You definitely could. I did it for a proprietary format once. Each item was quite small (typically 100-ish bytes IIRC), and I needed random access. One approac

You definitely could. I did it for a proprietary format once. Each item was quite small (typically 100-ish bytes IIRC), and I needed random access. One approach would have been to split it into pages of a few kilobytes and separately compress those. But on this platform, I/O was primitive and very slow, and the CPU was also extremely slow. So it was advantageous to decompress only the necessary data. So I came up with a rudimentary custom compression algorithm. I scanned all entries for common strings and made a shared dictionary. Each entry was then stored as a sequence of indexes into the shared dictionary. Decompressing an entry was dead simple: read the sequence of dictionary indices and copy from the dictionary to the output. On a side note, the unexpected challenge of this method was how to choose which strings to put in the shared dictionary. I tried a few things and ended up with a heuristic that tries to balance favoring longer strings with favoring frequently occurring strings. I'm sure there are much better ways than that. If I had it to do over, I probably would have gone with the compressed pages approach simply because the implementation would've been done so much quicker. But I think I did achieve faster decompression and a better compression ratio.