mask = sqlite4_context_appdata(context)==0 ? 0 : -1;
  pColl = sqlite4GetFuncCollSeq(context);
  assert( pColl );
  assert( mask==-1 || mask==0 );
  iBest = 0;
  if( sqlite4_value_type(argv[0])==SQLITE4_NULL ) return;
  for(i=1; i<argc; i++){

    if( sqlite4_value_type(argv[i])==SQLITE4_NULL ) return;
    if( (sqlite4MemCompare(argv[iBest], argv[i], pColl)^mask)>=0 ){





      testcase( mask==0 );
      iBest = i;
    }
  }
  sqlite4_result_value(context, argv[iBest]);
}

................................................................................
** arguments are equal to each other.
*/
static void nullifFunc(
  sqlite4_context *context,
  int NotUsed,
  sqlite4_value **argv
){

  CollSeq *pColl = sqlite4GetFuncCollSeq(context);
  UNUSED_PARAMETER(NotUsed);
  if( sqlite4MemCompare(argv[0], argv[1], pColl)!=0 ){



    sqlite4_result_value(context, argv[0]);
  }
}

/*
** Implementation of the sqlite_version() function.  The result is the version
** of the SQLite library that is running.
................................................................................
  if( sqlite4_value_type(argv[0])==SQLITE4_NULL ) return;
  pBest = (Mem *)sqlite4_aggregate_context(context, sizeof(*pBest));
  if( !pBest ) return;

  if( pBest->flags ){
    int max;
    int cmp;

    CollSeq *pColl = sqlite4GetFuncCollSeq(context);
    /* This step function is used for both the min() and max() aggregates,
    ** the only difference between the two being that the sense of the
    ** comparison is inverted. For the max() aggregate, the
    ** sqlite4_context_appdata() function returns (void *)-1. For min() it
    ** returns (void *)db, where db is the sqlite4* database pointer.
    ** Therefore the next statement sets variable 'max' to 1 for the max()
    ** aggregate, or 0 for min().
    */
    max = sqlite4_context_appdata(context)!=0;
    cmp = sqlite4MemCompare(pBest, pArg, pColl);




    if( (max && cmp<0) || (!max && cmp>0) ){
      sqlite4VdbeMemCopy(pBest, pArg);
    }
  }else{
    sqlite4VdbeMemCopy(pBest, pArg);
  }
}

  mask = sqlite4_context_appdata(context)==0 ? 0 : -1;
  pColl = sqlite4GetFuncCollSeq(context);
  assert( pColl );
  assert( mask==-1 || mask==0 );
  iBest = 0;
  if( sqlite4_value_type(argv[0])==SQLITE4_NULL ) return;
  for(i=1; i<argc; i++){
    int res, rc;
    if( sqlite4_value_type(argv[i])==SQLITE4_NULL ) return;
    rc = sqlite4MemCompare(argv[iBest], argv[i], pColl, &res);
    if( rc!=SQLITE4_OK ){
      sqlite4_result_error_code(context, rc);
      return;
    }
    if( (res^mask)>=0 ){
      testcase( mask==0 );
      iBest = i;
    }
  }
  sqlite4_result_value(context, argv[iBest]);
}

................................................................................
** arguments are equal to each other.
*/
static void nullifFunc(
  sqlite4_context *context,
  int NotUsed,
  sqlite4_value **argv
){
  int rc, res;
  CollSeq *pColl = sqlite4GetFuncCollSeq(context);
  UNUSED_PARAMETER(NotUsed);
  rc = sqlite4MemCompare(argv[0], argv[1], pColl, &res);
  if( rc!=SQLITE4_OK ){
    sqlite4_result_error_code(context, rc);
  }else if( res ){
    sqlite4_result_value(context, argv[0]);
  }
}

/*
** Implementation of the sqlite_version() function.  The result is the version
** of the SQLite library that is running.
................................................................................
  if( sqlite4_value_type(argv[0])==SQLITE4_NULL ) return;
  pBest = (Mem *)sqlite4_aggregate_context(context, sizeof(*pBest));
  if( !pBest ) return;

  if( pBest->flags ){
    int max;
    int cmp;
    int rc;
    CollSeq *pColl = sqlite4GetFuncCollSeq(context);
    /* This step function is used for both the min() and max() aggregates,
    ** the only difference between the two being that the sense of the
    ** comparison is inverted. For the max() aggregate, the
    ** sqlite4_context_appdata() function returns (void *)-1. For min() it
    ** returns (void *)db, where db is the sqlite4* database pointer.
    ** Therefore the next statement sets variable 'max' to 1 for the max()
    ** aggregate, or 0 for min().
    */
    max = sqlite4_context_appdata(context)!=0;
    rc = sqlite4MemCompare(pBest, pArg, pColl, &cmp);
    if( rc!=SQLITE4_OK ){
      sqlite4_result_error_code(context, rc);
      return;
    }
    if( (max && cmp<0) || (!max && cmp>0) ){
      sqlite4VdbeMemCopy(pBest, pArg);
    }
  }else{
    sqlite4VdbeMemCopy(pBest, pArg);
  }
}

