[英]PInvoke struct with array of unspecified length
C definitions C定义
typedef struct {
const uint8_t* buf;
int bufLen;
} Info;
int Foo(Info* info);
C# definitions C#定义
[StructLayout(LayoutKind.Sequential)]
public struct Info
{
// [MarshalAs( ??? )]
public byte[] buf;
int bufLen
}
[DllImport(...)]
public static extern int Foo(ref Info info);
I'm having trouble figuring out what to specify for the MarshalAs
attribute on byte[] buf
in the C# struct definition. 我在查找C#struct定义中
byte[] buf
上MarshalAs
属性的内容时遇到了麻烦。 The buffer is allocated on the .NET side, and its length is known at call time. 缓冲区在.NET端分配,其长度在调用时已知。
In a simple little test: 在一个简单的小测试中:
var info = new Info {
buf = new byte[] {0x40, 0x50, 0x60, 0x70},
bufLen = 4,
};
Foo(ref info);
Everything seems to be working correctly, but in fact the data in my buffer is incorrect. 一切似乎都正常,但事实上我的缓冲区中的数据是不正确的。 Printing it out from the DLL I see
01 00 80 00
- not sure what that is. 从DLL打印我看到
01 00 80 00
- 不知道那是什么。
I've tried: 我试过了:
MarshalAs
MarshalAs
[MarshalAs(UnmanagedType.SafeArray)]
and nothing works. 没有任何作用。
In general, I really don't know the best way to debug these kinds of problems either. 一般来说,我真的不知道调试这些问题的最佳方法。
Per Hans Passant's suggestion, I implemented the following: 根据Hans Passant的建议,我实施了以下内容:
[StructLayout(LayoutKind.Sequential)]
public struct Info : IDisposable
{
private IntPtr buf;
private int bufLen;
public Info(byte[] buf) : this() {
this.buf = Marshal.AllocHGlobal(buf.Length);
Marshal.Copy(buf, 0, this.buf, buf.Length);
this.bufLen = buf.Length;
}
public void Dispose() {
if (buf != IntPtr.Zero) {
Marshal.FreeHGlobal(buf);
buf= IntPtr.Zero;
}
}
}
I know it is too late.. but just in case if some one come here for an answer. 我知道为时已晚......但是如果有人来这里寻求答案的话。
I finally came up with next solution for similar exercise. 我终于想出了类似练习的下一个解决方案。
[StructLayout(LayoutKind.Sequential)]
public struct Info
{
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 8)]
public byte[] buf;
int bufLen
}
From MSDN 来自MSDN
Arrays can be marshaled as UnmanagedType.ByValArray, which requires you to set the MarshalAsAttribute.SizeConst field.
数组可以编组为UnmanagedType.ByValArray,它要求您设置MarshalAsAttribute.SizeConst字段。 The size can be set only as a constant.
大小只能设置为常量。
In my case the buffer size is 8 bytes. 在我的情况下,缓冲区大小是8个字节。
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