// The s3ChunkedReader returns io.EOF when the final 0-length chunk is read.
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)

}

func reqSignatureV4Verify(r *http.Request, region string, stype serviceType) (s3Error APIErrorCode) {
	sha256sum := getContentSha256Cksum(r, stype)
	switch {
	case isRequestSignatureV4(r):
		return doesSignatureMatch(sha256sum, r, region, stype)
	case isRequestPresignedSignatureV4(r):
		return doesPresignedSignatureMatch(sha256sum, r, region, stype)
	default:
		return ErrAccessDenied
	}
}