Converting a Variant Array to a Dynamic Array

Question

I'm trying to convert a variant array (of doubles, but it could be anything I guess) to a dynamic array. I usually use the DynArrayFromVariant and DynArrayToVariant procedures, but in this case my variant arrays are 1 based. These two functions only seem to work on 0 based arrays. Any idea how I could do what I need to do?

Call SetLength to allocate the dynamic array and then populate it with a for loop — David Heffernan
– David Heffernan, Commented Jul 3, 2012 at 11:05

Ondrej Kelle · Accepted Answer · 2012-07-03 11:49:12Z

8

If you know the type of your array elements you can write more efficient (while less generic) code:

function DoubleDynArrayFromVarArray(const V: Variant): TDoubleDynArray;
var
  P: Pointer;
  Count: Integer;
begin
  Result := nil;
  if not VarIsArray(V) or (VarType(V) and varTypeMask <> varDouble) or
    (VarArrayDimCount(V) <> 1) then
    raise EVariantInvalidArgError.Create(SVarInvalid);

  Count := VarArrayHighBound(V, 1) - VarArrayLowBound(V, 1) + 1;
  if Count = 0 then
    Exit;

  P := VarArrayLock(V);
  try
    SetLength(Result, Count);
    Move(P^, Result[0], Count * SizeOf(Double));
  finally
    VarArrayUnlock(V);
  end;
end;

answered Jul 3, 2012 at 11:49

Ondrej Kelle

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