Merge pull request #29 from uwiger/uw-maps

Uw maps

Author: uwiger

README.md

@@ -72,7 +72,7 @@ in the global Erlang term ordering. The number type is divided into several
 subtypes, to facilitate a reasonably efficient representation:
 
 
-<table border="1"><tr align="left"><th>Type</th><th>Description</th><th>Tag</th></tr><tr><td>negbig</td><td>Negative bignum</td><td>8</td></tr><tr><td>neg4</td><td>Negative 31-bit integer</td><td>9</td></tr><tr><td>pos4</td><td>Positive 31-bit integer</td><td>10</td></tr><tr><td>posbig</td><td>Positive bignum</td><td>11</td></tr><tr><td>atom</td><td>Obj of type atom()</td><td>12</td></tr><tr><td>reference</td><td>Obj of type reference()</td><td>13</td></tr><tr><td>port</td><td>Obj of type port()</td><td>14</td></tr><tr><td>pid</td><td>Obj of type pid()</td><td>15</td></tr><tr><td>tuple</td><td>Obj of type tuple()</td><td>16</td></tr><tr><td>list</td><td>Obj of type list()</td><td>17</td></tr><tr><td>binary</td><td>Obj of type binary()</td><td>18</td></tr><tr><td>bin_tail</td><td>Improper-tail marker followed by binary or bitstring</td><td>19</td></tr>
+<table border="1"><tr align="left"><th>Type</th><th>Description</th><th>Tag</th></tr><tr><td>negbig</td><td>Negative bignum</td><td>8</td></tr><tr><td>neg4</td><td>Negative 31-bit integer</td><td>9</td></tr><tr><td>pos4</td><td>Positive 31-bit integer</td><td>10</td></tr><tr><td>posbig</td><td>Positive bignum</td><td>11</td></tr><tr><td>atom</td><td>Obj of type atom()</td><td>12</td></tr><tr><td>reference</td><td>Obj of type reference()</td><td>13</td></tr><tr><td>port</td><td>Obj of type port()</td><td>14</td></tr><tr><td>pid</td><td>Obj of type pid()</td><td>15</td></tr><tr><td>tuple</td><td>Obj of type tuple()</td><td>16</td></tr><tr><td>list</td><td>Obj of type map()</td><td>17, 1</td></tr><tr><td>list</td><td>Obj of type list()</td><td>17</td></tr><tr><td>binary</td><td>Obj of type binary()</td><td>18</td></tr><tr><td>bin_tail</td><td>Improper-tail marker followed by binary or bitstring</td><td>19</td></tr>
 </table>
 
 
@@ -289,9 +289,18 @@ encode_pid(P) ->
 ```
 
 
+## 2.11 Maps ##
+
+The encoding of maps is currently experimental.
+Maps sort between tuples and lists. Since the smallest list is represented
+by `<<17, 2>>`, maps encoding starts with `<<17, 1>>` (introducing a new tag
+would break backwards compatibility), followed by the size of the map (4 bytes),
+and each Key-Value pair in the map.
+
 
 ## Modules ##
 
 
 <table width="100%" border="0" summary="list of modules">
-<tr><td><a href="http://github.com/uwiger/sext/blob/master/doc/sext.md" class="module">sext</a></td></tr></table>
+<tr><td><a href="http://github.com/uwiger/sext/blob/uw-maps/doc/sext.md" class="module">sext</a></td></tr></table>
+

doc/README.md

@@ -74,7 +74,7 @@ in the global Erlang term ordering. The number type is divided into several
 subtypes, to facilitate a reasonably efficient representation:
 
 
-<table border="1"><tr align="left"><th>Type</th><th>Description</th><th>Tag</th></tr><tr><td>negbig</td><td>Negative bignum</td><td>8</td></tr><tr><td>neg4</td><td>Negative 31-bit integer</td><td>9</td></tr><tr><td>pos4</td><td>Positive 31-bit integer</td><td>10</td></tr><tr><td>posbig</td><td>Positive bignum</td><td>11</td></tr><tr><td>atom</td><td>Obj of type atom()</td><td>12</td></tr><tr><td>reference</td><td>Obj of type reference()</td><td>13</td></tr><tr><td>port</td><td>Obj of type port()</td><td>14</td></tr><tr><td>pid</td><td>Obj of type pid()</td><td>15</td></tr><tr><td>tuple</td><td>Obj of type tuple()</td><td>16</td></tr><tr><td>list</td><td>Obj of type list()</td><td>17</td></tr><tr><td>binary</td><td>Obj of type binary()</td><td>18</td></tr><tr><td>bin_tail</td><td>Improper-tail marker followed by binary or bitstring</td><td>19</td></tr>
+<table border="1"><tr align="left"><th>Type</th><th>Description</th><th>Tag</th></tr><tr><td>negbig</td><td>Negative bignum</td><td>8</td></tr><tr><td>neg4</td><td>Negative 31-bit integer</td><td>9</td></tr><tr><td>pos4</td><td>Positive 31-bit integer</td><td>10</td></tr><tr><td>posbig</td><td>Positive bignum</td><td>11</td></tr><tr><td>atom</td><td>Obj of type atom()</td><td>12</td></tr><tr><td>reference</td><td>Obj of type reference()</td><td>13</td></tr><tr><td>port</td><td>Obj of type port()</td><td>14</td></tr><tr><td>pid</td><td>Obj of type pid()</td><td>15</td></tr><tr><td>tuple</td><td>Obj of type tuple()</td><td>16</td></tr><tr><td>list</td><td>Obj of type map()</td><td>17, 1</td></tr><tr><td>list</td><td>Obj of type list()</td><td>17</td></tr><tr><td>binary</td><td>Obj of type binary()</td><td>18</td></tr><tr><td>bin_tail</td><td>Improper-tail marker followed by binary or bitstring</td><td>19</td></tr>
 </table>
 
 
@@ -291,6 +291,14 @@ encode_pid(P) ->
 ```
 
