MsiOpenPackageW

// msi.dll  (Unicode / -W)
#include <windows.h>

DWORD MsiOpenPackageW(
    LPCWSTR szPackagePath,
    MSIHANDLE* hProduct
);

<DllImport("msi.dll", CharSet:=CharSet.Unicode, ExactSpelling:=True)>
Public Shared Function MsiOpenPackageW(
    <MarshalAs(UnmanagedType.LPWStr)> szPackagePath As String,   ' LPCWSTR
    <Out> ByRef hProduct As UInteger   ' MSIHANDLE* out
) As UInteger
End Function

' szPackagePath : LPCWSTR
' hProduct : MSIHANDLE* out
Declare PtrSafe Function MsiOpenPackageW Lib "msi" ( _
    ByVal szPackagePath As LongPtr, _
    ByRef hProduct As Long) As Long
' Unicode(W): 文字列は ByVal As LongPtr とし StrPtr(unicodeStr) を渡す
' VBA7前提(PtrSafe)。32bit Office では LongPtr→Long。Integer=16bit / Long=32bit / LongLong=64bit。

import ctypes
from ctypes import wintypes

MsiOpenPackageW = ctypes.windll.msi.MsiOpenPackageW
MsiOpenPackageW.restype = wintypes.DWORD
MsiOpenPackageW.argtypes = [
    wintypes.LPCWSTR,  # szPackagePath : LPCWSTR
    ctypes.c_void_p,  # hProduct : MSIHANDLE* out
]

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('msi.dll')
MsiOpenPackageW = Fiddle::Function.new(
  lib['MsiOpenPackageW'],
  [
    Fiddle::TYPE_VOIDP,  # szPackagePath : LPCWSTR
    Fiddle::TYPE_VOIDP,  # hProduct : MSIHANDLE* out
  ],
  -Fiddle::TYPE_INT)
# Wide strings: pass str.encode("UTF-16LE") + "\x00\x00"

#[link(name = "msi")]
extern "system" {
    fn MsiOpenPackageW(
        szPackagePath: *const u16,  // LPCWSTR
        hProduct: *mut u32  // MSIHANDLE* out
    ) -> u32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("msi.dll", CharSet = CharSet.Unicode)]
public static extern uint MsiOpenPackageW([MarshalAs(UnmanagedType.LPWStr)] string szPackagePath, out uint hProduct);
"@
$api = Add-Type -MemberDefinition $sig -Name 'msi_MsiOpenPackageW' -Namespace Win32 -PassThru
# $api::MsiOpenPackageW(szPackagePath, hProduct)

#uselib "msi.dll"
#func global MsiOpenPackageW "MsiOpenPackageW" wptr, wptr
; MsiOpenPackageW szPackagePath, hProduct   ; 戻り値は stat
; szPackagePath : LPCWSTR -> "wptr"
; hProduct : MSIHANDLE* out -> "wptr"
; ※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 "msi.dll"
#cfunc global MsiOpenPackageW "MsiOpenPackageW" wstr, int
; res = MsiOpenPackageW(szPackagePath, hProduct)
; szPackagePath : LPCWSTR -> "wstr"
; hProduct : MSIHANDLE* out -> "int"

; DWORD MsiOpenPackageW(LPCWSTR szPackagePath, MSIHANDLE* hProduct)
#uselib "msi.dll"
#cfunc global MsiOpenPackageW "MsiOpenPackageW" wstr, int
; res = MsiOpenPackageW(szPackagePath, hProduct)
; szPackagePath : LPCWSTR -> "wstr"
; hProduct : MSIHANDLE* out -> "int"

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

var (
	msi = windows.NewLazySystemDLL("msi.dll")
	procMsiOpenPackageW = msi.NewProc("MsiOpenPackageW")
)

// szPackagePath (LPCWSTR), hProduct (MSIHANDLE* out)
r1, _, err := procMsiOpenPackageW.Call(
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(szPackagePath))),
	uintptr(hProduct),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // DWORD

function MsiOpenPackageW(
  szPackagePath: PWideChar;   // LPCWSTR
  hProduct: Pointer   // MSIHANDLE* out
): DWORD; stdcall;
  external 'msi.dll' name 'MsiOpenPackageW';

result := DllCall("msi\MsiOpenPackageW"
    , "WStr", szPackagePath   ; LPCWSTR
    , "Ptr", hProduct   ; MSIHANDLE* out
    , "UInt")   ; return: DWORD

●MsiOpenPackageW(szPackagePath, hProduct) = DLL("msi.dll", "dword MsiOpenPackageW(char*, void*)")
# 呼び出し: MsiOpenPackageW(szPackagePath, hProduct)
# szPackagePath : LPCWSTR -> "char*"
# hProduct : MSIHANDLE* 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)。
# ※-W(Unicode)関数。なでしこ1はANSIのため -A 版の利用を推奨。