// payload checksum, false if not.
func skipContentSha256Cksum(r *http.Request) bool {
	var (
		v  []string
		ok bool
	)

	if isRequestPresignedSignatureV4(r) {
		v, ok = r.Form[xhttp.AmzContentSha256]
		if !ok {
			v, ok = r.Header[xhttp.AmzContentSha256]
		}
	} else {
		v, ok = r.Header[xhttp.AmzContentSha256]
	}

	// Skip if no header was set.
	if !ok {
		return true
	}

	errFaultyDisk,
	errFaultyRemoteDisk,
}

var baseIgnoredErrs = baseErrs

// Is a one place function which converts all os.PathError
// into a more FS object layer friendly form, converts
// known errors into their typed form for top level
// interpretation.
func osErrToFileErr(err error) error {
	if err == nil {
		return nil
	}
	if osIsNotExist(err) {
		return errFileNotFound
	}

        def fetch_credentials():
            # HTTP headers are case insensitive filter out
            # all duplicate headers and pick one.
            headers = {}
            headers['content-type'] = 'application/x-www-form-urlencoded'
            headers['authorization'] = urllib3.make_headers(
                basic_auth='%s:%s' % (self.cid, self.csec))['authorization']

            response = self._http.urlopen('POST', self.idp_ep,

	req, err := http.NewRequest(http.MethodPost, k.oeConfig.TokenEndpoint, strings.NewReader(values.Encode()))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

	resp, err := k.client.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	var accessToken Token
	if err = json.NewDecoder(resp.Body).Decode(&accessToken); err != nil {

		if s3Error := checkRequestAuthType(ctx, r, policy.ListenBucketNotificationAction, bucketName, ""); s3Error != ErrNone {
			writeErrorResponse(ctx, w, errorCodes.ToAPIErr(s3Error), r.URL)
			return
		}
	}

	values := r.Form

	var prefix string
	if len(values[peerRESTListenPrefix]) > 1 {
		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrFilterNamePrefix), r.URL)
		return
	}

	if len(values[peerRESTListenPrefix]) == 1 {

	if err := json.Unmarshal(reqBytes, &cfg); err != nil {
		writeErrorResponseJSON(ctx, w, toAdminAPIErr(ctx, err), r.URL)
		return
	}

	var ignoreInUse bool
	if forceStr := r.Form.Get("force"); forceStr != "" {
		ignoreInUse, _ = strconv.ParseBool(forceStr)
	}

	// Disallow remote tiers with internal storage class names
	switch cfg.Name {
	case storageclass.STANDARD, storageclass.RRS:

	return signedHeaders, ErrNone
}

// signValues data type represents structured form of AWS Signature V4 header.
type signValues struct {
	Credential    credentialHeader
	SignedHeaders []string
	Signature     string
}

// preSignValues data type represents structured form of AWS Signature V4 query string.
type preSignValues struct {
	signValues
	Date    time.Time
	Expires time.Duration

	if len(path) < 248 {
		// Don't fix. (This is how Go 1.7 and earlier worked,
		// not automatically generating the \\?\ form)
		return path
	}

	// The extended form begins with \\?\, as in
	// \\?\c:\windows\foo.txt or \\?\UNC\server\share\foo.txt.
	// The extended form disables evaluation of . and .. path
	// elements and disables the interpretation of / as equivalent

			return
		}
		if r.Form.Get("state") != state {
			http.Error(w, "state did not match", http.StatusBadRequest)
			return
		}

		var getWebTokenExpiry func() (*credentials.WebIdentityToken, error)
		if clientSec == "" {
			getWebTokenExpiry = func() (*credentials.WebIdentityToken, error) {
				return &credentials.WebIdentityToken{
					Token: r.Form.Get("id_token"),
				}, nil
			}
		} else {

	if err != nil {
		return false, err
	}

	// Handle large OPA responses when OPA URL is of
	// form http://localhost:8181/v1/data/httpapi/authz
	type opaResultAllow struct {
		Result struct {
			Allow bool `json:"allow"`
		} `json:"result"`
	}

	// Handle simpler OPA responses when OPA URL is of
	// form http://localhost:8181/v1/data/httpapi/authz/allow
	type opaResult struct {
		Result bool `json:"result"`
	}