Logo Search packages:      
Sourcecode: f-spot version File versions  Download package

SynchData.cs

//
// SynchData.cs: Provides support for encoding and decoding unsynchronized data
// and numbers.
//
// Author:
//   Brian Nickel (brian.nickel@gmail.com)
//
// Original Source:
//   id3v2synchdata.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 static class provides support for encoding and decoding
      ///    unsynchronized data and numbers.
      /// </summary>
      /// <remarks>
      ///    Unsynchronization is designed so that portions of the tag won't
      ///    be misinterpreted as MPEG audio stream headers by removing the
      ///    possibility of the synch bytes occuring in the tag.
      /// </remarks>
00041       public static class SynchData
      {
            /// <summary>
            ///    Decodes synchronized integer data into a <see
            ///    cref="uint" /> value.
            /// </summary>
            /// <param name="data">
            ///    A <see cref="ByteVector" /> object containing the number
            ///    to decode. Only the first 4 bytes of this value will be
            ///    used.
            /// </param>
            /// <returns>
            ///    A <see cref="uint" /> value containing the decoded
            ///    number.
            /// </returns>
            /// <exception cref="ArgumentNullException">
            ///    <paramref name="data" /> is <see langword="null" />.
            /// </exception>
00059             public static uint ToUInt (ByteVector data)
            {
                  if (data == null)
                        throw new ArgumentNullException ("data");
                  
                  uint sum = 0;
                  int last = data.Count > 4 ? 3 : data.Count - 1;
                  
                  for(int i = 0; i <= last; i++)
                        sum |= (uint) (data [i] & 0x7f)
                              << ((last - i) * 7);
                  
                  return sum;
            }
            
            /// <summary>
            ///    Encodes a <see cref="uint" /> value as synchronized
            ///    integer data.
            /// </summary>
            /// <param name="value">
            ///    A <see cref="uint" /> value containing the number to
            ///    encode.
            /// </param>
            /// <returns>
            ///    A <see cref="ByteVector" /> object containing the encoded
            ///    number.
            /// </returns>
            /// <exception cref="ArgumentOutOfRangeException">
            ///    <paramref name="value" /> is greater than 268435455.
            /// </exception>
00089             public static ByteVector FromUInt (uint value)
            {
                  if ((value >> 28) != 0)
                        throw new ArgumentOutOfRangeException ("value",
                              "value must be less than 268435456.");
                  
                  ByteVector v = new ByteVector (4, 0);
                  
                  for (int i = 0; i < 4; i++)
                        v [i] = (byte) (value >> ((3 - i) * 7) & 0x7f);
                  
                  return v;
            }
            
            /// <summary>
            ///    Unsynchronizes a <see cref="ByteVector" /> object by
            ///    inserting empty bytes where necessary.
            /// </summary>
            /// <param name="data">
            ///    A <see cref="ByteVector" /> object to unsynchronize.
            /// </param>
            /// <exception cref="ArgumentNullException">
            ///    <paramref name="data" /> is <see langword="null" />.
            /// </exception>
00113             public static void UnsynchByteVector (ByteVector data)
            {
                  if (data == null)
                        throw new ArgumentNullException ("data");
                  
                  for (int i = data.Count - 2; i >= 0; i --)
                        if (data [i] == 0xFF && (data [i+1] == 0 ||
                              (data [i+1] & 0xE0) != 0))
                              data.Insert (i+1, 0);
            }
            
            /// <summary>
            ///    Resynchronizes a <see cref="ByteVector" /> object by
            ///    removing the added bytes.
            /// </summary>
            /// <param name="data">
            ///    A <see cref="ByteVector" /> object to resynchronize.
            /// </param>
            /// <exception cref="ArgumentNullException">
            ///    <paramref name="data" /> is <see langword="null" />.
            /// </exception>
00134             public static void ResynchByteVector (ByteVector data)
            {
                  if (data == null)
                        throw new ArgumentNullException ("data");
                  
                  for (int i = data.Count - 2; i >= 0; i --)
                        if (data [i] == 0xFF && data [i+1] == 0)
                              data.RemoveAt (i+1);
            }
      }
}

Generated by  Doxygen 1.6.0   Back to index