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libsepol: optimize ebitmap_xor 

Iterate on nodes instead of single bits to save node resolution for each
single bit.

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Acked-by: James Carter <jwcart2@gmail.com>
This commit is contained in:
Christian Göttsche 2022-07-19 17:30:43 +02:00 committed by James Carter
parent efcd008148
commit f174045525
1 changed files with 43 additions and 6 deletions
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49
libsepol/src/ebitmap.c
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@ -117,14 +117,51 @@ int ebitmap_and(ebitmap_t *dst, const ebitmap_t *e1, const ebitmap_t *e2)
int ebitmap_xor(ebitmap_t *dst, const ebitmap_t *e1, const ebitmap_t *e2)
{
unsigned int i, length = max(ebitmap_length(e1), ebitmap_length(e2));
const ebitmap_node_t *n1, *n2;
ebitmap_node_t *new, *prev = NULL;
uint32_t startbit;
MAPTYPE map;
ebitmap_init(dst);
for (i=0; i < length; i++) {
int val = ebitmap_get_bit(e1, i) ^ ebitmap_get_bit(e2, i);
int rc = ebitmap_set_bit(dst, i, val);
if (rc < 0)
return rc;
n1 = e1->node;
n2 = e2->node;
while (n1 || n2) {
if (n1 && n2 && n1->startbit == n2->startbit) {
startbit = n1->startbit;
map = n1->map ^ n2->map;
n1 = n1->next;
n2 = n2->next;
} else if (!n2 || (n1 && n1->startbit < n2->startbit)) {
startbit = n1->startbit;
map = n1->map;
n1 = n1->next;
} else {
startbit = n2->startbit;
map = n2->map;
n2 = n2->next;
}
if (map != 0) {
new = malloc(sizeof(ebitmap_node_t));
if (!new) {
ebitmap_destroy(dst);
return -ENOMEM;
}
new->startbit = startbit;
new->map = map;
new->next = NULL;
if (prev)
prev->next = new;
else
dst->node = new;
prev = new;
}
}
if (prev)
dst->highbit = prev->startbit + MAPSIZE;
return 0;
}