Merge remote-tracking branch 'remotes/jasowang/tags/net-pull-request' into staging
[qemu/ar7.git] / util / hbitmap.c
blob305b894a63f15d4327082823861a956cac51dca9
1 /*
2 * Hierarchical Bitmap Data Type
4 * Copyright Red Hat, Inc., 2012
6 * Author: Paolo Bonzini <pbonzini@redhat.com>
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.
12 #include "qemu/osdep.h"
13 #include "qemu/hbitmap.h"
14 #include "qemu/host-utils.h"
15 #include "trace.h"
16 #include "crypto/hash.h"
18 /* HBitmaps provides an array of bits. The bits are stored as usual in an
19 * array of unsigned longs, but HBitmap is also optimized to provide fast
20 * iteration over set bits; going from one bit to the next is O(logB n)
21 * worst case, with B = sizeof(long) * CHAR_BIT: the result is low enough
22 * that the number of levels is in fact fixed.
24 * In order to do this, it stacks multiple bitmaps with progressively coarser
25 * granularity; in all levels except the last, bit N is set iff the N-th
26 * unsigned long is nonzero in the immediately next level. When iteration
27 * completes on the last level it can examine the 2nd-last level to quickly
28 * skip entire words, and even do so recursively to skip blocks of 64 words or
29 * powers thereof (32 on 32-bit machines).
31 * Given an index in the bitmap, it can be split in group of bits like
32 * this (for the 64-bit case):
34 * bits 0-57 => word in the last bitmap | bits 58-63 => bit in the word
35 * bits 0-51 => word in the 2nd-last bitmap | bits 52-57 => bit in the word
36 * bits 0-45 => word in the 3rd-last bitmap | bits 46-51 => bit in the word
38 * So it is easy to move up simply by shifting the index right by
39 * log2(BITS_PER_LONG) bits. To move down, you shift the index left
40 * similarly, and add the word index within the group. Iteration uses
41 * ffs (find first set bit) to find the next word to examine; this
42 * operation can be done in constant time in most current architectures.
44 * Setting or clearing a range of m bits on all levels, the work to perform
45 * is O(m + m/W + m/W^2 + ...), which is O(m) like on a regular bitmap.
47 * When iterating on a bitmap, each bit (on any level) is only visited
48 * once. Hence, The total cost of visiting a bitmap with m bits in it is
49 * the number of bits that are set in all bitmaps. Unless the bitmap is
50 * extremely sparse, this is also O(m + m/W + m/W^2 + ...), so the amortized
51 * cost of advancing from one bit to the next is usually constant (worst case
52 * O(logB n) as in the non-amortized complexity).
55 struct HBitmap {
57 * Size of the bitmap, as requested in hbitmap_alloc or in hbitmap_truncate.
59 uint64_t orig_size;
61 /* Number of total bits in the bottom level. */
62 uint64_t size;
64 /* Number of set bits in the bottom level. */
65 uint64_t count;
67 /* A scaling factor. Given a granularity of G, each bit in the bitmap will
68 * will actually represent a group of 2^G elements. Each operation on a
69 * range of bits first rounds the bits to determine which group they land
70 * in, and then affect the entire page; iteration will only visit the first
71 * bit of each group. Here is an example of operations in a size-16,
72 * granularity-1 HBitmap:
74 * initial state 00000000
75 * set(start=0, count=9) 11111000 (iter: 0, 2, 4, 6, 8)
76 * reset(start=1, count=3) 00111000 (iter: 4, 6, 8)
77 * set(start=9, count=2) 00111100 (iter: 4, 6, 8, 10)
78 * reset(start=5, count=5) 00000000
80 * From an implementation point of view, when setting or resetting bits,
81 * the bitmap will scale bit numbers right by this amount of bits. When
82 * iterating, the bitmap will scale bit numbers left by this amount of
83 * bits.
