From 23ab20927220a4f2f70552f70dc14c8407863870 Mon Sep 17 00:00:00 2001
From: Peter Krempa <pkrempa@redhat.com>
Date: Tue, 26 Feb 2019 17:34:57 +0100
Subject: [PATCH] util: XML: Introduce automatic reset of XPath's current node
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Quite a few parts modify the XPath context current node to shift the
scope and allow easier queries. This also means that the node needs
to be restored afterwards.

Introduce a macro based on 'VIR_AUTOCLEAN' which adds a local structure
on the stack remembering the original node along with a function which
will make sure that the node is reset when the local structure leaves
scope.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
---
 src/libvirt_private.syms |  1 +
 src/util/virxml.c        | 10 ++++++++++
 src/util/virxml.h        | 24 ++++++++++++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index e68e3f3a3b..770a921357 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -3247,6 +3247,7 @@ virXMLValidatorFree;
 virXMLValidatorInit;
 virXMLValidatorValidate;
 virXPathBoolean;
+virXPathContextNodeRestore;
 virXPathInt;
 virXPathLong;
 virXPathLongHex;
diff --git a/src/util/virxml.c b/src/util/virxml.c
index 8eb201fddf..f55b9a362c 100644
--- a/src/util/virxml.c
+++ b/src/util/virxml.c
@@ -1398,3 +1398,13 @@ virXMLFormatElement(virBufferPtr buf,
     virBufferFreeAndReset(childBuf);
     return ret;
 }
+
+
+void
+virXPathContextNodeRestore(virXPathContextNodeSavePtr save)
+{
+    if (!save->ctxt)
+        return;
+
+    save->ctxt->node = save->node;
+}
diff --git a/src/util/virxml.h b/src/util/virxml.h
index 23a4da1b7e..78a1e7fa5e 100644
--- a/src/util/virxml.h
+++ b/src/util/virxml.h
@@ -219,4 +219,28 @@ virXMLFormatElement(virBufferPtr buf,
                     virBufferPtr attrBuf,
                     virBufferPtr childBuf);
 
+struct _virXPathContextNodeSave {
+    xmlXPathContextPtr ctxt;
+    xmlNodePtr node;
+};
+typedef struct _virXPathContextNodeSave virXPathContextNodeSave;
+typedef virXPathContextNodeSave *virXPathContextNodeSavePtr;
+
+void
+virXPathContextNodeRestore(virXPathContextNodeSavePtr save);
+
+VIR_DEFINE_AUTOCLEAN_FUNC(virXPathContextNodeSave, virXPathContextNodeRestore);
+
+/**
+ * VIR_XPATH_NODE_AUTORESTORE:
+ * @ctxt: XML XPath context pointer
+ *
+ * This macro ensures that when the scope where it's used ends, @ctxt's current
+ * node pointer is reset to the original value when this macro was used.
+ */
+# define VIR_XPATH_NODE_AUTORESTORE(_ctxt) \
+    VIR_AUTOCLEAN(virXPathContextNodeSave) _ctxt ## CtxtSave = { .ctxt = _ctxt,\
+                                                                 .node = _ctxt->node}; \
+    ignore_value(&_ctxt ## CtxtSave)
+
 #endif /* LIBVIRT_VIRXML_H */