Hi all,
The following functions should compute the union, intersection and
difference of two bitmaps.
Please review the code. Thank you.
Sincerely,
Linda Jacobson
int libxl_bitmap_union(libxl_ctx *ctx, libxl_bitmap *union_bitmap,
libxl_bitmap *bitmap1, libxl_bitmap *bitmap2)
{
int size;
int rc;
GC_INIT(ctx);
// if bitmaps aren't the same size, union should be size of larger bit map
size = (bitmap1->size > bitmap2->size) ? bitmap1->size : bitmap2->size;
libxl_bitmap_init(union_bitmap);
rc = libxl_bitmap_alloc(ctx, union_bitmap, size);
if (rc)
{
// I'm following the coding standards here. First goto I've
written in decades.
goto out;
}
for (int bit = 0; bit < (size * 8); bit++)
{
// libxl_bitmap_test returns 0 if past end of bitmap
// if the bit is set in either bitmap, set it in their union
if (libxl_bitmap_test(bitmap1, bit))
{
libxl_bitmap_set(union_bitmap, bit);
}
else if (libxl_bitmap_test(bitmap2, bit))
{
libxl_bitmap_set(union_bitmap, bit);
}
}
out:
GC_FREE;
return rc;
}
int libxl_bitmap_intersection (libxl_ctx *ctx, libxl_bitmap
*union_bitmap, libxl_bitmap *bitmap1, libxl_bitmap *bitmap2)
{
int size;
int rc;
GC_INIT(ctx);
// if bitmaps aren't the same size, intersection should be size of
smaller bit map
size = (bitmap1->size > bitmap2->size) ? bitmap2->size : bitmap1->size;
libxl_bitmap_init(union_bitmap);
rc = libxl_bitmap_alloc(ctx, union_bitmap, size);
if (rc)
{
goto out;
}
for (int bit = 0; bit < (size * 8); bit++)
{
// libxl_bitmap_test returns 0 if past end of bitmap
// if the bit is set in both bitmaps, set it in their intersection
if (libxl_bitmap_test (bitmap1, bit) && libxl_bitmap_test
(bitmap2, bit) )
{
libxl_bitmap_set (intersection_bitmap, bit);
}
}
out:
GC_FREE;
return rc;
}
int libxl_bitmap_difference(libxl_ctx *ctx, libxl_bitmap *union_bitmap,
libxl_bitmap *bitmap1, libxl_bitmap *bitmap2)
{
int size;
int rc;
GC_INIT(ctx);
// if bitmaps aren't the same size, difference should be size of larger
bit map
size = (bitmap1->size > bitmap2->size) ? bitmap1->size : bitmap2->size;
libxl_bitmap_init(union_bitmap);
rc = libxl_bitmap_alloc(ctx, union_bitmap, size);
if (rc)
{
goto out;
}
for (int bit = 0; bit < (size * 8); bit++)
{
/* libxl_bitmap_test returns 0 if past end of bitmap
if the bit is set in one bitmap and not the other, set it in
their difference
NOTE: if one bit map is larger, this will result in all bits
being set past the size of the smaller bitmap; if this is not
the desired behavior, please let me know
*/
if (libxl_bitmap_test (bitmap1, bit) && (!libxl_bitmap_test
(bitmap2, bit)) )
{
libxl_bitmap_set (difference_bitmap, bit);
}
}
out:
GC_FREE;
return rc;
}
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