SQLite

  }
  *z = 0;
  assert( (pMem->n+(desiredEnc==SQLITE_UTF8?1:2))<=len );

  sqlite3VdbeMemRelease(pMem);
  pMem->flags &= ~(MEM_Static|MEM_Dyn|MEM_Ephem);
  pMem->enc = desiredEnc;
  pMem->flags |= (MEM_Term);
  pMem->z = (char*)zOut;
  pMem->zMalloc = pMem->z;

translate_out:
#if defined(TRANSLATE_TRACE) && defined(SQLITE_DEBUG)
  {
    char zBuf[100];

  sqlite3VdbeChangeEncoding(&m, SQLITE_UTF8);
  if( db->mallocFailed ){
    sqlite3VdbeMemRelease(&m);
    m.z = 0;
  }
  assert( (m.flags & MEM_Term)!=0 || db->mallocFailed );
  assert( (m.flags & MEM_Str)!=0 || db->mallocFailed );

  assert( m.z || db->mallocFailed );
  return m.z;
}

/*
** zIn is a UTF-16 encoded unicode string at least nChar characters long.
** Return the number of bytes in the first nChar unicode characters

** a pointer to a dynamically allocated string where some other entity
** is responsible for deallocating that string.  Because the register
** does not control the string, it might be deleted without the register
** knowing it.
**
** This routine converts an ephemeral string into a dynamically allocated
** string that the register itself controls.  In other words, it
** converts an MEM_Ephem string into a string with P.z==P.zMalloc.
*/
#define Deephemeralize(P) \
   if( ((P)->flags&MEM_Ephem)!=0 \
       && sqlite3VdbeMemMakeWriteable(P) ){ goto no_mem;}

/* Return true if the cursor was opened using the OP_OpenSorter opcode. */
#define isSorter(x) ((x)->pSorter!=0)

    /* Sanity checking on other operands */
#ifdef SQLITE_DEBUG
    if( (pOp->opflags & OPFLG_IN1)!=0 ){
      assert( pOp->p1>0 );
      assert( pOp->p1<=(p->nMem-p->nCursor) );
      assert( memIsValid(&aMem[pOp->p1]) );
      assert( sqlite3VdbeCheckMemInvariants(&aMem[pOp->p1]) );
      REGISTER_TRACE(pOp->p1, &aMem[pOp->p1]);
    }
    if( (pOp->opflags & OPFLG_IN2)!=0 ){
      assert( pOp->p2>0 );
      assert( pOp->p2<=(p->nMem-p->nCursor) );
      assert( memIsValid(&aMem[pOp->p2]) );
      assert( sqlite3VdbeCheckMemInvariants(&aMem[pOp->p2]) );
      REGISTER_TRACE(pOp->p2, &aMem[pOp->p2]);
    }
    if( (pOp->opflags & OPFLG_IN3)!=0 ){
      assert( pOp->p3>0 );
      assert( pOp->p3<=(p->nMem-p->nCursor) );
      assert( memIsValid(&aMem[pOp->p3]) );
      assert( sqlite3VdbeCheckMemInvariants(&aMem[pOp->p3]) );
      REGISTER_TRACE(pOp->p3, &aMem[pOp->p3]);
    }
    if( (pOp->opflags & OPFLG_OUT2)!=0 ){
      assert( pOp->p2>0 );
      assert( pOp->p2<=(p->nMem-p->nCursor) );
      memAboutToChange(p, &aMem[pOp->p2]);
    }

**
** Write the current address onto register P1
** and then jump to address P2.
*/
case OP_Gosub: {            /* jump */
  assert( pOp->p1>0 && pOp->p1<=(p->nMem-p->nCursor) );
  pIn1 = &aMem[pOp->p1];
  assert( VdbeMemDynamic(pIn1)==0 );
  memAboutToChange(p, pIn1);
  pIn1->flags = MEM_Int;
  pIn1->u.i = pc;
  REGISTER_TRACE(pOp->p1, pIn1);
  pc = pOp->p2 - 1;
  break;
}

