1// SPDX-License-Identifier: GPL-2.0-or-later
  2/* bit search implementation
  3 *
  4 * Copied from lib/find_bit.c to tools/lib/find_bit.c
  5 *
  6 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
  7 * Written by David Howells (dhowells@redhat.com)
  8 *
  9 * Copyright (C) 2008 IBM Corporation
 10 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
 11 * (Inspired by David Howell's find_next_bit implementation)
 12 *
 13 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
 14 * size and improve performance, 2015.
 15 */
 16
 17#include <linux/bitops.h>
 18#include <linux/bitmap.h>
 19#include <linux/kernel.h>
 20
 21#if !defined(find_next_bit) || !defined(find_next_zero_bit) || \
 22		!defined(find_next_and_bit)
 23
 24/*
 25 * This is a common helper function for find_next_bit, find_next_zero_bit, and
 26 * find_next_and_bit. The differences are:
 27 *  - The "invert" argument, which is XORed with each fetched word before
 28 *    searching it for one bits.
 29 *  - The optional "addr2", which is anded with "addr1" if present.
 30 */
 31unsigned long _find_next_bit(const unsigned long *addr1,
 32		const unsigned long *addr2, unsigned long nbits,
 33		unsigned long start, unsigned long invert, unsigned long le)
 34{
 35	unsigned long tmp, mask;
 36	(void) le;
 37
 38	if (unlikely(start >= nbits))
 39		return nbits;
 40
 41	tmp = addr1[start / BITS_PER_LONG];
 42	if (addr2)
 43		tmp &= addr2[start / BITS_PER_LONG];
 44	tmp ^= invert;
 45
 46	/* Handle 1st word. */
 47	mask = BITMAP_FIRST_WORD_MASK(start);
 48
 49	/*
 50	 * Due to the lack of swab() in tools, and the fact that it doesn't
 51	 * need little-endian support, just comment it out
 52	 */
 53#if (0)
 54	if (le)
 55		mask = swab(mask);
 56#endif
 57
 58	tmp &= mask;
 59
 60	start = round_down(start, BITS_PER_LONG);
 61
 62	while (!tmp) {
 63		start += BITS_PER_LONG;
 64		if (start >= nbits)
 65			return nbits;
 66
 67		tmp = addr1[start / BITS_PER_LONG];
 68		if (addr2)
 69			tmp &= addr2[start / BITS_PER_LONG];
 70		tmp ^= invert;
 71	}
 72
 73#if (0)
 74	if (le)
 75		tmp = swab(tmp);
 76#endif
 77
 78	return min(start + __ffs(tmp), nbits);
 79}
 80#endif
 81
 82#ifndef find_first_bit
 83/*
 84 * Find the first set bit in a memory region.
 85 */
 86unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
 87{
 88	unsigned long idx;
 89
 90	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
 91		if (addr[idx])
 92			return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
 93	}
 94
 95	return size;
 96}
 97#endif
 98
 99#ifndef find_first_zero_bit
100/*
101 * Find the first cleared bit in a memory region.
102 */
103unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
104{
105	unsigned long idx;
106
107	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
108		if (addr[idx] != ~0UL)
109			return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
110	}
111
112	return size;
113}
114#endif