diff options
Diffstat (limited to 'bitops.c')
-rw-r--r-- | bitops.c | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/bitops.c b/bitops.c new file mode 100644 index 0000000..d9de71f --- /dev/null +++ b/bitops.c @@ -0,0 +1,142 @@ +/* + * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * Copyright (C) 2008 IBM Corporation + * Written by Rusty Russell <rusty@rustcorp.com.au> + * (Inspired by David Howell's find_next_bit implementation) + * + * 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 "bitops.h" + +#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG) + +/* + * Find the next set bit in a memory region. + */ +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 + bitops_ffsl(tmp); +} + +/* + * 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); +} + +unsigned long find_last_bit(const unsigned long *addr, unsigned long size) +{ + unsigned long words; + unsigned long tmp; + + /* Start at final word. */ + words = size / BITS_PER_LONG; + + /* Partial final word? */ + if (size & (BITS_PER_LONG-1)) { + tmp = (addr[words] & (~0UL >> (BITS_PER_LONG + - (size & (BITS_PER_LONG-1))))); + if (tmp) { + goto found; + } + } + + while (words) { + tmp = addr[--words]; + if (tmp) { + found: + return words * BITS_PER_LONG + bitops_flsl(tmp); + } + } + + /* Not found */ + return size; +} |