// Copyright 2013 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. // +build darwin dragonfly freebsd netbsd openbsd package runtime // Integrated network poller (kqueue-based implementation). import "unsafe" func kqueue() int32 //go:noescapefunc kevent(kq int32, ch *keventt, nch int32, ev *keventt, nev int32, ts *timespec) int32func closeonexec(fd int32) var (	kq int32 = -1) func netpollinit() {	kq = kqueue()	if kq < 0 {		println("netpollinit: kqueue failed with", -kq)		throw("netpollinit: kqueue failed")	}	closeonexec(kq)} func netpollopen(fd uintptr, pd *pollDesc) int32 {	// Arm both EVFILT_READ and EVFILT_WRITE in edge-triggered mode (EV_CLEAR)	// for the whole fd lifetime.  The notifications are automatically unregistered	// when fd is closed.	var ev [2]keventt	*(*uintptr)(unsafe.Pointer(&ev[0].ident)) = fd	ev[0].filter = _EVFILT_READ	ev[0].flags = _EV_ADD | _EV_CLEAR	ev[0].fflags = 0	ev[0].data = 0	ev[0].udata = (*byte)(unsafe.Pointer(pd))	ev[1] = ev[0]	ev[1].filter = _EVFILT_WRITE	n := kevent(kq, &ev[0], 2, nil, 0, nil)	if n < 0 {		return -n	}	return 0} func netpollclose(fd uintptr) int32 {	// Don't need to unregister because calling close()	// on fd will remove any kevents that reference the descriptor.	return 0} func netpollarm(pd *pollDesc, mode int) {	throw("unused")} // Polls for ready network connections.// Returns list of goroutines that become runnable.func netpoll(block bool) *g {	if kq == -1 {		return nil	}	var tp *timespec	var ts timespec	if !block {		tp = &ts	}	var events [64]keventtretry:	n := kevent(kq, nil, 0, &events[0], int32(len(events)), tp)	if n < 0 {		if n != -_EINTR {			println("runtime: kevent on fd", kq, "failed with", -n)			throw("kevent failed")		}		goto retry	}	var gp guintptr	for i := 0; i < int(n); i++ {		ev := &events[i]		var mode int32		if ev.filter == _EVFILT_READ {			mode += 'r'		}		if ev.filter == _EVFILT_WRITE {			mode += 'w'		}		if mode != 0 {			netpollready(&gp, (*pollDesc)(unsafe.Pointer(ev.udata)), mode)		}	}	if block && gp == 0 {		goto retry	}	return gp.ptr()}