fs/xfs/xfs_bit.c

   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_bit.h"
  20 #include "xfs_log.h"
  21 #include "xfs_trans.h"
  22 #include "xfs_buf_item.h"
  23
  24 /*
  25  * XFS bit manipulation routines, used in non-realtime code.
  26  */
  27
  28 #ifndef HAVE_ARCH_HIGHBIT
  29 /*
  30  * Index of high bit number in byte, -1 for none set, 0..7 otherwise.
  31  */
  32 static const char xfs_highbit[256] = {
  33        -1, 0, 1, 1, 2, 2, 2, 2,                 /* 00 .. 07 */
  34         3, 3, 3, 3, 3, 3, 3, 3,                 /* 08 .. 0f */
  35         4, 4, 4, 4, 4, 4, 4, 4,                 /* 10 .. 17 */
  36         4, 4, 4, 4, 4, 4, 4, 4,                 /* 18 .. 1f */
  37         5, 5, 5, 5, 5, 5, 5, 5,                 /* 20 .. 27 */
  38         5, 5, 5, 5, 5, 5, 5, 5,                 /* 28 .. 2f */
  39         5, 5, 5, 5, 5, 5, 5, 5,                 /* 30 .. 37 */
  40         5, 5, 5, 5, 5, 5, 5, 5,                 /* 38 .. 3f */
  41         6, 6, 6, 6, 6, 6, 6, 6,                 /* 40 .. 47 */
  42         6, 6, 6, 6, 6, 6, 6, 6,                 /* 48 .. 4f */
  43         6, 6, 6, 6, 6, 6, 6, 6,                 /* 50 .. 57 */
  44         6, 6, 6, 6, 6, 6, 6, 6,                 /* 58 .. 5f */
  45         6, 6, 6, 6, 6, 6, 6, 6,                 /* 60 .. 67 */
  46         6, 6, 6, 6, 6, 6, 6, 6,                 /* 68 .. 6f */
  47         6, 6, 6, 6, 6, 6, 6, 6,                 /* 70 .. 77 */
  48         6, 6, 6, 6, 6, 6, 6, 6,                 /* 78 .. 7f */
  49         7, 7, 7, 7, 7, 7, 7, 7,                 /* 80 .. 87 */
  50         7, 7, 7, 7, 7, 7, 7, 7,                 /* 88 .. 8f */
  51         7, 7, 7, 7, 7, 7, 7, 7,                 /* 90 .. 97 */
  52         7, 7, 7, 7, 7, 7, 7, 7,                 /* 98 .. 9f */
  53         7, 7, 7, 7, 7, 7, 7, 7,                 /* a0 .. a7 */
  54         7, 7, 7, 7, 7, 7, 7, 7,                 /* a8 .. af */
  55         7, 7, 7, 7, 7, 7, 7, 7,                 /* b0 .. b7 */
  56         7, 7, 7, 7, 7, 7, 7, 7,                 /* b8 .. bf */
  57         7, 7, 7, 7, 7, 7, 7, 7,                 /* c0 .. c7 */
  58         7, 7, 7, 7, 7, 7, 7, 7,                 /* c8 .. cf */
  59         7, 7, 7, 7, 7, 7, 7, 7,                 /* d0 .. d7 */
  60         7, 7, 7, 7, 7, 7, 7, 7,                 /* d8 .. df */
  61         7, 7, 7, 7, 7, 7, 7, 7,                 /* e0 .. e7 */
  62         7, 7, 7, 7, 7, 7, 7, 7,                 /* e8 .. ef */
  63         7, 7, 7, 7, 7, 7, 7, 7,                 /* f0 .. f7 */
  64         7, 7, 7, 7, 7, 7, 7, 7,                 /* f8 .. ff */
  65 };
  66 #endif
  67
  68 /*
  69  * xfs_highbit32: get high bit set out of 32-bit argument, -1 if none set.
  70  */
  71 inline int
  72 xfs_highbit32(
  73         __uint32_t      v)
  74 {
  75 #ifdef HAVE_ARCH_HIGHBIT
  76         return highbit32(v);
  77 #else
  78         int             i;
  79
  80         if (v & 0xffff0000)
  81                 if (v & 0xff000000)
  82                         i = 24;
  83                 else
  84                         i = 16;
  85         else if (v & 0x0000ffff)
  86                 if (v & 0x0000ff00)
  87                         i = 8;
  88                 else
  89                         i = 0;
  90         else
  91                 return -1;
  92         return i + xfs_highbit[(v >> i) & 0xff];
  93 #endif
  94 }
  95
  96 /*
  97  * xfs_lowbit64: get low bit set out of 64-bit argument, -1 if none set.
