va_args_count.h

/* va_args_count. https://github.com/donmccaughey/va_args_count
 Copyright (c) 2014, Don McCaughey. All rights reserved.

 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:

 - Redistributions of source code must retain the above copyright notice, this
 list of conditions and the following disclaimer.

 - Redistributions in binary form must reproduce the above copyright notice,
 this list of conditions and the following disclaimer in the documentation
 and/or other materials provided with the distribution.

 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */

#ifndef VA_ARGS_COUNT_H_INCLUDED
#define VA_ARGS_COUNT_H_INCLUDED


/* VA_ARGS_COUNT(...)
 *
 * Returns the number of arguments passed to the macro as an int.
 * 
 * Arguments may be passed to this macro directly or by using __VA_ARGS__ as 
 * part of another macro.
 *
 * See https://groups.google.com/d/topic/comp.std.c/d-6Mj5Lko_s/discussion
 * for origin of VA_ARGS_COUNT() and related macros.
 */
#define VA_ARGS_COUNT(...) \
    VA_ARGS_SHIFT_COUNT_VALUES(__VA_ARGS__, VA_ARGS_COUNT_VALUES)


// Component of VA_ARGS_COUNT() macro.
#define VA_ARGS_COUNT_VALUES \
                            63, 62, 61, 60, \
    59, 58, 57, 56, 55, 54, 53, 52, 51, 50, \
    49, 48, 47, 46, 45, 44, 43, 42, 41, 40, \
    39, 38, 37, 36, 35, 34, 33, 32, 31, 30, \
    29, 28, 27, 26, 25, 24, 23, 22, 21, 20, \
    19, 18, 17, 16, 15, 14, 13, 12, 11, 10, \
     9,  8,  7,  6,  5,  4,  3,  2,  1,  0


// Component of VA_ARGS_COUNT() macro.
#define VA_ARGS_SELECT_COUNT_VALUE( \
       _1,  _2,  _3,  _4,  _5,  _6,  _7,  _8,  _9, _10, \
      _11, _12, _13, _14, _15, _16, _17, _18, _19, _20, \
      _21, _22, _23, _24, _25, _26, _27, _28, _29, _30, \
      _31, _32, _33, _34, _35, _36, _37, _38, _39, _40, \
      _41, _42, _43, _44, _45, _46, _47, _48, _49, _50, \
      _51, _52, _53, _54, _55, _56, _57, _58, _59, _60, \
      _61, _62, _63, \
        N, ... \
    ) \
      N


// Component of VA_ARGS_COUNT() macro.
#define VA_ARGS_SHIFT_COUNT_VALUES(...) \
    VA_ARGS_SELECT_COUNT_VALUE(__VA_ARGS__)


#endif