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xo-arena: DArenaHashMap: populate front bookend in control array

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This commit is contained in:
Roland Conybeare 2026-01-08 14:02:44 -05:00
commit ccfc587306
1 changed files with 26 additions and 5 deletions
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31
include/xo/arena/DArenaHashMap.hpp
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@ -70,6 +70,10 @@ namespace xo {
static constexpr uint8_t c_empty_slot = 0xFF;
/** control: tombstone for deleted slot **/
static constexpr uint8_t c_tombstone = 0xFE;
/** control: bookends around control array,
* for iterator edge support
**/
static constexpr uint8_t c_iterator_bookend = 0xF0;
/** group size **/
static constexpr size_type c_group_size = 16;
@ -237,8 +241,13 @@ namespace xo {
void _init() {
this->control_.resize(control_size(n_slot_));
/* all slots marked empty initially */
/* front stub: iterator bookend */
std::fill(this->control_.begin(),
this->control_.begin() + c_control_stub,
c_iterator_bookend);
/* all slots marked empty initially */
std::fill(this->control_.begin() + c_control_stub,
this->control_.end(),
c_empty_slot);
@ -708,8 +717,9 @@ namespace xo {
* SM2. load factor
* - SM2.1 load_factor() <= c_max_load_factor
* SM3. control_
* - SM3.1 control_[N+i] = control_[i] for i in [0, c_group_size)
* - SM3.2 {number of control_[i] spots with non-sentinel values} = size_
* - SM3.1 control_[i] = c_iterator_bookend
* - SM3.2 control_[N+i] = control_[i] for i in [0, c_group_size)
* - SM3.3 {number of control_[i] spots with non-sentinel values} = size_
* SM4. slots_
* - SM4.1 if control_[i] is non-sentinel:
* - SM4.1.1 control_[i] = hash_(slots_[i].first) & 0x7f
@ -788,7 +798,18 @@ namespace xo {
xtag("c_max_load_factor", c_max_load_factor));
}
/* SM3.1: control_[N+i] = control_[i] for i in [0, c_group_size) */
/* SM3.1: control_[i] = c_iterator_bookend for i in [0, c_control_stub) */
for (size_type i = 0; i < c_control_stub; ++i) {
if (store_.control_[i] != c_iterator_bookend) {
return policy.report_error(log,
c_self, ": expect control_[i] = c_iterator_bookend for front stub",
xtag("i", i),
xtag("control_[i]", (int)(store_.control_[i])),
xtag("c_iterator_bookend", (int)c_iterator_bookend));
}
}
/* SM3.2: control_[N+i] = control_[i] for i in [0, c_group_size) */
for (size_type i = 0; i < c_group_size; ++i) {
if (store_.control_[store_.n_slot_ + i + c_control_stub] != store_.control_[i + c_control_stub]) {
return policy.report_error(log,
@ -799,7 +820,7 @@ namespace xo {
}
}
/* SM3.2: {number of control_[i] spots with non-sentinel values} = size_ */
/* SM3.3: {number of control_[i] spots with non-sentinel values} = size_ */
{
size_type occupied_count = 0;
for (size_type i = 0; i < store_.n_slot_; ++i) {