src/include/base3.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #ifndef __SRC_INCLUDE_BASE3_H__
   4 #define __SRC_INCLUDE_BASE3_H__
   5
   6 /* We translate a floating pin (Z) as the ternary digit 2. */
   7 #define Z 2
   8
   9 /*
  10  * This provides a variadic macro BASE3() that can be used to translate a set of
  11  * pin states into its base-3 integer representation, even in the context of a
  12  * static initializer. You can call it with any number of up to 6 arguments,
  13  * e.g. BASE3(1, Z) -> 5 or BASE3(0, Z, 1, 0) -> 21. Just don't look too closely
  14  * at how the sausage is made. (Pay extra attention to typos when expanding it!)
  15  */
  16 #define _BASE3_IMPL_1(arg0, arg1, arg2, arg3, arg4, arg5) arg0
  17 #define _BASE3_IMPL_2(arg0, arg1, arg2, arg3, arg4, arg5) \
  18         (arg1 + (3 * _BASE3_IMPL_1(arg0, arg1, arg2, arg3, arg4, arg5)))
  19 #define _BASE3_IMPL_3(arg0, arg1, arg2, arg3, arg4, arg5) \
  20         (arg2 + (3 * _BASE3_IMPL_2(arg0, arg1, arg2, arg3, arg4, arg5)))
  21 #define _BASE3_IMPL_4(arg0, arg1, arg2, arg3, arg4, arg5) \
  22         (arg3 + (3 * _BASE3_IMPL_3(arg0, arg1, arg2, arg3, arg4, arg5)))
  23 #define _BASE3_IMPL_5(arg0, arg1, arg2, arg3, arg4, arg5) \
  24         (arg4 + (3 * _BASE3_IMPL_4(arg0, arg1, arg2, arg3, arg4, arg5)))
  25 #define _BASE3_IMPL_6(arg0, arg1, arg2, arg3, arg4, arg5) \
  26         (arg5 + (3 * _BASE3_IMPL_5(arg0, arg1, arg2, arg3, arg4, arg5)))
  27 #define _BASE3_IMPL(arg0, arg1, arg2, arg3, arg4, arg5, NARGS, ...) \
  28         _BASE3_IMPL##NARGS(arg0, arg1, arg2, arg3, arg4, arg5)
  29 #define BASE3(...) _BASE3_IMPL(__VA_ARGS__, _6, _5, _4, _3, _2, _1)
  30
  31 #endif /* __SRC_INCLUDE_BASE3_H__ */