[linux-2.6-block.git] / lib / find_next_bit.c

/* find_next_bit.c: fallback find next bit implementation
 *
 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * 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/module.h>

int find_next_bit(const unsigned long *addr, int size, int offset)
{
	const unsigned long *base;
	const int NBITS = sizeof(*addr) * 8;
	unsigned long tmp;

	base = addr;
	if (offset) {
		int suboffset;

		addr += offset / NBITS;

		suboffset = offset % NBITS;
		if (suboffset) {
			tmp = *addr;
			tmp >>= suboffset;
			if (tmp)
				goto finish;
		}

		addr++;
	}

	while ((tmp = *addr) == 0)
		addr++;

	offset = (addr - base) * NBITS;

 finish:
	/* count the remaining bits without using __ffs() since that takes a 32-bit arg */
	while (!(tmp & 0xff)) {
		offset += 8;
		tmp >>= 8;
	}

	while (!(tmp & 1)) {
		offset++;
		tmp >>= 1;
	}

	return offset;
}

EXPORT_SYMBOL(find_next_bit);
Commit	Line	Data
1da177e4 LT	1	/* find_next_bit.c: fallback find next bit implementation
	2	*
	3	* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
	4	* Written by David Howells (dhowells@redhat.com)
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public License
	8	* as published by the Free Software Foundation; either version
	9	* 2 of the License, or (at your option) any later version.
	10	*/
	11
	12	#include <linux/bitops.h>
40234401	13	#include <linux/module.h>
1da177e4 LT	14
	15	int find_next_bit(const unsigned long *addr, int size, int offset)
	16	{
	17	const unsigned long *base;
	18	const int NBITS = sizeof(addr) 8;
	19	unsigned long tmp;
	20
	21	base = addr;
	22	if (offset) {
	23	int suboffset;
	24
	25	addr += offset / NBITS;
	26
	27	suboffset = offset % NBITS;
	28	if (suboffset) {
	29	tmp = *addr;
	30	tmp >>= suboffset;
	31	if (tmp)
	32	goto finish;
	33	}
	34
	35	addr++;
	36	}
	37
	38	while ((tmp = *addr) == 0)
	39	addr++;
	40
	41	offset = (addr - base) * NBITS;
	42
	43	finish:
	44	/* count the remaining bits without using __ffs() since that takes a 32-bit arg */
	45	while (!(tmp & 0xff)) {
	46	offset += 8;
	47	tmp >>= 8;
	48	}
	49
	50	while (!(tmp & 1)) {
	51	offset++;
	52	tmp >>= 1;
	53	}
	54
	55	return offset;
	56	}
40234401 DH	57
40234401 DH	58	EXPORT_SYMBOL(find_next_bit);