include/qemu/hbitmap.h

   1 /*
   2  * Hierarchical Bitmap Data Type
   3  *
   4  * Copyright Red Hat, Inc., 2012
   5  *
   6  * Author: Paolo Bonzini <pbonzini@redhat.com>
   7  *
   8  * This work is licensed under the terms of the GNU GPL, version 2 or
   9  * later.  See the COPYING file in the top-level directory.
  10  */
  11
  12 #ifndef HBITMAP_H
  13 #define HBITMAP_H
  14
  15 #include "bitops.h"
  16 #include "host-utils.h"
  17
  18 typedef struct HBitmap HBitmap;
  19 typedef struct HBitmapIter HBitmapIter;
  20
  21 #define BITS_PER_LEVEL         (BITS_PER_LONG == 32 ? 5 : 6)
  22
  23 /* For 32-bit, the largest that fits in a 4 GiB address space.
  24  * For 64-bit, the number of sectors in 1 PiB.  Good luck, in
  25  * either case... :)
  26  */
  27 #define HBITMAP_LOG_MAX_SIZE   (BITS_PER_LONG == 32 ? 34 : 41)
  28
  29 /* We need to place a sentinel in level 0 to speed up iteration.  Thus,
  30  * we do this instead of HBITMAP_LOG_MAX_SIZE / BITS_PER_LEVEL.  The
  31  * difference is that it allocates an extra level when HBITMAP_LOG_MAX_SIZE
  32  * is an exact multiple of BITS_PER_LEVEL.
  33  */
  34 #define HBITMAP_LEVELS         ((HBITMAP_LOG_MAX_SIZE / BITS_PER_LEVEL) + 1)
  35
  36 struct HBitmapIter {
  37     const HBitmap *hb;
  38
  39     /* Copied from hb for access in the inline functions (hb is opaque).  */
  40     int granularity;
  41
  42     /* Entry offset into the last-level array of longs.  */
  43     size_t pos;
  44
  45     /* The currently-active path in the tree.  Each item of cur[i] stores
  46      * the bits (i.e. the subtrees) yet to be processed under that node.
  47      */
  48     unsigned long cur[HBITMAP_LEVELS];
  49 };
  50
  51 /**
  52  * hbitmap_alloc:
  53  * @size: Number of bits in the bitmap.
  54  * @granularity: Granularity of the bitmap.  Aligned groups of 2^@granularity
  55  * bits will be represented by a single bit.  Each operation on a
  56  * range of bits first rounds the bits to determine which group they land
  57  * in, and then affect the entire set; iteration will only visit the first
  58  * bit of each group.
  59  *
  60  * Allocate a new HBitmap.
  61  */
  62 HBitmap *hbitmap_alloc(uint64_t size, int granularity);
  63
  64 /**
  65  * hbitmap_truncate:
  66  * @hb: The bitmap to change the size of.
  67  * @size: The number of elements to change the bitmap to accommodate.
  68  *
  69  * truncate or grow an existing bitmap to accommodate a new number of elements.
  70  * This may invalidate existing HBitmapIterators.
  71  */
  72 void hbitmap_truncate(HBitmap *hb, uint64_t size);
  73
  74 /**
  75  * hbitmap_merge:
  76  * @a: The bitmap to store the result in.
  77  * @b: The bitmap to merge into @a.
  78  * @return true if the merge was successful,
  79  *         false if it was not attempted.
  80  *
  81  * Merge two bitmaps together.
  82  * A := A (BITOR) B.
  83  * B is left unmodified.
  84  */
  85 bool hbitmap_merge(HBitmap *a, const HBitmap *b);
  86
  87 /**
  88  * hbitmap_empty:
  89  * @hb: HBitmap to operate on.
  90  *
  91  * Return whether the bitmap is empty.
  92  */
  93 bool hbitmap_empty(const HBitmap *hb);
  94
  95 /**
  96  * hbitmap_granularity:
  97  * @hb: HBitmap to operate on.
  98  *
  99  * Return the granularity of the HBitmap.
 100  */
 101 int hbitmap_granularity(const HBitmap *hb);
 102
 103 /**
 104  * hbitmap_count:
 105  * @hb: HBitmap to operate on.
 106  *
 107  * Return the number of bits set in the HBitmap.
 108  */
 109 uint64_t hbitmap_count(const HBitmap *hb);
 110
 111 /**
 112  * hbitmap_set:
 113  * @hb: HBitmap to operate on.
 114  * @start: First bit to set (0-based).
 115  * @count: Number of bits to set.
 116  *
 117  * Set a consecutive range of bits in an HBitmap.
