Convenience function to return the value of a yes / no XML attribute.

Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
---
 src/libvirt_private.syms |  1 +
 src/util/virxml.c        | 49 ++++++++++++++++++++++++++++++++++++++++
 src/util/virxml.h        | 10 ++++++++
 3 files changed, 60 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index cb9fe7c80a..1aac0de1ae 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -3546,6 +3546,7 @@ virXMLParseHelper;
 virXMLPickShellSafeComment;
 virXMLPropString;
 virXMLPropStringLimit;
+virXMLPropTristateBool;
 virXMLSaveFile;
 virXMLValidateAgainstSchema;
 virXMLValidatorFree;
diff --git a/src/util/virxml.c b/src/util/virxml.c
index 4a6fe09468..0b822d7c4d 100644
--- a/src/util/virxml.c
+++ b/src/util/virxml.c
@@ -558,6 +558,55 @@ virXMLNodeContentString(xmlNodePtr node)
 }
 
 
+/**
+ * virXMLPropTristateBool:
+ * @node: XML dom node pointer
+ * @name: Name of the property (attribute) to get
+ * @flags: Bitwise or of virXMLPropFlags
+ * @result: The returned value
+ *
+ * Convenience function to return value of a yes / no attribute.
+ *
+ * Returns 1 in case of success in which case @result is set,
+ *         or 0 if the attribute is not present,
+ *         or -1 and reports an error on failure.
+ */
+int
+virXMLPropTristateBool(xmlNodePtr node, const char* name,
+                       virXMLPropFlags flags, virTristateBool *result)
+{
+    g_autofree char *tmp = NULL;
+    int val;
+
+    if (!node || !name || !result) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Invalid argument to %s"),
+                       __FUNCTION__);
+        return -1;
+    }
+
+    if (!(tmp = virXMLPropString(node, name))) {
+        if ((flags & VIR_XML_PROP_REQUIRED) != VIR_XML_PROP_REQUIRED)
+            return 0;
+
+        virReportError(VIR_ERR_XML_ERROR,
+                       _("Missing required attribute '%s' in element '%s'"),
+                       name, node->name);
+        return -1;
+    }
+
+    if ((val = virTristateBoolTypeFromString(tmp)) <= 0) {
+        virReportError(VIR_ERR_XML_ERROR,
+                       _("Invalid value for attribute '%s' in element '%s': '%s'. Expected 'yes' or 'no'"),
+                       name, node->name, tmp);
+        return -1;
+    }
+
+    *result = val;
+    return 1;
+}
+
+
 /**
  * virXPathBoolean:
  * @xpath: the XPath string to evaluate
diff --git a/src/util/virxml.h b/src/util/virxml.h
index d32f77b867..53de416a7f 100644
--- a/src/util/virxml.h
+++ b/src/util/virxml.h
@@ -28,10 +28,16 @@
 #include <libxml/relaxng.h>
 
 #include "virbuffer.h"
+#include "virenum.h"
 
 xmlXPathContextPtr virXMLXPathContextNew(xmlDocPtr xml)
     G_GNUC_WARN_UNUSED_RESULT;
 
+typedef enum {
+    VIR_XML_PROP_OPTIONAL       = 0,        /* Attribute may be absent */
+    VIR_XML_PROP_REQUIRED       = 1 << 0,   /* Attribute may not be absent */
+} virXMLPropFlags;
+
 int              virXPathBoolean(const char *xpath,
                                  xmlXPathContextPtr ctxt);
 char *            virXPathString(const char *xpath,
@@ -77,6 +83,10 @@ char *     virXMLPropStringLimit(xmlNodePtr node,
                                  const char *name,
                                  size_t maxlen);
 char *   virXMLNodeContentString(xmlNodePtr node);
+int       virXMLPropTristateBool(xmlNodePtr node,
+                                 const char *name,
+                                 virXMLPropFlags flags,
+                                 virTristateBool *result);
 
 /* Internal function; prefer the macros below.  */
 xmlDocPtr      virXMLParseHelper(int domcode,
-- 
2.26.2

On Thu, Apr 08, 2021 at 13:19:51 +0200, Tim Wiederhake wrote:
> Convenience function to return the value of a yes / no XML attribute.
> 
> Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
> ---
>  src/libvirt_private.syms |  1 +
>  src/util/virxml.c        | 49 ++++++++++++++++++++++++++++++++++++++++
>  src/util/virxml.h        | 10 ++++++++
>  3 files changed, 60 insertions(+)

Oops, I started reviewing v4 instead of v5. If you follow my comments on
v4:

Reviewed-by: Peter Krempa <pkrempa@redhat.com>

On Thu, Apr 08, 2021 at 13:19:51 +0200, Tim Wiederhake wrote:
> Convenience function to return the value of a yes / no XML attribute.
> 
> Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
> ---
>  src/libvirt_private.syms |  1 +
>  src/util/virxml.c        | 49 ++++++++++++++++++++++++++++++++++++++++
>  src/util/virxml.h        | 10 ++++++++
>  3 files changed, 60 insertions(+)

[...]

> diff --git a/src/util/virxml.c b/src/util/virxml.c
> index 4a6fe09468..0b822d7c4d 100644
> diff --git a/src/util/virxml.h b/src/util/virxml.h
> index d32f77b867..53de416a7f 100644
> --- a/src/util/virxml.h
> +++ b/src/util/virxml.h
> @@ -28,10 +28,16 @@
>  #include <libxml/relaxng.h>
>  
>  #include "virbuffer.h"
> +#include "virenum.h"
>  
>  xmlXPathContextPtr virXMLXPathContextNew(xmlDocPtr xml)
>      G_GNUC_WARN_UNUSED_RESULT;
>  
> +typedef enum {
> +    VIR_XML_PROP_OPTIONAL       = 0,        /* Attribute may be absent */
> +    VIR_XML_PROP_REQUIRED       = 1 << 0,   /* Attribute may not be absent */
> +} virXMLPropFlags;
> +
>  int              virXPathBoolean(const char *xpath,
>                                   xmlXPathContextPtr ctxt);
>  char *            virXPathString(const char *xpath,
> @@ -77,6 +83,10 @@ char *     virXMLPropStringLimit(xmlNodePtr node,
>                                   const char *name,
>                                   size_t maxlen);
>  char *   virXMLNodeContentString(xmlNodePtr node);
> +int       virXMLPropTristateBool(xmlNodePtr node,
> +                                 const char *name,
> +                                 virXMLPropFlags flags,
> +                                 virTristateBool *result);

I've posted
https://listman.redhat.com/archives/libvir-list/2021-April/msg00659.html

to fix the terrible header formatting so that we don't just keep adding
more and more use.