## sys.pipe and the non-blocking I/O contract

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

p := (sys.pipe)
chk (array? p) "sys.pipe returns an array"
r := (core.basicAt p 0)
w := (core.basicAt p 1)
chk (integer? r) "the read end is a handle id"
chk (integer? w) "the write end is a handle id"
chk (not (= r w)) "the two ends are distinct handles"

buf := (core.basicNew ByteArray 16)

## a pipe with nothing in it must report "would block" rather than stalling
chk (= (sys.read r buf) -1) "reading an empty pipe returns -1 (would block)"

wb := (core.basicNew ByteArray 3)
core.basicAtPut wb 0 97
core.basicAtPut wb 1 98
core.basicAtPut wb 2 99
chk (= (sys.write w wb) 3) "writing to the pipe returns the count"

n := (sys.read r buf)
chk (= n 3) "the data comes back"
chk (= (core.basicAt buf 0) 97) "byte 0 correct"
chk (= (core.basicAt buf 2) 99) "byte 2 correct"
chk (= (sys.read r buf) -1) "the pipe is empty again"

## closing the writer turns the next read into an end-of-file
sys.close w
chk (= (sys.read r buf) 0) "reading after the writer closed returns 0 (eof)"
sys.close r