The emulator community is vigorously using a tape image container format known as TAP for precisely this purpose. Each record from tape is written to file prefixed *and* suffixed by a four-byte record length in little-endian format. A zero- length record is represented by a 4-byte value of zero; although intuition might call for 8-bytes (a prefix & suffix with nothing in between), this is not the case. The convention appears to come directly from FORTRAN 77's handling of unformatted sequential files. And EOF is represented by two consecutive zero-length records.