SQLite

** ^(The sqlite3_value_numeric_type() interface attempts to apply
** numeric affinity to the value.  This means that an attempt is
** made to convert the value to an integer or floating point.  If
** such a conversion is possible without loss of information (in other
** words, if the value is a string that looks like a number)
** then the conversion is performed.  Otherwise no conversion occurs.
** The [SQLITE_INTEGER | datatype] after conversion is returned.)^
**
** ^Within the [xUpdate] method of a [virtual table], the
** sqlite3_value_nochange(X) interface returns true if and only if
** the column corresponding to X is unchanged by the UPDATE operation
** and the [xColumn] method had previously queried [sqlite3_vtab_nochange()]
** for that column and returned a NULL as a result.
**
** Please pay particular attention to the fact that the pointer returned
** from [sqlite3_value_blob()], [sqlite3_value_text()], or
** [sqlite3_value_text16()] can be invalidated by a subsequent call to
** [sqlite3_value_bytes()], [sqlite3_value_bytes16()], [sqlite3_value_text()],
** or [sqlite3_value_text16()].
**

const void *sqlite3_value_text16(sqlite3_value*);
const void *sqlite3_value_text16le(sqlite3_value*);
const void *sqlite3_value_text16be(sqlite3_value*);
int sqlite3_value_bytes(sqlite3_value*);
int sqlite3_value_bytes16(sqlite3_value*);
int sqlite3_value_type(sqlite3_value*);
int sqlite3_value_numeric_type(sqlite3_value*);
int sqlite3_value_nochange(sqlite3_value*);

/*
** CAPI3REF: Finding The Subtype Of SQL Values
** METHOD: sqlite3_value
**
** The sqlite3_value_subtype(V) function returns the subtype for
** an [application-defined SQL function] argument V.  The subtype

  if( pWInfo==0 ) return;

  /* Populate the argument registers. */
  for(i=0; i<pTab->nCol; i++){
    if( aXRef[i]>=0 ){
      sqlite3ExprCode(pParse, pChanges->a[aXRef[i]].pExpr, regArg+2+i);
    }else{
      sqlite3VdbeAddOp3(v, OP_VColumn, iCsr, i, regArg+2+i);
      sqlite3VdbeChangeP5(v, 1);
    }
  }
  if( HasRowid(pTab) ){
    sqlite3VdbeAddOp2(v, OP_Rowid, iCsr, regArg);
    if( pRowid ){
      sqlite3ExprCode(pParse, pRowid, regArg+1);
    }else{

    if( sqlite3IsToplevel(pParse) ){
      pParse->isMultiWrite = 0;
    }
  }else{
    /* Create a record from the argument register contents and insert it into
    ** the ephemeral table. */
    sqlite3VdbeAddOp3(v, OP_MakeRecord, regArg, nArg, regRec);
    sqlite3VdbeChangeP5(v, 2);
    sqlite3VdbeAddOp2(v, OP_NewRowid, ephemTab, regRowid);
    sqlite3VdbeAddOp3(v, OP_Insert, ephemTab, regRec, regRowid);
  }


  if( bOnePass==0 ){
    /* End the virtual table scan */

/*
** Print the value of a register for tracing purposes:
*/
static void memTracePrint(Mem *p){
  if( p->flags & MEM_Undefined ){
    printf(" undefined");
  }else if( p->flags & MEM_Null ){
    printf(p->flags & MEM_Zero ? " NULL-nochng" : " NULL");
  }else if( (p->flags & (MEM_Int|MEM_Str))==(MEM_Int|MEM_Str) ){
    printf(" si:%lld", p->u.i);
  }else if( p->flags & MEM_Int ){
    printf(" i:%lld", p->u.i);
#ifndef SQLITE_OMIT_FLOATING_POINT
  }else if( p->flags & MEM_Real ){
    printf(" r:%g", p->u.r);

  ** out how much space is required for the new record.
  */
  pRec = pLast;
  do{
    assert( memIsValid(pRec) );
    pRec->uTemp = serial_type = sqlite3VdbeSerialType(pRec, file_format, &len);
    if( pRec->flags & MEM_Zero ){
      if( serial_type==0 ){
        assert( pOp->p5==2 || CORRUPT_DB );
        /* serial_type 10 used internally only */
        pRec->uTemp = 10;
      }else if( nData ){
        if( sqlite3VdbeMemExpandBlob(pRec) ) goto no_mem;
      }else{
        nZero += pRec->u.nZero;
        len -= pRec->u.nZero;
      }
    }
    nData += len;

  VdbeBranchTaken(res!=0,2);
  if( res ) goto jump_to_p2;
  break;
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */

