I have stored allegro commpressed file into a datafile as a binary data:
dat game.bin -a 1.map -t BIN -k

when I call:

PACKFILE *f=pack_fopen(data.bin#1.map,"rp");

I dont get the original data(before compression), but the compressed data from the 1.map.

If I only load 1.map, which is not in the datafile, this works nicely:

PACKFILE *f=pack_fopen(1.map,"rp");

Am I doing something bad? How to store the compressed binary data into datafile to be able to read them the same way as they are not in datafile?

What you describe looks odd and it might be a bug, I'm not sure. I have a feeling it probably is (Allegro seems not to pick up the compressed flag for the embedded object, but take it from the parent datafile - I think one could argue that this is the expected behavior, but I think one could also argue that it is a bug).

Either way, it should work if you include the uncompressed data in a datafile and then compress the datafile.

It's a bug then. It looks to me that pack_fopen() ignores the "p" flag in the second parameter when the file is in a datafile.