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MINOR: standard: Add my_ffsl function to get the position of the bit set to one

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This commit is contained in:
Christopher Faulet 2017-11-22 15:00:13 +01:00 committed by Willy Tarreau
parent f1f0c5f591
commit ff8131861f
1 changed files with 40 additions and 0 deletions
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40
include/common/standard.h
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@ -793,6 +793,46 @@ static inline unsigned int my_popcountl(unsigned long a)
return cnt; return cnt;
} }
/* Simple ffs implementation. It returns the position of the lowest bit set to
* one. */
static inline unsigned int my_ffsl(unsigned long a)
{
unsigned int cnt;
if (!a)
return 0;
cnt = 1;
#if LONG_MAX > 0x7FFFFFFFL /* 64bits */
if (!(a & 0xFFFFFFFFUL)) {
a >>= 32;
cnt += 32;
}
#endif
if (!(a & 0XFFFFU)) {
a >>= 16;
cnt += 16;
}
if (!(a & 0XFF)) {
a >>= 8;
cnt += 8;
}
if (!(a & 0xf)) {
a >>= 4;
cnt += 4;
}
if (!(a & 0x3)) {
a >>= 2;
cnt += 2;
}
if (!(a & 0x1)) {
a >>= 1;
cnt += 1;
}
return cnt;
}
/* Build a word with the <bits> lower bits set (reverse of my_popcountl) */ /* Build a word with the <bits> lower bits set (reverse of my_popcountl) */
static inline unsigned long nbits(int bits) static inline unsigned long nbits(int bits)
{ {