I am doing my master thesis on wireless networking. I am working on the source code, which the writer of one of the articles provided to me. Initially, I sent him an email and I asked him to send me his C++ source code . So he did. But the problem is, there was no documentation for his code and he is the only one that knows anything about this codebase. As a result, I totally depend on him. Last night I sent him an email and I asked him a question about his code and he replied to me very quickly, only three hours later. Probably, I will need his help again.
Before my last night's email and after spending one month working on his code, I saw minor progress to my work. But after yesterday's mail and his guidance, my work was significantly accelerated. I will probably need his help again maybe another two or three emails in a week. But I am afraid he will become angry with me for sending him a lot of emails.
So what should I do? Assume you are the source code programmer. Do you think he will become angry about my emails? Or he will be willing to help (since I will cite his article)?