protobuf/csharp/ProtocolBuffers/WireFormat.cs

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.
// http://code.google.com/p/protobuf/
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
namespace Google.ProtocolBuffers {
  public class WireFormat {
    public enum WireType : uint {
      Varint = 0,
      Fixed64 = 1,
      LengthDelimited = 2,
      StartGroup = 3,
      EndGroup = 4,
      Fixed32 = 5
    }

    internal class MessageSetField {
      internal const int Item = 1;
      internal const int TypeID = 2;
      internal const int Message = 3;
    }

    private const int TagTypeBits = 3;
    private const uint TagTypeMask = (1 << TagTypeBits) - 1;

    /// <summary>
    /// Given a tag value, determines the wire type (lower 3 bits).
    /// </summary>
    public static WireType GetTagWireType(uint tag) {
      return (WireType) (tag & TagTypeMask);
    }

    /// <summary>
    /// Given a tag value, determines the field number (the upper 29 bits).
    /// </summary>
    public static uint GetTagFieldNumber(uint tag) {
      return tag >> TagTypeBits;
    }

    /// <summary>
    /// Makes a tag value given a field number and wire type.
    /// </summary>
    public static uint MakeTag(int fieldNumber, WireType wireType) {
      return (uint) (fieldNumber << TagTypeBits) | (uint) wireType;
    }
  }
}