptr)fchown,          0 },
#define osFchown    ((int(*)(int,uid_t,gid_t))aSyscall[20].pCurrent)

  { "geteuid",      (sqlite3_syscall_ptr)geteuid,         0 },
#define osGeteuid   ((uid_t(*)(void))aSyscall[21].pCurrent)

#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
  { "mmap",       (sqlite3_syscall_ptr)mmap,     0 },
  { "mmap",         (sqlite3_syscall_ptr)mmap,            0 },
#else
  { "mmap",         (sqlite3_syscall_ptr)0,               0 },
#endif
#define osMmap ((void*(*)(void*,size_t,int,int,int,off_t))aSyscall[22].pCurrent)

#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
  { "munmap",       (sqlite3_syscall_ptr)munmap,          0 },
#else
  { "munmap",       (sqlite3_syscall_ptr)0,               0 },
#endif
#define osMunmap ((void*(*)(void*,size_t))aSyscall[23].pCurrent)

#if HAVE_MREMAP
#if HAVE_MREMAP && (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0)
  { "mremap",       (sqlite3_syscall_ptr)mremap,          0 },
#else
  { "mremap",       (sqlite3_syscall_ptr)0,               0 },
#endif
#define osMremap ((void*(*)(void*,size_t,size_t,int,...))aSyscall[24].pCurrent)

#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
  { "getpagesize",  (sqlite3_syscall_ptr)unixGetpagesize, 0 },
#else
  { "getpagesize",  (sqlite3_syscall_ptr)0,               0 },
#endif
#define osGetpagesize ((int(*)(void))aSyscall[25].pCurrent)

  { "readlink",     (sqlite3_syscall_ptr)readlink,        0 },
#define osReadlink ((ssize_t(*)(const char*,char*,size_t))aSyscall[26].pCurrent)

#endif

}; /* End of the overrideable system calls */


/*
** On some systems, calls to fchown() will trigger a message in a security
** log if they come from non-root processes.  So avoid calling fchown() if

// Input is a single SQL command
input ::= cmdlist.
cmdlist ::= cmdlist ecmd.
cmdlist ::= ecmd.
ecmd ::= SEMI.
ecmd ::= explain cmdx SEMI.
explain ::= .           { sqlite3BeginParse(pParse, 0); }
explain ::= .
%ifndef SQLITE_OMIT_EXPLAIN
explain ::= EXPLAIN.              { sqlite3BeginParse(pParse, 1); }
explain ::= EXPLAIN QUERY PLAN.   { sqlite3BeginParse(pParse, 2); }
explain ::= EXPLAIN.              { pParse->explain = 1; }
explain ::= EXPLAIN QUERY PLAN.   { pParse->explain = 2; }
%endif  SQLITE_OMIT_EXPLAIN
cmdx ::= cmd.           { sqlite3FinishCoding(pParse); }

///////////////////// Begin and end transactions. ////////////////////////////
//

cmd ::= BEGIN transtype(Y) trans_opt.  {sqlite3BeginTransaction(pParse, Y);}

#define PGHDR_DIRTY           0x002  /* Page is on the PCache.pDirty list */
#define PGHDR_WRITEABLE       0x004  /* Journaled and ready to modify */
#define PGHDR_NEED_SYNC       0x008  /* Fsync the rollback journal before
                                     ** writing this page to the database */
#define PGHDR_NEED_READ       0x010  /* Content is unread */
#define PGHDR_DONT_WRITE      0x020  /* Do not write content to disk */
#define PGHDR_MMAP            0x040  /* This is an mmap page object */

#define PGHDR_WAL_APPEND      0x080  /* Appended to wal file */

/* Initialize and shutdown the page cache subsystem */
int sqlite3PcacheInitialize(void);
void sqlite3PcacheShutdown(void);

/* Page cache buffer management:
** These routines implement SQLITE_CONFIG_PAGECACHE.

