FileStream.Read(...): Will I ever get a nibble rather than byte?

Question

Hi All,

I'm doing a number of bitwise operations on an array of bytes in C#. I'm obtaining the array by calling FileStream.Read. I just realized that I'm not sure what would happen if a file had a bad byte or corrupt byte in it somewhere. For example, maybe a nibble is chopped off of the end or something like that. What would the FileStream do with it? Would the messed up byte by 'rounded' off by the Read method? Would an exception be thrown? Or is this something that will virtually never happen?

Thanks, brian

Answer 1

If your FileStream.Read call succeeds, there's no such thing as a file having a bad byte or corrupt byte. Each byte that is successfully read, and part of the file, is a value from 0 to 255. How it is interpreted by a program is what matters.

If FileStream.Read returns for example 5 bytes, then you can rely that those 5 bytes are read successfully from the file and all bits of the bytes were put into your buffer successfully.

There is such thing though for example as a bad cluster on your hard disk, in which case your Read would fail with some kind of exception.

For completeness I should also mention that every file type has a file format. I.e. how you should interpret the binary data. It is possible that a byte or several bytes don't follow the file format. And in that way you can view a byte as being corrupt or invalid, but it's not really corrupt or invalid just wrong in terms of what the file format specifies.