85 int granularity;
87 /* A meta dirty bitmap to track the dirtiness of bits in this HBitmap. */
88 HBitmap *meta;
90 /* A number of progressively less coarse bitmaps (i.e. level 0 is the
91 * coarsest). Each bit in level N represents a word in level N+1 that
92 * has a set bit, except the last level where each bit represents the
93 * actual bitmap.
95 * Note that all bitmaps have the same number of levels. Even a 1-bit
96 * bitmap will still allocate HBITMAP_LEVELS arrays.
98 unsigned long *levels[HBITMAP_LEVELS];
100 /* The length of each levels[] array. */
101 uint64_t sizes[HBITMAP_LEVELS];
104 /* Advance hbi to the next nonzero word and return it. hbi->pos
105 * is updated. Returns zero if we reach the end of the bitmap.
107 static unsigned long hbitmap_iter_skip_words(HBitmapIter *hbi)
109 size_t pos = hbi->pos;
110 const HBitmap *hb = hbi->hb;
111 unsigned i = HBITMAP_LEVELS - 1;
113 unsigned long cur;
114 do {
115 i--;
116 pos >>= BITS_PER_LEVEL;
117 cur = hbi->cur[i] & hb->levels[i][pos];
118 } while (cur == 0);
120 /* Check for end of iteration. We always use fewer than BITS_PER_LONG
121 * bits in the level 0 bitmap; thus we can repurpose the most significant
122 * bit as a sentinel. The sentinel is set in hbitmap_alloc and ensures
123 * that the above loop ends even without an explicit check on i.
126 if (i == 0 && cur == (1UL << (BITS_PER_LONG - 1))) {
127 return 0;
129 for (; i < HBITMAP_LEVELS - 1; i++) {
130 /* Shift back pos to the left, matching the right shifts above.
131 * The index of this word's least significant set bit provides
132 * the low-order bits.
134 assert(cur);
135 pos = (pos << BITS_PER_LEVEL) + ctzl(cur);
136 hbi->cur[i] = cur & (cur - 1);
138 /* Set up next level for iteration. */
139 cur = hb->levels[i + 1][pos];
142 hbi->pos = pos;
143 trace_hbitmap_iter_skip_words(hbi->hb, hbi, pos, cur);
145 assert(cur);
146 return cur;
149 int64_t hbitmap_iter_next(HBitmapIter *hbi)
151 unsigned long cur = hbi->cur[HBITMAP_LEVELS - 1] &
152 hbi->hb->levels[HBITMAP_LEVELS - 1][hbi->pos];
153 int64_t item;
155 if (cur == 0) {
156 cur = hbitmap_iter_skip_words(hbi);
157 if (cur == 0) {
158 return -1;
162 /* The next call will resume work from the next bit. */
163 hbi->cur[HBITMAP_LEVELS - 1] = cur & (cur - 1);
164 item = ((uint64_t)hbi->pos << BITS_PER_LEVEL) + ctzl(cur);
166 return item << hbi->granularity;
169 void hbitmap_iter_init(HBitmapIter *hbi, const HBitmap *hb, uint64_t first)
171 unsigned i, bit;
172 uint64_t pos;
174 hbi->hb = hb;
175 pos = first >> hb->granularity;
176 assert(pos < hb->size);
177 hbi->pos = pos >> BITS_PER_LEVEL;
178 hbi->granularity = hb->granularity;
180 for (i = HBITMAP_LEVELS; i-- > 0; ) {
181 bit = pos & (BITS_PER_LONG - 1);
182 pos >>= BITS_PER_LEVEL;
184 /* Drop bits representing items before first. */
185 hbi->cur[i] = hb->levels[i][pos] & ~((1UL << bit) - 1);
187 /* We have already added level i+1, so the lowest set bit has
188 * been processed. Clear it.
