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101 lines
3.6 KiB
C
101 lines
3.6 KiB
C
/*
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* BIRD Macro Tricks
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*
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* (c) 2018 Jan Maria Matejka <mq@jmq.cz>
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*
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* Can be freely distributed and used under the terms of the GNU GPL.
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*
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* Contains useful but dirty macro tricks:
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* MACRO_CONCAT(a, b) -> concatenates a##b
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* MACRO_BOOL(x) -> convert 0 to 0, anything else to 1
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* MACRO_IFELSE(b)(true-branch)(false-branch)
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* -> b shall be 0 or 1; expands to the appropriate branch
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* MACRO_ISEMPTY(...) -> 1 for empty argument list, 0 otherwise
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* MACRO_FOREACH(func, ...)
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* -> calling FOREACH(func, a, b, c, d) expands to
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* func(a) func(b) func(c) func(d)
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* MACRO_RPACK(func, terminator, ...)
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* -> packs the list into recursive calls:
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* func(func(func(func(terminator, a), b), c), d)
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*/
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#ifndef _BIRD_MACRO_H_
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#define _BIRD_MACRO_H_
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/* What to do with args */
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#define MACRO_DROP(...)
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#define MACRO_UNPAREN(...) __VA_ARGS__
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#define MACRO_SEP(a, b, sep) a sep b
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#define MACRO_STR(a) #a
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#define MACRO_STR_AFTER(a) MACRO_STR(a)
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/* Aliases for some special chars */
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#define MACRO_COMMA ,
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#define MACRO_LPAREN (
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#define MACRO_RPAREN )
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#define MACRO_LPAREN_() (
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#define MACRO_RPAREN_() )
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/* Multiple expansion trick */
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#define MACRO_EXPAND0(...) __VA_ARGS__
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#define MACRO_EXPAND1(...) MACRO_EXPAND0(MACRO_EXPAND0(__VA_ARGS__))
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#define MACRO_EXPAND2(...) MACRO_EXPAND1(MACRO_EXPAND1(__VA_ARGS__))
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#define MACRO_EXPAND3(...) MACRO_EXPAND2(MACRO_EXPAND2(__VA_ARGS__))
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#define MACRO_EXPAND(...) MACRO_EXPAND3(MACRO_EXPAND3(__VA_ARGS__))
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/* Deferring expansion in the expansion trick */
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#define MACRO_EMPTY()
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#define MACRO_DEFER(t) t MACRO_EMPTY()
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#define MACRO_DEFER2(t) t MACRO_EMPTY MACRO_EMPTY()()
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#define MACRO_DEFER3(t) t MACRO_EMPTY MACRO_EMPTY MACRO_EMPTY()()()
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/* Token concatenation */
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#define MACRO_CONCAT(prefix, ...) prefix##__VA_ARGS__
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#define MACRO_CONCAT_AFTER(...) MACRO_CONCAT(__VA_ARGS__)
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/* Get first or second argument only */
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#define MACRO_FIRST(a, ...) a
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#define MACRO_SECOND(a, b, ...) b
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#define MACRO_SECOND_OR_ZERO(...) MACRO_SECOND(__VA_ARGS__, 0,)
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/* Macro Boolean auxiliary macros */
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#define MACRO_BOOL_CHECK_0 ~, 1
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#define MACRO_BOOL_NEG(x) MACRO_SECOND_OR_ZERO(MACRO_CONCAT(MACRO_BOOL_CHECK_, x))
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#define MACRO_BOOL_NOT_0 1
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#define MACRO_BOOL_NOT_1 0
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/* Macro Boolean negation */
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#define MACRO_NOT(x) MACRO_CONCAT(MACRO_BOOL_NOT_, x)
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/* Convert anything to bool (anything -> 1, 0 -> 0) */
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#define MACRO_BOOL(x) MACRO_NOT(MACRO_BOOL_NEG(x))
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/*
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* Macro If/Else condition
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* Usage: MACRO_IFELSE(condition)(true-branch)(false-branch)
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* Expands to true-branch if condition is true, otherwise to false-branch.
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*/
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#define MACRO_IFELSE(b) MACRO_CONCAT(MACRO_IFELSE_, b)
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#define MACRO_IFELSE_0(...) MACRO_UNPAREN
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#define MACRO_IFELSE_1(...) __VA_ARGS__ MACRO_DROP
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/* Auxiliary macros for MACRO_FOREACH */
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#define MACRO_ISLAST(...) MACRO_BOOL_NEG(MACRO_FIRST(MACRO_ISLAST_CHECK __VA_ARGS__)())
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#define MACRO_ISLAST_CHECK() 0
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#define MACRO_FOREACH_EXPAND(call, a, ...) MACRO_IFELSE(MACRO_ISLAST(__VA_ARGS__))(call(a))(call(a) MACRO_DEFER2(MACRO_FOREACH_PAREN)()(call, __VA_ARGS__))
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#define MACRO_FOREACH_PAREN() MACRO_FOREACH_EXPAND
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#define MACRO_RPACK_EXPAND(call, terminator, a, ...) MACRO_IFELSE(MACRO_ISLAST(__VA_ARGS__))(call(terminator, a))(call(MACRO_DEFER2(MACRO_RPACK_PAREN)()(call, terminator, __VA_ARGS__), a))
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#define MACRO_RPACK_PAREN() MACRO_RPACK_EXPAND
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/*
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* Call the first argument for each following:
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* MACRO_FOREACH(func, a, b, c, d) expands to func(a) func(b) func(c) func(d).
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* It supports also macros as func.
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*/
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#define MACRO_FOREACH(call, ...) MACRO_EXPAND(MACRO_FOREACH_EXPAND(call, __VA_ARGS__))
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#define MACRO_RPACK(call, terminator, ...) MACRO_EXPAND(MACRO_RPACK_EXPAND(call, terminator, __VA_ARGS__))
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#endif
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