SHDefExtractIconW

// SHELL32.dll  (Unicode / -W)
#include <windows.h>

HRESULT SHDefExtractIconW(
    LPCWSTR pszIconFile,
    INT iIndex,
    DWORD uFlags,
    HICON* phiconLarge,   // optional
    HICON* phiconSmall,   // optional
    DWORD nIconSize
);

<DllImport("SHELL32.dll", CharSet:=CharSet.Unicode, ExactSpelling:=True)>
Public Shared Function SHDefExtractIconW(
    <MarshalAs(UnmanagedType.LPWStr)> pszIconFile As String,   ' LPCWSTR
    iIndex As Integer,   ' INT
    uFlags As UInteger,   ' DWORD
    phiconLarge As IntPtr,   ' HICON* optional, out
    phiconSmall As IntPtr,   ' HICON* optional, out
    nIconSize As UInteger   ' DWORD
) As Integer
End Function

' pszIconFile : LPCWSTR
' iIndex : INT
' uFlags : DWORD
' phiconLarge : HICON* optional, out
' phiconSmall : HICON* optional, out
' nIconSize : DWORD
Declare PtrSafe Function SHDefExtractIconW Lib "shell32" ( _
    ByVal pszIconFile As LongPtr, _
    ByVal iIndex As Long, _
    ByVal uFlags As Long, _
    ByVal phiconLarge As LongPtr, _
    ByVal phiconSmall As LongPtr, _
    ByVal nIconSize 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

SHDefExtractIconW = ctypes.windll.shell32.SHDefExtractIconW
SHDefExtractIconW.restype = ctypes.c_int
SHDefExtractIconW.argtypes = [
    wintypes.LPCWSTR,  # pszIconFile : LPCWSTR
    ctypes.c_int,  # iIndex : INT
    wintypes.DWORD,  # uFlags : DWORD
    ctypes.c_void_p,  # phiconLarge : HICON* optional, out
    ctypes.c_void_p,  # phiconSmall : HICON* optional, out
    wintypes.DWORD,  # nIconSize : DWORD
]

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('SHELL32.dll')
SHDefExtractIconW = Fiddle::Function.new(
  lib['SHDefExtractIconW'],
  [
    Fiddle::TYPE_VOIDP,  # pszIconFile : LPCWSTR
    Fiddle::TYPE_INT,  # iIndex : INT
    -Fiddle::TYPE_INT,  # uFlags : DWORD
    Fiddle::TYPE_VOIDP,  # phiconLarge : HICON* optional, out
    Fiddle::TYPE_VOIDP,  # phiconSmall : HICON* optional, out
    -Fiddle::TYPE_INT,  # nIconSize : DWORD
  ],
  Fiddle::TYPE_INT)
# Wide strings: pass str.encode("UTF-16LE") + "\x00\x00"

#[link(name = "shell32")]
extern "system" {
    fn SHDefExtractIconW(
        pszIconFile: *const u16,  // LPCWSTR
        iIndex: i32,  // INT
        uFlags: u32,  // DWORD
        phiconLarge: *mut *mut core::ffi::c_void,  // HICON* optional, out
        phiconSmall: *mut *mut core::ffi::c_void,  // HICON* optional, out
        nIconSize: u32  // DWORD
    ) -> i32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("SHELL32.dll", CharSet = CharSet.Unicode)]
public static extern int SHDefExtractIconW([MarshalAs(UnmanagedType.LPWStr)] string pszIconFile, int iIndex, uint uFlags, IntPtr phiconLarge, IntPtr phiconSmall, uint nIconSize);
"@
$api = Add-Type -MemberDefinition $sig -Name 'SHELL32_SHDefExtractIconW' -Namespace Win32 -PassThru
# $api::SHDefExtractIconW(pszIconFile, iIndex, uFlags, phiconLarge, phiconSmall, nIconSize)

