ClearScript/ClearScript/CanonicalRefTable.cs at master · tlecomte/ClearScript · GitHub

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// Licensed under the MIT license.

using System;

using System.Collections.Generic;

using System.Linq;

using Microsoft.ClearScript.Util;

namespace Microsoft.ClearScript

{

internal static class CanonicalRefTable

{

private static readonly Dictionary<Type, ICanonicalRefMap> table = new Dictionary<Type, ICanonicalRefMap>();

public static object GetCanonicalRef(object obj)

{

if (obj is ValueType)

{

var map = GetMap(obj);

if (map != null)

{

obj = map.GetRef(obj);

}

return obj;

}

private static ICanonicalRefMap GetMap(object obj)

{

var type = obj.GetType();

lock (table)

{

if (!table.TryGetValue(type, out var map))

{

if (type.IsEnum ||

type.IsNumeric() ||

type == typeof(DateTime) ||

type == typeof(DateTimeOffset) ||

type == typeof(TimeSpan) ||

type.GetCustomAttributes(typeof(ImmutableValueAttribute), false).Any())

{

map = (ICanonicalRefMap)typeof(CanonicalRefMap<>).MakeGenericType(type).CreateInstance();

}

table.Add(type, map);

}

return map;

}

#region Nested type: ICanonicalRefMap

private interface ICanonicalRefMap

{

object GetRef(object obj);

}

#endregion

#region Nested type: CanonicalRefMapBase

private abstract class CanonicalRefMapBase : ICanonicalRefMap

{

protected const int CompactionThreshold = 256 * 1024;

protected static readonly TimeSpan CompactionInterval = TimeSpan.FromMinutes(2);

#region ICanonicalRefMap implementation (abstract)

public abstract object GetRef(object obj);

#endregion

}

#endregion

#region Nested type: CanonicalRefMap<T>

private sealed class CanonicalRefMap<T> : CanonicalRefMapBase

{

private readonly Dictionary<T, WeakReference> map = new Dictionary<T, WeakReference>();

private DateTime lastCompactionTime = DateTime.MinValue;

private object GetRefInternal(object obj)

{

var value = (T)obj;

object result;

if (map.TryGetValue(value, out var weakRef))

{

result = weakRef.Target;

if (result == null)

{

result = obj;

weakRef.Target = result;

}

else

{

result = obj;

map.Add(value, new WeakReference(result));

}

return result;

}

private void CompactIfNecessary()

{

if (map.Count >= CompactionThreshold)

{

var now = DateTime.UtcNow;

if ((lastCompactionTime + CompactionInterval) <= now)

{

map.Where(pair => !pair.Value.IsAlive).ToList().ForEach(pair => map.Remove(pair.Key));

lastCompactionTime = now;

}

#region CanonicalRefMapBase overrides

public override object GetRef(object obj)

{

lock (map)

{

var result = GetRefInternal(obj);

CompactIfNecessary();

return result;

}

#endregion

}

#endregion

}

ClearScript/ClearScript/CanonicalRefTable.cs at master · tlecomte/ClearScript · GitHub

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