endian.cc

// #include <boost/array.hpp>

// int main()
// {
//   boost::array<int, 3> a{};
//   return a[0];
// }

#include <iostream>
#include <cstdio>
#include <boost/endian/arithmetic.hpp>
#include <boost/static_assert.hpp>

using namespace boost::endian;

namespace {
    struct header {
        big_int32_t file_code;
        big_int32_t file_length;
        little_int32_t version;
        little_int32_t shape_type;
    };

    const char* filename = "test.dat";
}

int main(int argc, char** argv) {
    header h;

    BOOST_STATIC_ASSERT(sizeof(h) == 16U);  // reality check
    
    h.file_code   = 0x01020304;
    h.file_length = sizeof(header);
    h.version     = 1;
    h.shape_type  = 0x01020304;

    //  Low-level I/O such as POSIX read/write or <cstdio>
    //  fread/fwrite is sometimes used for binary file operations
    //  when ultimate efficiency is important. Such I/O is often
    //  performed in some C++ wrapper class, but to drive home the
    //  point that endian integers are often used in fairly
    //  low-level code that does bulk I/O operations, <cstdio>
    //  fopen/fwrite is used for I/O in this example.

    std::FILE* fi = std::fopen(filename, "wb");  // MUST BE BINARY
    
    if (!fi)
    {
        std::cout << "could not open " << filename << '\n';
        return 1;
    }

    if (std::fwrite(&h, sizeof(header), 1, fi)!= 1)
    {
        std::cout << "write failure for " << filename << '\n';
        return 1;
    }

    std::fclose(fi);

    std::cout << "created file " << filename << '\n';

    return 0;
}