core/src/main/java/org/nanohttpd/protocols/http/response/Response.java
public static Response newFixedLengthResponse(IStatus status, String mimeType, InputStream data, long totalBytes) {
        return new Response(status, mimeType, data, totalBytes);
    }
public static Response newFixedLengthResponse(IStatus status, String mimeType, InputStream data, long totalBytes) {
        return new Response(status, mimeType, data, totalBytes);
    }
Create a response with known length.