**
** If the padFlag argument is not NULL then space padding at the end
** of strings is ignored.  This implements the RTRIM collation.
*/
static int binCollFunc(
  void *padFlag,
  int nKey1, const void *pKey1,
  int nKey2, const void *pKey2

){
  int rc, n;
  n = nKey1<nKey2 ? nKey1 : nKey2;
  rc = memcmp(pKey1, pKey2, n);
  if( rc==0 ){
    if( padFlag
     && allSpaces(((char*)pKey1)+n, nKey1-n)
     && allSpaces(((char*)pKey2)+n, nKey2-n)
    ){
      /* Leave rc unchanged at 0 */
    }else{
      rc = nKey1 - nKey2;
    }
  }

  return rc;
}

/*
** The xMakeKey callback for the built-in RTRIM collation. The output
** is the same as the input, with any trailing ' ' characters removed.
** (e.g.  " abc   "  ->   " abc").
*/
................................................................................
** extends only to the 26 characters used in the English language.
**
** At the moment there is only a UTF-8 implementation.
*/
static int collNocaseCmp(
  void *NotUsed,
  int nKey1, const void *pKey1,
  int nKey2, const void *pKey2

){
  int r = sqlite4_strnicmp(
      (const char *)pKey1, (const char *)pKey2, (nKey1<nKey2)?nKey1:nKey2);
  UNUSED_PARAMETER(NotUsed);
  if( 0==r ){
    r = nKey1-nKey2;
  }

  return r;
}

static int collNocaseMkKey(
  void *NotUsed,
  int nIn, const void *pKey1,
  int nOut, void *pKey2
){
................................................................................
** and the encoding is enc.
*/
static int createCollation(
  sqlite4* db,
  const char *zName, 
  u8 enc,
  void* pCtx,
  int(*xCompare)(void*,int,const void*,int,const void*),
  int(*xMakeKey)(void*,int,const void*,int,void*),
  void(*xDel)(void*)
){
  CollSeq *pColl;
  int enc2;
  int nName = sqlite4Strlen30(zName);
  
................................................................................
** Register a new collation sequence with the database handle db.
*/
int sqlite4_create_collation(
  sqlite4* db, 
  const char *zName, 
  int enc, 
  void* pCtx,
  int(*xCompare)(void*,int,const void*,int,const void*),
  int(*xMakeKey)(void*,int,const void*,int,void*),
  void(*xDel)(void*)
){
  int rc;
  sqlite4_mutex_enter(db->mutex);
  assert( !db->mallocFailed );
  rc = createCollation(db, zName, (u8)enc, pCtx, xCompare, xMakeKey, xDel);

**
** If the padFlag argument is not NULL then space padding at the end
** of strings is ignored.  This implements the RTRIM collation.
*/
static int binCollFunc(
  void *padFlag,
  int nKey1, const void *pKey1,
  int nKey2, const void *pKey2,
  int *pRes
){
  int res, n;
  n = nKey1<nKey2 ? nKey1 : nKey2;
  res = memcmp(pKey1, pKey2, n);
  if( res==0 ){
    if( padFlag
     && allSpaces(((char*)pKey1)+n, nKey1-n)
     && allSpaces(((char*)pKey2)+n, nKey2-n)
    ){
      /* Leave res unchanged at 0 */
    }else{
      res = nKey1 - nKey2;
    }
  }
  *pRes = res;
  return SQLITE4_OK;
}

/*
** The xMakeKey callback for the built-in RTRIM collation. The output
** is the same as the input, with any trailing ' ' characters removed.
** (e.g.  " abc   "  ->   " abc").
*/
................................................................................
** extends only to the 26 characters used in the English language.
**
** At the moment there is only a UTF-8 implementation.
*/
static int collNocaseCmp(
  void *NotUsed,
  int nKey1, const void *pKey1,
  int nKey2, const void *pKey2,
  int *pRes
){
  int r = sqlite4_strnicmp(
      (const char *)pKey1, (const char *)pKey2, (nKey1<nKey2)?nKey1:nKey2);
  UNUSED_PARAMETER(NotUsed);
  if( 0==r ){
    r = nKey1-nKey2;
  }
  *pRes = r;
  return SQLITE4_OK;
}

