PathCommonPrefixW

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

INT PathCommonPrefixW(
    LPCWSTR pszFile1,
    LPCWSTR pszFile2,
    LPWSTR achPath   // optional
);

<DllImport("SHLWAPI.dll", CharSet:=CharSet.Unicode, ExactSpelling:=True)>
Public Shared Function PathCommonPrefixW(
    <MarshalAs(UnmanagedType.LPWStr)> pszFile1 As String,   ' LPCWSTR
    <MarshalAs(UnmanagedType.LPWStr)> pszFile2 As String,   ' LPCWSTR
    <MarshalAs(UnmanagedType.LPWStr)> achPath As System.Text.StringBuilder   ' LPWSTR optional, out
) As Integer
End Function

' pszFile1 : LPCWSTR
' pszFile2 : LPCWSTR
' achPath : LPWSTR optional, out
Declare PtrSafe Function PathCommonPrefixW Lib "shlwapi" ( _
    ByVal pszFile1 As LongPtr, _
    ByVal pszFile2 As LongPtr, _
    ByVal achPath 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

PathCommonPrefixW = ctypes.windll.shlwapi.PathCommonPrefixW
PathCommonPrefixW.restype = ctypes.c_int
PathCommonPrefixW.argtypes = [
    wintypes.LPCWSTR,  # pszFile1 : LPCWSTR
    wintypes.LPCWSTR,  # pszFile2 : LPCWSTR
    wintypes.LPWSTR,  # achPath : LPWSTR optional, out
]

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('SHLWAPI.dll')
PathCommonPrefixW = Fiddle::Function.new(
  lib['PathCommonPrefixW'],
  [
    Fiddle::TYPE_VOIDP,  # pszFile1 : LPCWSTR
    Fiddle::TYPE_VOIDP,  # pszFile2 : LPCWSTR
    Fiddle::TYPE_VOIDP,  # achPath : LPWSTR optional, out
  ],
  Fiddle::TYPE_INT)
# Wide strings: pass str.encode("UTF-16LE") + "\x00\x00"

#[link(name = "shlwapi")]
extern "system" {
    fn PathCommonPrefixW(
        pszFile1: *const u16,  // LPCWSTR
        pszFile2: *const u16,  // LPCWSTR
        achPath: *mut u16  // LPWSTR optional, out
    ) -> i32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("SHLWAPI.dll", CharSet = CharSet.Unicode)]
public static extern int PathCommonPrefixW([MarshalAs(UnmanagedType.LPWStr)] string pszFile1, [MarshalAs(UnmanagedType.LPWStr)] string pszFile2, [MarshalAs(UnmanagedType.LPWStr)] System.Text.StringBuilder achPath);
"@
$api = Add-Type -MemberDefinition $sig -Name 'SHLWAPI_PathCommonPrefixW' -Namespace Win32 -PassThru
# $api::PathCommonPrefixW(pszFile1, pszFile2, achPath)

#uselib "SHLWAPI.dll"
#func global PathCommonPrefixW "PathCommonPrefixW" wptr, wptr, wptr
; PathCommonPrefixW pszFile1, pszFile2, varptr(achPath)   ; 戻り値は stat
; pszFile1 : LPCWSTR -> "wptr"
; pszFile2 : LPCWSTR -> "wptr"
; achPath : LPWSTR optional, 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 "SHLWAPI.dll"
#cfunc global PathCommonPrefixW "PathCommonPrefixW" wstr, wstr, var
; res = PathCommonPrefixW(pszFile1, pszFile2, achPath)
; pszFile1 : LPCWSTR -> "wstr"
; pszFile2 : LPCWSTR -> "wstr"
; achPath : LPWSTR optional, 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。

; INT PathCommonPrefixW(LPCWSTR pszFile1, LPCWSTR pszFile2, LPWSTR achPath)
#uselib "SHLWAPI.dll"
#cfunc global PathCommonPrefixW "PathCommonPrefixW" wstr, wstr, var
; res = PathCommonPrefixW(pszFile1, pszFile2, achPath)
; pszFile1 : LPCWSTR -> "wstr"
; pszFile2 : LPCWSTR -> "wstr"
; achPath : LPWSTR optional, 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 (
	shlwapi = windows.NewLazySystemDLL("SHLWAPI.dll")
	procPathCommonPrefixW = shlwapi.NewProc("PathCommonPrefixW")
)

// pszFile1 (LPCWSTR), pszFile2 (LPCWSTR), achPath (LPWSTR optional, out)
r1, _, err := procPathCommonPrefixW.Call(
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(pszFile1))),
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(pszFile2))),
	uintptr(achPath),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // INT

function PathCommonPrefixW(
  pszFile1: PWideChar;   // LPCWSTR
  pszFile2: PWideChar;   // LPCWSTR
  achPath: PWideChar   // LPWSTR optional, out
): Integer; stdcall;
  external 'SHLWAPI.dll' name 'PathCommonPrefixW';

result := DllCall("SHLWAPI\PathCommonPrefixW"
    , "WStr", pszFile1   ; LPCWSTR
    , "WStr", pszFile2   ; LPCWSTR
    , "Ptr", achPath   ; LPWSTR optional, out
    , "Int")   ; return: INT

●PathCommonPrefixW(pszFile1, pszFile2, achPath) = DLL("SHLWAPI.dll", "int PathCommonPrefixW(char*, char*, char*)")
# 呼び出し: PathCommonPrefixW(pszFile1, pszFile2, achPath)
# pszFile1 : LPCWSTR -> "char*"
# pszFile2 : LPCWSTR -> "char*"
# achPath : LPWSTR optional, 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。