Add jiffy:partial_encode/2 function.

Author: David Hull

c_src/encoder.c

@@ -628,16 +628,28 @@ enc_object_element(Encoder* e, int first, ERL_NIF_TERM curr, ERL_NIF_TERM* stack
     if(!first && !enc_comma(e)) {
         return enc_error(e, "internal_error");
     }
-    if(!enc_string(e, tuple[0])) {
-        return enc_obj_error(e, "invalid_object_member_key", tuple[0]);
-    }
-    if(!enc_colon(e)) {
-        return enc_error(e, "internal_error");
+    if(enif_compare(tuple[0], e->atoms->atom_partial_object) == 0) {
+        if(!enif_is_binary(env, tuple[1])) {
+            return enc_obj_error(e, "invalid_json_string", curr);
+        }
+        if(!enc_json(e, tuple[1])) {
+            return enc_error(e, "internal_error");
+        }
+        stack = enif_make_list_cell(env, curr, stack);
+        stack = enif_make_list_cell(env, e->atoms->ref_object, stack);
+        *stackp = stack;
+    } else {
+        if(!enc_string(e, tuple[0])) {
+            return enc_obj_error(e, "invalid_object_member_key", tuple[0]);
+        }
+        if(!enc_colon(e)) {
+            return enc_error(e, "internal_error");
+        }
+        stack = enif_make_list_cell(env, curr, stack);
+        stack = enif_make_list_cell(env, e->atoms->ref_object, stack);
+        stack = enif_make_list_cell(env, tuple[1], stack);
+        *stackp = stack;
     }
-    stack = enif_make_list_cell(env, curr, stack);
-    stack = enif_make_list_cell(env, e->atoms->ref_object, stack);
-    stack = enif_make_list_cell(env, tuple[1], stack);
-    *stackp = stack;
     return 0;
 }
 
@@ -843,7 +855,8 @@ encode_iter(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
                 ret = enc_object_element(e, 1, tuple[0], &stack);
                 if (ret) { goto done; }
             } else if(arity == 2) {
-                if(enif_compare(tuple[0], e->atoms->atom_json) != 0) {
+                if((enif_compare(tuple[0], e->atoms->atom_json) != 0) &&
+                   (enif_compare(tuple[0], e->atoms->atom_partial_array) != 0)) {
                     ret = enc_obj_error(e, "invalid_ejson", curr);
                     goto done;
                 }

c_src/jiffy.c

@@ -17,6 +17,8 @@ load(ErlNifEnv* env, void** priv, ERL_NIF_TERM info)
     st->atom_true = make_atom(env, "true");
     st->atom_false = make_atom(env, "false");
     st->atom_json = make_atom(env, "json");
+    st->atom_partial_object = make_atom(env, "$partial_object$");
+    st->atom_partial_array = make_atom(env, "$partial_array$");
     st->atom_bignum = make_atom(env, "bignum");
     st->atom_bignum_e = make_atom(env, "bignum_e");
     st->atom_bigdbl = make_atom(env, "bigdbl");

c_src/jiffy.h

@@ -20,6 +20,8 @@ typedef struct {
     ERL_NIF_TERM    atom_true;
     ERL_NIF_TERM    atom_false;
     ERL_NIF_TERM    atom_json;
+    ERL_NIF_TERM    atom_partial_object;
+    ERL_NIF_TERM    atom_partial_array;
     ERL_NIF_TERM    atom_bignum;
     ERL_NIF_TERM    atom_bignum_e;
     ERL_NIF_TERM    atom_bigdbl;

src/jiffy.erl

@@ -2,7 +2,7 @@
 % See the LICENSE file for more information.
 
 -module(jiffy).
--export([decode/1, decode/2, encode/1, encode/2]).
+-export([decode/1, decode/2, encode/1, encode/2, partial_encode/2]).
 -define(NOT_LOADED, not_loaded(?LINE)).
 
 -compile([no_native]).
@@ -107,6 +107,16 @@ encode(Data, Options) ->
     end.
 
 
+-spec partial_encode(json_array(), encode_options()) -> {'$partial_array$', binary()};
+                    (json_object(), encode_options()) -> {'$partial_object$', binary()}.
+partial_encode(Data, Options) when is_list(Data) ->
+    Json = iolist_to_binary(encode(Data, Options)),
+    {'$partial_array$', binary_part(Json, 1, byte_size(Json) - 2)};
+partial_encode(Data, Options) when is_tuple(Data) ->
+    Json = iolist_to_binary(encode(Data, Options)),
+    {'$partial_object$', binary_part(Json, 1, byte_size(Json) - 2)}.
+
+
 finish_decode({bignum, Value}) ->
     list_to_integer(binary_to_list(Value));
 finish_decode({bignum_e, Value}) ->

test/jiffy_16_preencode_tests.erl

@@ -19,6 +19,11 @@ gen(ok, {E1, J, E2}) ->
         {"Decode", ?_assertEqual(E2, dec(J))}
     ]};
 
+gen(ok, {E, J}) ->
+    {msg("~p", [E]), [
+        {"Encode", ?_assertEqual(J, enc(E))}
+    ]};
+
 gen(error, E) ->
     {msg("Error: ~p", [E]), [
         ?_assertThrow({error, _}, enc(E))
@@ -45,7 +50,24 @@ cases(ok) ->
         , { [ {json, JSON}, {json, JSON} ], <<"[[1,\"a\"],[1,\"a\"]]">>, [ EJSON, EJSON ]}
         , { {[ {<<"a">>, {json, JSON}} ]}, <<"{\"a\":[1,\"a\"]}">>, {[ {<<"a">>, EJSON} ]}}
         ],
-    TopTests ++ BuriedTests;
+
+    PartialArray = jiffy:partial_encode([ 2, 3 ], []),
+    PartialArrayTests =
+        [ {[ PartialArray ], <<"[2,3]">>}
+        , {[ 1, PartialArray ], <<"[1,2,3]">>}
+        , {[ PartialArray, 4 ], <<"[2,3,4]">>}
+        , {[ 1, PartialArray, 4 ], <<"[1,2,3,4]">>}
+        ],
+
+    PartialObject = jiffy:partial_encode({[ {<<"ii">>, <<"two">>}, {<<"iii">>, 3} ]}, []),
+    PartialObjectTests =
+        [ {{[ PartialObject ]}, <<"{\"ii\":\"two\",\"iii\":3}">>}
+        , {{[ {<<"i">>, 1}, PartialObject ]}, <<"{\"i\":1,\"ii\":\"two\",\"iii\":3}">>}
+        , {{[ PartialObject, {<<"iv">>, 4} ]}, <<"{\"ii\":\"two\",\"iii\":3,\"iv\":4}">>}
+        , {{[ {<<"i">>, 1}, PartialObject, {<<"iv">>, 4} ]}, <<"{\"i\":1,\"ii\":\"two\",\"iii\":3,\"iv\":4}">>}
+        ],
+
+    TopTests ++ BuriedTests ++ PartialArrayTests ++ PartialObjectTests;
 
 cases(error) ->
     [ {json, true}