lua userdata 就是用户自定义类型的数据
直接上例子
wss@localhost:~/lua/userdata/userdata2$ ls
array.so arr_test.lua lib.c log.lua
wss@localhost:~/lua/userdata/userdata2$ vim lib.c
#include <stdio.h>
#include <string.h>
#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>
typedef struct NumArray
{
int size;
double values[1]; /* variable part */
}NumArray;
static int newarray (lua_State *L)
{
int n = luaL_checkint(L, 1); //检查所给参数是否是一个数字，如果是返回该数字，否则报错
size_t nbytes = sizeof(NumArray) + (n - 1)*sizeof(double);
NumArray *a = (NumArray *)lua_newuserdata(L, nbytes);
a->size = n;
return 1; /* new userdatum is already on the stack */
}
static int setarray (lua_State *L)
{
NumArray *a = (NumArray *)lua_touserdata(L, 1); //返回userdata的地址
int index = luaL_checkint(L, 2);
double value = luaL_checknumber(L, 3);
luaL_argcheck(L, a != NULL, 1, "'array' expected");
//检查a != NULL 是否等于true，如果不是，抛出错误，并给出指定的错误信息
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 luaL_Reg arraylib [] =
{
{"new", newarray},
{"set", setarray},
{"get", getarray},
{"size", getsize},
{NULL, NULL}
};
int luaopen_array (lua_State *L)
{
const char* libName = "array";
luaL_register(L,libName,arraylib);
return 1;
}
wss@localhost:~/lua/userdata/userdata2$ vim arr_test.lua
require "array"
local log = require "log"
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
log.print_r(array.get(a, 10))
wss@localhost:~/lua/userdata/userdata2$ gcc -fpic -shared -o array.so lib.c
wss@localhost:~/lua/userdata/userdata2$ ls
array.so arr_test.lua lib.c log.lua
wss@localhost:~/lua/userdata/userdata2$ lua arr_test.lua
userdata: 0x8aeb784
1000
0.1
log.lua是用来调试，打印信息的，在每个.lua文件开始添加一行local log = require "luci.log"，在需要打印的函数中调用log.print()或者log.print_r()， 最后在/tmp/luci.output文件中查看添加的打印内容。
如：
wss@localhost:~/lua/userdata/userdata2$ echo "" > /tmp/luci.output
wss@localhost:~/lua/userdata/userdata2$ cat /tmp/luci.output
wss@localhost:~/lua/userdata/userdata2$ lua arr_test.lua
userdata: 0x82256ac
1000
0.1
wss@localhost:~/lua/userdata/userdata2$ cat /tmp/luci.output
[11:20:43]: 0.1
log.print打印一个普通变量
log.print_r打印table