1 files changed, 255 insertions, 0 deletions
diff --git a/src/runtime/netpoll_wasip1.go b/src/runtime/netpoll_wasip1.go
new file mode 100644
index 0000000..9903726
--- /dev/null
+++ b/src/runtime/netpoll_wasip1.go
@@ -0,0 +1,255 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build wasip1
+
+package runtime
+
+import "unsafe"
+
+// WASI network poller.
+//
+// WASI preview 1 includes a poll_oneoff host function that behaves similarly
+// to poll(2) on Linux. Like poll(2), poll_oneoff is level triggered. It
+// accepts one or more subscriptions to FD read or write events.
+//
+// Major differences to poll(2):
+// - the events are not written to the input entries (like pollfd.revents), and
+//   instead are appended to a separate events buffer. poll_oneoff writes zero
+//   or more events to the buffer (at most one per input subscription) and
+//   returns the number of events written. Although the index of the
+//   subscriptions might not match the index of the associated event in the
+//   events buffer, both the subscription and event structs contain a userdata
+//   field and when a subscription yields an event the userdata fields will
+//   match.
+// - there's no explicit timeout parameter, although a time limit can be added
+//   by using "clock" subscriptions.
+// - each FD subscription can either be for a read or a write, but not both.
+//   This is in contrast to poll(2) which accepts a mask with POLLIN and
+//   POLLOUT bits, allowing for a subscription to either, neither, or both
+//   reads and writes.
+//
+// Since poll_oneoff is similar to poll(2), the implementation here was derived
+// from netpoll_aix.go.
+
+const _EINTR = 27
+
+var (
+	evts []event
+	subs []subscription
+	pds  []*pollDesc
+	mtx  mutex
+)
+
+func netpollinit() {
+	// Unlike poll(2), WASI's poll_oneoff doesn't accept a timeout directly. To
+	// prevent it from blocking indefinitely, a clock subscription with a
+	// timeout field needs to be submitted. Reserve a slot here for the clock
+	// subscription, and set fields that won't change between poll_oneoff calls.
+
+	subs = make([]subscription, 1, 128)
+	evts = make([]event, 0, 128)
+	pds = make([]*pollDesc, 0, 128)
+
+	timeout := &subs[0]
+	eventtype := timeout.u.eventtype()
+	*eventtype = eventtypeClock
+	clock := timeout.u.subscriptionClock()
+	clock.id = clockMonotonic
+	clock.precision = 1e3
+}
+
+func netpollIsPollDescriptor(fd uintptr) bool {
+	return false
+}
+
+func netpollopen(fd uintptr, pd *pollDesc) int32 {
+	lock(&mtx)
+
+	// We don't worry about pd.fdseq here,
+	// as mtx protects us from stale pollDescs.
+
+	pds = append(pds, pd)
+
+	// The 32-bit pd.user field holds the index of the read subscription in the
+	// upper 16 bits, and index of the write subscription in the lower bits.
+	// A disarmed=^uint16(0) sentinel is used to represent no subscription.
+	// There is thus a maximum of 65535 total subscriptions.
