src/include/base3.h

   1 /*
   2  * This file is part of the coreboot project.
   3  *
   4  * Copyright 2014 Google Inc.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; version 2 of the License.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  */
  15
  16 #ifndef __SRC_INCLUDE_BASE3_H__
  17 #define __SRC_INCLUDE_BASE3_H__
  18
  19 /* We translate a floating pin (Z) as the ternary digit 2. */
  20 #define Z 2
  21
  22 /*
  23  * This provides a variadic macro BASE3() that can be used to translate a set of
  24  * pin states into its base-3 integer representation, even in the context of a
  25  * static initializer. You can call it with any number of up to 6 arguments,
  26  * e.g. BASE3(1, Z) -> 5 or BASE3(0, Z, 1, 0) -> 21. Just don't look too closely
  27  * at how the sausage is made. (Pay extra attention to typos when expanding it!)
  28  */
  29 #define _BASE3_IMPL_1(arg0, arg1, arg2, arg3, arg4, arg5) arg0
  30 #define _BASE3_IMPL_2(arg0, arg1, arg2, arg3, arg4, arg5) \
  31         (arg1 + (3 * _BASE3_IMPL_1(arg0, arg1, arg2, arg3, arg4, arg5)))
  32 #define _BASE3_IMPL_3(arg0, arg1, arg2, arg3, arg4, arg5) \
  33         (arg2 + (3 * _BASE3_IMPL_2(arg0, arg1, arg2, arg3, arg4, arg5)))
  34 #define _BASE3_IMPL_4(arg0, arg1, arg2, arg3, arg4, arg5) \
  35         (arg3 + (3 * _BASE3_IMPL_3(arg0, arg1, arg2, arg3, arg4, arg5)))
  36 #define _BASE3_IMPL_5(arg0, arg1, arg2, arg3, arg4, arg5) \
  37         (arg4 + (3 * _BASE3_IMPL_4(arg0, arg1, arg2, arg3, arg4, arg5)))
  38 #define _BASE3_IMPL_6(arg0, arg1, arg2, arg3, arg4, arg5) \
  39         (arg5 + (3 * _BASE3_IMPL_5(arg0, arg1, arg2, arg3, arg4, arg5)))
  40 #define _BASE3_IMPL(arg0, arg1, arg2, arg3, arg4, arg5, NARGS, ...) \
  41         _BASE3_IMPL##NARGS(arg0, arg1, arg2, arg3, arg4, arg5)
  42 #define BASE3(...) _BASE3_IMPL(__VA_ARGS__, _6, _5, _4, _3, _2, _1)
  43
  44 #endif /* __SRC_INCLUDE_BASE3_H__ */