Determine whether the CPU is a small-end storage (Little endian) or a large-end storage (Big endian) mode.

First version:

// Return true in big-endian machinesbool check_big_endian1 () {int a = 0; int * p = & a; * (char *) p = 1; return! = 1 ;}

The second version of union is used:

// Return true in big-endian machinesbool check_big_endian2 () {union {int a; char B;} var; // sizeof (var) = 4var. a = 1; return var. b! = 1 ;}

Finally, let's look at a version to avoid function calls:

Static union {int a; char B;} _ s_var_endian_check = {1}; # define ISLITTLEENDIAN (_ s_var_endian_check. B = 1) # define ISBIGENDIAN! ISLITTLEENDIAN

In this way, the macro ISLITTLEENDIAN and ISBIGENDIAN can be used to read the values of static variables to determine whether it is a small-end mode or a large-end mode.

However, this is the way C is written. The inline function can be used in C ++ to avoid macro usage.