#uselib "SHELL32.dll"
#func global SHDefExtractIconW "SHDefExtractIconW" wptr, wptr, wptr, wptr, wptr, wptr
; SHDefExtractIconW pszIconFile, iIndex, uFlags, phiconLarge, phiconSmall, nIconSize   ; 戻り値は stat
; pszIconFile : LPCWSTR -> "wptr"
; iIndex : INT -> "wptr"
; uFlags : DWORD -> "wptr"
; phiconLarge : HICON* optional, out -> "wptr"
; phiconSmall : HICON* optional, out -> "wptr"
; nIconSize : 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 "SHELL32.dll"
#cfunc global SHDefExtractIconW "SHDefExtractIconW" wstr, int, int, sptr, sptr, int
; res = SHDefExtractIconW(pszIconFile, iIndex, uFlags, phiconLarge, phiconSmall, nIconSize)
; pszIconFile : LPCWSTR -> "wstr"
; iIndex : INT -> "int"
; uFlags : DWORD -> "int"
; phiconLarge : HICON* optional, out -> "sptr"
; phiconSmall : HICON* optional, out -> "sptr"
; nIconSize : DWORD -> "int"

; HRESULT SHDefExtractIconW(LPCWSTR pszIconFile, INT iIndex, DWORD uFlags, HICON* phiconLarge, HICON* phiconSmall, DWORD nIconSize)
#uselib "SHELL32.dll"
#cfunc global SHDefExtractIconW "SHDefExtractIconW" wstr, int, int, intptr, intptr, int
; res = SHDefExtractIconW(pszIconFile, iIndex, uFlags, phiconLarge, phiconSmall, nIconSize)
; pszIconFile : LPCWSTR -> "wstr"
; iIndex : INT -> "int"
; uFlags : DWORD -> "int"
; phiconLarge : HICON* optional, out -> "intptr"
; phiconSmall : HICON* optional, out -> "intptr"
; nIconSize : DWORD -> "int"

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

var (
	shell32 = windows.NewLazySystemDLL("SHELL32.dll")
	procSHDefExtractIconW = shell32.NewProc("SHDefExtractIconW")
)

// pszIconFile (LPCWSTR), iIndex (INT), uFlags (DWORD), phiconLarge (HICON* optional, out), phiconSmall (HICON* optional, out), nIconSize (DWORD)
r1, _, err := procSHDefExtractIconW.Call(
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(pszIconFile))),
	uintptr(iIndex),
	uintptr(uFlags),
	uintptr(phiconLarge),
	uintptr(phiconSmall),
	uintptr(nIconSize),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // HRESULT

function SHDefExtractIconW(
  pszIconFile: PWideChar;   // LPCWSTR
  iIndex: Integer;   // INT
  uFlags: DWORD;   // DWORD
  phiconLarge: Pointer;   // HICON* optional, out
  phiconSmall: Pointer;   // HICON* optional, out
  nIconSize: DWORD   // DWORD
): Integer; stdcall;
  external 'SHELL32.dll' name 'SHDefExtractIconW';

result := DllCall("SHELL32\SHDefExtractIconW"
    , "WStr", pszIconFile   ; LPCWSTR
    , "Int", iIndex   ; INT
    , "UInt", uFlags   ; DWORD
    , "Ptr", phiconLarge   ; HICON* optional, out
    , "Ptr", phiconSmall   ; HICON* optional, out
    , "UInt", nIconSize   ; DWORD
    , "Int")   ; return: HRESULT

●SHDefExtractIconW(pszIconFile, iIndex, uFlags, phiconLarge, phiconSmall, nIconSize) = DLL("SHELL32.dll", "int SHDefExtractIconW(char*, int, dword, void*, void*, dword)")
# 呼び出し: SHDefExtractIconW(pszIconFile, iIndex, uFlags, phiconLarge, phiconSmall, nIconSize)
# pszIconFile : LPCWSTR -> "char*"
# iIndex : INT -> "int"
# uFlags : DWORD -> "dword"
# phiconLarge : HICON* optional, out -> "void*"
# phiconSmall : HICON* optional, out -> "void*"
# nIconSize : 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。