I try to write a table to an ini file, everything worked until I added a line lua_tostring(L, -2) then lua_next(L, -2) began to give out an error. How this line can influence, in my understanding, I just take the value from the stack and no more. How I can fix it?
{
// Push an initial nil to init lua_next
lua_pushnil(inOutState);
// Parse the table at index
while (lua_next(inOutState, -2))
{
if (lua_isstring(inOutState, -1)) {
string key = lua_tostring(inOutState, -2);
string value = lua_tostring(inOutState, -1);
inIniTree.put(suffix + key, value);
}
else if (lua_istable(inOutState, -1)) {
suffix += lua_tostring(inOutState, -2); !!!!!! without this line function is working well !!!!!!!
setDataInIni(inOutState, inIniTree, suffix);
}
// Pop value, keep key
lua_pop(inOutState, 1);
}
return;
}
lua_tostring() replaces value in stack if value is not of type string. It means you changed key for lua_next(). You must copy value with lua_pushvalue() and then convert it to string.
if (lua_isstring(inOutState, -1)) {
lua_pushvalue(inOutState, -2);
string key = lua_tostring(inOutState, -1);
lua_pop(L, 1);
string value = lua_tostring(inOutState, -1);
inIniTree.put(suffix + key, value);
}
else if (lua_istable(inOutState, -1)) {
lua_pushvalue(inOutState, -2);
suffix += lua_tostring(inOutState, -1);
lua_pop(L, 1);
setDataInIni(inOutState, inIniTree, suffix);
}
Related
so i was trying to push a table on a function inside arguments
*lua
function test1(varlist)
print(varlist[1])
print(varlist[2])
print(varlist[3])
end
addHook("string", "string2", test1)
*cpp
static int lua_addHook(lua_State* L) {
if (lua_isstring(L, 1) && lua_isstring(L, 2) && lua_isfunction(L, 3)) {
lua_newtable(L);
lua_newtable(L);
for (size_t i = 0; i < 3; ++i) {
lua_pushinteger(L, i + 1);
lua_pushstring(L, string("string varlist: " + to_string(i)).c_str());
lua_settable(L, -3);
}
if (lua_pcall(L, 1, 0, 0) != 0) {
printf("error: %s\n", lua_tostring(L, -1));
lua_pop(L, 1);
}
}
return 1;
}
so it should printing
string varlist: 0
string varlist: 1
string varlist: 2
but i keep getting error "attempt to call a table value"
u know what the problem is?
The stack looks like this at the point of lua_pcall:
table (constructed by the loop above) # STACK TOP and arg1 to function call
table (empty) # interpreted as the function to call
function test1
string "string1"
string "string"
Getting rid of one of the lua_newtable calls should fix it.
I'm creating a C/C++ function which will be called from Lua. My function must call a library function who's signature is like this:
void libFunction( int val1, int val2, tSETTINGS * pSettings );
I'm given these C/C++ structs:
typedef struct
{
int cmd;
int arg;
} tCOMMAND;
typedef struct
{
int numberCommands;
int id;
tCOMMAND commands[1];
} tSETTINGS;
Maybe my thinking is all wrong on this, but from Lua I'm calling like this:
id = 42
val1 = 1
val2 = 2
cmd1 = { 3, 4 }
cmd2 = { 5, 6 }
commands = { cmd1, cmd2 }
settings = { #commands, id, commands }
mycfunction( val1, val2, settings )
I'm sure that I'm still not understanding the Lua stack as referenced from C++, since what I'm trying just doesn't work. My solution is able to retrieve val1, val2, #commands and id, but when I try to retrieve commands[0] and commands[1] I get {1, 2} and {2, 42} respectively.
My C++ is essentially like this (for this sample I'm discarding the values). I've already retrieved val1 and val2:
int stkNdx = 1;
lua_rawgeti(L, 3, stkNdx++ );
int numcmds = lua_tointeger(L, -1); // this successfully retrieves numberCommands 2
lua_pop(L, 1);
lua_rawgeti(L, 3, stkNdx++ );
int id = lua_tointeger(L, -1); // this successfully retrieves id 42
lua_pop(L, 1);
lua_pushvalue(L, -1 );
lua_pushnil(L);
int cmdNbr = 0;
for( lua_next(L, -2); cmdNbr < numcmds; cmdNbr++ )
{
lua_pushvalue(L, -2);
int cmd = lua_tointeger(L, -1);
int arg = lua_tointeger(L, -1);
lua_pop(L, 2);
lua_next(L, -2);
}
lua_pop(L, 1);
I've tried various permutations of lua_rawgeti() followed by lua_tonumber() and lua_pop(), with basically the same result.
