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sys/util.h: add UTIL_OR and UTIL_AND

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These are short-circuiting utility helpers that can save typing
in situations where avoiding evaluation of the not-taken branch
skips invalid expressions.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>
This commit is contained in:
Martí Bolívar 2020-03-24 16:22:33 -07:00 • committed by Carles Cufí
commit 1edc84f526
2 changed files with 50 additions and 0 deletions
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15
include/sys/util.h
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@ -711,6 +711,21 @@ u8_t u8_to_dec(char *buf, u8_t buflen, u8_t value);
#define UTIL_IF(c) UTIL_IIF(UTIL_BOOL(c))
/*
* These are like || and &&, but they do evaluation and
* short-circuiting at preprocessor time instead of runtime.
*
* UTIL_OR(foo, bar) is sometimes a replacement for (foo || bar)
* when "bar" is an expression that would cause a build
* error when "foo" is true.
*
* UTIL_AND(foo, bar) is sometimes a replacement for (foo && bar)
* when "bar" is an expression that would cause a build
* error when "foo" is false.
*/
#define UTIL_OR(a, b) COND_CODE_1(UTIL_BOOL(a), (a), (b))
#define UTIL_AND(a, b) COND_CODE_1(UTIL_BOOL(a), (b), (0))
#define UTIL_EAT(...)
#define UTIL_EXPAND(...) __VA_ARGS__
#define UTIL_WHEN(c) UTIL_IF(c)(UTIL_EXPAND, UTIL_EAT)