3 files changed, 107 insertions, 1 deletions
diff --git a/src/libexpr/Makefile.am b/src/libexpr/Makefile.am
index d59b798c0bc9..81c851fb0037 100644
--- a/src/libexpr/Makefile.am
+++ b/src/libexpr/Makefile.am
@@ -4,7 +4,8 @@ libexpr_la_SOURCES = nixexpr.cc nixexpr.hh parser.cc parser.hh \
  eval.cc eval.hh primops.cc \
  lexer-tab.c lexer-tab.h parser-tab.c parser-tab.h \
  get-drvs.cc get-drvs.hh \
- attr-path.cc attr-path.hh
+ attr-path.cc attr-path.hh \
+ expr-to-xml.cc expr-to-xml.hh 
 
 BUILT_SOURCES = nixexpr-ast.cc nixexpr-ast.hh \
  parser-tab.h lexer-tab.h parser-tab.c lexer-tab.c
diff --git a/src/libexpr/expr-to-xml.cc b/src/libexpr/expr-to-xml.cc
new file mode 100644
index 000000000000..cd9112a425e2
--- /dev/null
+++ b/src/libexpr/expr-to-xml.cc
@@ -0,0 +1,92 @@
+#include "expr-to-xml.hh"
+
+#include "xml-writer.hh"
+#include "nixexpr-ast.hh"
+#include "aterm.hh"
+
+
+static XMLAttrs singletonAttrs(const string & name, const string & value)
+{
+    XMLAttrs attrs;
+    attrs[name] = value;
+    return attrs;
+}
+
+
+static void printTermAsXML(Expr e, XMLWriter & doc)
+{
+    XMLAttrs attrs;
+    ATerm s;
+    int i;
+    ATermList as, es, formals;
+    ATerm body, pos;
+
+    if (matchStr(e, s))
+        doc.writeEmptyElement("string", singletonAttrs("value", aterm2String(s)));
+
+    else if (matchPath(e, s))
+        doc.writeEmptyElement("path", singletonAttrs("value", aterm2String(s)));
+
+    else if (matchUri(e, s))
+        doc.writeEmptyElement("uri", singletonAttrs("value", aterm2String(s)));
+
+    else if (matchNull(e))
+        doc.writeEmptyElement("null");
+
+    else if (matchInt(e, i))
+        doc.writeEmptyElement("int", singletonAttrs("value", (format("%1%") % i).str()));
+
+    else if (e == eTrue)
+        doc.writeEmptyElement("bool", singletonAttrs("value", "true"));
+
+    else if (e == eFalse)
+        doc.writeEmptyElement("bool", singletonAttrs("value", "false"));
+
+    else if (matchAttrs(e, as)) {
+        XMLOpenElement _(doc, "attrs");
+        ATermMap attrs(128);
+        queryAllAttrs(e, attrs);
+        StringSet names;
+        for (ATermMap::const_iterator i = attrs.begin(); i != attrs.end(); ++i)
+            names.insert(aterm2String(i->key));
+        for (StringSet::iterator i = names.begin(); i != names.end(); ++i) {
+            XMLOpenElement _(doc, "attr", singletonAttrs("name", *i));
+            printTermAsXML(attrs.get(toATerm(*i)), doc);
+        }
+    }
+
+    else if (matchList(e, es)) {
+        XMLOpenElement _(doc, "list");
+        for (ATermIterator i(es); i; ++i)
+            printTermAsXML(*i, doc);
+    }
+
+    else if (matchFunction(e, formals, body, pos)) {
+        XMLOpenElement _(doc, "function");
+        
+        for (ATermIterator i(formals); i; ++i) {
+            Expr name; ValidValues valids; ATerm dummy;
+            if (!matchFormal(*i, name, valids, dummy)) abort();
+            XMLOpenElement _(doc, "arg", singletonAttrs("name", aterm2String(name)));
+
+            ATermList valids2;
+            if (matchValidValues(valids, valids2)) {
+                for (ATermIterator j(valids2); j; ++j) {
+                    XMLOpenElement _(doc, "value");
+                    printTermAsXML(*j, doc);
+                }
+            }
+        }
+    }
+
+    else
+        doc.writeEmptyElement("unevaluated");
+}
+
+
+void printTermAsXML(Expr e, ostream & out)
+{
+    XMLWriter doc(true, out);
+    XMLOpenElement root(doc, "expr");
+    printTermAsXML(e, doc);
+}
diff --git a/src/libexpr/expr-to-xml.hh b/src/libexpr/expr-to-xml.hh
new file mode 100644
index 000000000000..56f947e520de
--- /dev/null
+++ b/src/libexpr/expr-to-xml.hh
@@ -0,0 +1,13 @@
+#ifndef __EXPR_TO_XML_H
+#define __EXPR_TO_XML_H
+
+#include <string>
+#include <map>
+
+#include "nixexpr.hh"
+
+
+void printTermAsXML(Expr e, ostream & out);
+
+
+#endif /* !__EXPR_TO_XML_H */