dictionary improvements (#13052)

* fix typo in foreach write; added unit tests to traverse empty dictionaries

* rename variable dfe in macro to be uniform with name variable

2 files changed, 7 insertions, 5 deletions

diff --git a/libnetdata/dictionary/dictionary.c b/libnetdata/dictionary/dictionary.c
index de182cb023..1293491651 100644
--- a/libnetdata/dictionary/dictionary.c
+++ b/libnetdata/dictionary/dictionary.c
@@ -1253,6 +1253,8 @@ int dictionary_unittest(size_t entries) {
     dict = dictionary_create(DICTIONARY_FLAG_WITH_STATISTICS|DICTIONARY_FLAG_NAME_LINK_DONT_CLONE|DICTIONARY_FLAG_VALUE_LINK_DONT_CLONE|DICTIONARY_FLAG_DONT_OVERWRITE_VALUE);
     dictionary_unittest_run_and_measure_time(dict, "adding entries", names, values, entries, &errors, dictionary_unittest_set_nonclone);
     dictionary_unittest_run_and_measure_time(dict, "foreach write delete this", names, values, entries, &errors, dictionary_unittest_foreach_delete_this);
+    dictionary_unittest_run_and_measure_time(dict, "traverse foreach read loop empty", names, values, 0, &errors, dictionary_unittest_foreach);
+    dictionary_unittest_run_and_measure_time(dict, "walkthrough read callback empty", names, values, 0, &errors, dictionary_unittest_walkthrough);
     dictionary_unittest_run_and_measure_time(dict, "destroying empty dictionary", names, values, entries, &errors, dictionary_unittest_destroy);
 
     dictionary_unittest_free_char_pp(names, entries);
diff --git a/libnetdata/dictionary/dictionary.h b/libnetdata/dictionary/dictionary.h
index 1aeeb78f3c..7b9da3a380 100644
--- a/libnetdata/dictionary/dictionary.h
+++ b/libnetdata/dictionary/dictionary.h
@@ -154,17 +154,17 @@ typedef DICTFE_CONST struct dictionary_foreach {
 } DICTFE;
 
 #define dfe_start_read(dict, value) dfe_start_rw(dict, value, 'r')
-#define dfe_start_write(dict, value) dfe_start_rw(dict, value, 'r')
+#define dfe_start_write(dict, value) dfe_start_rw(dict, value, 'w')
 #define dfe_start_rw(dict, value, mode) \
         do { \
-            DICTFE dfe_ ## value = {};  \
+            DICTFE value ## _dfe = {};  \
             const char *value ## _name; (void)(value ## _name); \
-            for((value) = dictionary_foreach_start_rw(&dfe_ ## value, (dict), (mode)), ( value ## _name ) = dfe_ ## value.name; \
+            for((value) = dictionary_foreach_start_rw(&value ## _dfe, (dict), (mode)), ( value ## _name ) = value ## _dfe.name; \
                 (value) ;\
-                (value) = dictionary_foreach_next(&dfe_ ## value), ( value ## _name ) = dfe_ ## value.name)
+                (value) = dictionary_foreach_next(&value ## _dfe), ( value ## _name ) = value ## _dfe.name)
 
 #define dfe_done(value) \
-            dictionary_foreach_done(&dfe_ ## value); \
+            dictionary_foreach_done(&value ## _dfe); \
         } while(0)
 
 extern void * dictionary_foreach_start_rw(DICTFE *dfe, DICTIONARY *dict, char rw);