+ <li>New class <tt>broadcast-handler</tt> as a generalization

+      of the older <tt>sax-proxy</tt>.</li>

+      <li>New class <tt>tapping-source</tt>, a klacks source that
+      relays events from an upstream klacks source unchanged, while also
+      emitting them as SAX events to a user-specified handler at the
+      same time.</li>

+      Fixed serialize-event to generate
+      start-prefix-mapping and end-prefix-mapping events.  New function
+      map-current-namespace-declarations.</li>

klacks/tap-source.lisp

@@ -0,0 +1,103 @@
+;;; -*- Mode: Lisp; readtable: runes; -*-
+;;;  (c) copyright 2007 David Lichteblau
+
+;;; This library is free software; you can redistribute it and/or
+;;; modify it under the terms of the GNU Library General Public
+;;; License as published by the Free Software Foundation; either
+;;; version 2 of the License, or (at your option) any later version.
+;;;
+;;; This library is distributed in the hope that it will be useful,
+;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;; Library General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU Library General Public
+;;; License along with this library; if not, write to the
+;;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;;; Boston, MA  02111-1307  USA.
+
+(in-package :cxml)
+
+(defun klacks:make-tapping-source (upstream-source &optional sax-handler)
+  (make-instance 'klacks:tapping-source
+		 :upstream-source upstream-source
+		 :dribble-handler sax-handler))
+
+(defclass klacks:tapping-source (klacks:source)
+    ((upstream-source :initarg :upstream-source :accessor upstream-source)
+     (dribble-handler :initarg :dribble-handler :accessor dribble-handler)
+     (seen-event-p :initform nil :accessor seen-event-p)))
+
+(defmethod initialize-instance :after ((instance klacks:tapping-source) &key)
+  (let ((s-p (make-instance 'klacksax :source (upstream-source instance))))
+    (sax:register-sax-parser (dribble-handler instance) s-p)))
+
+
+;;; event dribbling 
+
+(defun maybe-dribble (source)
+  (unless (seen-event-p source)
+    (klacks:serialize-event (upstream-source source)
+			    (dribble-handler source)
+			    :consume nil)
+    (setf (seen-event-p source) t)))
+
+(defmethod klacks:peek ((source klacks:tapping-source))
+  (multiple-value-prog1
+      (klacks:peek (upstream-source source))
+    (maybe-dribble source)))
+
+(defmethod klacks:peek-value ((source klacks:tapping-source))
+  (multiple-value-prog1
+      (klacks:peek-value (upstream-source source))
+    (maybe-dribble source)))
+
+(defmethod klacks:peek-next ((source klacks:tapping-source))
+  (setf (seen-event-p source) nil)
+  (multiple-value-prog1
+      (klacks:peek-next (upstream-source source))
+    (maybe-dribble source)))
+
+(defmethod klacks:consume ((source klacks:tapping-source))
+  (maybe-dribble source)
+  (multiple-value-prog1
+      (klacks:consume (upstream-source source))
+    (setf (seen-event-p source) nil)))
+
+
+;;; loop through
+
+(defmethod klacks:close-source ((source klacks:tapping-source))
+  (klacks:close-source (upstream-source source)))
+
+(defmethod klacks:map-attributes (fn (source klacks:tapping-source))
+  (klacks:map-attributes fn (upstream-source source)))
+
+(defmethod klacks:map-current-namespace-declarations
+    (fn (source klacks:tapping-source))
+  (klacks:map-current-namespace-declarations fn (upstream-source source)))
+
+(defmethod klacks:list-attributes ((source klacks:tapping-source))
+  (klacks:list-attributes (upstream-source source)))
+
+(defmethod klacks:current-line-number ((source klacks:tapping-source))
+  (klacks:current-line-number (upstream-source source)))
+
+(defmethod klacks:current-column-number ((source klacks:tapping-source))
+  (klacks:current-column-number (upstream-source source)))
+
+(defmethod klacks:current-system-id ((source klacks:tapping-source))
+  (klacks:current-system-id (upstream-source source)))
+
+(defmethod klacks:current-xml-base ((source klacks:tapping-source))
+  (klacks:current-xml-base (upstream-source source)))
+
+(defmethod klacks:current-cdata-section-p ((source klacks:tapping-source))
+  (klacks:current-cdata-section-p (upstream-source source)))
+
+(defmethod klacks:find-namespace-binding
+    (prefix (source klacks:tapping-source))
+  (klacks:find-namespace-binding prefix (upstream-source source)))
+
+(defmethod klacks:decode-qname (qname (source klacks:tapping-source))
+  (klacks:decode-qname qname (upstream-source source)))