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package helper
import (
"flag"
"fmt"
"io"
"os"
"strconv"
"syscall"
)
// InternalHelperStub is an internal function but exported because it is cross-package;
// it is part of the implementation of the helper stub.
func InternalHelperStub() {
// this test mocks the helper process
var ap, sp string
if v, ok := os.LookupEnv(HakureiHelper); !ok {
return
} else {
ap = v
}
if v, ok := os.LookupEnv(HakureiStatus); !ok {
panic(HakureiStatus)
} else {
sp = v
}
genericStub(flagRestoreFiles(1, ap, sp))
os.Exit(0)
}
func newFile(fd int, name, p string) *os.File {
present := false
switch p {
case "0":
case "1":
present = true
default:
panic(fmt.Sprintf("%s fd has unexpected presence value %q", name, p))
}
f := os.NewFile(uintptr(fd), name)
if !present && f != nil {
panic(fmt.Sprintf("%s fd set but not present", name))
}
if present && f == nil {
panic(fmt.Sprintf("%s fd preset but unset", name))
}
return f
}
func flagRestoreFiles(offset int, ap, sp string) (argsFile, statFile *os.File) {
argsFd := flag.Int("args", -1, "")
statFd := flag.Int("fd", -1, "")
_ = flag.CommandLine.Parse(os.Args[offset:])
argsFile = newFile(*argsFd, "args", ap)
statFile = newFile(*statFd, "stat", sp)
return
}
func genericStub(argsFile, statFile *os.File) {
if argsFile != nil {
// this output is checked by parent
if _, err := io.Copy(os.Stdout, argsFile); err != nil {
panic("cannot read args: " + err.Error())
}
}
if statFile != nil {
// simulate status pipe behaviour
var epoll int
if fd, err := syscall.EpollCreate1(0); err != nil {
panic("cannot open epoll fd: " + err.Error())
} else {
defer func() {
if err = syscall.Close(fd); err != nil {
panic("cannot close epoll fd: " + err.Error())
}
}()
epoll = fd
}
if err := syscall.EpollCtl(epoll, syscall.EPOLL_CTL_ADD, int(statFile.Fd()), &syscall.EpollEvent{}); err != nil {
panic("cannot add status pipe to epoll: " + err.Error())
}
if _, err := statFile.Write([]byte{'x'}); err != nil {
panic("cannot write to status pipe: " + err.Error())
}
// wait for status pipe close
events := make([]syscall.EpollEvent, 1)
if _, err := syscall.EpollWait(epoll, events, -1); err != nil {
panic("cannot poll status pipe: " + err.Error())
}
if events[0].Events != syscall.EPOLLERR {
panic(strconv.Itoa(int(events[0].Events)))
}
}
}
|
