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package backup
import (
"io"
)
// LazyWriter is a WriteCloser that will call Create when on the first call to
// Write. This means it will only create a file if there will be data written
// to it.
type LazyWriter struct {
create func() (io.WriteCloser, error)
w io.WriteCloser
}
// NewLazyWriter initializes a new LazyWriter. create is called on the first
// call of Write, any errors will be returned by this call.
func NewLazyWriter(create func() (io.WriteCloser, error)) *LazyWriter {
return &LazyWriter{
create: create,
}
}
func (w *LazyWriter) Write(p []byte) (int, error) {
if w.w == nil {
var err error
w.w, err = w.create()
if err != nil {
return 0, err
}
}
return w.w.Write(p)
}
// Close calls Close on the WriteCloser returned by Create, passing on any
// returned error. Close must be called to properly clean up resources.
func (w *LazyWriter) Close() error {
if w.w == nil {
return nil
}
return w.w.Close()
}
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