protobuf/src/ProtocolBuffers/FieldAccess/SingleEnumAccessor.cs

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// http://github.com/jskeet/dotnet-protobufs/
// Original C++/Java/Python code:
// http://code.google.com/p/protobuf/
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using Google.ProtocolBuffers.Descriptors;

namespace Google.ProtocolBuffers.FieldAccess {
  /// <summary>
  /// Accessor for fields representing a non-repeated enum value.
  /// </summary>
  internal sealed class SingleEnumAccessor<TMessage, TBuilder> : SinglePrimitiveAccessor<TMessage, TBuilder>
      where TMessage : IMessage<TMessage, TBuilder>
      where TBuilder : IBuilder<TMessage, TBuilder> {

    private readonly EnumDescriptor enumDescriptor;

    internal SingleEnumAccessor(FieldDescriptor field, string name) : base(name) {
      enumDescriptor = field.EnumType;
    }

    /// <summary>
    /// Returns an EnumValueDescriptor representing the value in the builder.
    /// Note that if an enum has multiple values for the same number, the descriptor
    /// for the first value with that number will be returned.
    /// </summary>
    public override object GetValue(TMessage message) {
      // Note: This relies on the fact that the CLR allows unboxing from an enum to
      // its underlying value
      int rawValue = (int) base.GetValue(message);
      return enumDescriptor.FindValueByNumber(rawValue);
    }

    /// <summary>
    /// Sets the value as an enum (via an int) in the builder,
    /// from an EnumValueDescriptor parameter.
    /// </summary>
    public override void SetValue(TBuilder builder, object value) {
      ThrowHelper.ThrowIfNull(value, "value");
      EnumValueDescriptor valueDescriptor = (EnumValueDescriptor) value;
      base.SetValue(builder, valueDescriptor.Number);
    }
  }
}