Convert Big-Endian struct to Little-Endian C++

Question

I am working on a parser code to read all the data from a binary file. Incidentally the binary file is in Big-Endian. When I read the binary header of the file I read it into a Structure through this method:

Structure:

struct BinaryHeader{
    int jobID; 
    int lineNumber; 
    int reelNumber; 
    short unsigned int tracesPerEnsemble; 
    short int aTracesPerEnsemble; 
    short unsigned int sampleInterval; 
    short unsigned int sampleIntervalOriginalFieldRec; 
    short unsigned int samplesPerTrace; 
    short unsigned int samplesPerTraceOriginalFieldRec;
    ...etc.

Parsing method:

void Segy::parseSegyFile(){
    char textHeader[3200]; //to skip the first 3200 byte
    ifs.read(textHeader,sizeof(textHeader));
    BinaryHeader binaryHeader;
    ifs.read(reinterpret_cast<char *>(&binaryHeader), sizeof(binaryHeader));
    }
}

As I mentioned the endianness is Big-Endian, I found this answer for the conversion and it works like a charm but when -- for exapmle -- I print out the binaryHeader I always have to swap the sequence of the bytes.

std::cout << std::left << std::setw(w) << "JobID:" << std::fixed << SwapEnd(binaryHeader.jobID) << std::endl

Question: Is there any elegant way to convert the whole binaryHeader to Little-Endian?

Create a little array, which lists the sizes of the members (`desc`). And create a function, which takes a pointer to the header, and a pointer to `desc` and does the byte swap. This way you can use this function for any structure. — geza, Feb 18 '19 at 17:03
@NathanOliver: it would swap the order of the members, which is not intended. — geza, Feb 18 '19 at 17:03
No, C++ has no reflection (yet). Maybe look at magic_get (actually, don't). — rustyx, Feb 18 '19 at 17:05
Look at the boost endian buffers. I assume it's the easiest solution for your problem. — Deedee Megadoodoo, Feb 19 '19 at 01:42

score 1 · Accepted Answer · answered Feb 18 '19 at 17:35

Well I do not know if this is elegent to you but boost::fusion might help you.

struct BinaryHeader{
    int jobID; 
    int lineNumber; 
    int reelNumber; 
    ...
};
BOOST_FUSION_ADAPT_STRUCT(
    BinaryHeader,
    jobID,
    lineNumber,
    reelNumber
    ...
)
struct EndianSwap
{
    template<typename T>
    void operator()(T& t) const
    {
        SwapEnd(t);
    }
};

then after reading a BinaryHeader in big endian just do this.

boost::fusion::for_each(b, EndianSwap());

Convert Big-Endian struct to Little-Endian C++

1 Answers1