public boolean markSupported() 
{
            return false;
}

{@inheritDoc}

 public int read() throws IOException 
{
            if (currentOffset <  tiffheader.length)
            {
                return tiffheader[currentOffset++];
            }
            return datastream.read();
}

For simple read, take a byte from the tiffheader array or pass through. {@inheritDoc}

 public int read(byte[] data) throws IOException 
{
            if (currentOffset <  tiffheader.length)
            {
                int length = java.lang.Math.min(tiffheader.length - currentOffset, data.length);
                if (length  > 0)
                {
                    System.arraycopy(tiffheader, currentOffset, data, 0, length);
                }
                currentOffset += length;
                return length;
            }
            else
            {
                return datastream.read(data);
            }
}

For read methods only return as many bytes as we have left in the header if we've exhausted the header, pass through to the InputStream of the raw CCITT data. {@inheritDoc}

 public int read(byte[] data,
    int off,
    int len) throws IOException 
{
            if (currentOffset <  tiffheader.length)
            {
                int length = java.lang.Math.min(tiffheader.length - currentOffset, len);
                if (length  > 0)
                {
                    System.arraycopy(tiffheader, currentOffset, data, off, length);
                }
                currentOffset += length;
                return length;
            }
            else
            {
                return datastream.read(data,off,len);
            }
}

For read methods only return as many bytes as we have left in the header if we've exhausted the header, pass through to the InputStream of the raw CCITT data. {@inheritDoc}

 public  void reset() throws IOException 
{
            throw new IOException("reset not supported");
}

{@inheritDoc}

 public long skip(long n) throws IOException 
{
            if (currentOffset <  tiffheader.length)
            {
                long length = Math.min(tiffheader.length - currentOffset, n);
                currentOffset += length;
                return length;
            }
            else
            {
                return datastream.skip(n);
            }
}

When skipping if any header data not yet read, only allow to skip what we've in the buffer Otherwise just pass through. {@inheritDoc}