case c.Is(ChecksumSHA1):
		return sha1.New()
	case c.Is(ChecksumSHA256):
		return sha256.New()
	}
	return nil
}

// Trailing return whether the checksum is trailing.
func (c ChecksumType) Trailing() bool {
	return c.Is(ChecksumTrailing)
}

// NewChecksumFromData returns a new checksum from specified algorithm and base64 encoded value.

		"substring('abcd' , 2 , 2)",

		"substring('abcd' , 22 )",
		"trim('  aab  ')",
		"trim(leading from '  aab  ')",
		"trim(trailing from '  aab  ')",
		"trim(both from '  aab  ')",

		"trim(both '12' from '  aab  ')",
		"trim(leading '12' from '  aab  ')",
		"trim(trailing '12' from '  aab  ')",
		"count(23)",
	}
	for i, tc := range validCases {
		err := p.ParseString(tc, &fex)
		if err != nil {

			extractedSignedHeaders.Set(header, strconv.FormatInt(r.ContentLength, 10))
		default:
			return nil, ErrUnsignedHeaders
		}
	}
	return extractedSignedHeaders, ErrNone
}

// Trim leading and trailing spaces and replace sequential spaces with one space, following Trimall()
// in http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html
func signV4TrimAll(input string) string {

}

var etagRegex = regexp.MustCompile("\"*?([^\"]*?)\"*?$")

// canonicalizeETag returns ETag with leading and trailing double-quotes removed,
// if any present
func canonicalizeETag(etag string) string {
	return etagRegex.ReplaceAllString(etag, "$1")
}

// Init - populates the input values, initializes CondCheck

}

// pathsJoinPrefix - like pathJoin retains trailing SlashSeparator
// for all elements, prepends them with 'prefix' respectively.
func pathsJoinPrefix(prefix string, elem ...string) (paths []string) {
	paths = make([]string, len(elem))
	for i, e := range elem {
		paths[i] = pathJoin(prefix, e)
	}
	return paths
}

// pathJoin - like path.Join() but retains trailing SlashSeparator of the last element

		if cr.debug {
			fmt.Printf("prefix, want prefix %q, got %q", "x-amz-trailer-signature:", string(sig))
		}
		return errMalformedEncoding
	}

	// TODO: It seems like we may have to be prepared to rewrite and sort trailing headers:
	// https://docs.aws.amazon.com/IAM/latest/UserGuide/create-signed-request.html

	// Any value must end with a newline.
	// Not all clients send that.
	trailerRaw := valueBuffer.Bytes()

		if strings.HasPrefix(baseDir, dirPath) {
			return nil
		}
	}

	// Slow path: make sure parent exists and then call Mkdir for path.
	i := len(dirPath)
	for i > 0 && os.IsPathSeparator(dirPath[i-1]) { // Skip trailing path separator.
		i--
	}

	j := i
	for j > 0 && !os.IsPathSeparator(dirPath[j-1]) { // Scan backward over element.
		j--
	}

	if j > 1 {
		// Create parent.

			Objects: []ObjectInfo{
				{Name: "temporary/0/"},
			},
		},
		// ListObjectsResult-34:
		//    * Listing with marker > last object should return empty
		//    * Listing an object with a trailing slash and '/' delimiter
		34: {
			IsTruncated: false,
			Objects:     []ObjectInfo{},
		},
		// ListObjectsResult-35 list with custom uncommon delimiter
		35: {
			IsTruncated: false,

	globalTierConfigMgr *TierConfigMgr

	globalConsoleSrv *consoleapi.Server

	// handles service freeze or un-freeze S3 API calls.
	globalServiceFreeze atomic.Value

	// Only needed for tracking
	globalServiceFreezeCnt int32
	globalServiceFreezeMu  sync.Mutex // Updates.

	// List of local drives to this node, this is only set during server startup,

	// - missing format.json (unformatted drive)
	// - format.json is valid but invalid 'uuid'
	if err = p.checkDiskStale(); err != nil {
		return ctx, done, err
	}

	// Disallow recursive tracking to avoid deadlocks.
	if ctx.Value(healthDiskCtxKey{}) != nil {
		done = p.updateStorageMetrics(s, paths...)
		return ctx, done, nil
	}

	if contextCanceled(ctx) {
		return ctx, done, ctx.Err()
	}