lua笔记之userdata

#include "lua.h"
#include "lauxlib.h"
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>

typedef struct NumArray
{
    int size;
    double values[1];
}NumArray;

static int 
lnew(lua_State *L)
{
    int arr_size = luaL_checkint(L, 1);
    if (arr_size <= 0)
    {
        assert(NULL);
    }

    size_t nbytes = sizeof(NumArray) + (arr_size - 1) * sizeof(double);
    NumArray *na = (NumArray *)lua_newuserdata(L, nbytes);
    na->size = arr_size;

    return 1;
}

static int 
lset(lua_State *L)
{
    NumArray *na = (NumArray *)lua_touserdata(L, 1);
    int idx = luaL_checkint(L, 2);
    double value = luaL_checknumber(L, 3);
    printf("idx %d, value %f\n", idx, value);
    luaL_argcheck(L, na != NULL, 1, "array expected");
    luaL_argcheck(L, 1 <= idx && idx <= na->size , 2, "index out of range");

    na->values[idx - 1] = value;

    return 0;
}

static int 
lget(lua_State *L)
{
    NumArray *na = (NumArray *)lua_touserdata(L, 1);
    int idx = luaL_checkinteger(L, 2);

    luaL_argcheck(L, na != NULL, 1, "array expected");
    luaL_argcheck(L, 1 <= idx && idx <= na->size, 2, "index out of range");

    lua_pushnumber(L, na->values[idx - 1]);

    return 1;
}    
    
static int
lfind(lua_State *L)
{
    NumArray *na = (NumArray *)lua_touserdata(L, 1);
    assert(na != NULL);
    double elem = luaL_checknumber(L, 2);

    int idx;
    for (idx = 0; idx < na->size; idx++)
    {
        if (na->values[idx] == elem)
        {
            lua_pushnumber(L, idx + 1);
            return 1;
        }
    }

    lua_pushnumber(L, -1);
    return 1;
}

int
luaopen_newarray(lua_State *L)
{
    luaL_checkversion(L);
    luaL_Reg l[] = 
    {
        {"new", lnew},
        {"set", lset},
        {"get", lget},
        {"find", lfind},
        {NULL, NULL},
    };

    luaL_newlib(L, l);

    return 1;
}

local newarray = require "newarray"

print(newarray)
local na = newarray.new(1000)

newarray.set(na, 1, 100)

local value = newarray.find(na, 100)

if value ~= -1 then
    print("value is ", value)
else
    print("not exists")
end