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/* -*- Mode: C++; tab-width: 13; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=13 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef MOZILLA_CACHE_INVALIDATOR_H_
#define MOZILLA_CACHE_INVALIDATOR_H_
#include "mozilla/Maybe.h"
#include "mozilla/UniquePtr.h"
#include <unordered_map>
#include <unordered_set>
#include <vector>
// -
namespace mozilla {
class AbstractCache;
// -
class CacheInvalidator {
friend class AbstractCache;
private:
mutable std::unordered_set<AbstractCache*> mCaches;
public:
virtual ~CacheInvalidator() {
// It's actually generally unsafe to wait until now to invalidate caches,
// because when used as a mixin, this dtor is called after the dtor for the
// derived class. This means that if the derived class holds a cache (or is
// a cache!), OnInvalidate() will be called on a destroyed object.
// MOZ_ASSERT(!mCaches);
InvalidateCaches();
}
void InvalidateCaches() const;
};
// -
class AbstractCache {
using InvalidatorListT = std::vector<const CacheInvalidator*>;
private:
InvalidatorListT mInvalidators;
public:
AbstractCache() = default;
explicit AbstractCache(InvalidatorListT&& invalidators) {
ResetInvalidators(std::move(invalidators));
}
virtual ~AbstractCache() { ResetInvalidators({}); }
public:
virtual void OnInvalidate() = 0;
void ResetInvalidators(InvalidatorListT&&);
void AddInvalidator(const CacheInvalidator&);
};
// -
template <typename T>
class CacheMaybe : public AbstractCache {
Maybe<T> mVal;
public:
template <typename U>
CacheMaybe& operator=(Maybe<U>&& rhs) {
mVal.reset();
if (rhs) {
mVal.emplace(std::move(rhs.ref()));
}
return *this;
}
CacheMaybe& operator=(Nothing) { return *this = Maybe<T>(); }
void OnInvalidate() override {
*this = Nothing();
ResetInvalidators({});
}
explicit operator bool() const { return bool(mVal); }
T* get() const { return mVal.ptrOr(nullptr); }
T* operator->() const { return get(); }
};
// -
template <typename KeyT, typename ValueT>
class CacheWeakMap final {
class Entry final : public AbstractCache {
public:
CacheWeakMap& mParent;
const KeyT mKey;
const ValueT mValue;
Entry(CacheWeakMap& parent, const KeyT& key, ValueT&& value)
: mParent(parent), mKey(key), mValue(std::move(value)) {}
void OnInvalidate() override {
const auto erased = mParent.mMap.erase(&mKey);
MOZ_ALWAYS_TRUE(erased == 1);
}
};
struct DerefHash final {
size_t operator()(const KeyT* const a) const {
return std::hash<KeyT>()(*a);
}
};
struct DerefEqual final {
bool operator()(const KeyT* const a, const KeyT* const b) const {
return *a == *b;
}
};
using MapT =
std::unordered_map<const KeyT*, UniquePtr<Entry>, DerefHash, DerefEqual>;
MapT mMap;
public:
UniquePtr<Entry> MakeEntry(const KeyT& key, ValueT&& value) {
return UniquePtr<Entry>(new Entry(*this, key, std::move(value)));
}
UniquePtr<Entry> MakeEntry(const KeyT& key, const ValueT& value) {
return MakeEntry(key, ValueT(value));
}
const ValueT* Insert(UniquePtr<Entry>&& entry) {
auto insertable = typename MapT::value_type{&entry->mKey, std::move(entry)};
const auto res = mMap.insert(std::move(insertable));
const auto& didInsert = res.second;
MOZ_ALWAYS_TRUE(didInsert);
const auto& itr = res.first;
return &itr->second->mValue;
}
const ValueT* Find(const KeyT& key) const {
const auto itr = mMap.find(&key);
if (itr == mMap.end()) return nullptr;
return &itr->second->mValue;
}
void Clear() const {
while (true) {
const auto itr = mMap.begin();
if (itr == mMap.end()) return;
itr->second->OnInvalidate();
}
}
~CacheWeakMap() { Clear(); }
};
} // namespace mozilla
#endif // MOZILLA_CACHE_INVALIDATOR_H_
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