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Source file src/runtime/netpoll_epoll.go

  // 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 linux
  
  package runtime
  
  import "unsafe"
  
  func epollcreate(size int32) int32
  func epollcreate1(flags int32) int32
  
  //go:noescape
  func epollctl(epfd, op, fd int32, ev *epollevent) int32
  
  //go:noescape
  func epollwait(epfd int32, ev *epollevent, nev, timeout int32) int32
  func closeonexec(fd int32)
  
  var (
  	epfd int32 = -1 // epoll descriptor
  )
  
  func netpollinit() {
  	epfd = epollcreate1(_EPOLL_CLOEXEC)
  	if epfd >= 0 {
  		return
  	}
  	epfd = epollcreate(1024)
  	if epfd >= 0 {
  		closeonexec(epfd)
  		return
  	}
  	println("netpollinit: failed to create epoll descriptor", -epfd)
  	throw("netpollinit: failed to create descriptor")
  }
  
  func netpollopen(fd uintptr, pd *pollDesc) int32 {
  	var ev epollevent
  	ev.events = _EPOLLIN | _EPOLLOUT | _EPOLLRDHUP | _EPOLLET
  	*(**pollDesc)(unsafe.Pointer(&ev.data)) = pd
  	return -epollctl(epfd, _EPOLL_CTL_ADD, int32(fd), &ev)
  }
  
  func netpollclose(fd uintptr) int32 {
  	var ev epollevent
  	return -epollctl(epfd, _EPOLL_CTL_DEL, int32(fd), &ev)
  }
  
  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 epfd == -1 {
  		return nil
  	}
  	waitms := int32(-1)
  	if !block {
  		waitms = 0
  	}
  	var events [128]epollevent
  retry:
  	n := epollwait(epfd, &events[0], int32(len(events)), waitms)
  	if n < 0 {
  		if n != -_EINTR {
  			println("runtime: epollwait on fd", epfd, "failed with", -n)
  			throw("epollwait failed")
  		}
  		goto retry
  	}
  	var gp guintptr
  	for i := int32(0); i < n; i++ {
  		ev := &events[i]
  		if ev.events == 0 {
  			continue
  		}
  		var mode int32
  		if ev.events&(_EPOLLIN|_EPOLLRDHUP|_EPOLLHUP|_EPOLLERR) != 0 {
  			mode += 'r'
  		}
  		if ev.events&(_EPOLLOUT|_EPOLLHUP|_EPOLLERR) != 0 {
  			mode += 'w'
  		}
  		if mode != 0 {
  			pd := *(**pollDesc)(unsafe.Pointer(&ev.data))
  
  			netpollready(&gp, pd, mode)
  		}
  	}
  	if block && gp == 0 {
  		goto retry
  	}
  	return gp.ptr()
  }
  

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