[linux-2.6-block.git] / tools / lib / find_bit.c

/* 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.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

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

#if !defined(find_next_bit)

/*
 * This is a common helper function for find_next_bit and
 * find_next_zero_bit.  The difference is the "invert" argument, which
 * is XORed with each fetched word before searching it for one bits.
 */
static unsigned long _find_next_bit(const unsigned long *addr,
		unsigned long nbits, unsigned long start, unsigned long invert)
{
	unsigned long tmp;

	if (!nbits || start >= nbits)
		return nbits;

	tmp = addr[start / BITS_PER_LONG] ^ invert;

	/* Handle 1st word. */
	tmp &= BITMAP_FIRST_WORD_MASK(start);
	start = round_down(start, BITS_PER_LONG);

	while (!tmp) {
		start += BITS_PER_LONG;
		if (start >= nbits)
			return nbits;

		tmp = addr[start / BITS_PER_LONG] ^ invert;
	}

	return min(start + __ffs(tmp), nbits);
}
#endif

#ifndef find_next_bit
/*
 * Find the next set bit in a memory region.
 */
unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
			    unsigned long offset)
{
	return _find_next_bit(addr, size, offset, 0UL);
}
#endif

#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)
{
	unsigned long idx;

	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
		if (addr[idx])
			return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
	}

	return size;
}
#endif
Commit	Line	Data
64af4e0d	1	/* bit search implementation
23e1a358	2	*
64af4e0d	3	* Copied from lib/find_bit.c to tools/lib/find_bit.c
23e1a358 ACM	4	*
	5	* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
	6	* Written by David Howells (dhowells@redhat.com)
	7	*
64af4e0d ACM	8	* Copyright (C) 2008 IBM Corporation
	9	* 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
	10	* (Inspired by David Howell's find_next_bit implementation)
	11	*
	12	* Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
	13	* size and improve performance, 2015.
	14	*
23e1a358 ACM	15	* This program is free software; you can redistribute it and/or
	16	* modify it under the terms of the GNU General Public License
	17	* as published by the Free Software Foundation; either version
	18	* 2 of the License, or (at your option) any later version.
	19	*/
	20
	21	#include <linux/bitops.h>
64af4e0d ACM	22	#include <linux/bitmap.h>
64af4e0d ACM	23	#include <linux/kernel.h>
23e1a358	24
64af4e0d	25	#if !defined(find_next_bit)
23e1a358	26
23e1a358	27	/*
64af4e0d ACM	28	* This is a common helper function for find_next_bit and
	29	* find_next_zero_bit. The difference is the "invert" argument, which
	30	* is XORed with each fetched word before searching it for one bits.
23e1a358	31	*/
64af4e0d ACM	32	static unsigned long _find_next_bit(const unsigned long *addr,
64af4e0d ACM	33	unsigned long nbits, unsigned long start, unsigned long invert)
23e1a358	34	{
23e1a358 ACM	35	unsigned long tmp;
23e1a358 ACM	36
64af4e0d ACM	37	if (!nbits \|\| start >= nbits)
	38	return nbits;
	39
	40	tmp = addr[start / BITS_PER_LONG] ^ invert;
	41
	42	/* Handle 1st word. */
	43	tmp &= BITMAP_FIRST_WORD_MASK(start);
	44	start = round_down(start, BITS_PER_LONG);
	45
	46	while (!tmp) {
	47	start += BITS_PER_LONG;
	48	if (start >= nbits)
	49	return nbits;
	50
	51	tmp = addr[start / BITS_PER_LONG] ^ invert;
23e1a358	52	}
23e1a358	53
64af4e0d ACM	54	return min(start + __ffs(tmp), nbits);
	55	}
	56	#endif
	57
	58	#ifndef find_next_bit
	59	/*
	60	* Find the next set bit in a memory region.
	61	*/
	62	unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
	63	unsigned long offset)
	64	{
	65	return _find_next_bit(addr, size, offset, 0UL);
23e1a358 ACM	66	}
	67	#endif
	68
	69	#ifndef find_first_bit
	70	/*
	71	* Find the first set bit in a memory region.
	72	*/
	73	unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
	74	{
64af4e0d	75	unsigned long idx;
23e1a358	76
64af4e0d ACM	77	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
	78	if (addr[idx])
	79	return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
23e1a358	80	}
23e1a358	81
64af4e0d	82	return size;
23e1a358 ACM	83	}
23e1a358 ACM	84	#endif