erts: Change external format for maps

to be: 116,Arity, K1,V1,K2,V2,...,Kn,Vn

instead of: 116,Arity, K1,K2,...,Kn, V1,V2,....,Vn

We think this will be better for future internal map structures
like HAMT. Would be bad if we need to iterate twice over HAMT
in term_to_binary, one for keys and one for values.

2 files changed, 11 insertions, 12 deletions

diff --git a/lib/erl_interface/doc/src/ei.xml b/lib/erl_interface/doc/src/ei.xml
index 1756ee8a7d..90495eebd6 100644
--- a/lib/erl_interface/doc/src/ei.xml
+++ b/lib/erl_interface/doc/src/ei.xml
@@ -422,19 +422,18 @@ ei_x_encode_empty_list(&x);
       <fsummary>Encode a map</fsummary>
       <desc>
         <p>This function encodes a map header, with a specified arity. The next
-	   <c>arity</c> terms encoded will be the keys of the map, and the next
-	   <c>arity</c> terms after that will be the corresponding values in
-	   same order.</p>
+	   <c>arity*2</c> terms encoded will be the keys and values of the map
+	   encoded in the following order: <c>K1, V1, K2, V2, ..., Kn, Vn</c>.
+	</p>
         <p>E.g. to encode the map <c>#{a => "Apple", b => "Banana"}</c>:</p>
         <pre>
 ei_x_encode_map_header(&amp;x, 2);
 ei_x_encode_atom(&amp;x, "a");
-ei_x_encode_atom(&amp;x, "b");
 ei_x_encode_string(&amp;x, "Apple");
+ei_x_encode_atom(&amp;x, "b");
 ei_x_encode_string(&amp;x, "Banana");
         </pre>
-	<p>A correctly encoded map can not have duplicate keys, but no check
-	for duplicate keys is done by this function.</p>
+	<p>A correctly encoded map can not have duplicate keys.</p>
       </desc>
     </func>
     <func>
@@ -664,10 +663,9 @@ ei_x_encode_string(&amp;x, "Banana");
       <desc>
         <p>This function decodes a map header from the binary
           format. The number of key-value pairs is returned in
-          <c>arity</c>. Keys and values follows, first all keys and then all values,
-	  which makes a total of <c>arity*2</c> terms.
-	  Keys and values are paired according to their order, the first key
-	  with the first value and so on. If <c>arity</c> is zero, it's an empty map.
+          <c>*arity</c>. Keys and values follow in the following order:
+	  <c>K1, V1, K2, V2, ..., Kn, Vn</c>. This makes a total of
+	  <c>arity*2</c> terms. If <c>arity</c> is zero, it's an empty map.
 	  A correctly encoded map does not have duplicate keys.</p>
       </desc>
     </func>
diff --git a/lib/erl_interface/test/ei_decode_encode_SUITE_data/ei_decode_encode_test.c b/lib/erl_interface/test/ei_decode_encode_SUITE_data/ei_decode_encode_test.c
index 790d498a1d..fcf546105b 100644
--- a/lib/erl_interface/test/ei_decode_encode_SUITE_data/ei_decode_encode_test.c
+++ b/lib/erl_interface/test/ei_decode_encode_SUITE_data/ei_decode_encode_test.c
@@ -527,8 +527,9 @@ TESTCASE(test_ei_decode_encode)
 
     { /* #{atom => atom, atom => pid, port => ref }*/
 	struct Type* map[] = { &map_type,
-	    &my_atom_type, &my_atom_type, &port_type,
-	    &my_atom_type, &pid_type, &ref_type
+	    &my_atom_type, &my_atom_type,
+	    &my_atom_type, &pid_type,
+	    &port_type, &ref_type
 	};
 	decode_encode(map, 7);
     }