How do you find the line number of a string in a byte array?

Question

What I'm trying to find:

• A function definition within a code file.

Information I have:

• Code file.
• The byte index of where the function definition starts in the code file and length in bytes.

How should I go about finding this function's line number in the file?

My current thoughts:

• Read code file as byte array
• Find function inside byte array by using start index and length for end.
• Convert this function from binary to text.
• Convert whole code file from binary to text.
• Number the lines in the text.
• Pattern match to find where the function is in the text and return line number.

I'm using Golang for the back-end service which I believe will execute this functionality. Though I also have a front-end in JavaScript which I can leverage to help if needed.

Answer 1

Would something like counting newline characters be good enough, or are you looking into something more tweaky?

You could just start counting newlines \n until you reach the byte index. The line number is the number of newline characters.

Answer 2

Assuming that you have the contents of the file p as type []byte and the byte index of the function as int i , then bytes.Count(p[:i], []byte{'\n'}) + 1 returns the line number for the function.