1/*
  2 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
  3 * All Rights Reserved.
  4 *
  5 * This program is free software; you can redistribute it and/or
  6 * modify it under the terms of the GNU General Public License as
  7 * published by the Free Software Foundation.
  8 *
  9 * This program is distributed in the hope that it would be useful,
 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12 * GNU General Public License for more details.
 13 *
 14 * You should have received a copy of the GNU General Public License
 15 * along with this program; if not, write the Free Software Foundation,
 16 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 17 */
 18#include "xfs.h"
 19#include "xfs_bit.h"
 20#include "xfs_log.h"
 21#include "xfs_trans.h"
 22#include "xfs_buf_item.h"
 23
 24/*
 25 * XFS bit manipulation routines, used in non-realtime code.
 26 */
 27
 28/*
 29 * Return whether bitmap is empty.
 30 * Size is number of words in the bitmap, which is padded to word boundary
 31 * Returns 1 for empty, 0 for non-empty.
 32 */
 33int
 34xfs_bitmap_empty(uint *map, uint size)
 35{
 36	uint i;
 37	uint ret = 0;
 38
 39	for (i = 0; i < size; i++) {
 40		ret |= map[i];
 41	}
 42
 43	return (ret == 0);
 44}
 45
 46/*
 47 * Count the number of contiguous bits set in the bitmap starting with bit
 48 * start_bit.  Size is the size of the bitmap in words.
 49 */
 50int
 51xfs_contig_bits(uint *map, uint	size, uint start_bit)
 52{
 53	uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
 54	uint result = 0;
 55	uint tmp;
 56
 57	size <<= BIT_TO_WORD_SHIFT;
 58
 59	ASSERT(start_bit < size);
 60	size -= start_bit & ~(NBWORD - 1);
 61	start_bit &= (NBWORD - 1);
 62	if (start_bit) {
 63		tmp = *p++;
 64		/* set to one first offset bits prior to start */
 65		tmp |= (~0U >> (NBWORD-start_bit));
 66		if (tmp != ~0U)
 67			goto found;
 68		result += NBWORD;
 69		size -= NBWORD;
 70	}
 71	while (size) {
 72		if ((tmp = *p++) != ~0U)
 73			goto found;
 74		result += NBWORD;
 75		size -= NBWORD;
 76	}
 77	return result - start_bit;
 78found:
 79	return result + ffz(tmp) - start_bit;
 80}
 81
 82/*
 83 * This takes the bit number to start looking from and
 84 * returns the next set bit from there.  It returns -1
 85 * if there are no more bits set or the start bit is
 86 * beyond the end of the bitmap.
 87 *
 88 * Size is the number of words, not bytes, in the bitmap.
 89 */
 90int xfs_next_bit(uint *map, uint size, uint start_bit)
 91{
 92	uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
 93	uint result = start_bit & ~(NBWORD - 1);
 94	uint tmp;
 95
 96	size <<= BIT_TO_WORD_SHIFT;
 97
 98	if (start_bit >= size)
 99		return -1;
100	size -= result;
101	start_bit &= (NBWORD - 1);
102	if (start_bit) {
103		tmp = *p++;
104		/* set to zero first offset bits prior to start */
105		tmp &= (~0U << start_bit);
106		if (tmp != 0U)
107			goto found;
108		result += NBWORD;
109		size -= NBWORD;
110	}
111	while (size) {
112		if ((tmp = *p++) != 0U)
113			goto found;
114		result += NBWORD;
115		size -= NBWORD;
116	}
117	return -1;
118found:
119	return result + ffs(tmp) - 1;
120}