Add a function to calculate the accept header expected.

websocket-test.el

@@ -76,7 +76,14 @@
            (websocket-test-get-filtered-response
             '("HTTP 1.1" "\0foo\377")))))
 
+(ert-deftest websocket-calculate-accept ()
+  ;; This example comes straight from RFC 6455
+  (should
+   (equal "s3pPLMBiTxaQ9kYGzzhZRbK+xOo="
+    (websocket-calculate-accept "dGhlIHNhbXBsZSBub25jZQ=="))))
+
 (ert-run-tests-interactively 'websocket-genbytes-length)
 (ert-run-tests-interactively 'websocket-filter-basic)
 (ert-run-tests-interactively 'websocket-filter-inflight-packets)
 (ert-run-tests-interactively 'websocket-filter-first-response)
+(ert-run-tests-interactively 'websocket-calculate-accept)

websocket.el

@@ -41,6 +41,10 @@
 The buffer is ` *websocket URL debug*' where URL is the
 URL of the connection.")
 
+(defconst websocket-guid "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
+  "The websocket GUID as defined in RFC 6455. Do not change
+  unless the RFC changes.")
+
 (defun websocket-genbytes ()
   "Generate bytes used at the end of the handshake."
   (let ((s "        "))
@@ -71,6 +75,12 @@ URL of the connection.")
                          max-num-str)))
     (cons max-num-str num)))
 
+(defun websocket-calculate-accept (key)
+  "Calculate the expect value of the accept header.
+This is based on the KEY from the Sec-WebSocket-Key header."
+  (base64-encode-string
+   (sha1 (concat key websocket-guid) nil nil t)))
+
 (defun websocket-open (url filter &optional close-callback)
   "Open a websocket connection to URL.
 Websocket packets are sent as the only argument to FILTER, and if