...and convert all calls to syscall.{Fallocate,Openat} to syscallcompat . Both syscalls are not available on OSX. We emulate Openat and just return EOPNOTSUPP for Fallocate.
Mode=0 (default) and mode=1 (keep size) are supported. The patch includes test cases and the whole thing passed xfstests. Fixes https://github.com/rfjakob/gocryptfs/issues/1 .
These are large complicated implementations that will share some code.