// SPDX-License-Identifier: GPL-2.0-or-later
/* bit search implementation
 *
 * Copied from lib/find_bit.c to tools/lib/find_bit.c
 *
 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * Copyright (C) 2008 IBM Corporation
 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
 * (Inspired by David Howell's find_next_bit implementation)
 *
 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
 * size and improve performance, 2015.
 */

#include <linux/bitops.h>
#include <linux/bitmap.h>
#include <linux/kernel.h>

/*
 * Common helper for find_bit() function family
 * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
 * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
 * @size: The bitmap size in bits
 */
#define FIND_FIRST_BIT(FETCH, MUNGE, size)                                      \
({                                                                              \
        unsigned long idx, val, sz = (size);                                    \
                                                                                \
        for (idx = 0; idx * BITS_PER_LONG < sz; idx++) {                        \
                val = (FETCH);                                                  \
                if (val) {                                                      \
                        sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(val)), sz);  \
                        break;                                                  \
                }                                                               \
        }                                                                       \
                                                                                \
        sz;                                                                     \
})

/*
 * Common helper for find_next_bit() function family
 * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
 * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
 * @size: The bitmap size in bits
 * @start: The bitnumber to start searching at
 */
#define FIND_NEXT_BIT(FETCH, MUNGE, size, start)                                \
({                                                                              \
        unsigned long mask, idx, tmp, sz = (size), __start = (start);           \
                                                                                \
        if (unlikely(__start >= sz))                                            \
                goto out;                                                       \
                                                                                \
        mask = MUNGE(BITMAP_FIRST_WORD_MASK(__start));                          \
        idx = __start / BITS_PER_LONG;                                          \
                                                                                \
        for (tmp = (FETCH) & mask; !tmp; tmp = (FETCH)) {                       \
                if ((idx + 1) * BITS_PER_LONG >= sz)                            \
                        goto out;                                               \
                idx++;                                                          \
        }                                                                       \
                                                                                \
        sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(tmp)), sz);                  \
out:                                                                            \
        sz;                                                                     \
})

#ifndef find_first_bit
/*
 * Find the first set bit in a memory region.
 */
unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
{
        return FIND_FIRST_BIT(addr[idx], /* nop */, size);
}
#endif

#ifndef find_first_and_bit
/*
 * Find the first set bit in two memory regions.
 */
unsigned long _find_first_and_bit(const unsigned long *addr1,
                                  const unsigned long *addr2,
                                  unsigned long size)
{
        return FIND_FIRST_BIT(addr1[idx] & addr2[idx], /* nop */, size);
}
#endif

#ifndef find_first_zero_bit
/*
 * Find the first cleared bit in a memory region.
 */
unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
{
        return FIND_FIRST_BIT(~addr[idx], /* nop */, size);
}
#endif

#ifndef find_next_bit
unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, unsigned long start)
{
        return FIND_NEXT_BIT(addr[idx], /* nop */, nbits, start);
}
#endif

#ifndef find_next_and_bit
unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2,
                                        unsigned long nbits, unsigned long start)
{
        return FIND_NEXT_BIT(addr1[idx] & addr2[idx], /* nop */, nbits, start);
}
#endif

#ifndef find_next_zero_bit
unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
                                         unsigned long start)
{
        return FIND_NEXT_BIT(~addr[idx], /* nop */, nbits, start);
}
#endif