On: Low Level Bit Hacks You Absolutely Must Know

[antipax]

I guess I should be the one to provide the usual warning that C and C++ make no guarantees about the in-memory representation of the built-in types, and that this type of code can be very dangerous.

It is, however, very cool when it works.

[jules → antipax]

No. They might not guarantee the representation, but they do guarantee that the operations (e.g. >> & |) work.

[scott_s → antipax]

There actually are guarantees, they're just a guarantee of ranges. (When bit-twiddling, you always want to use the unsigned version.)

char is guaranteed to be at least 8 bits.

short is guaranteed to be at least 16 bits.

int is guaranteed to be at least 16 bits.

long is guaranteed to be at least 32 bits.

long long is guaranteed to be at least 64 bits.

unsigned long is guaranteed to be the same size as a pointer.

[Locke1689 → antipax]

Look up C99 and stdint.h. You will be pleasantly surprised.

[antipax → Locke1689]

Consider me educated.

[mahmud → antipax]

you want to use "unsigned" and "register".

[mahmud → antipax]

you want to use "unsigned" and "register".