Re: Stream_Element_Array

[Alexander Korolev <antonovkablog@gmail.com>]

On Sep 14, 12:31 pm, Simon Wright <si...@pushface.org> wrote:
> Alexander Korolev <antonovkab...@gmail.com> writes:
> > I have a Type
>
> > type Message_Header is
> >     record
> >        -- Components                  --   8 bit
> >        Length    : Unsigned_16;    -- 16 bit  (MSB)
> >        -- other components          --   8 bit
> >     end record;
>
> > How I could split the Lenght component on two subsequent
> > Stream_Element ( 8-bit)?
>
> > Command: Stream_Element_Array (1 .. 64);
>
> I think the best way is using unchecked conversion. Below adds the
> complication of converting to network byte order if not already so:
>
>    subtype Two_Byte_Slice is Ada.Streams.Stream_Element_Array (1 .. 2);
>
>    Big_Endian : constant Boolean
>      := System."=" (System.Default_Bit_Order, System.High_Order_First);
>
>    function To_Two_Byte_Slice (S : Unsigned_16) return Two_Byte_Slice is
>       function Convert is new Ada.Unchecked_Conversion (Unsigned_16,
>                                                         Two_Byte_Slice);
>       Tmp : constant Two_Byte_Slice := Convert (S);
>    begin
>       if Big_Endian then
>          return Tmp;
>       else
>          return (1 => Tmp (2),
>                  2 => Tmp (1));
>       end if;
>    end To_Two_Byte_Slice;
>
>    Command (11 .. 12) := To_Two_Byte_Slice (42);

Thanks Simon
I'll try your code anyway.
-- I thought I might made the issue more complex
The Unsigned_16 came from transformation of the Header_Type component
by Interfaces.Unsigned_16 (Last).
It means I have Last: Stream_Element_Count (8 bit) set correctly.
-- (Note For Per: I can not send the lenth to target stream because
the whole
-- message (stream_element_array) assembled needs further computation
over + one transformation
-- (staffing - something like replace 111 with 444 + 555 if 111
occures in some components of the message including
-- the letgh ) after the computation as an external dev requirement