AttributeHeader.h

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/*******************************************************************************
 *
 * Copyright (c) 2008-2010 Michael Schulze <mschulze@ivs.cs.uni-magdeburg.de>
 *                    2010 Marcus Foerster <MarcusFoerster1@gmx.de>
 * All rights reserved.
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 *      distribution.
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#ifndef _Attribute_Header_h_
#define _Attribute_Header_h_

#include <stdint.h>

#include "util/endianness.h"

#include "mw/attributes/detail/FirstByteOfHeader.h"
#include "mw/attributes/detail/ValueByteCount.h"
#include "mw/attributes/detail/CaseSelector.h"

namespace famouso {
    namespace mw {
        namespace attributes {
            namespace detail {

                template <typename Attr>
                struct AttributeHeader {
                    private:
                        typedef typename CaseSelector<
                                          uint8_t, 1, 1, 1, 2, (1 + 1), (1 + 1 + 1)
                                         >::type sizeSelector;

                        // The byte count for the attribute header (It could also include a
                        //  part of the attribute's value if the LVS switch is set)
                        static const uint8_t size = sizeSelector::template select_ct<Attr>::value;

                        static const bool res2 = (ValueBitCount<Attr>::value < 9) ? false : true;

                        static const bool useOr = CaseSelector<bool,
                                                               true,
                                                               res2,
                                                               false,
                                                               false,
                                                               false,
                                                               false
                                                              >::template select_ct<Attr>::value;

                        enum {
                            writeLowerLengthBits     = 0x10,
                            writeType                = 0x11,
                            writeLowerLenBitsAndType = 0x12,
                            nothingMore              = 0x13
                        };

                        // We use this to decide in the code below if further bytes
                        //  must be manipulated
                        static const uint8_t toWrite = CaseSelector<uint8_t,
                                                                    nothingMore,
                                                                    nothingMore,
                                                                    nothingMore,
                                                                    writeLowerLengthBits,
                                                                    writeType,
                                                                    writeLowerLenBitsAndType
                                                                   >::template select_ct<Attr>::value;

                        // TODO: Let this class also work on the this pointer not having real
                        //  own memory
                        uint8_t data[size];

                    public:
                        typedef AttributeHeader type;

                        AttributeHeader() {
                            // Either use an OR operation (to not overwrite existing bits already
                            //  set by writing the value) or directly assign the header byte since
                            //  there is no danger overwriting
                            if (useOr) {
                                data[0] |= (FirstByteOfHeader<Attr>::value);
                            } else {
                                data[0] = (FirstByteOfHeader<Attr>::value);
                            }

                            // Handle eventually further written bytes (depending on extension,
                            //  LVS etc.)
                            if (toWrite == writeLowerLengthBits) {
                                data[1] = (ValueByteCount<Attr>::value & 0xFF);
                            } else if (toWrite == writeType) {
                                data[1] = (Attr::id & 0xFF);
                            } else if (toWrite == writeLowerLenBitsAndType) {
                                data[1] = (ValueByteCount<Attr>::value & 0xFF);
                                data[2] = (Attr::id & 0xFF);
                            }
                        }
                };

            } // end namespace detail
        } // end namespace attributes
    } // end namespace mw
} // end namespace famouso

#endif