diff options
| -rw-r--r-- | include/linux/bitops.h | 19 | ||||
| -rw-r--r-- | include/linux/find.h | 86 | ||||
| -rw-r--r-- | lib/find_bit.c | 44 |
3 files changed, 149 insertions, 0 deletions
diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 3b89c64bcfd8..d7dd83fafeba 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -248,6 +248,25 @@ static inline unsigned long __ffs64(u64 word) } /** + * fns - find N'th set bit in a word + * @word: The word to search + * @n: Bit to find + */ +static inline unsigned long fns(unsigned long word, unsigned int n) +{ + unsigned int bit; + + while (word) { + bit = __ffs(word); + if (n-- == 0) + return bit; + __clear_bit(bit, &word); + } + + return BITS_PER_LONG; +} + +/** * assign_bit - Assign value to a bit in memory * @nr: the bit to set * @addr: the address to start counting from diff --git a/include/linux/find.h b/include/linux/find.h index dead6f53a97b..b100944daba0 100644 --- a/include/linux/find.h +++ b/include/linux/find.h @@ -15,6 +15,11 @@ unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits, unsigned long start); extern unsigned long _find_first_bit(const unsigned long *addr, unsigned long size); +unsigned long __find_nth_bit(const unsigned long *addr, unsigned long size, unsigned long n); +unsigned long __find_nth_and_bit(const unsigned long *addr1, const unsigned long *addr2, + unsigned long size, unsigned long n); +unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2, + unsigned long size, unsigned long n); extern unsigned long _find_first_and_bit(const unsigned long *addr1, const unsigned long *addr2, unsigned long size); extern unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size); @@ -136,6 +141,87 @@ unsigned long find_first_bit(const unsigned long *addr, unsigned long size) } #endif +/** + * find_nth_bit - find N'th set bit in a memory region + * @addr: The address to start the search at + * @size: The maximum number of bits to search + * @n: The number of set bit, which position is needed, counting from 0 + * + * The following is semantically equivalent: + * idx = find_nth_bit(addr, size, 0); + * idx = find_first_bit(addr, size); + * + * Returns the bit number of the N'th set bit. + * If no such, returns @size. + */ +static inline +unsigned long find_nth_bit(const unsigned long *addr, unsigned long size, unsigned long n) +{ + if (n >= size) + return size; + + if (small_const_nbits(size)) { + unsigned long val = *addr & GENMASK(size - 1, 0); + + return val ? fns(val, n) : size; + } + + return __find_nth_bit(addr, size, n); +} + +/** + * find_nth_and_bit - find N'th set bit in 2 memory regions + * @addr1: The 1st address to start the search at + * @addr2: The 2nd address to start the search at + * @size: The maximum number of bits to search + * @n: The number of set bit, which position is needed, counting from 0 + * + * Returns the bit number of the N'th set bit. + * If no such, returns @size. + */ +static inline +unsigned long find_nth_and_bit(const unsigned long *addr1, const unsigned long *addr2, + unsigned long size, unsigned long n) +{ + if (n >= size) + return size; + + if (small_const_nbits(size)) { + unsigned long val = *addr1 & *addr2 & GENMASK(size - 1, 0); + + return val ? fns(val, n) : size; + } + + return __find_nth_and_bit(addr1, addr2, size, n); +} + +/** + * find_nth_andnot_bit - find N'th set bit in 2 memory regions, + * flipping bits in 2nd region + * @addr1: The 1st address to start the search at + * @addr2: The 2nd address to start the search at + * @size: The maximum number of bits to search + * @n: The number of set bit, which position is needed, counting from 0 + * + * Returns the bit number of the N'th set bit. + * If no such, returns @size. + */ +static inline +unsigned long find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2, + unsigned long size, unsigned long n) +{ + if (n >= size) + return size; + + if (small_const_nbits(size)) { + unsigned long val = *addr1 & (~*addr2) & GENMASK(size - 1, 0); + + return val ? fns(val, n) : size; + } + + return __find_nth_andnot_bit(addr1, addr2, size, n); +} + #ifndef find_first_and_bit /** * find_first_and_bit - find the first set bit in both memory regions diff --git a/lib/find_bit.c b/lib/find_bit.c index d00ee23ab657..25609974cbe4 100644 --- a/lib/find_bit.c +++ b/lib/find_bit.c @@ -68,6 +68,30 @@ out: \ sz; \ }) +#define FIND_NTH_BIT(FETCH, size, num) \ +({ \ + unsigned long sz = (size), nr = (num), idx, w, tmp; \ + \ + for (idx = 0; (idx + 1) * BITS_PER_LONG <= sz; idx++) { \ + if (idx * BITS_PER_LONG + nr >= sz) \ + goto out; \ + \ + tmp = (FETCH); \ + w = hweight_long(tmp); \ + if (w > nr) \ + goto found; \ + \ + nr -= w; \ + } \ + \ + if (sz % BITS_PER_LONG) \ + tmp = (FETCH) & BITMAP_LAST_WORD_MASK(sz); \ +found: \ + sz = min(idx * BITS_PER_LONG + fns(tmp, nr), sz); \ +out: \ + sz; \ +}) + #ifndef find_first_bit /* * Find the first set bit in a memory region. @@ -111,6 +135,26 @@ unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, uns EXPORT_SYMBOL(_find_next_bit); #endif +unsigned long __find_nth_bit(const unsigned long *addr, unsigned long size, unsigned long n) +{ + return FIND_NTH_BIT(addr[idx], size, n); +} +EXPORT_SYMBOL(__find_nth_bit); + +unsigned long __find_nth_and_bit(const unsigned long *addr1, const unsigned long *addr2, + unsigned long size, unsigned long n) +{ + return FIND_NTH_BIT(addr1[idx] & addr2[idx], size, n); +} +EXPORT_SYMBOL(__find_nth_and_bit); + +unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2, + unsigned long size, unsigned long n) +{ + return FIND_NTH_BIT(addr1[idx] & ~addr2[idx], size, n); +} +EXPORT_SYMBOL(__find_nth_andnot_bit); + #ifndef find_next_and_bit unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2, unsigned long nbits, unsigned long start) |