You will fine enough help here and here.
First of all if you want to read the c file, find your answer in the first link. Second of all after opening it from the first step, you should look for types (helping yourself with the second link): bool, int, void, ..., then you will save the line with a getline().
your getline should include the following if your c file is well indent :
- the type (including pointers if any),
- the name of the function,
- the parameters
Then from the first '{' you will find your function implementation. If there is any more loop inside your fonction, you have to count all the '{' in order to know where your function finishes by putting them in a LIFO.
You will have to do this until the end of the doc to know all the functions.