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/* 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_SimpleMap_h
#define mozilla_SimpleMap_h
#include <utility>
#include "mozilla/Maybe.h"
#include "mozilla/Mutex.h"
#include "nsTArray.h"
namespace mozilla {
struct ThreadSafePolicy {
struct PolicyLock {
explicit PolicyLock(const char* aName) : mMutex(aName) {}
Mutex mMutex MOZ_UNANNOTATED;
};
PolicyLock& mPolicyLock;
explicit ThreadSafePolicy(PolicyLock& aPolicyLock)
: mPolicyLock(aPolicyLock) {
mPolicyLock.mMutex.Lock();
}
~ThreadSafePolicy() { mPolicyLock.mMutex.Unlock(); }
};
struct NoOpPolicy {
struct PolicyLock {
explicit PolicyLock(const char*) {}
};
explicit NoOpPolicy(PolicyLock&) {}
~NoOpPolicy() = default;
};
// An map employing an array instead of a hash table to optimize performance,
// particularly beneficial when the number of expected items in the map is
// small.
template <typename K, typename V, typename Policy = NoOpPolicy>
class SimpleMap {
using ElementType = std::pair<K, V>;
using MapType = AutoTArray<ElementType, 16>;
public:
SimpleMap() : mLock("SimpleMap"){};
// Check if aKey is in the map.
bool Contains(const K& aKey) {
struct Comparator {
bool Equals(const ElementType& aElement, const K& aKey) const {
return aElement.first == aKey;
}
};
Policy guard(mLock);
return mMap.Contains(aKey, Comparator());
}
// Insert Key and Value pair at the end of our map.
void Insert(const K& aKey, const V& aValue) {
Policy guard(mLock);
mMap.AppendElement(std::make_pair(aKey, aValue));
}
// Sets aValue matching aKey and remove it from the map if found.
// The element returned is the first one found.
// Returns true if found, false otherwise.
bool Find(const K& aKey, V& aValue) {
if (Maybe<V> v = Take(aKey)) {
aValue = v.extract();
return true;
}
return false;
}
// Take the value matching aKey and remove it from the map if found.
Maybe<V> Take(const K& aKey) {
Policy guard(mLock);
for (uint32_t i = 0; i < mMap.Length(); i++) {
ElementType& element = mMap[i];
if (element.first == aKey) {
Maybe<V> value = Some(element.second);
mMap.RemoveElementAt(i);
return value;
}
}
return Nothing();
}
// Remove all elements of the map.
void Clear() {
Policy guard(mLock);
mMap.Clear();
}
// Iterate through all elements of the map and call the function F.
template <typename F>
void ForEach(F&& aCallback) {
Policy guard(mLock);
for (const auto& element : mMap) {
aCallback(element.first, element.second);
}
}
private:
typename Policy::PolicyLock mLock;
MapType mMap;
};
} // namespace mozilla
#endif // mozilla_SimpleMap_h
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