+	pd.user = uint32(disarmed)<<16 | uint32(disarmed)
+
+	unlock(&mtx)
+	return 0
+}
+
+const disarmed = 0xFFFF
+
+func netpollarm(pd *pollDesc, mode int) {
+	lock(&mtx)
+
+	var s subscription
+
+	s.userdata = userdata(uintptr(unsafe.Pointer(pd)))
+
+	fdReadwrite := s.u.subscriptionFdReadwrite()
+	fdReadwrite.fd = int32(pd.fd)
+
+	ridx := int(pd.user >> 16)
+	widx := int(pd.user & 0xFFFF)
+
+	if (mode == 'r' && ridx != disarmed) || (mode == 'w' && widx != disarmed) {
+		unlock(&mtx)
+		return
+	}
+
+	eventtype := s.u.eventtype()
+	switch mode {
+	case 'r':
+		*eventtype = eventtypeFdRead
+		ridx = len(subs)
+	case 'w':
+		*eventtype = eventtypeFdWrite
+		widx = len(subs)
+	}
+
+	if len(subs) == disarmed {
+		throw("overflow")
+	}
+
+	pd.user = uint32(ridx)<<16 | uint32(widx)
+
+	subs = append(subs, s)
+	evts = append(evts, event{})
+
+	unlock(&mtx)
+}
+
+func netpolldisarm(pd *pollDesc, mode int32) {
+	switch mode {
+	case 'r':
+		removesub(int(pd.user >> 16))
+	case 'w':
+		removesub(int(pd.user & 0xFFFF))
+	case 'r' + 'w':
+		removesub(int(pd.user >> 16))
+		removesub(int(pd.user & 0xFFFF))
+	}
+}
+
+func removesub(i int) {
+	if i == disarmed {
+		return
+	}
+	j := len(subs) - 1
+
+	pdi := (*pollDesc)(unsafe.Pointer(uintptr(subs[i].userdata)))
+	pdj := (*pollDesc)(unsafe.Pointer(uintptr(subs[j].userdata)))
+
+	swapsub(pdi, i, disarmed)
+	swapsub(pdj, j, i)
+
+	subs = subs[:j]
+}
+
+func swapsub(pd *pollDesc, from, to int) {
+	if from == to {
+		return
+	}
+	ridx := int(pd.user >> 16)
+	widx := int(pd.user & 0xFFFF)
+	if ridx == from {
+		ridx = to
+	} else if widx == from {
+		widx = to
+	}
+	pd.user = uint32(ridx)<<16 | uint32(widx)
+	if to != disarmed {
+		subs[to], subs[from] = subs[from], subs[to]
+	}
+}
+
+func netpollclose(fd uintptr) int32 {
+	lock(&mtx)
+	for i := 0; i < len(pds); i++ {
+		if pds[i].fd == fd {
+			netpolldisarm(pds[i], 'r'+'w')
+			pds[i] = pds[len(pds)-1]
+			pds = pds[:len(pds)-1]
+			break
+		}
+	}
+	unlock(&mtx)
+	return 0
+}
+
+func netpollBreak() {}
+
+func netpoll(delay int64) (gList, int32) {
+	lock(&mtx)
+
+	// If delay >= 0, we include a subscription of type Clock that we use as
+	// a timeout. If delay < 0, we omit the subscription and allow poll_oneoff
+	// to block indefinitely.
+	pollsubs := subs
+	if delay >= 0 {
+		timeout := &subs[0]
+		clock := timeout.u.subscriptionClock()
+		clock.timeout = uint64(delay)
+	} else {
+		pollsubs = subs[1:]
+	}
+
+	if len(pollsubs) == 0 {
+		unlock(&mtx)
+		return gList{}, 0
+	}
+
+	evts = evts[:len(pollsubs)]
+	for i := range evts {
+		evts[i] = event{}
+	}
+
+retry:
+	var nevents size
+	errno := poll_oneoff(unsafe.Pointer(&pollsubs[0]), unsafe.Pointer(&evts[0]), uint32(len(pollsubs)), unsafe.Pointer(&nevents))
+	if errno != 0 {
+		if errno != _EINTR {
+			println("errno=", errno, " len(pollsubs)=", len(pollsubs))
+			throw("poll_oneoff failed")
+		}
+		// If a timed sleep was interrupted, just return to
+		// recalculate how long we should sleep now.
+		if delay > 0 {
+			unlock(&mtx)
+			return gList{}, 0
+		}
+		goto retry
+	}
+
+	var toRun gList
+	delta := int32(0)
+	for i := 0; i < int(nevents); i++ {
+		e := &evts[i]
+		if e.typ == eventtypeClock {
+			continue
+		}
+
+		hangup := e.fdReadwrite.flags&fdReadwriteHangup != 0
+		var mode int32
+		if e.typ == eventtypeFdRead || e.error != 0 || hangup {
+			mode += 'r'
+		}
+		if e.typ == eventtypeFdWrite || e.error != 0 || hangup {
+			mode += 'w'
+		}
+		if mode != 0 {
+			pd := (*pollDesc)(unsafe.Pointer(uintptr(e.userdata)))
+			netpolldisarm(pd, mode)
+			pd.setEventErr(e.error != 0, 0)
+			delta += netpollready(&toRun, pd, mode)
+		}
+	}
+
+	unlock(&mtx)
+	return toRun, delta
+}