mirror of https://github.com/dahall/Vanara.git
36 lines
1.8 KiB
C#
36 lines
1.8 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Reflection;
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namespace Vanara.PInvoke
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{
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/// <summary>Gets a static field's name from its value and caches the list for faster lookups.</summary>
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public class StaticFieldValueHash
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{
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private static Dictionary<(Type, Type), IDictionary<int, string>> cache = new Dictionary<(Type, Type), IDictionary<int, string>>();
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/// <summary>Tries to get the name of a static field from it's value.</summary>
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/// <typeparam name="TType">The type of the type.</typeparam>
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/// <typeparam name="TFieldType">The type of the field type.</typeparam>
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/// <param name="value">The value for which to search.</param>
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/// <param name="fieldName">On success, the name of the field.</param>
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/// <returns><see langword="true"/> if the value was found, otherwise <see langword="false"/>.</returns>
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public static bool TryGetFieldName<TType, TFieldType>(TFieldType value, out string fieldName)
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{
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var tt = (typeof(TType), typeof(TFieldType));
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if (!cache.TryGetValue(tt, out var hash))
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cache.Add(tt, hash = typeof(TType).GetFields(BindingFlags.Public | BindingFlags.Static).Where(fi => fi.FieldType == typeof(TFieldType)).Distinct(FIValueComp<TFieldType>.Default).ToDictionary(fi => fi.GetValue(null).GetHashCode(), fi => fi.Name));
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return hash.TryGetValue(value.GetHashCode(), out fieldName);
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}
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private class FIValueComp<TFieldType> : IEqualityComparer<FieldInfo>
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{
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bool IEqualityComparer<FieldInfo>.Equals(FieldInfo x, FieldInfo y) => Comparer<TFieldType>.Default.Compare((TFieldType)x.GetValue(null), (TFieldType)y.GetValue(null)) == 0;
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int IEqualityComparer<FieldInfo>.GetHashCode(FieldInfo obj) => ((TFieldType)obj.GetValue(null)).GetHashCode();
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public static readonly FIValueComp<TFieldType> Default = new FIValueComp<TFieldType>();
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}
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}
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} |