include "sys.m";
sys := load Sys Sys->PATH;

export:   fn(fd: ref FD, dir: string, flag: int):   int;

Commonly, export's first argument is a file descriptor open on the data file in the dir of a Connection returned by listen (see sys-dial(2)). Before calling export, the connection on fd can optionally be authenticated and set for encryption or digesting using the functions in security-auth(2).

The export function takes two mutually exclusive flags:

Sys->EXPWAIT

Export blocks until all client requests are complete.

Sys->EXPASYNC

Client requests are handled by a background (kernel) process. Export returns immediately. The serving process terminates when the client hangs up.

exportdir(fd: ref Sys->FD, dir: string, pid: chan of int)
{
	pid <-= sys->pctl(Sys->FORKNS|Sys->FORKENV|Sys->NEWFD, fd.fd :: nil);
	sys->export(fd, dir, Sys->EXPWAIT);
}

The FORKNS given to pctl forks the name space, and prevents the sys->export from seeing the effects of subsequent mounts by the process that calls or spawns exportdir. The exportdir function above might be called using:

pid := chan of int;
spawn export(fd, "/", pid);
expid := <-pid;

Service will stop automatically when the connection fd returns end-of-file (eg, when it hangs up), but it can also be stopped locally by killing expid.