This seems similar to this question, and my solution is modeled after that with no success.
Experimenting more I inserted this:
lua_pushnil(L);
while( lua_next(L, -2) )
{
if( ! lua_istable(L, -1) )
{
int v = lua_tointeger(L, -1);
}
lua_pop(L, 1);
}
This loop executes 4 times. The first 2 times the values 2 and 42 are assigned to v. The next 2 iterations skip the assignment (lua_istable returned true). So it seems that although I've already retrieved numcmds and id, they're still there on the stack. I also clearly don't understand how to iterate over the subtables when they're encountered.
Lua table indices range from [1 .. N] instead of [0 .. N-1].
Your loop should be:
int cmdNbr = 1;
for( lua_next(L, -2); cmdNbr <= numcmds; cmdNbr++ )
{
...
}
or as I prefer it:
lua_rawgeti(L, 3, 2 );
int id = lua_tointeger(L, -1); // this successfully retrieves id 42
lua_pop(L, 1);
lua_rawgeti(L, 3, 3);
{
// commands table at stack top
size_t N = lua_objlen(L,-1); // size of the table
for (int i = 1; i <= N; ++i)
{
lua_rawgeti(L,-1, i); // cmd# at stack top
{
lua_rawgeti(L,-1,1); // first entry
int cmd = lua_tointeger(L,-1);
lua_pop(L,1);
lua_rawgeti(L,-1,2); // second entry
int arg = lua_tointeger(L,-1);
lua_pop(L,1);
}
lua_pop(L, 1); // pop cmd#
}
}
lua_pop(L, 1); // pop commands table
Note that, with the function lua_objlen(L,idx), it's not necessary to pass numcmds.
I am currently using the following code to get a value from a table (cstring = const char*):
template<>
cstring luaTable::get(cstring name) {
prep_get(name); // puts table[name] at -1 in stack
cstring result;
if(!lua_isstring(L, -1)) {
report(name, "is not a string");
result = "";
}
else {
result = lua_tostring(L, -1);
}
lua_pop(L, 1);
return result;
}
void luaTable::prep_get(cstring name) {
lua_pushstring(L, name); // name at -1, table at -2
lua_gettable(L, -2);
// table[name] is now at position -1 in stack
}
This works perfectly for tables of form table = {a=10, b=2}. How can I modify it to get values from tables without keys such as table = {10, 2}?
I'm sure I'm missing something simple but can't seem to find the answer.
Thanks in advance,
Ben
Edit: added some pops
Okay sorry to answer my own question so soon - but a quick flash of inspiration lead to:
void luaTable::prep_get(cstring name) {
lua_pushstring(L, name); // name string at -1
if(lua_isnumber(L, -1)) { // call prep_get("i") for ith element etc
int key = lua_tonumber(L, -1);
lua_pop(L, 1); // remove the name string from -1
lua_pushnumber(L, key); // push name number to -1
}
lua_gettable(L, -2);
// result is now at position -1 in stack
}
which works as desired.
#user1483596 I don't think that solution would work. lua_isnumber will only return true if the value is of type number, and you just pushed a string, so it will always return false.
Instead, try something like this:
void luaTable::prep_get(cstring name) {
int num = strtol(name, 0, 0);
if (num > 0) {
lua_pushnumber(L, num);
} else {
lua_pushstring(L, name);
}
lua_gettable(L, -2);
}
Bear in mind though that it won't handle a special case. In Lua a[1] and a["1"] are different. If you use this function, you'll always treat numbers as array indices, even if they're not.
If you want to differentiate both cases, then you could overload prep_get and take a number.
In Lua Code
Test = {}
function Test:new()
local obj = {}
setmetatable(obj, self)
self.__index = self
return obj
end
local a = Test:new()
a.ID = "abc123"
callCfunc(a)
In C Code
int callCfunc(lua_State * l)
{
void* obj = lua_topointer(l, 1); //I hope get lua's a variable
lua_pushlightuserdata(l, obj);
lua_getfield(l, 1, "ID");
std::string id = lua_tostring(l, 1); //I hoe get the value "abc123"
...
return 0;
}
But My C result is
id = null
Why? How to modify code to work fine ?
