Macro decoder_function

macro_rules! decoder_function {
    ($preamble:block,
     $loop_preable:block,
     $eof:block,
     $body:block,
     $slf:ident,
     $src_consumed:ident,
     $dest:ident,
     $source:ident,
     $b:ident,
     $destination_handle:ident,
     $unread_handle:ident,
     $destination_check:ident,
     $name:ident,
     $code_unit:ty,
     $dest_struct:ident) => { ... };
}