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AK+Kernel: OOM-harden most parts of Trie

The only part of Unveil that can't handle OOM gracefully is the
String::formatted() use in the node metadata.
This commit is contained in:
Ali Mohammad Pur 2022-02-14 16:49:53 +03:30 committed by Idan Horowitz
parent 80e6198563
commit a1cb2c371a
9 changed files with 145 additions and 99 deletions

171
AK/Trie.h
View file

@ -6,6 +6,7 @@
#pragma once
#include <AK/Concepts.h>
#include <AK/Forward.h>
#include <AK/HashMap.h>
#include <AK/OwnPtr.h>
@ -29,62 +30,6 @@ template<typename DeclaredBaseType, typename DefaultBaseType, typename ValueType
class Trie {
using BaseType = typename SubstituteIfVoid<DeclaredBaseType, DefaultBaseType>::Type;
class ConstIterator {
public:
static ConstIterator end() { return {}; }
bool operator==(const ConstIterator& other) const { return m_current_node == other.m_current_node; }
const BaseType& operator*() const { return static_cast<const BaseType&>(*m_current_node); }
const BaseType* operator->() const { return static_cast<const BaseType*>(m_current_node); }
void operator++() { skip_to_next(); }
explicit ConstIterator(const Trie& node)
{
m_current_node = &node;
// FIXME: Figure out how to OOM harden this iterator.
MUST(m_state.try_empend(false, node.m_children.begin(), node.m_children.end()));
}
private:
void skip_to_next()
{
auto& current_state = m_state.last();
if (current_state.did_generate_root)
++current_state.it;
else
current_state.did_generate_root = true;
if (current_state.it == current_state.end)
return pop_and_get_next();
m_current_node = &*(*current_state.it).value;
// FIXME: Figure out how to OOM harden this iterator.
MUST(m_state.try_empend(false, m_current_node->m_children.begin(), m_current_node->m_children.end()));
}
void pop_and_get_next()
{
m_state.take_last();
if (m_state.is_empty()) {
m_current_node = nullptr;
return;
}
skip_to_next();
}
ConstIterator() = default;
struct State {
bool did_generate_root { false };
typename HashMap<ValueType, NonnullOwnPtr<Trie>, ValueTraits>::ConstIteratorType it;
typename HashMap<ValueType, NonnullOwnPtr<Trie>, ValueTraits>::ConstIteratorType end;
};
Vector<State> m_state;
const Trie* m_current_node { nullptr };
};
public:
using MetadataType = MetadataT;
@ -127,48 +72,56 @@ public:
Optional<MetadataType> metadata() const requires(!IsNullPointer<MetadataType>) { return m_metadata; }
void set_metadata(MetadataType metadata) requires(!IsNullPointer<MetadataType>) { m_metadata = move(metadata); }
const MetadataType& metadata_value() const requires(!IsNullPointer<MetadataType>) { return m_metadata.value(); }
MetadataType& metadata_value() requires(!IsNullPointer<MetadataType>) { return m_metadata.value(); }
const ValueType& value() const { return m_value; }
ValueType& value() { return m_value; }
Trie& ensure_child(ValueType value, Optional<MetadataType> metadata = {})
ErrorOr<Trie*> ensure_child(ValueType value, Optional<MetadataType> metadata = {})
{
auto it = m_children.find(value);
if (it == m_children.end()) {
auto node = adopt_nonnull_own_or_enomem(new (nothrow) Trie(value, move(metadata))).release_value_but_fixme_should_propagate_errors();
auto node = TRY(adopt_nonnull_own_or_enomem(new (nothrow) Trie(value, move(metadata))));
auto& node_ref = *node;
m_children.set(move(value), move(node));
return static_cast<BaseType&>(node_ref);
TRY(m_children.try_set(move(value), move(node)));
return &static_cast<BaseType&>(node_ref);
}
auto& node_ref = *it->value;
if (metadata.has_value())
node_ref.m_metadata = move(metadata);
return static_cast<BaseType&>(node_ref);
return &static_cast<BaseType&>(node_ref);
}
template<typename It, typename ProvideMetadataFunction>
BaseType& insert(
ErrorOr<BaseType*> insert(
It& it, const It& end, MetadataType metadata, ProvideMetadataFunction provide_missing_metadata) requires(!IsNullPointer<MetadataType>)
{
Trie* last_root_node = &traverse_until_last_accessible_node(it, end);
auto invoke_provide_missing_metadata = [&]<typename... Ts>(Ts && ... args)->ErrorOr<Optional<MetadataType>>
{
if constexpr (SameAs<MetadataType, decltype(provide_missing_metadata(forward<Ts>(args)...))>)
return Optional<MetadataType>(provide_missing_metadata(forward<Ts>(args)...));
else
return provide_missing_metadata(forward<Ts>(args)...);
};
for (; it != end; ++it)
last_root_node = static_cast<Trie*>(&last_root_node->ensure_child(*it, provide_missing_metadata(static_cast<BaseType&>(*last_root_node), it)));
last_root_node = static_cast<Trie*>(TRY(last_root_node->ensure_child(*it, TRY(invoke_provide_missing_metadata(static_cast<BaseType&>(*last_root_node), it)))));
