func (r *Reader) SetExpectedMax(expectedMax int64) {
	r.expectedMax = expectedMax
}

// AddChecksum will add checksum checks as specified in
// https://docs.aws.amazon.com/AmazonS3/latest/userguide/checking-object-integrity.html
// Returns ErrInvalidChecksum if a problem with the checksum is found.
func (r *Reader) AddChecksum(req *http.Request, ignoreValue bool) error {
	cs, err := GetContentChecksum(req.Header)
	if err != nil {

		actualReader, err := hash.NewReader(ctx, reader, size, md5hex, sha256hex, actualSize)
		if err != nil {
			writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
			return
		}
		if err = actualReader.AddChecksum(r, false); err != nil {
			writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrInvalidChecksum), r.URL)
			return
		}

		// Set compression metrics.
		wantEncryption := crypto.Requested(r.Header)

		actualReader, err := hash.NewReader(ctx, reader, size, md5hex, sha256hex, actualSize)
		if err != nil {
			writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
			return
		}
		if err = actualReader.AddChecksum(r, false); err != nil {
			writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrInvalidChecksum), r.URL)
			return
		}
		opts.WantChecksum = actualReader.Checksum()

		// Set compression metrics.