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xo-arena: DArenaHashMap: find() + utest

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This commit is contained in:
Roland Conybeare 2026-01-08 17:04:07 -05:00
commit 5be04f5ed2
3 changed files with 75 additions and 18 deletions
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58
include/xo/arena/DArenaHashMap.hpp
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@ -457,6 +457,11 @@ namespace xo {
/** reset to empty state **/
void clear();
/** find element with key @p key.
* @return iterator to element if found, end() otherwise
**/
iterator find(const key_type & key);
private:
/** insert @p kv_pair,
* where key hashes to @p hash_value, into @p *store
@ -745,6 +750,59 @@ namespace xo {
this->store_.clear();
}
template <typename Key,
typename Value,
typename Hash,
typename Equal>
auto
DArenaHashMap<Key, Value, Hash, Equal>::find(const key_type & key) -> iterator
{
size_type N = store_.capacity();
if (N == 0) [[unlikely]] {
return this->end();
}
size_type h = hash_(key);
size_type h1 = h >> 7;
uint8_t h2 = h & 0x7f;
size_type ix = h1 & (N - 1);
for (;;) {
auto grp = store_._load_group(ix);
{
uint16_t m = grp.all_matches(h2);
while (m) {
int skip = __builtin_ctz(m);
size_type slot_ix = (ix + skip) & (N - 1);
auto & slot = store_.slots_[slot_ix];
if (equal_(slot.first, key)) {
return iterator(&(store_.control_[c_control_stub + slot_ix]),
&(store_.control_[c_control_stub + N]),
&slot);
}
m &= (m - 1);
}
}
{
uint16_t e = grp.empty_matches();
if (e) {
return this->end();
}
}
ix = (ix + c_group_size) & (N - 1);
}
}
/**
* Verify DArenaHashMap class invariants.
*