| /* |
| * 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 "qemu/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; |
| } |