douhui0975
douhui0975
2018-01-11 13:20
采纳率: 100%
浏览 630

求助:使用生成的Golang DLL返回字符串或* C.Char

我一直试图遵循z505/goDLL的方法,但遇到了一个大问题。该方法无法返回字符串,我无法读取结果的输出变量。

这是我目前使用的代码(Go)(完整代码https://play.golang.org/p/Yfg85DCeMLh):

//export PrintHello2
func PrintHello2(Input *C.char, Output **C.char) int32 {
    fmt.Println(C.GoString(Input))
    *Output = C.CString(fmt.Sprintf("From DLL: Hello, %s!
", C.GoString(Input)))
    fmt.Println("Message: ", C.GoString(*Output))
    return 1
}

//export PrintHello3
func PrintHello3(Input *C.char, Output *int32) int32 {
    fmt.Println(C.GoString(Input))
    *Output = 3
    fmt.Println("Value: ", *Output)
    return 0
}

C# 测试代码:

class Program
{
    [DllImport("goDLL.dll", CharSet = CharSet.Unicode)]
    public static extern int PrintHello2(byte[] data, ref byte[] output);

    [DllImport("goDLL.dll", CharSet = CharSet.Unicode)]
    public static extern int PrintHello3(byte[] data, ref int output);

    static void Main(string[] args)
    {
        string res = "demo";
        byte[] output = null;
        Int32 refVal = 0;

        Console.WriteLine("PrintHello3 Returns: " + PrintHello3(Encoding.UTF8.GetBytes(res), ref refVal));
        Console.WriteLine("Ref Val changed to: " + refVal + "
");
        Console.WriteLine("PrintHello2 Returns: " + PrintHello2(Encoding.UTF8.GetBytes(res), ref output));
        Console.WriteLine("Ref Val changed to: " + Encoding.UTF8.GetString(output) + "
");
    }
}

预期产出结果:

C:\tmp\DLL>ConsoleApp.exe
demo
Value:  3
PrintHello3 Returns: 0
Ref Val changed to: 3

demo
Message:  From DLL: Hello, demo!
PrintHello2 Returns: 1
Ref Val changed to: From DLL: Hello, demo!

实际结果:

C:\tmp\DLL>ConsoleApp.exe
demo
Value:  3
PrintHello3 Returns: 0
Ref Val changed to: 3

demo
Message:  From DLL: Hello, demo!

我没有发现错误。

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1条回答 默认 最新

  • dongzhong1929
    dongzhong1929 2018-01-12 13:43
    已采纳

    Anyway, after some time trying and error"ing", this is the solution

    Go

    //export PrintHello2
    func PrintHello2(Input *C.char, Output **C.char) int32 {
        *Output = C.CString(fmt.Sprintf("From DLL: Hello, %s!
    ", C.GoString(Input)))
        return int32(len(C.GoString(*Output)))
    }
    
    //export PrintHello4
    func PrintHello4(Input *C.char) *C.char{
        return C.CString(fmt.Sprintf("From DLL: Hello, %s!
    ", C.GoString(Input)))
    }
    

    C#

    class Program
    {
        [DllImport("goDLL.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall)]
        public static extern int PrintHello2([In] byte[] data, ref IntPtr output);
    
        [DllImport("goDLL.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall)]
        public static extern IntPtr PrintHello4(byte[] data);
    
        static void Main(string[] args)
        {
            string res = "demo";
            IntPtr output= IntPtr.Zero;
            var a = PrintHello4(Encoding.UTF8.GetBytes(res));
    
            Console.WriteLine("PrintHello4 Returns: " + Marshal.PtrToStringAnsi(a));
            var i = PrintHello2(Encoding.UTF8.GetBytes(res), ref output);
    
            Console.WriteLine("PrintHello2 Returns: " + i);
            Console.WriteLine("Ref Val changed to: " + Marshal.PtrToStringAnsi(output, i));
        }
    }
    

    It will probably be used by many others that might be trying to accomplish the same as i am.

    Thanks for the tips and pacience JimB

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