** If the co-routine ends with OP_Yield or OP_Return then continue
** to the next instruction.  But if the co-routine ends with
** OP_EndCoroutine, jump immediately to P2.
*/
case OP_Yield: {            /* in1, jump */
  int pcDest;
  pIn1 = &aMem[pOp->p1];
  assert( VdbeMemDynamic(pIn1)==0 );
  pIn1->flags = MEM_Int;
  pcDest = (int)pIn1->u.i;
  pIn1->u.i = pc;
  REGISTER_TRACE(pOp->p1, pIn1);
  pc = pcDest;
  break;
}

#ifndef SQLITE_OMIT_UTF16
  if( encoding!=SQLITE_UTF8 ){
    rc = sqlite3VdbeMemSetStr(pOut, pOp->p4.z, -1, SQLITE_UTF8, SQLITE_STATIC);
    if( rc==SQLITE_TOOBIG ) goto too_big;
    if( SQLITE_OK!=sqlite3VdbeChangeEncoding(pOut, encoding) ) goto no_mem;
    assert( pOut->zMalloc==pOut->z );
    assert( VdbeMemDynamic(pOut)==0 );
    pOut->zMalloc = 0;
    pOut->flags |= MEM_Static;

    if( pOp->p4type==P4_DYNAMIC ){
      sqlite3DbFree(db, pOp->p4.z);
    }
    pOp->p4type = P4_DYNAMIC;
    pOp->p4.z = pOut->z;
    pOp->p1 = pOut->n;
  }

  pIn1 = &aMem[p1];
  pOut = &aMem[p2];
  do{
    assert( pOut<=&aMem[(p->nMem-p->nCursor)] );
    assert( pIn1<=&aMem[(p->nMem-p->nCursor)] );
    assert( memIsValid(pIn1) );
    memAboutToChange(p, pOut);
    VdbeMemRelease(pOut);
    zMalloc = pOut->zMalloc;

    memcpy(pOut, pIn1, sizeof(Mem));
#ifdef SQLITE_DEBUG
    if( pOut->pScopyFrom>=&aMem[p1] && pOut->pScopyFrom<&aMem[p1+pOp->p3] ){
      pOut->pScopyFrom += p1 - pOp->p2;
    }
#endif
    pIn1->flags = MEM_Undefined;
    pIn1->xDel = 0;
    pIn1->zMalloc = zMalloc;
    REGISTER_TRACE(p2++, pOut);
    pIn1++;
    pOut++;
  }while( n-- );
  break;
}

  if( ExpandBlob(pIn1) || ExpandBlob(pIn2) ) goto no_mem;
  Stringify(pIn1, encoding);
  Stringify(pIn2, encoding);
  nByte = pIn1->n + pIn2->n;
  if( nByte>db->aLimit[SQLITE_LIMIT_LENGTH] ){
    goto too_big;
  }

  if( sqlite3VdbeMemGrow(pOut, (int)nByte+2, pOut==pIn2) ){
    goto no_mem;
  }
  MemSetTypeFlag(pOut, MEM_Str);
  if( pOut!=pIn2 ){
    memcpy(pOut->z, pIn2->z, pIn2->n);
  }
  memcpy(&pOut->z[pIn2->n], pIn1->z, pIn1->n);
  pOut->z[nByte]=0;
  pOut->z[nByte+1] = 0;
  pOut->flags |= MEM_Term;

  /* Extract the content for the p2+1-th column.  Control can only
  ** reach this point if aOffset[p2], aOffset[p2+1], and aType[p2] are
  ** all valid.
  */
  assert( p2<pC->nHdrParsed );
  assert( rc==SQLITE_OK );
  assert( sqlite3VdbeCheckMemInvariants(pDest) );
  if( pC->szRow>=aOffset[p2+1] ){
    /* This is the common case where the desired content fits on the original
    ** page - where the content is not on an overflow page */
    VdbeMemRelease(pDest);
    sqlite3VdbeSerialGet(pC->aRow+aOffset[p2], aType[p2], pDest);
  }else{
    /* This branch happens only when content is on overflow pages */

