func (f *MemFiler) Close() (err error) {
	if f.nest != 0 {
		return &ErrPERM{(f.Name() + ":Close")}
	}
	return f.fi.Close()
}
Close implements Filer.
package lldb
import (
	"fmt"
	"io"
	"github.com/cznic/internal/file"
)
var _ Filer = &MemFiler{}
type MemFiler struct {
	fi   file.Interface
	nest int
}
func NewMemFiler() *MemFiler {
	fi, err := file.OpenMem("")
	if err != nil {
		return nil
	}
	return &MemFiler{fi: fi}
}
func (f *MemFiler) BeginUpdate() error {
	f.nest++
	return nil
}