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| author | Kimplul <kimi.h.kuparinen@gmail.com> | 2022-10-29 20:10:09 +0300 |
|---|---|---|
| committer | Kimplul <kimi.h.kuparinen@gmail.com> | 2022-10-29 20:10:09 +0300 |
| commit | 6303dd9b55a1871387122525e456747eeb860932 (patch) | |
| tree | 5ade67069f4b7f1e3d85e31c295da4f0b17c4141 /common/bits.c | |
| parent | e2631ad54db87b71943040dcb5a2fc0f4b850716 (diff) | |
| download | kmi-6303dd9b55a1871387122525e456747eeb860932.tar.gz kmi-6303dd9b55a1871387122525e456747eeb860932.zip | |
rewrite pmem
Diffstat (limited to 'common/bits.c')
| -rw-r--r-- | common/bits.c | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/common/bits.c b/common/bits.c index 2efbe2f..5691617 100644 --- a/common/bits.c +++ b/common/bits.c @@ -36,3 +36,23 @@ __weak uint64_t __bswap64(const uint64_t u) (u & 0x000000000000ff00ULL) << 40 | (u & 0x00000000000000ffULL) << 56; } + +#undef ffs +__weak int ffs(int v) +{ + /* http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightParallel */ + if (v == 0) + return 0; + + int c = 32; + v &= -v; + + if (v) c--; + if (v & 0x0000FFFF) c -= 16; + if (v & 0x00FF00FF) c -= 8; + if (v & 0x0F0F0F0F) c -= 4; + if (v & 0x33333333) c -= 2; + if (v & 0x55555555) c -= 1; + + return c + 1; +} |