config nodes: utility code to create a node for a specific file

The factory function is defined in ConfigNode because that is the minimal API
that is needed by code creating and using such a node. The actual implementatation
is in FileConfigNode.cpp and uses a SafeConfigNode as wrapper to make key/value
pairs safe for storing.

src/core/ConfigNode.h

@@ -10,6 +10,8 @@
 #include <string>
 using namespace std;
 
+#include <boost/shared_ptr.hpp>
+
 /**
  * This class corresponds to the Funambol C++ client
  * DeviceManagementNode, but offers a slightly different API.  See
@@ -20,6 +22,9 @@ class ConfigNode {
     /** free resources without saving */
     virtual ~ConfigNode() {}
 
+    /** creates a file-backed config node which accepts arbitrary key/value pairs */
+    static boost::shared_ptr<ConfigNode> createFileNode(const string &filename);
+
     /** a name for the node that the user can understand */
     virtual string getName() const = 0;
 

src/core/FileConfigNode.cpp

@@ -4,6 +4,7 @@
  */
 
 #include "FileConfigNode.h"
+#include "SafeConfigNode.h"
 #include "EvolutionSyncClient.h"
 #include "SyncEvolutionUtil.h"
 
@@ -16,6 +17,22 @@
 
 /** @TODO: replace stdio.h with streams */
 
+boost::shared_ptr<ConfigNode> ConfigNode::createFileNode(const string &filename)
+{
+    string::size_type off = filename.rfind('/');
+    boost::shared_ptr<ConfigNode> filenode;
+    if (off != filename.npos) {
+        filenode.reset(new FileConfigNode(filename.substr(0, off),
+                                          filename.substr(off + 1),
+                                          false));
+    } else {
+        filenode.reset(new FileConfigNode(".", filename, false));
+    }
+    boost::shared_ptr<SafeConfigNode> savenode(new SafeConfigNode(filenode));
+    savenode->setMode(false);
+    return savenode;
+}
+
 FileConfigNode::FileConfigNode(const string &path, const string &fileName, bool readonly) :
     m_path(path),
     m_fileName(fileName),