VarHeaderLength.h

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 * Copyright (c) 2010 Philipp Werner <philipp.werner@st.ovgu.de>
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#ifndef __VARHEADERLENGTH_H_FB8B6AC493785D__
#define __VARHEADERLENGTH_H_FB8B6AC493785D__


#include "debug.h"
#include "config/type_traits/ExpandedRangeTypeSelector.h"


namespace famouso {
    namespace mw {
        namespace afp {
            namespace defrag {
                namespace detail {


                    template <class DCP>
                    class VarHeaderLength {

                            typedef typename DCP::SizeProp::elen_t elen_t;
                            typedef typename DCP::SizeProp::flen_t flen_t;
                            typedef typename DCP::SizeProp::fcount_t fcount_t;

                        public:

                            typedef typename ExpandedRangeTypeSelector<elen_t>::type eelen_t;

                            static eelen_t get_payload(fcount_t frag_count, flen_t no_ext_mtu) {
                                eelen_t p = 0;          // payload
                                flen_t h = 1;           // header length
                                fcount_t c_h = 32;      // max. fragment count for header length = h
                                fcount_t c_max = 32;    // max. fragment count for header length <= h

                                while (frag_count > c_h) {
                                    frag_count -= c_h;
                                    p += c_h * (no_ext_mtu - h);

                                    h++;
                                    FAMOUSO_ASSERT(h < no_ext_mtu);
                                    c_h = 127 * c_max;
                                    c_max = 128 * c_max;
                                }
                                p += frag_count * (no_ext_mtu - h);
                                return p;
                            }


                            static flen_t get_basic_header_len(fcount_t fseq) {
                                flen_t hl = 1;
                                while (fseq >= 32) {
                                    hl++;
                                    fseq >>= 7;
                                }
                                return hl;
                            }
                    };


                } // namespace detail
            } // namespace defrag
        } // namespace afp
    } // namespace mw
} // namespace famouso


#endif // __VARHEADERLENGTH_H_FB8B6AC493785D__