Question

How to convert a 32-bit number between big-endian and little-endian values in C++

Answer 1

#include <iostream>

int main(void)
{
    // 32 bit 

    // unsigned long _byteswap_ulong(unsigned long value); // VS

    unsigned long n = 1991994; //0x001E653A;

    std::cout << std::hex << std::uppercase << n << "\n";

    n = _byteswap_ulong(n);

    std::cout << std::hex << n << "\n";
}



/*

001E653A
3A651E00

*/

 

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Answer 2

#include <iostream>

uint32_t toLittleEndian(uint32_t value) {
    return ((value >> 24) & 0x000000FF) |
           ((value >> 8) & 0x0000FF00) |
           ((value << 8) & 0x00FF0000) |
           ((value << 24) & 0xFF000000);
}

int main(void)
{
    // 32 bit 

    unsigned long n = 1991994; //0x001E653A;

    std::cout << std::hex << std::uppercase << n << "\n";

    n = toLittleEndian(n);

    std::cout << std::hex << n << "\n";
}


/*

001E653A
3A651E00

*/

 

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Answer 3

#include <iostream>
#include <cstdint>
 
int main(void)
{
    // 32 bit 
 
    // uint32_t __builtin_bswap32 (uint32_t x) // GCC
 
    uint32_t n = 1991994; //0x001E653A;
 
    std::cout << std::hex << std::uppercase << n << "\n";
 
    n = __builtin_bswap32(n);
 
    std::cout << std::hex << n << "\n";
}
 
 
 
/*
 
001E653A
3A651E00
 
*/

 

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