indexCh <- idx
			pw.CloseWithError(err)
			return
		}
		pw.CloseWithError(comp.Close())
	}()
	var gotIdx []byte
	return pr, func() []byte {
		if gotIdx != nil {
			return gotIdx
		}
		// Will get index or nil if closed.
		gotIdx = <-indexCh
		return gotIdx
	}
}

// compressSelfTest performs a self-test to ensure that compression

	for i, ver := range x.versions {
		if key == ver.header.VersionID {
			obj, err := x.getIdx(i)
			return i, obj, err
		}
	}
	return -1, nil, errFileVersionNotFound
}

func (x *xlMetaV2) getIdx(idx int) (ver *xlMetaV2Version, err error) {
	if idx < 0 || idx >= len(x.versions) {
		return nil, errFileNotFound
	}
	var dst xlMetaV2Version

				out += ".incomplete"
				fmt.Println(missingAll, "bytes missing.")
			} else {
				if wantMD5 != "" {
					sum := md5.Sum(combined)
					gotMD5 := hex.EncodeToString(sum[:])
					if gotMD5 != wantMD5 {
						fmt.Println("MD5 mismatch. Expected", wantMD5, "got", gotMD5)
						out += ".mismatch"
					} else {
						fmt.Println("MD5 verified.")
						out = fmt.Sprintf("verified/%s", baseName)
					}