static int collNocaseMkKey(
  void *NotUsed,
  int nIn, const void *pKey1,
  int nOut, void *pKey2
){
................................................................................
** and the encoding is enc.
*/
static int createCollation(
  sqlite4* db,
  const char *zName, 
  u8 enc,
  void* pCtx,
  int(*xCompare)(void*,int,const void*,int,const void*,int*),
  int(*xMakeKey)(void*,int,const void*,int,void*),
  void(*xDel)(void*)
){
  CollSeq *pColl;
  int enc2;
  int nName = sqlite4Strlen30(zName);
  
................................................................................
** Register a new collation sequence with the database handle db.
*/
int sqlite4_create_collation(
  sqlite4* db, 
  const char *zName, 
  int enc, 
  void* pCtx,
  int(*xCompare)(void*,int,const void*,int,const void*,int*),
  int(*xMakeKey)(void*,int,const void*,int,void*),
  void(*xDel)(void*)
){
  int rc;
  sqlite4_mutex_enter(db->mutex);
  assert( !db->mallocFailed );
  rc = createCollation(db, zName, (u8)enc, pCtx, xCompare, xMakeKey, xDel);

** See also:  [sqlite4_collation_needed()] and [sqlite4_collation_needed16()].
*/
int sqlite4_create_collation(
  sqlite4*, 
  const char *zName, 
  int eTextRep, 
  void *pArg,
  int(*xCompare)(void*,int,const void*,int,const void*),
  int(*xMakeKey)(void*,int,const void*,int,void*),
  void(*xDestroy)(void*)
);

/*
** CAPIREF: Collation Needed Callbacks
**
................................................................................
** sqlite4_collation_needed16().  The second argument is the database
** connection.  The third argument is one of [SQLITE4_UTF8], [SQLITE4_UTF16BE],
** or [SQLITE4_UTF16LE], indicating the most desirable form of the collation
** sequence function required.  The fourth parameter is the name of the
** required collation sequence.)^
**
** The callback function should register the desired collation using
** [sqlite4_create_collation()], [sqlite4_create_collation16()], or
** [sqlite4_create_collation_v2()].
*/
int sqlite4_collation_needed(
  sqlite4*, 
  void(*)(void*,sqlite4*,int eTextRep,const char*),
  void* 
);
int sqlite4_collation_needed16(

** See also:  [sqlite4_collation_needed()] and [sqlite4_collation_needed16()].
*/
int sqlite4_create_collation(
  sqlite4*, 
  const char *zName, 
  int eTextRep, 
  void *pArg,
  int(*xCompare)(void*,int,const void*,int,const void*,int*),
  int(*xMakeKey)(void*,int,const void*,int,void*),
  void(*xDestroy)(void*)
);

/*
** CAPIREF: Collation Needed Callbacks
**
................................................................................
** sqlite4_collation_needed16().  The second argument is the database
** connection.  The third argument is one of [SQLITE4_UTF8], [SQLITE4_UTF16BE],
** or [SQLITE4_UTF16LE], indicating the most desirable form of the collation
** sequence function required.  The fourth parameter is the name of the
** required collation sequence.)^
**
** The callback function should register the desired collation using

** [sqlite4_create_collation()].
*/
int sqlite4_collation_needed(
  sqlite4*, 
  void(*)(void*,sqlite4*,int eTextRep,const char*),
  void* 
);
int sqlite4_collation_needed16(

** collating sequence is undefined.  Indices built on an undefined
** collating sequence may not be read or written.
*/
struct CollSeq {
  char *zName;          /* Name of the collating sequence, UTF-8 encoded */
  u8 enc;               /* Text encoding handled by xCmp() */
  void *pUser;          /* First argument to xCmp() */
  int (*xCmp)(void*,int, const void*, int, const void*);
  int (*xMkKey)(void*,int, const void*, int, void*);
  void (*xDel)(void*);  /* Destructor for pUser */
};

/*
** A sort order can be either ASC or DESC.
*/

** collating sequence is undefined.  Indices built on an undefined
** collating sequence may not be read or written.
*/
struct CollSeq {
  char *zName;          /* Name of the collating sequence, UTF-8 encoded */
  u8 enc;               /* Text encoding handled by xCmp() */
  void *pUser;          /* First argument to xCmp() */
  int (*xCmp)(void*,int, const void*, int, const void*, int *);
  int (*xMkKey)(void*,int, const void*, int, void*);
  void (*xDel)(void*);  /* Destructor for pUser */
};

