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xo-arena: DArenaHashMap: provide for stub areas on control array

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This commit is contained in:
Roland Conybeare 2026-01-08 13:11:18 -05:00
commit 2273096b48
1 changed files with 39 additions and 23 deletions
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62
include/xo/arena/DArenaHashMap.hpp
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@ -77,6 +77,11 @@ namespace xo {
/** max load factor **/
static constexpr float c_max_load_factor = 0.875;
/** Iterator sentinel at begin/end of control array.
* Load-bearing for bidirectional iterator implementation
**/
static constexpr size_type c_control_stub = 0; //c_group_size;
/** control: true for sentinel values **/
static constexpr bool is_sentinel(control_type ctrl) {
return ctrl & c_sentinel_mask;
@ -87,6 +92,11 @@ namespace xo {
return 0 == (ctrl & c_sentinel_mask);
}
/** control: compute size of control array for swiss hash map with @p n_slot cells **/
static constexpr size_type control_size(size_type n_slot) {
return n_slot + c_group_size + 12 * c_control_stub;
}
/** find smallest multiple k : k * c_group_size >= n **/
static size_type lub_group_mult(size_t n) {
return (n + c_group_size - 1) / c_group_size;
@ -235,18 +245,22 @@ namespace xo {
this->slots_.resize(n_slot_);
}
/** load control group for slot range [ix .. ix+c_group_size) **/
group_type _load_group(size_type ix) {
return group_type(&(control_[ix]));
return group_type(&(control_[ix + c_control_stub]));
}
/** update control group for slot number @p ix, replace with @p h2 **/
void _update_control(size_type ix, uint8_t h2) {
this->control_[ix] = h2;
this->control_[ix + c_control_stub] = h2;
if (ix < c_group_size) {
size_type N = this->capacity();
// refresh end-of-array copy
std::memcpy(&(control_[N]), &(control_[0]), c_group_size);
std::memcpy(&(control_[N + c_control_stub]),
&(control_[c_control_stub]),
c_group_size);
}
}
@ -354,8 +368,8 @@ namespace xo {
bool verify_ok(verify_policy p = verify_policy::throw_only()) const;
iterator begin() {
iterator ix(&(store_.control_[0]),
&(store_.control_[store_.capacity()]),
iterator ix(&(store_.control_[c_control_stub]),
&(store_.control_[c_control_stub + store_.capacity()]),
&(store_.slots_[0]));
if (ix.is_sentinel()) {
@ -367,8 +381,8 @@ namespace xo {
}
iterator end() {
iterator ix(&(store_.control_[store_.capacity()]),
&(store_.control_[store_.capacity()]),
iterator ix(&(store_.control_[c_control_stub + store_.capacity()]),
&(store_.control_[c_control_stub + store_.capacity()]),
&(store_.slots_[store_.capacity()]));
return ix;
@ -614,7 +628,7 @@ namespace xo {
*/
for (size_type i = 0, n = store_.capacity(); i < n; ++i) {
uint8_t ctrl = store_.control_[i];
uint8_t ctrl = store_.control_[c_control_stub + i];
value_type & kv_pair = store_.slots_[i];
if (DArenaHashMapUtil::is_data(ctrl)) {
@ -726,12 +740,14 @@ namespace xo {
}
/* SM1.2: control_[] size consistent with slots_[] size */
if (store_.control_.size() != store_.n_slot_ + c_group_size) {
return policy.report_error(log,
c_self, ": expect .control_.size = .n_slot + c_group_size",
xtag("control_.size", store_.control_.size()),
xtag("n_slot", store_.n_slot_),
xtag("c_group_size", c_group_size));
if (store_.control_.size() != control_size(store_.n_slot_)) {
return policy.report_error
(log,
c_self, ": expect .control_.size = .n_slot + c_group_size + 2 * c_control_stub",
xtag("control_.size", store_.control_.size()),
xtag("n_slot", store_.n_slot_),
xtag("c_group_size", c_group_size),
xtag("c_control_stub", c_control_stub));
}
if (store_.slots_.size() != store_.n_slot_) {
return policy.report_error(log,
@ -774,7 +790,7 @@ namespace xo {
/* SM3.1: 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] != store_.control_[i]) {
if (store_.control_[store_.n_slot_ + i + c_control_stub] != store_.control_[i] + c_control_stub) {
return policy.report_error(log,
c_self, ": expect control_[N+i] = control_[i]",
xtag("i", i),
@ -787,7 +803,7 @@ namespace xo {
{
size_type occupied_count = 0;
for (size_type i = 0; i < store_.n_slot_; ++i) {
uint8_t c = store_.control_[i];
uint8_t c = store_.control_[i + c_control_stub];
if (DArenaHashMapUtil::is_data(c)) {
++occupied_count;
}
@ -802,14 +818,14 @@ namespace xo {
/* SM4.1.1: if control_[i] is non-sentinel, control_[i] = hash_(slots_[i].first) & 0x7f */
for (size_type i = 0; i < store_.n_slot_; ++i) {
uint8_t c = store_.control_[i];
uint8_t c = store_.control_[i + c_control_stub];
if (DArenaHashMapUtil::is_data(c)) {
uint8_t expected_h2 = hash_(store_.slots_[i].first) & 0x7f;
if (c != expected_h2) {
return policy.report_error(log,
c_self, ": expect control[i] = hash(key) & 0x7f",
xtag("i", i),
xtag("control[i]", c),
xtag("control[i+stub]", c),
xtag("expected_h2", expected_h2));
}
}
@ -819,19 +835,19 @@ namespace xo {
* where h = (hash_(slots_[i].first) >> 7) & (n_slot_ - 1)
*/
for (size_type i = 0; i < store_.n_slot_; ++i) {
uint8_t c = store_.control_[i];
uint8_t c = store_.control_[i + c_control_stub];
if (DArenaHashMapUtil::is_data(c)) {
size_type h = (hash_(store_.slots_[i].first) >> 7) & (store_.n_slot_ - 1);
size_type j = h;
while (j != i) {
uint8_t cj = store_.control_[j];
uint8_t cj = store_.control_[j + c_control_stub];
if (DArenaHashMapUtil::is_sentinel(cj)) {
return policy.report_error(log,
c_self, ": expect non-empty slot in probe range [h..i]",
xtag("i", i),
xtag("h", h),
xtag("j", j),
xtag("control[j]", cj));
xtag("control[j+stub]", cj));
}
j = (j + 1) & (store_.n_slot_ - 1);
}
@ -840,13 +856,13 @@ namespace xo {
/* SM4.2: if control_[i] is empty or tombstone, slots_[i].first = key_type() */
for (size_type i = 0; i < store_.n_slot_; ++i) {
uint8_t c = store_.control_[i];
uint8_t c = store_.control_[i + c_control_stub];
if (DArenaHashMapUtil::is_sentinel(c)) {
if (!(store_.slots_[i].first == key_type())) {
return policy.report_error(log,
c_self, ": expect empty/tombstone slot has default key",
xtag("i", i),
xtag("control[i]", c));
xtag("control[i+stub]", c));
}
}
}