context: add add_to_dict/remove_from_dict APIs

This patch adds add_to_dict and remove_from_dict API, which allows to
create internal string reference within the context.

Closes: #102
Signed-off-by: Stefan Gula <steweg@gmail.com>

Author: steweg

cffi/cdefs.h

@@ -1071,6 +1071,9 @@ LY_ERR lys_parse(struct ly_ctx *, struct ly_in *, LYS_INFORMAT, const char **, s
 LY_ERR ly_ctx_new_ylpath(const char *, const char *, LYD_FORMAT, int, struct ly_ctx **);
 LY_ERR ly_ctx_get_yanglib_data(const struct ly_ctx *, struct lyd_node **, const char *, ...);
 
+LY_ERR lydict_insert(const struct ly_ctx *, const char *, size_t, const char **);
+LY_ERR lydict_remove(const struct ly_ctx *, const char *);
+
 struct lyd_meta {
     struct lyd_node *parent;
     struct lyd_meta *next;

libyang/context.py

@@ -465,3 +465,13 @@ def __iter__(self) -> Iterator[Module]:
         while mod:
             yield Module(self, mod)
             mod = lib.ly_ctx_get_module_iter(self.cdata, idx)
+
+    def add_to_dict(self, orig_str: str) -> Any:
+        cstr = ffi.new("char **")
+        ret = lib.lydict_insert(self.cdata, str2c(orig_str), 0, cstr)
+        if ret != lib.LY_SUCCESS:
+            raise LibyangError("Unable to insert string into context dictionary")
+        return cstr[0]
+
+    def remove_from_dict(self, orig_str: str) -> None:
+        lib.lydict_remove(self.cdata, str2c(orig_str))

tests/test_context.py

@@ -5,6 +5,7 @@
 import unittest
 
 from libyang import Context, LibyangError, Module, SLeaf, SLeafList
+from libyang.util import c2str
 
 
 YANG_DIR = os.path.join(os.path.dirname(__file__), "yang")
@@ -111,3 +112,10 @@ def test_ctx_leafref_extended(self):
         with Context(YANG_DIR, leafref_extended=True) as ctx:
             mod = ctx.load_module("yolo-leafref-extended")
             self.assertIsInstance(mod, Module)
+
+    def test_context_dict(self):
+        with Context(YANG_DIR) as ctx:
+            orig_str = "teststring"
+            handle = ctx.add_to_dict(orig_str)
+            self.assertEqual(orig_str, c2str(handle))
+            ctx.remove_from_dict(orig_str)