Description

   The strxfrm function transforms the string pointed to by s2,
   and stores the resulting string in the array pointed to by s1.
   No more than maxchar bytes, including the null terminator, are
   placed into the array pointed to by s1.

   If the value of maxchar is less than the required size to store
   the transformed string (including the terminating null), the
   contents of the array pointed to by s1 is indeterminate. In such
   a case, the function returns the size of the transformed string.

   If maxchar is 0, then s1 is allowed to be a NULL pointer, and the
   function returns the required size of the s1 array before making
   the transformation.

   The string comparison functions, strcoll and strcmp, can produce
   different results given the same two strings to compare. The
   reason for this is that strcmp does a straightforward comparison
   of the code point values of the characters in the strings,
   whereas strcoll uses the locale information to do the comparison.
   Depending on the locale, the strcoll comparison can be a
   multipass operation, which is slower than strcmp.

   The purpose of the strxfrm function is to transform strings in
   such a way that if you pass two transformed strings to the strcmp
   function, the result is the same as passing the two original
   strings to the strcoll function. The strxfrm function is useful
   in applications that need to do a large number of comparisons on
   the same strings using strcoll. In this case, it might be more
   efficient (depending on the locale) to transform the strings once
   using strxfrm, and then do comparisons using strcmp.