private void Shrink()
{
int removed = 0;
int toRemove = dictionary.Count - (int)(shrinkFactor * capacity);
while (removed < toRemove)
{
LinkedDictionary <TKey, ValueWrapper> dict = GetDictByFrequency(lowestFrequency);
if (dict.Count == 0)
{
throw new Exception();
}
while (dict.Count > 0 && removed < toRemove)
{
var key = dict.FirstKey;
bool r = dict.Remove(key);
dictionary.Remove(key);
++removed;
}
if (dict.Count == 0)
{
UpdateLowestFrequency();
}
}
}
public LRUCache(int capacity)
{
if (capacity <= 0)
{
throw new ArgumentOutOfRangeException($"invalid argument {nameof(capacity)}");
}
this.capacity = capacity;
linkedDictionary = new LinkedDictionary <TKey, TValue>(capacity);
}
private LinkedDictionary <TKey, ValueWrapper> GetDictByFrequency(int frequency)
{
if (frequency < 0 || frequency > maxFrequency)
{
throw new Exception();
}
if (dictByFrequency[frequency] == null)
{
dictByFrequency[frequency] = new LinkedDictionary <TKey, ValueWrapper>();
}
return(dictByFrequency[frequency]);
}
public bool Remove(TKey key)
{
ValueWrapper wrapper = default;
if (dictionary.TryGetValue(key, out wrapper))
{
LinkedDictionary <TKey, ValueWrapper> dict = GetDictByFrequency(wrapper.frequency);
dict.Remove(key);
if (lowestFrequency == wrapper.frequency)
{
UpdateLowestFrequency();
}
return(true);
}
else
{
return(false);
}
}
public void Add(TKey key, TValue value)
{
if (dictionary.ContainsKey(key))
{
throw new ArgumentException("An item with the same key has already been added");
}
if (dictionary.Count == capacity)
{
Shrink();
}
LinkedDictionary <TKey, ValueWrapper> dict = GetDictByFrequency(0);
ValueWrapper wrapper = new ValueWrapper(value, 0);
dict.Add(key, wrapper);
dictionary[key] = wrapper;
lowestFrequency = 0;
}
public bool TryGetValue(TKey key, out TValue value)
{
ValueWrapper wrapper = default;
if (dictionary.TryGetValue(key, out wrapper))
{
int currentFrequency = wrapper.frequency;
if (currentFrequency < maxFrequency)
{
int nextFrequency = currentFrequency + 1;
LinkedDictionary <TKey, ValueWrapper> curDict = GetDictByFrequency(currentFrequency);
LinkedDictionary <TKey, ValueWrapper> nextDict = GetDictByFrequency(nextFrequency);
curDict.Remove(key);
nextDict.Add(key, wrapper);
wrapper.frequency = nextFrequency;
dictionary[key] = wrapper;
if (lowestFrequency == currentFrequency && curDict.Count == 0)
{
lowestFrequency = nextFrequency;
}
}
else
{
// f相同时 用LRU策略
LinkedDictionary <TKey, ValueWrapper> dict = GetDictByFrequency(currentFrequency);
dict.Remove(key);
dict.Add(key, wrapper);
}
value = wrapper.value;
return(true);
}
else
{
value = default;
return(false);
}
}
public FIFOCache(int capacity)
{
this.capacity = capacity;
this.linkedDictionary = new LinkedDictionary <TKey, TValue>();
}