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simplify code by removing return values where possible

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fix_iterator() and related functions are quite difficult to read.
perhaps it would be a little clearer if we didn't assign values
to variables that won't subsequently be used, or unnecessarily
pop the stack and then push the same value back onto it.

also, in dns_qp_lookup() we previously called fix_iterator(),
removed the leaf from the top of the iterator stack, and then
added it back on. this would be clearer if we just push the leaf
onto the stack when we need to, but leave the stack alone when
it's already complete.
This commit is contained in:
Evan Hunt
2024-04-19 15:57:32 -07:00
parent b1b1ca8ca4
commit 237123e500
1 changed files with 36 additions and 39 deletions
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75
lib/dns/qp.c
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@@ -2028,17 +2028,16 @@ add_link(dns_qpchain_t *chain, dns_qpnode_t *node, size_t offset) {
INSIST(chain->len <= DNS_NAME_MAXLABELS);
}
static inline dns_qpnode_t *
static inline void
prevleaf(dns_qpiter_t *it) {
isc_result_t result = dns_qpiter_prev(it, NULL, NULL, NULL);
if (result == ISC_R_NOMORE) {
result = dns_qpiter_prev(it, NULL, NULL, NULL);
}
RUNTIME_CHECK(result == ISC_R_SUCCESS);
return (it->stack[it->sp]);
}
static inline dns_qpnode_t *
static inline void
greatest_leaf(dns_qpreadable_t qpr, dns_qpnode_t *n, dns_qpiter_t *iter) {
while (is_branch(n)) {
dns_qpref_t ref = branch_twigs_ref(n) + branch_twigs_size(n) -
@@ -2047,7 +2046,6 @@ greatest_leaf(dns_qpreadable_t qpr, dns_qpnode_t *n, dns_qpiter_t *iter) {
n = ref_ptr(qpr, ref);
}
iter->stack[++iter->sp] = n;
return (n);
}
static inline dns_qpnode_t *
@@ -2099,18 +2097,16 @@ anyleaf(dns_qpreader_t *qp, dns_qpnode_t *n) {
* the parent branch. We can use the qpiter stack to step back one leaf to
* the predecessor.
*/
static dns_qpnode_t *
static void
fix_iterator(dns_qpreader_t *qp, dns_qpiter_t *iter, dns_qpkey_t search,
size_t searchlen, dns_qpshift_t bit, size_t offset) {
dns_qpkey_t found;
size_t foundlen, to;
dns_qpnode_t *n = iter->stack[iter->sp];
dns_qpnode_t *leaf = anyleaf(qp, n);
size_t foundlen = leaf_qpkey(qp, anyleaf(qp, n), found);
size_t to = qpkey_compare(search, searchlen, found, foundlen);
foundlen = leaf_qpkey(qp, leaf, found);
to = qpkey_compare(search, searchlen, found, foundlen);
if (to == QPKEY_EQUAL) {
return (leaf);
return;
}
/*
@@ -2122,7 +2118,8 @@ fix_iterator(dns_qpreader_t *qp, dns_qpiter_t *iter, dns_qpkey_t search,
*/
if (to < branch_key_offset(iter->stack[0])) {
dns_qpiter_init(qp, iter);
return (prevleaf(iter));
prevleaf(iter);
return;
}
/*
@@ -2145,11 +2142,12 @@ fix_iterator(dns_qpreader_t *qp, dns_qpiter_t *iter, dns_qpkey_t search,
* This was the first domain; move the iterator
* one step back from the origin and return.
