projects / linux-2.6-block.git / blame
| Commit | Line | Data |
|---|---|---|
| 1366c37e MW |
1 | /* find_next_bit.c: fallback find next bit implementation |
| 2 | * | |
| 3 | * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved. | |
| 4 | * Written by David Howells (dhowells@redhat.com) | |
| 5 | * | |
| 6 | * This program is free software; you can redistribute it and/or | |
| 7 | * modify it under the terms of the GNU General Public License | |
| 8 | * as published by the Free Software Foundation; either version | |
| 9 | * 2 of the License, or (at your option) any later version. | |
| 10 | */ | |
| 11 | ||
| 12 | #include <linux/types.h> | |
| 13 | #include <linux/bitops.h> | |
| 14 | ||
| 15 | #define BITOP_WORD(nr) ((nr) / BITS_PER_LONG) | |
| 16 | ||
| 17 | /* | |
| 18 | * Find the next set bit in a memory region. | |
| 19 | */ | |
| 20 | unsigned long find_next_bit(const unsigned long *addr, unsigned long size, | |
| 21 | unsigned long offset) | |
| 22 | { | |
| 23 | const unsigned long *p = addr + BITOP_WORD(offset); | |
| 24 | unsigned long result = offset & ~(BITS_PER_LONG-1); | |
| 25 | unsigned long tmp; | |
| 26 | ||
| 27 | if (offset >= size) | |
| 28 | return size; | |
| 29 | size -= result; | |
| 30 | offset %= BITS_PER_LONG; | |
| 31 | if (offset) { | |
| 32 | tmp = *(p++); | |
| 33 | tmp &= (~0UL << offset); | |
| 34 | if (size < BITS_PER_LONG) | |
| 35 | goto found_first; | |
| 36 | if (tmp) | |
| 37 | goto found_middle; | |
| 38 | size -= BITS_PER_LONG; | |
| 39 | result += BITS_PER_LONG; | |
| 40 | } | |
| 41 | while (size & ~(BITS_PER_LONG-1)) { | |
| 42 | if ((tmp = *(p++))) | |
| 43 | goto found_middle; | |
| 44 | result += BITS_PER_LONG; | |
| 45 | size -= BITS_PER_LONG; | |
| 46 | } | |
| 47 | if (!size) | |
| 48 | return result; | |
| 49 | tmp = *p; | |
| 50 | ||
| 51 | found_first: | |
| 52 | tmp &= (~0UL >> (BITS_PER_LONG - size)); | |
| 53 | if (tmp == 0UL) /* Are any bits set? */ | |
| 54 | return result + size; /* Nope. */ | |
| 55 | found_middle: | |
| 56 | return result + __ffs(tmp); | |
| 57 | } |