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-rw-r--r--absl/container/internal/raw_hash_set.h138
1 files changed, 71 insertions, 67 deletions
diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index 5fbe56b9..02158c4e 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -513,6 +513,64 @@ inline void AssertIsValid(ctrl_t* ctrl) {
"been erased, or the table might have rehashed.");
}
+struct FindInfo {
+ size_t offset;
+ size_t probe_length;
+};
+
+// The representation of the object has two modes:
+// - small: For capacities < kWidth-1
+// - large: For the rest.
+//
+// Differences:
+// - In small mode we are able to use the whole capacity. The extra control
+// bytes give us at least one "empty" control byte to stop the iteration.
+// This is important to make 1 a valid capacity.
+//
+// - In small mode only the first `capacity()` control bytes after the
+// sentinel are valid. The rest contain dummy kEmpty values that do not
+// represent a real slot. This is important to take into account on
+// find_first_non_full(), where we never try ShouldInsertBackwards() for
+// small tables.
+inline bool is_small(size_t capacity) { return capacity < Group::kWidth - 1; }
+
+inline probe_seq<Group::kWidth> probe(ctrl_t* ctrl, size_t hash,
+ size_t capacity) {
+ return probe_seq<Group::kWidth>(H1(hash, ctrl), capacity);
+}
+
+// Probes the raw_hash_set with the probe sequence for hash and returns the
+// pointer to the first empty or deleted slot.
+// NOTE: this function must work with tables having both kEmpty and kDelete
+// in one group. Such tables appears during drop_deletes_without_resize.
+//
+// This function is very useful when insertions happen and:
+// - the input is already a set
+// - there are enough slots
+// - the element with the hash is not in the table
+inline FindInfo find_first_non_full(ctrl_t* ctrl, size_t hash,
+ size_t capacity) {
+ auto seq = probe(ctrl, hash, capacity);
+ while (true) {
+ Group g{ctrl + seq.offset()};
+ auto mask = g.MatchEmptyOrDeleted();
+ if (mask) {
+#if !defined(NDEBUG)
+ // We want to add entropy even when ASLR is not enabled.
+ // In debug build we will randomly insert in either the front or back of
+ // the group.
+ // TODO(kfm,sbenza): revisit after we do unconditional mixing
+ if (!is_small(capacity) && ShouldInsertBackwards(hash, ctrl)) {
+ return {seq.offset(mask.HighestBitSet()), seq.index()};
+ }
+#endif
+ return {seq.offset(mask.LowestBitSet()), seq.index()};
+ }
+ seq.next();
+ assert(seq.index() < capacity && "full table!");
+ }
+}
+
// Policy: a policy defines how to perform different operations on
// the slots of the hashtable (see hash_policy_traits.h for the full interface
// of policy).
@@ -845,7 +903,7 @@ class raw_hash_set {
// than a full `insert`.
for (const auto& v : that) {
const size_t hash = PolicyTraits::apply(HashElement{hash_ref()}, v);
- auto target = find_first_non_full(hash);
+ auto target = find_first_non_full(ctrl_, hash, capacity_);
set_ctrl(target.offset, H2(hash));
emplace_at(target.offset, v);
infoz_.RecordInsert(hash, target.probe_length);
@@ -1297,7 +1355,7 @@ class raw_hash_set {
void prefetch(const key_arg<K>& key) const {
(void)key;
#if defined(__GNUC__)
- auto seq = probe(hash_ref()(key));
+ auto seq = probe(ctrl_, hash_ref()(key), capacity_);
__builtin_prefetch(static_cast<const void*>(ctrl_ + seq.offset()));
__builtin_prefetch(static_cast<const void*>(slots_ + seq.offset()));
#endif // __GNUC__
@@ -1312,7 +1370,7 @@ class raw_hash_set {
// called heterogeneous key support.
template <class K = key_type>
iterator find(const key_arg<K>& key, size_t hash) {
- auto seq = probe(hash);
+ auto seq = probe(ctrl_, hash, capacity_);
while (true) {
Group g{ctrl_ + seq.offset()};
for (int i : g.Match(H2(hash))) {
@@ -1534,7 +1592,7 @@ class raw_hash_set {
if (IsFull(old_ctrl[i])) {
size_t hash = PolicyTraits::apply(HashElement{hash_ref()},
PolicyTraits::element(old_slots + i));
- auto target = find_first_non_full(hash);
+ auto target = find_first_non_full(ctrl_, hash, capacity_);
size_t new_i = target.offset;
total_probe_length += target.probe_length;
set_ctrl(new_i, H2(hash));
@@ -1553,7 +1611,7 @@ class raw_hash_set {
void drop_deletes_without_resize() ABSL_ATTRIBUTE_NOINLINE {
assert(IsValidCapacity(capacity_));
- assert(!is_small());
+ assert(!is_small(capacity_));
// Algorithm:
// - mark all DELETED slots as EMPTY
// - mark all FULL slots as DELETED
@@ -1578,7 +1636,7 @@ class raw_hash_set {
if (!IsDeleted(ctrl_[i])) continue;
size_t hash = PolicyTraits::apply(HashElement{hash_ref()},
PolicyTraits::element(slots_ + i));
- auto target = find_first_non_full(hash);
+ auto target = find_first_non_full(ctrl_, hash, capacity_);
size_t new_i = target.offset;
total_probe_length += target.probe_length;
@@ -1586,7 +1644,8 @@ class raw_hash_set {
// If they do, we don't need to move the object as it falls already in the
// best probe we can.
const auto probe_index = [&](size_t pos) {
- return ((pos - probe(hash).offset()) & capacity_) / Group::kWidth;
+ return ((pos - probe(ctrl_, hash, capacity_).offset()) & capacity_) /
+ Group::kWidth;
};
// Element doesn't move.
