endianness.hh

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#ifndef TYPELIB_ENDIANSWAP_HH
#define TYPELIB_ENDIANSWAP_HH

#include <typelib/value.hh>
#include <utilmm/system/endian.hh>
#include <limits>

namespace Typelib
{
    struct UnsupportedEndianSwap : public std::runtime_error
    { 
        UnsupportedEndianSwap(std::string const& what) : std::runtime_error("cannot swap " + what) { }
    };

    /* This visitor swaps the endianness of the given value in-place */
    class EndianSwapVisitor : public ValueVisitor
    {
    protected:
        bool visit_ (int8_t  & value) { value = utilmm::endian::swap(value); return true; }
        bool visit_ (uint8_t & value) { value = utilmm::endian::swap(value); return true; }
        bool visit_ (int16_t & value) { value = utilmm::endian::swap(value); return true; }
        bool visit_ (uint16_t& value) { value = utilmm::endian::swap(value); return true; }
        bool visit_ (int32_t & value) { value = utilmm::endian::swap(value); return true; }
        bool visit_ (uint32_t& value) { value = utilmm::endian::swap(value); return true; }
        bool visit_ (int64_t & value) { value = utilmm::endian::swap(value); return true; }
        bool visit_ (uint64_t& value) { value = utilmm::endian::swap(value); return true; }
        bool visit_ (float   & value) { value = utilmm::endian::swap(value); return true; }
        bool visit_ (double  & value) { value = utilmm::endian::swap(value); return true; }
        bool visit_ (Value const& v, Pointer const& t) { throw UnsupportedEndianSwap("pointers"); }
        bool visit_ (Enum::integral_type& v, Enum const& e) { v = utilmm::endian::swap(v); return true; }
    };

    void endian_swap(Value v)
    {
        EndianSwapVisitor swapper;
        swapper.apply(v);
    }

    class CompileEndianSwapVisitor : public TypeVisitor 
    {
        // The current place into the output: the next element which are to be
        // byte-swapped will be written at this index in the output data
        // buffer.
        size_t m_output_index;

    public:
        // The compiled-in description of the byte-swap operation
        //
        // Given an output index, an element of compiled is the absolute
        // index of the input byte which should be written at this output index:
        //   output_buffer[output_index] = input_buffer[*it_compiled]
        //
        // After a "normal" operation (i.e. neither a skip nor an array),
        // output index is incremented and we handle the next operation
        // found in compiled
        std::vector<size_t> m_compiled;

        static size_t const FLAG_SKIP  = ((size_t) -1);
        static size_t const FLAG_ARRAY = ((size_t) -2);
        static size_t const FLAG_END   = ((size_t) -3);
        static size_t const FLAG_SWAP_4 = ((size_t) -4);
        static size_t const FLAG_SWAP_8 = ((size_t) -5);
        static const size_t SizeOfEnum = sizeof(int);;

    protected:
        void skip(int skip_size);
        bool visit_ (OpaqueType const& type);
        bool visit_ (Numeric const& type);
        bool visit_ (Enum const& type);
        bool visit_ (Pointer const& type);
        bool visit_ (Array const& type);
        bool visit_ (Compound const& type);
        bool visit_ (Container const& type);

    public:
        ~CompileEndianSwapVisitor() { }
        void apply(Type const& type);

        void swap(Value in, Value out)
        {
            CompileEndianSwapVisitor::swap(0, 0,
                    m_compiled.begin(), m_compiled.end(),
                    in, out);
        }

        std::pair<size_t, std::vector<size_t>::const_iterator> 
            swap(size_t output_offset, size_t input_offset,
                std::vector<size_t>::const_iterator it,
                std::vector<size_t>::const_iterator end,
                Value in, Value out);

        void display();
    };
}

#endif