damus/damus-c/cppmagic.h

/* MIT (BSD) license - see LICENSE file for details */
#ifndef CCAN_CPPMAGIC_H
#define CCAN_CPPMAGIC_H

/**
 * CPPMAGIC_NOTHING - expands to nothing
 */
#define CPPMAGIC_NOTHING()

/**
 * CPPMAGIC_STRINGIFY - convert arguments to a string literal
 */
#define _CPPMAGIC_STRINGIFY(...)    #__VA_ARGS__
#define CPPMAGIC_STRINGIFY(...)        _CPPMAGIC_STRINGIFY(__VA_ARGS__)

/**
 * CPPMAGIC_GLUE2 - glue arguments together
 *
 * CPPMAGIC_GLUE2(@a_, @b_)
 *    expands to the expansion of @a_ followed immediately
 *    (combining tokens) by the expansion of @b_
 */
#define _CPPMAGIC_GLUE2(a_, b_)        a_##b_
#define CPPMAGIC_GLUE2(a_, b_)        _CPPMAGIC_GLUE2(a_, b_)

/**
 * CPPMAGIC_1ST - return 1st argument
 *
 * CPPMAGIC_1ST(@a_, ...)
 *    expands to the expansion of @a_
 */
#define CPPMAGIC_1ST(a_, ...)        a_

/**
 * CPPMAGIC_2ND - return 2nd argument
 *
 * CPPMAGIC_2ST(@a_, @b_, ...)
 *    expands to the expansion of @b_
 */
#define CPPMAGIC_2ND(a_, b_, ...)    b_

/**
 * CPPMAGIC_ISZERO - is argument '0'
 *
 * CPPMAGIC_ISZERO(@a)
 *    expands to '1' if @a is '0', otherwise expands to '0'.
 */
#define _CPPMAGIC_ISPROBE(...)        CPPMAGIC_2ND(__VA_ARGS__, 0)
#define _CPPMAGIC_PROBE()        $, 1
#define _CPPMAGIC_ISZERO_0        _CPPMAGIC_PROBE()
#define CPPMAGIC_ISZERO(a_)        \
    _CPPMAGIC_ISPROBE(CPPMAGIC_GLUE2(_CPPMAGIC_ISZERO_, a_))

/**
 * CPPMAGIC_NONZERO - is argument not '0'
 *
 * CPPMAGIC_NONZERO(@a)
 *    expands to '0' if @a is '0', otherwise expands to '1'.
 */
#define CPPMAGIC_NONZERO(a_)        CPPMAGIC_ISZERO(CPPMAGIC_ISZERO(a_))

/**
 * CPPMAGIC_NONEMPTY - does the macro have any arguments?
 *
 * CPPMAGIC_NONEMPTY()
 *     expands to '0'
 * CPPMAGIC_NONEMPTY(@a)
 * CPPMAGIC_NONEMPTY(@a, ...)
 *     expand to '1'
 */
#define _CPPMAGIC_EOA()            0
#define CPPMAGIC_NONEMPTY(...)        \
    CPPMAGIC_NONZERO(CPPMAGIC_1ST(_CPPMAGIC_EOA __VA_ARGS__)())

/**
 * CPPMAGIC_ISEMPTY - does the macro have no arguments?
 *
 * CPPMAGIC_ISEMPTY()
 *     expands to '1'
 * CPPMAGIC_ISEMPTY(@a)
 * CPPMAGIC_ISEMPTY(@a, ...)
 *     expand to '0'
 */
#define CPPMAGIC_ISEMPTY(...)        \
    CPPMAGIC_ISZERO(CPPMAGIC_NONEMPTY(__VA_ARGS__))

/*
 * CPPMAGIC_IFELSE - preprocessor conditional
 *
 * CPPMAGIC_IFELSE(@cond)(@if)(@else)
 *    expands to @else if @cond is '0', otherwise expands to @if
 */
#define _CPPMAGIC_IF_0(...)        _CPPMAGIC_IF_0_ELSE
#define _CPPMAGIC_IF_1(...)        __VA_ARGS__ _CPPMAGIC_IF_1_ELSE
#define _CPPMAGIC_IF_0_ELSE(...)    __VA_ARGS__
#define _CPPMAGIC_IF_1_ELSE(...)
#define _CPPMAGIC_IFELSE(cond_)        CPPMAGIC_GLUE2(_CPPMAGIC_IF_, cond_)
#define CPPMAGIC_IFELSE(cond_)        \
    _CPPMAGIC_IFELSE(CPPMAGIC_NONZERO(cond_))

