问题描述
我真的在谷歌上搜索过这个问题,但我从来没有真正得到解决方案.
I have really Googled this question but I never really got an solution.
我想在 C 和 Lua 之间共享一个数组,为了性能我将避免从 Lua 复制数组.
I want to share an Array between C and Lua, for performance I will avoid copying Arrays to and from Lua.
所以我想将一个指向数组的指针从 C 传递给 Lua.然后从 Lua 我想直接设置/修改这个数组中的值.
So I want to pass a pointer to the Array from C to Lua. And then from Lua I want to set/modify values in this array directly.
C 代码示例
我想定义我的数组
int mydata[] = {1,2,3,4}
将其设置为全局以从 Lua 使用名称 mydata
访问它.
set it global to access it from Lua with the name mydata
.
在 Lua 中
我想改变这样的值
mydata[3] = 9
当我返回 C 语言时,mydata[3]
是 9,因为它是一个指向数组的指针.
and when I return to C, mydata[3]
is 9 because it is a pointer to the array.
这怎么可能?
推荐答案
您可以通过 userdata
向 Lua 公开任意数据.如果你给你的用户数据值一个元表,你可以为这些用户数据定义各种操作符/操作的行为.在这种情况下,我们想向 Lua 公开一个数组并定义在 array[index]
和 array[index] = value
的情况下要做什么.
You can expose arbitrary data to Lua via userdata
. If you give your userdata values a metatable, you can define the behavior for various operators/operations on those userdata. In this case, we want to expose an array to Lua and define what to do in the case of array[index]
and array[index] = value
.
我们通过创建一个足够大的用户数据缓冲区来将数组暴露给 Lua,以保存数组的地址.我们通过使用 __index
和 __newindex
方法创建元表来定义索引/分配行为.
We expose the array to Lua by creating a userdata buffer large enough to hold the address of the array. We define the indexing/assignment behavior by created a metatable with the __index
and __newindex
methods.
下面是一个完整的工作示例,它向 Lua 公开了一个静态数组.您的程序可能会有一些其他调用来将数组返回给 Lua.请注意,根本没有边界检查;如果您尝试在数组边界之外进行索引,则会崩溃.为了使其更健壮,您需要将用户数据更改为具有数组指针和数组大小的结构,以便您可以进行边界检查.
Below is a complete, working example that exposes a static array to Lua. Your program will probably have some other call for returning the array to Lua. Note, there's no boundschecking at all; if you try to index outside the array bounds, you'll crash. To make this more robust, you'd want to change the userdata to a structure which has the array pointer and the array size, so you can do boundschecking.
#include "lauxlib.h"
// metatable method for handling "array[index]"
static int array_index (lua_State* L) {
int** parray = luaL_checkudata(L, 1, "array");
int index = luaL_checkint(L, 2);
lua_pushnumber(L, (*parray)[index-1]);
return 1;
}
// metatable method for handle "array[index] = value"
static int array_newindex (lua_State* L) {
int** parray = luaL_checkudata(L, 1, "array");
int index = luaL_checkint(L, 2);
int value = luaL_checkint(L, 3);
(*parray)[index-1] = value;
return 0;
}
// create a metatable for our array type
static void create_array_type(lua_State* L) {
static const struct luaL_reg array[] = {
{ "__index", array_index },
{ "__newindex", array_newindex },
NULL, NULL
};
luaL_newmetatable(L, "array");
luaL_openlib(L, NULL, array, 0);
}
// expose an array to lua, by storing it in a userdata with the array metatable
static int expose_array(lua_State* L, int array[]) {
int** parray = lua_newuserdata(L, sizeof(int**));
*parray = array;
luaL_getmetatable(L, "array");
lua_setmetatable(L, -2);
return 1;
}
// test data
int mydata[] = { 1, 2, 3, 4 };
// test routine which exposes our test array to Lua
static int getarray (lua_State* L) {
return expose_array( L, mydata );
}
int __declspec(dllexport) __cdecl luaopen_array (lua_State* L) {
create_array_type(L);
// make our test routine available to Lua
lua_register(L, "array", getarray);
return 0;
}
用法:
require 'array'
foo = array()
print(foo) -- userdata
-- initial values set in C
print(foo[1])
print(foo[2])
print(foo[3])
print(foo[4])
-- change some values
foo[1] = 2112
foo[2] = 5150
foo[4] = 777
-- see changes
print(foo[1])
print(foo[2])
print(foo[3])
print(foo[4])
这篇关于在 lua 和 C 之间共享数组的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!
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