private static void AddError(string errorMessage, List <Directory> directories)
{
ErrorDirectory directory = directories.OfType <ErrorDirectory>().FirstOrDefault();
if (directory == null)
{
directories.Add(new ErrorDirectory(errorMessage));
}
else
{
directory.AddError(errorMessage);
}
}
private static Directory?ReadGifExtensionBlock(SequentialReader reader)
{
var extensionLabel = reader.GetByte();
var blockSizeBytes = reader.GetByte();
var blockStartPos = reader.Position;
Directory?directory;
switch (extensionLabel)
{
case 0x01:
{
directory = ReadPlainTextBlock(reader, blockSizeBytes);
break;
}
case 0xf9:
{
directory = ReadControlBlock(reader, blockSizeBytes);
break;
}
case 0xfe:
{
directory = ReadCommentBlock(reader, blockSizeBytes);
break;
}
case 0xff:
{
directory = ReadApplicationExtensionBlock(reader, blockSizeBytes);
break;
}
default:
{
directory = new ErrorDirectory($"Unsupported GIF extension block with type 0x{extensionLabel:X2}.");
break;
}
}
var skipCount = blockStartPos + blockSizeBytes - reader.Position;
if (skipCount > 0)
{
reader.Skip(skipCount);
}
return(directory);
}
private Directory GetCurrentOrErrorDirectory()
{
if (CurrentDirectory != null)
{
return(CurrentDirectory);
}
var error = Directories.OfType <ErrorDirectory>().FirstOrDefault();
if (error != null)
{
return(error);
}
error = new ErrorDirectory();
PushDirectory(error);
return(error);
}