/* * 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; }