OpenStreamOnFile

// MAPI32.dll
#include <windows.h>

HRESULT OpenStreamOnFile(
    LPALLOCATEBUFFER lpAllocateBuffer,
    LPFREEBUFFER lpFreeBuffer,
    DWORD ulFlags,
    CHAR* lpszFileName,
    CHAR* lpszPrefix,   // optional
    IStream** lppStream
);

<DllImport("MAPI32.dll", ExactSpelling:=True)>
Public Shared Function OpenStreamOnFile(
    lpAllocateBuffer As IntPtr,   ' LPALLOCATEBUFFER
    lpFreeBuffer As IntPtr,   ' LPFREEBUFFER
    ulFlags As UInteger,   ' DWORD
    lpszFileName As IntPtr,   ' CHAR*
    lpszPrefix As IntPtr,   ' CHAR* optional
    lppStream As IntPtr   ' IStream** out
) As Integer
End Function

' lpAllocateBuffer : LPALLOCATEBUFFER
' lpFreeBuffer : LPFREEBUFFER
' ulFlags : DWORD
' lpszFileName : CHAR*
' lpszPrefix : CHAR* optional
' lppStream : IStream** out
Declare PtrSafe Function OpenStreamOnFile Lib "mapi32" ( _
    ByVal lpAllocateBuffer As LongPtr, _
    ByVal lpFreeBuffer As LongPtr, _
    ByVal ulFlags As Long, _
    ByVal lpszFileName As LongPtr, _
    ByVal lpszPrefix As LongPtr, _
    ByVal lppStream As LongPtr) As Long
' VBA7前提(PtrSafe)。32bit Office では LongPtr→Long。Integer=16bit / Long=32bit / LongLong=64bit。

import ctypes
from ctypes import wintypes

OpenStreamOnFile = ctypes.windll.mapi32.OpenStreamOnFile
OpenStreamOnFile.restype = ctypes.c_int
OpenStreamOnFile.argtypes = [
    ctypes.c_void_p,  # lpAllocateBuffer : LPALLOCATEBUFFER
    ctypes.c_void_p,  # lpFreeBuffer : LPFREEBUFFER
    wintypes.DWORD,  # ulFlags : DWORD
    ctypes.POINTER(ctypes.c_byte),  # lpszFileName : CHAR*
    ctypes.POINTER(ctypes.c_byte),  # lpszPrefix : CHAR* optional
    ctypes.c_void_p,  # lppStream : IStream** out
]

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('MAPI32.dll')
OpenStreamOnFile = Fiddle::Function.new(
  lib['OpenStreamOnFile'],
  [
    Fiddle::TYPE_VOIDP,  # lpAllocateBuffer : LPALLOCATEBUFFER
    Fiddle::TYPE_VOIDP,  # lpFreeBuffer : LPFREEBUFFER
    -Fiddle::TYPE_INT,  # ulFlags : DWORD
    Fiddle::TYPE_VOIDP,  # lpszFileName : CHAR*
    Fiddle::TYPE_VOIDP,  # lpszPrefix : CHAR* optional
    Fiddle::TYPE_VOIDP,  # lppStream : IStream** out
  ],
  Fiddle::TYPE_INT)

#[link(name = "mapi32")]
extern "system" {
    fn OpenStreamOnFile(
        lpAllocateBuffer: *const core::ffi::c_void,  // LPALLOCATEBUFFER
        lpFreeBuffer: *const core::ffi::c_void,  // LPFREEBUFFER
        ulFlags: u32,  // DWORD
        lpszFileName: *mut i8,  // CHAR*
        lpszPrefix: *mut i8,  // CHAR* optional
        lppStream: *mut *mut core::ffi::c_void  // IStream** out
    ) -> i32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("MAPI32.dll")]
public static extern int OpenStreamOnFile(IntPtr lpAllocateBuffer, IntPtr lpFreeBuffer, uint ulFlags, IntPtr lpszFileName, IntPtr lpszPrefix, IntPtr lppStream);
"@
$api = Add-Type -MemberDefinition $sig -Name 'MAPI32_OpenStreamOnFile' -Namespace Win32 -PassThru
# $api::OpenStreamOnFile(lpAllocateBuffer, lpFreeBuffer, ulFlags, lpszFileName, lpszPrefix, lppStream)

#uselib "MAPI32.dll"
#func global OpenStreamOnFile "OpenStreamOnFile" sptr, sptr, sptr, sptr, sptr, sptr
; OpenStreamOnFile lpAllocateBuffer, lpFreeBuffer, ulFlags, varptr(lpszFileName), varptr(lpszPrefix), lppStream   ; 戻り値は stat
; lpAllocateBuffer : LPALLOCATEBUFFER -> "sptr"
; lpFreeBuffer : LPFREEBUFFER -> "sptr"
; ulFlags : DWORD -> "sptr"
; lpszFileName : CHAR* -> "sptr"
; lpszPrefix : CHAR* optional -> "sptr"
; lppStream : IStream** out -> "sptr"
; ※HSP3.7は #func のため戻り値はシステム変数 stat に格納されます。

