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Footer.cs

//
// Footer.cs:
//
// Author:
//   Brian Nickel (brian.nickel@gmail.com)
//
// Original Source:
//   id3v2header.cpp from TagLib
//
// Copyright (C) 2005-2007 Brian Nickel
// Copyright (C) 2002,2003 Scott Wheeler (Original Implementation)
//
// 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;

namespace TagLib.Id3v2
{
      
      /// <summary>
      ///    This structure provides a representation of an ID3v2 tag footer
      ///    which can be read from and written to disk.
      /// </summary>
00037       public struct Footer
      {
#region Private Fields
            
            /// <summary>
            ///    Contains the tag's major version.
            /// </summary>
00044             private byte major_version;
            
            /// <summary>
            ///    Contains the tag's version revision.
            /// </summary>
00049             private byte revision_number;
            
            /// <summary>
            ///    Contains tag's flags.
            /// </summary>
00054             private HeaderFlags flags;
            
            /// <summary>
            ///    Contains the tag size.
            /// </summary>
00059             private uint tag_size;
            
#endregion
            
            
            
#region Public Fields
            
            /// <summary>
            ///    The size of a ID3v2 footer.
            /// </summary>
00070             public const uint Size = 10;
            
            /// <summary>
            ///    The identifier used to recognize a ID3v2 footer.
            /// </summary>
            /// <value>
            ///    "3DI"
            /// </value>
00078             public static readonly ReadOnlyByteVector FileIdentifier = "3DI";
            
#endregion
            
            
            
#region Constructors
            
            /// <summary>
            ///    Constructs and initializes a new instance of <see
            ///    cref="Footer" /> by reading it from raw footer data.
            /// </summary>
            /// <param name="data">
            ///    A <see cref="ByteVector" /> object containing the raw
            ///    data to build the new instance from.
            /// </param>
            /// <exception cref="ArgumentNullException">
            ///    <paramref name="data" /> is <see langword="null" />.
            /// </exception>
            /// <exception cref="CorruptFileException">
            ///    <paramref name="data" /> is smaller than <see
            ///    cref="Size" />, does not begin with <see
            ///    cref="FileIdentifier" />, contains invalid flag data,
            ///    or contains invalid size data.
            /// </exception>
00103             public Footer (ByteVector data)
            {
                  if (data == null)
                        throw new ArgumentNullException ("data");
                  
                  if (data.Count < Size)
                        throw new CorruptFileException (
                              "Provided data is smaller than object size.");
                  
                  if (!data.StartsWith (FileIdentifier))
                        throw new CorruptFileException (
                              "Provided data does not start with the file identifier");
                  
                  major_version = data [3];
                  revision_number = data [4];
                  flags = (HeaderFlags) data [5];
                  
                  if (major_version == 2 && ((int) flags & 127) != 0)
                        throw new CorruptFileException (
                              "Invalid flags set on version 2 tag.");
                  
                  if (major_version == 3 && ((int) flags & 15) != 0)
                        throw new CorruptFileException (
                              "Invalid flags set on version 3 tag.");
                  
                  if (major_version == 4 && ((int) flags & 7) != 0)
                        throw new CorruptFileException (
                              "Invalid flags set on version 4 tag.");
                  
                  for (int i = 6; i < 10; i ++)
                        if (data [i] >= 128)
                              throw new CorruptFileException (
                                    "One of the bytes in the header was greater than the allowed 128.");
                  
                  tag_size = SynchData.ToUInt (data.Mid (6, 4));
            }
            
            /// <summary>
            ///    Constructs and intializes a new instance of <see
            ///    cref="Footer" /> by reading in the contents of the header
            ///    object used for the same tag.
            /// </summary>
            /// <param name="header">
            ///    A <see cref="Header" /> object to base the new instance
            ///    off of.
            /// </param>
00149             public Footer (Header header)
            {
                  major_version = header.MajorVersion;
                  revision_number = header.RevisionNumber;
                  flags = header.Flags | HeaderFlags.FooterPresent;
                  tag_size = header.TagSize;
            }
            
