에프에이리눅스 / 1611_0007_prime_oven

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kernel/linux-imx6_3.14.28/fs/xfs/xfs_bit.c 2.78 KB
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6b13f685e   김민수   BSP 최초 추가 
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  /*
   * Copyright (c) 2000-2005 Silicon Graphics, Inc.
   * All Rights Reserved.
   *
   * 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.
   *
   * This program is distributed in the hope that it would be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write the Free Software Foundation,
   * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
   */
  #include "xfs.h"
  #include "xfs_log_format.h"
  #include "xfs_bit.h"
  
  /*
   * XFS bit manipulation routines, used in non-realtime code.
   */
  
  /*
   * Return whether bitmap is empty.
   * Size is number of words in the bitmap, which is padded to word boundary
   * Returns 1 for empty, 0 for non-empty.
   */
  int
  xfs_bitmap_empty(uint *map, uint size)
  {
  	uint i;
  	uint ret = 0;
  
  	for (i = 0; i < size; i++) {
  		ret |= map[i];
  	}
  
  	return (ret == 0);
  }
  
  /*
   * Count the number of contiguous bits set in the bitmap starting with bit
   * start_bit.  Size is the size of the bitmap in words.
   */
  int
  xfs_contig_bits(uint *map, uint	size, uint start_bit)
  {
  	uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
  	uint result = 0;
  	uint tmp;
  
  	size <<= BIT_TO_WORD_SHIFT;
  
  	ASSERT(start_bit < size);
  	size -= start_bit & ~(NBWORD - 1);
  	start_bit &= (NBWORD - 1);
  	if (start_bit) {
  		tmp = *p++;
  		/* set to one first offset bits prior to start */
  		tmp |= (~0U >> (NBWORD-start_bit));
  		if (tmp != ~0U)
  			goto found;
  		result += NBWORD;
  		size -= NBWORD;
  	}
  	while (size) {
  		if ((tmp = *p++) != ~0U)
  			goto found;
  		result += NBWORD;
  		size -= NBWORD;
  	}
  	return result - start_bit;
  found:
  	return result + ffz(tmp) - start_bit;
  }
  
  /*
   * This takes the bit number to start looking from and
   * returns the next set bit from there.  It returns -1
   * if there are no more bits set or the start bit is
   * beyond the end of the bitmap.
   *
   * Size is the number of words, not bytes, in the bitmap.
   */
  int xfs_next_bit(uint *map, uint size, uint start_bit)
  {
  	uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
  	uint result = start_bit & ~(NBWORD - 1);
  	uint tmp;
  
  	size <<= BIT_TO_WORD_SHIFT;
  
  	if (start_bit >= size)
  		return -1;
  	size -= result;
  	start_bit &= (NBWORD - 1);
  	if (start_bit) {
  		tmp = *p++;
  		/* set to zero first offset bits prior to start */
  		tmp &= (~0U << start_bit);
  		if (tmp != 0U)
  			goto found;
  		result += NBWORD;
  		size -= NBWORD;
  	}
  	while (size) {
  		if ((tmp = *p++) != 0U)
  			goto found;
  		result += NBWORD;
  		size -= NBWORD;
  	}
  	return -1;
  found:
  	return result + ffs(tmp) - 1;
  }