_, ok := r.Form[xhttp.AmzAccessKeyID]
	return ok
}

// Verify if request has AWS Post policy Signature Version '4'.
func isRequestPostPolicySignatureV4(r *http.Request) bool {
	mediaType, _, err := mime.ParseMediaType(r.Header.Get(xhttp.ContentType))
	if err != nil {
		return false
	}
	return mediaType == "multipart/form-data" && r.Method == http.MethodPost
}

	v := r.Header.Get("Content-Type")
	if v == "" {
		return nil, http.ErrNotMultipart
	}
	if r.Body == nil {
		return nil, errors.New("missing form body")
	}
	d, params, err := mime.ParseMediaType(v)
	if err != nil {
		return nil, http.ErrNotMultipart
	}
	if d != "multipart/form-data" {
		return nil, http.ErrNotMultipart
	}
	boundary, ok := params["boundary"]
	if !ok {

pkg math/rand, type Source interface, Seed(int64)
pkg math/rand, type Zipf struct
pkg mime, func AddExtensionType(string, string) error
pkg mime, func FormatMediaType(string, map[string]string) string
pkg mime, func ParseMediaType(string) (string, map[string]string, error)
pkg mime, func TypeByExtension(string) string
pkg mime/multipart, func NewReader(io.Reader, string) *Reader
pkg mime/multipart, func NewWriter(io.Writer) *Writer