internal static async Task<TagHeader> ReadTagHeader(Stream stream)
{
var header = new TagHeader();
byte[] headerBytes = ArrayPool<byte>.Shared.Rent(7);
await stream.ReadAsync(headerBytes, 0, 7).ConfigureAwait(false);
switch (Convert.ToInt32(headerBytes[0]))
{
case 2:
header.Version = TagVersion.V22;
break;
case 3:
header.Version = TagVersion.V23;
break;
case 4:
header.Version = TagVersion.V24;
break;
default:
header.Version = TagVersion.Unknown;
break;
}
header.Unsynchronization = ((headerBytes[2] & 0x80) == 0x80);
header.ExtendedHeader = ((headerBytes[2] & 0x40) == 0x40);
header.Experimental = ((headerBytes[2] & 0x20) == 0x20);
header.HasFooter = ((headerBytes[2] & 0x10) == 0x10);
header.TagLength = headerBytes[3] * 128 * 128 * 128 + headerBytes[4] * 128 * 128 + headerBytes[5] * 128 + headerBytes[6];
ArrayPool<byte>.Shared.Return(headerBytes);
return header;
}
internal static async Task <TagHeader> ReadTagHeader(Stream stream)
{
var header = new TagHeader();
byte[] headerBytes = ArrayPool <byte> .Shared.Rent(7);
await stream.ReadAsync(headerBytes, 0, 7).ConfigureAwait(false);
switch (Convert.ToInt32(headerBytes[0]))
{
case 2:
header.Version = TagVersion.V22;
break;
case 3:
header.Version = TagVersion.V23;
break;
case 4:
header.Version = TagVersion.V24;
break;
default:
header.Version = TagVersion.Unknown;
break;
}
header.Unsynchronization = ((headerBytes[2] & 0x80) == 0x80);
header.ExtendedHeader = ((headerBytes[2] & 0x40) == 0x40);
header.Experimental = ((headerBytes[2] & 0x20) == 0x20);
header.HasFooter = ((headerBytes[2] & 0x10) == 0x10);
header.TagLength = headerBytes[3] * 128 * 128 * 128 + headerBytes[4] * 128 * 128 + headerBytes[5] * 128 + headerBytes[6];
ArrayPool <byte> .Shared.Return(headerBytes);
return(header);
}
public static async Task <MP3File> ReadMP3FileAsync(Stream stream)
{
var file = new MP3File();
file.HasId3V2 = (stream.ReadByte() == Constants.ID3Header[0] && stream.ReadByte() == Constants.ID3Header[1] && stream.ReadByte() == Constants.ID3Header[2]);
if (file.HasId3V2)
{
// Let's read the tag header.
file.OriginalTagHeader = await TagHeader.ReadTagHeader(stream).ConfigureAwait(false);
// Let's read the tag frames into a byte array and wrap it into a memorystream.
var tags = ArrayPool <byte> .Shared.Rent(file.OriginalTagHeader.TagLength);
await stream.ReadAsync(tags, 0, file.OriginalTagHeader.TagLength).ConfigureAwait(false);
using (var memoryStream = new MemoryStream(tags, 0, file.OriginalTagHeader.TagLength))
{
// Let's read the tag.
switch (file.OriginalTagHeader.Version)
{
case TagVersion.V22:
break;
case TagVersion.V23:
file.Tag = await Tag23Factory.FromStream(memoryStream, file.OriginalTagHeader.TagLength).ConfigureAwait(false);
break;
case TagVersion.V24:
//Tag = Tag24Factory.FromBytes(tagBytes);
break;
case TagVersion.Unknown:
break;
}
}
ArrayPool <byte> .Shared.Return(tags);
}
else // No ID3v2 Tag so the Mpeg Frames presumably start at the beginning but let's make sure though
{
stream.Seek(0, SeekOrigin.Begin);
}
// Now let's find the MPEG frames, seek until we find the first 0xFF byte that
// should be part of the first Mpeg frame.
while (stream.Position < stream.Length && stream.ReadByte() != 0xFF)
{
if (stream.ReadByte() >= 0xE0)
{
stream.Seek(-2, SeekOrigin.Current);
break;
}
}
// We should be at the first MPEG frame
file.MpegStart = (int)stream.Position;
//Let's see if this file has an ID3v1 tag
stream.Seek(-128, SeekOrigin.End);
if (stream.ReadByte() == 0x54 && stream.ReadByte() == 0x41 && stream.ReadByte() == 0x47)
{
// yup, the MPEG frames end at File.Length - 128 bytes
// we've read 3 bytes to see if the ID3v1 tag is present so the MPEG frames ended 3 bytes ago
file.MpegEnd = (int)stream.Position - 3;
}
else
{
// nope.. no ID3v1 tag is present so the MPEG frames end at the end of the file
file.MpegEnd = (int)stream.Length;
}
return(file);
}