190 if (i != HBITMAP_LEVELS - 1) {
191 hbi->cur[i] &= ~(1UL << bit);
196 int64_t hbitmap_next_dirty(const HBitmap *hb, int64_t start, int64_t count)
198 HBitmapIter hbi;
199 int64_t first_dirty_off;
200 uint64_t end;
202 assert(start >= 0 && count >= 0);
204 if (start >= hb->orig_size || count == 0) {
205 return -1;
208 end = count > hb->orig_size - start ? hb->orig_size : start + count;
210 hbitmap_iter_init(&hbi, hb, start);
211 first_dirty_off = hbitmap_iter_next(&hbi);
213 if (first_dirty_off < 0 || first_dirty_off >= end) {
214 return -1;
217 return MAX(start, first_dirty_off);
220 int64_t hbitmap_next_zero(const HBitmap *hb, int64_t start, int64_t count)
222 size_t pos = (start >> hb->granularity) >> BITS_PER_LEVEL;
223 unsigned long *last_lev = hb->levels[HBITMAP_LEVELS - 1];
224 unsigned long cur = last_lev[pos];
225 unsigned start_bit_offset;
226 uint64_t end_bit, sz;
227 int64_t res;
229 assert(start >= 0 && count >= 0);
231 if (start >= hb->orig_size || count == 0) {
232 return -1;
235 end_bit = count > hb->orig_size - start ?
236 hb->size :
237 ((start + count - 1) >> hb->granularity) + 1;
238 sz = (end_bit + BITS_PER_LONG - 1) >> BITS_PER_LEVEL;
240 /* There may be some zero bits in @cur before @start. We are not interested
241 * in them, let's set them.
243 start_bit_offset = (start >> hb->granularity) & (BITS_PER_LONG - 1);
244 cur |= (1UL << start_bit_offset) - 1;
245 assert((start >> hb->granularity) < hb->size);
247 if (cur == (unsigned long)-1) {
248 do {
249 pos++;
250 } while (pos < sz && last_lev[pos] == (unsigned long)-1);
252 if (pos >= sz) {
253 return -1;
256 cur = last_lev[pos];
259 res = (pos << BITS_PER_LEVEL) + ctol(cur);
260 if (res >= end_bit) {
261 return -1;
264 res = res << hb->granularity;
265 if (res < start) {
266 assert(((start - res) >> hb->granularity) == 0);
267 return start;
270 return res;
273 bool hbitmap_next_dirty_area(const HBitmap *hb, int64_t start, int64_t end,
274 int64_t max_dirty_count,
275 int64_t *dirty_start, int64_t *dirty_count)
277 int64_t next_zero;
279 assert(start >= 0 && end >= 0 && max_dirty_count > 0);
281 end = MIN(end, hb->orig_size);
282 if (start >= end) {
283 return false;
286 start = hbitmap_next_dirty(hb, start, end - start);
287 if (start < 0) {
288 return false;
291 end = start + MIN(end - start, max_dirty_count);
293 next_zero = hbitmap_next_zero(hb, start, end - start);
294 if (next_zero >= 0) {
295 end = next_zero;
298 *dirty_start = start;
299 *dirty_count = end - start;
301 return true;
304 bool hbitmap_empty(const HBitmap *hb)
306 return hb->count == 0;
309 int hbitmap_granularity(const HBitmap *hb)
311 return hb->granularity;
314 uint64_t hbitmap_count(const HBitmap *hb)
316 return hb->count << hb->granularity;
320 * hbitmap_iter_next_word:
321 * @hbi: HBitmapIter to operate on.
322 * @p_cur: Location where to store the next non-zero word.
324 * Return the index of the next nonzero word that is set in @hbi's
325 * associated HBitmap, and set *p_cur to the content of that word
326 * (bits before the index that was passed to hbitmap_iter_init are
327 * trimmed on the first call). Return -1, and set *p_cur to zero,
328 * if all remaining words are zero.
