/// <summary>
/// Reads the ID3v1 tag using specified code page for text encoding.
/// </summary>
/// <param name="inputStream">the input stream (i.e. the file.)</param>
/// <param name="codePage">The code page for text encoding.</param>
/// <returns>An ID3v1 container.</returns>
public Id3V1Tag Read(Stream inputStream, int codePage)
{
if (!inputStream.CanSeek)
{
var ex = new Id3TagException("Cannot read ID3v1 tag because the stream does not support seek.");
Logger.LogError(ex);
throw ex;
}
if (inputStream.Length < 128)
{
var ex = new Id3IOException("Cannot read ID3v1 tag because the stream is too short");
Logger.LogError(ex);
throw ex;
}
//
// Read the last 128 Bytes from the stream (ID3v1 Position)
//
var tagBytes = new byte[128];
inputStream.Seek(-128, SeekOrigin.End);
inputStream.Read(tagBytes, 0, 128);
bool isValidTag = CheckID(tagBytes);
if (!isValidTag)
{
var ex = new Id3HeaderNotFoundException("TAG header not found");
Logger.LogError(ex);
throw ex;
}
Id3V1Tag v1Tag = ExtractTag(tagBytes, codePage);
return v1Tag;
}
private static int AnalyseHeader(byte[] headerBytes, Id3TagInfo tagInfo)
{
// Check ID3 pattern
bool id3PatternFound = (headerBytes[0] == 0x49) && (headerBytes[1] == 0x44) && (headerBytes[2] == 0x33);
if (!id3PatternFound)
{
var ex = new Id3HeaderNotFoundException();
Logger.LogError(ex);
throw ex;
}
int majorVersion = Convert.ToInt32(headerBytes[3]);
int revision = Convert.ToInt32(headerBytes[4]);
byte flagByte = headerBytes[5];
var sizeBytes = new byte[4];
// Analyse the header...
tagInfo.MajorVersion = majorVersion;
tagInfo.Revision = revision;
bool unsynchronisationFlag = (flagByte & 0x80) == 0x80;
bool extendedHeaderFlag = (flagByte & 0x40) == 0x40;
bool experimentalFlag = (flagByte & 0x20) == 0x20;
tagInfo.Unsynchronised = unsynchronisationFlag;
tagInfo.ExtendedHeaderAvailable = extendedHeaderFlag;
tagInfo.Experimental = experimentalFlag;
if (majorVersion == 4)
{
//
// ID3V2.4 tag found! check for footer.
//
bool footerFlag = (flagByte & 0x10) == 0x10;
tagInfo.HasFooter = footerFlag;
}
Array.Copy(headerBytes, 6, sizeBytes, 0, 4);
int size = Utils.Convert7BitEncodedToInt32(sizeBytes);
return size;
}
