/// <summary>
        /// Retrieves a signed 64-bit integer value for the specified option field,
        /// assuming a zigzag encoding.
        /// </summary>
        /// <param name="field">The field to fetch the value for.</param>
        /// <param name="value">The output variable to populate.</param>
        /// <returns><c>true</c> if a suitable value for the field was found; <c>false</c> otherwise.</returns>
        public bool TryGetSInt64(int field, out long value)
        {
            ulong?tmp = GetLastNumericValue(field);

            value = CodedInputStream.DecodeZigZag64(tmp.GetValueOrDefault());
            return(tmp != null);
        }