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Remove BITMAP_USE_TREE.

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Remove tree-structured bitmap support, in order to reduce complexity and
ease maintenance.  No bitmaps larger than 512 bits have been necessary
since before 4.0.0, and there is no current plan that would increase
maximum bitmap size.  Although tree-structured bitmaps were used on
32-bit platforms prior to this change, the overall benefits were
questionable (higher metadata overhead, higher bitmap modification cost,
marginally lower search cost).
This commit is contained in:
Jason Evans
2017-03-27 01:58:09 -07:00
parent 6258176c87
commit 7c00f04ff4
5 changed files with 0 additions and 307 deletions
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78
src/bitmap.c
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@@ -3,82 +3,6 @@
/******************************************************************************/
#ifdef BITMAP_USE_TREE
void
bitmap_info_init(bitmap_info_t *binfo, size_t nbits) {
unsigned i;
size_t group_count;
assert(nbits > 0);
assert(nbits <= (ZU(1) << LG_BITMAP_MAXBITS));
/*
* Compute the number of groups necessary to store nbits bits, and
* progressively work upward through the levels until reaching a level
* that requires only one group.
*/
binfo->levels[0].group_offset = 0;
group_count = BITMAP_BITS2GROUPS(nbits);
for (i = 1; group_count > 1; i++) {
assert(i < BITMAP_MAX_LEVELS);
binfo->levels[i].group_offset = binfo->levels[i-1].group_offset
+ group_count;
group_count = BITMAP_BITS2GROUPS(group_count);
}
binfo->levels[i].group_offset = binfo->levels[i-1].group_offset
+ group_count;
assert(binfo->levels[i].group_offset <= BITMAP_GROUPS_MAX);
binfo->nlevels = i;
binfo->nbits = nbits;
}
static size_t
bitmap_info_ngroups(const bitmap_info_t *binfo) {
return binfo->levels[binfo->nlevels].group_offset;
}
void
bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo, bool fill) {
size_t extra;
unsigned i;
/*
* Bits are actually inverted with regard to the external bitmap
* interface.
*/
if (fill) {
/* The "filled" bitmap starts out with all 0 bits. */
memset(bitmap, 0, bitmap_size(binfo));
return;
}
/*
* The "empty" bitmap starts out with all 1 bits, except for trailing
* unused bits (if any). Note that each group uses bit 0 to correspond
* to the first logical bit in the group, so extra bits are the most
* significant bits of the last group.
*/
memset(bitmap, 0xffU, bitmap_size(binfo));
extra = (BITMAP_GROUP_NBITS - (binfo->nbits & BITMAP_GROUP_NBITS_MASK))
& BITMAP_GROUP_NBITS_MASK;
if (extra != 0) {
bitmap[binfo->levels[1].group_offset - 1] >>= extra;
}
for (i = 1; i < binfo->nlevels; i++) {
size_t group_count = binfo->levels[i].group_offset -
binfo->levels[i-1].group_offset;
extra = (BITMAP_GROUP_NBITS - (group_count &
BITMAP_GROUP_NBITS_MASK)) & BITMAP_GROUP_NBITS_MASK;
if (extra != 0) {
bitmap[binfo->levels[i+1].group_offset - 1] >>= extra;
}
}
}
#else /* BITMAP_USE_TREE */
void
bitmap_info_init(bitmap_info_t *binfo, size_t nbits) {
assert(nbits > 0);
@@ -110,8 +34,6 @@ bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo, bool fill) {
}
}
#endif /* BITMAP_USE_TREE */
size_t
bitmap_size(const bitmap_info_t *binfo) {
return (bitmap_info_ngroups(binfo) << LG_SIZEOF_BITMAP);