/**
 * CPPMAGIC_EVAL - force multiple expansion passes
 *
 * Forces macros in the arguments to be expanded repeatedly (up to
 * 1024 times) even when CPP would usually stop expanding.
 */
#define CPPMAGIC_EVAL1(...)        __VA_ARGS__
#define CPPMAGIC_EVAL2(...)        \
    CPPMAGIC_EVAL1(CPPMAGIC_EVAL1(__VA_ARGS__))
#define CPPMAGIC_EVAL4(...)        \
    CPPMAGIC_EVAL2(CPPMAGIC_EVAL2(__VA_ARGS__))
#define CPPMAGIC_EVAL8(...)        \
    CPPMAGIC_EVAL4(CPPMAGIC_EVAL4(__VA_ARGS__))
#define CPPMAGIC_EVAL16(...)        \
    CPPMAGIC_EVAL8(CPPMAGIC_EVAL8(__VA_ARGS__))
#define CPPMAGIC_EVAL32(...)        \
    CPPMAGIC_EVAL16(CPPMAGIC_EVAL16(__VA_ARGS__))
#define CPPMAGIC_EVAL64(...)        \
    CPPMAGIC_EVAL32(CPPMAGIC_EVAL32(__VA_ARGS__))
#define CPPMAGIC_EVAL128(...)        \
    CPPMAGIC_EVAL64(CPPMAGIC_EVAL64(__VA_ARGS__))
#define CPPMAGIC_EVAL256(...)        \
    CPPMAGIC_EVAL128(CPPMAGIC_EVAL128(__VA_ARGS__))
#define CPPMAGIC_EVAL512(...)        \
    CPPMAGIC_EVAL256(CPPMAGIC_EVAL256(__VA_ARGS__))
#define CPPMAGIC_EVAL1024(...)        \
    CPPMAGIC_EVAL512(CPPMAGIC_EVAL512(__VA_ARGS__))
#define CPPMAGIC_EVAL(...)        CPPMAGIC_EVAL1024(__VA_ARGS__)

/**
 * CPPMAGIC_DEFER1, CPPMAGIC_DEFER2 - defer expansion
 */
#define CPPMAGIC_DEFER1(a_)    a_ CPPMAGIC_NOTHING()
#define CPPMAGIC_DEFER2(a_)    a_ CPPMAGIC_NOTHING CPPMAGIC_NOTHING()()

/**
 * CPPMAGIC_MAP - iterate another macro across arguments
 * @m: name of a one argument macro
 *
 * CPPMAGIC_MAP(@m, @a1, @a2, ... @an)
 *    expands to the expansion of @m(@a1) , @m(@a2) , ... , @m(@an)
 */
#define _CPPMAGIC_MAP_()        _CPPMAGIC_MAP
#define _CPPMAGIC_MAP(m_, a_, ...)                    \
    m_(a_)                                \
    CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))            \
        (, CPPMAGIC_DEFER2(_CPPMAGIC_MAP_)()(m_, __VA_ARGS__))    \
        ()
#define CPPMAGIC_MAP(m_, ...)                        \
    CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))            \
        (CPPMAGIC_EVAL(_CPPMAGIC_MAP(m_, __VA_ARGS__)))        \
        ()

/**
 * CPPMAGIC_2MAP - iterate another macro across pairs of arguments
 * @m: name of a two argument macro
 *
 * CPPMAGIC_2MAP(@m, @a1, @b1, @a2, @b2, ..., @an, @bn)
 *    expands to the expansion of
 *         @m(@a1, @b1) , @m(@a2, @b2) , ... , @m(@an, @bn)
 */
#define _CPPMAGIC_2MAP_()        _CPPMAGIC_2MAP
#define _CPPMAGIC_2MAP(m_, a_, b_, ...)                \
    m_(a_, b_)                            \
    CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))            \
        (, CPPMAGIC_DEFER2(_CPPMAGIC_2MAP_)()(m_, __VA_ARGS__)) \
        ()
#define CPPMAGIC_2MAP(m_, ...)                    \
    CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))            \
        (CPPMAGIC_EVAL(_CPPMAGIC_2MAP(m_, __VA_ARGS__)))    \
        ()

/**
 * CPPMAGIC_JOIN - separate arguments with given delimiter
 * @d: delimiter
 *
 * CPPMAGIC_JOIN(@d, @a1, @a2, ..., @an)
 *    expands to the expansion of @a1 @d @a2 @d ... @d @an
 */
#define _CPPMAGIC_JOIN_()        _CPPMAGIC_JOIN
#define _CPPMAGIC_JOIN(d_, a_, ...)                    \
    a_                                \
    CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))            \
        (d_ CPPMAGIC_DEFER2(_CPPMAGIC_JOIN_)()(d_, __VA_ARGS__)) \
        ()
#define CPPMAGIC_JOIN(d_, ...)                    \
    CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))            \
        (CPPMAGIC_EVAL(_CPPMAGIC_JOIN(d_, __VA_ARGS__)))    \
        ()

#endif /* CCAN_CPPMAGIC_H */