RegOpenKeyExW

// ADVAPI32.dll  (Unicode / -W)
#include <windows.h>

WIN32_ERROR RegOpenKeyExW(
    HKEY hKey,
    LPCWSTR lpSubKey,   // optional
    DWORD ulOptions,   // optional
    REG_SAM_FLAGS samDesired,
    HKEY* phkResult
);

<DllImport("ADVAPI32.dll", CharSet:=CharSet.Unicode, ExactSpelling:=True)>
Public Shared Function RegOpenKeyExW(
    hKey As IntPtr,   ' HKEY
    <MarshalAs(UnmanagedType.LPWStr)> lpSubKey As String,   ' LPCWSTR optional
    ulOptions As UInteger,   ' DWORD optional
    samDesired As UInteger,   ' REG_SAM_FLAGS
    phkResult As IntPtr   ' HKEY* out
) As UInteger
End Function

' hKey : HKEY
' lpSubKey : LPCWSTR optional
' ulOptions : DWORD optional
' samDesired : REG_SAM_FLAGS
' phkResult : HKEY* out
Declare PtrSafe Function RegOpenKeyExW Lib "advapi32" ( _
    ByVal hKey As LongPtr, _
    ByVal lpSubKey As LongPtr, _
    ByVal ulOptions As Long, _
    ByVal samDesired As Long, _
    ByVal phkResult 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

RegOpenKeyExW = ctypes.windll.advapi32.RegOpenKeyExW
RegOpenKeyExW.restype = wintypes.DWORD
RegOpenKeyExW.argtypes = [
    wintypes.HANDLE,  # hKey : HKEY
    wintypes.LPCWSTR,  # lpSubKey : LPCWSTR optional
    wintypes.DWORD,  # ulOptions : DWORD optional
    wintypes.DWORD,  # samDesired : REG_SAM_FLAGS
    ctypes.c_void_p,  # phkResult : HKEY* out
]

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('ADVAPI32.dll')
RegOpenKeyExW = Fiddle::Function.new(
  lib['RegOpenKeyExW'],
  [
    Fiddle::TYPE_VOIDP,  # hKey : HKEY
    Fiddle::TYPE_VOIDP,  # lpSubKey : LPCWSTR optional
    -Fiddle::TYPE_INT,  # ulOptions : DWORD optional
    -Fiddle::TYPE_INT,  # samDesired : REG_SAM_FLAGS
    Fiddle::TYPE_VOIDP,  # phkResult : HKEY* out
  ],
  -Fiddle::TYPE_INT)
# Wide strings: pass str.encode("UTF-16LE") + "\x00\x00"

#[link(name = "advapi32")]
extern "system" {
    fn RegOpenKeyExW(
        hKey: *mut core::ffi::c_void,  // HKEY
        lpSubKey: *const u16,  // LPCWSTR optional
        ulOptions: u32,  // DWORD optional
        samDesired: u32,  // REG_SAM_FLAGS
        phkResult: *mut *mut core::ffi::c_void  // HKEY* out
    ) -> u32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("ADVAPI32.dll", CharSet = CharSet.Unicode)]
public static extern uint RegOpenKeyExW(IntPtr hKey, [MarshalAs(UnmanagedType.LPWStr)] string lpSubKey, uint ulOptions, uint samDesired, IntPtr phkResult);
"@
$api = Add-Type -MemberDefinition $sig -Name 'ADVAPI32_RegOpenKeyExW' -Namespace Win32 -PassThru
# $api::RegOpenKeyExW(hKey, lpSubKey, ulOptions, samDesired, phkResult)

#uselib "ADVAPI32.dll"
#func global RegOpenKeyExW "RegOpenKeyExW" wptr, wptr, wptr, wptr, wptr
; RegOpenKeyExW hKey, lpSubKey, ulOptions, samDesired, phkResult   ; 戻り値は stat
; hKey : HKEY -> "wptr"
; lpSubKey : LPCWSTR optional -> "wptr"
; ulOptions : DWORD optional -> "wptr"
; samDesired : REG_SAM_FLAGS -> "wptr"
; phkResult : HKEY* 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 "ADVAPI32.dll"
#cfunc global RegOpenKeyExW "RegOpenKeyExW" sptr, wstr, int, int, sptr
; res = RegOpenKeyExW(hKey, lpSubKey, ulOptions, samDesired, phkResult)
; hKey : HKEY -> "sptr"
; lpSubKey : LPCWSTR optional -> "wstr"
; ulOptions : DWORD optional -> "int"
; samDesired : REG_SAM_FLAGS -> "int"
; phkResult : HKEY* out -> "sptr"

; WIN32_ERROR RegOpenKeyExW(HKEY hKey, LPCWSTR lpSubKey, DWORD ulOptions, REG_SAM_FLAGS samDesired, HKEY* phkResult)
#uselib "ADVAPI32.dll"
#cfunc global RegOpenKeyExW "RegOpenKeyExW" intptr, wstr, int, int, intptr
; res = RegOpenKeyExW(hKey, lpSubKey, ulOptions, samDesired, phkResult)
; hKey : HKEY -> "intptr"
; lpSubKey : LPCWSTR optional -> "wstr"
; ulOptions : DWORD optional -> "int"
; samDesired : REG_SAM_FLAGS -> "int"
; phkResult : HKEY* out -> "intptr"

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

var (
	advapi32 = windows.NewLazySystemDLL("ADVAPI32.dll")
	procRegOpenKeyExW = advapi32.NewProc("RegOpenKeyExW")
)

// hKey (HKEY), lpSubKey (LPCWSTR optional), ulOptions (DWORD optional), samDesired (REG_SAM_FLAGS), phkResult (HKEY* out)
r1, _, err := procRegOpenKeyExW.Call(
	uintptr(hKey),
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(lpSubKey))),
	uintptr(ulOptions),
	uintptr(samDesired),
	uintptr(phkResult),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // WIN32_ERROR

function RegOpenKeyExW(
  hKey: THandle;   // HKEY
  lpSubKey: PWideChar;   // LPCWSTR optional
  ulOptions: DWORD;   // DWORD optional
  samDesired: DWORD;   // REG_SAM_FLAGS
  phkResult: Pointer   // HKEY* out
): DWORD; stdcall;
  external 'ADVAPI32.dll' name 'RegOpenKeyExW';

result := DllCall("ADVAPI32\RegOpenKeyExW"
    , "Ptr", hKey   ; HKEY
    , "WStr", lpSubKey   ; LPCWSTR optional
    , "UInt", ulOptions   ; DWORD optional
    , "UInt", samDesired   ; REG_SAM_FLAGS
    , "Ptr", phkResult   ; HKEY* out
    , "UInt")   ; return: WIN32_ERROR

●RegOpenKeyExW(hKey, lpSubKey, ulOptions, samDesired, phkResult) = DLL("ADVAPI32.dll", "dword RegOpenKeyExW(void*, char*, dword, dword, void*)")
# 呼び出し: RegOpenKeyExW(hKey, lpSubKey, ulOptions, samDesired, phkResult)
# hKey : HKEY -> "void*"
# lpSubKey : LPCWSTR optional -> "char*"
# ulOptions : DWORD optional -> "dword"
# samDesired : REG_SAM_FLAGS -> "dword"
# phkResult : HKEY* 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。