prevToken = null;
        while (true) {
            if (ch != -1) {
                ch = readCharFromBuffer();
            }
            if (ch == -1) {
                break;
            } else if (!isDelimiter(ch)) {
                block.append((char) ch);
            } else if (block.length() > 0) {
                break;
            } else {
                blkStart++;
            }
        }