shithub: mc

ref: 606bce2a5601d6a124da33d007e071ed9d43ff45
dir: /lib/std/wait+plan9.myr/

use sys

use "alloc"
use "chartype"
use "die"
use "extremum"
use "hashfuncs"
use "hasprefix"
use "htab"
use "intparse"
use "option"
use "strsplit"
use "striter"
use "syswrap"
use "utf"
use "sleq"
use "fmt"

pkg std =
	type waitstatus = union
		`Wsuccess
		`Wfailure
		`Wsignalled
		`Waiterror
	;;

	const wait	: (pid : pid -> waitstatus)
;;

var statusinit	: bool = false
var statusmap	: htab(pid, waitstatus)#

const wait = {pid
	var buf : byte[512]
	var xpid, status
	var n

	if !statusinit
		statusmap = mkht(inthash, inteq)
		statusinit = true
	;;
		
	match htget(statusmap, pid)
	| `Some st:
		htdel(statusmap, pid)
		-> st
	| `None:	/* nothing */
	;;

	while true
		n = sys.await(buf[:])
		if n < 0
			-> `Waiterror
		;;

		(status, xpid) = parsestatus(buf[:n])
		if xpid == pid
			-> status
		else
			htput(statusmap, pid, status)
		;;
	;;
	/* impossible */
	-> `Waiterror
}

const parsestatus = {status	-> (waitstatus, pid)
	var st : waitstatus
	var spbuf : byte[:][5]
	var xpid, sp

	sp = bstrsplit(spbuf[:], status, " ")
	if sp.len == 0
		-> (`Wfailure, -1)
	;;

	match intparse(sp[0])
	| `Some pid:
		xpid = pid
		/* exits(nil) => sp[0] either not present or equal to '' */
		if sp.len == 4 || (sp.len == 5 && sleq(sp[4], "''"))
			st = `Wsuccess
		elif sp.len == 5
			st = `Wfailure
		else	/* we have a malformed await message */
			st = `Waiterror
		;;
	| `None:
		xpid = -1
		st = `Waiterror
	;;

	-> (st, xpid)

}