  u16 selFlags,         /* Flag parameters, such as SF_Distinct */
  Expr *pLimit,         /* LIMIT value.  NULL means not used */
  Expr *pOffset         /* OFFSET value.  NULL means no offset */
){
  Select *pNew;
  Select standin;
  sqlite3 *db = pParse->db;
  pNew = sqlite3DbMallocZero(db, sizeof(*pNew) );
  pNew = sqlite3DbMallocRaw(db, sizeof(*pNew) );
  if( pNew==0 ){
    assert( db->mallocFailed );
    pNew = &standin;
    memset(pNew, 0, sizeof(*pNew));
  }
  if( pEList==0 ){
    pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db,TK_ASTERISK,0));
  }
  pNew->pEList = pEList;
  pNew->op = TK_SELECT;
  pNew->selFlags = selFlags;
  pNew->iLimit = 0;
  pNew->iOffset = 0;
  pNew->addrOpenEphm[0] = -1;
  pNew->addrOpenEphm[1] = -1;
  pNew->nSelectRow = 0;
  if( pSrc==0 ) pSrc = sqlite3DbMallocZero(db, sizeof(*pSrc));
  pNew->pSrc = pSrc;
  pNew->pWhere = pWhere;
  pNew->pGroupBy = pGroupBy;
  pNew->pHaving = pHaving;
  pNew->pOrderBy = pOrderBy;
  pNew->selFlags = selFlags;
  pNew->op = TK_SELECT;
  pNew->pPrior = 0;
  pNew->pNext = 0;
  pNew->pLimit = pLimit;
  pNew->pOffset = pOffset;
  pNew->pWith = 0;
  assert( pOffset==0 || pLimit!=0 || pParse->nErr>0 || db->mallocFailed!=0 );
  pNew->addrOpenEphm[0] = -1;
  pNew->addrOpenEphm[1] = -1;
  if( db->mallocFailed ) {
    clearSelect(db, pNew, pNew!=&standin);
    pNew = 0;
  }else{
    assert( pNew->pSrc!=0 || pParse->nErr>0 );
  }
  assert( pNew!=&standin );

#endif

/*
** Default maximum size of memory used by memory-mapped I/O in the VFS
*/
#ifdef __APPLE__
# include <TargetConditionals.h>
# if TARGET_OS_IPHONE
#   undef SQLITE_MAX_MMAP_SIZE
#   define SQLITE_MAX_MMAP_SIZE 0
# endif
#endif
#ifndef SQLITE_MAX_MMAP_SIZE
# if defined(__linux__) \
  || defined(_WIN32) \
  || (defined(__APPLE__) && defined(__MACH__)) \
  || defined(__sun) \
  || defined(__FreeBSD__) \

u32 sqlite3ExprListFlags(const ExprList*);
int sqlite3Init(sqlite3*, char**);
int sqlite3InitCallback(void*, int, char**, char**);
void sqlite3Pragma(Parse*,Token*,Token*,Token*,int);
void sqlite3ResetAllSchemasOfConnection(sqlite3*);
void sqlite3ResetOneSchema(sqlite3*,int);
void sqlite3CollapseDatabaseArray(sqlite3*);
void sqlite3BeginParse(Parse*,int);
void sqlite3CommitInternalChanges(sqlite3*);
void sqlite3DeleteColumnNames(sqlite3*,Table*);
int sqlite3ColumnsFromExprList(Parse*,ExprList*,i16*,Column**);
Table *sqlite3ResultSetOfSelect(Parse*,Select*);
void sqlite3OpenMasterTable(Parse *, int);
Index *sqlite3PrimaryKeyIndex(Table*);
i16 sqlite3ColumnOfIndex(Index*, i16);

#endif

  if( objc==2 ){
    zArg = Tcl_GetStringFromObj(objv[1], 0);
    if( strcmp(zArg,"-version")==0 ){
      Tcl_AppendResult(interp,sqlite3_libversion(), (char*)0);
      return TCL_OK;
    }
    if( strcmp(zArg,"-sourceid")==0 ){
      Tcl_AppendResult(interp,sqlite3_sourceid(), (char*)0);
      return TCL_OK;
    }
    if( strcmp(zArg,"-has-codec")==0 ){
#ifdef SQLITE_HAS_CODEC
      Tcl_AppendResult(interp,"1",(char*)0);
#else
      Tcl_AppendResult(interp,"0",(char*)0);
#endif

void sqlite3VdbeSorterClose(sqlite3 *, VdbeCursor *);
int sqlite3VdbeSorterRowkey(const VdbeCursor *, Mem *);
int sqlite3VdbeSorterNext(sqlite3 *, const VdbeCursor *, int *);
int sqlite3VdbeSorterRewind(const VdbeCursor *, int *);
int sqlite3VdbeSorterWrite(const VdbeCursor *, Mem *);
int sqlite3VdbeSorterCompare(const VdbeCursor *, Mem *, int, int *);

