使用成员和方法进行绑定
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使用成员和方法进行绑定 |
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这是一个使用index和newindex事件访问C结构体成员的 Lua 绑定示例。
newindex事件处理函数在它的上值中有一个查找表，其中包含可以设置的所有成员的列表。对于每个可以设置的成员，查找表包含该成员在结构体中的偏移量，以及一个指向用于设置该类型成员的胶水函数的指针。我们只需要为每种类型的成员编写一个胶水函数：double、int、char*。这样，我们就可以对该结构体中的所有int，或暴露给 Lua 的任何其他结构体，使用相同的设置int胶水函数。
index事件处理函数类似。它有一个用于所有可以获取的成员的查找表，但它还有一个用于所有方法函数的第二个查找表。
// CStructToLua.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
extern "C" {
#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"
}
/*
==============================================================================
Example Lua bindings with members and methods
==============================================================================
*/
static int get_int (lua_State *L, void *v)
{
lua_pushnumber(L, *(int*)v);
return 1;
}
static int set_int (lua_State *L, void *v)
{
*(int*)v = luaL_checkint(L, 3);
return 0;
}
static int get_number (lua_State *L, void *v)
{
lua_pushnumber(L, *(lua_Number*)v);
return 1;
}
static int set_number (lua_State *L, void *v)
{
*(lua_Number*)v = luaL_checknumber(L, 3);
return 0;
}
static int get_string (lua_State *L, void *v)
{
lua_pushstring(L, (char*)v );
return 1;
}
typedef int (*Xet_func) (lua_State *L, void *v);
/* member info for get and set handlers */
typedef const struct{
const char *name; /* member name */
Xet_func func; /* get or set function for type of member */
size_t offset; /* offset of member within your_t */
} Xet_reg_pre;
typedef Xet_reg_pre * Xet_reg;
static void Xet_add (lua_State *L, Xet_reg l)
{
for (; l->name; l++) {
lua_pushstring(L, l->name);
lua_pushlightuserdata(L, (void*)l);
lua_settable(L, -3);
}
}
static int Xet_call (lua_State *L)
{
/* for get: stack has userdata, index, lightuserdata */
/* for set: stack has userdata, index, value, lightuserdata */
Xet_reg m = (Xet_reg)lua_touserdata(L, -1); /* member info */
lua_pop(L, 1); /* drop lightuserdata */
luaL_checktype(L, 1, LUA_TUSERDATA);
return m->func(L, (void *)((char *)lua_touserdata(L, 1) + m->offset));
}
static int index_handler (lua_State *L)
{
/* stack has userdata, index */
lua_pushvalue(L, 2); /* dup index */
lua_rawget(L, lua_upvalueindex(1)); /* lookup member by name */
if (!lua_islightuserdata(L, -1)) {
lua_pop(L, 1); /* drop value */
lua_pushvalue(L, 2); /* dup index */
lua_gettable(L, lua_upvalueindex(2)); /* else try methods */
if (lua_isnil(L, -1)) /* invalid member */
luaL_error(L, "cannot get member '%s'", lua_tostring(L, 2));
return 1;
}
return Xet_call(L); /* call get function */
}
static int newindex_handler (lua_State *L)
{
/* stack has userdata, index, value */
lua_pushvalue(L, 2); /* dup index */
lua_rawget(L, lua_upvalueindex(1)); /* lookup member by name */
if (!lua_islightuserdata(L, -1)) /* invalid member */
luaL_error(L, "cannot set member '%s'", lua_tostring(L, 2));
return Xet_call(L); /* call set function */
}
/*
==============================================================================
Your structure and custom methods
==============================================================================
*/
#define YOUR_T "YourClass"
typedef struct {
int id;
char name[16];
int age;
double x,y;
} your_t;
static your_t *check_your_t (lua_State *L, int index)
{
your_t *yd;
luaL_checktype(L, index, LUA_TUSERDATA);
yd = (your_t *)luaL_checkudata(L, index, YOUR_T);
if (yd == NULL) luaL_typerror(L, index, YOUR_T);
return yd;
}
static your_t *push_your_t (lua_State *L)
{
your_t *yd = (your_t*)lua_newuserdata(L, sizeof(your_t));
luaL_getmetatable(L, YOUR_T);
lua_setmetatable(L, -2);
return yd;
}
static int id_counter;
static int your_create (lua_State *L)
{
your_t *yd;
unsigned int name_len;
const char *name = luaL_checklstring(L, 1, &name_len);
if( name_len > 15 ) luaL_error(L, "name too long"); /* die */
yd = push_your_t(L);
strcpy( yd->name, name );
yd->age = luaL_checkint(L, 2);
yd->x = luaL_checknumber(L, 3);
yd->y = luaL_checknumber(L, 4);
