protected override Block ReadNextInternal()
{
try
{
var bytes = new byte[FullHeaderLength];
File.Read(bytes, 0, bytes.Length);
// check extra field bit
if ((bytes[3] & (byte)GZipFlags.ExtraFieldPresent) == 0)
{
throw new InvalidOperationException(StringsHelper.EmptyExtraFieldFlag());
}
// check extra field length
var extraFieldLength = BitConverter.ToInt16(new ReadOnlySpan <byte>(bytes, 10, 2));
if (extraFieldLength != sizeof(int))
{
throw new InvalidOperationException(StringsHelper.InvalidExtraFieldLength());
}
// get block size from extra field
var blockLength = BitConverter.ToInt32(new ReadOnlySpan <byte>(bytes, 12, extraFieldLength));
var oldBytesLength = bytes.Length;
Array.Resize(ref bytes, bytes.Length + blockLength);
File.Read(bytes, oldBytesLength, blockLength);
return(new Block(bytes));
}
catch (Exception e)
{
throw new InvalidOperationException(StringsHelper.UnsupportedCompressedFile(), e);
}
}