#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
#if !defined(SQLITE_OMIT_SHARED_CACHE) 
  void sqlite3VdbeEnter(Vdbe*);
  void sqlite3VdbeLeave(Vdbe*);
#else
# define sqlite3VdbeEnter(X)
#endif

#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
  void sqlite3VdbeLeave(Vdbe*);
#else
# define sqlite3VdbeLeave(X)
#endif

#ifdef SQLITE_DEBUG
void sqlite3VdbeMemAboutToChange(Vdbe*,Mem*);
int sqlite3VdbeCheckMemInvariants(Mem*);
#endif

  assert( i<(int)sizeof(p->btreeMask)*8 );
  DbMaskSet(p->btreeMask, i);
  if( i!=1 && sqlite3BtreeSharable(p->db->aDb[i].pBt) ){
    DbMaskSet(p->lockMask, i);
  }
}

#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
#if !defined(SQLITE_OMIT_SHARED_CACHE)
/*
** If SQLite is compiled to support shared-cache mode and to be threadsafe,
** this routine obtains the mutex associated with each BtShared structure
** that may be accessed by the VM passed as an argument. In doing so it also
** sets the BtShared.db member of each of the BtShared structures, ensuring
** that the correct busy-handler callback is invoked if required.
**

  u8 ckptLock;               /* True if holding a checkpoint lock */
  u8 readOnly;               /* WAL_RDWR, WAL_RDONLY, or WAL_SHM_RDONLY */
  u8 truncateOnCommit;       /* True to truncate WAL file on commit */
  u8 syncHeader;             /* Fsync the WAL header if true */
  u8 padToSectorBoundary;    /* Pad transactions out to the next sector */
  WalIndexHdr hdr;           /* Wal-index header for current transaction */
  u32 minFrame;              /* Ignore wal frames before this one */
  u32 iReCksum;              /* On commit, recalculate checksums from here */
  const char *zWalName;      /* Name of WAL file */
  u32 nCkpt;                 /* Checkpoint sequence counter in the wal-header */
#ifdef SQLITE_DEBUG
  u8 lockError;              /* True if a locking error has occurred */
#endif
#ifdef SQLITE_ENABLE_SNAPSHOT
  WalIndexHdr *pSnapshot;    /* Start transaction here if not NULL */

  u8 *aFrame                      /* OUT: Write encoded frame here */
){
  int nativeCksum;                /* True for native byte-order checksums */
  u32 *aCksum = pWal->hdr.aFrameCksum;
  assert( WAL_FRAME_HDRSIZE==24 );
  sqlite3Put4byte(&aFrame[0], iPage);
  sqlite3Put4byte(&aFrame[4], nTruncate);
  if( pWal->iReCksum==0 ){
  memcpy(&aFrame[8], pWal->hdr.aSalt, 8);
    memcpy(&aFrame[8], pWal->hdr.aSalt, 8);

  nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
  walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
  walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
    nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
    walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
    walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);

  sqlite3Put4byte(&aFrame[16], aCksum[0]);
  sqlite3Put4byte(&aFrame[20], aCksum[1]);
    sqlite3Put4byte(&aFrame[16], aCksum[0]);
    sqlite3Put4byte(&aFrame[20], aCksum[1]);
  }
}

/*
** Check to see if the frame with header in aFrame[] and content
** in aData[] is valid.  If it is a valid frame, fill *piPage and
** *pnTruncate and return true.  Return if the frame is not valid.
*/

*/
int sqlite3WalBeginWriteTransaction(Wal *pWal){
  int rc;

  /* Cannot start a write transaction without first holding a read
  ** transaction. */
  assert( pWal->readLock>=0 );
  assert( pWal->writeLock==0 && pWal->iReCksum==0 );

  if( pWal->readOnly ){
    return SQLITE_READONLY;
  }

  /* Only one writer allowed at a time.  Get the write lock.  Return
  ** SQLITE_BUSY if unable.

