forked from luck/tmp_suning_uos_patched
[PATCH] bitops: generic find_{next,first}{,_zero}_bit()
This patch introduces the C-language equivalents of the functions below: unsigned logn find_next_bit(const unsigned long *addr, unsigned long size, unsigned long offset); unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size, unsigned long offset); unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size); unsigned long find_first_bit(const unsigned long *addr, unsigned long size); In include/asm-generic/bitops/find.h This code largely copied from: arch/powerpc/lib/bitops.c Signed-off-by: Akinobu Mita <mita@miraclelinux.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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include/asm-generic/bitops/find.h
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13
include/asm-generic/bitops/find.h
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@ -0,0 +1,13 @@
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#ifndef _ASM_GENERIC_BITOPS_FIND_H_
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#define _ASM_GENERIC_BITOPS_FIND_H_
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extern unsigned long find_next_bit(const unsigned long *addr, unsigned long
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size, unsigned long offset);
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extern unsigned long find_next_zero_bit(const unsigned long *addr, unsigned
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long size, unsigned long offset);
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#define find_first_bit(addr, size) find_next_bit((addr), (size), 0)
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#define find_first_zero_bit(addr, size) find_next_zero_bit((addr), (size), 0)
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#endif /*_ASM_GENERIC_BITOPS_FIND_H_ */
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@ -11,48 +11,98 @@
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#include <linux/bitops.h>
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#include <linux/module.h>
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#include <asm/types.h>
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int find_next_bit(const unsigned long *addr, int size, int offset)
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#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
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/**
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* find_next_bit - find the next set bit in a memory region
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* @addr: The address to base the search on
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* @offset: The bitnumber to start searching at
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* @size: The maximum size to search
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*/
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unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
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unsigned long offset)
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{
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const unsigned long *base;
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const int NBITS = sizeof(*addr) * 8;
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const unsigned long *p = addr + BITOP_WORD(offset);
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unsigned long result = offset & ~(BITS_PER_LONG-1);
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unsigned long tmp;
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base = addr;
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if (offset >= size)
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return size;
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size -= result;
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offset %= BITS_PER_LONG;
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if (offset) {
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int suboffset;
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addr += offset / NBITS;
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suboffset = offset % NBITS;
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if (suboffset) {
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tmp = *addr;
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tmp >>= suboffset;
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if (tmp)
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goto finish;
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}
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addr++;
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tmp = *(p++);
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tmp &= (~0UL << offset);
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if (size < BITS_PER_LONG)
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goto found_first;
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if (tmp)
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goto found_middle;
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size -= BITS_PER_LONG;
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result += BITS_PER_LONG;
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}
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while ((tmp = *addr) == 0)
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addr++;
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offset = (addr - base) * NBITS;
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finish:
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/* count the remaining bits without using __ffs() since that takes a 32-bit arg */
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while (!(tmp & 0xff)) {
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offset += 8;
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tmp >>= 8;
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while (size & ~(BITS_PER_LONG-1)) {
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if ((tmp = *(p++)))
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goto found_middle;
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result += BITS_PER_LONG;
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size -= BITS_PER_LONG;
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}
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if (!size)
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return result;
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tmp = *p;
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while (!(tmp & 1)) {
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offset++;
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tmp >>= 1;
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}
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return offset;
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found_first:
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tmp &= (~0UL >> (BITS_PER_LONG - size));
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if (tmp == 0UL) /* Are any bits set? */
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return result + size; /* Nope. */
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found_middle:
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return result + __ffs(tmp);
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}
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EXPORT_SYMBOL(find_next_bit);
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/*
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* This implementation of find_{first,next}_zero_bit was stolen from
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* Linus' asm-alpha/bitops.h.
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*/
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unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
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unsigned long offset)
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{
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const unsigned long *p = addr + BITOP_WORD(offset);
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unsigned long result = offset & ~(BITS_PER_LONG-1);
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unsigned long tmp;
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if (offset >= size)
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return size;
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size -= result;
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offset %= BITS_PER_LONG;
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if (offset) {
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tmp = *(p++);
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tmp |= ~0UL >> (BITS_PER_LONG - offset);
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if (size < BITS_PER_LONG)
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goto found_first;
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if (~tmp)
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goto found_middle;
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size -= BITS_PER_LONG;
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result += BITS_PER_LONG;
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}
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while (size & ~(BITS_PER_LONG-1)) {
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if (~(tmp = *(p++)))
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goto found_middle;
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result += BITS_PER_LONG;
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size -= BITS_PER_LONG;
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}
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if (!size)
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return result;
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tmp = *p;
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found_first:
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tmp |= ~0UL << size;
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if (tmp == ~0UL) /* Are any bits zero? */
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return result + size; /* Nope. */
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found_middle:
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return result + ffz(tmp);
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}
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EXPORT_SYMBOL(find_next_zero_bit);
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