I'd suggest dividing the problem into parts. A: reading of a single record; B: writing the modified record; ...

Most of the difficulty is in the reading part, and we cannot really offer you much advice without learning all the details about the file format. Is the record of arbitrary length? Can a single record span megabytes? Is the record size encoded in the header?

Update: May a record contain "HDR" or "FTR" in its body (as a substring)?

In reply to Re: header footer by oiskuu
in thread header footer by gupr1980

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