AIFF is just a byte-reversed RIFF (WAV), so if an audio program handles WAV and doesn't handle AIFF, the author is either lazy or a complete moron. Assuming it's a PC program (similar for the Mac, just reversed), it pretty much boils down to one significant line of code:
if (signature== 0x52494646 /*AIFF in hex*/) swap = 1; else swap = 0;
then for each line of code that reads data that needs to be swapped, instead of
uint16_t value = filebuf[whatever];
it becomes something like
uint16_t value = swap ? swap16(filebuf[whatever]) : filebuf[whatever];
or whatever byte swap function you prefer.... But you probably didn't care about that.