func newUnsignedV4ChunkedReader(req *http.Request, trailer bool, signature bool) (io.ReadCloser, APIErrorCode) {
	if signature {
		if errCode := doesSignatureMatch(unsignedPayloadTrailer, req, globalSite.Region(), serviceS3); errCode != ErrNone {
			return nil, errCode
		}
	}
	if trailer {
		// Discard anything unsigned.
		req.Trailer = make(http.Header)

const unsignedPayload = "UNSIGNED-PAYLOAD"

// http Header "x-amz-content-sha256" == "STREAMING-UNSIGNED-PAYLOAD-TRAILER" indicates that the
// client did not calculate sha256 of the payload and there is a trailer.
const unsignedPayloadTrailer = "STREAMING-UNSIGNED-PAYLOAD-TRAILER"

// skipContentSha256Cksum returns true if caller needs to skip
// payload checksum, false if not.
func skipContentSha256Cksum(r *http.Request) bool {
	var (
		v  []string