 118  */
 119 void hbitmap_set(HBitmap *hb, uint64_t start, uint64_t count);
 120
 121 /**
 122  * hbitmap_reset:
 123  * @hb: HBitmap to operate on.
 124  * @start: First bit to reset (0-based).
 125  * @count: Number of bits to reset.
 126  *
 127  * Reset a consecutive range of bits in an HBitmap.
 128  */
 129 void hbitmap_reset(HBitmap *hb, uint64_t start, uint64_t count);
 130
 131 /**
 132  * hbitmap_reset_all:
 133  * @hb: HBitmap to operate on.
 134  *
 135  * Reset all bits in an HBitmap.
 136  */
 137 void hbitmap_reset_all(HBitmap *hb);
 138
 139 /**
 140  * hbitmap_get:
 141  * @hb: HBitmap to operate on.
 142  * @item: Bit to query (0-based).
 143  *
 144  * Return whether the @item-th bit in an HBitmap is set.
 145  */
 146 bool hbitmap_get(const HBitmap *hb, uint64_t item);
 147
 148 /**
 149  * hbitmap_free:
 150  * @hb: HBitmap to operate on.
 151  *
 152  * Free an HBitmap and all of its associated memory.
 153  */
 154 void hbitmap_free(HBitmap *hb);
 155
 156 /**
 157  * hbitmap_iter_init:
 158  * @hbi: HBitmapIter to initialize.
 159  * @hb: HBitmap to iterate on.
 160  * @first: First bit to visit (0-based, must be strictly less than the
 161  * size of the bitmap).
 162  *
 163  * Set up @hbi to iterate on the HBitmap @hb.  hbitmap_iter_next will return
 164  * the lowest-numbered bit that is set in @hb, starting at @first.
 165  *
 166  * Concurrent setting of bits is acceptable, and will at worst cause the
 167  * iteration to miss some of those bits.  Resetting bits before the current
 168  * position of the iterator is also okay.  However, concurrent resetting of
 169  * bits can lead to unexpected behavior if the iterator has not yet reached
 170  * those bits.
 171  */
 172 void hbitmap_iter_init(HBitmapIter *hbi, const HBitmap *hb, uint64_t first);
 173
 174 /* hbitmap_iter_skip_words:
 175  * @hbi: HBitmapIter to operate on.
 176  *
 177  * Internal function used by hbitmap_iter_next and hbitmap_iter_next_word.
 178  */
 179 unsigned long hbitmap_iter_skip_words(HBitmapIter *hbi);
 180
 181 /**
 182  * hbitmap_iter_next:
 183  * @hbi: HBitmapIter to operate on.
 184  *
 185  * Return the next bit that is set in @hbi's associated HBitmap,
 186  * or -1 if all remaining bits are zero.
 187  */
 188 static inline int64_t hbitmap_iter_next(HBitmapIter *hbi)
 189 {
 190     unsigned long cur = hbi->cur[HBITMAP_LEVELS - 1];
 191     int64_t item;
 192
 193     if (cur == 0) {
 194         cur = hbitmap_iter_skip_words(hbi);
 195         if (cur == 0) {
 196             return -1;
 197         }
 198     }
 199
 200     /* The next call will resume work from the next bit.  */
 201     hbi->cur[HBITMAP_LEVELS - 1] = cur & (cur - 1);
 202     item = ((uint64_t)hbi->pos << BITS_PER_LEVEL) + ctzl(cur);
 203
 204     return item << hbi->granularity;
 205 }
 206
 207 /**
 208  * hbitmap_iter_next_word:
 209  * @hbi: HBitmapIter to operate on.
 210  * @p_cur: Location where to store the next non-zero word.
 211  *
 212  * Return the index of the next nonzero word that is set in @hbi's
 213  * associated HBitmap, and set *p_cur to the content of that word
 214  * (bits before the index that was passed to hbitmap_iter_init are
 215  * trimmed on the first call).  Return -1, and set *p_cur to zero,
 216  * if all remaining words are zero.
 217  */
 218 static inline size_t hbitmap_iter_next_word(HBitmapIter *hbi, unsigned long *p_cur)
 219 {
 220     unsigned long cur = hbi->cur[HBITMAP_LEVELS - 1];
 221
 222     if (cur == 0) {
 223         cur = hbitmap_iter_skip_words(hbi);
 224         if (cur == 0) {
 225             *p_cur = 0;
 226             return -1;
 227         }
 228     }
 229
 230     /* The next call will resume work from the next word.  */
 231     hbi->cur[HBITMAP_LEVELS - 1] = 0;
 232     *p_cur = cur;
 233     return hbi->pos;
 234 }
 235
 236
 237 #endif