erts: Fix map iterator bug when reverting from end of map position

and simplify code by ignoring h_limit which is always zero.

3 files changed, 53 insertions, 27 deletions

diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index c6f7c8adb5..6fceb8a0ba 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -1759,13 +1759,10 @@ int enif_map_iterator_next(ErlNifEnv *env, ErlNifMapIterator *iter)
     ASSERT(iter && is_map(iter->map));
     if (iter->idx < iter->t_limit) {
 	iter->idx++;
-	if (iter->idx != iter->t_limit) {
-	    iter->ks++;
-	    iter->vs++;
-	    return 1;
-	}
+	iter->ks++;
+	iter->vs++;
     }
-    return 0;
+    return (iter->idx != iter->t_limit);
 }
 
 int enif_map_iterator_prev(ErlNifEnv *env, ErlNifMapIterator *iter)
@@ -1773,13 +1770,10 @@ int enif_map_iterator_prev(ErlNifEnv *env, ErlNifMapIterator *iter)
     ASSERT(iter && is_map(iter->map));
     if (iter->idx > 0) {
 	iter->idx--;
-	if (iter->idx != 0) {
-	    iter->ks--;
-	    iter->vs--;
-	    return 1;
-	}
+	iter->ks--;
+	iter->vs--;
     }
-    return 0;
+    return (iter->idx > 0);
 }
 
 int enif_map_iterator_get_pair(ErlNifEnv *env,
diff --git a/erts/emulator/test/nif_SUITE.erl b/erts/emulator/test/nif_SUITE.erl
index 5b7c310aa4..a34f70c618 100644
--- a/erts/emulator/test/nif_SUITE.erl
+++ b/erts/emulator/test/nif_SUITE.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2010-2013. All Rights Reserved.
+%% Copyright Ericsson AB 2010-2014. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -449,6 +449,9 @@ maps(Config) when is_list(Config) ->
     io:format("Pairs: ~p~nMap: ~p~nReturned: ~p~n", [lists:sort(Pairs),M,R]),
     Is = lists:sort(Pairs),
     Is = lists:reverse(RIs),
+
+    #{} = maps_from_list([]),
+    {[],[]} = sorted_list_from_maps(#{}),
     ok.
  
 api_macros(doc) -> ["Test macros enif_make_list<N> and enif_make_tuple<N>"];
diff --git a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
index a0316a7861..8549d277de 100644
--- a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
+++ b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 2009-2013. All Rights Reserved.
+ * Copyright Ericsson AB 2009-2014. All Rights Reserved.
  *
  * The contents of this file are subject to the Erlang Public License,
  * Version 1.1, (the "License"); you may not use this file except in
@@ -1564,31 +1564,60 @@ static ERL_NIF_TERM sorted_list_from_maps(ErlNifEnv* env, int argc, const ERL_NI
     ERL_NIF_TERM map = argv[0];
     ERL_NIF_TERM list_f = enif_make_list(env, 0); /* NIL */
     ERL_NIF_TERM list_b = enif_make_list(env, 0); /* NIL */
-    ERL_NIF_TERM key, value;
-    ErlNifMapIterator iter;
+    ERL_NIF_TERM key, value, k2, v2;
+    ErlNifMapIterator iter_f;
+    ErlNifMapIterator iter_b;
+    int cnt, next_ret, prev_ret;
 
     if (argc != 1 && !enif_is_map(env, map))
-	return enif_make_badarg(env);
+	return enif_make_int(env, __LINE__);
 
-    if(!enif_map_iterator_create(env, map, &iter, ERL_NIF_MAP_ITERATOR_HEAD))
-	return enif_make_badarg(env);
+    if(!enif_map_iterator_create(env, map, &iter_f, ERL_NIF_MAP_ITERATOR_HEAD))
+	return enif_make_int(env, __LINE__);
 
-    while(enif_map_iterator_get_pair(env,&iter,&key,&value)) {
+    cnt = 0;
+    while(enif_map_iterator_get_pair(env,&iter_f,&key,&value)) {
+	if (cnt && !next_ret)
+	    return enif_make_int(env, __LINE__);
 	list_f = enif_make_list_cell(env, enif_make_tuple2(env, key, value), list_f);
-	enif_map_iterator_next(env,&iter);
+	next_ret = enif_map_iterator_next(env,&iter_f);
+	cnt++;
     }
+    if (cnt && next_ret)
+	return enif_make_int(env, __LINE__);
 
-    enif_map_iterator_destroy(env, &iter);
+    if(!enif_map_iterator_create(env, map, &iter_b, ERL_NIF_MAP_ITERATOR_TAIL))
+	return enif_make_int(env, __LINE__);
 
-    if(!enif_map_iterator_create(env, map, &iter, ERL_NIF_MAP_ITERATOR_TAIL))
-	return enif_make_badarg(env);
+    cnt = 0;
+    while(enif_map_iterator_get_pair(env,&iter_b,&key,&value)) {
+	if (cnt && !prev_ret)
+	    return enif_make_int(env, __LINE__);
+
+	/* Test that iter_f can step "backwards" */
+	if (!enif_map_iterator_prev(env,&iter_f)
+	    || !enif_map_iterator_get_pair(env,&iter_f,&k2,&v2)
+	    || k2 != key || v2 != value) {
+	    return enif_make_int(env, __LINE__);
+	}
 
-    while(enif_map_iterator_get_pair(env,&iter,&key,&value)) {
 	list_b = enif_make_list_cell(env, enif_make_tuple2(env, key, value), list_b);
-	enif_map_iterator_prev(env,&iter);
+	prev_ret = enif_map_iterator_prev(env,&iter_b);
+    }
+
+    if (cnt) {
+	if (prev_ret || enif_map_iterator_prev(env,&iter_f))
+	    return enif_make_int(env, __LINE__);
+
+	/* Test that iter_b can step "backwards" one step */
+	if (!enif_map_iterator_next(env, &iter_b)
+	    || !enif_map_iterator_get_pair(env,&iter_b,&k2,&v2)
+	    || k2 != key || v2 != value)
+	    return enif_make_int(env, __LINE__);
     }
 
-    enif_map_iterator_destroy(env, &iter);
+    enif_map_iterator_destroy(env, &iter_f);
+    enif_map_iterator_destroy(env, &iter_b);
 
     return enif_make_tuple2(env, list_f, list_b);
 }