From 66c62f432b07326598ce172cf9d4b292412c0e48 Mon Sep 17 00:00:00 2001
From: EMQ-YangM <yangm@emqx.io>
Date: Wed, 18 May 2022 14:49:51 +0800
Subject: [PATCH] fix: zero padding should be to the MSB side

---
 apps/emqx/src/emqx_misc.erl                          | 3 +--
 apps/emqx_rule_engine/test/emqx_rule_funcs_SUITE.erl | 8 ++++----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/apps/emqx/src/emqx_misc.erl b/apps/emqx/src/emqx_misc.erl
index 9a16f7107..4849fe38b 100644
--- a/apps/emqx/src/emqx_misc.erl
+++ b/apps/emqx/src/emqx_misc.erl
@@ -333,8 +333,7 @@ hexstr_to_bin(B, Size) when is_binary(B) ->
         0 ->
             make_binary(B);
         8 ->
-            <<BH:((Size - 8) div 8)/binary, BL:8>> = B,
-            <<(make_binary(BH))/binary, <<(hexchar2int(BL) * 16)>>/binary>>;
+            make_binary(<<"0", B/binary>>);
         _ ->
             throw({unsupport_hex_string, B, Size})
     end.
diff --git a/apps/emqx_rule_engine/test/emqx_rule_funcs_SUITE.erl b/apps/emqx_rule_engine/test/emqx_rule_funcs_SUITE.erl
index 0514fc0e9..69da7e4de 100644
--- a/apps/emqx_rule_engine/test/emqx_rule_funcs_SUITE.erl
+++ b/apps/emqx_rule_engine/test/emqx_rule_funcs_SUITE.erl
@@ -171,10 +171,10 @@ t_term_encode(_) ->
     ).
 
 t_hexstr2bin(_) ->
-    ?assertEqual(<<99, 100, 240>>, emqx_rule_funcs:hexstr2bin(<<"6364f">>)),
-    ?assertEqual(<<160>>, emqx_rule_funcs:hexstr2bin(<<"a">>)),
-    ?assertEqual(<<240>>, emqx_rule_funcs:hexstr2bin(<<"f">>)),
-    ?assertEqual(<<80>>, emqx_rule_funcs:hexstr2bin(<<"5">>)),
+    ?assertEqual(<<6, 54, 79>>, emqx_rule_funcs:hexstr2bin(<<"6364f">>)),
+    ?assertEqual(<<10>>, emqx_rule_funcs:hexstr2bin(<<"a">>)),
+    ?assertEqual(<<15>>, emqx_rule_funcs:hexstr2bin(<<"f">>)),
+    ?assertEqual(<<5>>, emqx_rule_funcs:hexstr2bin(<<"5">>)),
     ?assertEqual(<<1, 2>>, emqx_rule_funcs:hexstr2bin(<<"0102">>)),
     ?assertEqual(<<17, 33>>, emqx_rule_funcs:hexstr2bin(<<"1121">>)).