double to hex string & hex string to double

Question

What I\'m trying to do is to convert a double to hex string and then back to double.

The following code does conversion double-to-hex string.

char *          


        

Answer 1

Using sprintf is slow, to be honest, but you can revert it with sscanf, doing almost exactly the same thing.

Well, actually, you'd have to copy each two characters to a buffer string, to decode each individually. My first try, below is incorrect:

double hexString2Double(char *buf)
{
  char *buf2 = new char[3];
  double a;
  char* c2d;
  c2d = (char *) &a;
  int i;

  buf2[2] = '\0'

  for(i = 0; i < 16; i++)
  {
    buf2[0] = *buf++;
    buf2[1] = *buf++;
    sscanf(buf2, "%X", c2d++);
  }

  return a;
}

You see, %X is decoded as an int, not as a byte. It might even work, depending on low-ending/high-endian issues, but it's basically broken. So, let's try to get around that:

double hexString2Double(char *buf)
{
  char *buf2 = new char[3];
  double a;
  char* c2d;
  c2d = (char *) &a;
  int i;
  int decoder;

  buf2[2] = '\0'

  for(i = 0; i < 16; i++)
  {
    buf2[0] = *buf++;
    buf2[1] = *buf++;
    sscanf(buf2, "%X", &decoder);
    c2d++ = (char) decoder;
  }

  return a;
}

Barring syntax errors and such, I think this should work.