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LibJS: Fix Map Iterators when elements are deleted during iteration

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Before this would assume that the element found in operator++ was still
valid when dereferencing it in operator*.
Since any code can have been run since that increment this is not always
valid.
To further simplify the logic of the iterator we no longer store the
index in an optional.
This commit is contained in:
davidot 2022-02-10 11:13:53 +01:00 • committed by Linus Groh
parent fdbfe85a87
commit 45646eee43
7 changed files with 302 additions and 20 deletions
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41
Userland/Libraries/LibJS/Runtime/Map.h
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@ -38,32 +38,26 @@ public:
struct IteratorImpl {
bool is_end() const
{
if (m_index.has_value()) {
return m_map.m_keys.begin_from(*m_index).is_end()
&& m_map.m_keys.find_smallest_not_below_iterator(*m_index).is_end();
}
// First attempt and no iteration, ask the map if it has anything.
return m_map.m_keys.is_empty();
return m_map.m_keys.begin_from(m_index).is_end()
&& m_map.m_keys.find_smallest_not_below_iterator(m_index).is_end();
}
IteratorImpl& operator++()
{
if (auto it = m_map.m_keys.find_smallest_not_below_iterator(ensure_index() + 1); it.is_end())
m_index = m_map.m_next_insertion_id;
else
m_index = it.key();
++m_index;
return *this;
}
decltype(auto) operator*()
{
return *m_map.m_entries.find(*m_map.m_keys.begin_from(ensure_index()));
ensure_next_element();
return *m_map.m_entries.find(*m_map.m_keys.begin_from(m_index));
}
decltype(auto) operator*() const
{
return *m_map.m_entries.find(*m_map.m_keys.begin_from(ensure_index()));
ensure_next_element();
return *m_map.m_entries.find(*m_map.m_keys.begin_from(m_index));
}
bool operator==(IteratorImpl const& other) const { return m_index == other.m_index && &m_map == &other.m_map; }
@ -74,24 +68,33 @@ public:
IteratorImpl(Map const& map) requires(IsConst)
: m_map(map)
{
ensure_index();
}
IteratorImpl(Map& map) requires(!IsConst)
: m_map(map)
{
ensure_index();
}
size_t ensure_index()
void ensure_index() const
{
if (!m_index.has_value()) {
VERIFY(!m_map.m_keys.is_empty());
if (m_map.m_keys.is_empty())
m_index = m_map.m_next_insertion_id;
else
m_index = m_map.m_keys.begin().key();
}
return *m_index;
}
void ensure_next_element() const
{
if (auto it = m_map.m_keys.find_smallest_not_below_iterator(m_index); it.is_end())
m_index = m_map.m_next_insertion_id;
else
m_index = it.key();
}
Conditional<IsConst, Map const&, Map&> m_map;
mutable Optional<size_t> m_index;
mutable size_t m_index { 0 };
};
using Iterator = IteratorImpl<false>;