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  * Count of bits set in byte, 0..8.
  70  */
  71 static const char xfs_countbit[256] = {
  72         0, 1, 1, 2, 1, 2, 2, 3,                 /* 00 .. 07 */
  73         1, 2, 2, 3, 2, 3, 3, 4,                 /* 08 .. 0f */
  74         1, 2, 2, 3, 2, 3, 3, 4,                 /* 10 .. 17 */
  75         2, 3, 3, 4, 3, 4, 4, 5,                 /* 18 .. 1f */
  76         1, 2, 2, 3, 2, 3, 3, 4,                 /* 20 .. 27 */
  77         2, 3, 3, 4, 3, 4, 4, 5,                 /* 28 .. 2f */
  78         2, 3, 3, 4, 3, 4, 4, 5,                 /* 30 .. 37 */
  79         3, 4, 4, 5, 4, 5, 5, 6,                 /* 38 .. 3f */
  80         1, 2, 2, 3, 2, 3, 3, 4,                 /* 40 .. 47 */
  81         2, 3, 3, 4, 3, 4, 4, 5,                 /* 48 .. 4f */
  82         2, 3, 3, 4, 3, 4, 4, 5,                 /* 50 .. 57 */
  83         3, 4, 4, 5, 4, 5, 5, 6,                 /* 58 .. 5f */
  84         2, 3, 3, 4, 3, 4, 4, 5,                 /* 60 .. 67 */
  85         3, 4, 4, 5, 4, 5, 5, 6,                 /* 68 .. 6f */
  86         3, 4, 4, 5, 4, 5, 5, 6,                 /* 70 .. 77 */
  87         4, 5, 5, 6, 5, 6, 6, 7,                 /* 78 .. 7f */
  88         1, 2, 2, 3, 2, 3, 3, 4,                 /* 80 .. 87 */
  89         2, 3, 3, 4, 3, 4, 4, 5,                 /* 88 .. 8f */
  90         2, 3, 3, 4, 3, 4, 4, 5,                 /* 90 .. 97 */
  91         3, 4, 4, 5, 4, 5, 5, 6,                 /* 98 .. 9f */
  92         2, 3, 3, 4, 3, 4, 4, 5,                 /* a0 .. a7 */
  93         3, 4, 4, 5, 4, 5, 5, 6,                 /* a8 .. af */
  94         3, 4, 4, 5, 4, 5, 5, 6,                 /* b0 .. b7 */
  95         4, 5, 5, 6, 5, 6, 6, 7,                 /* b8 .. bf */
  96         2, 3, 3, 4, 3, 4, 4, 5,                 /* c0 .. c7 */
  97         3, 4, 4, 5, 4, 5, 5, 6,                 /* c8 .. cf */
  98         3, 4, 4, 5, 4, 5, 5, 6,                 /* d0 .. d7 */
  99         4, 5, 5, 6, 5, 6, 6, 7,                 /* d8 .. df */
 100         3, 4, 4, 5, 4, 5, 5, 6,                 /* e0 .. e7 */
 101         4, 5, 5, 6, 5, 6, 6, 7,                 /* e8 .. ef */
 102         4, 5, 5, 6, 5, 6, 6, 7,                 /* f0 .. f7 */
 103         5, 6, 6, 7, 6, 7, 7, 8,                 /* f8 .. ff */
 104 };
 105
 106 /*
 107  * xfs_highbit32: get high bit set out of 32-bit argument, -1 if none set.
 108  */
 109 inline int
 110 xfs_highbit32(
 111         __uint32_t      v)
 112 {
 113 #ifdef HAVE_ARCH_HIGHBIT
 114         return highbit32(v);
 115 #else
 116         int             i;
 117
 118         if (v & 0xffff0000)
 119                 if (v & 0xff000000)
 120                         i = 24;
 121                 else
 122                         i = 16;
 123         else if (v & 0x0000ffff)
 124                 if (v & 0x0000ff00)
 125                         i = 8;
 126                 else
 127                         i = 0;
 128         else
 129                 return -1;
 130         return i + xfs_highbit[(v >> i) & 0xff];
 131 #endif
 132 }
 133
 134 /*
 135  * xfs_lowbit64: get low bit set out of 64-bit argument, -1 if none set.
 136  */
 137 int
 138 xfs_lowbit64(
 139         __uint64_t      v)
 140 {
 141         __uint32_t      w = (__uint32_t)v;
 142         int             n = 0;
 143
 144         if (w) {        /* lower bits */
 145                 n = ffs(w);
 146         } else {        /* upper bits */
 147                 w = (__uint32_t)(v >> 32);
 148                 if (w && (n = ffs(w)))
 149                         n += 32;
 150         }
 151         return n - 1;
 152 }
 153
 154 /*
 155  * xfs_highbit64: get high bit set out of 64-bit argument, -1 if none set.
