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VBRIHeader.cs

//
// VBRIHeader.cs: Provides information about a variable bitrate MPEG audio
// stream encoded with the Fraunhofer Encoder.
//
// Author:
//   Helmut Wahrmann
//
// Original Source:
//   XingHeader.cs
//
// Copyright (C) 2007 Helmut Wahrmann
// Copyright (C) 2005-2007 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.Collections;
using System;

namespace TagLib.Mpeg {
      /// <summary>
      ///    This structure provides information about a variable bitrate MPEG
      ///    audio stream encoded by the Fraunhofer Encoder.
      /// </summary>
00037       public struct VBRIHeader
      {
#region Private Fields
            
            /// <summary>
            ///    Contains the frame count.
            /// </summary>
00044             private uint frames;
            
            /// <summary>
            ///    Contains the stream size.
            /// </summary>
00049             private uint size;
            
            /// <summary>
            ///    Indicates that a physical VBRI header is present.
            /// </summary>
00054             private bool present;
            
#endregion
            
            
            
#region Public Fields
            
            /// <summary>
            ///    Contains te VBRI identifier.
            /// </summary>
            /// <value>
            ///    "VBRI"
            /// </value>
00068             public static readonly ReadOnlyByteVector FileIdentifier = "VBRI";
            
            /// <summary>
            ///    An empty and unset VBRI header.
            /// </summary>
00073             public static readonly VBRIHeader Unknown = new VBRIHeader (0, 0);
            
#endregion
            
            
            
#region Constructors
            
            /// <summary>
            ///    Constructs and initializes a new instance of <see
            ///    cref="VBRIHeader" /> with a specified frame count and
            ///    size.
            /// </summary>
            /// <param name="frame">
            ///    A <see cref="uint" /> value specifying the frame count of
            ///    the audio represented by the new instance.
            /// </param>
            /// <param name="size">
            ///    A <see cref="uint" /> value specifying the stream size of
            ///    the audio represented by the new instance.
            /// </param>
00094             private VBRIHeader (uint frame, uint size)
            {
                  this.frames = frame;
                  this.size = size;
                  this.present = false;
            }
            
            /// <summary>
            ///    Constructs and initializes a new instance of <see
            ///    cref="VBRIHeader" /> by reading its raw contents.
            /// </summary>
            /// <param name="data">
            ///    A <see cref="ByteVector" /> object containing the raw
            ///    VBRI header.
            /// </param>
            /// <exception cref="ArgumentNullException">
            ///    <paramref name="data" /> is <see langword="null" />.
            /// </exception>
            /// <exception cref="CorruptFileException">
            ///    <paramref name="data" /> does not start with <see
            ///    cref="FileIdentifier" />.
            /// </exception>
00116             public VBRIHeader (ByteVector data)
            {
                  if (data == null)
                        throw new ArgumentNullException ("data");
                  
                  // Check to see if a valid VBRI header is available.
                  if (!data.StartsWith (FileIdentifier))
                        throw new CorruptFileException (
                              "Not a valid VBRI header");
                  
                  // Size starts at Position 10
                  int position = 10;

                  size = data.Mid(position, 4).ToUInt();
                  position += 4;

                  // The number of Frames are found at Posistion 14
                  frames = data.Mid(position, 4).ToUInt();
                  position += 4;
                  
                  present = true;
            }
            
#endregion
            
            
            
#region Public Properties
            
            /// <summary>
            ///    Gets the total number of frames in the file, as indicated
            ///    by the current instance.
            /// </summary>
            /// <value>
            ///    A <see cref="uint" /> value containing the number of
            ///    frames in the file, or <c>0</c> if not specified.
            /// </value>
00153             public uint TotalFrames {
                  get {return frames;}
            }
            
            /// <summary>
            ///    Gets the total size of the file, as indicated by the
            ///    current instance.
            /// </summary>
            /// <value>
            ///    A <see cref="uint" /> value containing the total size of
            ///    the file, or <c>0</c> if not specified.
            /// </value>
00165             public uint TotalSize {
                  get {return size;}
            }
            
            /// <summary>
            ///    Gets whether or not a physical VBRI header is present in
            ///    the file.
            /// </summary>
            /// <value>
            ///    A <see cref="bool" /> value indicating whether or not the
            ///    current instance represents a physical VBRI header.
            /// </value>
00177             public bool Present {
                  get {return present;}
            }
            
#endregion
            
            
            
#region Public Static Methods
            
            /// <summary>
            ///    Gets the offset at which a VBRI header would appear in an
            ///    MPEG audio packet.
            ///    Always 32 bytes after the end of the first MPEG Header.
            /// </summary>
            /// <returns>
            ///    A <see cref="int" /> value indicating the offset in an
            ///    MPEG audio packet at which the VBRI header would appear.
            /// </returns>
00196             public static int VBRIHeaderOffset ()
            {
                  // A VBRI header always appears 32 bytes after the end
                  // of the first MPEG Header. So it's position 36 (0x24).
                  return 0x24;
            }
            
#endregion
      }
}

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