added ability to use NULL_STRING in KeyValues natives

--HG--
extra : convert_revision : svn%3A39bc706e-5318-0410-9160-8a85361fbb7c/trunk%401006

core/vm/sp_vm_basecontext.cpp

@@ -83,6 +83,15 @@ BaseContext::BaseContext(sp_context_t *_ctx)
 	} else {
 		m_pNullVec = NULL;
 	}
+
+	if (FindPubvarByName("NULL_STRING", &index) == SP_ERROR_NONE)
+	{
+		sp_pubvar_t *pubvar;
+		GetPubvarByIndex(index, &pubvar);
+		m_pNullString = pubvar->offs;
+	} else {
+		m_pNullString = NULL;
+	}
 }
 
 void BaseContext::FlushFunctionCache()
@@ -992,6 +1001,22 @@ IPluginFunction *BaseContext::GetFunctionByName(const char *public_name)
 	return pFunc;
 }
 
+int BaseContext::LocalToStringNULL(cell_t local_addr, char **addr)
+{
+	int err;
+	if ((err = LocalToString(local_addr, addr)) != SP_ERROR_NONE)
+	{
+		return err;
+	}
+
+	if ((cell_t *)*addr == m_pNullString)
+	{
+		*addr = NULL;
+	}
+
+	return SP_ERROR_NONE;
+}
+
 #if defined SOURCEMOD_BUILD
 SourceMod::IdentityToken_t *BaseContext::GetIdentity()
 {

core/vm/sp_vm_basecontext.h

@@ -70,6 +70,7 @@ namespace SourcePawn
 		SourceMod::IdentityToken_t *GetIdentity();
 		void SetIdentity(SourceMod::IdentityToken_t *token);
 		cell_t *GetNullRef(SP_NULL_TYPE type);
+		int LocalToStringNULL(cell_t local_addr, char **addr);
 #endif
 	public: //IPluginDebugInfo
 		int LookupFile(ucell_t addr, const char **filename);
@@ -86,6 +87,7 @@ namespace SourcePawn
 #if defined SOURCEMOD_BUILD
 		SourceMod::IdentityToken_t *m_pToken;
 		cell_t *m_pNullVec;
+		cell_t *m_pNullString;
 #endif
 		char m_MsgCache[1024];
 		bool m_CustomMsg;