InternetCombineUrlW

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

BOOL InternetCombineUrlW(
    LPCWSTR lpszBaseUrl,
    LPCWSTR lpszRelativeUrl,
    LPWSTR lpszBuffer,
    DWORD* lpdwBufferLength,
    DWORD dwFlags
);

<DllImport("WININET.dll", CharSet:=CharSet.Unicode, SetLastError:=True, ExactSpelling:=True)>
Public Shared Function InternetCombineUrlW(
    <MarshalAs(UnmanagedType.LPWStr)> lpszBaseUrl As String,   ' LPCWSTR
    <MarshalAs(UnmanagedType.LPWStr)> lpszRelativeUrl As String,   ' LPCWSTR
    <MarshalAs(UnmanagedType.LPWStr)> lpszBuffer As System.Text.StringBuilder,   ' LPWSTR out
    ByRef lpdwBufferLength As UInteger,   ' DWORD* in/out
    dwFlags As UInteger   ' DWORD
) As Boolean
End Function

' lpszBaseUrl : LPCWSTR
' lpszRelativeUrl : LPCWSTR
' lpszBuffer : LPWSTR out
' lpdwBufferLength : DWORD* in/out
' dwFlags : DWORD
Declare PtrSafe Function InternetCombineUrlW Lib "wininet" ( _
    ByVal lpszBaseUrl As LongPtr, _
    ByVal lpszRelativeUrl As LongPtr, _
    ByVal lpszBuffer As LongPtr, _
    ByRef lpdwBufferLength As Long, _
    ByVal dwFlags 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

InternetCombineUrlW = ctypes.windll.wininet.InternetCombineUrlW
InternetCombineUrlW.restype = wintypes.BOOL
InternetCombineUrlW.argtypes = [
    wintypes.LPCWSTR,  # lpszBaseUrl : LPCWSTR
    wintypes.LPCWSTR,  # lpszRelativeUrl : LPCWSTR
    wintypes.LPWSTR,  # lpszBuffer : LPWSTR out
    ctypes.POINTER(wintypes.DWORD),  # lpdwBufferLength : DWORD* in/out
    wintypes.DWORD,  # dwFlags : DWORD
]
# GetLastError: use ctypes.GetLastError() (or ctypes.WinDLL(use_last_error=True))

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('WININET.dll')
InternetCombineUrlW = Fiddle::Function.new(
  lib['InternetCombineUrlW'],
  [
    Fiddle::TYPE_VOIDP,  # lpszBaseUrl : LPCWSTR
    Fiddle::TYPE_VOIDP,  # lpszRelativeUrl : LPCWSTR
    Fiddle::TYPE_VOIDP,  # lpszBuffer : LPWSTR out
    Fiddle::TYPE_VOIDP,  # lpdwBufferLength : DWORD* in/out
    -Fiddle::TYPE_INT,  # dwFlags : DWORD
  ],
  Fiddle::TYPE_INT)
# Wide strings: pass str.encode("UTF-16LE") + "\x00\x00"

#[link(name = "wininet")]
extern "system" {
    fn InternetCombineUrlW(
        lpszBaseUrl: *const u16,  // LPCWSTR
        lpszRelativeUrl: *const u16,  // LPCWSTR
        lpszBuffer: *mut u16,  // LPWSTR out
        lpdwBufferLength: *mut u32,  // DWORD* in/out
        dwFlags: u32  // DWORD
    ) -> i32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[return: MarshalAs(UnmanagedType.Bool)]
[DllImport("WININET.dll", CharSet = CharSet.Unicode, SetLastError = true)]
public static extern bool InternetCombineUrlW([MarshalAs(UnmanagedType.LPWStr)] string lpszBaseUrl, [MarshalAs(UnmanagedType.LPWStr)] string lpszRelativeUrl, [MarshalAs(UnmanagedType.LPWStr)] System.Text.StringBuilder lpszBuffer, ref uint lpdwBufferLength, uint dwFlags);
"@
$api = Add-Type -MemberDefinition $sig -Name 'WININET_InternetCombineUrlW' -Namespace Win32 -PassThru
# $api::InternetCombineUrlW(lpszBaseUrl, lpszRelativeUrl, lpszBuffer, lpdwBufferLength, dwFlags)