330 static size_t hbitmap_iter_next_word(HBitmapIter *hbi, unsigned long *p_cur)
332 unsigned long cur = hbi->cur[HBITMAP_LEVELS - 1];
334 if (cur == 0) {
335 cur = hbitmap_iter_skip_words(hbi);
336 if (cur == 0) {
337 *p_cur = 0;
338 return -1;
342 /* The next call will resume work from the next word. */
343 hbi->cur[HBITMAP_LEVELS - 1] = 0;
344 *p_cur = cur;
345 return hbi->pos;
348 /* Count the number of set bits between start and end, not accounting for
349 * the granularity. Also an example of how to use hbitmap_iter_next_word.
351 static uint64_t hb_count_between(HBitmap *hb, uint64_t start, uint64_t last)
353 HBitmapIter hbi;
354 uint64_t count = 0;
355 uint64_t end = last + 1;
356 unsigned long cur;
357 size_t pos;
359 hbitmap_iter_init(&hbi, hb, start << hb->granularity);
360 for (;;) {
361 pos = hbitmap_iter_next_word(&hbi, &cur);
362 if (pos >= (end >> BITS_PER_LEVEL)) {
363 break;
365 count += ctpopl(cur);
368 if (pos == (end >> BITS_PER_LEVEL)) {
369 /* Drop bits representing the END-th and subsequent items. */
370 int bit = end & (BITS_PER_LONG - 1);
371 cur &= (1UL << bit) - 1;
372 count += ctpopl(cur);
375 return count;
378 /* Setting starts at the last layer and propagates up if an element
379 * changes.
381 static inline bool hb_set_elem(unsigned long *elem, uint64_t start, uint64_t last)
383 unsigned long mask;
384 unsigned long old;
386 assert((last >> BITS_PER_LEVEL) == (start >> BITS_PER_LEVEL));
387 assert(start <= last);
389 mask = 2UL << (last & (BITS_PER_LONG - 1));
390 mask -= 1UL << (start & (BITS_PER_LONG - 1));
391 old = *elem;
392 *elem |= mask;
393 return old != *elem;
396 /* The recursive workhorse (the depth is limited to HBITMAP_LEVELS)...
397 * Returns true if at least one bit is changed. */
398 static bool hb_set_between(HBitmap *hb, int level, uint64_t start,
399 uint64_t last)
401 size_t pos = start >> BITS_PER_LEVEL;
402 size_t lastpos = last >> BITS_PER_LEVEL;
403 bool changed = false;
404 size_t i;
406 i = pos;
407 if (i < lastpos) {
408 uint64_t next = (start | (BITS_PER_LONG - 1)) + 1;
409 changed |= hb_set_elem(&hb->levels[level][i], start, next - 1);
410 for (;;) {
411 start = next;
412 next += BITS_PER_LONG;
413 if (++i == lastpos) {
414 break;
416 changed |= (hb->levels[level][i] == 0);
417 hb->levels[level][i] = ~0UL;
420 changed |= hb_set_elem(&hb->levels[level][i], start, last);
422 /* If there was any change in this layer, we may have to update
423 * the one above.
425 if (level > 0 && changed) {
426 hb_set_between(hb, level - 1, pos, lastpos);
428 return changed;
431 void hbitmap_set(HBitmap *hb, uint64_t start, uint64_t count)
433 /* Compute range in the last layer. */
434 uint64_t first, n;
435 uint64_t last = start + count - 1;
437 if (count == 0) {
438 return;
441 trace_hbitmap_set(hb, start, count,
442 start >> hb->granularity, last >> hb->granularity);
444 first = start >> hb->granularity;
445 last >>= hb->granularity;
446 assert(last < hb->size);
447 n = last - first + 1;
449 hb->count += n - hb_count_between(hb, first, last);
450 if (hb_set_between(hb, HBITMAP_LEVELS - 1, first, last) &&
451 hb->meta) {
452 hbitmap_set(hb->meta, start, count);
456 /* Resetting works the other way round: propagate up if the new
457 * value is zero.
