I have text like this:

> 
> This is a sample {text}. I want to inform my {Dada} that I have some
>  data which is {not useful}. So I need data to start by { and ends with
>  }. This data needs to {find out}.
> 
> 
> 

Total text have some substrings separated within curly braces `{}`. How can I find the starting position and length of the substring starting with `{` and ending with `}`? Further, I will replace the substring with the processed string.