在使用union调用PInvoke结构时，使用StructLayout（LayoutKind.Explicit）时我做错了什么？

时间：2009-10-21 17:59:01

标签： c# .net pinvoke union structlayout

以下是一个完整的程序。只要你不取消顶部的'#define BROKEN'，它就能正常工作。中断是由于PInvoke无法正确编组联合。所讨论的INPUT_RECORD结构具有许多可能使用的子结构，具体取决于EventType中的值。

我不明白的是，当我只定义KEY_EVENT_RECORD的单个子结构时，它在偏移量4处使用显式声明。但是当我在同一偏移量处添加其他结构时，结构的内容得到了完全被冲洗了。

//UNCOMMENT THIS LINE TO BREAK IT:
//#define BROKEN

using System;
using System.Runtime.InteropServices;

class ConIOBroken
{
    static void Main()
    {
        int nRead = 0;
        IntPtr handle = GetStdHandle(-10 /*STD_INPUT_HANDLE*/);
        Console.Write("Press the letter: 'a': ");

        INPUT_RECORD record = new INPUT_RECORD();
        do
        {
            ReadConsoleInputW(handle, ref record, 1, ref nRead);
        } while (record.EventType != 0x0001/*KEY_EVENT*/);

        Assert.AreEqual((short)0x0001, record.EventType);
        Assert.AreEqual(true, record.KeyEvent.bKeyDown);
        Assert.AreEqual(0x00000000, record.KeyEvent.dwControlKeyState & ~0x00000020);//strip num-lock and test
        Assert.AreEqual('a', record.KeyEvent.UnicodeChar);
        Assert.AreEqual((short)0x0001, record.KeyEvent.wRepeatCount);
        Assert.AreEqual((short)0x0041, record.KeyEvent.wVirtualKeyCode);
        Assert.AreEqual((short)0x001e, record.KeyEvent.wVirtualScanCode);
    }

    static class Assert { public static void AreEqual(object x, object y) { if (!x.Equals(y)) throw new ApplicationException(); } }

    [DllImport("Kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    public static extern IntPtr GetStdHandle(int nStdHandle);

    [DllImport("Kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    public static extern bool ReadConsoleInputW(IntPtr hConsoleInput, ref INPUT_RECORD lpBuffer, int nLength, ref int lpNumberOfEventsRead);

    [StructLayout(LayoutKind.Explicit)]
    public struct INPUT_RECORD
    {
        [FieldOffset(0)]
        public short EventType;
        //union {
        [FieldOffset(4)]
        public KEY_EVENT_RECORD KeyEvent;
#if BROKEN
        [FieldOffset(4)]
        public MOUSE_EVENT_RECORD MouseEvent;
        [FieldOffset(4)]
        public WINDOW_BUFFER_SIZE_RECORD WindowBufferSizeEvent;
        [FieldOffset(4)]
        public MENU_EVENT_RECORD MenuEvent;
        [FieldOffset(4)]
        public FOCUS_EVENT_RECORD FocusEvent;
        //}
#endif
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct KEY_EVENT_RECORD
    {
        public bool bKeyDown;
        public short wRepeatCount;
        public short wVirtualKeyCode;
        public short wVirtualScanCode;
        public char UnicodeChar;
        public int dwControlKeyState;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct MOUSE_EVENT_RECORD
    {
        public COORD dwMousePosition;
        public int dwButtonState;
        public int dwControlKeyState;
        public int dwEventFlags;
    };

    [StructLayout(LayoutKind.Sequential)]
    public struct WINDOW_BUFFER_SIZE_RECORD
    {
        public COORD dwSize;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct MENU_EVENT_RECORD
    {
        public int dwCommandId;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct FOCUS_EVENT_RECORD
    {
        public bool bSetFocus;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct COORD
    {
        public short X;
        public short Y;
    }
}

更新

对于那些担心结构声明本身的人：

  1. bool被视为32位值
  2. 数据偏移量（4）的原因是允许32位结构对齐，这会阻止并集从偏移量2开始。

    3. 同样，我的问题是没有使PInvoke工作，它试图弄清楚为什么这些额外的结构（假设在相同的偏移量）通过简单地添加它们来提升数据。

6 个答案:

答案 0 :(得分：2)

我相信如果你制作类型为uint的bSetFocus和dwCommandId会有效。

将来，请查看PInvoke wiki以获取正确的签名。它通常是准确的，或者至少是一个很好的起点。

答案 1 :(得分：1)

