file type

Question

I am writing a code to transfer files between computers. At the moment when user select a file to upload or download the user also have to select if it is binary or ascii file. So depend on what they select the stream is different. Now I want the code to determine the file type so the user doesn't need to select it by their self. I have checked file class fileinfo class and filesysteminfo class etc. But couldn't find any solution for it. Could anybody give me some advice?

spgilmore · Answer

That's right. You'd have to analyze each byte. If no bytes exceed ASCII limits (32-127?) you could send it as a text file. The good news is that since you're already sending the file you already have to read all the bytes. Just make this determination at that point. As previously stated when writing the client and server ends you can send EVERYTHING as binary and just choose what to do with it on the client end. I assume that the only difference is really whether the content is displayed to the client or saved to disk instead. Is that right? Either one is still possible if you send the file as binary. Data is data.

sjones · Answer

There is no way to do this. Nothing about a file indicates if it contains binary data. Certainly not a file extension. You could guess and say everything ending with .TXT would be text. You could keep your own internal list of extensions that are USUALLY text only. Buy there is no way to be absolutely sure. Some files that look like pure text actually have some binary data mixed in. About the only thing you could do is spin through the file yourself looking at every byte. If you don't find any binary data you know you can send it as text. Are you using FTP to do this? If you are writing both the sender and reciever apps why not just send the file as a stream of bytes and not worry about the contents?