index = opts.IndexCB()
	}

	actualSize := data.ActualSize()
	if actualSize < 0 {
		_, encrypted := crypto.IsEncrypted(fi.Metadata)
		compressed := fi.IsCompressed()
		switch {
		case compressed:
			// ... nothing changes for compressed stream.
			// if actualSize is -1 we have no known way to
			// determine what is the actualSize.
		case encrypted:
			decSize, err := sio.DecryptedSize(uint64(n))

		modTime = UTCNow()
	}

	kind, encrypted := crypto.IsEncrypted(userDefined)
	actualSize := data.ActualSize()
	if actualSize < 0 {
		compressed := fi.IsCompressed()
		switch {
		case compressed:
			// ... nothing changes for compressed stream.
			// if actualSize is -1 we have no known way to
			// determine what is the actualSize.
		case encrypted:
			decSize, err := sio.DecryptedSize(uint64(n))

		chStorageClass = true
		srcInfo.metadataOnly = false
	} // no changes in storage-class expected so its a metadataonly operation.

	var reader io.Reader = gr

	// Set the actual size to the compressed/decrypted size if encrypted.
	actualSize, err := srcInfo.GetActualSize()
	if err != nil {
		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
		return
	}
	length := actualSize

		wantEncryption := crypto.Requested(r.Header)
		s2c, cb := newS2CompressReader(actualReader, actualSize, wantEncryption)
		idxCb = cb
		defer s2c.Close()
		reader = etag.Wrap(s2c, actualReader)
		size = -1   // Since compressed size is un-predictable.
		md5hex = "" // Do not try to verify the content.
		sha256hex = ""
	}

	var forceMD5 []byte