git.ozlabs.org Git - ccan/blob - ccan/cppmagic/cppmagic.h

   1 /* MIT (BSD) license - see LICENSE file for details */
   2 #ifndef CCAN_CPPMAGIC_H
   3 #define CCAN_CPPMAGIC_H
   4
   5 /**
   6  * CPPMAGIC_NOTHING - expands to nothing
   7  */
   8 #define CPPMAGIC_NOTHING()
   9
  10 /**
  11  * CPPMAGIC_STRINGIFY - convert arguments to a string literal
  12  */
  13 #define _CPPMAGIC_STRINGIFY(...)        #__VA_ARGS__
  14 #define CPPMAGIC_STRINGIFY(...)         _CPPMAGIC_STRINGIFY(__VA_ARGS__)
  15
  16 /**
  17  * CPPMAGIC_GLUE2 - glue arguments together
  18  *
  19  * CPPMAGIC_GLUE2(@a_, @b_)
  20  *      expands to the expansion of @a_ followed immediately
  21  *      (combining tokens) by the expansion of @b_
  22  */
  23 #define _CPPMAGIC_GLUE2(a_, b_)         a_##b_
  24 #define CPPMAGIC_GLUE2(a_, b_)          _CPPMAGIC_GLUE2(a_, b_)
  25
  26 /**
  27  * CPPMAGIC_1ST - return 1st argument
  28  *
  29  * CPPMAGIC_1ST(@a_, ...)
  30  *      expands to the expansion of @a_
  31  */
  32 #define CPPMAGIC_1ST(a_, ...)           a_
  33
  34 /**
  35  * CPPMAGIC_2ND - return 2nd argument
  36  *
  37  * CPPMAGIC_2ST(@a_, @b_, ...)
  38  *      expands to the expansion of @b_
  39  */
  40 #define CPPMAGIC_2ND(a_, b_, ...)       b_
  41
  42 /**
  43  * CPPMAGIC_ISZERO - is argument '0'
  44  *
  45  * CPPMAGIC_ISZERO(@a)
  46  *      expands to '1' if @a is '0', otherwise expands to '0'.
  47  */
  48 #define _CPPMAGIC_ISPROBE(...)          CPPMAGIC_2ND(__VA_ARGS__, 0)
  49 #define _CPPMAGIC_PROBE()               $, 1
  50 #define _CPPMAGIC_ISZERO_0              _CPPMAGIC_PROBE()
  51 #define CPPMAGIC_ISZERO(a_)             \
  52         _CPPMAGIC_ISPROBE(CPPMAGIC_GLUE2(_CPPMAGIC_ISZERO_, a_))
  53
  54 /**
  55  * CPPMAGIC_NONZERO - is argument not '0'
  56  *
  57  * CPPMAGIC_NONZERO(@a)
  58  *      expands to '0' if @a is '0', otherwise expands to '1'.
  59  */
  60 #define CPPMAGIC_NONZERO(a_)            CPPMAGIC_ISZERO(CPPMAGIC_ISZERO(a_))
  61
  62 /**
  63  * CPPMAGIC_NONEMPTY - does the macro have any arguments?
  64  *
  65  * CPPMAGIC_NONEMPTY()
  66  *      expands to '0'
  67  * CPPMAGIC_NONEMPTY(@a)
  68  * CPPMAGIC_NONEMPTY(@a, ...)
  69  *      expand to '1'
  70  */
  71 #define _CPPMAGIC_EOA()                 0
  72 #define CPPMAGIC_NONEMPTY(...)          \
  73         CPPMAGIC_NONZERO(CPPMAGIC_1ST(_CPPMAGIC_EOA __VA_ARGS__)())
  74
  75 /**
  76  * CPPMAGIC_ISEMPTY - does the macro have no arguments?
  77  *
  78  * CPPMAGIC_ISEMPTY()
  79  *      expands to '1'
  80  * CPPMAGIC_ISEMPTY(@a)
  81  * CPPMAGIC_ISEMPTY(@a, ...)
  82  *      expand to '0'
  83  */
  84 #define CPPMAGIC_ISEMPTY(...)           \
  85         CPPMAGIC_ISZERO(CPPMAGIC_NONEMPTY(__VA_ARGS__))
  86
  87 /*
  88  * CPPMAGIC_IFELSE - preprocessor conditional
  89  *
  90  * CPPMAGIC_IFELSE(@cond)(@if)(@else)
  91  *      expands to @else if @cond is '0', otherwise expands to @if
  92  */
  93 #define _CPPMAGIC_IF_0(...)             _CPPMAGIC_IF_0_ELSE
  94 #define _CPPMAGIC_IF_1(...)             __VA_ARGS__ _CPPMAGIC_IF_1_ELSE
  95 #define _CPPMAGIC_IF_0_ELSE(...)        __VA_ARGS__
  96 #define _CPPMAGIC_IF_1_ELSE(...)
  97 #define _CPPMAGIC_IFELSE(cond_)         CPPMAGIC_GLUE2(_CPPMAGIC_IF_, cond_)
  98 #define CPPMAGIC_IFELSE(cond_)          \
  99         _CPPMAGIC_IFELSE(CPPMAGIC_NONZERO(cond_))
 100
 101 /**
 102  * CPPMAGIC_EVAL - force multiple expansion passes
 103  *
 104  * Forces macros in the arguments to be expanded repeatedly (up to
 105  * 1024 times) even when CPP would usually stop expanding.
