ref: e1fdc800bb227e4e4c1a91c6a0586bf1e0b5ef15
dir: /sys/src/cmd/cfs/file.h/
void fmerge(Dptr*, char*, char*, int, int); int fbwrite(Icache*, Ibuf*, char*, ulong, int); long fwrite(Icache*, Ibuf*, char*, ulong, long); Dptr* fpget(Icache*, Ibuf*, ulong); long fread(Icache*, Ibuf*, char*, ulong, long);