private String readUTF(int index, final int utfLen, final char[] buf) {
        int endIndex = index + utfLen;
        byte[] b = this.b;
        int strLen = 0;
        int c;
        int st = 0;
        char cc = 0;
        while (index < endIndex) {
            c = b[index++];
            switch (st) {
            case 0:
                c = c & 0xFF;
                if (c < 0x80) { // 0xxxxxxx
                    buf[strLen++] = (char) c;
                } else if (c < 0xE0 && c > 0xBF) { // 110x xxxx 10xx xxxx
                    cc = (char) (c & 0x1F);
                    st = 1;
                } else { // 1110 xxxx 10xx xxxx 10xx xxxx
                    cc = (char) (c & 0x0F);
                    st = 2;
                }
                break;

            case 1: // byte 2 of 2-byte char or byte 3 of 3-byte char
                buf[strLen++] = (char) ((cc << 6) | (c & 0x3F));
                st = 0;
                break;

            case 2: // byte 2 of 3-byte char
                cc = (char) ((cc << 6) | (c & 0x3F));
                st = 1;
                break;
            }
        }
        return new String(buf, 0, strLen);
    }