Swift:如何调用从dylib加载的C函数 [英] Swift: How to call a C function loaded from a dylib

问题描述

有没有一种方法可以调用从Swift的dylib加载的C函数?

Is there a way to call a C function loaded from a dylib from Swift?

这是我的 dylib 文件:

cppdemofile.cpp

cppdemofile.cpp

#include "cppdemofile.h"

int add(int a, int b) {
    return a + b;
}

cppdemofile.h

cppdemofile.h

#ifndef __CppDemoLibrary__cppdemofile__
#define __CppDemoLibrary__cppdemofile__

#pragma GCC visibility push(default)

extern "C" int add(int a, int b);

#pragma GCC visibility pop

#endif

编译为dylib并检查:

compile to dylib and check:

nm -gU libCppDemoLibrary.dylib
0000000000000f80 T _add

...将libCppDemoLibrary.dylib复制到~/lib ...

... copy libCppDemoLibrary.dylib to ~/lib...

快速程序:

@IBAction func buttonClick(sender: NSButton) {
    let handle = dlopen("libCppDemoLibrary.dylib", RTLD_NOW)
    if (handle != nil) {
        var sym = dlsym(handle, "add")
        if (sym != nil) {
            let pointer = UnsafeMutablePointer<(CInt, CInt) -> CInt>(sym)

            // When debugging, I'm reaching up to this point...
            // but now, how do I call the 'add' function here???
            // var result = ???

            // label.stringValue = "Total: " + String(result)
        }
    }
}

如何调用add函数?是否可以使用dylib?我应该改为将这些资源添加到我的swift项目中吗?

How do I call the add function? Is it ok to use a dylib? Should I instead add these sources to my swift project?

推荐答案

可以从Swift调用add函数，因为您 定义它与extern "C"具有C链接.

Calling the add function from Swift is possible because you defined it to have C linkage with extern "C".

使库成为一个Swift模块(如上面的jtbandes所建议 评论)可能是更好的解决方案， 但是这是您如何使用dlsym()从Swift返回的函数指针的方法:

Making the library a Swift module (as suggested by jtbandes in above comments) might be the better solution, but here is how you can use the function pointer return by dlsym() from Swift:

首先添加

typedef int(*addFunc)(int, int);

到桥接头文件，或者定义

to the bridging header file, or alternatively define

typealias addFunc = @convention(c) (CInt, CInt) -> CInt

在Swift中.然后执行以下操作:

in Swift. Then the following works:

let handle = dlopen(path, RTLD_NOW)
if (handle != nil) {
    var sym = dlsym(handle, "add")
    if (sym != nil) {
        let f = unsafeBitCast(sym, addFunc.self)
        let result = f(12, 45)
        print(result)
    }
    dlclose(handle)
}

当然，如果addFunc与 加载函数的实际签名.

Of course this will crash if addFunc does not match the actual signature of the loaded function.

更新迅速3:

if let handle = dlopen(path, RTLD_NOW) {
    if let sym = dlsym(handle, "add") {
        let f = unsafeBitCast(sym, to: addFunc.self)
        let result = f(12, 45)
        print(result)
    }
    dlclose(handle)
}

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