@Override

        public int read(byte[] b, int off, int blen) throws IOException {

            int retval = -1;

            if (!eof) {

                boolean isCached = (pos + blen < len);

                if (isCached) {

                    retval = blen;

                } else {

                    int buflen = Math.max(len, blen);

                    buflen = (buflen > 0) ? (buflen * 2) : 256;

                    byte[] buf = new byte[buflen];

                    if (len > 0) {

                        System.arraycopy(buffer, 0, buf, 0, len);

                    }

                    final int reuiredLen = buflen - blen;

                    int c = inputStream.read(buf, len, reuiredLen);

                    buffer = buf;

                    len += (c > 0) ? c : 0;

                    eof = (c < reuiredLen) ? true : false;

                    retval = Math.min(c, blen);

                }

                if (retval > 0) {

                    System.arraycopy(buffer, pos, b, off, retval);

                    pos += retval;

                }                

            }

            return retval;

        }