added atPointer method

Author: FourierTransformer

README.md

@@ -71,16 +71,18 @@ local response = simdjson.open([[
     }
 }
 ]])
-print(response:at("Image/Width"))
+print(response:atPointer("/Image/Width"))
 
 -- OR to parse a file from disk
 local fileResponse = simdjson.open("jsonexamples/twitter.json")
-print(fileResponse:at("statuses/0/id")) --using a JSON pointer
+print(fileResponse:atPointer("/statuses/0/id")) --using a JSON pointer
 
 ```
+Starting with version 0.5.0, the the `atPointer` method is JSON pointer compliant. The previous pointer implementation is considered deprecated, but is still available with the `at` method.
+
 The `open` and `parse` codeblocks should print out the same values. It's worth noting that the JSON pointer indexes from 0.
 
-This lazy style of using the simdjson data structure could also be used with array access in the future, and would result in ultra-fast JSON parsing.
+This lazy style of using the simdjson data structure could also be used with array access in the future, and would result in ultra-fast JSON "parsing".
 
 ## Error Handling
 lua-simdjson will error out with any errors from simdjson encountered while parsing. They are very good at helping identify what has gone wrong during parsing.

src/luasimdjson.cpp

@@ -210,13 +210,34 @@ static int ParsedObject_at(lua_State *L) {
     return 1;
 }
 
+static int ParsedObject_atPointer(lua_State *L) {
+    dom::document* document = (*reinterpret_cast<ParsedObject**>(luaL_checkudata(L, 1, LUA_MYOBJECT)))->get();
+    const char *pointer = luaL_checkstring(L, 2);    
+
+    dom::element returned_element;
+    simdjson::error_code error;
+
+    dom::element element = document->root();
+
+    element.at_pointer(pointer).tie(returned_element, error);
+    if (error) {
+        luaL_error(L, error_message(error));
+        return 1;
+    }
+
+    convert_element_to_table(L, returned_element);
+
+    return 1;
+}
+
 static int ParsedObject_newindex(lua_State *L) {
     luaL_error(L, "This should be treated as a read-only table. We may one day add array access for the elements, and it'll likely not be modifiable.");
     return 1;
 }
 
 static const struct luaL_Reg arraylib_m [] = {
     {"at", ParsedObject_at},
+    {"atPointer", ParsedObject_atPointer},
     {"__newindex", ParsedObject_newindex},
     {"__gc", ParsedObject_delete},
     {NULL, NULL}
@@ -242,4 +263,4 @@ int luaopen_simdjson (lua_State *L) {
     lua_setfield(L, -2, "_VERSION");
 
     return 1;
-}
+}