** End a write transaction.  The commit has already been done.  This
** routine merely releases the lock.
*/
int sqlite3WalEndWriteTransaction(Wal *pWal){
  if( pWal->writeLock ){
    walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
    pWal->writeLock = 0;
    pWal->iReCksum = 0;
    pWal->truncateOnCommit = 0;
  }
  return SQLITE_OK;
}

/*
** If any data has been written (but not committed) to the log file, this

  rc = walWriteToLog(p, aFrame, sizeof(aFrame), iOffset);
  if( rc ) return rc;
  /* Write the page data */
  rc = walWriteToLog(p, pData, p->szPage, iOffset+sizeof(aFrame));
#endif
  return rc;
}

/*
** This function is called as part of committing a transaction within which
** one or more frames have been overwritten. It updates the checksums for
** all frames written to the wal file by the current transaction starting
** with the earliest to have been overwritten.
**
** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
*/
static int walRewriteChecksums(Wal *pWal, u32 iLast){
  const int szPage = pWal->szPage;/* Database page size */
  int rc = SQLITE_OK;             /* Return code */
  u8 *aBuf;                       /* Buffer to load data from wal file into */
  u8 aFrame[WAL_FRAME_HDRSIZE];   /* Buffer to assemble frame-headers in */
  u32 iRead;                      /* Next frame to read from wal file */
  i64 iCksumOff;

  aBuf = sqlite3_malloc(szPage + WAL_FRAME_HDRSIZE);
  if( aBuf==0 ) return SQLITE_NOMEM;

  /* Find the checksum values to use as input for the recalculating the
  ** first checksum. If the first frame is frame 1 (implying that the current
  ** transaction restarted the wal file), these values must be read from the
  ** wal-file header. Otherwise, read them from the frame header of the
  ** previous frame.  */
  assert( pWal->iReCksum>0 );
  if( pWal->iReCksum==1 ){
    iCksumOff = 24;
  }else{
    iCksumOff = walFrameOffset(pWal->iReCksum-1, szPage) + 16;
  }
  rc = sqlite3OsRead(pWal->pWalFd, aBuf, sizeof(u32)*2, iCksumOff);
  pWal->hdr.aFrameCksum[0] = sqlite3Get4byte(aBuf);
  pWal->hdr.aFrameCksum[1] = sqlite3Get4byte(&aBuf[sizeof(u32)]);

  iRead = pWal->iReCksum;
  pWal->iReCksum = 0;
  for(; rc==SQLITE_OK && iRead<=iLast; iRead++){
    i64 iOff = walFrameOffset(iRead, szPage);
    rc = sqlite3OsRead(pWal->pWalFd, aBuf, szPage+WAL_FRAME_HDRSIZE, iOff);
    if( rc==SQLITE_OK ){
      u32 iPgno, nDbSize;
      iPgno = sqlite3Get4byte(aBuf);
      nDbSize = sqlite3Get4byte(&aBuf[4]);

      walEncodeFrame(pWal, iPgno, nDbSize, &aBuf[WAL_FRAME_HDRSIZE], aFrame);
      rc = sqlite3OsWrite(pWal->pWalFd, aFrame, sizeof(aFrame), iOff);
    }
  }

  sqlite3_free(aBuf);
  return rc;
}

/* 
** Write a set of frames to the log. The caller must hold the write-lock
** on the log file (obtained using sqlite3WalBeginWriteTransaction()).
*/
int sqlite3WalFrames(
  Wal *pWal,                      /* Wal handle to write to */

  u32 iFrame;                     /* Next frame address */
  PgHdr *p;                       /* Iterator to run through pList with. */
  PgHdr *pLast = 0;               /* Last frame in list */
  int nExtra = 0;                 /* Number of extra copies of last page */
  int szFrame;                    /* The size of a single frame */
  i64 iOffset;                    /* Next byte to write in WAL file */
  WalWriter w;                    /* The writer */
  u32 iFirst = 0;                 /* First frame that may be overwritten */
  WalIndexHdr *pLive;             /* Pointer to shared header */

  assert( pList );
  assert( pWal->writeLock );

  /* If this frame set completes a transaction, then nTruncate>0.  If
  ** nTruncate==0 then this frame set does not complete the transaction. */
  assert( (isCommit!=0)==(nTruncate!=0) );

#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
  { int cnt; for(cnt=0, p=pList; p; p=p->pDirty, cnt++){}
    WALTRACE(("WAL%p: frame write begin. %d frames. mxFrame=%d. %s\n",
              pWal, cnt, pWal->hdr.mxFrame, isCommit ? "Commit" : "Spill"));
  }
#endif

  pLive = (WalIndexHdr*)walIndexHdr(pWal);
  if( memcmp(&pWal->hdr, (void *)pLive, sizeof(WalIndexHdr))!=0 ){
    iFirst = pLive->mxFrame+1;
  }

