DecryptFileW

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

BOOL DecryptFileW(
    LPCWSTR lpFileName,
    DWORD dwReserved   // optional
);

<DllImport("ADVAPI32.dll", CharSet:=CharSet.Unicode, SetLastError:=True, ExactSpelling:=True)>
Public Shared Function DecryptFileW(
    <MarshalAs(UnmanagedType.LPWStr)> lpFileName As String,   ' LPCWSTR
    dwReserved As UInteger   ' DWORD optional
) As Boolean
End Function

' lpFileName : LPCWSTR
' dwReserved : DWORD optional
Declare PtrSafe Function DecryptFileW Lib "advapi32" ( _
    ByVal lpFileName As LongPtr, _
    ByVal dwReserved 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

DecryptFileW = ctypes.windll.advapi32.DecryptFileW
DecryptFileW.restype = wintypes.BOOL
DecryptFileW.argtypes = [
    wintypes.LPCWSTR,  # lpFileName : LPCWSTR
    wintypes.DWORD,  # dwReserved : DWORD optional
]
# GetLastError: use ctypes.GetLastError() (or ctypes.WinDLL(use_last_error=True))

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('ADVAPI32.dll')
DecryptFileW = Fiddle::Function.new(
  lib['DecryptFileW'],
  [
    Fiddle::TYPE_VOIDP,  # lpFileName : LPCWSTR
    -Fiddle::TYPE_INT,  # dwReserved : DWORD optional
  ],
  Fiddle::TYPE_INT)
# Wide strings: pass str.encode("UTF-16LE") + "\x00\x00"

#[link(name = "advapi32")]
extern "system" {
    fn DecryptFileW(
        lpFileName: *const u16,  // LPCWSTR
        dwReserved: u32  // DWORD optional
    ) -> i32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[return: MarshalAs(UnmanagedType.Bool)]
[DllImport("ADVAPI32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
public static extern bool DecryptFileW([MarshalAs(UnmanagedType.LPWStr)] string lpFileName, uint dwReserved);
"@
$api = Add-Type -MemberDefinition $sig -Name 'ADVAPI32_DecryptFileW' -Namespace Win32 -PassThru
# $api::DecryptFileW(lpFileName, dwReserved)

#uselib "ADVAPI32.dll"
#func global DecryptFileW "DecryptFileW" wptr, wptr
; DecryptFileW lpFileName, dwReserved   ; 戻り値は stat
; lpFileName : LPCWSTR -> "wptr"
; dwReserved : DWORD optional -> "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 DecryptFileW "DecryptFileW" wstr, int
; res = DecryptFileW(lpFileName, dwReserved)
; lpFileName : LPCWSTR -> "wstr"
; dwReserved : DWORD optional -> "int"

; BOOL DecryptFileW(LPCWSTR lpFileName, DWORD dwReserved)
#uselib "ADVAPI32.dll"
#cfunc global DecryptFileW "DecryptFileW" wstr, int
; res = DecryptFileW(lpFileName, dwReserved)
; lpFileName : LPCWSTR -> "wstr"
; dwReserved : DWORD optional -> "int"

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

var (
	advapi32 = windows.NewLazySystemDLL("ADVAPI32.dll")
	procDecryptFileW = advapi32.NewProc("DecryptFileW")
)

// lpFileName (LPCWSTR), dwReserved (DWORD optional)
r1, _, err := procDecryptFileW.Call(
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(lpFileName))),
	uintptr(dwReserved),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // BOOL

function DecryptFileW(
  lpFileName: PWideChar;   // LPCWSTR
  dwReserved: DWORD   // DWORD optional
): BOOL; stdcall;
  external 'ADVAPI32.dll' name 'DecryptFileW';

result := DllCall("ADVAPI32\DecryptFileW"
    , "WStr", lpFileName   ; LPCWSTR
    , "UInt", dwReserved   ; DWORD optional
    , "Int")   ; return: BOOL

●DecryptFileW(lpFileName, dwReserved) = DLL("ADVAPI32.dll", "bool DecryptFileW(char*, dword)")
# 呼び出し: DecryptFileW(lpFileName, dwReserved)
# lpFileName : LPCWSTR -> "char*"
# dwReserved : DWORD optional -> "dword"
# 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。