Merge branch dispatcher and broke out pagination callbacks to use it

* Merge branch 'dcornejo-master'
* Broke out pagination callback API from state data callbacks
  * New pagination callback API uses new dispatcher from netgate, thanks @dcornejo
   * Register callback with: `clixon_pagination_cb_register()`
   * Use accessor functions `pagination_offset()`, `pagination_limit()`, etc
 * Reverted state data callback API to pre-5.3 (see C/CLI API changes below)

lib/clixon/clixon.h.in

@@ -108,6 +108,7 @@ extern "C" {
 #include <clixon/clixon_xml_nsctx.h>
 #include <clixon/clixon_xml_vec.h>
 #include <clixon/clixon_client.h>
+#include <clixon/clixon_dispatcher.h>
 
 /*
  * Global variables generated by Makefile

lib/clixon/clixon_data.h

@@ -61,10 +61,15 @@ typedef struct {
 /*
  * Prototypes
  */
+/* Generic clixon data API the form <name>=<val> where <val> is string */
 int clicon_data_get(clicon_handle h, const char *name, char **val);
 int clicon_data_set(clicon_handle h, const char *name, char *val);
 int clicon_data_del(clicon_handle h, const char *name);
 
+int clicon_ptr_get(clicon_handle h, const char *name, void **ptr);
+int clicon_ptr_set(clicon_handle h, const char *name, void *ptr);
+int clicon_ptr_del(clicon_handle h, const char *name);
+
 cvec *clicon_data_cvec_get(clicon_handle h, const char *name);
 int   clicon_data_cvec_set(clicon_handle h, const char *name, cvec *cvv);
 int   clicon_data_cvec_del(clicon_handle h, const char *name);

lib/clixon/clixon_dispatcher.h

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2021 Rubicon Communications LLC (Netgate)
+ * @see https://github.com/dcornejo/dispatcher
+ */
+
+#ifndef DISPATCH_DISPATCHER_H
+#define DISPATCH_DISPATCHER_H
+
+/*! prototype for a function to handle a path
+ * minimally needs the path it's working on, but probably
+ * we want to hand down cached data somehow
+ * @param[in]  h        Generic handler
+ * @param[in]  xpath    Registered XPath using canonical prefixes
+ * @param[in]  userargs Per-call user arguments
+ * @param[in]  arg      Per-path user argument
+ */
+typedef int (*handler_function)(void *handle, char *path, void *userargs, void *arg);
+
+/*
+ * this structure is used to map a handler to a path
+ */
+typedef struct {
+    char            *dd_path;
+    handler_function dd_handler;
+} dispatcher_definition;
+
+/*
+ * the dispatcher_entry_t is the structure created from
+ * the registered dispatcher_definitions
+ */
+struct _dispatcher_entry;
+typedef struct _dispatcher_entry dispatcher_entry_t;
+
+struct _dispatcher_entry {
+    /*
+     * the name of this node, NOT the complete path
+     */
+    char *node_name;
+
+    /*
+     * peer points at peer to the right of this one
+     * if NULL then this is the rightmost and last on list
+     */
+    dispatcher_entry_t *peer;
+
+    /*
+     * peer_head points at leftmost peer at this level
+     * if NULL, then this is the leftmost and first on the list
+     */
+    dispatcher_entry_t *peer_head;
+
+    /*
+     * points at peer_head of children list
+     * if NULL, then no children
+     */
+    dispatcher_entry_t *children;
+
+    /*
+     * pointer to handler function for this node
+     */
+    handler_function handler;
+
+    /*
+     * End-user argument
+     */
+    void *arg;
+};
+
+/*
+ * Prototypes
+ */
+int dispatcher_register_handler(dispatcher_entry_t **root, dispatcher_definition *x);
+int dispatcher_call_handlers(dispatcher_entry_t *root, void *handle, char *path, void *user_args);
+
+#endif /* DISPATCH_DISPATCHER_H */

lib/clixon/clixon_plugin.h

@@ -217,24 +217,21 @@ enum pagination_mode{
 typedef enum pagination_mode pagination_mode_t;
 
 /* Plugin statedata
- * @param[in]  Clicon handle
+ * @param[in]  h          Clicon handle
  * @param[in]  xpath      Part of state requested
  * @param[in]  nsc        XPATH namespace context.
- * @param[in]  pagmode    List pagination mode
- * @param[in]  offset     Offset, for list pagination
- * @param[in]  limit      Limit, for list pagination
- * @param[out] remaining  Remaining elements (if limit is non-zero)
  * @param[out] xtop       XML tree where statedata is added
  * @retval    -1          Fatal error
  * @retval     0          OK
  */
-typedef int (plgstatedata_t)(clicon_handle h, cvec *nsc, char *xpath,
-			      pagination_mode_t pagmode,
-			      uint32_t offset, uint32_t limit,
-			      uint32_t *remaining, 
-			      cxobj *xtop);
+typedef int (plgstatedata_t)(clicon_handle h, cvec *nsc, char *xpath, cxobj *xtop);
 
-/*! Lock databse status has changed status
+/* Pagination-data type
+ * @see pagination_data_t in clixon_backend_transaction.h for full pagination API 
+ */
+typedef void *pagination_data;
+
+/*! Lock database status has changed status
  * @param[in]  h    Clixon handle
  * @param[in]  db   Database name (eg "running")
  * @param[in]  lock Lock status: 0: unlocked, 1: locked