feat(third_party/lisp/s-xml): Check in sources & derivation

Checked in the sources for this because it is tracked upstream in CVS
and I can't be bothered to deal with that right now.

third_party/lisp/s-xml/examples/echo.lisp

@@ -0,0 +1,64 @@
+;;;; -*- mode: lisp -*-
+;;;;
+;;;; $Id: echo.lisp,v 1.1 2005/08/17 13:44:30 scaekenberghe Exp $
+;;;;
+;;;; A simple example as well as a useful tool: parse, echo and pretty print XML
+;;;;
+;;;; Copyright (C) 2002, 2004 Sven Van Caekenberghe, Beta Nine BVBA.
+;;;;
+;;;; You are granted the rights to distribute and use this software
+;;;; as governed by the terms of the Lisp Lesser General Public License
+;;;; (http://opensource.franz.com/preamble.html), also known as the LLGPL.
+
+(in-package :s-xml)
+
+(defun indent (stream count)
+  (loop :repeat (* count 2) :do (write-char #\space stream)))
+
+(defclass echo-xml-seed ()
+  ((stream :initarg :stream)
+   (level :initarg :level :initform 0)))
+
+#+NIL
+(defmethod print-object ((seed echo-xml-seed) stream)
+  (with-slots (stream level) seed
+    (print-unreadable-object (seed stream :type t)
+      (format stream "level=~d" level))))
+
+(defun echo-xml-new-element-hook (name attributes seed)
+  (with-slots (stream level) seed
+    (indent stream level)
+    (format stream "<~a" name)
+    (dolist (attribute (reverse attributes)) 
+      (format stream " ~a=\'" (car attribute))
+      (print-string-xml (cdr attribute) stream)
+      (write-char #\' stream))
+    (format stream ">~%")
+    (incf level)
+    seed))
+
+(defun echo-xml-finish-element-hook (name attributes parent-seed seed)
+  (declare (ignore attributes parent-seed))
+  (with-slots (stream level) seed 
+    (decf level)
+    (indent stream level)
+    (format stream "</~a>~%" name)
+    seed))
+
+(defun echo-xml-text-hook (string seed)
+  (with-slots (stream level) seed
+    (indent stream level)
+    (print-string-xml string stream)
+    (terpri stream)
+    seed))
+  
+(defun echo-xml (in out)
+  "Parse a toplevel XML element from stream in, echoing and pretty printing the result to stream out"
+  (start-parse-xml in
+		   (make-instance 'xml-parser-state
+				  :seed (make-instance 'echo-xml-seed :stream out)
+				  :new-element-hook #'echo-xml-new-element-hook
+				  :finish-element-hook #'echo-xml-finish-element-hook
+				  :text-hook #'echo-xml-text-hook)))
+
+;;;; eof