46 lines
1.7 KiB
C#
46 lines
1.7 KiB
C#
// Copyright (c) All contributors. All rights reserved.
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// Licensed under the MIT license. See LICENSE file in the project root for full license information.
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using System;
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using System.Reflection;
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using MessagePack.Formatters;
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#nullable enable
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namespace MessagePack.Internal
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{
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internal static class ResolverUtilities
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{
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internal static IMessagePackFormatter ActivateFormatter(Type formatterType, object?[]? args = null)
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{
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if (args == null || args.Length == 0)
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{
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if (formatterType.GetConstructor(Type.EmptyTypes) is ConstructorInfo ctor)
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{
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return (IMessagePackFormatter)ctor.Invoke(Array.Empty<object>());
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}
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else if (FetchSingletonField(formatterType) is FieldInfo instance)
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{
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return (IMessagePackFormatter)(instance.GetValue(null) ?? throw new InvalidOperationException($"{instance.ReflectedType?.FullName}.{instance.Name} return null."));
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}
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else
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{
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throw new MessagePackSerializationException($"The {formatterType.FullName} formatter has no default constructor nor implements the singleton pattern.");
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}
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}
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else
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{
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return (IMessagePackFormatter)Activator.CreateInstance(formatterType, args)!;
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}
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}
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internal static FieldInfo? FetchSingletonField(Type formatterType)
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{
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if (formatterType.GetField("Instance", BindingFlags.Static | BindingFlags.Public) is FieldInfo fieldInfo && fieldInfo.IsInitOnly)
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{
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return fieldInfo;
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}
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return null;
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}
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}
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}
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