459 static inline bool hb_reset_elem(unsigned long *elem, uint64_t start, uint64_t last)
461 unsigned long mask;
462 bool blanked;
464 assert((last >> BITS_PER_LEVEL) == (start >> BITS_PER_LEVEL));
465 assert(start <= last);
467 mask = 2UL << (last & (BITS_PER_LONG - 1));
468 mask -= 1UL << (start & (BITS_PER_LONG - 1));
469 blanked = *elem != 0 && ((*elem & ~mask) == 0);
470 *elem &= ~mask;
471 return blanked;
474 /* The recursive workhorse (the depth is limited to HBITMAP_LEVELS)...
475 * Returns true if at least one bit is changed. */
476 static bool hb_reset_between(HBitmap *hb, int level, uint64_t start,
477 uint64_t last)
479 size_t pos = start >> BITS_PER_LEVEL;
480 size_t lastpos = last >> BITS_PER_LEVEL;
481 bool changed = false;
482 size_t i;
484 i = pos;
485 if (i < lastpos) {
486 uint64_t next = (start | (BITS_PER_LONG - 1)) + 1;
488 /* Here we need a more complex test than when setting bits. Even if
489 * something was changed, we must not blank bits in the upper level
490 * unless the lower-level word became entirely zero. So, remove pos
491 * from the upper-level range if bits remain set.
493 if (hb_reset_elem(&hb->levels[level][i], start, next - 1)) {
494 changed = true;
495 } else {
496 pos++;
499 for (;;) {
500 start = next;
501 next += BITS_PER_LONG;
502 if (++i == lastpos) {
503 break;
505 changed |= (hb->levels[level][i] != 0);
506 hb->levels[level][i] = 0UL;
510 /* Same as above, this time for lastpos. */
511 if (hb_reset_elem(&hb->levels[level][i], start, last)) {
512 changed = true;
513 } else {
514 lastpos--;
517 if (level > 0 && changed) {
518 hb_reset_between(hb, level - 1, pos, lastpos);
521 return changed;
525 void hbitmap_reset(HBitmap *hb, uint64_t start, uint64_t count)
527 /* Compute range in the last layer. */
528 uint64_t first;
529 uint64_t last = start + count - 1;
530 uint64_t gran = 1ULL << hb->granularity;
532 if (count == 0) {
533 return;
536 assert(QEMU_IS_ALIGNED(start, gran));
537 assert(QEMU_IS_ALIGNED(count, gran) || (start + count == hb->orig_size));
539 trace_hbitmap_reset(hb, start, count,
540 start >> hb->granularity, last >> hb->granularity);
542 first = start >> hb->granularity;
543 last >>= hb->granularity;
544 assert(last < hb->size);
546 hb->count -= hb_count_between(hb, first, last);
547 if (hb_reset_between(hb, HBITMAP_LEVELS - 1, first, last) &&
548 hb->meta) {
549 hbitmap_set(hb->meta, start, count);
553 void hbitmap_reset_all(HBitmap *hb)
555 unsigned int i;
557 /* Same as hbitmap_alloc() except for memset() instead of malloc() */
558 for (i = HBITMAP_LEVELS; --i >= 1; ) {
559 memset(hb->levels[i], 0, hb->sizes[i] * sizeof(unsigned long));
562 hb->levels[0][0] = 1UL << (BITS_PER_LONG - 1);
563 hb->count = 0;
566 bool hbitmap_is_serializable(const HBitmap *hb)
568 /* Every serialized chunk must be aligned to 64 bits so that endianness
569 * requirements can be fulfilled on both 64 bit and 32 bit hosts.
570 * We have hbitmap_serialization_align() which converts this
571 * alignment requirement from bitmap bits to items covered (e.g. sectors).
