Author: scottph Date: Wed Aug 26 02:07:46 2020 New Revision: 364796 URL: https://svnweb.freebsd.org/changeset/base/364796
Log: bitset: add BIT_FFS_AT() for finding the first bit set greater than a start bit Reviewed by: kib Approved by: scottl (implicit) MFC after: 1 week Sponsored by: Ampere Computing, Inc. Differential Revision: https://reviews.freebsd.org/D26128 Modified: head/share/man/man9/bitset.9 head/sys/sys/bitset.h Modified: head/share/man/man9/bitset.9 ============================================================================== --- head/share/man/man9/bitset.9 Wed Aug 26 02:05:58 2020 (r364795) +++ head/share/man/man9/bitset.9 Wed Aug 26 02:07:46 2020 (r364796) @@ -24,7 +24,7 @@ .\" .\" $FreeBSD$ .\" -.Dd December 12, 2019 +.Dd August 25, 2020 .Dt BITSET 9 .Os .Sh NAME @@ -43,6 +43,7 @@ .Nm BIT_EMPTY , .Nm BIT_ISFULLSET , .Nm BIT_FFS , +.Nm BIT_FFS_AT , .Nm BIT_FLS , .Nm BIT_COUNT , .Nm BIT_SUBSET , @@ -86,6 +87,8 @@ .Ft int .Fn BIT_FFS "const SETSIZE" "struct STRUCTNAME *bitset" .Ft int +.Fn BIT_FFS_AT "const SETSIZE" "struct STRUCTNAME *bitset" "int start" +.Ft int .Fn BIT_FLS "const SETSIZE" "struct STRUCTNAME *bitset" .Ft int .Fn BIT_COUNT "const SETSIZE" "struct STRUCTNAME *bitset" @@ -285,6 +288,18 @@ index parameter to any other macro, you must subtract one from the result. .Pp The +.Fn BIT_FFS_AT +macro returns the 1-index of the first (lowest) set bit in +.Fa bitset , +which is greater than the given 1-indexed +.Fa start , +or zero if no bits in +.Fa bitset +greater than +.Fa start +are set. +.Pp +The .Fn BIT_FLS macro returns the 1-index of the last (highest) set bit in .Fa bitset , @@ -518,7 +533,8 @@ argument to all of these macros must match the value g .Fn BITSET_DEFINE . .Pp Unlike every other reference to individual set members, which are zero-indexed, -.Fn BIT_FFS +.Fn BIT_FFS , +.Fn BIT_FFS_AT and .Fn BIT_FLS return a one-indexed result (or zero if the set is empty). Modified: head/sys/sys/bitset.h ============================================================================== --- head/sys/sys/bitset.h Wed Aug 26 02:05:58 2020 (r364795) +++ head/sys/sys/bitset.h Wed Aug 26 02:07:46 2020 (r364796) @@ -207,20 +207,31 @@ (f)->__bits[__i]); \ } while (0) -#define BIT_FFS(_s, p) __extension__ ({ \ +/* + * Note that `start` and the returned value from BIT_FFS_AT are + * 1-based bit indices. + */ +#define BIT_FFS_AT(_s, p, start) __extension__ ({ \ __size_t __i; \ + long __mask; \ int __bit; \ \ + __mask = ~0UL << ((start) % _BITSET_BITS); \ __bit = 0; \ - for (__i = 0; __i < __bitset_words((_s)); __i++) { \ - if ((p)->__bits[__i] != 0) { \ - __bit = ffsl((p)->__bits[__i]); \ + for (__i = __bitset_word((_s), (start)); \ + __i < __bitset_words((_s)); \ + __i++) { \ + if (((p)->__bits[__i] & __mask) != 0) { \ + __bit = ffsl((p)->__bits[__i] & __mask); \ __bit += __i * _BITSET_BITS; \ break; \ } \ + __mask = ~0UL; \ } \ __bit; \ }) + +#define BIT_FFS(_s, p) BIT_FFS_AT((_s), (p), 0) #define BIT_FLS(_s, p) __extension__ ({ \ __size_t __i; \ _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
