----- Original Message ----- From: "Terry Golubiewski" <tjgolubi@netins.net> To: <boost@lists.boost.org> Sent: Thursday, June 03, 2010 10:27 PM Subject: Re: [boost] [boost::endian] Summary of discussion #1
Beman's approach is integer centric and combines the use of non-natively-sized integers and endianness. I would like to see Beman's library split into two parts: the integer part and the endian-part.
It's easy for me to suggest that someone else should change. But what would such a change look like. How about this... (I've ignored alignment)
namespace boost { namespace interface {
template<size_t Bits, endian_t Endian=native> class PackedInteger {
<snip> I think that the packed class should take the same template parameters as the original endian class, as this packed class is able to manage integer endian. template <BOOST_SCOPED_ENUM(endianness) E, typename T, std::size_t n_bits, BOOST_SCOPED_ENUM(alignment) A = alignment::unaligned> class endian_pack; The single difference between endian_pack and the original endian is that it don't inherits from cover_operators.
My point is that one must consider "how" the compact integer will be stored in memory, so endianness is important to an implementation of PackedInteger<Bits>. PackedInteger<> must provide for all possible native endiannesses, so why not make it a template parameter that defaults to "native"? So Beman's "endian" survives almost intact with just a name change from "endian" to "PackedInteger" and a reordering of the template parameters.
Then I suppose endian<E, T> should be specialized to support a PackedInteger<Bits, Endian>, but I can't think of what it would be used for, since in a message specification it would be easier to just use "PackedInteger<24, big>" instead of "endian<big, PackedInteger<24>>". Still, either should work, so here it is...
template<endian_t E1, size_t Bits, endian_t E2> class endian<E1, PackedInteger<Bits, E2>> {
The original endian class could be declared as template <BOOST_SCOPED_ENUM(endianness) E, typename T, std::size_t n_bits, BOOST_SCOPED_ENUM(alignment) A = alignment::unaligned> class endian; template <typename T, std::size_t n_bits> class endian< endianness::big, T, n_bits, alignment::unaligned > : cover_operators< endian< endianness::big, T, n_bits >, T > { typedef endian_pack<E,T,n_bits,A> pack_type; pack_type pack_; // change every access to the value_type original m_value by pack_.m_value. This seems simple. Isn't it? Best, Vicente