GCHandleとMarshalについて迷ったらこれ

marshal.vb

Imports System.Runtime.InteropServices

Module Module1

    ' int hoge(int val) { return val; }
    <DllImport("ConsoleApplication2.dll", CallingConvention:=CallingConvention.Cdecl)>
    Public Function hoge(val As Int32) As Int32
    End Function

    ' int foo(int* val) { *val = *val + 200; return val; }
    <DllImport("ConsoleApplication2.dll", CallingConvention:=CallingConvention.Cdecl)>
    Public Function foo(val As IntPtr) As IntPtr
    End Function

    ' int bar(int* val) { **val = 900; return val; }
    <DllImport("ConsoleApplication2.dll", CallingConvention:=CallingConvention.Cdecl)>
    Public Function bar(val As IntPtr) As IntPtr
    End Function


    Sub Main()

        ' intをalloc
        Dim gchFoo As GCHandle = GCHandle.Alloc(0, GCHandleType.Pinned)
        gchFoo.Target = 200

        Console.WriteLine(hoge(10))

        ' int*を渡す
        Dim retFoo As IntPtr = foo(gchFoo.AddrOfPinnedObject)
        Dim dstFoo(0) As Integer
        ' 戻り値retを*retとしてdstFooにコピー
        Marshal.Copy(retFoo, dstFoo, 0, 1)

        ' int** bar
        Dim gchBar As GCHandle = GCHandle.Alloc(gchFoo.AddrOfPinnedObject, GCHandleType.Pinned)
        ' int**を渡す
        Dim retBar As IntPtr = bar(gchBar.AddrOfPinnedObject)
        Dim dstBar(0) As IntPtr
        Dim dstBarPtr(0) As Int32
        ' int**をint*にしてdstBarにコピー
        Marshal.Copy(retBar, dstBar, 0, 1)
        ' int*をintにしてdstBarPtrにコピー
        Marshal.Copy(dstBar(0), dstBarPtr, 0, 1)

        Console.ReadLine()

        gchFoo.Free()
    End Sub

End Module