572 * That value is:
573 * 64 << hb->granularity
574 * Since this value must not exceed UINT64_MAX, hb->granularity must be
575 * less than 58 (== 64 - 6, where 6 is ld(64), i.e. 1 << 6 == 64).
577 * In order for hbitmap_serialization_align() to always return a
578 * meaningful value, bitmaps that are to be serialized must have a
579 * granularity of less than 58. */
581 return hb->granularity < 58;
584 bool hbitmap_get(const HBitmap *hb, uint64_t item)
586 /* Compute position and bit in the last layer. */
587 uint64_t pos = item >> hb->granularity;
588 unsigned long bit = 1UL << (pos & (BITS_PER_LONG - 1));
589 assert(pos < hb->size);
591 return (hb->levels[HBITMAP_LEVELS - 1][pos >> BITS_PER_LEVEL] & bit) != 0;
594 uint64_t hbitmap_serialization_align(const HBitmap *hb)
596 assert(hbitmap_is_serializable(hb));
598 /* Require at least 64 bit granularity to be safe on both 64 bit and 32 bit
599 * hosts. */
600 return UINT64_C(64) << hb->granularity;
603 /* Start should be aligned to serialization granularity, chunk size should be
604 * aligned to serialization granularity too, except for last chunk.
606 static void serialization_chunk(const HBitmap *hb,
607 uint64_t start, uint64_t count,
608 unsigned long **first_el, uint64_t *el_count)
610 uint64_t last = start + count - 1;
611 uint64_t gran = hbitmap_serialization_align(hb);
613 assert((start & (gran - 1)) == 0);
614 assert((last >> hb->granularity) < hb->size);
615 if ((last >> hb->granularity) != hb->size - 1) {
616 assert((count & (gran - 1)) == 0);
619 start = (start >> hb->granularity) >> BITS_PER_LEVEL;
620 last = (last >> hb->granularity) >> BITS_PER_LEVEL;
622 *first_el = &hb->levels[HBITMAP_LEVELS - 1][start];
623 *el_count = last - start + 1;
626 uint64_t hbitmap_serialization_size(const HBitmap *hb,
627 uint64_t start, uint64_t count)
629 uint64_t el_count;
630 unsigned long *cur;
632 if (!count) {
633 return 0;
635 serialization_chunk(hb, start, count, &cur, &el_count);
637 return el_count * sizeof(unsigned long);
640 void hbitmap_serialize_part(const HBitmap *hb, uint8_t *buf,
641 uint64_t start, uint64_t count)
643 uint64_t el_count;
644 unsigned long *cur, *end;
646 if (!count) {
647 return;
649 serialization_chunk(hb, start, count, &cur, &el_count);
650 end = cur + el_count;
652 while (cur != end) {
653 unsigned long el =
654 (BITS_PER_LONG == 32 ? cpu_to_le32(*cur) : cpu_to_le64(*cur));
656 memcpy(buf, &el, sizeof(el));
657 buf += sizeof(el);
658 cur++;
662 void hbitmap_deserialize_part(HBitmap *hb, uint8_t *buf,
663 uint64_t start, uint64_t count,
664 bool finish)
666 uint64_t el_count;
667 unsigned long *cur, *end;
669 if (!count) {
670 return;
672 serialization_chunk(hb, start, count, &cur, &el_count);
673 end = cur + el_count;
675 while (cur != end) {
676 memcpy(cur, buf, sizeof(*cur));
678 if (BITS_PER_LONG == 32) {
679 le32_to_cpus((uint32_t *)cur);
680 } else {
681 le64_to_cpus((uint64_t *)cur);
684 buf += sizeof(unsigned long);
685 cur++;
687 if (finish) {
688 hbitmap_deserialize_finish(hb);
692 void hbitmap_deserialize_zeroes(HBitmap *hb, uint64_t start, uint64_t count,
693 bool finish)