  /* See if it is possible to write these frames into the start of the
  ** log file, instead of appending to it at pWal->hdr.mxFrame.
  */
  if( SQLITE_OK!=(rc = walRestartLog(pWal)) ){
    return rc;
  }

  }
#endif


  /* Write all frames into the log file exactly once */
  for(p=pList; p; p=p->pDirty){
    int nDbSize;   /* 0 normally.  Positive == commit flag */

    /* Check if this page has already been written into the wal file by
    ** the current transaction. If so, overwrite the existing frame and
    ** set Wal.writeLock to WAL_WRITELOCK_RECKSUM - indicating that 
    ** checksums must be recomputed when the transaction is committed.  */
    if( iFirst && (p->pDirty || isCommit==0) ){
      u32 iWrite = 0;
      VVA_ONLY(rc =) sqlite3WalFindFrame(pWal, p->pgno, &iWrite);
      assert( rc==SQLITE_OK || iWrite==0 );
      if( iWrite>=iFirst ){
        i64 iOff = walFrameOffset(iWrite, szPage) + WAL_FRAME_HDRSIZE;
        if( pWal->iReCksum==0 || iWrite<pWal->iReCksum ){
          pWal->iReCksum = iWrite;
        }
        rc = sqlite3OsWrite(pWal->pWalFd, p->pData, szPage, iOff);
        if( rc ) return rc;
        p->flags &= ~PGHDR_WAL_APPEND;
        continue;
      }
    }

    iFrame++;
    assert( iOffset==walFrameOffset(iFrame, szPage) );
    nDbSize = (isCommit && p->pDirty==0) ? nTruncate : 0;
    rc = walWriteOneFrame(&w, p, nDbSize, iOffset);
    if( rc ) return rc;
    pLast = p;
    iOffset += szFrame;
    p->flags |= PGHDR_WAL_APPEND;
  }

  /* Recalculate checksums within the wal file if required. */
  if( isCommit && pWal->iReCksum ){
    rc = walRewriteChecksums(pWal, iFrame);
    if( rc ) return rc;
  }

  /* If this is the end of a transaction, then we might need to pad
  ** the transaction and/or sync the WAL file.
  **
  ** Padding and syncing only occur if this set of frames complete a
  ** transaction and if PRAGMA synchronous=FULL.  If synchronous==NORMAL

  /* Append data to the wal-index. It is not necessary to lock the 
  ** wal-index to do this as the SQLITE_SHM_WRITE lock held on the wal-index
  ** guarantees that there are no other writers, and no data that may
  ** be in use by existing readers is being overwritten.
  */
  iFrame = pWal->hdr.mxFrame;
  for(p=pList; p && rc==SQLITE_OK; p=p->pDirty){
    if( (p->flags & PGHDR_WAL_APPEND)==0 ) continue;
    iFrame++;
    rc = walIndexAppend(pWal, iFrame, p->pgno);
  }
  while( rc==SQLITE_OK && nExtra>0 ){
    iFrame++;
    nExtra--;
    rc = walIndexAppend(pWal, iFrame, pLast->pgno);

    if( isChanged && pWal->pDbFd->pMethods->iVersion>=3 ){
      sqlite3OsUnfetch(pWal->pDbFd, 0, 0);
    }
  }

  /* Copy data from the log to the database file. */
  if( rc==SQLITE_OK ){

    if( pWal->hdr.mxFrame && walPagesize(pWal)!=nBuf ){
      rc = SQLITE_CORRUPT_BKPT;
    }else{
      rc = walCheckpoint(pWal, eMode2, xBusy2, pBusyArg, sync_flags, zBuf);
    }

