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.

5 files changed, 20 insertions, 24 deletions

diff --git a/lib/debugger/test/map_SUITE.erl b/lib/debugger/test/map_SUITE.erl
index e9f4ea1fad..741ad2dc41 100644
--- a/lib/debugger/test/map_SUITE.erl
+++ b/lib/debugger/test/map_SUITE.erl
@@ -790,16 +790,16 @@ t_map_encode_decode(Config) when is_list(Config) ->
 
     %% literally #{ b=>2, a=>1 } in the internal order
     #{ a:=1, b:=2 } =
-	erlang:binary_to_term(<<131,116,0,0,0,2,100,0,1,98,100,0,1,97,97,2,97,1>>),
+	erlang:binary_to_term(<<131,116,0,0,0,2,100,0,1,98,97,2,100,0,1,97,97,1>>),
 
 
     %% literally #{ "hi" => "value", a=>33, b=>55 } in the internal order
     #{ a:=33, b:=55, "hi" := "value"} = erlang:binary_to_term(<<131,116,0,0,0,3,
 	107,0,2,104,105, % "hi" :: list()
-	100,0,1,97, % a :: atom()
-	100,0,1,98, % b :: atom()
 	107,0,5,118,97,108,117,101, % "value" :: list()
+	100,0,1,97, % a :: atom()
 	97,33, % 33 :: integer()
+	100,0,1,98, % b :: atom()
 	97,55  % 55 :: integer()
 	>>),
 
@@ -829,7 +829,8 @@ map_encode_decode_and_match([{K,V}|Pairs], EncodedPairs, M0) ->
     B0 = erlang:term_to_binary(M1),
     Ls = lists:sort(fun(A,B) -> erts_internal:cmp_term(A,B) < 0 end, [{K, erlang:term_to_binary(K), erlang:term_to_binary(V)}|EncodedPairs]),
     %% sort Ks and Vs according to term spec, then match it
-    ok = match_encoded_map(B0, length(Ls), [Kbin||{_,Kbin,_}<-Ls] ++ [Vbin||{_,_,Vbin}<-Ls]),
+    KVbins = lists:foldr(fun({_,Kbin,Vbin}, Acc) -> [Kbin,Vbin | Acc] end, [], Ls),
+    ok = match_encoded_map(B0, length(Ls), KVbins),
     %% decode and match it
     M1 = erlang:binary_to_term(B0),
     map_encode_decode_and_match(Pairs,Ls,M1);
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(&amp;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);
     }
diff --git a/lib/jinterface/java_src/com/ericsson/otp/erlang/OtpErlangMap.java b/lib/jinterface/java_src/com/ericsson/otp/erlang/OtpErlangMap.java
index 7c1cf84e98..03c18e55a2 100644
--- a/lib/jinterface/java_src/com/ericsson/otp/erlang/OtpErlangMap.java
+++ b/lib/jinterface/java_src/com/ericsson/otp/erlang/OtpErlangMap.java
@@ -125,8 +125,6 @@ public class OtpErlangMap extends OtpErlangObject implements Serializable,
 
 	    for (int i = 0; i < arity; i++) {
 		keys[i] = buf.read_any();
-	    }
-	    for (int i = 0; i < arity; i++) {
 		values[i] = buf.read_any();
 	    }
 	} else {
@@ -227,8 +225,6 @@ public class OtpErlangMap extends OtpErlangObject implements Serializable,
 
 	for (int i = 0; i < arity; i++) {
 	    buf.write_any(keys[i]);
-	}
-	for (int i = 0; i < arity; i++) {
 	    buf.write_any(values[i]);
 	}
     }
diff --git a/lib/jinterface/test/jinterface_SUITE_data/Maps.java b/lib/jinterface/test/jinterface_SUITE_data/Maps.java
index 136a665f23..653defc621 100644
--- a/lib/jinterface/test/jinterface_SUITE_data/Maps.java
+++ b/lib/jinterface/test/jinterface_SUITE_data/Maps.java
@@ -42,16 +42,16 @@ class Maps {
 	runTest(new byte[] { (byte) 131, 116, 0, 0, 0, 1, 100, 0, 1, 97, 100,
 		0, 1, 98 }, "#{a => b}", 2);
 	// make sure keys are sorted here, jinterface doesn't reorder them
-	runTest(new byte[] { (byte) 131, 116, 0, 0, 0, 2, 97, 2, 100, 0, 1, 97,
-		106, 97, 1 }, "#{2 => [],a => 1}", 3);
+	runTest(new byte[] { (byte) 131, 116, 0, 0, 0, 2, 97, 2, 106,
+			     100, 0, 1, 97, 97, 1 }, "#{2 => [],a => 1}", 3);
 	runTest(new byte[] { (byte) 131, 116, 0, 0, 0, 1, 104, 1, 97, 3, 108,
 		0, 0, 0, 1, 100, 0, 1, 114, 106 }, "#{{3} => [r]}", 4);
 
 	try {
 	    // #{2 => [],a => 1}
 	    final OtpErlangMap map = new OtpErlangMap(new OtpInputStream(
-		    new byte[] { (byte) 131, 116, 0, 0, 0, 2, 97, 2, 100, 0, 1,
-			    97, 106, 97, 1 }));
+		  new byte[] { (byte) 131, 116, 0, 0, 0, 2, 97, 2, 106,
+			       100, 0, 1, 97, 97, 1 }));
 
 	    if (map.arity() != 2) {
 		fail(5);