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util: add log2u(), log2u_round_up()

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Two's logarithms for unsigned.
This commit is contained in:
Michal Schmidt 2014-10-15 01:28:54 +02:00
parent a09abc4ae0
commit b5de6d9842
1 changed files with 15 additions and 0 deletions
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15
src/shared/util.h
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@ -830,6 +830,21 @@ static inline int log2i(int x) {
return __SIZEOF_INT__ * 8 - __builtin_clz(x) - 1;
}
static inline unsigned log2u(unsigned x) {
assert(x > 0);
return sizeof(unsigned) * 8 - __builtin_clz(x) - 1;
}
static inline unsigned log2u_round_up(unsigned x) {
assert(x > 0);
if (x == 1)
return 0;
return log2u(x - 1) + 1;
}
static inline bool logind_running(void) {
return access("/run/systemd/seats/", F_OK) >= 0;
}