    sqlite3VdbeSerialGet(zData, t, pDest);
    /* If we dynamically allocated space to hold the data (in the
    ** sqlite3VdbeMemFromBtree() call above) then transfer control of that
    ** dynamically allocated space over to the pDest structure.
    ** This prevents a memory copy. */
    if( sMem.zMalloc ){
      assert( sMem.z==sMem.zMalloc );
      assert( VdbeMemDynamic(pDest)==0 );
      assert( (pDest->flags & (MEM_Blob|MEM_Str))==0 || pDest->z==sMem.z );
      pDest->flags &= ~(MEM_Ephem|MEM_Static);
      pDest->flags |= MEM_Term;
      pDest->z = sMem.z;
      pDest->zMalloc = sMem.zMalloc;
    }
  }
  pDest->enc = encoding;

    j += sqlite3VdbeSerialPut(&zNewRecord[j], pRec, serial_type); /* content */
  }while( (++pRec)<=pLast );
  assert( i==nHdr );
  assert( j==nByte );

  assert( pOp->p3>0 && pOp->p3<=(p->nMem-p->nCursor) );
  pOut->n = (int)nByte;
  pOut->flags = MEM_Blob;
  pOut->xDel = 0;
  if( nZero ){
    pOut->u.nZero = nZero;
    pOut->flags |= MEM_Zero;
  }
  pOut->enc = SQLITE_UTF8;  /* In case the blob is ever converted to text */
  REGISTER_TRACE(pOp->p3, pOut);

/* Whenever Mem contains a valid string or blob representation, one of
** the following flags must be set to determine the memory management
** policy for Mem.z.  The MEM_Term flag tells us whether or not the
** string is \000 or \u0000 terminated
*/
#define MEM_Term      0x0200   /* String rep is nul terminated */
#define MEM_Dyn       0x0400   /* Need to call Mem.xDel() on Mem.z */
#define MEM_Static    0x0800   /* Mem.z points to a static string */
#define MEM_Ephem     0x1000   /* Mem.z points to an ephemeral string */
#define MEM_Agg       0x2000   /* Mem.z points to an agg function context */
#define MEM_Zero      0x4000   /* Mem.i contains count of 0s appended to blob */
#ifdef SQLITE_OMIT_INCRBLOB
  #undef MEM_Zero
  #define MEM_Zero 0x0000

#else
# define sqlite3VdbeEnter(X)
# define sqlite3VdbeLeave(X)
#endif

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

#ifndef SQLITE_OMIT_FOREIGN_KEY
int sqlite3VdbeCheckFk(Vdbe *, int);
#else
# define sqlite3VdbeCheckFk(p,i) 0
#endif

      for(pEnd=&p[N]; p<pEnd; p++){
        sqlite3DbFree(db, p->zMalloc);
      }
      return;
    }
    for(pEnd=&p[N]; p<pEnd; p++){
      assert( (&p[1])==pEnd || p[0].db==p[1].db );
      assert( sqlite3VdbeCheckMemInvariants(p) );

      /* This block is really an inlined version of sqlite3VdbeMemRelease()
      ** that takes advantage of the fact that the memory cell value is 
      ** being set to NULL after releasing any dynamic resources.
      **
      ** The justification for duplicating code is that according to 
      ** callgrind, this causes a certain test case to hit the CPU 4.7 

    pMem->memType = MEM_Int;
    pMem++;

    if( sqlite3VdbeMemGrow(pMem, 32, 0) ){            /* P4 */
      assert( p->db->mallocFailed );
      return SQLITE_ERROR;
    }
    pMem->flags = MEM_Str|MEM_Term;
    zP4 = displayP4(pOp, pMem->z, 32);
    if( zP4!=pMem->z ){
      sqlite3VdbeMemSetStr(pMem, zP4, -1, SQLITE_UTF8, 0);
    }else{
      assert( pMem->z!=0 );
      pMem->n = sqlite3Strlen30(pMem->z);
      pMem->enc = SQLITE_UTF8;
    }
    pMem->memType = MEM_Str;
    pMem++;

    if( p->explain==1 ){
      if( sqlite3VdbeMemGrow(pMem, 4, 0) ){
        assert( p->db->mallocFailed );
        return SQLITE_ERROR;
      }
      pMem->flags = MEM_Str|MEM_Term;
      pMem->n = 2;
      sqlite3_snprintf(3, pMem->z, "%.2x", pOp->p5);   /* P5 */
      pMem->memType = MEM_Str;
      pMem->enc = SQLITE_UTF8;
      pMem++;
  
