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using System;
using System.IO;
using System.Text;
namespace Tango.AnimatedGif.Decoding
{
// label 0xFF
internal class GifApplicationExtension : GifExtension
{
internal const int ExtensionLabel = 0xFF;
public int BlockSize { get; private set; }
public string ApplicationIdentifier { get; private set; }
public byte[] AuthenticationCode { get; private set; }
public byte[] Data { get; private set; }
private GifApplicationExtension()
{
}
internal override GifBlockKind Kind
{
get { return GifBlockKind.SpecialPurpose; }
}
internal static GifApplicationExtension ReadApplication(Stream stream)
{
var ext = new GifApplicationExtension();
ext.Read(stream);
return ext;
}
private void Read(Stream stream)
{
// Note: at this point, the label (0xFF) has already been read
byte[] bytes = new byte[12];
stream.ReadAll(bytes, 0, bytes.Length);
BlockSize = bytes[0]; // should always be 11
if (BlockSize != 11)
throw GifHelpers.InvalidBlockSizeException("Application Extension", 11, BlockSize);
ApplicationIdentifier = Encoding.ASCII.GetString(bytes, 1, 8);
byte[] authCode = new byte[3];
Array.Copy(bytes, 9, authCode, 0, 3);
AuthenticationCode = authCode;
Data = GifHelpers.ReadDataBlocks(stream, false);
}
}
}
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