On 04/12/2013 11:47 AM, Reinier Olislagers wrote: > if (FNullField <> nil) and (Dst = nil) and (AFieldDef.NullPosition >= > 0) then > begin > Src := PChar(Src) + FNullField.Offset + (AFieldDef.NullPosition shr 3); > Result := (PByte(Src)^ and (1 shl (AFieldDef.NullPosition and $7))) = 0; > exit; > end; >
NullPosition is a bit position, 8 bits in a byte. To find bit x you have to look in byte Start + x div 8. x div 8 can be written as x shr 3. Now that you have found the byte where bit x is you need to isolate that bit. Its position in the byte is X mod 8 which you can write as X and $7. The 1 shl (X and $7) is done to create a mask to get the correct bit. Ludo _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