@@ -1630,7 +1689,7 @@ class raw_hash_set {
bool has_element(const value_type& elem) const {
size_t hash = PolicyTraits::apply(HashElement{hash_ref()}, elem);
- auto seq = probe(hash);
+ auto seq = probe(ctrl_, hash, capacity_);
while (true) {
Group g{ctrl_ + seq.offset()};
for (int i : g.Match(H2(hash))) {
@@ -1645,41 +1704,6 @@ class raw_hash_set {
return false;
}
- // Probes the raw_hash_set with the probe sequence for hash and returns the
- // pointer to the first empty or deleted slot.
- // NOTE: this function must work with tables having both kEmpty and kDelete
- // in one group. Such tables appears during drop_deletes_without_resize.
- //
- // This function is very useful when insertions happen and:
- // - the input is already a set
- // - there are enough slots
- // - the element with the hash is not in the table
- struct FindInfo {
- size_t offset;
- size_t probe_length;
- };
- FindInfo find_first_non_full(size_t hash) {
- auto seq = probe(hash);
- while (true) {
- Group g{ctrl_ + seq.offset()};
- auto mask = g.MatchEmptyOrDeleted();
- if (mask) {
-#if !defined(NDEBUG)
- // We want to add entropy even when ASLR is not enabled.
- // In debug build we will randomly insert in either the front or back of
- // the group.
- // TODO(kfm,sbenza): revisit after we do unconditional mixing
- if (!is_small() && ShouldInsertBackwards(hash, ctrl_)) {
- return {seq.offset(mask.HighestBitSet()), seq.index()};
- }
-#endif
- return {seq.offset(mask.LowestBitSet()), seq.index()};
- }
- seq.next();
- assert(seq.index() < capacity_ && "full table!");
- }
- }
-
// TODO(alkis): Optimize this assuming *this and that don't overlap.
raw_hash_set& move_assign(raw_hash_set&& that, std::true_type) {
raw_hash_set tmp(std::move(that));
@@ -1696,7 +1720,7 @@ class raw_hash_set {
template <class K>
std::pair<size_t, bool> find_or_prepare_insert(const K& key) {
auto hash = hash_ref()(key);
- auto seq = probe(hash);
+ auto seq = probe(ctrl_, hash, capacity_);
while (true) {
Group g{ctrl_ + seq.offset()};
for (int i : g.Match(H2(hash))) {
@@ -1713,11 +1737,11 @@ class raw_hash_set {
}
size_t prepare_insert(size_t hash) ABSL_ATTRIBUTE_NOINLINE {
- auto target = find_first_non_full(hash);
+ auto target = find_first_non_full(ctrl_, hash, capacity_);
if (ABSL_PREDICT_FALSE(growth_left() == 0 &&
!IsDeleted(ctrl_[target.offset]))) {
rehash_and_grow_if_necessary();
- target = find_first_non_full(hash);
+ target = find_first_non_full(ctrl_, hash, capacity_);
}
++size_;
growth_left() -= IsEmpty(ctrl_[target.offset]);
@@ -1750,10 +1774,6 @@ class raw_hash_set {
private:
friend struct RawHashSetTestOnlyAccess;
- probe_seq<Group::kWidth> probe(size_t hash) const {
- return probe_seq<Group::kWidth>(H1(hash, ctrl_), capacity_);
- }
-
// Reset all ctrl bytes back to kEmpty, except the sentinel.
void reset_ctrl() {
std::memset(ctrl_, kEmpty, capacity_ + Group::kWidth);
@@ -1783,22 +1803,6 @@ class raw_hash_set {
size_t& growth_left() { return settings_.template get<0>(); }
- // The representation of the object has two modes:
- // - small: For capacities < kWidth-1
- // - large: For the rest.
- //
- // Differences:
- // - In small mode we are able to use the whole capacity. The extra control
- // bytes give us at least one "empty" control byte to stop the iteration.
- // This is important to make 1 a valid capacity.
- //
- // - In small mode only the first `capacity()` control bytes after the
- // sentinel are valid. The rest contain dummy kEmpty values that do not
- // represent a real slot. This is important to take into account on
- // find_first_non_full(), where we never try ShouldInsertBackwards() for
- // small tables.
- bool is_small() const { return capacity_ < Group::kWidth - 1; }
-
hasher& hash_ref() { return settings_.template get<1>(); }
const hasher& hash_ref() const { return settings_.template get<1>(); }
key_equal& eq_ref() { return settings_.template get<2>(); }
@@ -1842,7 +1846,7 @@ struct HashtableDebugAccess<Set, absl::void_t<typename Set::raw_hash_set>> {
const typename Set::key_type& key) {
size_t num_probes = 0;
size_t hash = set.hash_ref()(key);
- auto seq = set.probe(hash);
+ auto seq = probe(set.ctrl_, hash, set.capacity_);
while (true) {
container_internal::Group g{set.ctrl_ + seq.offset()};
for (int i : g.Match(container_internal::H2(hash))) {
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-09 00:07:41 +0000