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// Copyright 2009 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.
// Waiting for FDs via epoll(7).
package net
import (
"os"
"syscall"
)
const (
readFlags = syscall.EPOLLIN | syscall.EPOLLRDHUP
writeFlags = syscall.EPOLLOUT
)
type pollster struct {
epfd int
// Events we're already waiting for
// Must hold pollServer lock
events map[int]uint32
// An event buffer for EpollWait.
// Used without a lock, may only be used by WaitFD.
waitEventBuf [10]syscall.EpollEvent
waitEvents []syscall.EpollEvent
// An event buffer for EpollCtl, to avoid a malloc.
// Must hold pollServer lock.
ctlEvent syscall.EpollEvent
}
func newpollster() (p *pollster, err error) {
p = new(pollster)
if p.epfd, err = syscall.EpollCreate1(syscall.EPOLL_CLOEXEC); err != nil {
if err != syscall.ENOSYS {
return nil, os.NewSyscallError("epoll_create1", err)
}
// The arg to epoll_create is a hint to the kernel
// about the number of FDs we will care about.
// We don't know, and since 2.6.8 the kernel ignores it anyhow.
if p.epfd, err = syscall.EpollCreate(16); err != nil {
return nil, os.NewSyscallError("epoll_create", err)
}
syscall.CloseOnExec(p.epfd)
}
p.events = make(map[int]uint32)
return p, nil
}
func (p *pollster) AddFD(fd int, mode int, repeat bool) (bool, error) {
// pollServer is locked.
var already bool
p.ctlEvent.Fd = int32(fd)
p.ctlEvent.Events, already = p.events[fd]
if !repeat {
p.ctlEvent.Events |= syscall.EPOLLONESHOT
}
if mode == 'r' {
p.ctlEvent.Events |= readFlags
} else {
p.ctlEvent.Events |= writeFlags
}
var op int
if already {
op = syscall.EPOLL_CTL_MOD
} else {
op = syscall.EPOLL_CTL_ADD
}
if err := syscall.EpollCtl(p.epfd, op, fd, &p.ctlEvent); err != nil {
return false, os.NewSyscallError("epoll_ctl", err)
}
p.events[fd] = p.ctlEvent.Events
return false, nil
}
func (p *pollster) StopWaiting(fd int, bits uint) {
// pollServer is locked.
events, already := p.events[fd]
if !already {
// The fd returned by the kernel may have been
// cancelled already; return silently.
return
}
// If syscall.EPOLLONESHOT is not set, the wait
// is a repeating wait, so don't change it.
if events&syscall.EPOLLONESHOT == 0 {
return
}
// Disable the given bits.
// If we're still waiting for other events, modify the fd
// event in the kernel. Otherwise, delete it.
events &= ^uint32(bits)
if int32(events)&^syscall.EPOLLONESHOT != 0 {
p.ctlEvent.Fd = int32(fd)
p.ctlEvent.Events = events
if err := syscall.EpollCtl(p.epfd, syscall.EPOLL_CTL_MOD, fd, &p.ctlEvent); err != nil {
print("Epoll modify fd=", fd, ": ", err.Error(), "\n")
}
p.events[fd] = events
} else {
if err := syscall.EpollCtl(p.epfd, syscall.EPOLL_CTL_DEL, fd, nil); err != nil {
print("Epoll delete fd=", fd, ": ", err.Error(), "\n")
}
delete(p.events, fd)
}
}
func (p *pollster) DelFD(fd int, mode int) {
// pollServer is locked.
if mode == 'r' {
p.StopWaiting(fd, readFlags)
} else {
p.StopWaiting(fd, writeFlags)
}
// Discard any queued up events.
i := 0
for i < len(p.waitEvents) {
if fd == int(p.waitEvents[i].Fd) {
copy(p.waitEvents[i:], p.waitEvents[i+1:])
p.waitEvents = p.waitEvents[:len(p.waitEvents)-1]
} else {
i++
}
}
}
func (p *pollster) WaitFD(s *pollServer, nsec int64) (fd int, mode int, err error) {
for len(p.waitEvents) == 0 {
var msec int = -1
if nsec > 0 {
msec = int((nsec + 1e6 - 1) / 1e6)
}
s.Unlock()
n, err := syscall.EpollWait(p.epfd, p.waitEventBuf[0:], msec)
s.Lock()
if err != nil {
if err == syscall.EAGAIN || err == syscall.EINTR {
continue
}
return -1, 0, os.NewSyscallError("epoll_wait", err)
}
if n == 0 {
return -1, 0, nil
}
p.waitEvents = p.waitEventBuf[0:n]
}
ev := &p.waitEvents[0]
p.waitEvents = p.waitEvents[1:]
fd = int(ev.Fd)
if ev.Events&writeFlags != 0 {
p.StopWaiting(fd, writeFlags)
return fd, 'w', nil
}
if ev.Events&readFlags != 0 {
p.StopWaiting(fd, readFlags)
return fd, 'r', nil
}
// Other events are error conditions - wake whoever is waiting.
events, _ := p.events[fd]
if events&writeFlags != 0 {
p.StopWaiting(fd, writeFlags)
return fd, 'w', nil
}
p.StopWaiting(fd, readFlags)
return fd, 'r', nil
}
func (p *pollster) Close() error {
return os.NewSyscallError("close", syscall.Close(p.epfd))
}
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