Lua sample code analysis
What is a meta table
a meta table has a __name attr whose value is name of metatable
a meta table is stored in LUA_REGISTRYINDEX whose key is its name
Code analysis
Appl
DUMP_STACK(L);
/*{ "foo", "C:\\test\\codes\\mylualib\\test\\../build/v100+x64+Debug/foo_vc100_64.
dll" }*/
//1. 创建元表，并将该元表指定给newArray函数新创建的userdata。在Lua中userdata也是以table的身份表现的。
//这样在调用对象函数时，可以通过验证其metatable的名称来确定参数userdata是否合法。
luaL_newmetatable(L,"myarray");
lua_pushvalue(L,-1);
/*
top=4
4/-1: type=table{__name='myarray', }
3/-2: type=table{__name='myarray', } -->name it mt
2/-3: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-4: type=string'foo'
*/
//2. 为了实现面对对象的调用方式，需要将元表的__index字段指向自身，同时再将arraylib_m数组中的函数注册到
//元表中，之后基于这些注册函数的调用就可以以面向对象的形式调用了。
//lua_setfield在执行后会将栈顶的table弹出。
lua_setfield(L, -2, "__index"); // mt.__index = mt
/*
top=3
3/-1: type=table{__index={__index={__index={__index={__index=, __name=, }, __name='myarray', }, __name='myarray', }, __name='myarray', }, __name='myarray', }
2/-2: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-3: type=string'foo'*/
//将这些成员函数注册给元表，以保证Lua在寻找方法时可以定位。NULL参数表示将用栈顶的table代替第二个参数。
luaL_register(L, NULL, arraylib_m);
//这里只注册的工厂方法。
luaL_register(L,"testuserdata",arraylib_f);
DUMP_STACK(L);
/*{ "foo", "C:\\test\\codes\\mylualib\\test\\../build/v100+x64+Debug/foo_vc100_64.
dll", <1>{
__gc = <function 1>,
__index = <table 1>,
__name = "myarray",
__tostring = <function 2>,
get = <function 3>,
set = <function 4>,
size = <function 5>
}, {
new = <function 6>
} }
*/
luaL_register(L,"testuserdatafm",arraylib_f_and_m);
DUMP_STACK(L);
/*{ "foo", "C:\\test\\codes\\mylualib\\test\\../build/v100+x64+Debug/foo_vc100_64.
dll", <1>{
__gc = <function 1>,
__index = <table 1>,
__name = "myarray",
__tostring = <function 2>,
get = <function 3>,
set = <function 4>,
size = <function 5>
}, {
new = <function 6>
}, {
get = <function 3>,
new = <function 6>,
set = <function 4>,
size = <function 5>,
tostring = <function 2>
} }*/
luaopen_packet(L);
/*{ "foo", "C:\\test\\codes\\mylualib\\test\\../build/v100+x64+Debug/foo_vc100_64.
dll", <1>{
__gc = <function 1>,
__index = <table 1>,
__name = "myarray",
__tostring = <function 2>,
get = <function 3>,
set = <function 4>,
size = <function 5>
}, {
new = <function 6>
}, {
get = <function 3>,
new = <function 6>,
set = <function 4>,
size = <function 5>,
tostring = <function 2>
}, {
creatPacket = <function 7>
} }
*/
=========
luaL_newmetatable
LUALIB_API int luaL_newmetatable (lua_State *L, const char *tname) {
if (luaL_getmetatable(L, tname) != LUA_TNIL) /* name already in use? */ // top=1
return 0; /* leave previous value on top, but return 0 */
/*top=3
3/-1: type=nil
2/-2: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-3: type=string'foo'
*/
lua_pop(L, 1); // =0
lua_createtable(L, 0, 2); /* create metatable */ // =1
/*top=3
3/-1: type=table{}
2/-2: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-3: type=string'foo'*/
lua_pushstring(L, tname); // =2
/*top=4
4/-1: type=string'myarray'
3/-2: type=table{}
2/-3: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-4: type=string'foo'*/
lua_setfield(L, -2, "__name"); /* metatable.__name = tname */ // =1
/*top=3
3/-1: type=table{'myarray', }
2/-2: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-3: type=string'foo'*/
lua_pushvalue(L, -1); // =2
/*top=4
4/-1: type=table{__name='myarray', }
3/-2: type=table{__name='myarray', }
2/-3: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-4: type=string'foo'*/
lua_setfield(L, LUA_REGISTRYINDEX, tname); /* registry.name = metatable */
/*top=3
3/-1: type=table{__name='myarray', }
2/-2: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-3: type=string'foo'*/
return 1;
}
EnumTableItem
void EnumTableItem(lua_State *L, int index, int nDepth)
{
/*top=4
4/-1: type=table{C:000007FEEF9610EB, }
3/-2: type=table{'myarray', {, , , , , , , }, C:000007FEEF961131, C:000007FEEF9611A9, C:000007FEEF961163, C:000007FEEF961113, C:000007FEEF96103C, }
2/-3: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-4: type=string'foo'
*/
int top = lua_gettop(L);
