Annotation of embedaddon/bird2/lib/macro.h, revision 1.1.1.1
1.1 misho 1: /*
2: * BIRD Macro Tricks
3: *
4: * (c) 2018 Jan Maria Matejka <mq@jmq.cz>
5: *
6: * Can be freely distributed and used under the terms of the GNU GPL.
7: *
8: * Contains useful but dirty macro tricks:
9: * MACRO_CONCAT(a, b) -> concatenates a##b
10: * MACRO_BOOL(x) -> convert 0 to 0, anything else to 1
11: * MACRO_IFELSE(b)(true-branch)(false-branch)
12: * -> b shall be 0 or 1; expands to the appropriate branch
13: * MACRO_ISEMPTY(...) -> 1 for empty argument list, 0 otherwise
14: * MACRO_FOREACH(func, ...)
15: * -> calling FOREACH(func, a, b, c, d) expands to
16: * func(a) func(b) func(c) func(d)
17: * MACRO_RPACK(func, terminator, ...)
18: * -> packs the list into recursive calls:
19: * func(func(func(func(terminator, a), b), c), d)
20: */
21:
22: #ifndef _BIRD_MACRO_H_
23: #define _BIRD_MACRO_H_
24:
25: /* What to do with args */
26: #define MACRO_DROP(...)
27: #define MACRO_UNPAREN(...) __VA_ARGS__
28: #define MACRO_SEP(a, b, sep) a sep b
29:
30: /* Aliases for some special chars */
31: #define MACRO_COMMA ,
32: #define MACRO_LPAREN (
33: #define MACRO_RPAREN )
34: #define MACRO_LPAREN_() (
35: #define MACRO_RPAREN_() )
36:
37: /* Multiple expansion trick */
38: #define MACRO_EXPAND0(...) __VA_ARGS__
39: #define MACRO_EXPAND1(...) MACRO_EXPAND0(MACRO_EXPAND0(__VA_ARGS__))
40: #define MACRO_EXPAND2(...) MACRO_EXPAND1(MACRO_EXPAND1(__VA_ARGS__))
41: #define MACRO_EXPAND3(...) MACRO_EXPAND2(MACRO_EXPAND2(__VA_ARGS__))
42: #define MACRO_EXPAND(...) MACRO_EXPAND3(MACRO_EXPAND3(__VA_ARGS__))
43:
44: /* Deferring expansion in the expansion trick */
45: #define MACRO_EMPTY()
46: #define MACRO_DEFER(t) t MACRO_EMPTY()
47: #define MACRO_DEFER2(t) t MACRO_EMPTY MACRO_EMPTY()()
48: #define MACRO_DEFER3(t) t MACRO_EMPTY MACRO_EMPTY MACRO_EMPTY()()()
49:
50: /* Token concatenation */
51: #define MACRO_CONCAT(prefix, ...) prefix##__VA_ARGS__
52: #define MACRO_CONCAT_AFTER(...) MACRO_CONCAT(__VA_ARGS__)
53:
54: /* Get first or second argument only */
55: #define MACRO_FIRST(a, ...) a
56: #define MACRO_SECOND(a, b, ...) b
57: #define MACRO_SECOND_OR_ZERO(...) MACRO_SECOND(__VA_ARGS__, 0,)
58:
59: /* Macro Boolean auxiliary macros */
60: #define MACRO_BOOL_CHECK_0 ~, 1
61: #define MACRO_BOOL_NEG(x) MACRO_SECOND_OR_ZERO(MACRO_CONCAT(MACRO_BOOL_CHECK_, x))
62:
63: #define MACRO_BOOL_NOT_0 1
64: #define MACRO_BOOL_NOT_1 0
65:
66: /* Macro Boolean negation */
67: #define MACRO_NOT(x) MACRO_CONCAT(MACRO_BOOL_NOT_, x)
68:
69: /* Convert anything to bool (anything -> 1, 0 -> 0) */
70: #define MACRO_BOOL(x) MACRO_NOT(MACRO_BOOL_NEG(x))
71:
72: /*
73: * Macro If/Else condition
74: * Usage: MACRO_IFELSE(condition)(true-branch)(false-branch)
75: * Expands to true-branch if condition is true, otherwise to false-branch.
76: */
77: #define MACRO_IFELSE(b) MACRO_CONCAT(MACRO_IFELSE_, b)
78: #define MACRO_IFELSE_0(...) MACRO_UNPAREN
79: #define MACRO_IFELSE_1(...) __VA_ARGS__ MACRO_DROP
80:
81: /* Auxiliary macros for MACRO_FOREACH */
82: #define MACRO_ISLAST(...) MACRO_BOOL_NEG(MACRO_FIRST(MACRO_ISLAST_CHECK __VA_ARGS__)())
83: #define MACRO_ISLAST_CHECK() 0
84:
85: #define MACRO_FOREACH_EXPAND(call, a, ...) MACRO_IFELSE(MACRO_ISLAST(__VA_ARGS__))(call(a))(call(a) MACRO_DEFER2(MACRO_FOREACH_PAREN)()(call, __VA_ARGS__))
86: #define MACRO_FOREACH_PAREN() MACRO_FOREACH_EXPAND
87:
88: #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))
89: #define MACRO_RPACK_PAREN() MACRO_RPACK_EXPAND
90: /*
91: * Call the first argument for each following:
92: * MACRO_FOREACH(func, a, b, c, d) expands to func(a) func(b) func(c) func(d).
93: * It supports also macros as func.
94: */
95: #define MACRO_FOREACH(call, ...) MACRO_EXPAND(MACRO_FOREACH_EXPAND(call, __VA_ARGS__))
96: #define MACRO_RPACK(call, terminator, ...) MACRO_EXPAND(MACRO_RPACK_EXPAND(call, terminator, __VA_ARGS__))
97:
98: #endif
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