Representation of a C binary file [closed]

Question

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.

Closed 9 years ago.

For a homework assignment I created a simple compression/decompression program that makes use of a naive implementation of run-length encoding. I've gotten my program working; compressing and decompressing any text file with a pretty large number of characters (e.g. the program source) works flawlessly. As an experiment I tried to compress/decompress the binary of the compression program itself. This resulted in a file that was much smaller than the original binary, and is obviously un-runnable. What is causing this data-loss?

My assumption was that it's related to how binary files are represented, but I can't figure much out past that.

Answer 1

Possible issues:

• Your program opens the binary file in the text mode, which damages the '\r' and '\n' bytes
• Your program incorrectly handles zero bytes, treating them as ends of strings ('\0') and not as data of its own
• Your program uses char (that is actually signed char) for the bytes of data and correctly works only with non-negative values, which ASCII chars of English text are, but fails to work with arbitrary char/byte values, which may be negative
• Your program has an overflow somewhere which shows up only on big files
• Your program has some other data-dependent bug

Answer 2

If the platform is linux (as the question is tagged), there's no difference between binary and text modes. So it shouldn't be that; but even so, the files should be opened as binary.

I suspect that your problem is the program treats '\0' characters as terminators (or otherwise specially) instead of as valid data.