#region PDFsharp - A .NET library for processing PDF
//
// Authors:
//   Stefan Lange
//
// Copyright (c) 2005-2017 empira Software GmbH, Cologne Area (Germany)
//
// http://www.pdfsharp.com
// http://sourceforge.net/projects/pdfsharp
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
// DEALINGS IN THE SOFTWARE.
#endregion

using PdfSharp.Pdf.IO;

namespace PdfSharp.Pdf
{
    /// <summary>
    /// Represents an indirect null value. This type is not used by PDFsharp, but at least
    /// one tool from Adobe creates PDF files with a null object.
    /// </summary>
    public sealed class PdfNullObject : PdfObject
    {
        // Reference: 3.2.8  Null Object / Page 63

        /// <summary>
        /// Initializes a new instance of the <see cref="PdfNullObject"/> class.
        /// </summary>
        public PdfNullObject()
        { }

        /// <summary>
        /// Initializes a new instance of the <see cref="PdfNullObject"/> class.
        /// </summary>
        /// <param name="document">The document.</param>
        public PdfNullObject(PdfDocument document)
            : base(document)
        { }

        /// <summary>
        /// Returns the string "null".
        /// </summary>
        public override string ToString()
        {
            return "null";
        }

        /// <summary>
        /// Writes the keyword «null».
        /// </summary>
        internal override void WriteObject(PdfWriter writer)
        {
            writer.WriteBeginObject(this);
            writer.WriteRaw(" null ");
            writer.WriteEndObject();
        }
    }
}