linux / linux / kernel / git / viro / vfs / e7f2c8c1f0e5b062c23001dac229e570228940e8 / . / fs / xfs / xfs_bit.c

/* | |

* 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; | |

} |