1.1 --- a/libraries/json/json.c	Wed Jul 30 22:32:33 2014 +0200
     1.2 +++ b/libraries/json/json.c	Wed Jul 30 22:56:21 2014 +0200
     1.3 @@ -651,22 +651,34 @@
     1.4  #define json_pairs_iterfunc_shadowtbl_idx 4
     1.5  
     1.6  static int json_pairs_iterfunc(lua_State *L) {
     1.7 +  // stack shall contain two function arguments:
     1.8    lua_settop(L, 2);
     1.9 -  json_pushlightref(L, nullmark);  // on stack position 3
    1.10 +  // push nullmark onto stack position 3:
    1.11 +  json_pushlightref(L, nullmark);
    1.12 +  // push shadowtbl onto stack position 4:
    1.13    json_regfetch(L, shadowtbl);
    1.14 +  // get corresponding shadow table for first argument:
    1.15    lua_pushvalue(L, 1);
    1.16    lua_rawget(L, json_pairs_iterfunc_shadowtbl_idx);
    1.17 +  // throw error if no shadow table was found:
    1.18    if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
    1.19 +  // get next key value pair from shadow table (using previous key from argument 2)
    1.20 +  // and return nothing if there is no next pair:
    1.21    lua_pushvalue(L, 2);
    1.22    if (!lua_next(L, -2)) return 0;
    1.23 +  // replace null-marker with nil:
    1.24    if (lua_rawequal(L, -1, json_pairs_iterfunc_nullmark_idx)) {
    1.25      lua_pop(L, 1);
    1.26      lua_pushnil(L);
    1.27    }
    1.28 +  // return key and value (or key and nil, if null-marker was found):
    1.29    return 2;
    1.30  }
    1.31  
    1.32 +// returns a triple such that 'for key, value in pairs(obj) do ... end'
    1.33 +// iterates through all key value pairs (including JSON null keys represented as Lua nil):
    1.34  static int json_pairs(lua_State *L) {
    1.35 +  // return triple of function json_pairs_iterfunc, first argument, and nil:
    1.36    lua_pushcfunction(L, json_pairs_iterfunc);
    1.37    lua_pushvalue(L, 1);
    1.38    lua_pushnil(L);
    1.39 @@ -679,28 +691,43 @@
    1.40  
    1.41  static int json_ipairs_iterfunc(lua_State *L) {
    1.42    int idx;
    1.43 +  // stack shall contain two function arguments:
    1.44    lua_settop(L, 2);
    1.45 -  json_pushlightref(L, nullmark);  // on stack position 3
    1.46 +  // push nullmark onto stack position 3:
    1.47 +  json_pushlightref(L, nullmark);
    1.48 +  // push shadowtbl onto stack position 4:
    1.49    json_regfetch(L, shadowtbl);
    1.50 +  // calculate new index by incrementing second argument:
    1.51    idx = lua_tointeger(L, 2) + 1;
    1.52 +  // get corresponding shadow table for first argument:
    1.53    lua_pushvalue(L, 1);
    1.54    lua_rawget(L, json_ipairs_iterfunc_shadowtbl_idx);
    1.55 +  // throw error if no shadow table was found:
    1.56    if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
    1.57 +  // do integer lookup in shadow table:
    1.58    lua_rawgeti(L, -1, idx);
    1.59 +  // return nothing if there was no value:
    1.60    if (lua_isnil(L, -1)) return 0;
    1.61 +  // return new index and
    1.62 +  // either the looked up value if it is not equal to the null-marker
    1.63 +  // or nil instead of null-marker:
    1.64    lua_pushinteger(L, idx);
    1.65    if (lua_rawequal(L, -2, json_ipairs_iterfunc_nullmark_idx)) lua_pushnil(L);
    1.66    else lua_pushvalue(L, -2);
    1.67    return 2;
    1.68  }
    1.69  
    1.70 +// returns a triple such that 'for idx, value in ipairs(ary) do ... end'
    1.71 +// iterates through all values (including JSON null represented as Lua nil):
    1.72  static int json_ipairs(lua_State *L) {
    1.73 +  // return triple of function json_ipairs_iterfunc, first argument, and zero:
    1.74    lua_pushcfunction(L, json_ipairs_iterfunc);
    1.75    lua_pushvalue(L, 1);
    1.76    lua_pushinteger(L, 0);
    1.77    return 3;
    1.78  }
    1.79  
    1.80 +// functions in library module:
    1.81  static const struct luaL_Reg json_module_functions[] = {
    1.82    {"object", json_object},
    1.83    {"array", json_array},
    1.84 @@ -712,6 +739,7 @@
    1.85    {NULL, NULL}
    1.86  };
    1.87  
    1.88 +// metamethods for JSON objects, JSON arrays, and unknown JSON collections (object or array):
    1.89  static const struct luaL_Reg json_metatable_functions[] = {
    1.90    {"__len", json_len},
    1.91    {"__index", json_index},
    1.92 @@ -721,29 +749,36 @@
    1.93    {NULL, NULL}
    1.94  };
    1.95  
    1.96 +// initializes json library:
    1.97  int luaopen_json(lua_State *L) {
    1.98 +  // empty stack:
    1.99    lua_settop(L, 0);
   1.100 -  lua_newtable(L);  // library
   1.101 +  // push library module onto stack position 1:
   1.102 +  lua_newtable(L);
   1.103 +  // register library functions:
   1.104 +  luaL_setfuncs(L, json_module_functions, 0);
   1.105 +  // create and store unknownmt:
   1.106    lua_newtable(L);
   1.107    luaL_setfuncs(L, json_metatable_functions, 0);
   1.108    json_regstore(L, unknownmt);
   1.109 -  lua_setfield(L, 1, "ambiguous_mt");
   1.110 +  // create and store objectmt:
   1.111    lua_newtable(L);
   1.112    luaL_setfuncs(L, json_metatable_functions, 0);
   1.113    json_regstore(L, objectmt);
   1.114 -  lua_setfield(L, 1, "object_mt");
   1.115 +  // create and store arraymt:
   1.116    lua_newtable(L);
   1.117    luaL_setfuncs(L, json_metatable_functions, 0);
   1.118    json_regstore(L, arraymt);
   1.119 -  lua_setfield(L, 1, "array_mt");
   1.120 -  lua_newtable(L);  // ephemeron table to store shadow tables for each JSON object/array to allow NULL values returned as nil
   1.121 +  // create and store ephemeron table to store shadow tables for each JSON object/array
   1.122 +  // to allow NULL values returned as nil
   1.123 +  lua_newtable(L);
   1.124    lua_newtable(L);  // metatable for ephemeron table
   1.125    lua_pushliteral(L, "__mode");
   1.126    lua_pushliteral(L, "k");
   1.127    lua_rawset(L, -3);
   1.128    lua_setmetatable(L, -2);
   1.129    json_regstore(L, shadowtbl);
   1.130 +  // return library module stored on lowest stack position:
   1.131    lua_settop(L, 1);
   1.132 -  luaL_setfuncs(L, json_module_functions, 0);
   1.133    return 1;
   1.134  }