/*
** A sort order can be either ASC or DESC.
*/

** using TCL script.
*/
static int tclSqlCollate(
  void *pCtx,
  int nA,
  const void *zA,
  int nB,
  const void *zB

){
  SqlCollate *p = (SqlCollate *)pCtx;
  Tcl_Obj *pCmd;


  pCmd = Tcl_NewStringObj(p->zCmp, -1);
  Tcl_IncrRefCount(pCmd);
  Tcl_ListObjAppendElement(p->interp, pCmd, Tcl_NewStringObj(zA, nA));
  Tcl_ListObjAppendElement(p->interp, pCmd, Tcl_NewStringObj(zB, nB));
  Tcl_EvalObjEx(p->interp, pCmd, TCL_EVAL_DIRECT);
  Tcl_DecrRefCount(pCmd);
  return (atoi(Tcl_GetStringResult(p->interp)));

}

static int tclSqlMkkey(
  void *pCtx,
  int nIn,
  const void *zIn,
  int nOut,

** using TCL script.
*/
static int tclSqlCollate(
  void *pCtx,
  int nA,
  const void *zA,
  int nB,
  const void *zB,
  int *pRes
){
  SqlCollate *p = (SqlCollate *)pCtx;
  Tcl_Obj *pCmd;
  int rc;

  pCmd = Tcl_NewStringObj(p->zCmp, -1);
  Tcl_IncrRefCount(pCmd);
  Tcl_ListObjAppendElement(p->interp, pCmd, Tcl_NewStringObj(zA, nA));
  Tcl_ListObjAppendElement(p->interp, pCmd, Tcl_NewStringObj(zB, nB));
  rc = Tcl_EvalObjEx(p->interp, pCmd, TCL_EVAL_DIRECT);
  Tcl_DecrRefCount(pCmd);
  *pRes = (atoi(Tcl_GetStringResult(p->interp)));
  return (rc==TCL_OK ? SQLITE4_OK : SQLITE4_ERROR);
}

static int tclSqlMkkey(
  void *pCtx,
  int nIn,
  const void *zIn,
  int nOut,

    if( affinity ){
      applyAffinity(pIn1, affinity, encoding);
      applyAffinity(pIn3, affinity, encoding);
      if( db->mallocFailed ) goto no_mem;
    }

    assert( pOp->p4type==P4_COLLSEQ || pOp->p4.pColl==0 );
    res = sqlite4MemCompare(pIn3, pIn1, pOp->p4.pColl);
  }
  switch( pOp->opcode ){
    case OP_Eq:    res = res==0;     break;
    case OP_Ne:    res = res!=0;     break;
    case OP_Lt:    res = res<0;      break;
    case OP_Le:    res = res<=0;     break;
    case OP_Gt:    res = res>0;      break;
................................................................................
    assert( memIsValid(&aMem[p1+idx]) );
    assert( memIsValid(&aMem[p2+idx]) );
    REGISTER_TRACE(p1+idx, &aMem[p1+idx]);
    REGISTER_TRACE(p2+idx, &aMem[p2+idx]);
    assert( i<pKeyInfo->nField );
    pColl = pKeyInfo->aColl[i];
    bRev = pKeyInfo->aSortOrder[i];
    iCompare = sqlite4MemCompare(&aMem[p1+idx], &aMem[p2+idx], pColl);
    if( iCompare ){
      if( bRev ) iCompare = -iCompare;
      break;
    }
  }
  aPermute = 0;
  break;

    if( affinity ){
      applyAffinity(pIn1, affinity, encoding);
      applyAffinity(pIn3, affinity, encoding);
      if( db->mallocFailed ) goto no_mem;
    }

    assert( pOp->p4type==P4_COLLSEQ || pOp->p4.pColl==0 );
    rc = sqlite4MemCompare(pIn3, pIn1, pOp->p4.pColl, &res);
  }
  switch( pOp->opcode ){
    case OP_Eq:    res = res==0;     break;
    case OP_Ne:    res = res!=0;     break;
    case OP_Lt:    res = res<0;      break;
    case OP_Le:    res = res<=0;     break;
    case OP_Gt:    res = res>0;      break;
................................................................................
    assert( memIsValid(&aMem[p1+idx]) );
    assert( memIsValid(&aMem[p2+idx]) );
    REGISTER_TRACE(p1+idx, &aMem[p1+idx]);
    REGISTER_TRACE(p2+idx, &aMem[p2+idx]);
    assert( i<pKeyInfo->nField );
    pColl = pKeyInfo->aColl[i];
    bRev = pKeyInfo->aSortOrder[i];
    rc = sqlite4MemCompare(&aMem[p1+idx], &aMem[p2+idx], pColl, &iCompare);
    if( iCompare ){
      if( bRev ) iCompare = -iCompare;
      break;
    }
  }
  aPermute = 0;
  break;

