c++ - 如何调用 DeviceIoControl 来检索它需要的内存量？

Question

我正在尝试调用 DeviceIoControl(IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS) API，作为 shown here ，但我需要它首先“告诉我”它需要多少内存(与我链接到的代码不同。)

所以我这样调用它:

//First determine how much data do we need?
BYTE dummyBuff[1];
DWORD bytesReturned = 0;
if(!::DeviceIoControl(hDevice, dwIoControlCode, lpInBuffer, nInBufferSize, 
    dummyBuff, sizeof(dummyBuff), &bytesReturned, NULL))
{
    //Check last error
    int nError = ::GetLastError();
    if(nOSError == ERROR_INSUFFICIENT_BUFFER ||
        nOSError == ERROR_MORE_DATA)
    {
        //Alloc memory from 'bytesReturned' ...
    }
}

但它总是返回错误代码 87，或 ERROR_INVALID_PARAMETER 而我的 bytesReturned 始终为 0。

那我做错了什么？

Answer 1

获取所有磁盘卷范围的说明记录在 VOLUME_DISK_EXTENTS structure 下:

When the number of extents returned is greater than one (1), the error code ERROR_MORE_DATA is returned. You should call DeviceIoControl again, allocating enough buffer space based on the value of NumberOfDiskExtents after the first DeviceIoControl call.

如果传递小于 sizeof(VOLUME_DISK_EXTENTS) 的输出缓冲区，该行为也记录在 IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS control code 中:

If the output buffer is less than sizeof(VOLUME_DISK_EXTENTS), the call fails, GetLastError returns ERROR_INSUFFICIENT_BUFFER, and lpBytesReturned is 0 (zero).

虽然这解释了 lpBytesReturned 中的返回值，但它没有解释错误代码 87 (ERROR_INVALID_PARAMETER)¹⁾。

以下代码将返回所有卷的磁盘范围:

VOLUME_DISK_EXTENTS vde = { 0 };
DWORD bytesReturned = 0;
if ( !::DeviceIoControl( hDevice, IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS, NULL, 0, 
                         (void*)&vde, sizeof(vde), &bytesReturned, NULL ) )
{
    // Check last error
    int nError = ::GetLastError();
    if ( nError != ERROR_MORE_DATA )
    {
        // Unexpected error -> error out
        throw std::runtime_error( "DeviceIoControl() failed." );
    }

    size_t size = offsetof( VOLUME_DISK_EXTENTS, Extents[vde.NumberOfDiskExtents] );
    std::vector<BYTE> buffer( size );
    if ( !::DeviceIoControl( hDevice, IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS, NULL, 0, 
                             (void*)buffer.data(), size, &bytesReturned, NULL ) )
    {
        // Unexpected error -> error out
        throw std::runtime_error( "DeviceIoControl() failed." );
    }
    // At this point we have a fully populated VOLUME_DISK_EXTENTS structure
    const VOLUME_DISK_EXTENTS& result =
        *reinterpret_cast<const VOLUME_DISK_EXTENTS*>( buffer.data() );
}
else
{
    // Call succeeded; vde is populated with single disk extent.
}

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附加引用:

• Why do some structures end with an array of size 1?
• offsetof Macro

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¹⁾ 我猜测，BYTE[1] 开始于一个内存地址，该地址没有充分对齐 的对齐要求VOLUME_DISK_EXTENTS。