MsiEnumClientsW

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

DWORD MsiEnumClientsW(
    LPCWSTR szComponent,
    DWORD iProductIndex,
    LPWSTR lpProductBuf
);

<DllImport("msi.dll", CharSet:=CharSet.Unicode, ExactSpelling:=True)>
Public Shared Function MsiEnumClientsW(
    <MarshalAs(UnmanagedType.LPWStr)> szComponent As String,   ' LPCWSTR
    iProductIndex As UInteger,   ' DWORD
    <MarshalAs(UnmanagedType.LPWStr)> lpProductBuf As System.Text.StringBuilder   ' LPWSTR out
) As UInteger
End Function

' szComponent : LPCWSTR
' iProductIndex : DWORD
' lpProductBuf : LPWSTR out
Declare PtrSafe Function MsiEnumClientsW Lib "msi" ( _
    ByVal szComponent As LongPtr, _
    ByVal iProductIndex As Long, _
    ByVal lpProductBuf As LongPtr) 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

MsiEnumClientsW = ctypes.windll.msi.MsiEnumClientsW
MsiEnumClientsW.restype = wintypes.DWORD
MsiEnumClientsW.argtypes = [
    wintypes.LPCWSTR,  # szComponent : LPCWSTR
    wintypes.DWORD,  # iProductIndex : DWORD
    wintypes.LPWSTR,  # lpProductBuf : LPWSTR out
]

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('msi.dll')
MsiEnumClientsW = Fiddle::Function.new(
  lib['MsiEnumClientsW'],
  [
    Fiddle::TYPE_VOIDP,  # szComponent : LPCWSTR
    -Fiddle::TYPE_INT,  # iProductIndex : DWORD
    Fiddle::TYPE_VOIDP,  # lpProductBuf : LPWSTR out
  ],
  -Fiddle::TYPE_INT)
# Wide strings: pass str.encode("UTF-16LE") + "\x00\x00"

#[link(name = "msi")]
extern "system" {
    fn MsiEnumClientsW(
        szComponent: *const u16,  // LPCWSTR
        iProductIndex: u32,  // DWORD
        lpProductBuf: *mut u16  // LPWSTR out
    ) -> u32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("msi.dll", CharSet = CharSet.Unicode)]
public static extern uint MsiEnumClientsW([MarshalAs(UnmanagedType.LPWStr)] string szComponent, uint iProductIndex, [MarshalAs(UnmanagedType.LPWStr)] System.Text.StringBuilder lpProductBuf);
"@
$api = Add-Type -MemberDefinition $sig -Name 'msi_MsiEnumClientsW' -Namespace Win32 -PassThru
# $api::MsiEnumClientsW(szComponent, iProductIndex, lpProductBuf)

#uselib "msi.dll"
#func global MsiEnumClientsW "MsiEnumClientsW" wptr, wptr, wptr
; MsiEnumClientsW szComponent, iProductIndex, varptr(lpProductBuf)   ; 戻り値は stat
; szComponent : LPCWSTR -> "wptr"
; iProductIndex : DWORD -> "wptr"
; lpProductBuf : LPWSTR 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 MsiEnumClientsW "MsiEnumClientsW" wstr, int, var
; res = MsiEnumClientsW(szComponent, iProductIndex, lpProductBuf)
; szComponent : LPCWSTR -> "wstr"
; iProductIndex : DWORD -> "int"
; lpProductBuf : LPWSTR out -> "var"
; ※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。

; DWORD MsiEnumClientsW(LPCWSTR szComponent, DWORD iProductIndex, LPWSTR lpProductBuf)
#uselib "msi.dll"
#cfunc global MsiEnumClientsW "MsiEnumClientsW" wstr, int, var
; res = MsiEnumClientsW(szComponent, iProductIndex, lpProductBuf)
; szComponent : LPCWSTR -> "wstr"
; iProductIndex : DWORD -> "int"
; lpProductBuf : LPWSTR out -> "var"
; ※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 (
	msi = windows.NewLazySystemDLL("msi.dll")
	procMsiEnumClientsW = msi.NewProc("MsiEnumClientsW")
)

// szComponent (LPCWSTR), iProductIndex (DWORD), lpProductBuf (LPWSTR out)
r1, _, err := procMsiEnumClientsW.Call(
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(szComponent))),
	uintptr(iProductIndex),
	uintptr(lpProductBuf),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // DWORD

function MsiEnumClientsW(
  szComponent: PWideChar;   // LPCWSTR
  iProductIndex: DWORD;   // DWORD
  lpProductBuf: PWideChar   // LPWSTR out
): DWORD; stdcall;
  external 'msi.dll' name 'MsiEnumClientsW';

result := DllCall("msi\MsiEnumClientsW"
    , "WStr", szComponent   ; LPCWSTR
    , "UInt", iProductIndex   ; DWORD
    , "Ptr", lpProductBuf   ; LPWSTR out
    , "UInt")   ; return: DWORD

●MsiEnumClientsW(szComponent, iProductIndex, lpProductBuf) = DLL("msi.dll", "dword MsiEnumClientsW(char*, dword, char*)")
# 呼び出し: MsiEnumClientsW(szComponent, iProductIndex, lpProductBuf)
# szComponent : LPCWSTR -> "char*"
# iProductIndex : DWORD -> "dword"
# lpProductBuf : LPWSTR out -> "char*"
# 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。