contentSHA256, err = hex.DecodeString(r.Header.Get(xhttp.AmzContentSha256))
		if err != nil || len(contentSHA256) == 0 {
			return ErrContentSHA256Mismatch
		}
	}

	// Verify 'Content-Md5' and/or 'X-Amz-Content-Sha256' if present.
	// The verification happens implicit during reading.
	reader, err := hash.NewReader(ctx, r.Body, -1, clientETag.String(), hex.EncodeToString(contentSHA256), -1)
	if err != nil {

			return nil, BadDigest{
				ExpectedMD5:   r.checksum.String(),
				CalculatedMD5: md5Hex,
			}
		}
		if len(r.contentSHA256) != 0 && len(SHA256) != 0 && !bytes.Equal(r.contentSHA256, SHA256) {
			return nil, SHA256Mismatch{
				ExpectedSHA256:   hex.EncodeToString(r.contentSHA256),
				CalculatedSHA256: sha256Hex,
			}
		}
		if r.size >= 0 && size >= 0 && r.size != size {