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_log_format.h"
 20#include "xfs_bit.h"
 21
 22/*
 23 * XFS bit manipulation routines, used in non-realtime code.
 24 */
 25
 26/*
 27 * Return whether bitmap is empty.
 28 * Size is number of words in the bitmap, which is padded to word boundary
 29 * Returns 1 for empty, 0 for non-empty.
 30 */
 31int
 32xfs_bitmap_empty(uint *map, uint size)
 33{
 34	uint i;
 35	uint ret = 0;
 36
 37	for (i = 0; i < size; i++) {
 38		ret |= map[i];
 39	}
 40
 41	return (ret == 0);
 42}
 43
 44/*
 45 * Count the number of contiguous bits set in the bitmap starting with bit
 46 * start_bit.  Size is the size of the bitmap in words.
 47 */
 48int
 49xfs_contig_bits(uint *map, uint	size, uint start_bit)
 50{
 51	uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
 52	uint result = 0;
 53	uint tmp;
 54
 55	size <<= BIT_TO_WORD_SHIFT;
 56
 57	ASSERT(start_bit < size);
 58	size -= start_bit & ~(NBWORD - 1);
 59	start_bit &= (NBWORD - 1);
 60	if (start_bit) {
 61		tmp = *p++;
 62		/* set to one first offset bits prior to start */
 63		tmp |= (~0U >> (NBWORD-start_bit));
 64		if (tmp != ~0U)
 65			goto found;
 66		result += NBWORD;
 67		size -= NBWORD;
 68	}
 69	while (size) {
 70		if ((tmp = *p++) != ~0U)
 71			goto found;
 72		result += NBWORD;
 73		size -= NBWORD;
 74	}
 75	return result - start_bit;
 76found:
 77	return result + ffz(tmp) - start_bit;
 78}
 79
 80/*
 81 * This takes the bit number to start looking from and
 82 * returns the next set bit from there.  It returns -1
 83 * if there are no more bits set or the start bit is
 84 * beyond the end of the bitmap.
 85 *
 86 * Size is the number of words, not bytes, in the bitmap.
 87 */
 88int xfs_next_bit(uint *map, uint size, uint start_bit)
 89{
 90	uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
 91	uint result = start_bit & ~(NBWORD - 1);
 92	uint tmp;
 93
 94	size <<= BIT_TO_WORD_SHIFT;
 95
 96	if (start_bit >= size)
 97		return -1;
 98	size -= result;
 99	start_bit &= (NBWORD - 1);
100	if (start_bit) {
101		tmp = *p++;
102		/* set to zero first offset bits prior to start */
103		tmp &= (~0U << start_bit);
104		if (tmp != 0U)
105			goto found;
106		result += NBWORD;
107		size -= NBWORD;
108	}
109	while (size) {
110		if ((tmp = *p++) != 0U)
111			goto found;
112		result += NBWORD;
113		size -= NBWORD;
114	}
115	return -1;
116found:
117	return result + ffs(tmp) - 1;
118}