Swap bits in c++ for a double
- by hidayat
Im trying to change from big endian to little endian on a double. One way to go is to use
double val, tmp = 5.55;
((unsigned int *)&val)[0] = ntohl(((unsigned int *)&tmp)[1]);
((unsigned int *)&val)[1] = ntohl(((unsigned int *)&tmp)[0]);
But then I get a warning: "dereferencing type-punned pointer will break strict-aliasing rules" and I dont want to turn this warning off.
Another way to go is:
#define ntohll(x) ( ( (uint64_t)(ntohl( (uint32_t)((x << 32) >> 32) )) << 32) | ntohl( ((uint32_t)(x >> 32)) ) )
val = (double)bswap_64(unsigned long long(tmp)); //or
val = (double)ntohll(unsigned long long(tmp));
But then a lose the decimals.
Anyone know a good way to swap the bits on a double without using a for loop?
