add readxml function that reads an XML file and returns it as property tree

Nasal/io.nas

@@ -26,3 +26,33 @@ var ifmts = {dir:4, reg:8, lnk:10, sock:12, fifo:1, blk:6, chr:2};
 foreach(fmt; keys(ifmts))
     caller(0)[0]["is" ~ fmt] = _gen_ifmt_test(ifmts[fmt]);
 
+# Reads an XML file from an absolute path and returns it as property
+# tree. All nodes are of type STRING, attributes are written as regular
+# nodes with the optional prefix prepended to the name. If the prefix
+# is nil, then attributes are ignored. Returns nil on error.
+var readxml = func(file, prefix = "") {
+    var stack = [[0, ""]];
+    var node = props.Node.new();
+    var tree = node;           # prevent GC
+    var start = func(name, attr) {
+        stack[-1][0] += 1;     # count children
+        append(stack, [0, ""]);
+        var index = size(node.getChildren(name));
+        node = node.getChild(name, index, 1);
+        if(prefix != nil)
+            foreach(var n; keys(attr))
+                node.getNode(prefix ~ n, 1).setValue(attr[n]);
+    }
+    var end = func(name) {
+        var buf = pop(stack);
+        if(!buf[0] and size(buf[1]))
+            node.setValue(buf[1]);
+        node = node.getParent();
+    }
+    var data = func(d) {
+        stack[-1][1] ~= d;
+    }
+    return parsexml(file, start, end, data) == nil ? nil : tree;
+}
+
+