mirror of https://gitee.com/openkylin/linux.git
110 lines
2.6 KiB
C
110 lines
2.6 KiB
C
/* bit search implementation
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*
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* Copied from lib/find_bit.c to tools/lib/find_bit.c
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*
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* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* Copyright (C) 2008 IBM Corporation
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* 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
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* (Inspired by David Howell's find_next_bit implementation)
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*
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* Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
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* size and improve performance, 2015.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/bitops.h>
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#include <linux/bitmap.h>
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#include <linux/kernel.h>
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#if !defined(find_next_bit)
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/*
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* This is a common helper function for find_next_bit and
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* find_next_zero_bit. The difference is the "invert" argument, which
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* is XORed with each fetched word before searching it for one bits.
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*/
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static unsigned long _find_next_bit(const unsigned long *addr,
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unsigned long nbits, unsigned long start, unsigned long invert)
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{
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unsigned long tmp;
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if (unlikely(start >= nbits))
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return nbits;
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tmp = addr[start / BITS_PER_LONG] ^ invert;
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/* Handle 1st word. */
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tmp &= BITMAP_FIRST_WORD_MASK(start);
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start = round_down(start, BITS_PER_LONG);
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while (!tmp) {
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start += BITS_PER_LONG;
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if (start >= nbits)
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return nbits;
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tmp = addr[start / BITS_PER_LONG] ^ invert;
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}
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return min(start + __ffs(tmp), nbits);
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}
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#endif
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#ifndef find_next_bit
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/*
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* Find the next set bit in a memory region.
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*/
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unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
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unsigned long offset)
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{
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return _find_next_bit(addr, size, offset, 0UL);
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}
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#endif
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#ifndef find_first_bit
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/*
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* Find the first set bit in a memory region.
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*/
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unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
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{
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unsigned long idx;
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for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
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if (addr[idx])
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return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
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}
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return size;
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}
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#endif
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#ifndef find_first_zero_bit
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/*
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* Find the first cleared bit in a memory region.
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*/
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unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
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{
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unsigned long idx;
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for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
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if (addr[idx] != ~0UL)
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return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
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}
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return size;
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}
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#endif
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#ifndef find_next_zero_bit
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unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
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unsigned long offset)
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{
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return _find_next_bit(addr, size, offset, ~0UL);
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}
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#endif
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