  u8 **pzOut,                  /* Write the resulting key here */
  int *pnOut,                  /* Number of bytes in the key */
  int nExtra                   /* Append extra bytes on end of key */
);
int sqlite4VdbeEncodeIntKey(u8 *aBuf,sqlite4_int64 v);
int sqlite4VdbeDecodeIntKey(const KVByteArray*, KVSize, sqlite4_int64*);
int sqlite4VdbeShortKey(const u8 *, int, int);
int sqlite4MemCompare(const Mem*, const Mem*, const CollSeq*);
int sqlite4VdbeExec(Vdbe*);
int sqlite4VdbeList(Vdbe*);
int sqlite4VdbeHalt(Vdbe*);
int sqlite4VdbeChangeEncoding(Mem *, int);
int sqlite4VdbeMemTooBig(Mem*);
int sqlite4VdbeMemCopy(Mem*, const Mem*);
void sqlite4VdbeMemShallowCopy(Mem*, const Mem*, int);

  u8 **pzOut,                  /* Write the resulting key here */
  int *pnOut,                  /* Number of bytes in the key */
  int nExtra                   /* Append extra bytes on end of key */
);
int sqlite4VdbeEncodeIntKey(u8 *aBuf,sqlite4_int64 v);
int sqlite4VdbeDecodeIntKey(const KVByteArray*, KVSize, sqlite4_int64*);
int sqlite4VdbeShortKey(const u8 *, int, int);
int sqlite4MemCompare(const Mem*, const Mem*, const CollSeq*,int*);
int sqlite4VdbeExec(Vdbe*);
int sqlite4VdbeList(Vdbe*);
int sqlite4VdbeHalt(Vdbe*);
int sqlite4VdbeChangeEncoding(Mem *, int);
int sqlite4VdbeMemTooBig(Mem*);
int sqlite4VdbeMemCopy(Mem*, const Mem*);
void sqlite4VdbeMemShallowCopy(Mem*, const Mem*, int);

** negative, zero or positive if pMem1 is less than, equal to, or greater
** than pMem2. Sorting order is NULL's first, followed by numbers (integers
** and reals) sorted numerically, followed by text ordered by the collating
** sequence pColl and finally blob's ordered by memcmp().
**
** Two NULL values are considered equal by this function.
*/
int sqlite4MemCompare(const Mem *pMem1, const Mem *pMem2, const CollSeq *pColl){





  int rc;
  int f1, f2;
  int combined_flags;

  f1 = pMem1->flags;
  f2 = pMem2->flags;
  combined_flags = f1|f2;
  assert( (combined_flags & MEM_RowSet)==0 );
 
  /* If one value is NULL, it is less than the other. If both values
  ** are NULL, return 0.
  */
  if( combined_flags&MEM_Null ){
    return (f2&MEM_Null) - (f1&MEM_Null);

  }

  /* If one value is a number and the other is not, the number is less.
  ** If both are numbers, compare as reals if one is a real, or as integers
  ** if both values are integers.
  */
  if( combined_flags&(MEM_Int|MEM_Real) ){
    if( !(f1&(MEM_Int|MEM_Real)) ) return 1;

    if( !(f2&(MEM_Int|MEM_Real)) ) return -1;


    return (sqlite4_num_compare(pMem1->u.num, pMem2->u.num) - 2);


  }

  /* If one value is a string and the other is a blob, the string is less.
  ** If both are strings, compare using the collating functions.
  */
  if( combined_flags&MEM_Str ){
    if( (f1 & MEM_Str)==0 ){
      return 1;
    }
    if( (f2 & MEM_Str)==0 ){
      return -1;


    }

    assert( pMem1->enc==pMem2->enc );
    assert( pMem1->enc==SQLITE4_UTF8 || 
            pMem1->enc==SQLITE4_UTF16LE || pMem1->enc==SQLITE4_UTF16BE );

