Iterating a multidimensional Lua table in C
I have a problem iterating over a multidimensional Lua table in C.
Let the Lua table be ie:
local MyLuaTable = {
{0x04, 0x0001, 0x0001, 0x84, 0x000000},
{0x04, 0x0001, 0x0001, 0x84, 0x000010}
}
I tried to extend the sample C code:
/* table is in the stack at index 't' */
lua_pushnil(L); /* first key */
while (lua_next(L, t) != 0) {
/* uses 'key' (at index -2) and 'value' (at index -1) */
printf("%s - %s\n",
lua_typename(L, lua_type(L, -2)),
lua_typename(L, lua_type(L, -1)));
/* removes 'value'; keeps 'key' for next iteration */
lua_pop(L, 1);
}
second dimension:
/* table is in the stack at index 't' */
lua_pushnil(L); /* first key */ /* Iterating the first dimension */
while (lua_next(L, t) != 0)
{
/* uses 'key' (at index -2) and 'value' (at index -1) */
printf("%s - %s\n",
lua_typename(L, lua_type(L, -2)),
lua_typename(L, lua_type(L, -1)));
if(lua_istable(L, -1))
{
lua_pushnil(L); /* first key */ /* Iterating the second dimension */
while (lua_next(L, -2) != 0) /* table is in the stack at index -2 */
{
printf("%s - %s\n",
lua_typename(L, lua_type(L, -2)),
lua_typename(L, lua_type(L, -1)));
}
/* removes 'value'; keeps 'key' for next iteration */
lua_pop(L, 1);
}
/* removes 'value'; keeps 'key' for next iteration */
lua_pop(L, 1);
}
Output:
" number - table " (from the first dimension)
" number - number " (from the second dimension)
" number - thread " (from the second dimension)
Subsequently my code crashes into "while (lua_next (L, -2)! = 0)"
Does anyone have an idea how to iterate over a two dimensional Lua table correctly?
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lua_pop(L, 1)
from the second dimension is outside of your iteration!
while (lua_next(L, -2) != 0) /* table is in the stack at index -2 */
{
printf("%s - %s\n",
lua_typename(L, lua_type(L, -2)),
lua_typename(L, lua_type(L, -1)));
}
/* removes 'value'; keeps 'key' for next iteration */
lua_pop(L, 1);
You need to put it inside a while loop to make it work to remove the value that is lua_next()
implicitly pushed onto the stack in your while state.
while (lua_next(L, -2) != 0) /* table is in the stack at index -2 */
{
printf("%s - %s\n",
lua_typename(L, lua_type(L, -2)),
lua_typename(L, lua_type(L, -1)));
/* removes 'value'; keeps 'key' for next iteration */
lua_pop(L, 1);
}
Thus, it should work as expected.
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