yd->id = ++id_counter;
return 1;
}
static int your_destroy (lua_State *L)
{
your_t *yd = (your_t*)lua_touserdata(L,1);
printf("Goodbye %s:%d at (%lf,%lf)\n", yd->name, yd->id, yd->x, yd->y);
return 0;
}
static int your_position (lua_State *L)
{
your_t *yd = check_your_t(L, 1);
double x = yd->x;
double y = yd->y;
if( lua_gettop(L) > 1 ) {
yd->x = luaL_checknumber(L, 2);
yd->y = luaL_checknumber(L, 3);
}
lua_pushnumber(L,x);
lua_pushnumber(L,y);
return 2;
}
static int test (lua_State *L)
{
int n = luaL_checknumber(L, 1);
lua_pushnumber(L, 66);
lua_pushnumber(L, 67);
lua_pushnumber(L, 68);
return n;
}
static const luaL_reg your_meta_methods[] = {
{"__gc", your_destroy },
{0,0}
};
static const luaL_reg your_methods[] = {
{"create", your_create},
{"position", your_position},
{"test", test},
{0,0}
};
static const Xet_reg_pre your_getters[] = {
{"id", get_int, offsetof(your_t,id) },
{"name", get_string, offsetof(your_t,name) },
{"age", get_int, offsetof(your_t,age) },
{"x", get_number, offsetof(your_t,x) },
{"y", get_number, offsetof(your_t,y) },
{0,0}
};
static const Xet_reg_pre your_setters[] = {
{"age", set_int, offsetof(your_t,age) },
{"x", set_number, offsetof(your_t,x) },
{"y", set_number, offsetof(your_t,y) },
{0,0}
};
int your_register (lua_State *L)
{
int metatable, methods;
/* create methods table, & add it to the table of globals */
luaL_openlib(L, YOUR_T, your_methods, 0);
methods = lua_gettop(L);
/* create metatable for your_t, & add it to the registry */
luaL_newmetatable(L, YOUR_T);
luaL_openlib(L, 0, your_meta_methods, 0); /* fill metatable */
metatable = lua_gettop(L);
lua_pushliteral(L, "__metatable");
lua_pushvalue(L, methods); /* dup methods table*/
lua_rawset(L, metatable); /* hide metatable:
metatable.__metatable = methods */
lua_pushliteral(L, "__index");
lua_pushvalue(L, metatable); /* upvalue index 1 */
Xet_add(L, your_getters); /* fill metatable with getters */
lua_pushvalue(L, methods); /* upvalue index 2 */
lua_pushcclosure(L, index_handler, 2);
lua_rawset(L, metatable); /* metatable.__index = index_handler */
lua_pushliteral(L, "__newindex");
lua_newtable(L); /* table for members you can set */
Xet_add(L, your_setters); /* fill with setters */
lua_pushcclosure(L, newindex_handler, 1);
lua_rawset(L, metatable); /* metatable.__newindex = newindex_handler */
lua_pop(L, 1); /* drop metatable */
return 1; /* return methods on the stack */
}
int main(int argc, char *argv[])
{
lua_State *L = lua_open();
luaopen_base(L);
luaopen_table(L);
//luaopen_io(L);
luaopen_string(L);
luaopen_math(L);
luaopen_debug(L);
your_register(L);
luaL_dofile(L, "test.lua");
//if(argc>1) lua_dofile(L, argv[1]);
lua_close(L);
return 0;
}
此代码可以按如下方式编译用于 Lua 5.0
gcc member.c -L/usr/local/lib/ -llua -llualib
print('= YourClass =',YourClass) for n,v in YourClass do print(n,v) end b = YourClass.create('bill', 99, 34,65) f = YourClass.create('fish', 44, 16.7,19.25) local member_names = {'id','name','age','x','y'} function dump(ud) for _,n in pairs(member_names) do print(n, ud[n]) end end print'*** b ***' dump(b) print'*** f ***' dump(f) print('b.name =', b.name, 'pos = ', b.x, b.y) b.age = 88 b.x = 40 b.y = 50 print'*** modified b ***' dump(b) debug.debug()
$ ./a member.lua = YourClass = table: 0xa044f00 test function: 0xa044f60 create function: 0xa044f28 position function: 0xa045240 *** b *** id 1 name bill age 99 x 34 y 65 *** f *** id 2 name fish age 44 x 16.7 y 19.25 b.name = bill pos = 34 65 *** modified b *** id 1 name bill age 88 x 40 y 50 lua_debug> print(b.age, b:position()) 88 40 50 lua_debug> b.age = 99 lua_debug> b.name = 'rat' [string "b.name = 'rat'..."]:1: cannot set member 'name' lua_debug> print(b.cow) [string "print(b.cow)..."]:1: cannot get member 'cow' lua_debug> b.fish = 9 [string "b.fish = 9..."]:1: cannot set member 'fish' lua_debug> dump(b) id 1 name bill age 99 x 40 y 50 lua_debug> cont Goodbye fish:2 at (16.700000,19.250000) Goodbye bill:1 at (40.000000,50.000000)