  98  */
  99 int
 100 xfs_lowbit64(
 101         __uint64_t      v)
 102 {
 103         __uint32_t      w = (__uint32_t)v;
 104         int             n = 0;
 105
 106         if (w) {        /* lower bits */
 107                 n = ffs(w);
 108         } else {        /* upper bits */
 109                 w = (__uint32_t)(v >> 32);
 110                 if (w && (n = ffs(w)))
 111                         n += 32;
 112         }
 113         return n - 1;
 114 }
 115
 116 /*
 117  * xfs_highbit64: get high bit set out of 64-bit argument, -1 if none set.
 118  */
 119 int
 120 xfs_highbit64(
 121         __uint64_t      v)
 122 {
 123         __uint32_t      h = (__uint32_t)(v >> 32);
 124
 125         if (h)
 126                 return xfs_highbit32(h) + 32;
 127         return xfs_highbit32((__uint32_t)v);
 128 }
 129
 130
 131 /*
 132  * Return whether bitmap is empty.
 133  * Size is number of words in the bitmap, which is padded to word boundary
 134  * Returns 1 for empty, 0 for non-empty.
 135  */
 136 int
 137 xfs_bitmap_empty(uint *map, uint size)
 138 {
 139         uint i;
 140         uint ret = 0;
 141
 142         for (i = 0; i < size; i++) {
 143                 ret |= map[i];
 144         }
 145
 146         return (ret == 0);
 147 }
 148
 149 /*
 150  * Count the number of contiguous bits set in the bitmap starting with bit
 151  * start_bit.  Size is the size of the bitmap in words.
 152  */
 153 int
 154 xfs_contig_bits(uint *map, uint size, uint start_bit)
 155 {
 156         uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
 157         uint result = 0;
 158         uint tmp;
 159
 160         size <<= BIT_TO_WORD_SHIFT;
 161
 162         ASSERT(start_bit < size);
 163         size -= start_bit & ~(NBWORD - 1);
 164         start_bit &= (NBWORD - 1);
 165         if (start_bit) {
 166                 tmp = *p++;
 167                 /* set to one first offset bits prior to start */
 168                 tmp |= (~0U >> (NBWORD-start_bit));
 169                 if (tmp != ~0U)
 170                         goto found;
 171                 result += NBWORD;
 172                 size -= NBWORD;
 173         }
 174         while (size) {
 175                 if ((tmp = *p++) != ~0U)
 176                         goto found;
 177                 result += NBWORD;
 178                 size -= NBWORD;
 179         }
 180         return result - start_bit;
 181 found:
 182         return result + ffz(tmp) - start_bit;
 183 }
 184
 185 /*
 186  * This takes the bit number to start looking from and
 187  * returns the next set bit from there.  It returns -1
 188  * if there are no more bits set or the start bit is
 189  * beyond the end of the bitmap.
 190  *
 191  * Size is the number of words, not bytes, in the bitmap.
 192  */
 193 int xfs_next_bit(uint *map, uint size, uint start_bit)
 194 {
 195         uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
 196         uint result = start_bit & ~(NBWORD - 1);
 197         uint tmp;
 198
 199         size <<= BIT_TO_WORD_SHIFT;
 200
 201         if (start_bit >= size)
 202                 return -1;
 203         size -= result;
 204         start_bit &= (NBWORD - 1);
 205         if (start_bit) {
 206                 tmp = *p++;
 207                 /* set to zero first offset bits prior to start */
 208                 tmp &= (~0U << start_bit);
 209                 if (tmp != 0U)
 210                         goto found;
 211                 result += NBWORD;
 212                 size -= NBWORD;
 213         }
 214         while (size) {
 215                 if ((tmp = *p++) != 0U)
 216                         goto found;
 217                 result += NBWORD;
 218                 size -= NBWORD;
 219         }
 220         return -1;
 221 found:
 222         return result + ffs(tmp) - 1;
 223 }