 
+## 2.11 Maps ##
+
+The encoding of maps is currently experimental.
+Maps sort between tuples and lists. Since the smallest list is represented
+by `<<17, 2>>`, maps encoding starts with `<<17, 1>>` (introducing a new tag
+would break backwards compatibility), followed by the size of the map (4 bytes),
+and each Key-Value pair in the map.
+
 
 ## Modules ##
 

doc/overview.edoc

@@ -114,6 +114,11 @@ subtypes, to facilitate a reasonably efficient representation:
   <td>Obj of type tuple()</td>
   <td>16</td>
  </tr>
+ <tr>
+  <td>list</td>
+  <td>Obj of type map()</td>
+  <td>17, 1</td>
+ </tr>
  <tr>
   <td>list</td>
   <td>Obj of type list()</td>
@@ -308,4 +313,13 @@ The encoding of ports is perhaps best described by the code:
     NameEnc = encode_bin_elems(Name),
     <<?pid, NameEnc/binary, Rest/binary>>.]]></pre>
 
+<h2>2.11 Maps</h2>
+
+The encoding of maps is currently experimental.
+
+Maps sort between tuples and lists. Since the smallest list is represented
+by `<<17, 2>>', maps encoding starts with `<<17, 1>>' (introducing a new tag
+would break backwards compatibility), followed by the size of the map (4 bytes),
+and each Key-Value pair in the map.
+
 @end

src/sext.erl

@@ -90,6 +90,7 @@ encode(X) -> encode(X, false).
 %% Use only as transition support. This function will be deprecated in time.
 %% @end
 encode(X, Legacy) when is_tuple(X)  -> encode_tuple(X, Legacy);
+encode(X, Legacy) when is_map(X)    -> encode_map(X, Legacy);
 encode(X, Legacy) when is_list(X)   -> encode_list(X, Legacy);
 encode(X, _) when is_pid(X)         -> encode_pid(X);
 encode(X, _) when is_port(X)        -> encode_port(X);
@@ -274,6 +275,15 @@ encode_list(L, Legacy) ->
 prefix_list(L) ->
     prefix_list_elems(L, <<?list>>).
 
+encode_map(M, Legacy) ->
+    Sz = map_size(M),
+    maps:fold(
+      fun(K,V,Acc) ->
+              <<Acc/binary, (encode(K, Legacy))/binary,
+                (encode(V, Legacy))/binary>>
+      end, <<?list, 1:8, Sz:32>>, M).
+
+
 encode_binary(B)    ->
     Enc = encode_bin_elems(B),
     <<?binary:8, Enc/binary>>.
@@ -650,6 +660,9 @@ decode_next(<<?pid, Rest/binary>>) -> decode_pid(Rest);
 decode_next(<<?port, Rest/binary>>) -> decode_port(Rest);
 decode_next(<<?reference,Rest/binary>>) -> decode_ref(Rest);
 decode_next(<<?tuple,Sz:32, Rest/binary>>) -> decode_tuple(Sz,Rest);
+%% decode_next(<<?nil, Rest/binary>>) -> {[], Rest};
+%% decode_next(<<?old_list, Rest/binary>>) -> decode_list(Rest);
+decode_next(<<?list, 1, Rest/binary>>) -> decode_map(Rest);
 decode_next(<<?list, Rest/binary>>) -> decode_list(Rest);
 decode_next(<<?negbig, Rest/binary>>) -> decode_neg_big(Rest);
 decode_next(<<?posbig, Rest/binary>>) -> decode_pos_big(Rest);
@@ -753,6 +766,17 @@ partial_decode_list(<<X,_/binary>> = Next, Acc) when ?is_sext(X) ->
 partial_decode_list(Rest, Acc) ->
     {partial, lists:reverse(Acc) ++ '_', Rest}.
 
+decode_map(<<Sz:32, Rest/binary>>) ->
+    decode_map(Sz, Rest, #{}).
+
+decode_map(0, Rest, M) ->
+    {M, Rest};
+decode_map(N, Bin, M) ->
+    {K, Bin1} = decode_next(Bin),
+    {V, Bin2} = decode_next(Bin1),
+    decode_map(N-1, Bin2, maps:put(K, V, M)).
+
+
 decode_list(Elems) ->
     decode_list(Elems, []).