| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame] | 1 | // SPDX-License-Identifier: GPL-2.0 |
| 2 | /* |
| 3 | * Copyright (c) 2000-2005 Silicon Graphics, Inc. |
| 4 | * All Rights Reserved. |
| 5 | */ |
| 6 | #include "xfs.h" |
| 7 | #include "xfs_log_format.h" |
| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame] | 8 | |
| 9 | /* |
| 10 | * XFS bit manipulation routines, used in non-realtime code. |
| 11 | */ |
| 12 | |
| 13 | /* |
| 14 | * Return whether bitmap is empty. |
| 15 | * Size is number of words in the bitmap, which is padded to word boundary |
| 16 | * Returns 1 for empty, 0 for non-empty. |
| 17 | */ |
| 18 | int |
| 19 | xfs_bitmap_empty(uint *map, uint size) |
| 20 | { |
| 21 | uint i; |
| 22 | |
| 23 | for (i = 0; i < size; i++) { |
| 24 | if (map[i] != 0) |
| 25 | return 0; |
| 26 | } |
| 27 | |
| 28 | return 1; |
| 29 | } |
| 30 | |
| 31 | /* |
| 32 | * Count the number of contiguous bits set in the bitmap starting with bit |
| 33 | * start_bit. Size is the size of the bitmap in words. |
| 34 | */ |
| 35 | int |
| 36 | xfs_contig_bits(uint *map, uint size, uint start_bit) |
| 37 | { |
| 38 | uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT); |
| 39 | uint result = 0; |
| 40 | uint tmp; |
| 41 | |
| 42 | size <<= BIT_TO_WORD_SHIFT; |
| 43 | |
| 44 | ASSERT(start_bit < size); |
| 45 | size -= start_bit & ~(NBWORD - 1); |
| 46 | start_bit &= (NBWORD - 1); |
| 47 | if (start_bit) { |
| 48 | tmp = *p++; |
| 49 | /* set to one first offset bits prior to start */ |
| 50 | tmp |= (~0U >> (NBWORD-start_bit)); |
| 51 | if (tmp != ~0U) |
| 52 | goto found; |
| 53 | result += NBWORD; |
| 54 | size -= NBWORD; |
| 55 | } |
| 56 | while (size) { |
| 57 | if ((tmp = *p++) != ~0U) |
| 58 | goto found; |
| 59 | result += NBWORD; |
| 60 | size -= NBWORD; |
| 61 | } |
| 62 | return result - start_bit; |
| 63 | found: |
| 64 | return result + ffz(tmp) - start_bit; |
| 65 | } |
| 66 | |
| 67 | /* |
| 68 | * This takes the bit number to start looking from and |
| 69 | * returns the next set bit from there. It returns -1 |
| 70 | * if there are no more bits set or the start bit is |
| 71 | * beyond the end of the bitmap. |
| 72 | * |
| 73 | * Size is the number of words, not bytes, in the bitmap. |
| 74 | */ |
| 75 | int xfs_next_bit(uint *map, uint size, uint start_bit) |
| 76 | { |
| 77 | uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT); |
| 78 | uint result = start_bit & ~(NBWORD - 1); |
| 79 | uint tmp; |
| 80 | |
| 81 | size <<= BIT_TO_WORD_SHIFT; |
| 82 | |
| 83 | if (start_bit >= size) |
| 84 | return -1; |
| 85 | size -= result; |
| 86 | start_bit &= (NBWORD - 1); |
| 87 | if (start_bit) { |
| 88 | tmp = *p++; |
| 89 | /* set to zero first offset bits prior to start */ |
| 90 | tmp &= (~0U << start_bit); |
| 91 | if (tmp != 0U) |
| 92 | goto found; |
| 93 | result += NBWORD; |
| 94 | size -= NBWORD; |
| 95 | } |
| 96 | while (size) { |
| 97 | if ((tmp = *p++) != 0U) |
| 98 | goto found; |
| 99 | result += NBWORD; |
| 100 | size -= NBWORD; |
| 101 | } |
| 102 | return -1; |
| 103 | found: |
| 104 | return result + ffs(tmp) - 1; |
| 105 | } |