## several io bindings alive at once, and unbinding one from the middle
##
## Each sem-signal-on-input adds an entry to the VM's io tuple array; removing
## one compacts the gap by migrating the last entry into the freed slot, which
## has to fix up the moved semaphore's recorded index. Nothing exercises that
## unless two or more bindings exist simultaneously - a single binding always
## occupies the last slot and compaction is a no-op.
##
## The children finish in a known order, so the semaphore each wait answers is
## predictable, and a mixed-up index shows as the wrong semaphore or a read
## that finds nothing.

fun chk(ok msg) {
	if ok { printf "OK: %s\n" msg } \
	else { printf "ERROR: %s\n" msg }
}

sg  := (core.semgr-new)
sa  := (core.sem-new)
sb  := (core.sem-new)
sc  := (core.sem-new)
tmo := (core.sem-new)
core.semgr-add sg sa
core.semgr-add sg sb
core.semgr-add sg sc
core.semgr-add sg tmo

## staggered so the completion order is a, then b, then c
pa := (sys.popen "sleep 0.2; echo aaa" "r")
pb := (sys.popen "sleep 0.5; echo bbb" "r")
pc := (sys.popen "sleep 0.8; echo ccc" "r")

ha := (core.basicAt pa 2)
hb := (core.basicAt pb 2)
hc := (core.basicAt pc 2)

## all three bound at the same time - three live tuple entries
core.sem-signal-on-input sa ha
core.sem-signal-on-input sb hb
core.sem-signal-on-input sc hc
core.sem-signal tmo 9 0

fun expect(want h name) {
	| s buf got |
	s := (core.semgr-wait sg)
	chk (eqv? s want) name
	buf := (core.basicNew ByteArray 8)
	got := (sys.read h buf)
	chk (== got 4) "the woken handle carried its child's bytes"
}

## unbinding sa frees the first slot, so the last entry migrates into it and
## sb/sc must still resolve to their own handles afterwards
expect sa ha "the first child woke its own semaphore"
core.sem-unsignal sa

expect sb hb "the second child woke its own semaphore after compaction"
core.sem-unsignal sb

expect sc hc "the third child woke its own semaphore after compaction"
core.sem-unsignal sc

core.sem-unsignal tmo
sys.pclose (core.basicAt pa 0)
sys.pclose (core.basicAt pb 0)
sys.pclose (core.basicAt pc 0)