last_root_node->set_metadata(move(metadata));
return static_cast<BaseType&>(*last_root_node);
return static_cast<BaseType*>(last_root_node);
}
template<typename It>
BaseType& insert(It& it, const It& end) requires(IsNullPointer<MetadataType>)
ErrorOr<BaseType*> insert(It& it, const It& end) requires(IsNullPointer<MetadataType>)
{
Trie* last_root_node = &traverse_until_last_accessible_node(it, end);
for (; it != end; ++it)
last_root_node = static_cast<Trie*>(&last_root_node->ensure_child(*it, {}));
return static_cast<BaseType&>(*last_root_node);
last_root_node = static_cast<Trie*>(TRY(last_root_node->ensure_child(*it, {})));
return static_cast<BaseType*>(last_root_node);
}
template<typename It, typename ProvideMetadataFunction>
BaseType& insert(
ErrorOr<BaseType*> insert(
const It& begin, const It& end, MetadataType metadata, ProvideMetadataFunction provide_missing_metadata) requires(!IsNullPointer<MetadataType>)
{
auto it = begin;
@ -176,7 +129,7 @@ public:
}
template<typename It>
BaseType& insert(const It& begin, const It& end) requires(IsNullPointer<MetadataType>)
ErrorOr<BaseType*> insert(const It& begin, const It& end) requires(IsNullPointer<MetadataType>)
{
auto it = begin;
return insert(it, end);
@ -185,21 +138,91 @@ public:
HashMap<ValueType, NonnullOwnPtr<Trie>, ValueTraits>& children() { return m_children; }
HashMap<ValueType, NonnullOwnPtr<Trie>, ValueTraits> const& children() const { return m_children; }
ConstIterator begin() const { return ConstIterator(*this); }
ConstIterator end() const { return ConstIterator::end(); }
template<typename Fn>
ErrorOr<void> for_each_node_in_tree_order(Fn callback) const
{
struct State {
bool did_generate_root { false };
typename HashMap<ValueType, NonnullOwnPtr<Trie>, ValueTraits>::ConstIteratorType it;
typename HashMap<ValueType, NonnullOwnPtr<Trie>, ValueTraits>::ConstIteratorType end;
};
Vector<State> state;
TRY(state.try_empend(false, m_children.begin(), m_children.end()));
auto invoke = [&](auto& current_node) -> ErrorOr<IterationDecision> {
if constexpr (VoidFunction<Fn, const BaseType&>) {
callback(static_cast<const BaseType&>(current_node));
return IterationDecision::Continue;
} else if constexpr (IsSpecializationOf<decltype(callback(declval<const BaseType&>())), ErrorOr>) {
return callback(static_cast<const BaseType&>(current_node));
} else if constexpr (IteratorFunction<Fn, const BaseType&>) {
return callback(static_cast<const BaseType&>(current_node));
} else {
static_assert(DependentFalse<Fn>, "Invalid iterator function type signature");
}
return IterationDecision::Continue;
};
for (auto* current_node = this; current_node != nullptr;) {
if (TRY(invoke(*current_node)) == IterationDecision::Break)
break;
TRY(skip_to_next_iterator(state, current_node));
}
return {};
}
[[nodiscard]] bool is_empty() const { return m_children.is_empty(); }
void clear() { m_children.clear(); }
BaseType deep_copy()
ErrorOr<BaseType> deep_copy()
{
Trie root(m_value, m_metadata);
Trie root(m_value, TRY(copy_metadata(m_metadata)));
for (auto& it : m_children)
root.m_children.set(it.key, adopt_nonnull_own_or_enomem(new (nothrow) Trie(it.value->deep_copy())).release_value_but_fixme_should_propagate_errors());
TRY(root.m_children.try_set(it.key, TRY(adopt_nonnull_own_or_enomem(new (nothrow) Trie(TRY(it.value->deep_copy()))))));
return static_cast<BaseType&&>(move(root));
}
private:
static ErrorOr<Optional<MetadataType>> copy_metadata(Optional<MetadataType> const& metadata)
{
if (!metadata.has_value())
return Optional<MetadataType> {};
if constexpr (requires(MetadataType t) { { t.copy() } -> SpecializationOf<ErrorOr>; })
return Optional<MetadataType> { TRY(metadata->copy()) };
#ifndef KERNEL
else
return Optional<MetadataType> { MetadataType(metadata.value()) };
#endif
}
static ErrorOr<void> skip_to_next_iterator(auto& state, auto& current_node)
{
auto& current_state = state.last();
if (current_state.did_generate_root)
++current_state.it;
else
current_state.did_generate_root = true;
if (current_state.it == current_state.end)
return pop_and_get_next_iterator(state, current_node);
current_node = &*(*current_state.it).value;
TRY(state.try_empend(false, current_node->m_children.begin(), current_node->m_children.end()));
return {};
}
static ErrorOr<void> pop_and_get_next_iterator(auto& state, auto& current_node)
{
state.take_last();
if (state.is_empty()) {
current_node = nullptr;
return {};
}
return skip_to_next_iterator(state, current_node);
}
ValueType m_value;
Optional<MetadataType> m_metadata;
HashMap<ValueType, NonnullOwnPtr<Trie>, ValueTraits> m_children;