是否有内置例程将lightuserdata转换为int? [英] Is there a built in routine to convert lightuserdata to int?

问题描述

Lightuserdata与userdata不同，该怎么办?我的意思是lua中的lightuserdata操作.看来我无法将其转换为任何其他数据类型.

Lightuserdata is different from userdata so what can I do with it? I mean the operations of lightuserdata in lua. Looks like I cannot convert it to any other data type.

我的一个案例:

我的 C 库向 Lua 返回了一个名为c_pointer"的 C 指针，AKA lightuserdata，然后我想要:

My C library returns a C pointer named 'c_pointer', AKA lightuserdata to Lua, and then I want:

my_pointer = c_pointer +4

my_pointer = c_pointer +4

，然后将"my_pointer"传递回C库.由于我无法对"c_pointer"执行任何操作，因此表达式"c_pointer + 4"无效.

and then pass 'my_pointer' back to C library. Since I cannot do anything with 'c_pointer', so the expression 'c_pointer + 4' is invalid.

我想知道对此有一些切实可行的解决方案吗?

I am wondering are there some practical solutions to this?

推荐答案

Lightuserdata由C库创建.它们只是C指针.

Lightuserdata are created by C libraries. They are simply C pointers.

例如，您可以使用它们来引用使用 malloc 分配的数据，或在模块中静态分配的数据.您的C库可以使用 lua_pushlightuserdata 将这些指针作为lightuserdata传递到Lua端，然后Lua可以将其返回给堆栈上的库(或其他C代码).Lua代码可以将lightuserdata用作任何其他值，例如将其存储在表中，甚至用作表键.

For example, you can use them to refer to data you allocate with malloc, or statically allocate in your module. Your C library can transfer these pointers to the Lua side as a lightuserdata using lua_pushlightuserdata, and later Lua can give it back to your library (or other C code) on the stack. Lua code can use the lightuserdata as any other value, storing it in a table, for example, even as a table key.

附录

要回答您的修订问题，如果要向指针添加偏移量，请在C侧执行.将lightuserdata和整数偏移量传递给C，然后让C使用 ptr [n]

To answer your revised question, if you want to add an offset to the pointer, do it on the C side. Pass the lightuserdata and the integer offset to C, and let C do the offset using ptr[n]

void * ptr = lua_touserdata(L, idx1);
lua_Integer n = lua_tointeger(L. idx2);
// do something with
((char *)ptr)[n];

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