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Use iterative solution instead of tail recursion to avoid stack problems when optimization is off

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This commit is contained in:
dmiller 2018-11-08 04:25:12 +00:00
parent 4620cc3df0
commit 1345eb247b
1 changed files with 55 additions and 57 deletions
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112
nbase/nbase_addrset.c
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@ -389,58 +389,58 @@ static void trie_split (struct trie_node *this, const u32 *addr)
}
}
/* Tail-recursive helper for address insertion */
/* Helper for address insertion */
static void _trie_insert (struct trie_node *this, const u32 *addr, const u32 *mask)
{
if (this == NULL || this == TRIE_NODE_TRUE) {
/* Anything below this point always matches; no need to insert */
return;
}
if (addr_matches(this->mask, this->addr, addr)) {
if (1 & this->mask[3]) {
/* 1. end of address: duplicate. return; */
return;
}
}
else {
/* Split the netmask to ensure a match */
trie_split(this, addr);
}
for (size_t i=0; i < 4; i++) {
if (this->mask[i] > mask[i]) {
/* broader mask, truncate this one */
this->mask[i] = mask[i];
for (; i < 4; i++) {
this->mask[i] = 0;
while (this != NULL && this != TRIE_NODE_TRUE) {
if (addr_matches(this->mask, this->addr, addr)) {
if (1 & this->mask[3]) {
/* 1. end of address: duplicate. return; */
return;
}
/* The longer mask is superseded. Delete following nodes. */
trie_free(this->next_bit_one);
trie_free(this->next_bit_zero);
/* Anything below here will always match. */
this->next_bit_one = this->next_bit_zero = TRIE_NODE_TRUE;
return;
}
}
else {
/* Split the netmask to ensure a match */
trie_split(this, addr);
}
if (addr_next_bit_is_one(this->mask, addr)) {
/* next bit is one: insert on the one branch */
if (this->next_bit_one == NULL) {
/* Previously unmatching branch, always the case when splitting */
this->next_bit_one = new_trie_node(addr, mask);
for (size_t i=0; i < 4; i++) {
if (this->mask[i] > mask[i]) {
/* broader mask, truncate this one */
this->mask[i] = mask[i];
for (; i < 4; i++) {
this->mask[i] = 0;
}
/* The longer mask is superseded. Delete following nodes. */
trie_free(this->next_bit_one);
trie_free(this->next_bit_zero);
/* Anything below here will always match. */
this->next_bit_one = this->next_bit_zero = TRIE_NODE_TRUE;
return;
}
}
if (addr_next_bit_is_one(this->mask, addr)) {
/* next bit is one: insert on the one branch */
if (this->next_bit_one == NULL) {
/* Previously unmatching branch, always the case when splitting */
this->next_bit_one = new_trie_node(addr, mask);
return;
}
else {
this = this->next_bit_one;
}
}
else {
return _trie_insert(this->next_bit_one, addr, mask);
}
}
else {
/* next bit is zero: insert on the zero branch */
if (this->next_bit_zero == NULL) {
/* Previously unmatching branch, always the case when splitting */
this->next_bit_zero = new_trie_node(addr, mask);
}
else {
return _trie_insert(this->next_bit_zero, addr, mask);
/* next bit is zero: insert on the zero branch */
if (this->next_bit_zero == NULL) {
/* Previously unmatching branch, always the case when splitting */
this->next_bit_zero = new_trie_node(addr, mask);
return;
}
else {
this = this->next_bit_zero;
}
}
}
}
@ -520,7 +520,7 @@ static void trie_insert (struct trie_node *this, const struct sockaddr *sa, int
this->next_bit_one = new_trie_node(addr, mask);
return;
}
return _trie_insert(this->next_bit_one, addr, mask);
_trie_insert(this->next_bit_one, addr, mask);
}
else {
/* First bit is 0, so insert on zeros branch */
@ -529,31 +529,29 @@ static void trie_insert (struct trie_node *this, const struct sockaddr *sa, int
this->next_bit_zero = new_trie_node(addr, mask);
return;
}
return _trie_insert(this->next_bit_zero, addr, mask);
_trie_insert(this->next_bit_zero, addr, mask);
}
}
/* Tail-recursive helper for matching addresses */
/* Helper for matching addresses */
static int _trie_match (const struct trie_node *this, const u32 *addr)
{
if (this == TRIE_NODE_TRUE) {
return 1;
}
if (this == NULL) {
return 0;
}
if (addr_matches(this->mask, this->addr, addr)) {
while (this != TRIE_NODE_TRUE && this != NULL
&& addr_matches(this->mask, this->addr, addr)) {
if (1 & this->mask[3]) {
/* We've matched all possible bits! Yay! */
return 1;
}
else if (addr_next_bit_is_one(this->mask, addr)) {
return _trie_match(this->next_bit_one, addr);
this = this->next_bit_one;
}
else {
return _trie_match(this->next_bit_zero, addr);
this = this->next_bit_zero;
}
}
if (this == TRIE_NODE_TRUE) {
return 1;
}
return 0;
}