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macro: add macro for checking if integer is power of 2

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This commit is contained in:
Lennart Poettering 2022-08-05 13:16:27 +02:00
parent 14e7bc2e77
commit c51e4c796d
2 changed files with 69 additions and 0 deletions
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13
src/fundamental/macro-fundamental.h
View File

@ -200,6 +200,19 @@
MIN(_c, z); \ MIN(_c, z); \
}) })
/* Returns true if the passed integer is a positive power of two */
#define CONST_ISPOWEROF2(x) \
((x) > 0 && ((x) & ((x) - 1)) == 0)
#define ISPOWEROF2(x) \
__builtin_choose_expr( \
__builtin_constant_p(x), \
CONST_ISPOWEROF2(x), \
({ \
const typeof(x) _x = (x); \
CONST_ISPOWEROF2(_x); \
}))
#define LESS_BY(a, b) __LESS_BY(UNIQ, (a), UNIQ, (b)) #define LESS_BY(a, b) __LESS_BY(UNIQ, (a), UNIQ, (b))
#define __LESS_BY(aq, a, bq, b) \ #define __LESS_BY(aq, a, bq, b) \
({ \ ({ \

56
src/test/test-macro.c
View File

@ -465,4 +465,60 @@ TEST(PTR_SUB1) {
assert_se(!p); assert_se(!p);
} }
TEST(ISPOWEROF2) {
uint64_t u;
int64_t i;
/* First, test constant expressions */
assert_se(!ISPOWEROF2(-2));
assert_se(!ISPOWEROF2(-1));
assert_se(!ISPOWEROF2(0));
assert_se(ISPOWEROF2(1));
assert_se(ISPOWEROF2(2));
assert_se(!ISPOWEROF2(3));
assert_se(ISPOWEROF2(4));
assert_se(!ISPOWEROF2(5));
assert_se(!ISPOWEROF2(6));
assert_se(!ISPOWEROF2(7));
assert_se(ISPOWEROF2(8));
assert_se(!ISPOWEROF2(9));
assert_se(!ISPOWEROF2(1022));
assert_se(ISPOWEROF2(1024));
assert_se(!ISPOWEROF2(1025));
assert_se(!ISPOWEROF2(UINT64_C(0xffffffff)));
assert_se(ISPOWEROF2(UINT64_C(0x100000000)));
assert_se(!ISPOWEROF2(UINT64_C(0x100000001)));
/* Then, test dynamic expressions, and if they are side-effect free */
i = -2;
assert_se(!ISPOWEROF2(i++));
assert_se(i == -1);
assert_se(!ISPOWEROF2(i++));
assert_se(i == 0);
assert_se(!ISPOWEROF2(i++));
assert_se(i == 1);
assert_se(ISPOWEROF2(i++));
assert_se(i == 2);
assert_se(ISPOWEROF2(i++));
assert_se(i == 3);
assert_se(!ISPOWEROF2(i++));
assert_se(i == 4);
assert_se(ISPOWEROF2(i++));
assert_se(i == 5);
assert_se(!ISPOWEROF2(i));
u = 0;
assert_se(!ISPOWEROF2(u++));
assert_se(u == 1);
assert_se(ISPOWEROF2(u++));
assert_se(u == 2);
assert_se(ISPOWEROF2(u++));
assert_se(u == 3);
assert_se(!ISPOWEROF2(u++));
assert_se(u == 4);
assert_se(ISPOWEROF2(u++));
assert_se(u == 5);
assert_se(!ISPOWEROF2(u));
}
DEFINE_TEST_MAIN(LOG_INFO); DEFINE_TEST_MAIN(LOG_INFO);