CharToOemW

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

BOOL CharToOemW(
    LPCWSTR pSrc,
    LPSTR pDst
);

<DllImport("USER32.dll", CharSet:=CharSet.Unicode, SetLastError:=True, ExactSpelling:=True)>
Public Shared Function CharToOemW(
    <MarshalAs(UnmanagedType.LPWStr)> pSrc As String,   ' LPCWSTR
    <MarshalAs(UnmanagedType.LPStr)> pDst As System.Text.StringBuilder   ' LPSTR out
) As Boolean
End Function

' pSrc : LPCWSTR
' pDst : LPSTR out
Declare PtrSafe Function CharToOemW Lib "user32" ( _
    ByVal pSrc As LongPtr, _
    ByVal pDst As String) 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

CharToOemW = ctypes.windll.user32.CharToOemW
CharToOemW.restype = wintypes.BOOL
CharToOemW.argtypes = [
    wintypes.LPCWSTR,  # pSrc : LPCWSTR
    wintypes.LPSTR,  # pDst : LPSTR out
]
# GetLastError: use ctypes.GetLastError() (or ctypes.WinDLL(use_last_error=True))

require 'fiddle'
require 'fiddle/import'

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

#[link(name = "user32")]
extern "system" {
    fn CharToOemW(
        pSrc: *const u16,  // LPCWSTR
        pDst: *mut u8  // LPSTR out
    ) -> 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 CharToOemW([MarshalAs(UnmanagedType.LPWStr)] string pSrc, [MarshalAs(UnmanagedType.LPStr)] System.Text.StringBuilder pDst);
"@
$api = Add-Type -MemberDefinition $sig -Name 'USER32_CharToOemW' -Namespace Win32 -PassThru
# $api::CharToOemW(pSrc, pDst)

#uselib "USER32.dll"
#func global CharToOemW "CharToOemW" wptr, wptr
; CharToOemW pSrc, varptr(pDst)   ; 戻り値は stat
; pSrc : LPCWSTR -> "wptr"
; pDst : LPSTR 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 "USER32.dll"
#cfunc global CharToOemW "CharToOemW" wstr, var
; res = CharToOemW(pSrc, pDst)
; pSrc : LPCWSTR -> "wstr"
; pDst : LPSTR 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。

; BOOL CharToOemW(LPCWSTR pSrc, LPSTR pDst)
#uselib "USER32.dll"
#cfunc global CharToOemW "CharToOemW" wstr, var
; res = CharToOemW(pSrc, pDst)
; pSrc : LPCWSTR -> "wstr"
; pDst : LPSTR 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 (
	user32 = windows.NewLazySystemDLL("USER32.dll")
	procCharToOemW = user32.NewProc("CharToOemW")
)

// pSrc (LPCWSTR), pDst (LPSTR out)
r1, _, err := procCharToOemW.Call(
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(pSrc))),
	uintptr(pDst),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // BOOL

function CharToOemW(
  pSrc: PWideChar;   // LPCWSTR
  pDst: PAnsiChar   // LPSTR out
): BOOL; stdcall;
  external 'USER32.dll' name 'CharToOemW';

result := DllCall("USER32\CharToOemW"
    , "WStr", pSrc   ; LPCWSTR
    , "Ptr", pDst   ; LPSTR out
    , "Int")   ; return: BOOL

●CharToOemW(pSrc, pDst) = DLL("USER32.dll", "bool CharToOemW(char*, char*)")
# 呼び出し: CharToOemW(pSrc, pDst)
# pSrc : LPCWSTR -> "char*"
# pDst : LPSTR 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。