    /* If no error occurred, set the output variables. */

        zExpSql = argv[++i];
      }else
      if( strcmp(z,"help")==0 ){
        showHelp();
        return 0;
      }else
      if( strcmp(z,"limit-mem")==0 ){
#if !defined(SQLITE_ENABLE_MEMSYS3) && !defined(SQLITE_ENABLE_MEMSYS5)
        fatalError("the %s option requires -DSQLITE_ENABLE_MEMSYS5 or _MEMSYS3",
                   argv[i]);
#else
        if( i>=argc-1 ) fatalError("missing arguments on %s", argv[i]);
        nMem = integerValue(argv[++i]);
#endif
      }else
      if( strcmp(z,"limit-vdbe")==0 ){
        vdbeLimitFlag = 1;
      }else
      if( strcmp(z,"load-sql")==0 ){
        zInsSql = "INSERT INTO xsql(sqltext) VALUES(CAST(readfile(?1) AS text))";
        iFirstInsArg = i+1;

      if {[info exists known_error($x)]} {incr nKnown}
    }
  }
  if {$nKnown>0} {
    output2 "[expr {$nErr-$nKnown}] new errors and $nKnown known errors\
         out of $nTest tests"
  } else {
    set cpuinfo {}
    if {[catch {exec hostname} hname]==0} {set cpuinfo [string trim $hname]}
    append cpuinfo " $::tcl_platform(os)"
    append cpuinfo " [expr {$::tcl_platform(pointerSize)*8}]-bit"
    append cpuinfo " [string map {E -e} $::tcl_platform(byteOrder)]"
    output2 "SQLite [sqlite3 -sourceid]"
    output2 "$nErr errors out of $nTest tests"
    output2 "$nErr errors out of $nTest tests on $cpuinfo"
  }
  if {$nErr>$nKnown} {
    output2 -nonewline "!Failures on these tests:"
    foreach x [set_test_counter fail_list] {
      if {![info exists known_error($x)]} {output2 -nonewline " $x"}
    }
    output2 ""

set x4 abandonint
set x5 babble
set x6 baboon
set x7 backbone
set x8 backarrow
set x9 castle

db func glob gfunc
db func glob -argcount 2 gfunc
proc gfunc {a b} {
  incr ::gfunc
  return 1
}

db func like lfunc
db func like -argcount 2 lfunc
proc lfunc {a b} {
  incr ::gfunc 100
  return 1
}

db func regexp rfunc
db func regexp -argcount 2 rfunc
proc rfunc {a b} {
  incr ::gfunc 10000
  return 1
}

foreach ::tclvar_set_omit {0 1} {
  foreach {tn expr res cnt} {

    SELECT count(*) FROM t1;
    PRAGMA integrity_check;
  }
} {16 ok}
do_test wal-11.6 {
  execsql COMMIT
  list [expr [file size test.db]/1024] [file size test.db-wal]
} [list 3 [wal_file_size 41 1024]]
} [list 3 [wal_file_size 40 1024]]
do_test wal-11.7 {
  execsql { 
    SELECT count(*) FROM t1;
    PRAGMA integrity_check;
  }
} {16 ok}
do_test wal-11.8 {
  execsql { PRAGMA wal_checkpoint }
  list [expr [file size test.db]/1024] [file size test.db-wal]
} [list 37 [wal_file_size 41 1024]]
} [list 37 [wal_file_size 40 1024]]
do_test wal-11.9 {
  ifcapable enable_persist_wal {
    file_control_persist_wal db 0
  }
  db close
  list [expr [file size test.db]/1024] [log_deleted test.db-wal]
} {37 1}
sqlite3_wal db test.db

# After adding the capability of WAL to overwrite prior uncommitted
# frame in the WAL-file with revised content, the size of the WAL file
# following cache-spill is smaller.
#
set nWal 39
if {[permutation]!="mmap"} {set nWal 37}
ifcapable !mmap {set nWal 37}
#set nWal 39
#if {[permutation]!="mmap"} {set nWal 37}
#ifcapable !mmap {set nWal 37}
set nWal 34

ifcapable enable_persist_wal {
  file_control_persist_wal db 0
}
do_test wal-11.10 {
  execsql {
    PRAGMA cache_size = 10;
    BEGIN;