695 uint64_t el_count;
696 unsigned long *first;
698 if (!count) {
699 return;
701 serialization_chunk(hb, start, count, &first, &el_count);
703 memset(first, 0, el_count * sizeof(unsigned long));
704 if (finish) {
705 hbitmap_deserialize_finish(hb);
709 void hbitmap_deserialize_ones(HBitmap *hb, uint64_t start, uint64_t count,
710 bool finish)
712 uint64_t el_count;
713 unsigned long *first;
715 if (!count) {
716 return;
718 serialization_chunk(hb, start, count, &first, &el_count);
720 memset(first, 0xff, el_count * sizeof(unsigned long));
721 if (finish) {
722 hbitmap_deserialize_finish(hb);
726 void hbitmap_deserialize_finish(HBitmap *bitmap)
728 int64_t i, size, prev_size;
729 int lev;
731 /* restore levels starting from penultimate to zero level, assuming
732 * that the last level is ok */
733 size = MAX((bitmap->size + BITS_PER_LONG - 1) >> BITS_PER_LEVEL, 1);
734 for (lev = HBITMAP_LEVELS - 1; lev-- > 0; ) {
735 prev_size = size;
736 size = MAX((size + BITS_PER_LONG - 1) >> BITS_PER_LEVEL, 1);
737 memset(bitmap->levels[lev], 0, size * sizeof(unsigned long));
739 for (i = 0; i < prev_size; ++i) {
740 if (bitmap->levels[lev + 1][i]) {
741 bitmap->levels[lev][i >> BITS_PER_LEVEL] |=
742 1UL << (i & (BITS_PER_LONG - 1));
747 bitmap->levels[0][0] |= 1UL << (BITS_PER_LONG - 1);
748 bitmap->count = hb_count_between(bitmap, 0, bitmap->size - 1);
751 void hbitmap_free(HBitmap *hb)
753 unsigned i;
754 assert(!hb->meta);
755 for (i = HBITMAP_LEVELS; i-- > 0; ) {
756 g_free(hb->levels[i]);
758 g_free(hb);
761 HBitmap *hbitmap_alloc(uint64_t size, int granularity)
763 HBitmap *hb = g_new0(struct HBitmap, 1);
764 unsigned i;
766 assert(size <= INT64_MAX);
767 hb->orig_size = size;
769 assert(granularity >= 0 && granularity < 64);
770 size = (size + (1ULL << granularity) - 1) >> granularity;
771 assert(size <= ((uint64_t)1 << HBITMAP_LOG_MAX_SIZE));
773 hb->size = size;
774 hb->granularity = granularity;
775 for (i = HBITMAP_LEVELS; i-- > 0; ) {
776 size = MAX((size + BITS_PER_LONG - 1) >> BITS_PER_LEVEL, 1);
777 hb->sizes[i] = size;
778 hb->levels[i] = g_new0(unsigned long, size);
781 /* We necessarily have free bits in level 0 due to the definition
782 * of HBITMAP_LEVELS, so use one for a sentinel. This speeds up
783 * hbitmap_iter_skip_words.
785 assert(size == 1);
786 hb->levels[0][0] |= 1UL << (BITS_PER_LONG - 1);
787 return hb;
790 void hbitmap_truncate(HBitmap *hb, uint64_t size)
792 bool shrink;
793 unsigned i;
794 uint64_t num_elements = size;
795 uint64_t old;
797 assert(size <= INT64_MAX);
798 hb->orig_size = size;
800 /* Size comes in as logical elements, adjust for granularity. */
801 size = (size + (1ULL << hb->granularity) - 1) >> hb->granularity;
802 assert(size <= ((uint64_t)1 << HBITMAP_LOG_MAX_SIZE));
803 shrink = size < hb->size;
805 /* bit sizes are identical; nothing to do. */
806 if (size == hb->size) {
807 return;
810 /* If we're losing bits, let's clear those bits before we invalidate all of
811 * our invariants. This helps keep the bitcount consistent, and will prevent
812 * us from carrying around garbage bits beyond the end of the map.