*/
return (prevleaf(iter));
prevleaf(iter);
return;
}
RUNTIME_CHECK(result == ISC_R_SUCCESS);
n = iter->stack[iter->sp];
leaf = n;
} else {
if (to <= searchlen && to <= foundlen && iter->sp > 0) {
/*
@@ -2170,13 +2168,13 @@ fix_iterator(dns_qpreader_t *qp, dns_qpiter_t *iter, dns_qpkey_t search,
if (is_branch(n)) {
iter->stack[iter->sp--] = NULL;
n = greatest_leaf(qp, n, iter);
greatest_leaf(qp, n, iter);
}
return (n);
return;
}
foundlen = leaf_qpkey(qp, leaf, found);
foundlen = leaf_qpkey(qp, n, found);
size_t nto = qpkey_compare(search, searchlen, found, foundlen);
if (nto < to) {
/*
@@ -2184,7 +2182,7 @@ fix_iterator(dns_qpreader_t *qp, dns_qpiter_t *iter, dns_qpkey_t search,
* even earlier point, so no further improvement is
* possible.
*/
return (leaf);
return;
}
to = nto;
}
@@ -2203,32 +2201,29 @@ fix_iterator(dns_qpreader_t *qp, dns_qpiter_t *iter, dns_qpkey_t search,
* wanted; use the iterator to walk back to the
* predecessor.
*/
n = prevleaf(iter);
prevleaf(iter);
} else {
/*
* The name we want would've been after some twig in
* this branch. point n to that twig, then walk down
* to the highest leaf in that subtree to get
* the predecessor.
* this branch. walk down from that twig to the
* highest leaf in that subtree to get the predecessor.
*/
n = greatest_leaf(qp, twigs + pos - 1, iter);
greatest_leaf(qp, twigs + pos - 1, iter);
}
} else {
/*
* We're on the right leaf, either the iterator already points
* to the rightful predecessor, or it points to an immediate
* successor. If the latter, we can now use the qpiter stack
* we've constructed to step back to the predecessor. Otherwise,
* we don't have to do anything anymore.
* We're on the right leaf, so either the iterator already
* points to the rightful predecessor, or it points to an
* immediate successor. If the latter, we can now use the
* qpiter stack we've constructed to step back to the
* predecessor. Otherwise, we don't have to do anything
* anymore.
*/
if (to <= searchlen && to <= foundlen && search[to] < found[to])
{
n = prevleaf(iter);
prevleaf(iter);
}
}
return (n);
}
isc_result_t
@@ -2310,6 +2305,7 @@ dns_qp_lookup(dns_qpreadable_t qpr, const dns_name_t *name,
* the loop.
*/
n = branch_twig_ptr(qp, n, bit);
iter->stack[++iter->sp] = n;
} else if (setiter) {
/*
* this branch is a dead end. however, the caller
@@ -2317,9 +2313,8 @@ dns_qp_lookup(dns_qpreadable_t qpr, const dns_name_t *name,
* for the predecessor of the searched-for-name;
* that will break the loop.
*/
n = fix_iterator(qp, iter, search, searchlen, bit,
offset);
iter->stack[iter->sp--] = NULL;
fix_iterator(qp, iter, search, searchlen, bit, offset);
n = iter->stack[iter->sp];
} else {
/*
* this branch is a dead end, and the predecessor
@@ -2333,9 +2328,8 @@ dns_qp_lookup(dns_qpreadable_t qpr, const dns_name_t *name,
/* walk down to find the leftmost leaf */
n = anyleaf(qp, twigs);
}
iter->stack[++iter->sp] = n;
}
iter->stack[++iter->sp] = n;
}
if (matched && setiter) {
@@ -2345,10 +2339,13 @@ dns_qp_lookup(dns_qpreadable_t qpr, const dns_name_t *name,
* and if the caller passed us an iterator,
* then we might need to reposition it.
*/
n = fix_iterator(qp, iter, search, searchlen, bit, offset);
fix_iterator(qp, iter, search, searchlen, bit, offset);
n = iter->stack[iter->sp];
}
/* do the keys differ, and if so, where? */
/* at this point, n can only be a leaf node */
INSIST(!is_branch(n));
foundlen = leaf_qpkey(qp, n, found);
offset = qpkey_compare(search, searchlen, found, foundlen);