# 2010 May 5
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is testing the operation of the library in
# "PRAGMA journal_mode=WAL" mode.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
source $testdir/wal_common.tcl
set testprefix waloverwrite

ifcapable !wal {finish_test ; return }

# Simple test:
#
# Test cases *.1 - *.6:
#
#   + Create a database of blobs roughly 50 pages in size.
#
#   + Set the db cache size to something much smaller than this (5 pages)
#
#   + Within a transaction, loop through the set of blobs 5 times. Update
#      each blob as it is visited.
#
#   + Test that the wal file is roughly 50 pages in size - even though many
#      database pages have been written to it multiple times.
#
#   + Take a copy of the database and wal file. Test that recovery can
#     be run on it.
#
# Test cases *.7 - *.9:
#
#   + Same thing, but before committing the statement transaction open
#     a SAVEPOINT, update the blobs another 5 times, then roll it back.
#
#   + Check that if recovery is run on the resulting wal file, the rolled
#     back changes from within the SAVEPOINT are not present in the db.
#
# The above is run twice - once where the wal file is empty at the start of
# step 3 (tn==1) and once where it already contains a transaction (tn==2).
#
foreach {tn xtra} {
  1 {}
  2 { UPDATE t1 SET y = randomblob(799) WHERE x=4 }
} {
  reset_db
  do_execsql_test 1.$tn.0 {
    CREATE TABLE t1(x, y);
    CREATE TABLE t2(x, y);
    CREATE INDEX i1y ON t1(y);
  
    WITH cnt(i) AS (
      SELECT 1 UNION ALL SELECT i+1 FROM cnt WHERE i<20
    )
    INSERT INTO t1 SELECT i, randomblob(800) FROM cnt;
  } {}
  
  do_test 1.$tn.1 {
    set nPg [db one { PRAGMA page_count } ]
    expr $nPg>40 && $nPg<50
  } {1}
  
  do_test 1.$tn.2 {
    db close
    sqlite3 db test.db
  
    execsql {PRAGMA journal_mode = wal}
    execsql {PRAGMA cache_size = 5}
    execsql $xtra
  
    db transaction {
      for {set i 0} {$i < 5} {incr i} {
        foreach x [db eval {SELECT x FROM t1}] {
          execsql { UPDATE t1 SET y = randomblob(799) WHERE x=$x }
        }
      }
    }
  
    set nPg [wal_frame_count test.db-wal 1024]
    expr $nPg>40 && $nPg<60
  } {1}
  
  do_execsql_test 1.$tn.3 { PRAGMA integrity_check } ok
  
  do_test 1.$tn.4 {
    forcedelete test.db2 test.db2-wal
    forcecopy test.db test.db2
    sqlite3 db2 test.db2
    execsql { SELECT sum(length(y)) FROM t1 } db2
  } [expr 20*800]
  
  do_test 1.$tn.5 {
    db2 close
    forcecopy test.db test.db2
    forcecopy test.db-wal test.db2-wal
    sqlite3 db2 test.db2
    execsql { SELECT sum(length(y)) FROM t1 } db2
  } [expr 20*799]
  
  do_test 1.$tn.6 {
    execsql { PRAGMA integrity_check } db2
  } ok
  db2 close

  do_test 1.$tn.7 {
    execsql { PRAGMA wal_checkpoint }
    db transaction {
      for {set i 0} {$i < 1} {incr i} {
        foreach x [db eval {SELECT x FROM t1}] {
          execsql { UPDATE t1 SET y = randomblob(798) WHERE x=$x }
        }
      }

      execsql {
        WITH cnt(i) AS (SELECT 1 UNION ALL SELECT i+1 FROM cnt WHERE i<20)
        INSERT INTO t2 SELECT i, randomblob(800) FROM cnt;
      }

      execsql {SAVEPOINT abc}
      for {set i 0} {$i < 5} {incr i} {
        foreach x [db eval {SELECT x FROM t1}] {
          execsql { UPDATE t1 SET y = randomblob(797) WHERE x=$x }
        }
      }
      breakpoint
      execsql {ROLLBACK TO abc}

    }

    set nPg [wal_frame_count test.db-wal 1024]
    expr $nPg>55 && $nPg<75
  } {1}

  do_test 1.$tn.8 {
    forcedelete test.db2 test.db2-wal
    forcecopy test.db test.db2
    sqlite3 db2 test.db2
    execsql { SELECT sum(length(y)) FROM t1 } db2
  } [expr 20*799]

  do_test 1.$tn.9 {
    db2 close
    forcecopy test.db-wal test.db2-wal
    sqlite3 db2 test.db2
    execsql { SELECT sum(length(y)) FROM t1 } db2
  } [expr 20*798]

  do_test 1.$tn.9 {
    execsql { PRAGMA integrity_check } db2
  } ok
  db2 close
}

finish_test