Converting float values from big endian to little endian

Question

Is it possible to convert floats from big to little endian? I have a big endian value from a PowerPC platform that I am sendING via TCP to a Windows process (li

Answer 1

An elegant way to do the byte exchange is to use a union:

float big2little (float f)
{
    union
    {
        float f;
        char b[4];
    } src, dst;

    src.f = f;
    dst.b[3] = src.b[0];
    dst.b[2] = src.b[1];
    dst.b[1] = src.b[2];
    dst.b[0] = src.b[3];
    return dst.f;
}

Following jjmerelo's recommendation to write a loop, a more generic solution could be:

typedef float number_t;
#define NUMBER_SIZE sizeof(number_t)

number_t big2little (number_t n)
{
    union
    {
        number_t n;
        char b[NUMBER_SIZE];
    } src, dst;

    src.n = n;
    for (size_t i=0; i<NUMBER_SIZE; i++)
        dst.b[i] = src.b[NUMBER_SIZE-1 - i];

    return dst.n;
}

Answer 2

in some case, especially on modbus: network byte order for a float is:

nfloat[0] = float[1]
nfloat[1] = float[0]
nfloat[2] = float[3]
nfloat[3] = float[2]

Answer 3

Don't memcpy the data directly into a float type. Keep it as char data, swap the bytes and then treat it as a float.