Can we implement ctype functions through table?

[Xiang Xiao]

Hi all,
For example, here is isspace implementation:
#  define isspace(c) \
    ((c) == ' '  || (c) == '\t' || (c) == '\n' || (c) == '\r' || \
     (c) == '\f' || (c) == '\v')
The argument of c will evaluate 6 times, which make the following code suddenly 
fail:
while (end != begin)
  {
    If (!isspace(*--end))
      {
         break;
      }
  }
But it work well with other libc implementation, because all other libc utilize 
a table to classify  the char type:
https://github.com/bminor/newlib/blob/master/newlib/libc/include/ctype.h#L97
https://github.com/bminor/glibc/blob/master/ctype/ctype.h#L197
and the argument only need evaluate once.
So my question is: can we implement ctype functions through table to improve 
the compatibility?
Yes, the table need take more 256 bytes ROM space, but the complex expression 
used in NuttX also bloat the code size, especially
considering ctype function is used very frequently.

Thanks
Xiang