mirror of https://gitee.com/openkylin/linux.git
143 lines
3.3 KiB
C
143 lines
3.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* bit search implementation
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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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#include <linux/bitops.h>
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#include <linux/bitmap.h>
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#include <linux/export.h>
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#include <linux/math.h>
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#include <linux/minmax.h>
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#include <linux/swab.h>
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#if !defined(find_next_bit) || !defined(find_next_zero_bit) || \
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!defined(find_next_bit_le) || !defined(find_next_zero_bit_le) || \
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!defined(find_next_and_bit)
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/*
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* This is a common helper function for find_next_bit, find_next_zero_bit, and
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* find_next_and_bit. The differences are:
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* - The "invert" argument, which is XORed with each fetched word before
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* searching it for one bits.
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* - The optional "addr2", which is anded with "addr1" if present.
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*/
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unsigned long _find_next_bit(const unsigned long *addr1,
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const unsigned long *addr2, unsigned long nbits,
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unsigned long start, unsigned long invert, unsigned long le)
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{
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unsigned long tmp, mask;
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if (unlikely(start >= nbits))
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return nbits;
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tmp = addr1[start / BITS_PER_LONG];
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if (addr2)
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tmp &= addr2[start / BITS_PER_LONG];
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tmp ^= invert;
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/* Handle 1st word. */
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mask = BITMAP_FIRST_WORD_MASK(start);
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if (le)
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mask = swab(mask);
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tmp &= mask;
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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 = addr1[start / BITS_PER_LONG];
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if (addr2)
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tmp &= addr2[start / BITS_PER_LONG];
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tmp ^= invert;
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}
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if (le)
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tmp = swab(tmp);
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return min(start + __ffs(tmp), nbits);
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}
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EXPORT_SYMBOL(_find_next_bit);
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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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EXPORT_SYMBOL(_find_first_bit);
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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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EXPORT_SYMBOL(_find_first_zero_bit);
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#endif
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#ifndef find_last_bit
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unsigned long _find_last_bit(const unsigned long *addr, unsigned long size)
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{
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if (size) {
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unsigned long val = BITMAP_LAST_WORD_MASK(size);
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unsigned long idx = (size-1) / BITS_PER_LONG;
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do {
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val &= addr[idx];
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if (val)
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return idx * BITS_PER_LONG + __fls(val);
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val = ~0ul;
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} while (idx--);
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}
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return size;
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}
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EXPORT_SYMBOL(_find_last_bit);
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#endif
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unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
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unsigned long size, unsigned long offset)
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{
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offset = find_next_bit(addr, size, offset);
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if (offset == size)
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return size;
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offset = round_down(offset, 8);
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*clump = bitmap_get_value8(addr, offset);
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return offset;
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}
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EXPORT_SYMBOL(find_next_clump8);
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