    /* The collation sequence must be defined at this point, even if
    ** the user deletes the collation sequence after the vdbe program is
    ** compiled (this was not always the case).
    */
    assert( !pColl || pColl->xCmp );

    if( pColl ){

      if( pMem1->enc==pColl->enc ){
        /* The strings are already in the correct encoding.  Call the
        ** comparison function directly */
        return pColl->xCmp(pColl->pUser,pMem1->n,pMem1->z,pMem2->n,pMem2->z);
      }else{
        const void *v1, *v2;
        int n1, n2;
        Mem c1;
        Mem c2;
        memset(&c1, 0, sizeof(c1));
        memset(&c2, 0, sizeof(c2));
        sqlite4VdbeMemShallowCopy(&c1, pMem1, MEM_Ephem);
        sqlite4VdbeMemShallowCopy(&c2, pMem2, MEM_Ephem);
        v1 = sqlite4ValueText((sqlite4_value*)&c1, pColl->enc);
        n1 = v1==0 ? 0 : c1.n;
        v2 = sqlite4ValueText((sqlite4_value*)&c2, pColl->enc);
        n2 = v2==0 ? 0 : c2.n;
        rc = pColl->xCmp(pColl->pUser, n1, v1, n2, v2);
        sqlite4VdbeMemRelease(&c1);
        sqlite4VdbeMemRelease(&c2);
        return rc;
      }
    }
    /* If a NULL pointer was passed as the collate function, fall through
    ** to the blob case and use memcmp().  */
  }
 
  /* Both values must be blobs.  Compare using memcmp().  */
  rc = memcmp(pMem1->z, pMem2->z, (pMem1->n>pMem2->n)?pMem2->n:pMem1->n);
  if( rc==0 ){
    rc = pMem1->n - pMem2->n;
  }
  return rc;
}

/* This function is only available internally, it is not part of the
** external API. It works in a similar way to sqlite4_value_text(),
** except the data returned is in the encoding specified by the second

** negative, zero or positive if pMem1 is less than, equal to, or greater
** than pMem2. Sorting order is NULL's first, followed by numbers (integers
** and reals) sorted numerically, followed by text ordered by the collating
** sequence pColl and finally blob's ordered by memcmp().
**
** Two NULL values are considered equal by this function.
*/
int sqlite4MemCompare(
  const Mem *pMem1, 
  const Mem *pMem2, 
  const CollSeq *pColl,
  int *pRes                       /* OUT: Result of comparison operation */
){
  int rc = SQLITE4_OK;
  int f1, f2;
  int combined_flags;

  f1 = pMem1->flags;
  f2 = pMem2->flags;
  combined_flags = f1|f2;
  assert( (combined_flags & MEM_RowSet)==0 );
 
  /* If one value is NULL, it is less than the other. If both values
  ** are NULL, return 0.
  */
  if( combined_flags&MEM_Null ){
    *pRes = (f2&MEM_Null) - (f1&MEM_Null);
    return SQLITE4_OK;
  }

  /* If one value is a number and the other is not, the number is less.
  ** If both are numbers, compare as reals if one is a real, or as integers
  ** if both values are integers.
  */
  if( combined_flags&(MEM_Int|MEM_Real) ){
    if( !(f1&(MEM_Int|MEM_Real)) ){
      *pRes = 1;
    }else if( !(f2&(MEM_Int|MEM_Real)) ){
      *pRes = -1;
    }else{
      *pRes = (sqlite4_num_compare(pMem1->u.num, pMem2->u.num) - 2);
    }
    return SQLITE4_OK;
  }

  /* If one value is a string and the other is a blob, the string is less.
  ** If both are strings, compare using the collating functions.
  */
  if( combined_flags&MEM_Str ){

    if( (f1 & f2 & MEM_Str)==0 ){
      /* This branch is taken if one of the values is not a string. So, if
      ** f1 is a string, then f2 must be a blob. Return -1. Otherwise,
      ** if f2 is a string and f1 is a blob, return +1.  */
      *pRes = (f1 & MEM_Str) ? -1 : +1;
      return SQLITE4_OK;
    }

    assert( pMem1->enc==pMem2->enc );
    assert( pMem1->enc==SQLITE4_UTF8 || 
            pMem1->enc==SQLITE4_UTF16LE || pMem1->enc==SQLITE4_UTF16BE );

    /* The collation sequence must be defined at this point, even if
    ** the user deletes the collation sequence after the vdbe program is
    ** compiled (this was not always the case).
    */
    assert( !pColl || pColl->xCmp );