814 if (shrink) {
815 /* Don't clear partial granularity groups;
816 * start at the first full one. */
817 uint64_t start = ROUND_UP(num_elements, UINT64_C(1) << hb->granularity);
818 uint64_t fix_count = (hb->size << hb->granularity) - start;
820 assert(fix_count);
821 hbitmap_reset(hb, start, fix_count);
824 hb->size = size;
825 for (i = HBITMAP_LEVELS; i-- > 0; ) {
826 size = MAX(BITS_TO_LONGS(size), 1);
827 if (hb->sizes[i] == size) {
828 break;
830 old = hb->sizes[i];
831 hb->sizes[i] = size;
832 hb->levels[i] = g_realloc(hb->levels[i], size * sizeof(unsigned long));
833 if (!shrink) {
834 memset(&hb->levels[i][old], 0x00,
835 (size - old) * sizeof(*hb->levels[i]));
838 if (hb->meta) {
839 hbitmap_truncate(hb->meta, hb->size << hb->granularity);
843 bool hbitmap_can_merge(const HBitmap *a, const HBitmap *b)
845 return (a->orig_size == b->orig_size);
849 * hbitmap_sparse_merge: performs dst = dst | src
850 * works with differing granularities.
851 * best used when src is sparsely populated.
853 static void hbitmap_sparse_merge(HBitmap *dst, const HBitmap *src)
855 int64_t offset;
856 int64_t count;
858 for (offset = 0;
859 hbitmap_next_dirty_area(src, offset, src->orig_size, INT64_MAX,
860 &offset, &count);
861 offset += count)
863 hbitmap_set(dst, offset, count);
868 * Given HBitmaps A and B, let R := A (BITOR) B.
869 * Bitmaps A and B will not be modified,
870 * except when bitmap R is an alias of A or B.
872 * @return true if the merge was successful,
873 * false if it was not attempted.
875 bool hbitmap_merge(const HBitmap *a, const HBitmap *b, HBitmap *result)
877 int i;
878 uint64_t j;
880 if (!hbitmap_can_merge(a, b) || !hbitmap_can_merge(a, result)) {
881 return false;
883 assert(hbitmap_can_merge(b, result));
885 if ((!hbitmap_count(a) && result == b) ||
886 (!hbitmap_count(b) && result == a)) {
887 return true;
890 if (!hbitmap_count(a) && !hbitmap_count(b)) {
891 hbitmap_reset_all(result);
892 return true;
895 if (a->granularity != b->granularity) {
896 if ((a != result) && (b != result)) {
897 hbitmap_reset_all(result);
899 if (a != result) {
900 hbitmap_sparse_merge(result, a);
902 if (b != result) {
903 hbitmap_sparse_merge(result, b);
905 return true;
908 /* This merge is O(size), as BITS_PER_LONG and HBITMAP_LEVELS are constant.
909 * It may be possible to improve running times for sparsely populated maps
910 * by using hbitmap_iter_next, but this is suboptimal for dense maps.
912 assert(a->size == b->size);
913 for (i = HBITMAP_LEVELS - 1; i >= 0; i--) {
914 for (j = 0; j < a->sizes[i]; j++) {
915 result->levels[i][j] = a->levels[i][j] | b->levels[i][j];
919 /* Recompute the dirty count */
920 result->count = hb_count_between(result, 0, result->size - 1);
922 return true;
925 char *hbitmap_sha256(const HBitmap *bitmap, Error **errp)
927 size_t size = bitmap->sizes[HBITMAP_LEVELS - 1] * sizeof(unsigned long);
928 char *data = (char *)bitmap->levels[HBITMAP_LEVELS - 1];
929 char *hash = NULL;
930 qcrypto_hash_digest(QCRYPTO_HASH_ALG_SHA256, data, size, &hash, errp);
932 return hash;