In our previous episode, Graeme Geldenhuys said: > > In fact deflate/zip is 18-19 years old and there are lot of better > > compression algorithm, like LZX. I think there is one implemented in Pascal > > (ABC if memory don't fails). > > I'm still trying to find a compression algorithm that beats whatever > 7-zip uses. The results are by magnitudes smaller than any other > compression algorithm I have seen. > > The important thing for TZipFile component is that the archive format > must compresses every file separately. Otherwise you can't extract a > specific file without unpacking everything first.
But ZIP is 5-6 times larger than CHM, which can do all this too, and we have the whole software shebang without deps. I was somewhat surprised that bz2 was another 2 times smaller, and according to Eduardo it is possible to extract blocks separately, without changing compression parameters. Then you could index the tar+bz2 (which files in which block + offset in block) by decompressing fully once, and then extract single files. Still, since that adds another index and handling, and a lot of work, chm is working and not too bad. > The other thing is the algorithms need to be free and supporting > Unicode. A compression algorithm is not related to unicode. That's the job of the archive component. >7-zip's LZMA does pass both requirements. I'm just not sure if it > compresses filed separately - I would imagine it can/does. A portable, not overly complex implementation in Pascal is also a requirement IMHO. Not an hard one, but the fact that it is already there for CHM makes it one for an alternative. _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