#endregion
            
            
            
#region Public Properties
            
            /// <summary>
            ///    Gets and sets the major version of the tag described by
            ///    the current instance.
            /// </summary>
            /// <value>
            ///    A <see cref="byte" /> value specifying the ID3v2 version
            ///    of tag described by the current instance.
            /// </value>
            /// <remarks>
            ///    When the version is set, unsupported header flags will
            ///    automatically be removed from the tag.
            /// </remarks>
            /// <exception cref="ArgumentOutOfRangeException">
            ///    <paramref name="value" /> is not 4.
            /// </exception>
00178             public byte MajorVersion {
                  get {
                        return major_version == 0 ? Tag.DefaultVersion :
                              major_version;
                  }
                  set {
                        if (value != 4)
                              throw new ArgumentException (
                                    "Version unsupported.");
                        
                        major_version = value;
                  }
            }
            
            /// <summary>
            ///    Gets and sets the version revision number of the tag
            ///    represented by the current instance.
            /// </summary>
            /// <value>
            ///    A <see cref="byte" /> value containing the version
            ///    revision number of the tag represented by the current
            ///    instance.
            /// </value>
            /// <remarks>
            ///    This value should always be zeroed. A non-zero value
            ///    indicates an experimental or new version of the format
            ///    which may not be completely understood by the current
            ///    implementation. Some software may refuse to read tags
            ///    with a non-zero value.
            /// </remarks>
00208             public byte RevisionNumber {
                  get {return revision_number;}
                  set {revision_number = value;}
            }
            
            /// <summary>
            ///    Gets and sets the flags applied to the current instance.
            /// </summary>
            /// <value>
            ///    A bitwise combined <see cref="HeaderFlags" /> value
            ///    containing the flags applied to the current instance.
            /// </value>
            /// <exception cref="ArgumentException">
            ///    <paramref name="value" /> contains a flag not supported
            ///    by the the ID3v2 version of the current instance.
            /// </exception>
00224             public HeaderFlags Flags {
                  get {return flags;}
                  set {
                        if (0 != (value & (HeaderFlags.ExtendedHeader |
                              HeaderFlags.ExperimentalIndicator)) &&
                              MajorVersion < 3)
                              throw new ArgumentException (
                                    "Feature only supported in version 2.3+",
                                    "value");
                        
                        if (0 != (value & HeaderFlags.FooterPresent) &&
                              MajorVersion < 3)
                              throw new ArgumentException (
                                    "Feature only supported in version 2.4+",
                                    "value");
                        
                        flags = value;
                  }
            }
            
            /// <summary>
            ///    Gets and sets the size of the tag described by the
            ///    current instance, minus the header and footer.
            /// </summary>
            /// <value>
            ///    A <see cref="uint" /> value containing the size of the
            ///    tag described by the current instance.
            /// </value>
00252             public uint TagSize {
                  get {return tag_size;}
                  set {tag_size = value;}
            }
            
            /// <summary>
            ///    Gets the complete size of the tag described by the
            ///    current instance, including the header and footer.
            /// </summary>
            /// <value>
            ///    A <see cref="uint" /> value containing the complete size
            ///    of the tag described by the current instance.
            /// </value>
00265             public uint CompleteTagSize {
                  get {return TagSize + Header.Size + Size;}
            }
            
#endregion
            
            
            
#region Public Methods
            
            /// <summary>
            ///    Renders the current instance as a raw ID3v2 header.
            /// </summary>
            /// <returns>
            ///    A <see cref="ByteVector" /> object containing the
            ///    rendered header.
            /// </returns>
00282             public ByteVector Render ()
            {
                  ByteVector v = new ByteVector ();
                  v.Add (FileIdentifier);
                  v.Add (MajorVersion);
                  v.Add (RevisionNumber);
                  v.Add ((byte)flags);
                  v.Add (SynchData.FromUInt (TagSize));
                  return v;
            }
            
#endregion
      }
}

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