如何在以struct作为参数的Ruby FFI方法中包装函数? [英] How to wrap function in Ruby FFI method that takes struct as argument?

问题描述

我正在尝试使用ruby-ffi从共享库中调用函数.我将以下内容编译为共享对象:

I am trying to call a function from a shared object using ruby-ffi. I compiled the following into a shared object:

#include <stdio.h>

typedef struct _WHAT {
  int d;
  void * something;
} WHAT;

int doit(WHAT w) {
  printf("%d\n", w.d);
  return w.d;
}

问题是，如何在Ruby中使用attach_function声明函数?在Ruby的参数列表中如何定义struct参数(w w)?它不是:pointer，并且似乎不适合ruby-ffi文档中描述的任何其他可用类型，那么它将是什么呢?

The problem is, how do I declare the function with attach_function in Ruby? How is the struct argument (WHAT w) defined in the list of arguments in Ruby? It is not a :pointer, and does not seem to fit any of the other available types described in the ruby-ffi documentation, so what would it be?

推荐答案

在如何使用Structs "rel =" noreferrer> https://github.com/ffi/ffi/wiki/Structs ，针对您的情况:

Check how to use Structs in https://github.com/ffi/ffi/wiki/Structs, for your case:

class What < FFI::Struct
  layout :d, :int,
         :something, :pointer
end

现在附加函数，由于您要通过值传递结构，因此参数将变为What.by_value(用您命名的内容替换What)上面的struct类):

Now attach the function, the argument, since you are passing the struct by value, is going to be What.by_value(replacing What by whatever you have named you struct class above):

attach_function 'doit', [What.by_value],:int

现在如何调用函数:

mywhat = DoitLib::What.new
mywhat[:d] = 1234
DoitLib.doit(mywhat)

现在是完整文件:

require 'ffi'

module DoitLib
  extend FFI::Library
  ffi_lib "path/to/yourlibrary.so"

  class What < FFI::Struct
    layout :d, :int,
           :something, :pointer
  end

  attach_function 'doit', [What.by_value],:int

end

mywhat = DoitLib::What.new
mywhat[:d] = 1234
DoitLib.doit(mywhat)

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