@Override
    public final void writeRaw(char c0, char c1) {
        if (c0 > 128 || c1 > 128) {
            throw new JSONException("not support " + c0 + ", " + c1);
        }

        int off = this.off;
        byte[] bytes = this.bytes;
        if (off + 2 > bytes.length) {
            bytes = grow(off + 2);
        }
        bytes[off] = (byte) c0;
        bytes[off + 1] = (byte) c1;
        this.off = off + 2;
    }
A faster alternative that is functionally equivalent to Long.expand(i, 0x0F0F_0F0F_0F0F_0F0FL)
core/src/main/java/com/alibaba/fastjson2/JSONWriterUTF8.java