 156  */
 157 int
 158 xfs_highbit64(
 159         __uint64_t      v)
 160 {
 161         __uint32_t      h = (__uint32_t)(v >> 32);
 162
 163         if (h)
 164                 return xfs_highbit32(h) + 32;
 165         return xfs_highbit32((__uint32_t)v);
 166 }
 167
 168
 169 /*
 170  * Count the number of bits set in the bitmap starting with bit
 171  * start_bit.  Size is the size of the bitmap in words.
 172  *
 173  * Do the counting by mapping a byte value to the number of set
 174  * bits for that value using the xfs_countbit array, i.e.
 175  * xfs_countbit[0] == 0, xfs_countbit[1] == 1, xfs_countbit[2] == 1,
 176  * xfs_countbit[3] == 2, etc.
 177  */
 178 int
 179 xfs_count_bits(uint *map, uint size, uint start_bit)
 180 {
 181         register int    bits;
 182         register unsigned char  *bytep;
 183         register unsigned char  *end_map;
 184         int             byte_bit;
 185
 186         bits = 0;
 187         end_map = (char*)(map + size);
 188         bytep = (char*)(map + (start_bit & ~0x7));
 189         byte_bit = start_bit & 0x7;
 190
 191         /*
 192          * If the caller fell off the end of the map, return 0.
 193          */
 194         if (bytep >= end_map) {
 195                 return (0);
 196         }
 197
 198         /*
 199          * If start_bit is not byte aligned, then process the
 200          * first byte separately.
 201          */
 202         if (byte_bit != 0) {
 203                 /*
 204                  * Shift off the bits we don't want to look at,
 205                  * before indexing into xfs_countbit.
 206                  */
 207                 bits += xfs_countbit[(*bytep >> byte_bit)];
 208                 bytep++;
 209         }
 210
 211         /*
 212          * Count the bits in each byte until the end of the bitmap.
 213          */
 214         while (bytep < end_map) {
 215                 bits += xfs_countbit[*bytep];
 216                 bytep++;
 217         }
 218
 219         return (bits);
 220 }
 221
 222 /*
 223  * Count the number of contiguous bits set in the bitmap starting with bit
 224  * start_bit.  Size is the size of the bitmap in words.
 225  */
 226 int
 227 xfs_contig_bits(uint *map, uint size, uint start_bit)
 228 {
 229         uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
 230         uint result = 0;
 231         uint tmp;
 232
 233         size <<= BIT_TO_WORD_SHIFT;
 234
 235         ASSERT(start_bit < size);
 236         size -= start_bit & ~(NBWORD - 1);
 237         start_bit &= (NBWORD - 1);
 238         if (start_bit) {
 239                 tmp = *p++;
 240                 /* set to one first offset bits prior to start */
 241                 tmp |= (~0U >> (NBWORD-start_bit));
 242                 if (tmp != ~0U)
 243                         goto found;
 244                 result += NBWORD;
 245                 size -= NBWORD;
 246         }
 247         while (size) {
 248                 if ((tmp = *p++) != ~0U)
 249                         goto found;
 250                 result += NBWORD;
 251                 size -= NBWORD;
 252         }
 253         return result - start_bit;
 254 found:
 255         return result + ffz(tmp) - start_bit;
 256 }
 257
 258 /*
 259  * This takes the bit number to start looking from and
 260  * returns the next set bit from there.  It returns -1
 261  * if there are no more bits set or the start bit is
 262  * beyond the end of the bitmap.
 263  *
 264  * Size is the number of words, not bytes, in the bitmap.
 265  */
 266 int xfs_next_bit(uint *map, uint size, uint start_bit)
 267 {
 268         uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
 269         uint result = start_bit & ~(NBWORD - 1);
 270         uint tmp;
 271
 272         size <<= BIT_TO_WORD_SHIFT;
 273
 274         if (start_bit >= size)
 275                 return -1;
 276         size -= result;
 277         start_bit &= (NBWORD - 1);
 278         if (start_bit) {
 279                 tmp = *p++;
 280                 /* set to zero first offset bits prior to start */
 281                 tmp &= (~0U << start_bit);
 282                 if (tmp != 0U)
 283                         goto found;
 284                 result += NBWORD;
 285                 size -= NBWORD;
 286         }
 287         while (size) {
 288                 if ((tmp = *p++) != 0U)
 289                         goto found;
 290                 result += NBWORD;
 291                 size -= NBWORD;
 292         }
 293         return -1;
 294 found:
 295         return result + ffs(tmp) - 1;
 296 }