1）public bool bKeyDown应该是Int32 bKeyDown，因为它是c ++中的BOOL（4bytes）

2）public bool bSetFocus应该是Int32

答案 2 :(得分：1)


//UNCOMMENT THIS LINE TO BREAK IT:
//#define BROKEN



using System;
using System.Runtime.InteropServices;



class ConIOBroken
{
    static void Main()
    {
        int nRead = 0;
        IntPtr handle = GetStdHandle(-10 /STD_INPUT_HANDLE/);
        Console.Write("Press the letter: 'a': ");



    INPUT_RECORD record = new INPUT_RECORD();
    do
    {
        ReadConsoleInputW(handle, ref record, 1, ref nRead);
    } while (record.EventType != 0x0001/*KEY_EVENT*/);

    Assert.AreEqual((short)0x0001, record.EventType);
    Assert.AreEqual(1u, record.KeyEvent.bKeyDown);
    Assert.AreEqual(0x00000000, record.KeyEvent.dwControlKeyState & ~0x00000020);//strip num-lock and test
    Assert.AreEqual('a', record.KeyEvent.UnicodeChar);
    Assert.AreEqual((short)0x0001, record.KeyEvent.wRepeatCount);
    Assert.AreEqual((short)0x0041, record.KeyEvent.wVirtualKeyCode);
    Assert.AreEqual((short)0x001e, record.KeyEvent.wVirtualScanCode);
    return;
}

static class Assert { public static void AreEqual(object x, object y) { if (!x.Equals(y)) throw new ApplicationException(); } }

[DllImport("Kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
public static extern IntPtr GetStdHandle(int nStdHandle);

[DllImport("Kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
public static extern bool ReadConsoleInputW(IntPtr hConsoleInput, ref INPUT_RECORD lpBuffer, int nLength, ref int lpNumberOfEventsRead);

[StructLayout(LayoutKind.Explicit)]
public struct INPUT_RECORD
{
    [FieldOffset(0)]
    public short EventType;
    //union {
    [FieldOffset(4)]
    public KEY_EVENT_RECORD KeyEvent;
    [FieldOffset(4)]
    public MOUSE_EVENT_RECORD MouseEvent;
    [FieldOffset(4)]
    public WINDOW_BUFFER_SIZE_RECORD WindowBufferSizeEvent;
    [FieldOffset(4)]
    public MENU_EVENT_RECORD MenuEvent;
    [FieldOffset(4)]
    public FOCUS_EVENT_RECORD FocusEvent;
}

[StructLayout(LayoutKind.Sequential)]
public struct KEY_EVENT_RECORD
{
    public uint bKeyDown;
    public short wRepeatCount;
    public short wVirtualKeyCode;
    public short wVirtualScanCode;
    public char UnicodeChar;
    public int dwControlKeyState;
}

[StructLayout(LayoutKind.Sequential)]
public struct MOUSE_EVENT_RECORD
{
    public COORD dwMousePosition;
    public int dwButtonState;
    public int dwControlKeyState;
    public int dwEventFlags;
};

[StructLayout(LayoutKind.Sequential)]
public struct WINDOW_BUFFER_SIZE_RECORD
{
    public COORD dwSize;
}

[StructLayout(LayoutKind.Sequential)]
public struct MENU_EVENT_RECORD
{
    public int dwCommandId;
}

[StructLayout(LayoutKind.Sequential)]
public struct FOCUS_EVENT_RECORD
{
    public uint bSetFocus;
}

[StructLayout(LayoutKind.Sequential)]
public struct COORD
{
    public short X;
    public short Y;
}




}

答案 3 :(得分：0)

只是想一想，如果你最后声明最大的字段会发生什么？也许P / Invoke正在复制到最后一个字段，该字段在前面的字段之前结束。

答案 4 :(得分：0)

尝试将手动计算的“大小”字段添加到StructLayout属性，如下所示：

[StructLayout(LayoutKind.Explicit, Size=...)]

答案 5 :(得分：0)

bool的原始代码包含13个字节，从FieldOffset（4）开始...
从同一偏移量开始的MOUSE_EVENT_RECORD从同一偏移量开始，共有16个字节。

当你将bool（1byte）更改为uint（4bytes）时，你就组成了3个字节。

相关问题
最新问题