C# PInvoke out 字符串声明

问题描述

在 C# PInvoke 中，如何传递字符串缓冲区以便 C DLL 填充它并返回?PInvoke 声明是什么?

In C# PInvoke, how do I pass a string buffer so that the C DLL fills it and returns? What will be the PInvoke declaration?

C 函数声明是

int GetData(char* data, int buflength);

在 C# 中，我已将其声明为

In C#, I have declared it as

[DllImport(DllName)]
static extern Int32 GetData([MarshalAs(UnmanagedType.LPStr)]StringBuilder receiveddata, Int32 buflen);

正确吗?我像这样传递 StringBuilder 变量

Is it correct? I'm passing the StringBuilder variable like this

int bufferLength = 32;
StringBuilder data = new StringBuilder(bufferLength);
int result = GetData(data, bufferLength);

我想知道它是否正确?

谢谢

推荐答案

我认为是正确的.

[DllImport(DllName)]
static extern int GetData(StringBuilder data, int length);

是这样调用的:

StringBuilder data = new StringBuilder(32);
GetData(data, data.Capacity);

我曾经想对我的函数返回的字节有更多的控制，并这样做了:

I once wanted to have more control over the bytes returned by my function and did it like this:

[DllImport(DllName)]
private unsafe static bool GetData(byte* data, int length);

这样使用:

byte[] bytes = new byte[length];

fixed(byte* ptr = bytes)
{
  bool success = Library.GetData(ptr, length);

  if (!success)
    Library.GetError();

  return Encoding.UTF8.GetString(bytes);
}

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