c7f612cdf0
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>
109 lines
2.6 KiB
C
109 lines
2.6 KiB
C
/* find_next_bit.c: fallback find next bit implementation
|
|
*
|
|
* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
|
|
* Written by David Howells (dhowells@redhat.com)
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License
|
|
* as published by the Free Software Foundation; either version
|
|
* 2 of the License, or (at your option) any later version.
|
|
*/
|
|
|
|
#include <linux/bitops.h>
|
|
#include <linux/module.h>
|
|
#include <asm/types.h>
|
|
|
|
#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
|
|
|
|
/**
|
|
* find_next_bit - find the next set bit in a memory region
|
|
* @addr: The address to base the search on
|
|
* @offset: The bitnumber to start searching at
|
|
* @size: The maximum size to search
|
|
*/
|
|
unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
|
|
unsigned long offset)
|
|
{
|
|
const unsigned long *p = addr + BITOP_WORD(offset);
|
|
unsigned long result = offset & ~(BITS_PER_LONG-1);
|
|
unsigned long tmp;
|
|
|
|
if (offset >= size)
|
|
return size;
|
|
size -= result;
|
|
offset %= BITS_PER_LONG;
|
|
if (offset) {
|
|
tmp = *(p++);
|
|
tmp &= (~0UL << offset);
|
|
if (size < BITS_PER_LONG)
|
|
goto found_first;
|
|
if (tmp)
|
|
goto found_middle;
|
|
size -= BITS_PER_LONG;
|
|
result += BITS_PER_LONG;
|
|
}
|
|
while (size & ~(BITS_PER_LONG-1)) {
|
|
if ((tmp = *(p++)))
|
|
goto found_middle;
|
|
result += BITS_PER_LONG;
|
|
size -= BITS_PER_LONG;
|
|
}
|
|
if (!size)
|
|
return result;
|
|
tmp = *p;
|
|
|
|
found_first:
|
|
tmp &= (~0UL >> (BITS_PER_LONG - size));
|
|
if (tmp == 0UL) /* Are any bits set? */
|
|
return result + size; /* Nope. */
|
|
found_middle:
|
|
return result + __ffs(tmp);
|
|
}
|
|
|
|
EXPORT_SYMBOL(find_next_bit);
|
|
|
|
/*
|
|
* This implementation of find_{first,next}_zero_bit was stolen from
|
|
* Linus' asm-alpha/bitops.h.
|
|
*/
|
|
unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
|
|
unsigned long offset)
|
|
{
|
|
const unsigned long *p = addr + BITOP_WORD(offset);
|
|
unsigned long result = offset & ~(BITS_PER_LONG-1);
|
|
unsigned long tmp;
|
|
|
|
if (offset >= size)
|
|
return size;
|
|
size -= result;
|
|
offset %= BITS_PER_LONG;
|
|
if (offset) {
|
|
tmp = *(p++);
|
|
tmp |= ~0UL >> (BITS_PER_LONG - offset);
|
|
if (size < BITS_PER_LONG)
|
|
goto found_first;
|
|
if (~tmp)
|
|
goto found_middle;
|
|
size -= BITS_PER_LONG;
|
|
result += BITS_PER_LONG;
|
|
}
|
|
while (size & ~(BITS_PER_LONG-1)) {
|
|
if (~(tmp = *(p++)))
|
|
goto found_middle;
|
|
result += BITS_PER_LONG;
|
|
size -= BITS_PER_LONG;
|
|
}
|
|
if (!size)
|
|
return result;
|
|
tmp = *p;
|
|
|
|
found_first:
|
|
tmp |= ~0UL << size;
|
|
if (tmp == ~0UL) /* Are any bits zero? */
|
|
return result + size; /* Nope. */
|
|
found_middle:
|
|
return result + ffz(tmp);
|
|
}
|
|
|
|
EXPORT_SYMBOL(find_next_zero_bit);
|