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bitmap: Add bitmap_copy_with_{src|dst}_offset()

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These helpers copy the source bitmap to destination bitmap with a
shift either on the src or dst bitmap.

Meanwhile, we never have bitmap tests but we should.

This patch also introduces the initial test cases for utils/bitmap.c
but it only tests the newly introduced functions.

Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Message-Id: <20190603065056.25211-5-peterx@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

---

Bitmap test used sizeof(unsigned long) instead of BITS_PER_LONG.
This commit is contained in:
Peter Xu 2019-06-03 14:50:49 +08:00 • committed by Juan Quintela
parent ae7a2bca8a
commit ad37f24d57
4 changed files with 168 additions and 0 deletions
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85
util/bitmap.c
View file

@ -402,3 +402,88 @@ void bitmap_to_le(unsigned long *dst, const unsigned long *src,
{
bitmap_to_from_le(dst, src, nbits);
}
/*
* Copy "src" bitmap with a positive offset and put it into the "dst"
* bitmap. The caller needs to make sure the bitmap size of "src"
* is bigger than (shift + nbits).
*/
void bitmap_copy_with_src_offset(unsigned long *dst, const unsigned long *src,
unsigned long shift, unsigned long nbits)
{
unsigned long left_mask, right_mask, last_mask;
/* Proper shift src pointer to the first word to copy from */
src += BIT_WORD(shift);
shift %= BITS_PER_LONG;
if (!shift) {
/* Fast path */
bitmap_copy(dst, src, nbits);
return;
}
right_mask = (1ul << shift) - 1;
left_mask = ~right_mask;
while (nbits >= BITS_PER_LONG) {
*dst = (*src & left_mask) >> shift;
*dst |= (src[1] & right_mask) << (BITS_PER_LONG - shift);
dst++;
src++;
nbits -= BITS_PER_LONG;
}
if (nbits > BITS_PER_LONG - shift) {
*dst = (*src & left_mask) >> shift;
nbits -= BITS_PER_LONG - shift;
last_mask = (1ul << nbits) - 1;
*dst |= (src[1] & last_mask) << (BITS_PER_LONG - shift);
} else if (nbits) {
last_mask = (1ul << nbits) - 1;
*dst = (*src >> shift) & last_mask;
}
}
/*
* Copy "src" bitmap into the "dst" bitmap with an offset in the
* "dst". The caller needs to make sure the bitmap size of "dst" is
* bigger than (shift + nbits).
*/
void bitmap_copy_with_dst_offset(unsigned long *dst, const unsigned long *src,
unsigned long shift, unsigned long nbits)
{
unsigned long left_mask, right_mask, last_mask;
/* Proper shift dst pointer to the first word to copy from */
dst += BIT_WORD(shift);
shift %= BITS_PER_LONG;
if (!shift) {
/* Fast path */
bitmap_copy(dst, src, nbits);
return;
}
right_mask = (1ul << (BITS_PER_LONG - shift)) - 1;
left_mask = ~right_mask;
*dst &= (1ul << shift) - 1;
while (nbits >= BITS_PER_LONG) {
*dst |= (*src & right_mask) << shift;
dst[1] = (*src & left_mask) >> (BITS_PER_LONG - shift);
dst++;
src++;
nbits -= BITS_PER_LONG;
}
if (nbits > BITS_PER_LONG - shift) {
*dst |= (*src & right_mask) << shift;
nbits -= BITS_PER_LONG - shift;
last_mask = ((1ul << nbits) - 1) << (BITS_PER_LONG - shift);
dst[1] = (*src & last_mask) >> (BITS_PER_LONG - shift);
} else if (nbits) {
last_mask = (1ul << nbits) - 1;
*dst |= (*src & last_mask) << shift;
}
}