119 lines
2.8 KiB
C
119 lines
2.8 KiB
C
/*
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* Copyright (c) 2000-2005 Silicon Graphics, Inc.
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* All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it would be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "xfs.h"
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#include "xfs_log_format.h"
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#include "xfs_bit.h"
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/*
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* XFS bit manipulation routines, used in non-realtime code.
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*/
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/*
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* Return whether bitmap is empty.
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* Size is number of words in the bitmap, which is padded to word boundary
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* Returns 1 for empty, 0 for non-empty.
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*/
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int
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xfs_bitmap_empty(uint *map, uint size)
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{
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uint i;
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for (i = 0; i < size; i++) {
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if (map[i] != 0)
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return 0;
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}
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return 1;
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}
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/*
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* Count the number of contiguous bits set in the bitmap starting with bit
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* start_bit. Size is the size of the bitmap in words.
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*/
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int
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xfs_contig_bits(uint *map, uint size, uint start_bit)
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{
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uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
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uint result = 0;
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uint tmp;
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size <<= BIT_TO_WORD_SHIFT;
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ASSERT(start_bit < size);
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size -= start_bit & ~(NBWORD - 1);
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start_bit &= (NBWORD - 1);
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if (start_bit) {
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tmp = *p++;
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/* set to one first offset bits prior to start */
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tmp |= (~0U >> (NBWORD-start_bit));
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if (tmp != ~0U)
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goto found;
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result += NBWORD;
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size -= NBWORD;
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}
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while (size) {
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if ((tmp = *p++) != ~0U)
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goto found;
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result += NBWORD;
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size -= NBWORD;
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}
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return result - start_bit;
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found:
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return result + ffz(tmp) - start_bit;
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}
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/*
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* This takes the bit number to start looking from and
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* returns the next set bit from there. It returns -1
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* if there are no more bits set or the start bit is
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* beyond the end of the bitmap.
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*
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* Size is the number of words, not bytes, in the bitmap.
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*/
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int xfs_next_bit(uint *map, uint size, uint start_bit)
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{
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uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
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uint result = start_bit & ~(NBWORD - 1);
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uint tmp;
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size <<= BIT_TO_WORD_SHIFT;
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if (start_bit >= size)
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return -1;
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size -= result;
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start_bit &= (NBWORD - 1);
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if (start_bit) {
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tmp = *p++;
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/* set to zero first offset bits prior to start */
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tmp &= (~0U << start_bit);
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if (tmp != 0U)
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goto found;
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result += NBWORD;
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size -= NBWORD;
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}
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while (size) {
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if ((tmp = *p++) != 0U)
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goto found;
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result += NBWORD;
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size -= NBWORD;
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}
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return -1;
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found:
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return result + ffs(tmp) - 1;
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}
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