Question

I need to do some operations in the middle of a binary file (change string value, boolean or int32) and leave everything else as it was. How can I quickly skip items I don’t need to work with and get right to what I need without processing every binary object (there are many of them and it’s slow)?

Answer 1

This entirely depends on the structure of your file. Indeed, whether or not you can change a value will depend on the structure of the file – if you need to make a change which would make the file larger or smaller, you’re likely to need to create a new file, as you can’t just insert or delete bytes from the middle of a file.

If your file has a fixed-length record format, you can skip to the right place by seeking, e.g. using the Stream.Position property. If your file doesn’t have a fixed-length format, you may need to process everything fully. An “in-between” possibility exists where each record is length-prefixed: you wouldn’t need to actually process everything, but you’d still need to read the header for each record, to skip through it.