    if( pColl ){
      void *pUser = pColl->pUser;
      if( pMem1->enc==pColl->enc ){
        /* The strings are already in the correct encoding.  Call the
        ** comparison function directly */
        return pColl->xCmp(pUser, pMem1->n, pMem1->z, pMem2->n, pMem2->z, pRes);
      }else{
        const void *v1, *v2;
        int n1, n2;
        Mem c1;
        Mem c2;
        memset(&c1, 0, sizeof(c1));
        memset(&c2, 0, sizeof(c2));
        sqlite4VdbeMemShallowCopy(&c1, pMem1, MEM_Ephem);
        sqlite4VdbeMemShallowCopy(&c2, pMem2, MEM_Ephem);
        v1 = sqlite4ValueText((sqlite4_value*)&c1, pColl->enc);
        n1 = v1==0 ? 0 : c1.n;
        v2 = sqlite4ValueText((sqlite4_value*)&c2, pColl->enc);
        n2 = v2==0 ? 0 : c2.n;
        rc = pColl->xCmp(pUser, n1, v1, n2, v2, pRes);
        sqlite4VdbeMemRelease(&c1);
        sqlite4VdbeMemRelease(&c2);
        return rc;
      }
    }
    /* If a NULL pointer was passed as the collate function, fall through
    ** to the blob case and use memcmp().  */
  }
 
  /* Both values must be blobs.  Compare using memcmp().  */
  *pRes = memcmp(pMem1->z, pMem2->z, (pMem1->n>pMem2->n)?pMem2->n:pMem1->n);
  if( *pRes==0 ){
    *pRes = pMem1->n - pMem2->n;
  }
  return rc;
}

/* This function is only available internally, it is not part of the
** external API. It works in a similar way to sqlite4_value_text(),
** except the data returned is in the encoding specified by the second

#
# 2001 September 15
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this test is errors returned by collation sequence comparison
# functions.

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set ::testprefix collateerr

db collate xxx xxx_collate xxx_mkkey

proc xxx_collate {a b} { return [string compare $a $b] }
proc xxx_mkkey {a}     { return $a }

do_execsql_test 1.0 {
  CREATE TABLE t1(a COLLATE xxx, b COLLATE xxx);
  INSERT INTO t1 VALUES('abc', 'def');
  INSERT INTO t1 VALUES('jkl', 'ghi');
}

foreach {tn sql res} {
  1 { SELECT max(a, b) FROM t1 }   {def jkl} 
  2 { SELECT max(a) FROM t1 }      {jkl} 
  3 { SELECT nullif(a,b) FROM t1 } {abc jkl} 
  4 { SELECT a==b FROM t1 }        {0 0}
} {

  proc xxx_collate {a b} { return [string compare $a $b] }
  do_execsql_test 1.$tn.1 $sql $res
   
  proc xxx_collate {a b} {error "no good"}
  do_test 1.$tn.2 { catchsql $sql } {1 {SQL logic error or missing database}}
}

finish_test

  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  char **argv            /* Text of each argument */
){
  sqlite4 *db;
  Tcl_DString str;
  int rc;
  char *zErr = 0;
  char *zSql;
  char zBuf[30];
  if( argc!=4 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
       " DB FORMAT STRING", 0);
    return TCL_ERROR;
  }
................................................................................
  sqlite4_free(0, (void *)p);
}
static int testCreateCollationCmp(
  void *pCtx,
  int nLeft,
  const void *zLeft,
  int nRight,
  const void *zRight

){
  TestCollationX *p = (TestCollationX *)pCtx;
  Tcl_Obj *pScript = Tcl_DuplicateObj(p->pCmp);
  int iRes = 0;


  Tcl_IncrRefCount(pScript);
  Tcl_ListObjAppendElement(0, pScript, Tcl_NewStringObj((char *)zLeft, nLeft));
  Tcl_ListObjAppendElement(0, pScript, Tcl_NewStringObj((char *)zRight,nRight));

  if( TCL_OK!=Tcl_EvalObjEx(p->interp, pScript, TCL_EVAL_DIRECT|TCL_EVAL_GLOBAL)

   || TCL_OK!=Tcl_GetIntFromObj(p->interp, Tcl_GetObjResult(p->interp), &iRes)
  ){
    Tcl_BackgroundError(p->interp);
  }
  Tcl_DecrRefCount(pScript);




  return iRes;

}
static int test_create_collation(
  ClientData clientData, /* Not used */
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int objc,              /* Number of arguments */
  Tcl_Obj *CONST objv[]  /* Command arguments */
){
................................................................................
** interp pointer to use when evaluating the TCL script is stored in
** pTestCollateInterp.
*/
static Tcl_Interp* pTestCollateInterp;
static int test_collate_func(
  void *pCtx, 
  int nA, const void *zA,
  int nB, const void *zB

){
  Tcl_Interp *i = pTestCollateInterp;
  int encin = SQLITE4_PTR_TO_INT(pCtx);
  int res;
  int n;
  sqlite4_env *pEnv = sqlite4_context_env(pCtx);

................................................................................
    sqlite4ValueFree(pVal);
  }
  sqlite4EndBenignMalloc(pEnv);

