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/*
 22 * Common helper for find_bit() function family
 23 * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
 24 * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
 25 * @size: The bitmap size in bits
 26 */
 27#define FIND_FIRST_BIT(FETCH, MUNGE, size)					\
 28({										\
 29	unsigned long idx, val, sz = (size);					\
 30										\
 31	for (idx = 0; idx * BITS_PER_LONG < sz; idx++) {			\
 32		val = (FETCH);							\
 33		if (val) {							\
 34			sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(val)), sz);	\
 35			break;							\
 36		}								\
 37	}									\
 38										\
 39	sz;									\
 40})
 41
 42/*
 43 * Common helper for find_next_bit() function family
 44 * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
 45 * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
 46 * @size: The bitmap size in bits
 47 * @start: The bitnumber to start searching at
 48 */
 49#define FIND_NEXT_BIT(FETCH, MUNGE, size, start)				\
 50({										\
 51	unsigned long mask, idx, tmp, sz = (size), __start = (start);		\
 52										\
 53	if (unlikely(__start >= sz))						\
 54		goto out;							\
 55										\
 56	mask = MUNGE(BITMAP_FIRST_WORD_MASK(__start));				\
 57	idx = __start / BITS_PER_LONG;						\
 58										\
 59	for (tmp = (FETCH) & mask; !tmp; tmp = (FETCH)) {			\
 60		if ((idx + 1) * BITS_PER_LONG >= sz)				\
 61			goto out;						\
 62		idx++;								\
 63	}									\
 64										\
 65	sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(tmp)), sz);			\
 66out:										\
 67	sz;									\
 68})
 69
 70#ifndef find_first_bit
 71/*
 72 * Find the first set bit in a memory region.
 73 */
 74unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
 75{
 76	return FIND_FIRST_BIT(addr[idx], /* nop */, size);
 77}
 78#endif
 79
 80#ifndef find_first_and_bit
 81/*
 82 * Find the first set bit in two memory regions.
 83 */
 84unsigned long _find_first_and_bit(const unsigned long *addr1,
 85				  const unsigned long *addr2,
 86				  unsigned long size)
 87{
 88	return FIND_FIRST_BIT(addr1[idx] & addr2[idx], /* nop */, size);
 89}
 90#endif
 91
 92#ifndef find_first_zero_bit
 93/*
 94 * Find the first cleared bit in a memory region.
 95 */
 96unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
 97{
 98	return FIND_FIRST_BIT(~addr[idx], /* nop */, size);
 99}
100#endif
101
102#ifndef find_next_bit
103unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, unsigned long start)
104{
105	return FIND_NEXT_BIT(addr[idx], /* nop */, nbits, start);
106}
107#endif
108
109#ifndef find_next_and_bit
110unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2,
111					unsigned long nbits, unsigned long start)
112{
113	return FIND_NEXT_BIT(addr1[idx] & addr2[idx], /* nop */, nbits, start);
114}
115#endif
116
117#ifndef find_next_zero_bit
118unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
119					 unsigned long start)
120{
121	return FIND_NEXT_BIT(~addr[idx], /* nop */, nbits, start);
122}
123#endif