The BufferIn argument turns into various things:
in C const char *, size_t parameter pair
in XDR an opaque<> type (instead of string) which allows \0 chars
in other bindings
mostly just a string, since most languages except for C
permit strings to contain any 8 bit data
truncate, truncate_size: Used to truncate files to a particular
size, or to zero bytes.
mkdir_mode: Like mkdir but allows you to also specify the
initial permissions for the new directory.
utimens: Set timestamp on a file with nanosecond accuracy.
lchown: Corresponding to lchown(2) syscall (we already have chown).
The implementation is complicated by the fact that we had to
add an Int64 parameter type to the generator.