  Tcl_EvalObjEx(i, pX, 0);
  Tcl_DecrRefCount(pX);
  Tcl_GetIntFromObj(i, Tcl_GetObjResult(i), &res);

  return res;
}
static int test_collate(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
................................................................................
** Both collating functions increment the unaligned utf16 counter
** whenever they see a string that begins on an odd byte boundary.
*/
static int unaligned_string_counter = 0;
static int alignmentCollFunc(
  void *NotUsed,
  int nKey1, const void *pKey1,
  int nKey2, const void *pKey2

){
  int rc, n;
  n = nKey1<nKey2 ? nKey1 : nKey2;
  if( nKey1>0 && 1==(1&(SQLITE4_PTR_TO_INT(pKey1))) ) unaligned_string_counter++;


  if( nKey2>0 && 1==(1&(SQLITE4_PTR_TO_INT(pKey2))) ) unaligned_string_counter++;



  rc = memcmp(pKey1, pKey2, n);
  if( rc==0 ){
    rc = nKey1 - nKey2;
  }

  return rc;
}
static int add_alignment_test_collations(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){

  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  char **argv            /* Text of each argument */
){
  sqlite4 *db;
  Tcl_DString str;
  int rc;

  char *zSql;
  char zBuf[30];
  if( argc!=4 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
       " DB FORMAT STRING", 0);
    return TCL_ERROR;
  }
................................................................................
  sqlite4_free(0, (void *)p);
}
static int testCreateCollationCmp(
  void *pCtx,
  int nLeft,
  const void *zLeft,
  int nRight,
  const void *zRight,
  int *pRes
){
  TestCollationX *p = (TestCollationX *)pCtx;
  Tcl_Obj *pScript = Tcl_DuplicateObj(p->pCmp);
  int iRes = 0;
  int rc;

  Tcl_IncrRefCount(pScript);
  Tcl_ListObjAppendElement(0, pScript, Tcl_NewStringObj((char *)zLeft, nLeft));
  Tcl_ListObjAppendElement(0, pScript, Tcl_NewStringObj((char *)zRight,nRight));

  rc = Tcl_EvalObjEx(p->interp, pScript, TCL_EVAL_DIRECT|TCL_EVAL_GLOBAL);
  if( rc==TCL_OK ){
   rc = Tcl_GetIntFromObj(p->interp, Tcl_GetObjResult(p->interp), &iRes);


  }
  Tcl_DecrRefCount(pScript);

  if( rc!=TCL_OK ){
    return SQLITE4_ERROR;
  }
  *pRes = iRes;
  return SQLITE4_OK;
}
static int test_create_collation(
  ClientData clientData, /* Not used */
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int objc,              /* Number of arguments */
  Tcl_Obj *CONST objv[]  /* Command arguments */
){
................................................................................
** interp pointer to use when evaluating the TCL script is stored in
** pTestCollateInterp.
*/
static Tcl_Interp* pTestCollateInterp;
static int test_collate_func(
  void *pCtx, 
  int nA, const void *zA,
  int nB, const void *zB,
  int *pRes
){
  Tcl_Interp *i = pTestCollateInterp;
  int encin = SQLITE4_PTR_TO_INT(pCtx);
  int res;
  int n;
  sqlite4_env *pEnv = sqlite4_context_env(pCtx);

................................................................................
    sqlite4ValueFree(pVal);
  }
  sqlite4EndBenignMalloc(pEnv);

  Tcl_EvalObjEx(i, pX, 0);
  Tcl_DecrRefCount(pX);
  Tcl_GetIntFromObj(i, Tcl_GetObjResult(i), &res);
  *pRes = res;
  return SQLITE4_OK;
}
static int test_collate(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
................................................................................
** Both collating functions increment the unaligned utf16 counter
** whenever they see a string that begins on an odd byte boundary.
*/
static int unaligned_string_counter = 0;
static int alignmentCollFunc(
  void *NotUsed,
  int nKey1, const void *pKey1,
  int nKey2, const void *pKey2,
  int *pRes
){
  int res, n;
  n = nKey1<nKey2 ? nKey1 : nKey2;
  if( nKey1>0 && 1==(1&(SQLITE4_PTR_TO_INT(pKey1))) ){
    unaligned_string_counter++;
  }
  if( nKey2>0 && 1==(1&(SQLITE4_PTR_TO_INT(pKey2))) ){
    unaligned_string_counter++;
  }

  res = memcmp(pKey1, pKey2, n);
  if( res==0 ){
    res = nKey1 - nKey2;
  }
  *pRes = res;
  return SQLITE4_OK;
}
static int add_alignment_test_collations(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){