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
      if( sqlite3VdbeMemGrow(pMem, 500, 0) ){
        assert( p->db->mallocFailed );
        return SQLITE_ERROR;
      }
      pMem->flags = MEM_Str|MEM_Term;
      pMem->n = displayComment(pOp, zP4, pMem->z, 500);
      pMem->memType = MEM_Str;
      pMem->enc = SQLITE_UTF8;
#else
      pMem->flags = MEM_Null;                       /* Comment */
      pMem->memType = MEM_Null;
#endif

** This file contains code use to manipulate "Mem" structure.  A "Mem"
** stores a single value in the VDBE.  Mem is an opaque structure visible
** only within the VDBE.  Interface routines refer to a Mem using the
** name sqlite_value
*/
#include "sqliteInt.h"
#include "vdbeInt.h"

#ifdef SQLITE_DEBUG
/*
** Check invariants on a Mem object.
**
** This routine is intended for use inside of assert() statements, like
** this:    assert( sqlite3VdbeCheckMemInvariants(pMem) );
*/
int sqlite3VdbeCheckMemInvariants(Mem *p){
  /* The MEM_Dyn bit is set if and only if Mem.xDel is a non-NULL destructor
  ** function for Mem.z 
  */
  assert( (p->flags & MEM_Dyn)==0 || p->xDel!=0 );
  assert( (p->flags & MEM_Dyn)!=0 || p->xDel==0 );

  /* If p holds a string or blob, the Mem.z must point to exactly
  ** one of the following:
  **
  **   (1) Memory in Mem.zMalloc and managed by the Mem object
  **   (2) Memory to be freed using Mem.xDel
  **   (3) An ephermal string or blob
  **   (4) A static string or blob
  */
  if( (p->flags & (MEM_Str|MEM_Blob)) && p->z!=0 ){
    assert( 
      ((p->z==p->zMalloc)? 1 : 0) +
      ((p->flags&MEM_Dyn)!=0 ? 1 : 0) +
      ((p->flags&MEM_Ephem)!=0 ? 1 : 0) +
      ((p->flags&MEM_Static)!=0 ? 1 : 0) == 1
    );
  }

  return 1;
}
#endif


/*
** If pMem is an object with a valid string representation, this routine
** ensures the internal encoding for the string representation is
** 'desiredEnc', one of SQLITE_UTF8, SQLITE_UTF16LE or SQLITE_UTF16BE.
**
** If pMem is not a string object, or the encoding of the string

**
** If the bPreserve argument is true, then copy of the content of
** pMem->z into the new allocation.  pMem must be either a string or
** blob if bPreserve is true.  If bPreserve is false, any prior content
** in pMem->z is discarded.
*/
int sqlite3VdbeMemGrow(Mem *pMem, int n, int bPreserve){
  assert( sqlite3VdbeCheckMemInvariants(pMem) );





  assert( (pMem->flags&MEM_RowSet)==0 );

