My best advice is that you read and store the data character by character until you reach a CrLf. Then you know you have one line and the first few characters - up to the first space - will be the index number.
Repeat until you get to the index number you want.
You could do it a bit smarter by just reading looking for a CrLf and the reading the next few bytes to check the index number. If you don't want that record and if you know there is a minimum length of record you could possibly speed the process a bit by skipping that number of bytes before starting the search for CrLf. But it's a bit hard to explain exactly how to do that in a few words.
Main task of project - compare the performance of different algorithms for searching for a way to obtain the map position of the robot from GPS / Glonass
I don't think you have told us this before. What is that about? What are you planning to compare?
It's hard to give useful advice when we only see part of the picture.
...R