Implement self-update recovery (T-403)

app-win7/platform/windows/selfupdate.go

@@ -0,0 +1,49 @@
+package windows
+
+import (
+	"context"
+	"fmt"
+	"time"
+)
+
+type pidWaitHandle interface {
+	Wait(time.Duration) (bool, error)
+	Close() error
+}
+
+type pidOpener func(int) (pidWaitHandle, error)
+
+func waitForProcessExit(ctx context.Context, pid int, timeout time.Duration, open pidOpener) error {
+	if pid <= 0 {
+		return fmt.Errorf("process PID must be positive")
+	}
+	if timeout <= 0 {
+		return fmt.Errorf("process wait timeout must be positive")
+	}
+	handle, err := open(pid)
+	if err != nil {
+		return fmt.Errorf("open process %d: %w", pid, err)
+	}
+	defer handle.Close()
+	deadline := time.NewTimer(timeout)
+	defer deadline.Stop()
+	for {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+		exited, err := handle.Wait(250 * time.Millisecond)
+		if err != nil {
+			return fmt.Errorf("wait for process %d: %w", pid, err)
+		}
+		if exited {
+			return nil
+		}
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-deadline.C:
+			return context.DeadlineExceeded
+		default:
+		}
+	}
+}