CharToOemBuffW

// USER32.dll  (Unicode / -W)
#include <windows.h>

BOOL CharToOemBuffW(
    LPCWSTR lpszSrc,
    LPSTR lpszDst,
    DWORD cchDstLength
);

<DllImport("USER32.dll", CharSet:=CharSet.Unicode, SetLastError:=True, ExactSpelling:=True)>
Public Shared Function CharToOemBuffW(
    <MarshalAs(UnmanagedType.LPWStr)> lpszSrc As String,   ' LPCWSTR
    <MarshalAs(UnmanagedType.LPStr)> lpszDst As System.Text.StringBuilder,   ' LPSTR out
    cchDstLength As UInteger   ' DWORD
) As Boolean
End Function

' lpszSrc : LPCWSTR
' lpszDst : LPSTR out
' cchDstLength : DWORD
Declare PtrSafe Function CharToOemBuffW Lib "user32" ( _
    ByVal lpszSrc As LongPtr, _
    ByVal lpszDst As String, _
    ByVal cchDstLength 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

CharToOemBuffW = ctypes.windll.user32.CharToOemBuffW
CharToOemBuffW.restype = wintypes.BOOL
CharToOemBuffW.argtypes = [
    wintypes.LPCWSTR,  # lpszSrc : LPCWSTR
    wintypes.LPSTR,  # lpszDst : LPSTR out
    wintypes.DWORD,  # cchDstLength : DWORD
]
# GetLastError: use ctypes.GetLastError() (or ctypes.WinDLL(use_last_error=True))

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('USER32.dll')
CharToOemBuffW = Fiddle::Function.new(
  lib['CharToOemBuffW'],
  [
    Fiddle::TYPE_VOIDP,  # lpszSrc : LPCWSTR
    Fiddle::TYPE_VOIDP,  # lpszDst : LPSTR out
    -Fiddle::TYPE_INT,  # cchDstLength : DWORD
  ],
  Fiddle::TYPE_INT)
# Wide strings: pass str.encode("UTF-16LE") + "\x00\x00"

#[link(name = "user32")]
extern "system" {
    fn CharToOemBuffW(
        lpszSrc: *const u16,  // LPCWSTR
        lpszDst: *mut u8,  // LPSTR out
        cchDstLength: u32  // DWORD
    ) -> i32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[return: MarshalAs(UnmanagedType.Bool)]
[DllImport("USER32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
public static extern bool CharToOemBuffW([MarshalAs(UnmanagedType.LPWStr)] string lpszSrc, [MarshalAs(UnmanagedType.LPStr)] System.Text.StringBuilder lpszDst, uint cchDstLength);
"@
$api = Add-Type -MemberDefinition $sig -Name 'USER32_CharToOemBuffW' -Namespace Win32 -PassThru
# $api::CharToOemBuffW(lpszSrc, lpszDst, cchDstLength)

#uselib "USER32.dll"
#func global CharToOemBuffW "CharToOemBuffW" wptr, wptr, wptr
; CharToOemBuffW lpszSrc, varptr(lpszDst), cchDstLength   ; 戻り値は stat
; lpszSrc : LPCWSTR -> "wptr"
; lpszDst : LPSTR out -> "wptr"
; cchDstLength : DWORD -> "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 "USER32.dll"
#cfunc global CharToOemBuffW "CharToOemBuffW" wstr, var, int
; res = CharToOemBuffW(lpszSrc, lpszDst, cchDstLength)
; lpszSrc : LPCWSTR -> "wstr"
; lpszDst : LPSTR out -> "var"
; cchDstLength : DWORD -> "int"
; ※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。

; BOOL CharToOemBuffW(LPCWSTR lpszSrc, LPSTR lpszDst, DWORD cchDstLength)
#uselib "USER32.dll"
#cfunc global CharToOemBuffW "CharToOemBuffW" wstr, var, int
; res = CharToOemBuffW(lpszSrc, lpszDst, cchDstLength)
; lpszSrc : LPCWSTR -> "wstr"
; lpszDst : LPSTR out -> "var"
; cchDstLength : DWORD -> "int"
; ※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 (
	user32 = windows.NewLazySystemDLL("USER32.dll")
	procCharToOemBuffW = user32.NewProc("CharToOemBuffW")
)

// lpszSrc (LPCWSTR), lpszDst (LPSTR out), cchDstLength (DWORD)
r1, _, err := procCharToOemBuffW.Call(
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(lpszSrc))),
	uintptr(lpszDst),
	uintptr(cchDstLength),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // BOOL

function CharToOemBuffW(
  lpszSrc: PWideChar;   // LPCWSTR
  lpszDst: PAnsiChar;   // LPSTR out
  cchDstLength: DWORD   // DWORD
): BOOL; stdcall;
  external 'USER32.dll' name 'CharToOemBuffW';

result := DllCall("USER32\CharToOemBuffW"
    , "WStr", lpszSrc   ; LPCWSTR
    , "Ptr", lpszDst   ; LPSTR out
    , "UInt", cchDstLength   ; DWORD
    , "Int")   ; return: BOOL

●CharToOemBuffW(lpszSrc, lpszDst, cchDstLength) = DLL("USER32.dll", "bool CharToOemBuffW(char*, char*, dword)")
# 呼び出し: CharToOemBuffW(lpszSrc, lpszDst, cchDstLength)
# lpszSrc : LPCWSTR -> "char*"
# lpszDst : LPSTR out -> "char*"
# cchDstLength : DWORD -> "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。