#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Opcode: VColumn P1 P2 P3 * P5
** Synopsis: r[P3]=vcolumn(P2)
**
** Store in register P3 the value of the P2-th column of
** the current row of the virtual-table of cursor P1.
**
** If the VColumn opcode is being used to fetch the value of
** an unchanging column during an UPDATE operation, then the P5
** value is 1.  Otherwise, P5 is 0.  The P5 value is returned
** by sqlite3_vtab_nochange() routine can can be used
** by virtual table implementations to return special "no-change"
** marks which can be more efficient, depending on the virtual table.
*/
case OP_VColumn: {
  sqlite3_vtab *pVtab;
  const sqlite3_module *pModule;

    break;
  }
  pVtab = pCur->uc.pVCur->pVtab;
  pModule = pVtab->pModule;
  assert( pModule->xColumn );
  memset(&sContext, 0, sizeof(sContext));
  sContext.pOut = pDest;
  if( pOp->p5 ){
    sqlite3VdbeMemSetNull(pDest);
    pDest->flags = MEM_Null|MEM_Zero;
    pDest->u.nZero = 0;
  }else{
    MemSetTypeFlag(pDest, MEM_Null);
  }
  rc = pModule->xColumn(pCur->uc.pVCur, &sContext, pOp->p2);
  sqlite3VtabImportErrmsg(p, pVtab);
  if( sContext.isError ){
    rc = sContext.isError;
  }
  sqlite3VdbeChangeEncoding(pDest, encoding);
  REGISTER_TRACE(pOp->p3, pDest);

/* One or more of the following flags are set to indicate the validOK
** representations of the value stored in the Mem struct.
**
** If the MEM_Null flag is set, then the value is an SQL NULL value.
** For a pointer type created using sqlite3_bind_pointer() or
** sqlite3_result_pointer() the MEM_Term and MEM_Subtype flags are also set.
** If both MEM_Null and MEM_Zero are set, that means that the value is
** an unchanging column value from VColumn.
**
** If the MEM_Str flag is set then Mem.z points at a string representation.
** Usually this is encoded in the same unicode encoding as the main
** database (see below for exceptions). If the MEM_Term flag is also
** set, then the string is nul terminated. The MEM_Int and MEM_Real 
** flags may coexist with the MEM_Str flag.
*/

     SQLITE_INTEGER,  /* 0x1c */
     SQLITE_NULL,     /* 0x1d */
     SQLITE_INTEGER,  /* 0x1e */
     SQLITE_NULL,     /* 0x1f */
  };
  return aType[pVal->flags&MEM_AffMask];
}

/* Return true if a parameter to xUpdate represents an unchanged column */
int sqlite3_value_nochange(sqlite3_value *pVal){
  return (pVal->flags&(MEM_Null|MEM_Zero))==(MEM_Null|MEM_Zero);
}

/* Make a copy of an sqlite3_value object
*/
sqlite3_value *sqlite3_value_dup(const sqlite3_value *pOrig){
  sqlite3_value *pNew;
  if( pOrig==0 ) return 0;
  pNew = sqlite3_malloc( sizeof(*pNew) );

**
** Virtual table implements might use this routine to optimize their
** performance by substituting a NULL result, or some other light-weight
** value, as a signal to the xUpdate routine that the column is unchanged.
*/
int sqlite3_vtab_nochange(sqlite3_context *p){
  assert( p );
  return sqlite3_value_nochange(p->pOut);
}

/*
** Return the current time for a statement.  If the current time
** is requested more than once within the same run of a single prepared
** statement, the exact same time is returned for each invocation regardless
** of the amount of time that elapses between invocations.  In other words,

}
u32 sqlite3VdbeSerialGet(
  const unsigned char *buf,     /* Buffer to deserialize from */
  u32 serial_type,              /* Serial type to deserialize */
  Mem *pMem                     /* Memory cell to write value into */
){
  switch( serial_type ){
    case 10: { /* Internal use only: NULL with virtual table
               ** UPDATE no-change flag set */
      pMem->flags = MEM_Null|MEM_Zero;
      break;
    }
    case 11:   /* Reserved for future use */
    case 0: {  /* Null */
      /* EVIDENCE-OF: R-24078-09375 Value is a NULL. */
      pMem->flags = MEM_Null;
      break;
    }
    case 1: {

  /* Cannot be both MEM_Int and MEM_Real at the same time */
  assert( (p->flags & (MEM_Int|MEM_Real))!=(MEM_Int|MEM_Real) );

  if( p->flags & MEM_Null ){
    /* Cannot be both MEM_Null and some other type */
    assert( (p->flags & (MEM_Int|MEM_Real|MEM_Str|MEM_Blob
                         |MEM_RowSet|MEM_Frame|MEM_Agg))==0 );

    /* If MEM_Null is set, then either the value is a pure NULL (the usual
    ** case) or it is a pointer set using sqlite3_bind_pointer() or
    ** sqlite3_result_pointer().  If a pointer, then MEM_Term must also be
    ** set.
    */
    if( (p->flags & (MEM_Term|MEM_Subtype))==(MEM_Term|MEM_Subtype) ){