1//go:build windows
 2
 3package cmd
 4
 5import (
 6	"fmt"
 7	"math"
 8	"os"
 9
10	"golang.org/x/sys/windows"
11)
12
13// acquireSpawnLock takes an exclusive lock on the given file (creating
14// it if necessary) using LockFileEx, and returns a release function
15// that unlocks and closes the file. Blocks until the lock is acquired.
16func acquireSpawnLock(path string) (func(), error) {
17	f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0o600)
18	if err != nil {
19		return nil, fmt.Errorf("open spawn lock %q: %v", path, err)
20	}
21	h := windows.Handle(f.Fd())
22	ol := new(windows.Overlapped)
23	if err := windows.LockFileEx(h, windows.LOCKFILE_EXCLUSIVE_LOCK, 0, math.MaxUint32, math.MaxUint32, ol); err != nil {
24		_ = f.Close()
25		return nil, fmt.Errorf("LockFileEx spawn lock %q: %v", path, err)
26	}
27	return func() {
28		ol := new(windows.Overlapped)
29		_ = windows.UnlockFileEx(windows.Handle(f.Fd()), 0, math.MaxUint32, math.MaxUint32, ol)
30		_ = f.Close()
31	}, nil
32}