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Document and (minor) refactor on MruCache class #2458

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merged 1 commit into from Dec 11, 2017
Merged

Document and (minor) refactor on MruCache class #2458

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44 changes: 22 additions & 22 deletions src/NLog/Internal/MruCache.cs
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Expand Up @@ -40,38 +40,38 @@ namespace NLog.Internal
/// </summary>
internal class MruCache<TKey, TValue>
{
private readonly Dictionary<TKey, MruItem> _dictionary;
private readonly Dictionary<TKey, MruCacheItem> _dictionary;
private readonly int _maxCapacity;
private long _currentVersion;

/// <summary>
/// Constructor
/// </summary>
/// <param name="maxCapacity">Max number of items to hold before discarding</param>
/// <param name="maxCapacity">Maximum number of items the cache will hold before discarding.</param>
public MruCache(int maxCapacity)
{
_maxCapacity = maxCapacity;
_dictionary = new Dictionary<TKey, MruItem>(_maxCapacity);
_dictionary = new Dictionary<TKey, MruCacheItem>(_maxCapacity);
_currentVersion = 1;
}

/// <summary>
/// Insert item into caceh
/// Attempt to insert item into cache.
/// </summary>
/// <param name="key">Dictionary Key</param>
/// <param name="value">Dictionary Value</param>
/// <returns>Key did not exist already</returns>
/// <param name="key">Key of the item to be inserted in the cache.</param>
/// <param name="value">Value of the item to be inserted in the cache.</param>
/// <returns><c>true</c> when the key does not already exist in the cache, <c>false</c> otherwise.</returns>
public bool TryAddValue(TKey key, TValue value)
{
lock (_dictionary)
{
MruItem item;
MruCacheItem item;
if (_dictionary.TryGetValue(key, out item))
{
var version = _currentVersion;
if (item.Version != version || !EqualityComparer<TValue>.Default.Equals(value, item.Value))
{
_dictionary[key] = new MruItem(value, version, false);
_dictionary[key] = new MruCacheItem(value, version, false);
}
return false; // Already exists
}
Expand All @@ -83,7 +83,7 @@ public bool TryAddValue(TKey key, TValue value)
PruneCache();
}

_dictionary.Add(key, new MruItem(value, _currentVersion, true));
_dictionary.Add(key, new MruCacheItem(value, _currentVersion, true));
return true;
}
}
Expand Down Expand Up @@ -147,14 +147,14 @@ private void PruneCache()
}

/// <summary>
/// Lookup existing item in cache
/// Lookup existing item in cache.
/// </summary>
/// <param name="key">Dictionary Key</param>
/// <param name="value">Dictionary Value [out]</param>
/// <returns>Key found</returns>
/// <param name="key">Key of the item to be searched in the cache.</param>
/// <param name="value">Output value of the item found in the cache.</param>
/// <returns><c>True</c> when the key is found in the cache, <c>false</c> otherwise.</returns>
public bool TryGetValue(TKey key, out TValue value)
{
MruItem item;
MruCacheItem item;
try
{
if (!_dictionary.TryGetValue(key, out item))
Expand All @@ -165,7 +165,7 @@ public bool TryGetValue(TKey key, out TValue value)
}
catch
{
item = default(MruItem); // Too many people in the same room
item = default(MruCacheItem); // Too many people in the same room
}

if (item.Version != _currentVersion || item.Virgin)
Expand All @@ -182,7 +182,7 @@ public bool TryGetValue(TKey key, out TValue value)
{
version = ++_currentVersion;
}
_dictionary[key] = new MruItem(item.Value, version, false);
_dictionary[key] = new MruCacheItem(item.Value, version, false);
}
}
else
Expand All @@ -197,13 +197,13 @@ public bool TryGetValue(TKey key, out TValue value)
return true;
}

struct MruItem
struct MruCacheItem
{
public readonly TValue Value;
public readonly long Version;
public readonly bool Virgin;
public TValue Value { get; }
public long Version { get; }
public bool Virgin { get; }

public MruItem(TValue value, long version, bool virgin)
public MruCacheItem(TValue value, long version, bool virgin)
{
Value = value;
Version = version;
Expand Down