Dear DPDK users,
I have been reading and studying the source codes of the librte_acl, since I am
very curious to know how to algorithmically implement a fast lookup process.
When I read the function acl_add_ptrs() in the acl_gen.c, there is one comment
saying that
/*
* Rather than going from 0 to 256, the range count and
* the layout are from 80-ff then 0-7f due to signed compare
* for SSE (cmpgt).
*/
However, in the following codes, it is
for (x = QRANGE_MIN + 1; x < UINT8_MAX + 1; x++) {
if (dfa[x] != index) {
index = dfa[x];
*node_a++ = index;
node->transitions[m++] = (uint8_t)(x - 1);
}
}
for (x = 0; x < INT8_MAX + 1; x++) {
if (dfa[x] != index) {
index = dfa[x];
*node_a++ = index;
node->transitions[m++] = (uint8_t)(x - 1);
}
}
As you can see that there are two for-loops, and the second for-loop include
the first for-loop. And, this is not consistent with the comment. If the
comment is followed, in the second for-loop, it should be "for (x = 0; x <
QRANGE_MIN + 1; x++)", if we assume QRANGE_MIN is ff?
Moreover, due to that the first for-loop is included in the second for-loop and
the "m" variable is increased by 1 whenever the if-statement is true, I am
thinking about a case in which during the first for-loop, the "m" is increased
by 3, hence after the second for-loop, the "m" is at least 6, this will finally
break the check RTE_ACL_VERIFY(m <= RTE_ACL_QUAD_SIZE) in the following code,
since RTE_ACL_QUAD_SIZE is 4. I am wondering if this case will ever happen?
Am I missing something here? Thanks very much for your help.
Best wishes,
Xiaoban
