Add support for read-only proxy trees

This change allows a remote apteryx database to be mounted at a
proxy node as a read only tree.

The logical-element model has been extended to contain a read only
logical element for testing purposes.

apteryx-xml.h

@@ -95,6 +95,7 @@ bool sch_is_executable (sch_node * node);
 bool sch_is_hidden (sch_node * node);
 bool sch_is_config (sch_node * node);
 bool sch_is_proxy (sch_node * node);
+bool sch_is_read_only_proxy (sch_node * node);
 char *sch_translate_to (sch_node * node, char *value);
 char *sch_translate_from (sch_node * node, char *value);
 bool sch_validate_pattern (sch_node * node, const char *value);
@@ -120,6 +121,7 @@ typedef enum
     SCH_F_SET_NULL              = (1 << 13), /* Set all nodes to NULL */
     SCH_F_FILTER_RDEPTH         = (1 << 14), /* Set filter based on depth value */
     SCH_F_IDREF_VALUES          = (1 << 15), /* Expand identityref based values to include type information */
+    SCH_F_MODIFY_DATA           = (1 << 16), /* The created tree will be used to modify the associated model */
 } sch_flags;
 GNode *sch_path_to_gnode (sch_instance * instance, sch_node * schema, const char * path, int flags, sch_node ** rschema);
 bool sch_query_to_gnode (sch_instance * instance, sch_node * schema, GNode *parent, const char * query, int flags, int *rflags);

models/logical-element.xml

@@ -7,8 +7,14 @@
   <NODE name="logical-elements" help="Allows a device to support multiple logical element (device) instances.">
     <NODE name="logical-element" help="List of logical elements.">
       <NODE name="*" mode="p" help="The logical-element entry with key name">
-        <NODE name="name" mode="rw" help="Device-wide unique identifier for the logical element."/>
-        <NODE name="root" help="Container for mount point."/>
+        <NODE name="name" mode="rw" help="Device-wide unique identifier for the logical element." />
+        <NODE name="root" help="Container for mount point." />
+      </NODE>
+    </NODE>
+    <NODE name="logical-element-ro" help="List of read only logical elements.">
+      <NODE name="*" mode="pr" help="The logical-element entry with key name">
+        <NODE name="name" mode="rw" help="Device-wide unique identifier for the logical element." />
+        <NODE name="root" help="Container for mount point." />
       </NODE>
     </NODE>
   </NODE>

schema.c

@@ -1798,6 +1798,20 @@ sch_is_proxy (sch_node * node)
     return access;
 }
 
+bool
+sch_is_read_only_proxy (sch_node * node)
+{
+    xmlNode *xml = (xmlNode *) node;
+    bool read_only = false;
+    char *mode = (char *) xmlGetProp (xml, (xmlChar *) "mode");
+    if (mode && strchr (mode, 'p') != NULL && strchr (mode, 'r') != NULL)
+    {
+        read_only = true;
+    }
+    free (mode);
+    return read_only;
+}
+
 char *
 sch_translate_to (sch_node * node, char *value)
 {
@@ -2590,6 +2604,7 @@ _sch_path_to_gnode (sch_instance * instance, sch_node ** rschema, xmlNs *ns, con
     char *name = NULL;
     sch_node *last_good_schema = NULL;
     bool is_proxy = false;
+    bool read_only = false;
 
     if (path && path[0] == '/')
     {
@@ -2656,6 +2671,7 @@ _sch_path_to_gnode (sch_instance * instance, sch_node ** rschema, xmlNs *ns, con
             if (!child)
             {
                 is_proxy = sch_is_proxy (schema);
+                read_only = sch_is_read_only_proxy (schema);
             }
         }
 
@@ -2686,6 +2702,12 @@ _sch_path_to_gnode (sch_instance * instance, sch_node ** rschema, xmlNs *ns, con
 
         last_good_schema = schema;
         schema = _sch_node_child (ns, schema, name);
+        if ((flags & SCH_F_MODIFY_DATA) && schema && read_only)
+        {
+            ERROR (flags, SCH_E_NOTWRITABLE, "Node not writable \"%s\"\n", name);
+            goto exit;
+        }
+
         if ((flags & SCH_F_XPATH) && schema == NULL && g_strcmp0 (name, "*") == 0)
         {
             GList *path_list = NULL;