C/C++ - Convert 24-bit signed integer to float

Question

I\'m programming in C++. I need to convert a 24-bit signed integer (stored in a 3-byte array) to float (normalizing to [-1.0,1.0]).

The platform is MSVC++ on x86 (wh

Answer 1

The solution that works for me:

/**
 * Convert 24 byte that are saved into a char* and represent a float
 * in little endian format to a C float number.
 */
float convert(const unsigned char* src)
{
    float num_float;
    // concatenate the chars (short integers) and
    // save them to a long int
    long int num_integer = (
            ((src[2] & 0xFF) << 16) | 
            ((src[1] & 0xFF) << 8) | 
            (src[0] & 0xFF)
        ) & 0xFFFFFFFF;

    // copy the bits from the long int variable
    // to the float.
    memcpy(&num_float, &num_integer, 4);

    return num_float;
}