ioUtils.copy(in,out)方法中关于缓冲byte[]buffer的问题

内部的缓冲byte[]buffer，定义的大小为4096，如果要写的io流内容超过这个大小呢
贴个源码：

public static int copy(InputStream input, OutputStream output) throws IOException {
    long count = copyLarge(input, output);
    if (count > Integer.MAX_VALUE) {
        return -1;
    }
    return (int) count;
}
public static long copyLarge(InputStream input, OutputStream output)
        throws IOException {
    return copyLarge(input, output, new byte[DEFAULT_BUFFER_SIZE]);//大小为4096
}
public static long copyLarge(InputStream input, OutputStream output, byte[] buffer)
        throws IOException {
    long count = 0;
    int n = 0;
    while (EOF != (n = input.read(buffer))) {
        output.write(buffer, 0, n);
        count += n;
    }
    return count;
}

也没看见对buffer有什么别的处理呀？如果buffer大小不够呢？