使用生成的 Golang DLL 返回字符串或 *C.Char

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问题内容

我一直在尝试关注z505/goDLL repo 并遇到了一个大问题。如果我无法读取结果的输出变量，该方法将无法返回字符串。

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

预期输出结果：

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!

当前结果：

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

demo
Message:  From DLL: Hello, demo!

没有可见的恐慌，没有发现错误。只是输出不完整thx

正确答案

无论如何，经过一段时间的尝试和错误“ing”，这就是解决方案

走

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

它可能会被许多其他可能试图完成与我一样的人使用。

感谢您的提示和耐心 JimB

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