path: root/src/ProtocolBuffers/Descriptors/FieldMappingAttribute.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/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
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using System;
using System.Collections.Generic;
using Google.ProtocolBuffers.Collections;

namespace Google.ProtocolBuffers.Descriptors {

  /// <summary>
  /// Defined specifically for the <see cref="FieldType" /> enumeration,
  /// this allows each field type to specify the mapped type and wire type.
  /// </summary>
  [CLSCompliant(false)]
  [AttributeUsage(AttributeTargets.Field)]
  public sealed class FieldMappingAttribute : Attribute {
    public FieldMappingAttribute(MappedType mappedType, WireFormat.WireType wireType) {
      MappedType = mappedType;
      WireType = wireType;
    }

    public MappedType MappedType { get; private set; }
    public WireFormat.WireType WireType { get; private set; }


    /// <summary>
    /// Immutable mapping from field type to mapped type. Built using the attributes on
    /// FieldType values.
    /// </summary>
    static readonly IDictionary<FieldType, FieldMappingAttribute> FieldTypeToMappedTypeMap = MapFieldTypes();

    private static IDictionary<FieldType, FieldMappingAttribute> MapFieldTypes() {
      var map = new Dictionary<FieldType, FieldMappingAttribute>();
      foreach (System.Reflection.FieldInfo field in typeof(FieldType).GetFields(System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.Public)) {
        FieldType fieldType = (FieldType)field.GetValue(null);
        FieldMappingAttribute mapping = (FieldMappingAttribute)field.GetCustomAttributes(typeof(FieldMappingAttribute), false)[0];
        map[fieldType] = mapping;
      }
      return Dictionaries.AsReadOnly(map);
    }

    internal static MappedType MappedTypeFromFieldType(FieldType type) {
      return FieldTypeToMappedTypeMap[type].MappedType;
    }
    internal static WireFormat.WireType WireTypeFromFieldType(FieldType type, bool packed) {
      return packed ? WireFormat.WireType.LengthDelimited : FieldTypeToMappedTypeMap[type].WireType;
    }
  }
}