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libext2fs: optimize rb_get_bmap_range() 

This simplifies the rb_get_bmap_range() function and speeds it up for
the case where most of the bitmap is zero.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
debian-1.42.9
Theodore Ts'o 2012-11-24 18:35:42 -05:00
parent c6b006ea6c
commit c3f9641eaf
1 changed files with 8 additions and 17 deletions
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25
lib/ext2fs/blkmap64_rb.c
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@ -741,32 +741,23 @@ static errcode_t rb_get_bmap_range(ext2fs_generic_bitmap bitmap,
break;
}
pos = start;
memset(out, 0, (num + 7) >> 3);
for (; parent != NULL; parent = next) {
next = ext2fs_rb_next(parent);
ext = ext2fs_rb_entry(parent, struct bmap_rb_extent, node);
while (((pos - start) < num) &&
(pos < ext->start)) {
ext2fs_fast_clear_bit64((pos - start), out);
pos++;
}
pos = ext->start;
if (pos < start)
pos = start;
if ((pos - start) >= num)
return 0;
while (((pos - start) < num) &&
(pos < (ext->start + ext->count))) {
while (pos < (ext->start + ext->count)) {
if ((pos - start) >= num)
return 0;
ext2fs_fast_set_bit64((pos - start), out);
pos++;
}
}
while ((pos - start) < num) {
ext2fs_fast_clear_bit64((pos - start), out);
pos++;
}
return 0;
}