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Adding support for an extra json_encode argument for empty table encoding resolution #48

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Adding support for an extra json_encode argument for empty table encoding resolution #48

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48 changes: 37 additions & 11 deletions lua_cjson.c
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Original file line number Diff line number Diff line change
Expand Up @@ -561,14 +561,14 @@ static void json_check_encode_depth(lua_State *l, json_config_t *cfg,
}

static void json_append_data(lua_State *l, json_config_t *cfg,
int current_depth, strbuf_t *json);
int current_depth, char have_empty_array_lookup_table, strbuf_t *json);

/* json_append_array args:
* - lua_State
* - JSON strbuf
* - Size of passwd Lua array (top of stack) */
static void json_append_array(lua_State *l, json_config_t *cfg, int current_depth,
strbuf_t *json, int array_length)
char have_empty_array_lookup_table, strbuf_t *json, int array_length)
{
int comma, i;

Expand All @@ -582,7 +582,7 @@ static void json_append_array(lua_State *l, json_config_t *cfg, int current_dept
comma = 1;

lua_rawgeti(l, -1, i);
json_append_data(l, cfg, current_depth, json);
json_append_data(l, cfg, current_depth, have_empty_array_lookup_table, json);
lua_pop(l, 1);
}

Expand Down Expand Up @@ -628,7 +628,7 @@ static void json_append_number(lua_State *l, json_config_t *cfg,
}

static void json_append_object(lua_State *l, json_config_t *cfg,
int current_depth, strbuf_t *json)
int current_depth, char have_empty_array_lookup_table, strbuf_t *json)
{
int comma, keytype;

Expand Down Expand Up @@ -660,17 +660,28 @@ static void json_append_object(lua_State *l, json_config_t *cfg,
}

/* table, key, value */
json_append_data(l, cfg, current_depth, json);
json_append_data(l, cfg, current_depth, have_empty_array_lookup_table, json);
lua_pop(l, 1);
/* table, key */
}

strbuf_append_char(json, '}');
}

/* Check if the current empty table (at index -1) is contained in the empty-array lookup table (at index 1). */
static char json_is_current_empty_table_an_array(lua_State *l)
{
char ret;
lua_pushvalue(l, -1);
lua_gettable(l, 1);
ret = lua_toboolean(l, -1);
lua_pop(l, 1);
return ret;
}

/* Serialise Lua data into JSON string. */
static void json_append_data(lua_State *l, json_config_t *cfg,
int current_depth, strbuf_t *json)
int current_depth, char have_empty_array_lookup_table, strbuf_t *json)
{
int len;

Expand All @@ -691,10 +702,10 @@ static void json_append_data(lua_State *l, json_config_t *cfg,
current_depth++;
json_check_encode_depth(l, cfg, current_depth, json);
len = lua_array_length(l, cfg, json);
if (len > 0)
json_append_array(l, cfg, current_depth, json, len);
if ((len > 0) || ((len == 0 ) && have_empty_array_lookup_table && json_is_current_empty_table_an_array(l)))
json_append_array(l, cfg, current_depth, have_empty_array_lookup_table, json, len);
else
json_append_object(l, cfg, current_depth, json);
json_append_object(l, cfg, current_depth, have_empty_array_lookup_table, json);
break;
case LUA_TNIL:
strbuf_append_mem(json, "null", 4);
Expand All @@ -719,8 +730,23 @@ static int json_encode(lua_State *l)
strbuf_t *encode_buf;
char *json;
int len;
char have_empty_array_lookup_table =0;

luaL_argcheck(l, lua_gettop(l) == 1, 1, "expected 1 argument");
if ((lua_gettop(l) == 2) && (lua_type(l, 2) == LUA_TTABLE)) {
/*
* An empty-array lookup table is supplied; swap arguments as
* further code expects value at the top, and the lookup table
* at index 1.
*/
lua_insert(l, -2);
have_empty_array_lookup_table = 1;
} else if ((lua_gettop(l) == 2) && !lua_toboolean(l, 2))
/*
* A false-valued empty-array lookup table is supplied; drop it.
*/
lua_pop(l, 1);
else
luaL_argcheck(l, lua_gettop(l) == 1, 1, "expected 1 argument");

if (!cfg->encode_keep_buffer) {
/* Use private buffer */
Expand All @@ -732,7 +758,7 @@ static int json_encode(lua_State *l)
strbuf_reset(encode_buf);
}

json_append_data(l, cfg, 0, encode_buf);
json_append_data(l, cfg, 0, have_empty_array_lookup_table, encode_buf);
json = strbuf_string(encode_buf, &len);

lua_pushlstring(l, json, len);
Expand Down