64位C风格DLL在VB.NET中unsigned short*的DllImport类型映射问询

Hey there! Let's break down how to properly map that unsigned short* parameter from your PhiOpticsSDK DLL to VB.NET—you were on the right track with IntPtr, but let's clarify the confusion around "size mismatch" and cover the best options for your specific PHI_ComputePush function.

1. The Easiest (and Most Common) Approach: Use UInt16() Arrays #

Given your function deals with rows and cols (sounds like image data!), your ptr_in is almost certainly pointing to a contiguous array of 16-bit unsigned integers. In this case, you don't need to mess with raw pointers at all—VB.NET and the CLR will automatically marshal a UInt16() array to a C-style unsigned short* for you.

Here's the corrected DllImport declaration for PHI_ComputePush:

<DllImport("PhiOpticsSDK.dll", CallingConvention := CallingConvention.Cdecl)>
Private Shared Function PHI_ComputePush(
    ByVal ptr_in As UInt16(),
    ByVal rows As Long,
    ByVal cols As Long,
    ByVal pattern As Long,
    ByVal timeout_ms As Long,
    Optional ByVal background_offset As Single = 0.0F
) As IntPtr
End Function

Quick notes to align with your existing code:

• I mapped PHI_64 to Long since it's defined as long long in your header—this matches the 64-bit integer size correctly.
• PHI_STATUS stays as IntPtr like your PHI_LibraryInitialize declaration.
• Added CallingConvention.Cdecl because most C-style DLLs use this calling convention; omitting it can cause stack corruption bugs.

2. When You Need Manual Memory Control: Use IntPtr #

If you have to work with unmanaged memory directly (e.g., receiving a pointer from another DLL function), IntPtr is still valid. The "size mismatch" you noticed is probably mixing up the size of the pointer itself (8 bytes on 64-bit systems) with the size of the data it points to (2 bytes for unsigned short). Those are two different things!

When using IntPtr, you'll need to use the Marshal class to read/write the underlying data. For example:

' Read a single unsigned short from the pointer
Dim singleValue As UInt16 = Marshal.ReadUInt16(ptr_in)

' Copy the entire array from unmanaged to managed memory
Dim pixelArray As UInt16() = New UInt16(rows * cols - 1) {}
Marshal.Copy(ptr_in, pixelArray, 0, pixelArray.Length)

And the corresponding function declaration would be:

<DllImport("PhiOpticsSDK.dll", CallingConvention := CallingConvention.Cdecl)>
Private Shared Function PHI_ComputePush(
    ByVal ptr_in As IntPtr,
    ByVal rows As Long,
    ByVal cols As Long,
    ByVal pattern As Long,
    ByVal timeout_ms As Long,
    Optional ByVal background_offset As Single = 0.0F
) As IntPtr
End Function

Key Things to Double-Check #

• Confirm PHI_EXP_CONV matches CallingConvention.Cdecl—if your DLL uses stdcall instead, swap that out in the DllImport attribute.
• Make sure your Long mapping for PHI_64 is correct (since long long is a 64-bit signed integer, VB.NET's Long maps perfectly to .NET's Int64).
• The optional background_offset parameter is properly marked with Optional in VB.NET to match the C++ default value.

内容的提问来源于stack exchange，提问作者Mikhail