[英]C# PInvoke out strings declaration
In C# PInvoke, how do I pass a string buffer so that the C DLL fills it and returns? 在C#PInvoke中,如何传递字符串缓冲区以便C DLL填充它并返回? What will be the PInvoke declaration? PInvoke宣言是什么?
The C function declaration is C函数声明是
int GetData(char* data, int buflength);
In C#, I have declared it as 在C#中,我已将其声明为
[DllImport(DllName)]
static extern Int32 GetData([MarshalAs(UnmanagedType.LPStr)]StringBuilder receiveddata, Int32 buflen);
Is it correct? 这是对的吗? I'm passing the StringBuilder variable like this 我像这样传递StringBuilder变量
int bufferLength = 32;
StringBuilder data = new StringBuilder(bufferLength);
int result = GetData(data, bufferLength);
I would like to know is it correct or not? 我想知道它是否正确?
Thanks 谢谢
I believe it's correct. 我相信这是正确的。
[DllImport(DllName)]
static extern int GetData(StringBuilder data, int length);
which is called like this: 这被称为:
StringBuilder data = new StringBuilder(32);
GetData(data, data.Capacity);
I once wanted to have more control over the bytes returned by my function and did it like this: 我曾经希望对我的函数返回的字节有更多的控制权,并且这样做:
[DllImport(DllName)]
private unsafe static bool GetData(byte* data, int length);
used like this: 像这样使用:
byte[] bytes = new byte[length];
fixed(byte* ptr = bytes)
{
bool success = Library.GetData(ptr, length);
if (!success)
Library.GetError();
return Encoding.UTF8.GetString(bytes);
}
I don't think that using MarshalAs attribute necessary here. 我不认为在这里使用MarshalAs属性是必要的。 StringBuilder is a right choice for char* out. StringBuilder是char * out的正确选择。
I guess it will be good to add the CharSet property since you are dealing with strings here. 我想添加CharSet属性会很好,因为你在这里处理字符串。
Like this: 像这样:
[DllImport(DllName, CharSet=CharSet.Auto)]
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