Re: how to get the offset of the current struct

[Bruno Haible]

Jose E. Marchesi wrote:
> > type ABXML_chunk =
> >   struct
> >   {
> >     // Chunk header:
> >     uint<16> chunk_type;
> >     offset<uint<16>,B> chunk_header_size;
> >     offset<uint<32>,B> chunk_size;
> >
> >     // Data:
> >     uint<8>[0] before_bulk_of_data;
> >     uint<8>[chunk_size - before_bulk_of_data'offset] data;
> >   };
> ...
> In the body of a struct or union you can use OFFSET, which is the
> current offset from the beginning of the struct type.  Something like
> this:
> 
> type ABXML_chunk =
>   struct
>   {
>     // Chunk header:
>     uint<16> chunk_type;
>     offset<uint<16>,B> chunk_header_size;
>     offset<uint<32>,B> chunk_size;
> 
>     // Data:
>     uint<8>[chunk_size - OFFSET] data;
>   };

There is a small difference:
  before_bulk_of_data'offset    evaluates to the offset from the beginning
                                of the file (assuming the file is mapped at 0#B)
  OFFSET                        evaluates to the offset from the beginning of
                                the struct type.

So, what I would need is:

type ABXML_chunk =
  struct
  {
    // Chunk header:
    uint<16> chunk_type;
    offset<uint<16>,B> chunk_header_size;
    offset<uint<32>,B> chunk_size;

    // Data:
    uint<8>[chunk_size - (SELF'offset + OFFSET)] data;
  };

but that does not compile: "error: undefined variable 'SELF'".

Apparently it would be useful to have SELF be defined also outside of methods.

Bruno