Make URL-ENCODE more closely match the AWS requirements.

utils.lisp

@@ -115,13 +115,10 @@
           (loop for char across string
                 do (setf state (funcall state char))))))))
 
-;;; The following two functions were adatpted from Drakma source. The
-;;; only change is to escape space as "%20", not #\+ and add the
-;;; encode-slash parameter.
-;;;
-;;; See UriEncode() in
+;;; The following two functions were adatpted from Drakma source. It
+;;; has been adapted to more closely follow the description of
+;;; UriEncode() in
 ;;; http://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-header-based-auth.html
-;;; for the reasoning behind ENCODE-SLASH
 
 (defun url-encode (string &key (encode-slash t))
   "Returns a URL-encoded version of the string STRING using the
@@ -130,11 +127,12 @@ LispWorks external format EXTERNAL-FORMAT."
     (with-output-to-string (out)
       (loop for octet across (string-octets (or string ""))
             for char = (code-char octet)
+            ;;'A'-'Z', 'a'-'z', '0'-'9', '-', '.', '_', and '~'
             do (cond ((or (char<= #\0 char #\9)
                           (char<= #\a char #\z)
                           (char<= #\A char #\Z)
                           (and (not encode-slash) (char= char #\/))
-                          (find char "$-_.!*'()," :test #'char=))
+                          (find char "-._~" :test #'char=))
                       (write-char char out))
                      ((char= char #\Space)
                       (write-string "%20" out))