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// +build !windows
/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
*/
// Package rwcancel implements cancelable read/write operations on
// a file descriptor.
package rwcancel
import (
"errors"
"os"
"syscall"
"golang.org/x/sys/unix"
)
type RWCancel struct {
fd int
closingReader *os.File
closingWriter *os.File
}
func NewRWCancel(fd int) (*RWCancel, error) {
err := unix.SetNonblock(fd, true)
if err != nil {
return nil, err
}
rwcancel := RWCancel{fd: fd}
rwcancel.closingReader, rwcancel.closingWriter, err = os.Pipe()
if err != nil {
return nil, err
}
return &rwcancel, nil
}
func RetryAfterError(err error) bool {
return errors.Is(err, syscall.EAGAIN) || errors.Is(err, syscall.EINTR)
}
func (rw *RWCancel) ReadyRead() bool {
closeFd := int32(rw.closingReader.Fd())
pollFds := []unix.PollFd{{Fd: int32(rw.fd), Events: unix.POLLIN}, {Fd: closeFd, Events: unix.POLLIN}}
var err error
for {
_, err = unix.Poll(pollFds, -1)
if err == nil || !RetryAfterError(err) {
break
}
}
if err != nil {
return false
}
if pollFds[1].Revents != 0 {
return false
}
return pollFds[0].Revents != 0
}
func (rw *RWCancel) ReadyWrite() bool {
closeFd := int32(rw.closingReader.Fd())
pollFds := []unix.PollFd{{Fd: int32(rw.fd), Events: unix.POLLOUT}, {Fd: closeFd, Events: unix.POLLOUT}}
var err error
for {
_, err = unix.Poll(pollFds, -1)
if err == nil || !RetryAfterError(err) {
break
}
}
if err != nil {
return false
}
if pollFds[1].Revents != 0 {
return false
}
return pollFds[0].Revents != 0
}
func (rw *RWCancel) Read(p []byte) (n int, err error) {
for {
n, err := unix.Read(rw.fd, p)
if err == nil || !RetryAfterError(err) {
return n, err
}
if !rw.ReadyRead() {
return 0, errors.New("fd closed")
}
}
}
func (rw *RWCancel) Write(p []byte) (n int, err error) {
for {
n, err := unix.Write(rw.fd, p)
if err == nil || !RetryAfterError(err) {
return n, err
}
if !rw.ReadyWrite() {
return 0, errors.New("fd closed")
}
}
}
func (rw *RWCancel) Cancel() (err error) {
_, err = rw.closingWriter.Write([]byte{0})
return
}
func (rw *RWCancel) Close() {
rw.closingReader.Close()
rw.closingWriter.Close()
}
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