从Windows的C函数返回一个字符串 [英] Returning strings from Windows C functions

问题描述

我是一个完整的新手在C和C ++纯粹的Windows API级的功能和最近已尝试用.NET互操作能力。我已经建立已成功为.NET调用者返回数值（INT /浮动等），一个简单的库，但我不会有尽可能多的运气字符串。

I am a complete novice at pure Windows API-level functions in C and C++ and have been experimenting recently with .NET interoperability. I have built a simple library which has successfully returned numeric values (int/float, etc.) to a .NET caller, but I am not having as much luck with strings.

我已经尝试了多种不同的数据类型，但没有出现工作：LPSTR，LPCSTR，LPCTSTR和LPCWSTR。诚然，我没有尝试过的char *。另外，一旦方法被设置为返回一个字符串，它需要由.NET编组作为一个特定的数据类型，或可以被简单地直接读入以System.String对象？我曾尝试解析为一个IntPtr然后铸造成一个字符串，但没有成功。

I have tried a variety of different data types, but none appear to work: LPSTR, LPCSTR, LPCTSTR, and LPCWSTR. Admittedly, I haven't tried char*. Also, once a method is set up to return a string, does it require marshalling by .NET as a specific data type, or could it be simply read straight into a System.String object? I have tried parsing into an IntPtr then casting into a string but that did not work.

推荐答案

做什么的Windows API的一样。它通常不会返回指针，它填补了您传递的缓冲区。

Do what the Windows API does. It typically does not return pointers, it fills in buffers that you pass in.

管理code：

[DllImport("YourLibrary", CharSet = CharSet.Auto)] 
static extern Int32  SomeArbitraryFunction (
    String        input,          // string passed to API (LPCSTR) 
    StringBuilder output,         // output filled by API (LPSTR)    
    Int32         outputMaxLen    // StringBuilder.Capacity
); 

在C / C ++侧：

On the C/C++ side:

DWORD WINAPI SomeArbitraryFunction (
    LPCSTR input,
    LPSTR output,
    DWORD outputMaxLen
);

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