#uselib "WININET.dll"
#func global InternetCombineUrlW "InternetCombineUrlW" wptr, wptr, wptr, wptr, wptr
; InternetCombineUrlW lpszBaseUrl, lpszRelativeUrl, varptr(lpszBuffer), varptr(lpdwBufferLength), dwFlags   ; 戻り値は stat
; lpszBaseUrl : LPCWSTR -> "wptr"
; lpszRelativeUrl : LPCWSTR -> "wptr"
; lpszBuffer : LPWSTR out -> "wptr"
; lpdwBufferLength : DWORD* in/out -> "wptr"
; dwFlags : 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 "WININET.dll"
#cfunc global InternetCombineUrlW "InternetCombineUrlW" wstr, wstr, var, var, int
; res = InternetCombineUrlW(lpszBaseUrl, lpszRelativeUrl, lpszBuffer, lpdwBufferLength, dwFlags)
; lpszBaseUrl : LPCWSTR -> "wstr"
; lpszRelativeUrl : LPCWSTR -> "wstr"
; lpszBuffer : LPWSTR out -> "var"
; lpdwBufferLength : DWORD* in/out -> "var"
; dwFlags : 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 InternetCombineUrlW(LPCWSTR lpszBaseUrl, LPCWSTR lpszRelativeUrl, LPWSTR lpszBuffer, DWORD* lpdwBufferLength, DWORD dwFlags)
#uselib "WININET.dll"
#cfunc global InternetCombineUrlW "InternetCombineUrlW" wstr, wstr, var, var, int
; res = InternetCombineUrlW(lpszBaseUrl, lpszRelativeUrl, lpszBuffer, lpdwBufferLength, dwFlags)
; lpszBaseUrl : LPCWSTR -> "wstr"
; lpszRelativeUrl : LPCWSTR -> "wstr"
; lpszBuffer : LPWSTR out -> "var"
; lpdwBufferLength : DWORD* in/out -> "var"
; dwFlags : 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 (
	wininet = windows.NewLazySystemDLL("WININET.dll")
	procInternetCombineUrlW = wininet.NewProc("InternetCombineUrlW")
)

// lpszBaseUrl (LPCWSTR), lpszRelativeUrl (LPCWSTR), lpszBuffer (LPWSTR out), lpdwBufferLength (DWORD* in/out), dwFlags (DWORD)
r1, _, err := procInternetCombineUrlW.Call(
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(lpszBaseUrl))),
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(lpszRelativeUrl))),
	uintptr(lpszBuffer),
	uintptr(lpdwBufferLength),
	uintptr(dwFlags),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // BOOL

function InternetCombineUrlW(
  lpszBaseUrl: PWideChar;   // LPCWSTR
  lpszRelativeUrl: PWideChar;   // LPCWSTR
  lpszBuffer: PWideChar;   // LPWSTR out
  lpdwBufferLength: Pointer;   // DWORD* in/out
  dwFlags: DWORD   // DWORD
): BOOL; stdcall;
  external 'WININET.dll' name 'InternetCombineUrlW';

result := DllCall("WININET\InternetCombineUrlW"
    , "WStr", lpszBaseUrl   ; LPCWSTR
    , "WStr", lpszRelativeUrl   ; LPCWSTR
    , "Ptr", lpszBuffer   ; LPWSTR out
    , "Ptr", lpdwBufferLength   ; DWORD* in/out
    , "UInt", dwFlags   ; DWORD
    , "Int")   ; return: BOOL

●InternetCombineUrlW(lpszBaseUrl, lpszRelativeUrl, lpszBuffer, lpdwBufferLength, dwFlags) = DLL("WININET.dll", "bool InternetCombineUrlW(char*, char*, char*, void*, dword)")
# 呼び出し: InternetCombineUrlW(lpszBaseUrl, lpszRelativeUrl, lpszBuffer, lpdwBufferLength, dwFlags)
# lpszBaseUrl : LPCWSTR -> "char*"
# lpszRelativeUrl : LPCWSTR -> "char*"
# lpszBuffer : LPWSTR out -> "char*"
# lpdwBufferLength : DWORD* in/out -> "void*"
# dwFlags : 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。