PS: I don't hope create C Test Class mapping to lua
==== update1 ====
In addition, I have added the test code to confirm correct incoming parameters.
int callCfunc(lua_State * l)
{
std::string typeName = lua_typename(l, lua_type(l, 1)); // the typeName=="table"
void* obj = lua_topointer(l, 1); //I hope get lua's a variable
lua_pushlightuserdata(l, obj);
lua_getfield(l, 1, "ID");
std::string id = lua_tostring(l, 1); //I hoe get the value "abc123"
...
return 0;
}
the result
typeName == "table"
so incoming parameter type is Correct
I found the reason
Correct c code should is ...
In C Code
int callCfunc(lua_State * l)
{
lua_getfield(l, 1, "ID");
std::string id = lua_tostring(l, -1); //-1
...
return 0;
}
Maybe this - haven't tested sorry - don't have a compiler handy
Input is the table from lua on top of the stack, so getfield(l,1, "ID") should get the field ID from the table at the top of the stack - which in this case is your input table. It then pushes the result to the top of the stack
int callCfunc(lua_State * l)
{
lua_getfield(l, 1, "ID");
std::string id = lua_tostring(l, 1); //I hoe get the value "abc123"
...
return 0;
}
In our menu system, we define menus in xml with lua chunks used for callbacks for menu component events. Currently, everytime a script callback is called, we call lua_loadstring which is quite slow. I'm trying to make it so this only happens once, when the menu is loaded.
My initial thought was to maintain a lua table per menu component and to do the following to add a new callback function to the table:
//create lua code that will assign a function to our table
std::string callback = "temp." + callbackName + " = function (" + params + ")" + luaCode + "end";
//push table onto stack
lua_rawgeti(L, LUA_REGISTRYINDEX, luaTableRef_);
//pop table from stack and set it as value of global "temp"
lua_setglobal(L, "temp");
//push new function onto stack
int error = luaL_loadstring(L, callback.c_str());
if ( error )
{
const char* errorMsg = lua_tostring(L, -1);
Dbg::Printf("error loading the script '%s' : %s\n", callbackName, errorMsg);
lua_pop(L,1);
return;
}
//call the lua code to insert the loaded function into the global temp table
if (lua_pcall(L, 0, 0, 0))
{
Dbg::Printf("luascript: error running the script '%s'\n", lua_tostring(L, -1));
lua_pop(L, 1);
}
//table now has function in it
This seems kind of dirty. Is there a better way that allows me to assign the function to the table directly from a lua chunk without having to use a temp global variable and running lua_pcall?
If you want to put the function in a table, then put the function in the table. It seems that your Lua-stack-fu is not strong; consider studying the manual a bit more closely.
Anyway, I'd say the biggest problem you have is your insistence on params. Callback functions should expect to be varadic; they take ... as their parameters. If they want to get those values, they should use locals like this:
local param1, param2 = ...;
But if you insist on allowing them to specify a list of parameters, you may do the following:
std::string luaChunk =
//The ; is here instead of a \n so that the line numbering
//won't be broken by the addition of this code.
"local " + params + " = ...; " +
luaCode;
lua_checkstack(L, 3);
lua_rawgeti(L, LUA_REGISTRYINDEX, luaTableRef_);
if(lua_isnil(L, -1))
{
//Create the table if it doesn't already exist.
lua_newtable(L);
//Put it in the registry.
lua_rawseti(L, LUA_REGISTRYINDEX, luaTableRef_);
//Get it back, since setting it popped it.
lua_rawgeti(L, LUA_REGISTRYINDEX, luaTableRef_);
}
//The table is on the stack. Now put the key on the stack.
lua_pushlstring(L, callbackName.c_str(), callbackName.size());
//Load up our function.
int error = luaL_loadbuffer(L, luaChunk.c_str(), luaChunk.size(),
callbackName.c_str());
if( error )
{
const char* errorMsg = lua_tostring(L, -1);
Dbg::Printf("error loading the script '%s' : %s\n", callbackName, errorMsg);
//Pop the function name and the table.
lua_pop(L, 2);
return;
}
//Put the function in the table.
lua_settable(L, -3);
//Remove the table from the stack.
lua_pop(L, 1);