Trouble Parsing with Indexof

Question

I am trying to use indexof to parse serial data and extract data between @ and #.

int start = data.IndexOf('@') + 1;
int end = data.IndexOf('#', start);
string result = data.substring (start, end - start -1)

but sometimes the string does not stop at # and I get extra data. What is a good way to effectively filter out everything outside of the @ and #.

Note: If the data being processed is from a pre-existing string, then it works fine. The problem is when the data comes in from a serial port (stream)

Sam Hobbs · Answer

I understand that you don't control the data but you control the program and that is what you need to change to be dynamic and respond gracefully to exceptions.

Telco Joe · Answer

Yes. It will not work with a return of -1. I am unable to control the data that is fed to the program and there are times where there will not be a @ or #.

Sam Hobbs · Answer

In those situations reliability is critical and sloppy programming is futile. It sounds as if exceptions are not exceptional. Audit the data as much as possible. When looking for a @ then check to ensure that one is found. Then check to ensure that a # is found as expected. If there are any other requirements for valid data then check to ensure that the data conforms. The code you posed will not work as expected if IndexOf returns -1 correct?

Telco Joe · Answer

Sometimes just random data will come over the serial port that does not need to be decoded so a stream of various numbers and letters will go through like 123abc456. This is when problems are caused because this data is unfiltered by indexof and an exception comes up at the next part of the program that tries to decode this unwanted data with substrings.

Sam Hobbs · Answer

So is it possible for some lines to not have both?

Telco Joe · Answer

Part of the problem is if data is sent without the @ or # as it gets displayed anyway. I need a sure-fire way to eliminate any other data besides what's between @ and #.

Sam Hobbs · Answer

Investigate why. I see no explanation for it but I don't see the data. Instead of showing the data here you can investigate the problem. Problems such as this usually is caused when we assume something that is not true. So are you sure there is an @ in the records that are a problem and that there is also a # after the @? I suspect that there is not.

Zoran Horvat · Answer

This piece of code alone looks good. I'd say that problem is in the way in which this code is used. Can you post a bit more code to show how variable data is obtained. Also it would be good if you had logged or printed to console input and output strings (data and results) so to catch the case in which result is incorrect. One hint - you haven't checked whether @ and # exist in data or not.