#uselib "MAPI32.dll"
#cfunc global OpenStreamOnFile "OpenStreamOnFile" sptr, sptr, int, var, var, sptr
; res = OpenStreamOnFile(lpAllocateBuffer, lpFreeBuffer, ulFlags, lpszFileName, lpszPrefix, lppStream)
; lpAllocateBuffer : LPALLOCATEBUFFER -> "sptr"
; lpFreeBuffer : LPFREEBUFFER -> "sptr"
; ulFlags : DWORD -> "int"
; lpszFileName : CHAR* -> "var"
; lpszPrefix : CHAR* optional -> "var"
; lppStream : IStream** out -> "sptr"
; ※出力/バッファ引数は var 方式(変数を直接渡す)。varptr 方式にも切替可。

; HRESULT OpenStreamOnFile(LPALLOCATEBUFFER lpAllocateBuffer, LPFREEBUFFER lpFreeBuffer, DWORD ulFlags, CHAR* lpszFileName, CHAR* lpszPrefix, IStream** lppStream)
#uselib "MAPI32.dll"
#cfunc global OpenStreamOnFile "OpenStreamOnFile" intptr, intptr, int, var, var, intptr
; res = OpenStreamOnFile(lpAllocateBuffer, lpFreeBuffer, ulFlags, lpszFileName, lpszPrefix, lppStream)
; lpAllocateBuffer : LPALLOCATEBUFFER -> "intptr"
; lpFreeBuffer : LPFREEBUFFER -> "intptr"
; ulFlags : DWORD -> "int"
; lpszFileName : CHAR* -> "var"
; lpszPrefix : CHAR* optional -> "var"
; lppStream : IStream** out -> "intptr"
; ※出力/バッファ引数は var 方式(変数を直接渡す)。varptr 方式にも切替可。

import (
	"golang.org/x/sys/windows"
	"unsafe"
)

var (
	mapi32 = windows.NewLazySystemDLL("MAPI32.dll")
	procOpenStreamOnFile = mapi32.NewProc("OpenStreamOnFile")
)

// lpAllocateBuffer (LPALLOCATEBUFFER), lpFreeBuffer (LPFREEBUFFER), ulFlags (DWORD), lpszFileName (CHAR*), lpszPrefix (CHAR* optional), lppStream (IStream** out)
r1, _, err := procOpenStreamOnFile.Call(
	uintptr(lpAllocateBuffer),
	uintptr(lpFreeBuffer),
	uintptr(ulFlags),
	uintptr(lpszFileName),
	uintptr(lpszPrefix),
	uintptr(lppStream),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // HRESULT

function OpenStreamOnFile(
  lpAllocateBuffer: Pointer;   // LPALLOCATEBUFFER
  lpFreeBuffer: Pointer;   // LPFREEBUFFER
  ulFlags: DWORD;   // DWORD
  lpszFileName: Pointer;   // CHAR*
  lpszPrefix: Pointer;   // CHAR* optional
  lppStream: Pointer   // IStream** out
): Integer; stdcall;
  external 'MAPI32.dll' name 'OpenStreamOnFile';

result := DllCall("MAPI32\OpenStreamOnFile"
    , "Ptr", lpAllocateBuffer   ; LPALLOCATEBUFFER
    , "Ptr", lpFreeBuffer   ; LPFREEBUFFER
    , "UInt", ulFlags   ; DWORD
    , "Ptr", lpszFileName   ; CHAR*
    , "Ptr", lpszPrefix   ; CHAR* optional
    , "Ptr", lppStream   ; IStream** out
    , "Int")   ; return: HRESULT

●OpenStreamOnFile(lpAllocateBuffer, lpFreeBuffer, ulFlags, lpszFileName, lpszPrefix, lppStream) = DLL("MAPI32.dll", "int OpenStreamOnFile(void*, void*, dword, void*, void*, void*)")
# 呼び出し: OpenStreamOnFile(lpAllocateBuffer, lpFreeBuffer, ulFlags, lpszFileName, lpszPrefix, lppStream)
# lpAllocateBuffer : LPALLOCATEBUFFER -> "void*"
# lpFreeBuffer : LPFREEBUFFER -> "void*"
# ulFlags : DWORD -> "dword"
# lpszFileName : CHAR* -> "void*"
# lpszPrefix : CHAR* optional -> "void*"
# lppStream : IStream** out -> "void*"
# なでしこ1は32bit・ANSI(Shift_JIS)。文字列=char*(ANSI)、ポインタ/ハンドル=void*(4byte)。