经过与会代表在D外部C函数 [英] Pass delegates to external C functions in D

问题描述

我如何通过一个委托以函数指针，D中的外部C函数？

How do I pass a delegate to an external C function taking a function pointer, in D?

推荐答案

让我交交我说的新闻组：

Let me cross post what I said on the newsgroup:

我如何通过一个委托给外部C函数取
  函数指针？

How do I pass a delegate to an external C function taking a function pointer?

您不能直接一般做到这一点，除非你能修改C
功能，那么你就可以破解它周围，而是一个委托和
普通函数指针是pretty不同的动物。

You can't do it directly in general, unless you can modify the C function, then you can hack around it, but a delegate and a regular function pointer are pretty different animals.

但是，也许你可以神奇的本事。注意：

But perhaps you can magic hack it. Observe:

// a C function that needs a plain function
extern(C) void test(void function() f) {
    // pretend this is implemented in C
    f();
}

// just create a random delegate
void delegate() foo(int a) {
    return { import std.stdio; writeln(a); };
}

// what we want to work
void main() {
    auto dg = foo(10);
    dg(); // works

    //test(dg); // won't work
    test(bindDelegate(dg)); // we want this
}

// transform delegate into pointer..
import std.traits;
auto bindDelegate(T, string file = __FILE__, size_t line = __LINE__)(T t) if(isDelegate!T) {
    static T dg;

    dg = t;

    extern(C)
    static ReturnType!T func(ParameterTypeTuple!T args) {
            return dg(args);
    }

    return &func;
}

什么bindDelegate所做的是创建一个特殊的静态变量和
功能为特定的呼叫。这是因为如果我们写了一个单独的
函数和全局持有它。

What bindDelegate does is create a special static variable and function for that specific call. It is as if we wrote a separate function and global to hold it.

的 __ __ FILE ， __ __ LINE 东西是一个肮脏的黑客攻击，使其
实例化一个独立的变量+功能，对不同的
线，使全局变量控股委托不会那么
轻易改写。

The __FILE__, __LINE__ things are a filthy hack to make it instantiate a separate variable+function pair for different lines so the global variable holding the delegate won't be so easily overwritten.

这篇关于经过与会代表在D外部C函数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！