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HeaderObject.cs

//
// HeaderObject.cs: Provides a representation of an ASF Header object which can
// be read from and written to disk.
//
// Author:
//   Brian Nickel (brian.nickel@gmail.com)
//
// Copyright (C) 2006-2007 Brian Nickel
// 
// This library is free software; you can redistribute it and/or modify
// it  under the terms of the GNU Lesser General Public License version
// 2.1 as published by the Free Software Foundation.
//
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
// USA
//

using System;
using System.Collections.Generic;

namespace TagLib.Asf {
      /// <summary>
      ///    This class extends <see cref="Object" /> to provide a
      ///    representation of an ASF Header object which can be read from and
      ///    written to disk.
      /// </summary>
00034       public class HeaderObject : Object
      {
            #region Private Fields
            
            /// <summary>
            ///    Contains the reserved header data.
            /// </summary>
00041             private ByteVector reserved;
            
            /// <summary>
            ///    Contains the child objects.
            /// </summary>
00046             private List<Object> children;
            
            #endregion
            
            
            
            #region Constructors
            
            /// <summary>
            ///    Constructs and initializes a new instance of <see
            ///    cref="HeaderObject" /> by reading the contents from a
            ///    specified position in a specified file.
            /// </summary>
            /// <param name="file">
            ///    A <see cref="Asf.File" /> object containing the file from
            ///    which the contents of the new instance are to be read.
            /// </param>
            /// <param name="position">
            ///    A <see cref="long" /> value specify at what position to
            ///    read the object.
            /// </param>
            /// <exception cref="ArgumentNullException">
            ///    <paramref name="file" /> is <see langword="null" />.
            /// </exception>
            /// <exception cref="ArgumentOutOfRangeException">
            ///    <paramref name="position" /> is less than zero or greater
            ///    than the size of the file.
            /// </exception>
            /// <exception cref="CorruptFileException">
            ///    The object read from disk does not have the correct GUID
            ///    or smaller than the minimum size.
            /// </exception>
00078             public HeaderObject (Asf.File file, long position)
                  : base (file, position)
            {
                  if (!Guid.Equals (Asf.Guid.AsfHeaderObject))
                        throw new CorruptFileException (
                              "Object GUID incorrect.");
                  
                  if (OriginalSize < 26)
                        throw new CorruptFileException (
                              "Object size too small.");
                  
                  children = new List<Object> ();
                  
                  uint child_count = file.ReadDWord ();
                  
                  reserved = file.ReadBlock (2);
                  
                  children.AddRange (file.ReadObjects (child_count,
                        file.Tell));
            }
            
            #endregion
            
            
            
            #region Public Properties
            
            /// <summary>
            ///    Gets the header extension object contained in the
            ///    current instance.
            /// </summary>
            /// <value>
            ///    A <see cref="HeaderExtensionObject" /> object containing
            ///    the header extension object.
            /// </value>
00113             public HeaderExtensionObject Extension {
                  get {
                        foreach (Object child in children)
                              if (child is HeaderExtensionObject)
                                    return child as HeaderExtensionObject;
                        return null;
                  }
            }
            
            /// <summary>
            ///    Gets the child objects contained in the current instance.
            /// </summary>
            /// <value>
            ///    A <see cref="T:System.Collections.Generic.IEnumerable`1" /> object enumerating
            ///    through the children of the current instance.
            /// </value>
00129             public IEnumerable<Object> Children {
                  get {return children;}
            }
            
            /// <summary>
            ///    Gets the media properties contained within the current
            ///    instance.
            /// </summary>
            /// <value>
            ///    A <see cref="Properties" /> object containing the media
            ///    properties of the current instance.
            /// </value>
00141             public Properties Properties {
                  get {
                        TimeSpan duration = TimeSpan.Zero;
                        List<ICodec> codecs = new List<ICodec> ();
                        
                        foreach (Object obj in Children) {
                              FilePropertiesObject fpobj = obj as
                                    FilePropertiesObject;
                              
                              if (fpobj != null) {
                                    duration = fpobj.PlayDuration -
                                          new TimeSpan((long) fpobj.Preroll);
                                    continue;
                              }
                              
                              StreamPropertiesObject spobj = obj as
                                    StreamPropertiesObject;
                              
                              if (spobj != null) {
                                    codecs.Add (spobj.Codec);
                                    continue;
                              }
                        }
                        
                        return new Properties (duration, codecs);
                  }
            }
            
            /// <summary>
            ///    Gets whether or not the current instance contains either
            ///    type of content descriptiors.
            /// </summary>
            /// <value>
            ///    <see langword="true" /> if the current instance contains
            ///    a <see cref="ContentDescriptionObject" /> or a <see
            ///    cref="ExtendedContentDescriptionObject" />. Otherwise
            ///    <see langword="false" />.
            /// </value>
00179             public bool HasContentDescriptors {
                  get {
                        foreach (Asf.Object child in children)
                              if (child.Guid == Asf.Guid.AsfContentDescriptionObject ||
                                    child.Guid == Asf.Guid.AsfExtendedContentDescriptionObject)
                                    return true;
                        
                        return false;
                  }
            }
            
            #endregion
            
            
            
            #region Public Methods
            
            /// <summary>
            ///    Renders the current instance as a raw ASF object.
            /// </summary>
            /// <returns>
            ///    A <see cref="ByteVector" /> object containing the
            ///    rendered version of the current instance.
            /// </returns>
00203             public override ByteVector Render ()
            {
                  ByteVector output = new ByteVector ();
                  uint child_count = 0;
                  
                  foreach (Object child in children)
                        if (child.Guid != Asf.Guid.AsfPaddingObject) {
                              output.Add (child.Render ());
                              child_count ++;
                        }
                  
                  long size_diff = (long) output.Count + 30 -
                        (long) OriginalSize;
                  
                  if (size_diff != 0) {
                        PaddingObject obj = new PaddingObject ((uint)
                              (size_diff > 0 ? 4096 : - size_diff));
                        
                        output.Add (obj.Render ());
                        child_count ++;
                  }
                  
                  output.Insert (0, reserved);
                  output.Insert (0, RenderDWord (child_count));
                  return Render (output);
            }
            
            /// <summary>
            ///    Adds a child object to the current instance.
            /// </summary>
            /// <param name="obj">
            ///    A <see cref="Object" /> object to add to the current
            ///    instance.
            /// </param>
00237             public void AddObject (Object obj)
            {
                  children.Add (obj);
            }
            
            /// <summary>
            ///    Adds a child unique child object to the current instance,
            ///    replacing and existing child if present.
            /// </summary>
            /// <param name="obj">
            ///    A <see cref="Object" /> object to add to the current
            ///    instance.
            /// </param>
00250             public void AddUniqueObject (Object obj)
            {
                  for (int i = 0; i < children.Count; i ++)
                        if (children [i].Guid == obj.Guid) {
                              children [i] = obj;
                              return;
                        }
                  
                  children.Add (obj);
            }
            
            /// <summary>
            ///    Removes the content description objects from the current
            ///    instance.
            /// </summary>
00265             public void RemoveContentDescriptors ()
            {
                  for (int i = children.Count - 1; i >= 0; i --)
                        if (children [i].Guid == Asf.Guid.AsfContentDescriptionObject ||
                              children [i].Guid == Asf.Guid.AsfExtendedContentDescriptionObject)
                              children.RemoveAt (i);
            }
            
            #endregion
      }
}

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