/// <summary>
        /// Parse a single field from <paramref name="input"/> and merge it
        /// into this set.
        /// </summary>
        /// <param name="input">The coded input stream containing the field</param>
        /// <returns>false if the tag is an "end group" tag, true otherwise</returns>
        private bool MergeFieldFrom(CodedInputStream input)
        {
            uint tag    = input.LastTag;
            int  number = WireFormat.GetTagFieldNumber(tag);

            switch (WireFormat.GetTagWireType(tag))
            {
            case WireFormat.WireType.Varint:
            {
                ulong uint64 = input.ReadUInt64();
                GetOrAddField(number).AddVarint(uint64);
                return(true);
            }

            case WireFormat.WireType.Fixed32:
            {
                uint uint32 = input.ReadFixed32();
                GetOrAddField(number).AddFixed32(uint32);
                return(true);
            }

            case WireFormat.WireType.Fixed64:
            {
                ulong uint64 = input.ReadFixed64();
                GetOrAddField(number).AddFixed64(uint64);
                return(true);
            }

            case WireFormat.WireType.LengthDelimited:
            {
                ByteString bytes = input.ReadBytes();
                GetOrAddField(number).AddLengthDelimited(bytes);
                return(true);
            }

            case WireFormat.WireType.StartGroup:
            {
                UnknownFieldSet set = new UnknownFieldSet();
                input.ReadGroup(number, set);
                GetOrAddField(number).AddGroup(set);
                return(true);
            }

            case WireFormat.WireType.EndGroup:
            {
                return(false);
            }

            default:
                throw InvalidProtocolBufferException.InvalidWireType();
            }
        }