/// <summary>
/// Gets the length of the byte order marker. <see cref="Id3v2FrameEncodingType"/> for possible encoding types.
/// </summary>
/// <param name="encodingType">Type of the encoding.</param>
/// <returns>The length of the byte order marker, in bytes.</returns>
public static int GetBomLength(Id3v2FrameEncodingType encodingType)
{
switch (encodingType)
{
case Id3v2FrameEncodingType.Default:
case Id3v2FrameEncodingType.UTF16BigEndianWithoutBom:
return 0;
case Id3v2FrameEncodingType.UTF16BigEndian:
case Id3v2FrameEncodingType.UTF16LittleEndian:
return 2;
case Id3v2FrameEncodingType.UTF8:
case Id3v2FrameEncodingType.UTF7:
return 3;
}
return 0;
}
/// <summary>
/// Determines whether the string is a valid string in the specified frame encoding type and if it contains new line characters.
/// </summary>
/// <param name="textString">The string to check.</param>
/// <param name="frameEncodingType">Type of the frame encoding.</param>
/// <param name="newLineAllowed">if set to <c>true</c>, new lines are allowed in the string.</param>
/// <returns>
/// <c>true</c> if the string is a valid string in the specified frame encoding type; otherwise, <c>false</c>.
/// </returns>
/// <remarks>
/// An <see cref="Id3v2FrameEncodingType.Default"/> string is represented as characters in the range 0x20 - 0xFF.
/// In <see cref="Id3v2FrameEncodingType.Default"/> and <see cref="Id3v2FrameEncodingType.UTF8"/>
/// a new line is represented, when allowed, with 0x0A only.
/// In <see cref="Id3v2FrameEncodingType.UTF16LittleEndian"/> a new line is represented, when allowed, with 0x0A 0x00.
/// In <see cref="Id3v2FrameEncodingType.UTF16BigEndian"/> and <see cref="Id3v2FrameEncodingType.UTF16BigEndianWithoutBom"/>
/// a new line is represented, when allowed, with 0x00 0x0A.
/// </remarks>
public static bool IsValidTextString(string textString, Id3v2FrameEncodingType frameEncodingType, bool newLineAllowed)
{
if (textString == null)
throw new ArgumentNullException("textString");
switch (frameEncodingType)
{
case Id3v2FrameEncodingType.Default:
return textString.All(c => ((c >= (char)0x20) && (c <= (char)0xFF)) || (newLineAllowed && (c == '\n')));
case Id3v2FrameEncodingType.UTF16LittleEndian:
case Id3v2FrameEncodingType.UTF16BigEndian:
case Id3v2FrameEncodingType.UTF16BigEndianWithoutBom:
case Id3v2FrameEncodingType.UTF7:
case Id3v2FrameEncodingType.UTF8:
return textString.All(c => (newLineAllowed && (c == '\n')) || (c != '\0'));
default:
return true;
}
}
/// <summary>
/// Gets the encoding for the specific encoding type.
/// </summary>
/// <param name="encodingType">Type of the encoding.</param>
/// <returns>
/// The encoding for the specific encoding type.
/// </returns>
/// <remarks>
/// See <see cref="Id3v2FrameEncodingType"/> for possible values.
/// </remarks>
public static Encoding GetEncoding(Id3v2FrameEncodingType encodingType)
{
switch (encodingType)
{
case Id3v2FrameEncodingType.Default:
return Encoding.GetEncoding("ISO-8859-1");
case Id3v2FrameEncodingType.UTF16LittleEndian:
case Id3v2FrameEncodingType.UTF16BigEndian:
return (encodingType == Id3v2FrameEncodingType.UTF16LittleEndian)
? new UnicodeEncoding(false, true)
: new UnicodeEncoding(true, true);
case Id3v2FrameEncodingType.UTF16BigEndianWithoutBom:
return new UnicodeEncoding(true, false);
case Id3v2FrameEncodingType.UTF8:
return new UTF8Encoding(false);
case Id3v2FrameEncodingType.UTF7:
return new UTF7Encoding();
}
return Encoding.Default;
}
/// <summary>
/// Determines whether the specified encoding type is valid.
/// </summary>
/// <param name="encodingType">Type of the encoding.</param>
/// <returns>
/// <c>true</c> if the specified encoding type is valid; otherwise, <c>false</c>.
/// </returns>
public static bool IsValidEncodingType(Id3v2FrameEncodingType encodingType)
{
return Enum.TryParse(encodingType.ToString(), true, out encodingType);
}
/// <summary>
/// Gets the real value of the encoding type as defined in the Id3v2 specs.
/// </summary>
/// <param name="encodingType">Type of the encoding.</param>
/// <returns>The real value of the encoding type, as defined in the Id3v2 specs.</returns>
public static byte GetEncodingTypeValue(Id3v2FrameEncodingType encodingType)
{
if ((byte)encodingType >= EncodingTypes.Length)
throw new ArgumentOutOfRangeException("encodingType");
return EncodingTypes[(byte)encodingType];
}
/// <summary>
/// Gets the preamble of the specified encoding.
/// </summary>
/// <param name="encodingType">Type of the encoding.</param>
/// <returns>The preamble of the encoding, or an empty byte array if the encoding does not use a preamble.</returns>
public static byte[] GetEncodingPreamble(Id3v2FrameEncodingType encodingType)
{
switch (encodingType)
{
case Id3v2FrameEncodingType.Default:
case Id3v2FrameEncodingType.UTF16BigEndianWithoutBom:
case Id3v2FrameEncodingType.UTF8:
case Id3v2FrameEncodingType.UTF7:
return new byte[0];
case Id3v2FrameEncodingType.UTF16LittleEndian:
case Id3v2FrameEncodingType.UTF16BigEndian:
return
((encodingType == Id3v2FrameEncodingType.UTF16LittleEndian) ? Encoding.Unicode : Encoding.BigEndianUnicode).GetPreamble();
default:
throw new ArgumentOutOfRangeException("encodingType");
}
}
