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use "die.use"
use "execvp.use"
use "fmt.use"
use "result.use"
use "syswrap.use"

pkg std =
	const spork	: (cmd : byte[:][:]	-> result((pid, fd, fd), int))
	const sporkfd	: (cmd : byte[:][:], infd : fd, outfd : fd	-> result(pid, int))
;;

const spork = {cmd
	var infds  :fd[2], outfds : fd[2]
	var err

	/* open up pipes */
	err = pipe(&infds)
	if err != 0
		-> `Fail (-err castto(int))
	;;
	err = pipe(&outfds)
	if err != 0
		-> `Fail (-err castto(int))
	;;

	match sporkfd(cmd, infds[0] castto(fd), outfds[1] castto(fd))
	| `Ok pid:
		/* close unused fd ends */
		close(infds[0]);
		close(outfds[1]);
		-> `Ok (pid, infds[1], outfds[0])
	| `Fail m:
		-> `Fail m
	;;
}

const sporkfd = {cmd, infd, outfd
	var pid

	pid = fork()
	/* error  */
	if pid == -1
		-> `Fail -1
	/* child */
	elif pid == 0
		/* stdin/stdout for our communication. */
		if dup2(infd castto(fd), 0) != 0
			fatal("unable to set stdin\n")
		;;
		if dup2(outfd castto(fd), 1) != 1
			fatal("unable to set stdout\n")
		;;
		close(infd)
		close(outfd)
		execvp(cmd[0], cmd) < 0
		fatal("failed to exec {}\n", cmd[0])
	/* parent */
	else
		-> `Ok pid
	;;
}