lua 自定义lib

struct NumArray
{
    size_t size;
    double values[1];
};

static int newarray(lua_State*L)
{
    int n = luaL_checkint(L,1);
    size_t nbytes = sizeof(NumArray) + (n-1)*sizeof(double);
    NumArray*a = (NumArray*)lua_newuserdata(L,nbytes);
    a->size = n;
    return 1;
}

static int setarray(lua_State *L)
{
    NumArray*a = (NumArray*)lua_touserdata(L,1);
    int index = luaL_checkint(L,2);
    double value = luaL_checknumber(L,3);
    luaL_argcheck(L,a!= NULL,1,"array expected");
    luaL_argcheck(L,1<= index && index <= a->size ,2,"index out of range");
    a->values[index - 1] = value;
    return 0;
}

static int getarray (lua_State *L)
{
    NumArray *a = (NumArray *)lua_touserdata(L, 1);
    int index = luaL_checkint(L, 2);
    luaL_argcheck(L, a != NULL, 1, "'array' expected");
    luaL_argcheck(L, 1 <= index && index <= a->size, 2,
                  "index out of range");
    lua_pushnumber(L, a->values[index-1]);
    return 1;
}

static int getsize (lua_State *L)
{
    NumArray *a = (NumArray *)lua_touserdata(L, 1);
    luaL_argcheck(L, a != NULL, 1, "`array' expected");
    lua_pushnumber(L, a->size);
    return 1;
}

static const struct luaL_Reg arraylib [] =
 {

    {"new", newarray},
    {"set", setarray},
    {"get", getarray},
    {"size", getsize},
    {NULL, NULL}
};

int luaopen_array (lua_State *L)
 {
    luaL_newlib(L,arraylib);
    lua_setglobal(L,"array");
    return 1;
}

a = array.new(1000)
print(a)                 --> userdata: 0x8064d48

print(array.size(a))     --> 1000
for i=1,1000 do
    array.set(a, i, 1/i)
end

print(array.get(a, 10))  --> 0.1