Periodically prune empty elements in weak cache

pull/541/head
Kyle Cooley 6 years ago committed by Andrei Kortunov
parent 0096951f25
commit 7eb1b14b21

@ -3,6 +3,7 @@
#include <memory>
#include <unordered_map>
#include <vector>
namespace cache
{
@ -19,18 +20,19 @@ namespace cache
class iterator
{
public:
iterator(typename Map::iterator current, typename Map::iterator end);
iterator(WeakCache* cache, typename Map::iterator current, typename Map::iterator end);
iterator& operator++();
bool operator==(const iterator& other);
bool operator!=(const iterator& other);
StrongPtr operator*();
private:
WeakCache* mCache;
typename Map::iterator mCurrent, mEnd;
StrongPtr mPtr;
};
/// Stores a weak pointer to the item.
void insert(Key key, StrongPtr value);
void insert(Key key, StrongPtr value, bool prune=true);
/// Retrieves the item associated with the key.
/// \return An item or null.
@ -39,14 +41,19 @@ namespace cache
iterator begin();
iterator end();
/// Removes known invalid entries
void prune();
private:
Map mData;
std::vector<Key> mDirty;
};
template <typename Key, typename T>
WeakCache<Key, T>::iterator::iterator(typename Map::iterator current, typename Map::iterator end)
: mCurrent(current)
WeakCache<Key, T>::iterator::iterator(WeakCache* cache, typename Map::iterator current, typename Map::iterator end)
: mCache(cache)
, mCurrent(current)
, mEnd(end)
{
// Move to 1st available valid item
@ -54,6 +61,7 @@ namespace cache
{
mPtr = mCurrent->second.lock();
if (mPtr) break;
else mCache->mDirty.push_back(mCurrent->first);
}
}
@ -62,7 +70,7 @@ namespace cache
{
auto next = mCurrent;
++next;
return *this = iterator(next, mEnd);
return *this = iterator(mCache, next, mEnd);
}
template <typename Key, typename T>
@ -85,9 +93,10 @@ namespace cache
template <typename Key, typename T>
void WeakCache<Key, T>::insert(Key key, StrongPtr value)
void WeakCache<Key, T>::insert(Key key, StrongPtr value, bool shouldPrune)
{
mData[key] = WeakPtr(value);
if (shouldPrune) prune();
}
template <typename Key, typename T>
@ -103,13 +112,26 @@ namespace cache
template <typename Key, typename T>
typename WeakCache<Key, T>::iterator WeakCache<Key, T>::begin()
{
return iterator(mData.begin(), mData.end());
return iterator(this, mData.begin(), mData.end());
}
template <typename Key, typename T>
typename WeakCache<Key, T>::iterator WeakCache<Key, T>::end()
{
return iterator(mData.end(), mData.end());
return iterator(this, mData.end(), mData.end());
}
template <typename Key, typename T>
void WeakCache<Key, T>::prune()
{
// Remove empty entries
for (auto& key : mDirty)
{
auto it = mData.find(key);
if (it != mData.end() && it->second.use_count() == 0)
mData.erase(it);
}
mDirty.clear();
}
}

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