lua_pushvalue(L, index); // copy the variable to stack top // +1
int it = lua_gettop(L);
myprintf("{");
lua_pushnil(L);
/*{----------8, NA, 0
top=6
6/-1: type=nil
5/-2: type=table{C:000007FEEF9610EB, }
4/-3: type=table{C:000007FEEF9610EB, }
3/-4: type=table{'myarray', {, , , , , , , }, C:000007FEEF961131, C:000007FEEF9611A9, C:000007FEEF961163, C:000007FEEF961113, C:000007FEEF96103C, }
2/-5: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-6: type=string'foo'
*/
// 2
while (lua_next(L, it)) // If there is data, then top++, else top--
{
/*top=7
7/-1: type=functionC:000007FEEF9610EB
6/-2: type=string'new'
5/-3: type=table{C:000007FEEF9610EB, }
4/-4: type=table{C:000007FEEF9610EB, }
3/-5: type=table{'myarray', {, , , , , , , }, C:000007FEEF961131, C:000007FEEF9611A9, C:000007FEEF961163, C:000007FEEF961113, C:000007FEEF96103C, }
2/-6: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-7: type=string'foo'
*/
DumpItemEx(L, -1, nDepth+1);
myprintf(", ");
lua_pop(L, 1);
} // 1
myprintf("}");
lua_pop(L, 1); // 0
int top2 = lua_gettop(L);
assert(top==top2);
}
#define luaL_register(L,n,l) (luaL_openlib(L,(n),(l),0))
luaL_openlib
LUALIB_API void luaL_openlib (lua_State *L, const char *libname,
const luaL_Reg *l, int nup) {
/*top=3
3/-1: type=table{__index={__index={__index={__index={__index=, __name=, }, __name='myarray', }, __name='myarray', }, __name='myarray', }, __name='myarray', }
2/-2: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-3: type=string'foo'
*/
luaL_checkversion(L);
if (libname) {
luaL_pushmodule(L, libname, libsize(l)); /* get/create library table */
lua_insert(L, -(nup + 1)); /* move library table to below upvalues */
}
if (l)
luaL_setfuncs(L, l, nup);
else
lua_pop(L, nup); /* remove upvalues */
}
luaL_setfuncs
// This function fills the functions to a table
// the key function is
// lua_pushcclosure, lua_setfield
//
LUALIB_API void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup) {
/*top=3
3/-1: type=table{__index={__index={__index={__index={__index=, __name=, }, __name='myarray', }, __name='myarray', }, __name='myarray', }, __name='myarray', }
2/-2: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-3: type=string'foo'
*/
luaL_checkstack(L, nup, "too many upvalues");
for (; l->name != NULL; l++) { /* fill the table with given functions */
int i;
for (i = 0; i < nup; i++) /* copy upvalues to the top */
lua_pushvalue(L, -nup);
lua_pushcclosure(L, l->func, nup); /* closure with those upvalues */
/*top=4
4/-1: type=functionC:000007FED9A21131
3/-2: type=table{__index={__index={__index={__index={__index=, __name=, }, __name='myarray', }, __name='myarray', }, __name='myarray', }, __name='myarray', }
2/-3: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-4: type=string'foo'
*/
lua_setfield(L, -(nup + 2), l->name);
/*top=3
3/-1: type=table{__index={__index={__index={__index={__index=, __name=, set=, }, __name='myarray', set=C:000007FED9A21131, }, __name='myarray', set=C:000007FED9A21131, }, __name='myarray', set=C:000007FED9A21131, }, __name='myarray', set=C:000007FED9A21131, }
2/-2: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-3: type=string'foo'
*/
}
lua_pop(L, nup); /* remove upvalues */
/*top=3
3/-1: type=table{__index={__index={__index={__index={__index=, set=, __gc=, __tostring=, get=, size=, __name=, }, set=C:000007FED9A21131, __gc=C:000007FED9A21163, __tostring=C:000007FED9A211A9, get=C:000007FED9A2103C, size=C:000007FED9A21113, __name='myarray', }, set=C:000007FED9A21131, __gc=C:000007FED9A21163, __tostring=C:000007FED9A211A9, get=C:000007FED9A2103C, size=C:000007FED9A21113, __name='myarray', }, set=C:000007FED9A21131, __gc=C:000007FED9A21163, __tostring=C:000007FED9A211A9, get=C:000007FED9A2103C, size=C:000007FED9A21113, __name='myarray', }, set=C:000007FED9A21131, __gc=C:000007FED9A21163, __tostring=C:000007FED9A211A9, get=C:000007FED9A2103C, size=C:000007FED9A21113, __name='myarray', }
2/-2: type=string'C:\test\codes\mylualib\test\../build/v100+x64+Debug/foo_vc100_64.dll'
1/-3: type=string'foo'
*/
}
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