  /* If the bPreserve flag is set to true, then the memory cell must already
  ** contain a valid string or blob value.  */
  assert( bPreserve==0 || pMem->flags&(MEM_Blob|MEM_Str) );
  testcase( bPreserve && pMem->z==0 );

  if( pMem->zMalloc==0 || sqlite3DbMallocSize(pMem->db, pMem->zMalloc)<n ){
    if( n<32 ) n = 32;
    if( bPreserve && pMem->z==pMem->zMalloc ){
      pMem->z = pMem->zMalloc = sqlite3DbReallocOrFree(pMem->db, pMem->z, n);
      bPreserve = 0;
    }else{
      sqlite3DbFree(pMem->db, pMem->zMalloc);
      pMem->zMalloc = sqlite3DbMallocRaw(pMem->db, n);
    }
    if( pMem->zMalloc==0 ){
      VdbeMemRelease(pMem);
      pMem->flags = MEM_Null;  
      return SQLITE_NOMEM;
    }
  }

  if( pMem->z && bPreserve && pMem->z!=pMem->zMalloc ){
    memcpy(pMem->zMalloc, pMem->z, pMem->n);
  }
  if( (pMem->flags&MEM_Dyn)!=0 ){
    assert( pMem->xDel!=0 && pMem->xDel!=SQLITE_DYNAMIC );
    pMem->xDel((void *)(pMem->z));
  }

  pMem->z = pMem->zMalloc;
  pMem->flags &= ~(MEM_Dyn|MEM_Ephem|MEM_Static);
  pMem->xDel = 0;
  return SQLITE_OK;
}

/*
** Make the given Mem object MEM_Dyn.  In other words, make it so
** that any TEXT or BLOB content is stored in memory obtained from

*/
void sqlite3VdbeMemReleaseExternal(Mem *p){
  assert( p->db==0 || sqlite3_mutex_held(p->db->mutex) );
  if( p->flags&MEM_Agg ){
    sqlite3VdbeMemFinalize(p, p->u.pDef);
    assert( (p->flags & MEM_Agg)==0 );
    sqlite3VdbeMemRelease(p);
  }else if( p->flags&MEM_Dyn ){
    assert( (p->flags&MEM_RowSet)==0 );
    assert( p->xDel!=SQLITE_DYNAMIC && p->xDel!=0 );
    p->xDel((void *)p->z);
    p->xDel = 0;
  }else if( p->flags&MEM_RowSet ){
    sqlite3RowSetClear(p->u.pRowSet);
  }else if( p->flags&MEM_Frame ){
    sqlite3VdbeMemSetNull(p);
  }
}

/*
** Release any memory held by the Mem. This may leave the Mem in an
** inconsistent state, for example with (Mem.z==0) and
** (Mem.memType==MEM_Str).
*/
void sqlite3VdbeMemRelease(Mem *p){
  assert( sqlite3VdbeCheckMemInvariants(p) );
  VdbeMemRelease(p);
  if( p->zMalloc ){
    sqlite3DbFree(p->db, p->zMalloc);
    p->zMalloc = 0;
  }
  p->z = 0;
  assert( p->xDel==0 );  /* Zeroed by VdbeMemRelease() above */

int sqlite3VdbeMemCopy(Mem *pTo, const Mem *pFrom){
  int rc = SQLITE_OK;

  assert( (pFrom->flags & MEM_RowSet)==0 );
  VdbeMemRelease(pTo);
  memcpy(pTo, pFrom, MEMCELLSIZE);
  pTo->flags &= ~MEM_Dyn;
  pTo->xDel = 0;

  if( pTo->flags&(MEM_Str|MEM_Blob) ){
    if( 0==(pFrom->flags&MEM_Static) ){
      pTo->flags |= MEM_Ephem;
      rc = sqlite3VdbeMemMakeWriteable(pTo);
    }
  }

  assert( zData!=0 );

  if( offset+amt<=available ){
    sqlite3VdbeMemRelease(pMem);
    pMem->z = &zData[offset];
    pMem->flags = MEM_Blob|MEM_Ephem;
  }else if( SQLITE_OK==(rc = sqlite3VdbeMemGrow(pMem, amt+2, 0)) ){
    pMem->flags = MEM_Blob|MEM_Term;
    pMem->enc = 0;
    pMem->memType = MEM_Blob;
    if( key ){
      rc = sqlite3BtreeKey(pCur, offset, amt, pMem->z);
    }else{
      rc = sqlite3BtreeData(pCur, offset, amt, pMem->z);
    }