 106  */
 107 #define CPPMAGIC_EVAL1(...)             __VA_ARGS__
 108 #define CPPMAGIC_EVAL2(...)             \
 109         CPPMAGIC_EVAL1(CPPMAGIC_EVAL1(__VA_ARGS__))
 110 #define CPPMAGIC_EVAL4(...)             \
 111         CPPMAGIC_EVAL2(CPPMAGIC_EVAL2(__VA_ARGS__))
 112 #define CPPMAGIC_EVAL8(...)             \
 113         CPPMAGIC_EVAL4(CPPMAGIC_EVAL4(__VA_ARGS__))
 114 #define CPPMAGIC_EVAL16(...)            \
 115         CPPMAGIC_EVAL8(CPPMAGIC_EVAL8(__VA_ARGS__))
 116 #define CPPMAGIC_EVAL32(...)            \
 117         CPPMAGIC_EVAL16(CPPMAGIC_EVAL16(__VA_ARGS__))
 118 #define CPPMAGIC_EVAL64(...)            \
 119         CPPMAGIC_EVAL32(CPPMAGIC_EVAL32(__VA_ARGS__))
 120 #define CPPMAGIC_EVAL128(...)           \
 121         CPPMAGIC_EVAL64(CPPMAGIC_EVAL64(__VA_ARGS__))
 122 #define CPPMAGIC_EVAL256(...)           \
 123         CPPMAGIC_EVAL128(CPPMAGIC_EVAL128(__VA_ARGS__))
 124 #define CPPMAGIC_EVAL512(...)           \
 125         CPPMAGIC_EVAL256(CPPMAGIC_EVAL256(__VA_ARGS__))
 126 #define CPPMAGIC_EVAL1024(...)          \
 127         CPPMAGIC_EVAL512(CPPMAGIC_EVAL512(__VA_ARGS__))
 128 #define CPPMAGIC_EVAL(...)              CPPMAGIC_EVAL1024(__VA_ARGS__)
 129
 130 /**
 131  * CPPMAGIC_DEFER1, CPPMAGIC_DEFER2 - defer expansion
 132  */
 133 #define CPPMAGIC_DEFER1(a_)     a_ CPPMAGIC_NOTHING()
 134 #define CPPMAGIC_DEFER2(a_)     a_ CPPMAGIC_NOTHING CPPMAGIC_NOTHING()()
 135
 136 /**
 137  * CPPMAGIC_MAP - iterate another macro across arguments
 138  * @m: name of a one argument macro
 139  *
 140  * CPPMAGIC_MAP(@m, @a1, @a2, ... @an)
 141  *      expands to the expansion of @m(@a1) , @m(@a2) , ... , @m(@an)
 142  */
 143 #define _CPPMAGIC_MAP_()                _CPPMAGIC_MAP
 144 #define _CPPMAGIC_MAP(m_, a_, ...)                                      \
 145         m_(a_)                                                          \
 146         CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))                 \
 147                 (, CPPMAGIC_DEFER2(_CPPMAGIC_MAP_)()(m_, __VA_ARGS__))  \
 148                 ()
 149 #define CPPMAGIC_MAP(m_, ...)                                           \
 150         CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))                 \
 151                 (CPPMAGIC_EVAL(_CPPMAGIC_MAP(m_, __VA_ARGS__)))         \
 152                 ()
 153
 154 /**
 155  * CPPMAGIC_2MAP - iterate another macro across pairs of arguments
 156  * @m: name of a two argument macro
 157  *
 158  * CPPMAGIC_2MAP(@m, @a1, @b1, @a2, @b2, ..., @an, @bn)
 159  *      expands to the expansion of
 160  *               @m(@a1, @b1) , @m(@a2, @b2) , ... , @m(@an, @bn)
 161  */
 162 #define _CPPMAGIC_2MAP_()               _CPPMAGIC_2MAP
 163 #define _CPPMAGIC_2MAP(m_, a_, b_, ...)                         \
 164         m_(a_, b_)                                                      \
 165         CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))                 \
 166                 (, CPPMAGIC_DEFER2(_CPPMAGIC_2MAP_)()(m_, __VA_ARGS__)) \
 167                 ()
 168 #define CPPMAGIC_2MAP(m_, ...)                                  \
 169         CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))                 \
 170                 (CPPMAGIC_EVAL(_CPPMAGIC_2MAP(m_, __VA_ARGS__)))        \
 171                 ()
 172
 173 /**
 174  * CPPMAGIC_JOIN - separate arguments with given delimiter
 175  * @d: delimiter
 176  *
 177  * CPPMAGIC_JOIN(@d, @a1, @a2, ..., @an)
 178  *      expands to the expansion of @a1 @d @a2 @d ... @d @an
 179  */
 180 #define _CPPMAGIC_JOIN_()               _CPPMAGIC_JOIN
 181 #define _CPPMAGIC_JOIN(d_, a_, ...)                                     \
 182         a_                                                              \
 183         CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))                 \
 184                 (d_ CPPMAGIC_DEFER2(_CPPMAGIC_JOIN_)()(d_, __VA_ARGS__)) \
 185                 ()
 186 #define CPPMAGIC_JOIN(d_, ...)                                  \
 187         CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))                 \
 188                 (CPPMAGIC_EVAL(_CPPMAGIC_JOIN(d_, __VA_ARGS__)))        \
 189                 ()
 190
 191 #endif /* CCAN_CPPMAGIC_H */