# HG changeset patch
# User jbe
# Date 1406345262 -7200
# Node ID 402fce94f98c4837f686929b181352ac1abd3271
# Parent  ff39d4a310b984e598a5c26338b5f75c922d5fc4
Added function json.isnull(...) to JSON library

diff -r ff39d4a310b9 -r 402fce94f98c libraries/json/json.c
--- a/libraries/json/json.c	Fri Jul 25 22:50:12 2014 +0200
+++ b/libraries/json/json.c	Sat Jul 26 05:27:42 2014 +0200
@@ -3,6 +3,9 @@
 #include <stdlib.h>
 #include <string.h>
 
+#define JSON_UPVAL_ARYLEN lua_upvalueindex(1)
+#define JSON_UPVAL_NULLS lua_upvalueindex(2)
+
 #define JSON_VALUE 0
 #define JSON_OBJECT_KEY 1
 #define JSON_OBJECT_KEY_TERMINATOR 2
@@ -41,6 +44,10 @@
       goto json_import_syntax_error;
     pos++;
     lua_newtable(L);
+    lua_newtable(L);  // stores set of NULL values
+    lua_pushvalue(L, -2);
+    lua_pushvalue(L, -2);
+    lua_rawset(L, JSON_UPVAL_NULLS);
     mode = JSON_OBJECT_KEY;
     level++;
     goto json_import_loop;
@@ -49,6 +56,10 @@
       goto json_import_syntax_error;
     pos++;
     lua_newtable(L);
+    lua_newtable(L);  // stores set of NULL values
+    lua_pushvalue(L, -2);
+    lua_pushvalue(L, -2);
+    lua_rawset(L, JSON_UPVAL_NULLS);
     lua_pushinteger(L, 0);  // length of array (since it may contain nil's)
     mode = JSON_ARRAY_VALUE;
     level++;
@@ -62,10 +73,11 @@
       goto json_import_syntax_error;
     lua_pushvalue(L, -2);  // use array table as key
     lua_insert(L, -2);  // use length of array as value
-    lua_rawset(L, lua_upvalueindex(1));  // store length in ephemeron table
+    lua_rawset(L, JSON_UPVAL_ARYLEN);  // store length in ephemeron table
     // leaves array table on top of stack
   json_import_close:
     pos++;
+    lua_pop(L, 1);  // pop table that stores set of NULL values
     if (--level) {
       if (lua_type(L, -2) == LUA_TNUMBER) {
         mode = JSON_ARRAY_VALUE;
@@ -172,12 +184,22 @@
     mode = JSON_OBJECT_KEY_TERMINATOR;
     goto json_import_loop;
   case JSON_OBJECT_VALUE:
-    lua_rawset(L, -3);
+    if (lua_isnil(L, -1)) {
+      lua_pushvalue(L, -2);
+      lua_pushboolean(L, 1);
+      lua_rawset(L, -5);
+    }
+    lua_rawset(L, -4);
     mode = JSON_OBJECT_SEPARATOR;
     goto json_import_loop;
   case JSON_ARRAY_VALUE:
     aryidx = lua_tointeger(L, -2) + 1;
-    lua_rawseti(L, -3, aryidx);
+    if (lua_isnil(L, -1)) {
+      lua_pushinteger(L, aryidx);
+      lua_pushboolean(L, 1);
+      lua_rawset(L, -5);
+    }
+    lua_rawseti(L, -4, aryidx);
     lua_pop(L, 1);
     lua_pushinteger(L, aryidx);
     mode = JSON_ARRAY_SEPARATOR;
@@ -194,24 +216,40 @@
 
 static int json_arylen(lua_State *L) {
   lua_settop(L, 1);
-  lua_rawget(L, lua_upvalueindex(1));
+  lua_rawget(L, JSON_UPVAL_ARYLEN);
+  return 1;
+}
+
+static int json_isnull(lua_State *L) {
+  lua_pushvalue(L, 1);
+  lua_rawget(L, JSON_UPVAL_NULLS);
+  if (lua_isnil(L, -1)) goto json_isnull_false;
+  lua_pushvalue(L, 2);
+  lua_rawget(L, -2);
+  if (!lua_isnil(L, -1)) return 1;
+json_isnull_false:
+  lua_pushboolean(L, 0);
   return 1;
 }
 
 static const struct luaL_Reg json_module_functions[] = {
   {"import", json_import},
   {"arylen", json_arylen},
+  {"isnull", json_isnull},
   {NULL, NULL}
 };
 
 int luaopen_json(lua_State *L) {
   lua_newtable(L);  // library table
   lua_newtable(L);  // ephemeron table to store the length of arrays (that may contain nil's)
+  lua_newtable(L);  // ephemeron table to store a set of keys associated with JSON-null values
   lua_newtable(L);  // meta table for ephemeron table
   lua_pushliteral(L, "__mode");
   lua_pushliteral(L, "k");
   lua_rawset(L, -3);
+  lua_pushvalue(L, -1);
+  lua_setmetatable(L, -3);
   lua_setmetatable(L, -2);
-  luaL_setfuncs(L, json_module_functions, 1);
+  luaL_setfuncs(L, json_module_functions, 2);
   return 1;
 }