Lua as a method of reading configuration files

struct PICTURECFG

{

String name;

float rotation;

};

1, global configuration

--Picture0-cfg.lua

Name = "Dragon.png"

rotation= 180

Global configuration Read

Voidloadpicturecfg (vector<picturecfg>& Rstpicturecfgvec)

{

Picturecfg stcfg;

lua_state* L = Lual_newstate (); Create a new independent state machine

Lual_dofile (L, "Picture0-cfg.lua");

Lua_getglobal (L, "name"); Pressing the value in the global variable name into the stack is equivalent to Lua_getfield (L,lua_globalsindex, "name")

printf ("%s\n", Lua_typename (L, Lua_type (L,-1));

ASSERT (Lua_isstring (L,-1) = = 1); Returns 1 when the value of the given index is a string or a number (the number is always converted to a string), or 0

Stcfg.name = lua_tostring (L,-1); Converts the Lua value at the given index to a C string, noting that the function of the series does not eject the value from the stack

Lua_getglobal (L, "rotation"); //

ASSERT (Lua_isnumber (L,-1) = = 1);

Stcfg.rotation = (float) lua_tonumber (L,-1); Converts the Lua value at a given index to a C type such as Lua_number (see Lua_number). This Lua value must be a number or a string that can be converted to a number (see §2.2.1); otherwise, Lua_tonumber returns 0. typedef double Lua_number;

Rstpicturecfgvec.push_back (STCFG);

Lua_close (L);

}

2, one-dimensional table configuration read

--Picture1-cfg.lua

CFG = {name= "Dragon.png", rotation=180}

Reading of a one-dimensional table

Voidloadpicturecfg (vector<picturecfg>& Rstpicturecfgvec)

{

lua_state* L = Lual_newstate ();

Lual_dofile (L, "Picture1-cfg.lua");

Get the table

Lua_getglobal (L, "cfg"); The global variable cfg pressure stack, cfg is table type, one-dimensional table

ASSERT (Lua_istable (L,-1) = = 1);

Picturecfg stcfg;

Push the key to stack for getting the value

Lua_pushstring (L, "name"); //

Now the ' table ' in The-2 and key (-1)

Lua_gettable (L,-2);

/*

void Lua_gettable (lua_state *l, int index);

The t[k] value is pressed into the stack, where T is the value that the valid index index points to, and K is the stack top value.

This function pops up the key on the stack (placing the result on the stack in the same position).

*/

ASSERT (Lua_isstring (L,-1));

Stcfg.name = lua_tostring (L,-1);

Lua_pop (L, 1);

Push the key to stack for getting the value

Lua_pushstring (L, "rotation");

Now the ' table ' in The-2 and key (-1)

Lua_gettable (L,-2);

ASSERT (Lua_isnumber (L,-1));

Stcfg.rotation = Lua_tonumber (L,-1);

Rstpicturecfgvec.push_back (STCFG);

/* Empty Stack * *

Lua_pop (L, 2);

Lua_close (L);

}

The typical one-dimensional table traversal method is this:

int t_idx = Lua_gettop (L); Fetch Table Index value

Lua_pushnil (L); First key

while (Lua_next (L, T_idx)!= 0)

{

Now the top of the stack (-1) is the value,-2 position is the corresponding key

Here you can determine what the key is and do a variety of processing of value

printf ("%s-%s\n", Lua_typename (L, Lua_type (L,-2)), Lua_typename (L, Lua_type (L,-1));

Lua_pop (L, 1); Remove ' value '; Keep ' key ' for next iteration

}

2, two-dimensional table configuration read

--Picture2-cfg.lua

CFG = {

{name= "Dragon.png", rotation=180},

{name= "Dragon.png", rotation=0}

}

Reading of two-dimensional tables

Voidloadpicturecfg (vector<picturecfg>& Rstpicturecfgvec)

{

lua_state* L = Lual_newstate ();

Lual_dofile (L, "Picture2-cfg.lua");

Get the table

Lua_getglobal (L, "cfg"); The global variable cfg pressure stack, cfg is table type, and is a two-dimensional table

ASSERT (Lua_istable (L,-1) = = 1);

/*

int Lua_type (lua_state *l, int index);

Returns the type of the value at the given index and returns Lua_tnone when the index is invalid (that is, an index pointing to an empty position on the stack). The type returned by Lua_type is some of the constants defined in Lua.h: Lua_tnil, Lua_tnumber, Lua_tboolean, lua_tstring, lua_ttable, Lua_tfunction, lua_t USERDATA, Lua_tthread, Lua_tlightuserdata.

const char *lua_typename (lua_state*l, int tp);

Returns the name of the type that the TP represents, which must be one of the values that Lua_type might return.

*/

Lua_pushnil (L); /* First key//////////////////////Nil

while (Lua_next (L,-2)!= 0)//index-2 is the table

{

/*

int Lua_next (lua_state *l, int index);

POPs a key from the stack and then pushes the next Key-value (health value) in the table specified by index onto the stack

If there are no more elements in the table, then Lua_next will return 0 (nothing is pressed onto the stack).

*/

/* ' key ' (at index-2) and ' value ' (at index-1) * *

Picturecfg rstcfg;

Push the key to stack for getting the value

Lua_pushstring (L, "name"); //

/*

void Lua_pushstring (lua_state *l, const char *s);

Put the pointer s to the end of the string of 0 to press the stack. Lua makes a memory copy of the string (or a duplicate copy), so the memory at S can be released or reused for other purposes after the function returns. The string cannot contain 0 characters; The first encounter of the 0-character specifier is considered to be the end of the string.

*/

Now the ' table ' in The-2 and key (-1)

Lua_gettable (L,-2);

/*

void Lua_gettable (lua_state *l, int index);

The t[k] value is pressed into the stack, where T is the value that the valid index index points to, and K is the stack top value.

This function pops up the key on the stack (placing the result on the stack in the same position).

*/

ASSERT (Lua_isstring (L,-1)); The value of name of the first child table is now on the top of the stack

Rstcfg.name = lua_tostring (L,-1);

Lua_pop (L, 1);

/*

void Lua_pop (lua_state *l, int n);

POPs an n element from the stack.

*/

Push the key to stack for getting the value

Lua_pushstring (L, "rotation");

Now the ' table ' in The-2 and key (-1)

Lua_gettable (L,-2);

ASSERT (Lua_isnumber (L,-1));

Rstcfg.rotation = Lua_tonumber (L,-1);

Rstpicturecfgvec.push_back (RSTCFG);

/* Removes the key we pushed and the ' value ' of the global table; Keeps ' key ' for next iteration * *

Lua_pop (L, 2);

}

Lua_close (L);

}

Another way to traverse a two-dimensional table is as follows:

T_idx = Lua_gettop (L);

Lua_pushnil (L);

while (Lua_next (L, T_idx))

{

It_idx = Lua_gettop (L); Inner table

Lua_pushnil (L);

while (Lua_next (L, It_idx))

{

printf ("%s\n", Lua_tostring (l,-1)); Here is value, but value is not necessarily a string type

Lua_pop (L, 1);

}

Lua_pop (L, 1);

}